Manual Atto AFMI MFM KPFM P5788

Version:

1.0

Modified:

February 2015

Products:

Atomic Force Microscope attoAFM I

User Manuals

Atomic Force Microscope

attoAFM I/MFM/KPFM

P5788

attocube systems AG, Königinstrasse 11 A, D - 80539 München Germany

Phone: +49 89-24208888 Fax: +49 89-24208890

E-Mail: info@attocube.com www.attocube.com

For technical queries, contact:

support@attocube.com

attocube systems office Munich:

Phone +49 89 2877 80915

Fax +49 89 2877 80919

Disclaimer of Responsibility

attocube systems does not assume any responsibility for the use of

any circuitry described in this manual. attocube systems reserves

the right to change the product specifications and the

functionality, or the manual itself, at any time without prior

notice. Furthermore, attocube systems assumes no responsibility

or liability for any misinformation, errors, or general inaccuracies

that may appear in this manual.

Product and company names listed are trademarks or trade names of

their respective companies. Any rights not expressly granted herein

are reserved.

Page 3

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Table of Contents

I. Introduction .............................................................................................. 4

I.1. System Overview ..................................................................................... 5

I.1. Safety Information .................................................................................. 6

I.1.a. Warnings ............................................................................................ 7

II. Mode of Operation and Force Detection Scheme ................................................. 9

III. Components of the Microscope and Technical Specifications ................................ 12

III.1. Microscope Setup ................................................................................... 12

III.2. Electronics ............................................................................................ 14

III.2.a. ANC300: High voltage amplifier ............................................................. 14

III.2.b. ACC100: LDM1300 Laser Detector module and Break-Out Panels .................... 14

III.2.c. ANC350 Piezo controller for positioners ................................................... 15

III.2.d. Laser detector module: LDM1300 ........................................................... 16

III.2.e. ASC500 SPM Controller ........................................................................ 16

III.3. (Dis-)Assembling the attoAFM I Module ....................................................... 17

III.3.a. Inserting (removing) the stack into (from) the microscope housing ............... 17

III.3.b. Mounting the Scanner-Positioner Stack ................................................... 19

III.4. Sample Exchange and Thermal Contact ........................................................ 19

III.5. Changing the AFM Cantilever ..................................................................... 20

III.5.a. The cantilever mounting platform .......................................................... 23

III.5.b. Cantilever exchange ............................................................................ 23

III.5.c. Mounting the attoAFM I sensor head into the housing ................................ 26

IV. Connecting the attoAFM I Module .................................................................. 27

IV.1. Electrical Connections ............................................................................. 27

IV.1.a. ASC500 Controller Connections .............................................................. 27

IV.1.b. Break-Out Panel Connections ................................................................ 28

IV.1.c. Pin Connections ................................................................................. 29

IV.1.d. Vacuum Feedthroughs ......................................................................... 31

IV.2. Fiber Connection .................................................................................... 31

V. Measurement Procedure .............................................................................. 32

V.1. Operation Modes .................................................................................... 32

V.1.a. Contact Mode without Feedback (constant height) ..................................... 32

V.1.b. Contact Mode with Feedback on (constant force) ....................................... 33

V.1.c. Non-Contact Mode .............................................................................. 33

V.1.d. MFM and EFM measurements ................................................................. 35

V.1.e. KPFM measurements............................................................................ 35

V.2. Performing a Scan .................................................................................. 36

V.2.a. Set the Actor Scaling ........................................................................... 36

V.2.b. Non-Contact Mode .............................................................................. 37

V.2.c. Contact Mode ..................................................................................... 43

V.2.d. Starting a scan ................................................................................... 48

Page 4

I. Introduction

The attoAFM I is designed particularly for the use at extreme

environmental conditions such as ultra-low temperature, high magnetic

fields and high vacuum. Reliable functionality at these extreme conditions

is provided by implementing the outstanding attocube systems

nanopositioning modules as well as a force detection scheme based on an

all fiber low-coherence interferometer (explained in detail in the next

section).

To perform low temperature microscopy, the attoAFM I is cooled by a

controlled exchange gas atmosphere in a liquid Helium bath cryostat or a

variable temperature insert or a closed cycle cooling system.

The instruments may be surrounded by both liquid helium and liquid

nitrogen radiation shields, separated by vacuum insulation.

Figure 1

: The attoAFM I standard setup

Page 5

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

I.1. System Overview

The attoAFM I microscope is a tool to image, characterize, analyze, and

manipulate materials surfaces on a nanometer scale in low temperatures

as well as high magnetic fields. This short chapter wants to give a rough

overview on the concepts of the system.

The attoAFM I consists of the measurement head which is inside a housing

suspended on the lower end of the microscope stick, which itself is placed

in a vacuum tube. Before cooling down the system, this vacuum tube is

evacuated and backfilled with some He exchange gas for coupling to the

temperature outside of the vacuum tube. Typically, this vacuum tube is

then cooled by insertion into a He bath cryostat, a Variable Temperature

Insert (VTI), a pulse tube cooler, or by other means.

The main part of the attoAFM I measurement head is the AFM cantilever, a

thin bar typically made from silicon and possibly functionalized with

different coatings, which is placed before the end of an optical fiber,

hence forming an optical cavity, the length of which can be measured by

a laser/detector system.

The sample to be examined is placed (in standard setups) on an

ANPxyz101 positioner stack for coarse motion (5 x 5 x 5 mm³) and an

ANSxyz100 scanner (typ. 30 x 30 x 15 µm³ at 4 K, for details see the

specifications page at the end of the manual). Just underneath there is

typically also a temperature sensor and a small heater, which allows

controlling the temperature of the sample precisely.

When the sample is brought into contact with the cantilever, the

interaction forces can be measured by recording the length of the cavity.

While the sample is scanned, typically the distance between -tip and

sample is kept constant by the use of a feedback loop. For these purposes,

one uses the electronic scan controller ASC500, which generates all

required voltages and records all relevant signals. Additionally, a high

voltage amplifier ANC300 is part of the system, amplifying the unipolar,

0 – 10 V signals to 0 – 150 V, as well as generating the signals required to

move the stepper positioners.

Regarding the optics, laser light is guided to the fiber-cantilever cavity,

and the back-reflection is then detected by a photo-receiver. The signal

generated by the photo-receiver is analyzed and recorded with the

ASC500 controller.

