A New Scanning Method for Fast Atomic Force

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A NEW SCANNING METHOD FOR

FAST ATOMIC FORCEMICROSCOPY

Guided By Submitted By

Mrs.SOUMYA.D.S NINU.J.S

Asst.Professor S1, AEI

Dept.of ECE YCET

YCET

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OVERVIEW

Introduction AFM working

Spiral scan

Comparison

System description & Identification

Advantage & Disadvantage

Future Enhancement

Conclusion

Bibliography

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INTRODUCTION

Atomic Force microscope (AFM) has an important tool in

nanotechnology.

It was first conceived to generate 3-D images of

conducting as well as non conducting surfaces.

It is also used for the manipulation of material surface at

nanoscale.

Introduce a new scanning method to AFM.

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Sample is scanned in the spiral pattern.

Spiral scan have 2 modes

These scan method can be incorporated into the AFM

with minimal effort.

Spiral scan produce high quality images.

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Constant angular velocity spiral(CAV)

Constant linear velocity spiral(CLV)


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AFM

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Fig.1. Basic AFM schematic with feedback controllers.

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AFM have 2 modes of operation

Contact mode

Non contact mode

A raster scan is attained by applying triangular

waveform to the x-axis & ramp signal to the y-axis.

High speed raster scan need high frequency triangular

waveform.

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Fast triangular waveform results the distorted AFM

image.

Accuracy of the AFM image also affected by the

nonlinear properties.

Feed back control technique is used to avoid these

complications.

Spiral scan can be produce by applying the sinusoidal

signal as the inputs.

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SPIRAL SCAN

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The pattern is known as Archimedean spiral.

A property of the spiral is that its pitch P.

Fig.2. spiral scan

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CAV SPIRAL

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The differential equation that generate the CAV Spiral is

where

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Total scanning time associated with the CAV Spiral is

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The input signal applied to the scanner in the x & y axis is

Fig.3. Input signal to be applied in x-axis Fig.4. Input signal to be applied in y-axis

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There is a phase errors between the input & output signals.

These phase errors can be eliminated by introducing

the phase constants in the input signals.

The single frequency sinusoidal signals can be used to

track the CAV Spiral.

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CLV SPIRAL

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The differential equation that generate the CLV Spiral is

From these

Total scanning time of CLV Spiral is

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The input signals that generate the CLV Spiral is

Fig.5. Input signal to be applied in x-axis Fig.6. Input signal to be applied in y-axis

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TOTAL SCAN TIME : SPIRAL

VERSUS RASTER

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For the equal area & pitch ,the total scanning time for both

raster & spiral scan is

The number of lines in the raster scanned image is

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Total scan time for the raster scanned image is

Total scanning time to generate the CAV Spiral is

Linear velocity of the raster scan is,

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TOTAL TRAJECTORY DISTANCE :

SPIRAL VERSUS RASTER SCAN

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Total trajectory distance of spiral scan is

Total trajectory distance of raster scan is

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MAPPING SPIRAL POINTS TO

RASTER POINTS

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Spiral scanned images are plotted by mapping spiral points

to raster points

Fig.7. Mapping in CAV Spiral Fig.8. Mapping in CLV Spiral

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SYSTEM DESCRIPTION

SPM was configured to operate as an AFM

The voltage amplifiers were replaced with the charge

amplifiers.

DSPACE system was used to implement the feedback

controllers.

Amplifiers & SPM were interfaced with the DSPACE

using a signal access module.

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Piezoelectric tube is platted with inner & outer electrodes.

Outer electrodes are segmented into 4 parts.

Bridge configuration of these electrode will halves the

input voltage requirement.

Fig.9. Bridge configuration of electrodes

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SYSTEM IDENTIFICATION

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Fig.10. Block diagram of the experimental setup used for system identification

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CONTROLLER DESIGN

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Controller achieve good damping ratio & higher tracking.

PPF increase the overall damping.

High gain integral controller provide tracking.

Fig.11. Structure of x-axis feedback controller

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ADVANTAGES

Good quality images are produced.

Scanning time is low compared to raster

scanning.

Less wear on the AFM tip.

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DISADVANTAGES

CLV mode spiral scanning requires high

bandwidth controller.

Scanning time gain will produce small

distortion at the centre of the image.

On the spiral image plotting ,computational

time will increases in CAV mode.

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FUTURE ENHANCEMENT

Spiral scanning will be also used in the

scanning tunneling microscopy(STM).

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CONCLUSION

A new scanning method can be incorporated in AFM.

The spiral scan have 2 modes CAV &CLV modes.

Spiral scanned images have great accuracy than raster

scan.

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BIBLIOGRAPHY

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[1] Y. K. Yong, S. Aphale, and S. O. R. Moheimani, Design,identification,and control of a flexure-based xy stage for fastnanoscale positioning,IEEETrans. Nanotechnol., vol. 8, no. 1,

pp. 4654, Jan. 2009.

[2] S. Devasia, E. Eleftheriou, and S.Moheimani, A survey of

control issues in nanopositioning,IEEETrans. Control Syst.Technol., vol. 15, no. 5,pp. 802823, Sep. 2007.

[3] N. Tamer and M. Dahleh, Feedback control of piezoelectrictube scan-ners, in Proc. 33rdIEEEConf. Decision Control,Dec. 1994, vol. 2,pp. 18261831.

[4] G. Binnig, C. F. Quate, and C. Gerber, Atomic forcemicroscope, Phys.Rev. Lett., vol. 56, no. 9, pp. 930933, Mar.1986.

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THANK YOU........

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A New Scanning Method for Fast Atomic Force