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אוניברסיטת בן-גוריון בנגב הפקולטה למדעי ההנדסה המחלקה להנדסת חשמל ומחשבים Scanning Probe Microscope - SPM - Present Rony Levin Email levinbr@ee.bgu.ac.il Course Nanotechnology Number 361-2-0826 Lecturer Dr. Ilan Shalish Agenda Terms Definition Historical Overview SPM Overview

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אוניברסיטת בן-גוריון בנגב

הפקולטה למדעי ההנדסה

המחלקה להנדסת חשמל ומחשבים

Scanning Probe Microscope

- SPM -

Present Rony Levin

Email levinbr@ee.bgu.ac.il

Course Nanotechnology

Number 361-2-0826

Lecturer Dr. Ilan Shalish


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Agenda

  • Terms Definition

  • Historical Overview

  • SPM Overview

  • SPM Software

  • STM Overview

  • AFM Overview

  • Summary


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Terms Definition

MicroscopyμΙκροσ-small, σκοποσ– see

Scanning Probe Microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen

Artifact is any perceived distortion or other data error caused by the instrument of observation

Cantilever is a beam supported on only one end

from wikipedia


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Terms Definition

Input transducer or sensor

Convert nonelectrical signal to electrical one

Output transducer or actuator

Convert electrical signal to nonelectrical one

Piezoceramic

Ceramic that convert electrical field to mechanical deformation and vice versa

Piezoelectric properties are time-depended


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Acronyms

SPM Scanning Probe Microscope

STM Scanning Tunneling Microscope

AFM Atomic Force Microscope

SFM Scanning Force Microscope

FFM Force-Modulated AFM

LFM Lateral Force Microscope

MFM Magnetic Force Microscope

SThM Scanning Thermal Microscope

EFM Electrical Force Microscope


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Historical Overview

  • 1981 STM was developed by Binnig and Rohrer, IBM, Zurich

  • 1986 AFM was developed by Binnig, Quarter and Gerber

  • 1988 Commercial SPM available

  • 1990 Analog electronics replaced by digital

  • 1990 Software for SPM based Microsoft Windows developed

  • from 1990 SPM market wake up

    Agilent Technologies, nanoScience …


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SPM Physical ModelThe Blind Mouse

Computer

Actuator

Probe

Sensor

Sample


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Blind Mouse Operational Principle

The blind mouse can’t see the object (sample), but using the stick (probe), he can scan it.

Arm skin (sensor) send the received from the probe information to the brain (computer), the computer “see” the picture, if it need receive additional information about the sample (decision done using feedback), it send requirement to arm muscle (actuator), arm carefully moves the probe to required coordinate and vice versa


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SPM Operational Principle

All of the SPM techniques are based upon scanning a probe (typically called the tip, since it literally is a sharp metallic tip) just above a surface whilst between scanned surface and probe exist interaction

The nature of this chosen interaction defines a device accessory to this or that type within the family of Scanning Probe Microscope

The information on a surface is taken by fixing (by means of feedback system) or monitoring of interaction of a probe and the sample


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SPM Operational Principle

We will present scanning probe microscopes based on two kind of iteration

  • Iteration is electrical current STM

  • Iteration is atomic force AFM/SFM

    In general, as mentioned, SPM have two modes, defined by tip movement over the surface

  • Fixed probe Z coordinate, iteration or parameter depended on iteration monitoring

  • Fixed iteration, height change monitoring



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Potential Barrier Schematics

V is bias voltage

EF is Fermi level


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Step Potential Barrier

Schrödinger time invariant equation


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Transfer Matrix

General solution

Using C1 connectivity


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Transfer Matrix

Transfer Matrix Definition

Now it can be written more simple


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Transfer Matrix

We received very powerful mathematical tool. Using this algorithm and Matlab we can solve complicated potential barriers




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Tunneling-Summary

Received result is not so suitable for classical physics theory, were electron position defined as “to be or not to be”

In quantum mechanics theory electron position defined as “may be” and appropriate number from 0 to 1 that describe the chance of electron to be in some coordinate.

Summarizing all the electrons over all energy levels, that can pass the barrier, will receive tunneling current expression



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Distance Sensitivity

What happened if current will be changed, how mach it will affect the distance?

Assume that K=4 eV, current precision is 2%


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Feedback

control signal

Control

System

feedback signal

error

reference


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Calibration

  • Error as result of non orthogonal axes and reference point definition

  • Error as result of probe geometric shape

  • Error as result of sensor sensitivity

In order to avoid measurement errors depended on setup, mandatory to perform pre measurement system calibration




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Thank You

for Attention


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Stam

  • SPM