Page 6

I.1. Safety Information

For the continuing safety of the operators of this equipment and the

protection of the equipment itself, the operator should take note of the

Warnings, Cautions, and Notes throughout this handbook and, where

visible, on the product itself.

The following safety symbols may be used on the equipment:

Laser safety warning. Class 1M laser product.

Warning. Risk of electric shock. High voltages present.

Warning. Risk of danger. Refer to the handbook for details on this hazard.

Functional (EMC) earth/ground terminal.

The following safety symbols may be used throughout the handbook:

Warning. An instruction, which draws attention to the risk of injury or

death.

Caution. An instruction, which draws attention to the risks of damage to

the product, process, or surroundings.

Note. Clarification of an instruction or additional information.

Page 7

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

I.1.a. Warnings

Note: Please read the manual for the positioners, scanners, and the

controllers prior to initial operation! Mind the warnings mentioned in

there!

Warning. To prevent electrical shocks do not remove the cover of the

control unit. Unplug the power cord and all other electrical connections

and consult qualified service personnel before servicing or cleaning.

Operate only under dry conditions and at room temperature.

Warning. If this equipment is used in a manner not specified by the

manufacturer, the protection provided by the equipment may be impaired.

Do not operate the instrument outside its rated supply voltages or

environmental range. In particular, excessive moisture may impair safety.

Warning. Any individual vacuum space must be equipped with a security

overpressure valve! In case of hidden leaks air may enter into vacuum

spaces and build up large amounts of condensate at cold walls and

interfaces. In case such system is warmed up again such ice may evaporate

quickly and easily build up extremely dangerous overpressures! If no

overpressure valve is mounted on such vacuum space or the valve is

blocked e.g. due to mounting to a recovery line, this overpressure may

cause sudden breakdowns of the container, i.e. explosions. If in doubt,

please contact attocube systems.

Laser Safety Warning. Class 1M Laser product. This device utilizes a laser

which emits invisible light. There is potential for eye damage if proper

caution is not taken. The laser assembly should not be modified in any

way. The fiber cable should never be disconnected from the laser device

for any reason. The laser's wavelength is specified at 1330 nm with a

maximum power output of 1.5 mW. Please wear protective eyewear when

the laser source is turned on and never look directly into to the laser port

or fiber.

Warning. Plugging or unplugging modules of the electronic while

connected to power line will cause damages to the electronic. For

replacing modules disconnect the electronics from power and wait at least

5 minutes. Internal components need to be discharged.

Page 8

Caution. Never connect any cabling to the electronics when contacts are

exposed! Never connect any cabling to the electronics when the

electronics is not in GND mode! The scan piezos at the heart of a positioner

unit are high voltage components and can cause serious injuries. Be

careful not to cause a short-cut between the contacts in the BNC or any

other connectors.

Caution. For laboratory use only. This unit is intended for operation from a

normal, single phase supply, in the temperature range 5° to 40°C, 20% to

80% RH. The unit must be connected only to an earthed fused supply of

100, 115 or 230 V, 50/60 Hz.

Caution. In case of failure refer to your local dealer or attocube systems.

Users are cautioned not to attempt to access, open, modify, or service any

part of the setup unless outlined herein or otherwise directed by the

technical support staff from attocube systems. Take special care if

connecting products from other manufacturers. Clean only with a dry

cloth.

Caution. Because of the inherent fragility of the positioners and scanners

and the extreme conditions they are operated in, no responsibility can be

taken by the manufacturer for breakdowns of the ceramic piezo stacks. In

case of breakage, please contact the manufacturer for details of the repair

service.

Page 9

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

II. Mode of Operation and Force Detection Scheme

The attoAFM I is an atomic force microscope built around an optical

fiber based interferometer. The sensor is compatible with any

commercial cantilever and measures the vertical deflection of the

cantilever with picometer resolution. The microscope is designed to

work both in contact and in non-contact mode.

This highly compact microscope guarantees highest resolution tip-

sample positioning and an optimized sensor adjustment suitable for

any environment: room or low temperature, high magnetic field or

high vacuum conditions.

Figure 2

: Schematic drawing of the attoAFM I system.

Page 10

The force detection scheme for the attoAFM I microscope system is

based on an all fiber low-coherence interferometer (seeFigure 3).

Via a 50/50 fiber coupler, a laser beam illuminates a cavity built up

from the end-face of the fiber and the back-face of the cantilever. The

light reflected back from these surfaces gives rise to interferences that

can be seen by a detector. Due to the low reflectivity constants these

surfaces form a low-finesse Fabry-Perot cavity.

Monitoring the intensity of the interference fringes allows measuring

the tip deflection. The low coherence of the laser source has the

advantage of eliminating spurious interference signals resulting from

other reflections in the setup (e.g. the coupler), thus leading to an

increase of the signal-to-noise ratio of about 30 dB.

Figure 3

: Schematic drawing of the AFM I setup.

The periodicity of the signal corresponds to half the wavelength -of the

laser source. Hence, the system can be easily calibrated and a measured

voltage difference can be translated into a height difference.

The control fiber has to be adjusted with respect to the cantilever in such a

way that the interference signal is at the quadrature point, i.e. in the

middle between two extrema values. In this case, the sensitivity of the

sensor is highest.

There are different ways to perform topographic images. Common modes

are the so-called contact- and non-contact modes.

Page 11

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Figure 4

: Schematic drawing of the interference signal.

Contact mode:

The tip is in direct contact with the sample, while the intensity is in the

middle of the intensity range. The cantilever is not oscillating. Due to a de-

tuning of the cantilever position before contacting the surface, a

compressive force is applied onto the sample. The strength of the force

corresponds to the amount of detuning times the force constant of the

cantilever.

For example, the cantilever position can be adjusted off contact such that

the intensity is in a minimum. Now, by engaging the feedback loop, the

sample is lifted up until the tip engages with the sample surface. While still

increasing the sample height, the smaple pushes the cantilever up until

the intensity reaches the middle intensity value. The amount of bending

corresponds in this case to a cavity length difference of -/8, and hence the

force on the tip is F =

-

/8*k, with k being the force constant of the

cantilever. As the feed-back loop keeps the intensity constant, the amount

of bending is kept. Hence, the force on the tip is kept constant.

