estructuras mediante microscopía de fuerza atómica - SMCr

LA SOCIEDAD MEXICANA DE CRISTALOGRAFÍA, A.C.
SE HONRA EN PUBLICAR EL PRESENTE TEXTO,
FRUTO DEL ESFUERZO DEL AUTOR
Y AGRADECE MUY ESPECIALMENTE A
F A C U L T A D D E Q U Í M I C A, U N A M
F U N D A C I Ó N R O B E R T O M E D E L L Í N , S. C.
POR OTORGAR EL APOYO FINANCIERO PARA SU IMPRESIÓN
Portada: Mariposa Monarca: composición realizada de una fotografía tomada por Luis
Vilchez
SOCIEDAD MEXICANA DE
C R I S T A L O G R A F Í A , A.C.
ESTRUCTURAS MEDIANTE MICROSCOPÍA
DE FUERZA ATÓMICA
POR
ING. CARLOS SEGOVIA URBANO
MICRA INGENIERÍA, S.A.
SOCIEDAD MEXICANA DE CRISTALOGRAFÍA,
A.C.
MÉXICO, D.F.
NOVIEMBRE 2003
Prefacio
La Sociedad Mexicana de Cristalografía realiza su IV Congreso Nacional, en esta ocasión
en Morelia, Michoacán. Convirtiéndose sus notas de curso ya una costumbre, aunque así lo
demanden sus motivos estatutarios, estas publicaciones emanadas de los cursos ofrecidos
en cada evento, se han convertido en un elemento valioso de consulta cotidiana.
En esta ocasión el Ingeniero Carlos Segovia, de Micra Ingeniería, nos ofrece el curso
Estructuras por Microscopia de Fuerza Atómica.
Esta contribución comienza describiendo las técnicas utilizadas por la Microscopia de
Fuerza Atómica en el capitulo 1, y el capitulo 2 lo dedica a la descripción del barrido con
los problemas inherentes a la linealidad. Los capítulos 3 y 4 ahondan en la descripción de
las sondas utilizadas y en los artificios requeridos para la construcción de imágenes. Por
último, reitera en el capitulo 5, los beneficios que brinda el instrumento.
La Sociedad Mexicana de Cristalografía agradece al Ingeniero Segovia y le satisface
presentar este trabajo a la comunidad cristalográfica mexicana, la que indudablemente
reconocerá el esfuerzo del Ingeniero Segovia para contribuir al avance de la cristalografía
en México.
José Luis Boldú
México, D.F. noviembre de 2003
Contents
i
CONTENTS ................................................................................ I
INTRODUCTION....................................................................................... V
CHAPTER 1 SPM TECHNIQUES ............................................................... 1
1.1
1.2
Scanning Tunneling Microscopy.............................................................. 2
Atomic Force Microscopy ........................................................................ 5
1.2.1 Contact AFM ................................................................................... 7
1.2.2 Non-contact AFM .......................................................................... 10
1.2.3 Intermittent-contact AFM .............................................................. 13
1.3
Magnetic Force Microscopy................................................................... 13
1.4 Lateral Force Microscopy.............................................................................. 15
1.5
Other SPM Techniques........................................................................... 17
1.5.1 Force Modulation Microscopy....................................................... 17
1.5.2 Phase Detection Microscopy ......................................................... 18
1.5.3 Electrostatic Force Microscopy ..................................................... 20
1.5.4 Scanning Capacitance Microscopy................................................ 21
1.5.5 Scanning Thermal Microscopy ...................................................... 21
1.5.6 Near-field Scanning Optical Microscopy ...................................... 22
1.5.7 Nanolithography ............................................................................ 22
1.6
SPMs as Surface Analysis Tools............................................................ 26
1.6.1 Scanning Tunneling Spectroscopy................................................. 26
1.6.2 Force vs. Distance Curves.............................................................. 27
1.7
SPM Environments................................................................................. 30
1.7.1 Ultra-high Vacuum ........................................................................ 30
1.7.2 Ambient.......................................................................................... 31
1.7.3 Liquid............................................................................................. 31
1.7.4 Electrochemical.............................................................................. 32
1.8
Further Reading ...................................................................................... 32
ii
Contents
CHAPTER 2 THE SCANNER ................................................................... 35
2.1
2.2
2.3
2.4
2.5
2.6
Scanner Design and Operation ............................................................... 36
Scanner Nonlinearities............................................................................ 39
2.2.1 Intrinsic Nonlinearity..................................................................... 39
2.2.2 Hysteresis....................................................................................... 40
2.2.3 Creep .............................................................................................. 42
2.2.4 Aging.............................................................................................. 44
2.2.5 Cross Coupling............................................................................... 46
Software Correction................................................................................ 48
Hardware Correction .............................................................................. 49
2.4.1 Optical Techniques ........................................................................ 51
