DWJ's+11.26-11.29


 * **11/26/07 Monday**

I found a picture that shows where all the things are located. Here are explanations and a picture.

A beam of electrons is generated in the electron gun, located at the top of the column, which is pictured to the left. This beam is attracted through the anode, condensed by a condenser lens, and focused as a very fine point on the sample by the objective lens. The scan coils are energized (by varying the voltage produced by the scan generator) and create a magnetic field which deflects the beam back and forth in a controlled pattern. The varying voltage is also applied to the coils around the neck of the Cathode-ray tube (CRT) which produces a pattern of light deflected back and forth on the surface of the CRT. The pattern of deflection of the electron beam is the same as the pattern of deflection of the spot of light on the CRT.

The electron beam hits the sample, producing secondary electrons from the sample. These electrons are collected by a secondary detector or a backscatter detector, converted to a voltage, and amplified. The amplified voltage is applied to the grid of the CRT and causes the intensity of the spot of light to change. The image consists of thousands of spots of varying intensity on the face of a CRT that correspond to the topography of the sample.



The electron beam hits the sample, producing secondary electrons from the sample. These electrons are collected by a [|secondary detector] or a [|backscatter detector], converted to a voltage, and amplified. The amplified voltage is applied to the grid of the CRT and causes the intensity of the spot of light to change. The image consists of thousands of spots of varying intensity on the face of a CRT that correspond to the topography of the sample.

http://mse.iastate.edu/microscopy/path.html ||
 * **11/27/07 Tuesday**
 * **11/27/07 Tuesday**

I have found some information about backscatter detector which I have read yesterday. Backscatter electrons are another useful method of analysis. These electrons are the results of reflected (or backscattered) primary beam electrons from the sample. Backscattered electrons are useful for compositional analysis since their yield increases with the sample’s atomic mass. Characteristic X-rays are generated by the primary electron beam through interaction with sample’s atoms. The energy of these x-rays can be used to identify the parent atom. The technique used to identify the characteristic x-ray is Energy Dispersive X-ray Spectroscopy (EDS). Other useful SEM techniques, particularly for the IC analyses, are voltage contrast and Electron Beam Induced Current (EBIC). http://www.siliconfareast.com/SEMTEM.htm ||
 * **11/28/07 Wednesday**
 * **11/28/07 Wednesday**

Organize what I have done and review what I have read. I will also read the SEM text book from ND at home. ||
 * **11/29/07 Thursday**



It is random that I put this picture. but I just put it, because this picture is really good picture showing SEM with computer that captures pictures.

Today, i will organize Secondary Electron Detector and Backscatter Electron Detector that I have been discovered this week.


 * First, Secondary Electron Detector.**

For each high energy electron striking the surface, usually many low energy secondary electrons are given off the surface. The secondary electron detector sweeps up these electrons and forms an image based on the number of secondary electrons. The secondary electron detector gives the best resolution and it is the mostly commonly used detector.


 * Secondly, Backscatter Electron Detector.**

A backscattered electron is an electron that scatters off the nucleus of an atom. The larger the nucleus of the atom, the more electrons are backscattered. As a result, the backscatter electron detector gives good compositional contrast. If the compositional information from the detector is subtracted off, the result is a surface topography image.

Also, I have found what **Energy Dispersive X-ray System (EDS)** is and what it does. The Oxford Pentafet energy dispersive X-ray detector (EDS) is available for qualitative and semi-quantitative elemental analysis. The EDS detector has an ultra-thin window that allows for element detection of carbon and higher atomic number elements. An elemental or X-ray map of the surface can also be obtained using this detector. Also, EDS identifies the elemental composition of materials imaged in a Scanning Electron Microscope for all elements with an atomic number greater than boron. Most elements are detected at concentrations of order 0.1%. Also, instead of using EDS, WDS is possible. WDS identifies the elemental composition of materials imaged in the __SEM__ with an order of magnitude better spectral resolution, sensitivity and ability to determine concentratins of light elements than is achievable with EDS. Most elements are detected below 0.1% and some as low as a few ppm.

**WDS vs. EDS**
X-ray microanalysis in the scanning electron microscope is accomplished using EDS and/or WDS. EDS is more commonly applied due to its simplicity and speed, while WDS offers an important and often critical refinement of EDS data by providing

And here is an example of showing EDS. To show EDS, they use this kind of graph. The letter written which is yellow shows the element with the series of Alpha and Beta. EDS Spectra of Nd-Fe-B Permanent Magnet (7.5 KB GIF)

I found a web site that you can do activities with **Bee eye and Carpet Beetle** using SEM

Go and Try ! ! : ) http://education.denniskunkel.com/Java-SEM-begin.php

I also found really fun fun play with SEM.

There is an image of **ant** taken from SEM, and you can change things. If you click anything, you can see the effect of varying the Lucis DCR settings on the resulting images.

Go and Try ! ! : ) http://www.imagecontent.com/lucis/applications/bio/sem1/sem1.html ||