Non-contact mode:

For non-contact mode, no detuning is applied; the cavity length is such

that the signal is in the middle between the extrema. Then, the cantilever

is excited by the dither piezo at its resonance frequency. The input of the

lock-in measures the AC component of the photo-detected signal, which

reflects the oscillation amplitude of the cantilever. As the cantilever

approaches the sample, the oscillation amplitude drops rapidly with

decreasing tip-sample distance. This signal serves as the input to a feed-

back loop which maintains the cantilever oscillation amplitude at a so

called ‘set level’, which corresponds to a given force between the sample

and the cantilever. During the scan, the output signal of the feedback loop

is recorded (z-scanner piezo voltage), providing a topographic image.





d

Page 12

III. Components of the Microscope and Technical Specifications

III.1. Microscope Setup

The sample is mounted onto a stack consisting of an ANPxyz101 coarse

positioning unit, an ANSxyz100 scanner and a copper sample plate that

carries heater and temperature sensor. The attoAFM I module, consisting

of the cantilever holder and the attoAFM I head together with the fiber

based deflection detection system, is fixed onto a slide which is mounted

in the microscope housing.

The microscope module is mounted below the 3He pot . The top of the 3He

insert contains all electrical connectors and feedthroughs, the vacuum

window, and the fiber feedthrough. The AFM module including the fiber-

and sample positioning units is attached to the bottom of the insert, see

Figure 5. The microscope housing is inserted into a inner vacuum chamber

(IVC) and subsequently sled into the cryostat utilizing a log G10 tube .

Figure 5:

Image of the attoAFM I housing

The positioning stage ANPxyz101 is built from three individual positioners

mounted on top of each other (please find the specifications in the

respective manual). The ANSxyz100 scanners will be mounted on top of the

positioner stack, followed by a plate with integrated heater and

Page 13

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

temperature sensor. Finally, the quik exchange sample holder is mounted

to the very top of the assembly.

The stack will be delivered completely mounted. If you ever need to

disassemble and consequently reassemble it, please recheck the correct

orientation (which is given in the system specs) and the correct order of

the different parts and screws. Wrong screws may cause severe damages to

the scanners and positioners.

Figure 6:

Standard assembly of the stack with a lower coarse-positioning unit and an upper scanner unit. The

sample holder is specially designed for the 3He system.

Page 14

III.2. Electronics

III.2.a. ANC300: High voltage amplifier

The ANC300 can be used either as ‘piezo positioning controller’ or as ‘high

voltage amplifier’.

Four axes of the ANC300 controller provide the high voltages for driving

the attocube scanners for fine positioning (voltage amplifier with an

amplification factor 15).The fourth axis is another high-voltage amplifier

that drives the dither piezo of the attoAFM I.

For technical specifications please refer to the respective manual.

The axis number is counted from the right to the left.

For technical specifications please refer to the respective manual.

Figure 7

: ANC300 used as high voltage amplifier on the axes 1-4, and as a AC-DC coupler for the tip voltage.

III.2.b. ACC100: LDM1300 Laser Detector module and Break-Out Panels

The ACC100 is a 19”housing that allows to attach electrical break-out

panels as well as additional electronic modules, e.g. the LDM1300 laser

detector module.

The electrical break-out panels convert the 12- and 8-pin Fischer

connectors to easy accessible BNC connectors.

Page 15

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Figure 8

: The ACC100 with the Break-Out-Panels and the LDM1300.

Four break-out panels serve as connector panels between the controllers

with BNC outputs and the microscope with multi-pin Fischer cables.

For details about the labelling and electrical connections see section IV.1.

III.2.c. ANC350 Piezo controller for positioners

Piezo controller driving /RES encoded attocube positioners in coarse and

fine positioning mode. Please note that for the He-3-system highly

resistive wires are taken for the resistive encoding. This is why you need to

upload a modified RESencoder-file with the extension ‘_mod’. The original

files may be taken without highly resistive wires.

For technical specifications please refer to the respective manual.

Figure 9

: The ANC350 piezo controller.

Page 16

III.2.d. Laser detector module: LDM1300

The attoAFM I system includes a temperature-stabilised laser-detector

module, the LDM1300.

The wavelength of the laser diode is 1310 nm. The built-in photodetector

may be read out via the ‘DET OUT’ BNC connector.

For technical specifications please refer to the respective manual.

Figure 9

: LDM1300.

III.2.e. ASC500 SPM Controller

The modular and flexible digital SPM controller ASC500 combines state of

the art hardware with innovative software concepts to offer an unmatched

diversity of scanning-probe microscopy applications to the customer. All

desirable functions and high-end specifications for controlling the

experiment of your choice in AFM, CFM, SNOM, and STM are available. The

flexible, FPGA-based architecture allows the implementation of your

particular requirements to the system.

Figure 10

: The ASC500 SPM controller

Page 17

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

III.3. (Dis-)Assembling the attoAFM I Module

This section will describe how to assemble and align the AFM module.

Figure 11:

The assembled attoAFM I module.

III.3.a. Inserting (removing) the stack into (from) the microscope housing

The microscope stack is fixed to the housing bottom. By loosening

the two screws in the front and opening the three screws on the

left, right and back side the whole bottom part including the

positioner stack may be pushed down and electrically disconnected

from the stick.

The stack and bottom plate may then be taken off towards the front

of the housing.

Open

bottom

screws

Loosen front

screws

Page 18

As there might be some force needed to disconnect the bottom

plate, we recommend keeping the housing with one hand and using

the thumb of the other hand to push the front plate down.

Noteworthy, two slits on the sides of the bottom plate may be used

to smoothly lever off the plate using a screw driver.

Before mounting the stack back into the housing, inspect the

cabling before pushing the bottom plate upwards. Make sure not to

squeeze any wire!

‘Bottom part’, including the housing bottom plate and positioner

stack.

You must not disassemble the stack. If there is any problem with

the stack please contact attocube AG for support.

Page 19

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

III.3.b. Mounting the Scanner-Positioner Stack

Carefully place the stack onto the spacer plate on the bottom plate. Make

sure that the stack cannot fall down. Move the stack backwards until the

outer shape matches with the spacer plates.

Introduce two screws (M2.5 x 8) in the bottom plate in order to fix the

stack, see picture. Once the screws are tightened a little by hand, you can

use a screwdriver to tighten them further.

