Bruker公司原子力显微镜(AFM)工作原理及发展历史

where h is the thickness of the tube wall, V is the potential difference between internal and external electrodes. Thus, for the same applied voltage, the tube lengthening will be larger, for longer and thinner tubes.
Piezoceramics Creep
Piezoceramics creep is a delay in the response to sudden change of the control electric field value.
The creep results in appearance of geometrical distortions in SPM images. Specifically strong influence of the creep occurs, on initial stages of the scanning process, or after a large displacement of the starting point of the scanned area.
EFM KFM
SThM
SCM SSRM
MFM Force Spectroscopy
TUNA c-AFM
Basic Components of SPM - MultiMode 8
MultiMode 8 SPM System Components
Nanoscope V Controller and MultiMode 8 Base
Nanoscope V Controller
Dimension Stage Controller
Optics and Motor
Stage System
Dimension SPM Head
Position-Sensitive Photodetectors
The optical system is aligned so that the beam emitted by a diode-laser is focused on the cantilever, and the reflected beam hits the center of a photodetector. Four-section split photodiodes are used as position-sensitive photodetectors (PSPD).
Cantilever Holders
Various Cantilever holders for the MultiMode SPM
Basic Components of SPM - Dimension Icon SPM
Input and Display Equipment
Computer
Controllers
For small control fields the given dependence can be represented in the following way:
Typical values of fields E*, at which nonlinear effects cannot be neglected, are about 100 V/mm.
The probe microscope scanners are made of piezoelectric materials. Piezoelectric materials change their sizes in an external electric field.
The piezoceramics is polarized polycrystalline material obtained by powder sintering from crystal ferroelectrics.
Scanning Tunneling Microscope
STM is based on the fact that the tunneling current between a conductive tip and sample is exponentially dependent on their separation. This can be represented by the equation: I ~ Ve -cd This technique is typically limited to conductive and semiconducting surfaces
Wave Based Resolution Imaging Speed Imaging Depth Fast Penetration of Probe Slow~Medium Surface
Sensitivity
Versatility User Friendliness
Scanning Tunneling Microscope (STM)
Tapping Mode AFM Contact Mode AFM Torsional Resonance Mode (TRmode) AFM PeakForce Tapping AFM
Scanning Probe Microscopy
STM SFM
Scanning Probe Microscopy
P = P(z)
Working Mode
Tunneling Current i
Cantilever Amplitude A Cantilever Deflection D Cantilever TR Amplitude At Tip-Sample Force F
Demo: STM
AFM System
Detector Signal
Demo: AFM
Basic Working Principle
If there is a sharp enough and unique (single valued) dependence P = P (z) of that parameter on the tip-sample distance, then P can be used in the feedback system (FS) that control the distance between the tip and the sample.
Nanoscope V Controller inside
MultiMode 8 Head
MultiMode SPM Head and Major Components
Quad Photodetector Arrangement
MultiMode 8 Scanners
Voltages Applied to the X- and Yaxes Produce a Raster Scan Pattern
Tubular Piezoelement
Advantage: Allowing obtaining large enough movements with rather small control voltages. The relative longitudinal deformation under the influence of a radial electric field can be written as: where l0 is the length of the unstressed tube. The absolute lengthening of the piezo-tube is :
G．Binning and H．Rohrer invented the first Scanning Tunneling Microscope.
1986 Nobel Prize
STM is the first instrument that can reflect information of material surface in atomic scale.
Normally High
Limited Very Good
Medium
More Modes Being Improved
Comparison of AFM with Other Imaging Modalities
Optical Microscope Operating Environment Resolution in XY Resolution in Z Ambient, Liquid, Vacuum ~ 500 nm N/A Not completely transparent, refractive index different from environment
Sum, Vertical and Horizontal
The ΔIZ value is used as an input parameter in a feedback loop of the atomic force microscope.
Piezoceramic Plate in an External Electric Field
History, Principle and Working Modes of Scanning Probe Microscope
Sun Hao, 2012.4.23
5/7/2012
Outline
Basic Concepts and Hardware of SPM
Topography Imaging
SEM Vacuum 5 nm N/A Conductive surface, vacuum compatible
AFM Ambient, Liquid, Vacuum 1~10 nm 0.1 nm
Sample Requirement
Variation in depth<10 μm
The First SPM in the World
Piezoceramics Nonlinearity
Generally (especially at large control fields) the piezoceramics are characterized by nonlinear dependence of the deformation on the field. Thus, deformation of piezoceramics is a complex function of the applied electric field:
Tubular Piezo-scanner
X, Y Directions: When differential-mode voltage is applied on opposite sections of the external electrode (with respect to the internal electrode) part of the tube reduces in length and increases (where field and polarization directions are opposite). This leads to a bend of the tube. Z Direction: Change of the internal electrode potential with respect to all external sections results in lengthening or reduction of the tube along Z axis.
Properties Mapping
Surface Modification
Basic Concepts and Hardware of SPM
Two Imaging Methods
“Seeing” Method Wave based
“Touching” Method Probe Based
Comparison of Two Imaging Methods