college of nanoscale science & engineering elroy tatem bradley thiel and miguel rodriguez...

College of Nanoscale Science & Engineering

Elroy Tatem

Bradley Thiel and Miguel Rodriguez

University at Albany Summer Research Program

Electronics of Electron Microscopes


Introduction

Troubleshoot and repair a malfunctioning scanning electron microscope (SEM)

Troubleshoot and repair a transmission electron microscope (TEM)


A Vital Research Tool

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>


Why not Use an Optical Microscope?

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)


Why Not Use an Optical Microscope? (Cont.)

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


What is an SEM?


The Breakdown The SEM is a series of systems

that must communicate with each other

• VacuumVacuum

• High voltage supplyHigh voltage supply

• InputsInputs

• Electron opticsElectron optics

• Detector(s)Detector(s)

• Signal processing systemSignal processing system

• DisplayDisplay


How do they communicate?


The Problem With this SEM

The first observation

• No horizontal deflection while in TV mode

• There is vertical deflection

• None of the other visual modes have this problem


What does this Tell Us?

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.


Troubleshooting

Troubleshooting tools

• Logic probe

• Multimeter


Troubleshooting

Troubleshooting tools• Oscilloscope

• Knowledge of electronic circuits


Troubleshooting Techniques

Finding where the signal begins Collecting careful and useful data Utilizing test sockets


Collecting Data


Test Points


Circuits of Interest

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


Challenges

A lot of systems Complex interconnected circuitry Hard to reach components Obsolete Chips


Challenges

Incomplete documentation

Undocumented after-market modifications

Companies don’t like when people fix things themselves


Not Completed, However…

Narrowed down possible problem areas

Provided additional data for technicians to review

In storage… for the time being


What I learned

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


Current Work

Transmission electron microscope (TEM)• High voltage power supply appears to be malfunctioning.


The Problem in More Detail

The problem most likely lies within the Cockcroft – Walton rectification circuit used for voltage amplification


The Problem


Special Thanks

Brad Thiel

• Professor (Mentor Extraordinaire) Miguel Rodriguez

• Sr. Technician (The Man) Cathy Dunn

• Professor Lorena Coscio

• Student affairs Tara “The beautiful one” Garcia-

Collins

• Resident assistant Nana “Queens’ finest” Mensah

• Resident assistant

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


References 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


Ask Now, or Forever Hold Your Piece

college of nanoscale science & engineering elroy tatem bradley thiel and miguel rodriguez...

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