III.4. Sample Exchange and Thermal Contact

In order to change samples you need to take of the stack, as described

above.

A copper plate is fixed on top of the stack, electrically isolated but

thermally coupled, to the copper body that is directly connected/coupled

to the 3He-pot with copper braids.

For cleaning the sample holder acetone as well as alcohol may be used

(please take care that no conductive paste gets between the sample

plate and the lower copper body).

The sample holder may be electrically connected with a single pin

connector to set the sample potential. In the present setup the pin ‘S’ is

supposed to be connected to the sample holder (with a manganin wire) .

In order to fix the sample Apiezon N (available in the tool box) and/or

silver paste (available in the tool box) should be used.

The temperature sensor may be fixed with a headless set screw. Note that

this screw should only be fixed gently, in order to protect the sensor.

Attocube also recommends to cover the smaller top plate of the sensor

with Kapton tape (that can be found in the tool box).

For additional electrical connections, the pins X2…X6 on the housing

bottom may be accessed on the break-out panel ‘4’ of the electronic rack,

delivered with the microscope.

After the sample has been changed, the housing can be assembled again

and at last the copper rods need to be attached to the upper copper body

as shown in the picture to the left with two screws. These screws should

be tighly closed in order to give as good thermal conduction as possible.

Attocube also recommends to polish the inner surfaces of this contact

from time to time and to add a little bit of Apiezon grease (that can be

found in the tool box) before closing it.

Page 20

III.5. Changing the AFM Cantilever

Page 21

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

The attoAFM I (+) head includes an alignment-free

cantilever holder that is compatible with all

commercially available XY-auto alignment AFM tips.

In order to change the tip the attoAFM I (+) head

needs to be handled as follows::

1. Turn the AFM head upwards. Insert an Allen key

in the provided hole as shown in the picture to the

left (a)

2. Grab the cantilever holder on its arms and

smoothly strip it off, see picture to the left. (b)

Page 22

3. Perform the AFM tip exchange (for details, see

description below)

4. Once a new tip is mounted, reattach the

cantilever holder:

A guiding rod (c) automatically centers the

cantilever holder, while the fiber ferrule is still far

away from any potentially harmful obstacle.

5. Feed the ferrule into the cantilever holder

through another guiding sleeve (d). The ferrule

is protected by an additional soft Teflon cap.

6. Tilt the head back into the housing – it flips

conveniently and firmly into its dedicated parking

position.

No further mechanical alignment is necessary.

Page 23

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

III.5.a. The cantilever mounting platform

The mounting platform provides three stages for

the alignment and adjustment procedures of the

cantilever on the AFMI head, namely:

I – cantilever exchange stage

II – AFM head parking site

III – slider module parking site

III.5.b. Cantilever exchange

In order to change the cantilever you need to:

Put the cantilever holder into the cantilever

exchange stage (1).

Slide back the spring blade, first push the back

part down (spring opens) (2) then pull the

slider towards the back(3).

In order to fix the AFM head into cantilever

exchange stage, you need to turn the black

knurled wheel sitting left to it.

II

I

III

Fix

Page 24

Perform cantilever exchange 4.-5.;

Do only use the plastic tweezers for handling

the cantilevers near the alignment chip.

Metallic parts may easily destroy this silicon

chip.

If the cantilever is not sitting correctly within

the chip you may gently push it with the end of

the plastic tweezers until it gets into the right

place.

Page 25

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Close the holder. 6.-7.

Remove holder from the exchange

basis, and insert it back, see above,

into the AFM head.

Finally, run a spectroscopy on the dither piezo

(interference signal ADC1 vs. DAC1 dither voltage)

in order to see whether you get a decent

interferogram (in this context, “decent” is defined

by the intensity of the interferometric signal and

its symmetric shape)..

If the interferogram becomes comparable to the

one depicted in Figure 12 with a contrast of ≈ 1 V a

good measuring condition is met.

Figure 12

: Interference fringes seen in the cavity signal

on changing its length (spectroscopy ADC1 vs. DAC1).

Typically, the cavity gap amounts to 10-50 µm. Be

aware that the cavity will decrease when cooling

the microscope to liquid Helium temperature (up to

10 µm depending on the lever in use).

Note that the silicon cantilever-alignment chip

needs to be kept very clean. Hence, from time to

time it needs to be gently brushed with a alcohol-

soaked Q-tip.

Page 26

III.5.c. Mounting the attoAFM I sensor head into the housing

Before mounting the attoAFM I head into the housing make sure that

the z-positioning stage is fully retracted and that the cantilever

cannot touch the sample, i.e. sits clearly above the later.

Now slide the aligned attoAFM I head into the microscope housing

and tighten the two screws on top of the housing (see arrow).

This will fix the slider with the microscope head in place that also

makes an electrical contact to the microscope stick (e.g. the dither

piezo connection).

o

Page 27

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

IV. Connecting the attoAFM I Module

IV.1. Electrical Connections

IV.1.a. ASC500 Controller Connections

Table 1 gives an overview of all the electrical connections of the ASC500

controller.

Controller

Port

Controller

Port

Usage

ASC500

X-Out

ANC300 (SCAN)

DC in x (1)

X scanner

Y-Out

ANC300 (SCAN)

DC in y (2)

Y scanner

Z-Out

ANC300 (SCAN)

DC in z (3)

Z scanner

DAC1

ANC300 (SCAN)

DC in D (4)

dither offset (DC)

DAC2

AC/DC coupler

for KPFM

DCin

tip voltage

DAC3

Sample S1

S

sample voltage

ADC1

photo detector

DET out(T-piece)

interferometer signal (DC)

HF1 in

photo detector

DET out (T-piece)

interferometer signal (AC), AFM

HF1 OUT

ANC300 (SCAN)

Mod in D (4)

dither excitation

HF2 in

photo detector

DET out (T-piece)

interferometer signal (AC), KPFM

HF2 OUT

AC/DC coupler

for KPFM)

ACin

KPFM excitation

Ground

(rear side)

break-out panel

╧

grounding of the stack

USB port

PC

USB

PC - ASC500 communication

NSL port

ANC350 (Step)

NSL

ANC350 (STEP) communication

Table 1

: Overview of controller connections.

Page 28

IV.1.b. Break-Out Panel Connections

The break-out panels are connected to the different controllers via BNC

cables. These cables are labelled for your convenience. See Table 2 for a

complete list.

