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Electronics of Electron Microscopes
Elroy Tatem
Bradley Thiel and Miguel Rodriguez
University at Albany Summer Research Program
College of Nanoscale Science & Engineering
Introduction
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Troubleshoot and repair a
malfunctioning scanning electron
microscope (SEM)
Troubleshoot and repair a transmission
electron microscope (TEM)
College of Nanoscale Science & Engineering
A Vital Research Tool
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Characterization tools are necessary in all areas of research at
CNSE
Must be made available for students, professors, and other
personnel to use
Taken from <http://www.trafficticketpayment.com/images/cartoon_line.big.jpg>
College of Nanoscale Science & Engineering
Why not Use an Optical Microscope?
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Much greater resolving power
• Resolution is limited by the wavelength of the incident beam
Taken from J.I. Goldstein, Scanning Electron Microscopy and X-Ray Microanalysis,
(Plenum Press,NY,1980)
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Why Not Use an Optical Microscope? (Cont.)
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Optical microscopes use light
• The wavelength of visible light is a few hundred nanometers
• High resolution optical microscopes can use light at a wavelength of
about 20nm
Electron microscopes use electrons
• Wavelength of an electron beam can be smaller than a tenth of a
nanometer
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What is an SEM?
College of Nanoscale Science & Engineering
The Breakdown
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The SEM is a series of systems
that must communicate with each
other
• Detector(s)
• Vacuum
• High voltage supply • Signal processing system
• Display
• Inputs
• Electron optics
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How do they communicate?
College of Nanoscale Science & Engineering
College of Nanoscale Science & Engineering
The Problem With this SEM
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The first observation
• No horizontal deflection while in
TV mode
• There is vertical deflection
• None of the other visual modes
have this problem
College of Nanoscale Science & Engineering
What does this Tell Us?
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Problem can be in one of
three places
• Scan Coil
• CRT
• Source of scan signal
Start from the source
• The best way to start
troubleshooting is to find
the source of the signal.
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Troubleshooting
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Troubleshooting tools
• Logic probe
• Multimeter
College of Nanoscale Science & Engineering
Troubleshooting
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Troubleshooting tools
• Oscilloscope
• Knowledge of electronic circuits
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Troubleshooting Techniques
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Finding where the signal begins
Collecting careful and useful data
Utilizing test sockets
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Collecting Data
College of Nanoscale Science & Engineering
Test Points
College of Nanoscale Science & Engineering
Circuits of Interest
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Switch board
• All of the relay switches that refer to mode selection and raster speeds
are controlled on this board
Divider circuit
• This circuit creates signals depending on what functions are selected
Logic circuit
• Most of the signal timing and synchronization takes place here
College of Nanoscale Science & Engineering
College of Nanoscale Science & Engineering
Challenges
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A lot of systems
Complex interconnected circuitry
Hard to reach components
Obsolete Chips
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Challenges
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Incomplete documentation
Undocumented after-market
modifications
Companies don’t like when people fix
things themselves
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Not Completed, However…
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Narrowed down possible problem areas
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Provided additional data for technicians to review
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In storage… for the time being
College of Nanoscale Science & Engineering
What I learned
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Differences in theoretical vs experimental analysis
• Calculating values
• Making practical assumptions
Inner workings of the electron microscope
• Understanding of almost any electron microscope circuitry
• Most industry standard SEMs function the same way
Troubleshooting complex circuitry
• Can take my experience anywhere
• Component-wise, electronic circuitry is the same in any device
College of Nanoscale Science & Engineering
Current Work
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Transmission electron microscope (TEM)
• High voltage power supply appears to be malfunctioning.
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The Problem in More Detail
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The problem most likely lies within the Cockcroft – Walton
rectification circuit used for voltage amplification
College of Nanoscale Science & Engineering
The Problem
College of Nanoscale Science & Engineering
Special Thanks
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Brad Thiel
• Professor (Mentor Extraordinaire)
Miguel Rodriguez
• Sr. Technician (The Man)
Cathy Dunn
• Professor
Lorena Coscio
• Student affairs
Tara “The beautiful one” GarciaCollins
• Resident assistant
Nana “Queens’ finest” Mensah
• Resident assistant
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Anthony Weathers
• Cantilever kid
Marc-Anthony Armand
• Ion beam certified
Marc Carter
• Program Coordinator
Carson Carr
• THE MAN
You and you and you and you and
especially you
College of Nanoscale Science & Engineering
References
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Otsuka Tokio
• A Technical Guide for Engineers Using Electron Microscopes
• 20, August 1991 Technical Material Dept, JEOL
Museum of Science online
• Scanning Electron Microscope http://www.mos.org/sln/sem/intro.html
• 1996 Museum of Science
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Ask Now, or Forever Hold Your Piece
College of Nanoscale Science & Engineering