DWJ's+11.12-11.16


 * **11/12/07 Monday**

Today, I am going to review about what I have done and what I have read. Also I am going to have task list of this week. First of all, I have to have appointment of going to ND to research. I e-mailed yesterday and Brighid was available researching wednesday of this week. So I planned going to ND this wednesday and sent my response to her.

what I am going to do today is summarizing the Notre Dame SEM text book. Brighid told me it will be really confusing since it is college level book, and it was really COMPLECATED. Actually, it was hard to understand, There were a lot of words that I don't even know. She said it is okay if I don't understand. ( which made me comfortable of reading the book :) )

In the First chapter, it explains how important SEM is. The SEM is one of the most versatile instruments available for the examination and analysis of the microstructural characteristics of solid objects. A major reason for the SEM's usefulness is the high resolution which can be obtained when bulk objects are examined; instrumental resolution on the order of 1-5nm (10-50A) is now routinely quoted for commercial instruments.

Another important feature of the SEM is the large depth of field, which is responsible, in part, for the three-dimensional appearance of the specimen image. The greater depth of field of the SEM provides much more information about the specimen.

- **The third edition** (Scanning Electron Microscopy and X-Ray Microanalysis)

I have got lectures of SEM from ND professor, so if anyone wants to see this, ask me for them. ||
 * **11/13/07 Tuesday**

Today I have been searched for the Electron Source. First, the electron beam comes from a filament, made of various types of materials. The most common is the **Tungsten hairpin gun**. This filament is a loop of tungsten which functions as the cathode. A voltage is applied to the loop, causing it to heat up. The anode, which is positive with respect to the filament, forms powerful attractive forces for electrons. This causes electrons to accelerate toward the anode. Some accelerate right by the anode and on down the column, to the sample. Other examples of filaments are **Lanthanum Hexaboride filaments** and **field emission guns**.

Here is a picture, so it is much easier to understand...

http://mse.iastate.edu/microscopy/source.html ||  ||   || 11/15/07 Thursday 11/16/07 Friday
 * **11/14/07 Wednesday

I was absent due to fever and thyroid gland.** ||