Figure 13

: Break-Out Panels.

Label break-out

panel

Controller connection

Usage

Px

ANC350 Axis 1 (OUTPUT)

X Positioner: Px

Py

ANC350 Axis 2 (OUTPUT)

Y Positioner: Py

Pz

ANC350 Axis 3 (OUTPUT)

Z Positioner: Pz

Sx

ANC300 Axis 1 (OUTPUT)

X Scanner: Sx

Sy

ANC300 Axis 2 (OUTPUT)

Y Scanner: Sy

Sz

ANC300 Axis 3 (OUTPUT)

Z Scanner: Sz

T-I

temperature monitor Ch A

temperature sensor current

T-V

temperature sensor voltage

H

temperature monitor (optional)

╧

ASC500 ground (rear side)

grounding of the stack

X1

---

optional user contact (above

housing)

X2

---

optional user contact

X3

---

optional user contact

X4

---

optional sample contact

X5

---

optional sample contact

X6

---

optional sample contact

D

ANC300 Axis 4 (OUTPUT)

Dither DC voltage/ AC

excitation

╧

ASC500 Ground (rear side)

grounding of the stack

Page 29

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Table 2

: Overview of Break-Out panel connections.

IV.1.c. Pin Connections

All electrical pin connections to and from the attoAFM I module are low

temperature compatible pin. Most electrical connections are twisted pairs

of copper wires adjusted to the correct lengths. Wires carrying positive

voltages are labelled red, GND wires are marked black. All wiring from the

positioner stack has to be connected to the front- and back-row pin

connectors in the bottom plate of the housing. All connectors are labelled

with short codes. The port numbers are counted from the left to the right

(1,2,3..., see pictures below).

Table 3 describes these codes and provides details about the connections.

Port

number

Usage

Connector code

Leads to Fischer/BNC

connector

1 front

X Positioner

Px

1

2 front

Y Positioner

Py

1

3 front

Z Positioner

Pz

1

4 front

X Scanner

RESx

1

5 front

Y Scanner

RESy

1

6 front

Z Scanner

RESz

1

7 front

--

-

8 front

X Scanner

Sx

2

9front

Y Scanner

Sy

2

10 front

Z Scanner

Sz

2

1 back

temperature sensor

T-I

3

2 back

temperature sensor

T-V

3

3 back

sample heater

H

3

4 back

sample

S

4

5 back

user contact

X2

4

6 back

user contact

X3

4

7 back

user contact

X4

4

8 back

user contact

X5

4

9 back

user contact

X6

4

10 back

User contact

BNC1

AFM head 1

Dither

D

2

AFM head 2

user contact

X1

2

Housing top

ground

╧

2

Table 3: Overview of pin connections.

Page 30

In order to get access to the front-row-pin connections the front side

needs to be taken off by opening one screw.

Front view of the present housing pin connections.

Back view of the present housing pin connections.

Page 31

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

IV.1.d. Vacuum Feedthroughs

There are multi-pin cables used to connect the microscope to the

electronics rack. The black cables are labelled ‘1’ ,‘2’,’3’,’4’.

IV.2. Fiber Connection

The optical read out system of the cantilever of the attoAFM I system requires

only one optical connection which will be described in this section.

For the optical connection plug the attoAFMI fiber into the laser port1 (or

port2) of the LDM1300. Please make sure to have the right orientation of the

fiber groove and tongue system (see Figure 14). Do not tighten too hard as

this might damage the optical connector.

Figure 14:

Connecting the FC/APC pigtail to a connector port. Be careful to obey the correct orientation of the

groove and the tongue.

Page 32

V. Measurement Procedure

This chapter will lead you through your first measurement in the different

AFM modes available.

V.1. Operation Modes

Different operation modes are possible. The two fundamental ones are the

Contact Mode - with and without feedback - and the Non-Contact Mode (also

intermittent or modulation mode).

V.1.a. Contact Mode without Feedback (constant height)

In contact mode, the tip is brought in contact with the sample. The sample

is scanned without any feedback control of the z scanner, i.e. topographic

variations are directly translated into a deflection of the cantilever. The

photo detector signal is acquired during scanning, which can be directly

converted into a height signal by using the formula:

V

dV

nm

V

dV

dz 





 246

2



-

Here, V is the peak-to-peak amplitude of the interferogram; dz is the

change in height corresponding to a change dV in detector voltage.

Important note: This mode is only suitable for samples with a maximum

height corrugation of -/4! Otherwise, the contrast may be inverted.

The contact mode without feedback, also called const.-height mode, is the

easiest and fastest way to record an AFM image, because it is not depending

on z feedback. Please note that the image topography is inverted if the

working point within the interference signal is set to a negative slope.

For contact mode scans, cantilevers with a small stiffness (< 5 N/m) are used

in order to keep the forces between tip and sample small.

Page 33

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Figure 15

: Schematic drawing of the attoAFM I operated in contact mode without feedback.

V.1.b. Contact Mode with Feedback on (constant force)

The tip is first brought into real contact with the sample surface. In this

mode, however, a feedback mechanism is employed to keep the deflection

signal at a constant value by varying the voltage of the z-scanner. This will

maintain a constant force between tip and sample. The feedback setpoint

should be set to the point of maximum slope in the interference signal

(working point), i.e. to the middle between two interference extrema. The

main measurement signal in this mode is the voltage applied to the z

scanner, which can be translated into height data by using the z piezo

calibration value (usually this is automatically done by the controller

software). The error signal is the detector signal.

This mode is suggested for samples with height corrugations >-/4!

Since a feedback always causes low pass filtering, the measurements in

constant force mode are usually slower but less noisy than constant height

images.

V.1.c. Non-Contact Mode

In this mode, the cantilever is excited at its resonance frequency by an AC

voltage applied to the dither piezo. Correspondingly, the photo-detected AC

signal at the resonance frequency reflects the oscillation amplitude of the

cantilever. As the cantilever approaches the sample, this vibration amplitude

decreases rapidly with diminishing tip-sample distance. Note that the

oscillation amplitude is already reduced due to long-range forces (such as

van der Waals- or electrostatic/magnetic forces), i.e. the tip is not

necessarily physically touching the sample.

