Gioi Thieu Kinh Hien Vi Luc Nguyen Tu

8/13/2019 Gioi Thieu Kinh Hien Vi Luc Nguyen Tu

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Scanning Probe Microscopy

Junior Research Seminar

Spring 2004

6 April 2004

Junior Research Seminar: Nanoscale Patterning and Systems

Teri W. Odom


2/24

Fundamental Principles

Imaging and Spectroscopy

Instrumentation

Atomic Force Microscopy


Teri W. Odom


3/24

Surface force history and measurements

Surface force apparatus

Studies of van der waals (VDW) interactions

Force between mica surfaces (molecules, liquid layers) fromdeflection of spring upon contact

Separation measured to 1 A; force sensitivity 10-8

N Surface profi lometers

Roughness of materials

Stylus tip in mechanical contact with surface (10-4 N)

1 m radius of curvature Forces and their range of influence

Long range

Electrostatic force in air (100 nm)

Magneto-electrostatic forces (100 nm)

Double layer electrostatic (fluid) (100 nm) Short range

Van der Waals (10 nm)

Surface-induced solvent ordering (5 nm)

Hydrogen-bonding force (0.2 nm)

Contact (0.1 nm)


Teri W. Odom


4/24

AFM tip and sample interaction

(1) Large tip-sample separations nodetectable interaction force

1

(2) Separation distance decreases

2

(3) Separation where the gradient of

interaction energy exceeds the

restoring force of the cantilever

jump to contact point

3

(4) Tip pushes farther into surface, a

positive linear cantilever deflection isobserved; tip retracts from surface,

a similar cantilever deflection line is

traced and the tip and sample

remain in contact

4

(5) Separation where restoring force

exerted by the bending of the

cantilever overcomes the adhesive

force of the tip-sample force of

interaction

5

(6) Non-interacting, equilibrium position

6

http://www.ntmdt.ru/SPM-Techniques/Spectroscopies/Force-distance_curves_mode20.html


Teri W. Odom


5/24



Instrumentation



Teri W. Odom


6/24

AFM: General Overview


Teri W. Odom


7/24


8/24

Force feedback

stm2.nrl.navy.mil/how-afm/how-afm.html


Teri W. Odom


9/24

Optical detection of cantilever changes

(A+B)-(C+D)

A B

C D

(A+C)-(B+D)


Teri W. Odom
http://images.google.com/imgres?imgurl=www.spmtips.com/app/Subjects/pics/lateral_deflection.gif&imgrefurl=http://www.spmtips.com/app/Subjects/probes_cantilevers.htm&h=240&w=300&prev=/images%3Fq%3Dafm%2Bschematic%26start%3D40%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DNhttp://images.google.com/imgres?imgurl=www.spmtips.com/app/Subjects/pics/vertical_deflection.gif&imgrefurl=http://www.spmtips.com/app/Subjects/probes_cantilevers.htm&h=240&w=300&prev=/images%3Fq%3Dafm%2Bschematic%26start%3D40%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN


10/24

Lateral resolution

Tip effects

Radius of curvature of tip

Cone angle and depth of tip

Aspect ratio of tip

Force interaction

Repulsive region can damagesample

Attractive region not enoughresolution


Teri W. Odom


11/24

Vibration Isolation Typical frequencies

1 Hz building vibrations (people

walking, etc.)

10 - 100 Hz building vibrations

(electronics, ventilation, etc.)

1 - 10 kHz resonant frequency

of most STMs

Ideal vibration contributions

Building vibrational amplitude of

1 m translates to 1 pm at the

STM junction

Solution

Make STM has rigid as

possible so that internal

resonance is high

Mount it on a low resonant

frequency support

Ai r suppor t tables

Spring suspensions

PICO SPM solutions


Teri W. Odom


12/24



Instrumentation



Teri W. Odom


13/24

Contact mode imaging Constant force image

Constant deflection

Strong repulsive regime

Tip makes physical contact with the

surface

Stiffness of cantilever less than springs

holding atoms (10 nN/nm)

VDW forces dominate

Well-suited for

Hard and shallow samples Samples with periodicity

Samples in liquid environments

Shao, U. Virginia

2.5m

Q. Xu, U. Virginia R. Bley, U. Virginia

80 nm

http://www.ntmdt.ru/SPM-Techniques/SFM/dc_Contact_techniques/Constant_Force_mode_mode9.html


Teri W. Odom


14/24

Lateral force microscopy

-COOH

-CH3

25 nN

C.M. Lieber, J. Am. Chem. Soc. 117, 7943 (1995)http://www.ntmdt.ru/SPM-Techniques/SFM/dc_Contact_techniques/Lateral_Force_Imaging_mode11.html


Teri W. Odom


15/24

Noncontact mode imaging Constant force gradient image

Amplitude or resonance frequency

feedback

Weak attractive regime

Tip oscillated 1-10 nm above thesurface

Stiff cantilever

Tip-sample forces ~ pN

Using for imaging

Soft surfaces Samples in ultra-high vacuum

2 m

Raspberry polymer, DI

10 m

5 m

Polystyrene spheres, DI

http://www.ntmdt.ru/SPM-Techniques/SFM/Non-Contact_techniques/Non-Contact_mode_mode57.html


Teri W. Odom


16/24

Tapping mode imaging

Constant force gradient image

Amplitude feedback

Weak repulsive force

Stiff cantilever makes intermittent

contact with the surface Well-suited for

Soft samples (biomolecules, polymers)

Samples with poor surface adhesion

Arene on graphite, T. Nguyen, Columbia

B. Stine, Northwesternhttp://www.ntmdt.ru/SPM-Techniques/SFM/Semicontact_techniques/Semicontact_mode_mode28.html


Teri W. Odom


17/24

Force spectroscopy

C.M. Lieber, J. Am. Chem. Soc. 117, 7943 (1995)C.M. Lieber, J. Am. Chem. Soc. 119, 2006 (1997)

http://www.ntmdt.ru/SPM-Techniques/Spectroscopies/Force-distance_curves_mode20.html

Titration curves


Teri W. Odom


18/24

Dip Pen Nanolithography


Teri W. Odom


19/24

Dip-Pen Nanolithography (DPN)

http://www.chem.northwestern.edu/~mkngrp/timeref.html#dpn


Teri W. Odom


20/24

DPN Writing


Teri W. Odom


21/24

Instrumentation


Teri W. Odom


22/24

Contact Time with Molecular Ink

C.A. Mirkin, Science 283, 661-663 (1999)

ODT tip MHA tip

10, 20, 40 s2, 4, 16 min

Probe

Ink diffusion

2

A r C t= =

2 time

units

3 time

units1 time

unit


Teri W. Odom


23/24

Towards Parallel Patterning

C. Mirkin, Science 288, 1808-1811 (2000)


Teri W. Odom


24/24

Labs 2 and 3: Atomic Force Microscopy

andDip-pen Nanolithography

Training on atomic force microscope

Writing patterns using DPN

Wet chemical etching

Lab report on both DPN and AFM due on

26 April


Teri W. Odom

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Gioi Thieu Kinh Hien Vi Luc Nguyen Tu