2.4.2 Capacitive Techniques................................................................... 51
2.4.3 Strain-gauge Techniques................................................................ 51
Tests for Scanner Linearity .................................................................... 52
2.5.1 Intrinsic Nonlinearity..................................................................... 52
2.5.2 Hysteresis....................................................................................... 53
2.5.3 Creep .............................................................................................. 53
2.5.4 Aging.............................................................................................. 55
2.5.5 Cross Coupling............................................................................... 56
2.5.6 Step Profile: Hysteresis, Creep, and Cross Coupling in Z............ 56
Further Reading ...................................................................................... 57
CHAPTER 3 SPM PROBES ................................................................... 58
3.1
3.2
3.3
3.4
3.5
3.6
Introduction ............................................................................................ 58
Cantilevers .............................................................................................. 58
3.2.1 Properties of Cantilevers................................................................ 59
Tip Shape and Resolution....................................................................... 60
How to Select a Probe ............................................................................ 65
Probe Handling ....................................................................................... 69
Further Reading ...................................................................................... 69
Contents
iii
CHAPTER 4 IMAGE ARTIFACTS .............................................................. 70
4.1
4.2
4.3
4.4
4.5
4.6
Tip Convolution...................................................................................... 70
Convolution with Other Physics............................................................. 73
Feedback Artifacts.................................................................................. 73
Image Processing Capabilities................................................................ 74
Test for Artifacts..................................................................................... 75
Further Reading ...................................................................................... 75
CHAPTER 5 KEY FEATURES OF SPMS ................................................... 76
5.1
User Interface ......................................................................................... 76
5.2
Optical Microscope ................................................................................ 76
5.3
Probe Handling ....................................................................................... 78
5.4
System Accessibility............................................................................... 78
Notes:..................................................................................................................... 1
iv
Contents
Introduction
v
INTRODUCTION
In the early 1980's scanning probe microscopes (SPMs) dazzled the world with
the first real-space images of the surface of silicon. Now, SPMs are used in a
wide variety of disciplines, including fundamental surface science, routine
surface roughness analysis, and spectacular three-dimensional imaging—from
atoms of silicon to micron-sized protrusions on the surface of a living cell.
The scanning probe microscope is an imaging tool with a vast dynamic range,
spanning the realms of optical and electron microscopes. It's also a profiler with
unprecedented 3-D resolution. In some cases, scanning probe microscopes can
measure physical properties such as surface conductivity, static charge
distribution, localized friction, magnetic fields, and elastic moduli. As a result,
applications of SPMs are very diverse.
This booklet was written to help you learn about SPMs, a process that should
begin with a thorough understanding of the basics. Issues covered in this booklet
range from fundamental physics of SPMs to their practical capabilities and
instrumentation. Examples of applications are included throughout the text, and
several application-specific articles are listed at the end of each chapter.
ThermoMicroscopes was founded in 1998 with the merging of Park Scientific
Instruments and TopoMetrix Corporation. Since the founding of these companies
at the end of the 1980s, we have maintained strong ties to the academic
community and a corporate philosophy that combines technology leadership with
a practical-applications orientation. Our Analytical Services Laboratories work
with customers to demonstrate the ability of our SPMs to meet their needs. We
believe that the more you know about scanning probe microscopes, the more
likely you'll be to choose our products. We want to provide you with the basic
facts about SPMs before you make your way through sales literature—which
tends to be more persuasive and less informative.
We hope you enjoy reading about this exciting technology. When you finish
reading this booklet, please contact us. An order form for our sales literature is
included at the back of the booklet. We'd also like to show you images from our
image library, which spans a wide variety of applications.
vi
Introduction
Key Features of SPMs
79
ThermoMicroscopes
Notes:
Primera Impresión: noviembre de 2003
Tiraje total: 100
D.R.@ 2003, Sociedad Mexicana de Cristalografía, A.C.
Cd. de México
Impreso en México