At this point, a oscillation amplitude called ‘set level’ is defined,

corresponding to a given force between sample and cantilever. The vibration

amplitude of the cantilever serves as the input to a feedback loop which

maintains the cantilever oscillation at the set level by adjusting the voltage

on the z-scanner (amplitude feedback). Alternatively, the amplitude and the

Page 34

phase of the oscillation resonance can be kept constant (phase feedback).

During the scan, the output signal of the feedback loop is recorded (z-piezo

voltage), providing the topographic information. The error signal is the

oscillation amplitude of the cantilever.

For non-contact mode scans, cantilevers with a high stiffness (k > 2 N/m) are

used to avoid the problem of unwanted jump-to-contact (stop of the

oscillation).

Figure 16 illustrates the interference signal measured by an interferometric

deflection detection system in non-contact mode. The output signal is largest

if the cantilever vibrates around the point of maximum slope of the

interference signal (working point). The working point is set by applying an

offset DC voltage to the dither piezo.

The AC voltage detected (peak to peak) by the Lock-In amplifier can be

translated into the real oscillation amplitude,

V

dV

nm

V

dV

dz 





 246

2



-

Figure 16:

Schematic drawing of the interference signal.

Note that if the vibration amplitude of the cantilever is slightly higher than a

quarter of the wavelength, the optical signal gets distorted at its extrema.

This is shown in Figure 17, which illustrates the electrical signals

corresponding to the dither excitation (top) and the interference signal

(bottom). Sweeping the (DC) dither voltage and measuring the interference

signal provides a quick calibration of the vibration amplitude of the

cantilever.

Page 35

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Figure 17

: Electrical signals corresponding to the dither excitation (top) and interference signal (bottom).

V.1.d. MFM and EFM measurements

MFM (EFM) is performed in non-contact mode utilizing a magnetic

(conducting) tip, i.e. the tip of the cantilever is covered with hard-magnetic

or conductive material. The tip-sample interaction leads to a shift f of the

lever mechanical resonance frequency f0. This interaction is directly related

to the gradient F of the magnetic force acting on the tip along the lever

bending direction. For a given lever of spring constant K (>> F), the

relation between the force gradient and the frequency shift f (<< f0) is

given by the approximation

F  -2 (f/ f0) K.

Thus, the magnetic (electric) information can be either extracted from the

detected phase shift while measuring at a const. frequency or

correspondingly from the measured frequency shift in a phase-lock loop.

In order to avoid mixing of topographic and magnetic (electric)

information, the magnetic signal is usually recorded at bigger tip-sample

distances.

V.1.e. KPFM measurements

KPFM is performed in non-contact mode utilizing a conductive tip, i.e. the

tip of the cantilever is covered with a contactable conductive material. In

contrast to the MFM or EFM modes the cantilever is not mechanically excited

at its resonance frequency by using the dither piezo but by using an

oscillating electrical tip AC potential. The oscillation amplitude thereby

depends on the tip to sample DC voltage difference. Hence, by keeping the

oscillation amplitude at its minimum (i.e. HFx=0) with means of tuning the

Page 36

tip DC voltage a direct mapping of the sample potential is possible. The

KPFM mode is performed in a constant sample to tip distance using the dual

pass technique. In the first line the sample topography is recorded and in

the second line the topography is retraced at a certain tip-sample distance

while the KPFM signal is recorded.

V.2. Performing a Scan

The following sections describe the most important steps to be performed

before a scan is started. The AFM system must be in the following state

before you can go on:

- all electrical and optical connections are correct (see chapter IV).

- The tip-fiber system is well aligned.

- The step function for the positioner axes of the ANC300 axes should be

activated in the hardware but disabled in the coarse menu of the

software.

- For the non-contact mode, the BNC labeled HF out of the Lock-In

amplifier (on the ASC500) should be connected to the AC IN of the

AC/DC-coupler breakout panel and both the HF in input of the Lock-In

amplifier and ADC1 are connected in series to the output of the photo

detector.

With an open system at ambient conditions, start to manually approach the

sample to the tip using the z coarse positioner. This should be done under

eye inspection to a distance close enough for reasonable auto-approach

duration but still far enough away to avoid any crash of the tip. If the system

is going to be cooled down, the sample surface should be moved down 250-

500 steps from the contact position to (i) avoid the tip crashing into the

sample on cooling due to thermal contractions and (ii) assure a reasonable

approach time at low temperatures.

V.2.a. Set the Actor Scaling

The voltage outputs of the ASC500 must be activated (check the ‘output

active’-button within the DAISY software)

However, before you start activating the outputs, check that the correct

temperature and the according scaling details are set correctly in the ‘Actor

Scaling’ box of the ‘Pref’ window.

Two sets of parameters for room temperature and low temperature may be

saved. The parameters for the low temperature scaling entered here by

attocube systems are the calibrated 4 K values.

Note that at room temperature 4 V is the upper limit for the ASC500 scanner

outputs and at 4 K this limit increases to 10 V (this limits are valid for an

amplifier with amplification factor 15, namely the ANC300). If the customer

wants to measure at temperatures in between he should not exceed the

Page 37

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

linearly extrapolated voltages.

V.2.b. Non-Contact Mode

In non-contact mode the tip-fiber cavity has to be adjusted to the point of

highest interference sensitivity, i.e. at which the change in the tip-fiber

distance gives the biggest (linear) change in the interferometric signal.

After the cavity has been adjusted to this point, the cantilever must be

excited at its resonance frequency and the photo-detected AC voltage

AFM Aosc will be used as measuring signal for the feedback loop. The basic

steps for this procedure are sketched below.

1. Adjustment of the fiber-cantilever cavity:

Run a so-called ‘dither spectroscopy’ (spectroscopy of ADC1 vs.DAC1) to

check the interferogram. To do so, choose one of the 'Spec' windows and

enter the following settings:

DAC: DAC1

Start: 0V

End : max. 4V (@RT); max. 10V (@LT)

Data Points: >1000

Data Point Avg. Time: 2-5 ms

Delay per Data Point: 0-5 ms

Choose ADC1 as the signal to be monitored.

Start the spectroscopy.

The Spectroscopy View should look similar to the figure below. The working

point WP (point of highest sensitivity where signal depends linearly on the

Page 38

cavity length between fiber end and cantilever) is located at the midpoint

between minimum and maximum of the interference signal.

