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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 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 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? 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) College of Nanoscale Science & Engineering 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 College of Nanoscale Science & Engineering What is an SEM? College of Nanoscale Science & Engineering The Breakdown 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 College of Nanoscale Science & Engineering How do they communicate? College of Nanoscale Science & Engineering College of Nanoscale Science & Engineering 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 College of Nanoscale Science & Engineering 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. College of Nanoscale Science & Engineering Troubleshooting Troubleshooting tools • Logic probe • Multimeter College of Nanoscale Science & Engineering Troubleshooting Troubleshooting tools • Oscilloscope • Knowledge of electronic circuits College of Nanoscale Science & Engineering Troubleshooting Techniques Finding where the signal begins Collecting careful and useful data Utilizing test sockets College of Nanoscale Science & Engineering Collecting Data College of Nanoscale Science & Engineering Test Points College of Nanoscale Science & Engineering 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 College of Nanoscale Science & Engineering College of Nanoscale Science & Engineering Challenges A lot of systems Complex interconnected circuitry Hard to reach components Obsolete Chips College of Nanoscale Science & Engineering Challenges Incomplete documentation Undocumented after-market modifications Companies don’t like when people fix things themselves College of Nanoscale Science & Engineering Not Completed, However… Narrowed down possible problem areas Provided additional data for technicians to review In storage… for the time being College of Nanoscale Science & Engineering 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 College of Nanoscale Science & Engineering Current Work Transmission electron microscope (TEM) • High voltage power supply appears to be malfunctioning. College of Nanoscale Science & Engineering The Problem in More Detail 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 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 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 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 College of Nanoscale Science & Engineering Ask Now, or Forever Hold Your Piece College of Nanoscale Science & Engineering