Adjust ADC1 to the WP by tuning the dither piezo voltage, i.e. DAC1, in the

‘DACs’ window.

2. Finding the resonance frequency fres of the cantilever:

In non-contact mode, the cantilever is excited at its resonance frequency fres

with the an AC voltage Aexc. To deduce fres , the excitation frequency is swept

while measuring the oscillation amplitude (and the phase) of the cantilever.

The excitation amplitude and all demodulation settings are made in the

‘Lock In’ widow. The frequency sweep is done in the ‘Calibration’ window.

High Frequency box:

Amplitude (pp): 10-200 mV (@RT); 1-20 mV (@LT)

This sets the excitation amplitude

Frequency: This frequency will be deduced from the

calibration

For ‘Demodulation’ parameters, choose:

Sensitivity Range: 1-2 V (maximum oscillation

amplitude Aosc)

Phase Shift: leave 0 or set an offset phase so that the

phase signal is 0 at resonance.

Integration time: set to 100 µs – 1 ms

Leave the Preferences value set to 1.

Calibration:

Frequency range (Start - End): 45 kHz – 95 kHz

(depending on the cantilever)

Data Points: 500-5000

Data Point. Avg. Time: 2.5ms

Page 39

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Delay Per Data Point: 0s

Start the calibration.

The upper figure shows the calibration window and the oscillation amplitude

(AFM Aosc) of the cantilever as a function of the excitation frequency. From

this resonance curve, fres can be selected with the help of the frequency

selection tool. Press the ok button (green checkmark) to set the chosen

frequency as the excitation frequency. It is also possible to zoom in by using

the frequency range selection tool.

It is possible to extract the oscillation amplitude A of the cantilever from the

resonance curve with help of the calibration of the interference signal:

A = -/2*V/V with V being the photo detector signal at resonance and

V being the peak-peak amplitude of the interference

signal.

The amplitude A is typically chosen to be within 20 nm to 100 nm.

Besides the the oscillation frequency of the resonance, the Full Width at Half

Maximum (FWHM) can also be deduced from the resonance curve which

allows calculating the cantilever’s Q factor, Q = fres/FWHM.

Page 40

3. Starting the Auto Approach:

The auto approach procedure will expand the z-scanner while constantly

checking the photo-detected Ac signal AFM_Aosc. If a certain threshold (stop

condition) is not detected within one stroke, the z piezo will be retracted and

a predefined number of coarse steps in z direction will be executed.

Afterwards, ramping of the z-scanner will be restarted. Please note that you

can affect the range of the z-piezo stroke by adjusting 'Z limit min' and 'Z

limit max' within the 'Feedback' tap.

Before starting the auto approach, select the AFM_Aosc as ‘Actual Value’ in

the 'Feedback' tab. Furthermore, choose the following parameters:

Z out: 0nm

Z limit min: 0nm

Z limit max: maximum z piezo stroke. See data sheet at

the end of this manual.

P: 1-5 m

I: 1-20 Hz

Inv. Polarity: checked (signal AFM Aosc is expected to decrease with

increasing Z)

In the 'Coarse' tab, one can find the 'Auto Approach' box where the

following parameters should be entered:

Delay: 10 ms

Threshold: ~2/3 * of AFM_Aosc

Stop Cond.: < Threshold

Speed: 2V/s (@RT), 3V/s (@LT)

Steps/Apr.: see data sheet (part of this manual)

Apr. Mode: Ramp

Target Mode: Retract

Page 41

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Check the ‘Autoapproach Details’ where the following parameters should be

entered:

Coarse Axis: Axis 3

Coarse Dir.: Forward

Coarse Device: ANC150

Coarse Trig. Pol.: High Active

Coarse Trig. Hold Time: 0 µs

The auto approach should last between a few minutes and half an hour,

depending on approach parameters and initial tip-sample distance. After the

auto approach is finished, the sample surface is within reach of the z

scanner.

The figure below shows how the auto-approach signal is typically reflected

in the photo-detected AC signal AFM Aosc (at an already quite small tip-

sample distance)

4. Finding a good setpoint:

During the measurement, the distance (force) between tip and sample will

be held constant by the P/I-feedback loop that tries to keep the oscillation

amplitude at a given setpoint by varying the voltage applied to the z

scanner. It will now be described how a reasonable setpoint for the feedback

loop can be found with help of a z-spectroscopy:

In order to perform a ‘z-spectroscopy’, choose on of the ‘spec’ windows and

enter with the following parameters/values:

Page 42

DAC: Z

monitored signal: AFM Aosc

Start: 0pm

End: maximum z piezo stroke. See data sheet at

the end of this manual

Data Points: 1000

Fwd/Bkwd: not checked

Data Point Avg. Time: 2-5ms

Delay Per Data Point: 0ms

Now open the 'Details Spectroscopy' sub menu and enter the following

parameters:

Limiter: (Stops the z spectroscopy before the tip crashes into the sample)

Active: checked

Source: AFM Aosc

Value: 0.5 * A

Limit: Source<Value

The contact point where the signal is dropping sharply should be in the

middle of the z scanner range. Move manually upwards with the z positioner

in a step by step fashion to adjust this position.

The set point for the AFM Aosc signal should be chosen in such a way as

shown in the picture (typically, the set point value corresponds to 75% -

95% of the free oscillation amplitude).

Page 43

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

V.2.c. Contact Mode

In Contact Mode the cantilever is not excited at its resonance frequency.

Only a DC voltage is applied to the dither piezo (normally on DAC1) and

correspondingly the DC voltage of the photo-detected signal (normally on

ADC1) is used to detect the topography.

Contrary to the non-contact mode the tip-fiber cavity is not set to the WP by

tuning DAC1 manually but by using ADC1 as the feedback input and defining

the working point WP as the setpoint.

1. Adjustment of the fiber-cantilever cavity length:

Execute a dither spectroscopy (photo-detector signal (normally on ADC1)

vs. DC dither voltage (normally on DAC1)) to check the interferometric

signal. To do so, choose the 'Spectroscopy' and the 'Spectroscopy View' tab

with the following settings:

Start: 0V

End : 4V (@RT); 10V (@LT)

Data Points: 1000

Data Point Avg. Time: 2ms

Delay per Data Point: 0ms

Start the spectroscopy.

The ‘Spectroscopy View’ should look similar to the Figure 18 below.

The working point WP (point of highest sensitivity where signal depends

linearly on the cavity length between fiber end and cantilever) is located at

the midpoint between minimum and maximum of the interference signal.

Page 44

Figure 18:

Working point WP.

The fiber-tip cavity now must be adjusted to a minimum (ADC1min ) of the

interferogram by tuning the DC voltage of the dither piezo (normally on

DAC1). Hence, as soon as the sample starts pushing against the tip the

cavity will decrease and the interferometric signal must increase.

2. Starting the auto approach:

The auto approach settings must be set accordingly, i.e. the voltage of the

limiter must be set slightly higher than the minimum of the interferometric

signal and the stop condition must be set to “ > threshold”. Remember that

the autoapproach monitors the parameter set kin the feedback window. This

parameter must be set to the DC signal of the photo-detector (ADC1).

Examples for correct autoapproach settings are given in the 3 figures below.

The auto approach will stop when the tip touches the sample. The cantilever

will be bent and the interference signal will sharply increase, see figure to

the left

Page 45

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Before starting the auto approach select the ADC1 as ‘Actual Value’ in the

'Feedback' box. Furthermore choose the following parameters :

Actual Value: SPM ADC1

Z out: 0nm

Z limit min: 0nm

Z limit max: maximum z scanner stroke (see data sheet at the end

of the manual).

P: 1-5 m

I: 10-50 Hz

Setpoint: Working point WP as indicated in Figure 18.

Inv. Polarity: not checked (signal ADC1 is expected to increase with

increasing Z)

In the 'Coarse' tab one can find the 'Auto Approach' box where the

following parameters should be entered:

Delay: 10ms

Threshold: a value bigger than ADC1min

Stop Cond.: > Threshold

Speed: 2V/s (@RT), 3V/s (@LT)

Steps/Apr.: See Data Sheet at the end of this section

Apr. Mode.: When the stop condition is met, you can either

tell the ASC 500 to remain within the feedback

mode or to immediately retract. To choose

'Retract' is of course the safer procedure.

Target Mode: Retract

Page 46

Press the ‘Autoapproach Details’ where the following parameters should be

entered:

Coarse Axis: Axis 3

Coarse Dir.: Forward

Coarse Device: ANC150

Coarse Trig. Pol.: High Active

Coarse Trig. Hold Time: 1ms

Check the ‘Axis 3’ settings to have reasonable values for the coarse

positioning, for example:

Frequency: 200-1000Hz

Amplitude: 30V (@RT), 50V(@LT)

3. Z Spectroscopy:

After the ‘Auto Approach’, run a so-called ‘z Spectroscopy’. This is a

spectroscopy where the feedback parameter is monitored while the z

scanner moves the sample surface towards the tip until some breakdown

condition is reached. To perform this spectroscopy, we recommend to enter

the following values/ranges into one of the three ‘Spec’ windows

(Spec1,Spec2 or Spec3):

Page 47

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Start: 0pm

End: maximum z scanner stroke. See data

sheet at the end of this section.

Data Points: 1000

Fwd/Bkwd: not checked

Data Point Avg. Time: 2-10 ms

Delay Per Data Point: 0 s

Now open the ‘Details Spectroscopy’ sub menu and enter the following

parameters:

Limiter: (Stops the z spectroscopy before the a certain force onto the tip is

exceeded)

Active: checked

Source: ADC1

Value: higher than the interference minimum

Sign: Source > Value

Start the z Spectroscopy

The ‘jump-to-contact (JTC)’, will now be seen in a rather sharp ‘jump-like’

increase of the interference signal (ADC1).

Note, that it is suggestive (for the validity of the scale calibration) to keep

the feedback in the middle of the z scanner range. Move manually upwards

(or downwards) with the z positioner step by step to adjust this position.

During the contact-mode measurement, the fiber-tip distance is tried to be

kept constant. This means that the deflection of the cantilever and therefore

the force between tip and sample is kept constant by the P/I-feedback loop.

Page 48

V.2.d. Starting a scan

To finally start the scan check the following parameters in the feedback box

as already shown before:

Actual Value: SPM ADC1

Z limit min: 0nm

Z limit max: maximum z scanner stroke (see data sheet

at the end of the manual).

P: 1-5 m

I: 10-50 Hz

Setpoint: Working point WP as described in the two

subsections above

Inv. Polarity: not checked for contact mode(signal ADC1

is expected to increase with increasing Z)

checked for non-contact mode(signal ADC1

is expected to decrease with increasing Z)

In the ‘Scanner’ box select the scan area (blue shaded area) of interest and

choose a slow ‘Scan Speed’ (< 3 µm/s) to start the scan.

Now the feedback can be activated by checking the ‘Loop On’ box. The z

piezo will expand and the tip will go into contact.

Before you start the scan, select the appropriate signals in the ‘Frame/Line

View’ tab:

Page 49

companies. Any rights not expressly granted herein are reserved. ATTENTION: Specifications and technical data are subject

to change without notice.

Normally, in contact mode ‘ADC1’ (error signal) and the ‘SPM Z out inv’

(topography signal) is recorded.

In non-contact mode ‘AFM Aosc’ (error signal) and the ‘SPM Z out inv’

(topography signal) is recorded.

During scanning, the P and I parameters of the feedback loop have to be

adjusted according to the chosen scan speed and the surface roughness. At

the same scan speed, for example, a rougher surface will need a faster

feedback loop compared to a smooth surface.

In addition, the sample tilt can be compensated by setting a proper slope

compensation value for x and y. This feature can also be found in the

‘Feedback’ box.

Choosing P, I parameters:

To find reasonable start values for the P, I parameters, a 'Setpoint

Modulation' can be used. This feature is found in the 'Feedback’ box. As

parameters choose:

Setpoint Mod.: Periodic Rectangle

Period: 1s

Value: 95% or 105% of current setpoint

Start the feedback. The setpoint modulation will simulate a step-like pattern

on the sample surface. You can choose P and I for minimum response time

without overshoot (increase P and/or I) or lower noise.

Now, a scan may be started.

Page 50

attocube systems AG

Königinstrasse 11a (Rgb)

D-80539 München

Germany

Phone +49 89 2877 809 0

Fax +49 89 2877 809 19

Manual Atto AFMI MFM KPFM P5788

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