DWJ's+12.03-12.07


 * **12/03/07 Monday**

I am going to read the SEM book, and review what i have done. ||
 * **12/04/07 Tuesday**

**Preparation before using SEM:**Before we use SEM, we need to prepare for something such as sample collection.Sample preparation can be minimal or elaborate for SEM analysis, depending on the nature of the samples and the data required. Minimal preparation includes acquisition of a sample that will fit into the SEM chamber and some accommodation to prevent charge build-up on electrically insulating samples. Most electrically insulating samples are coated with a thin layer of conducting material, commonly carbon, gold, or some other metal or alloy. The choice of material for conductive coatings depends on the data to be acquired: carbon is most desirable if elemental analysis is a priority, while metal coatings are most effective for high resolution electron imaging applications. Alternatively, an electrically insulating sample can be examined without a conductive coating in an instrument capable of "low vacuum" operation.**Vacuum System Components:** Pressure Terminology ||||||||||||||||||  ||
 * 1 atmosphere ||
 * 760mm Hg ||
 * 760 torr ||
 * 1.013bar ||
 * 101.3 kPa ||
 * Thus, 1 torr is roughly 1.3 mbar or 1.3 Pa ||
 * Vacuum Pumps:**
 * There are four types of vacuum pumps that are at least somewhat commonly employed in SEMs. I will go over the basic operational mechanisms and operational parameters of each, then put each into their place in a typical SEM. ||
 * **12/05/07 Wednesday**
 * 101.3 kPa ||
 * Thus, 1 torr is roughly 1.3 mbar or 1.3 Pa ||
 * Vacuum Pumps:**
 * There are four types of vacuum pumps that are at least somewhat commonly employed in SEMs. I will go over the basic operational mechanisms and operational parameters of each, then put each into their place in a typical SEM. ||
 * **12/05/07 Wednesday**
 * There are four types of vacuum pumps that are at least somewhat commonly employed in SEMs. I will go over the basic operational mechanisms and operational parameters of each, then put each into their place in a typical SEM. ||
 * **12/05/07 Wednesday**

Today, I will watch the video of ND professor teaching about SEM ||
 * **12/06/07 Thursday**
 * **12/06/07 Thursday**

I have searched some disadvantages of SEM Electron microscopes are expensive to buy and maintain. They are dynamic rather than static in their operation: requiring extremely stable high-voltage supplies, extremely stable currents to each electromagnetic coil/lens, continuously-pumped high-/ultra-high-vacuum systems, and a cooling water supply circulation through the lenses and pumps. As they are very sensitive to vibration and external magnetic fields, microscopes aimed at achieving high resolutions must be housed in buildings (sometimes underground) with special services. Newer generations of TEM operating at lower voltages (around 5 kV) do not have stringent voltage supply, lens coil current, cooling water or vibration isolation requirements and as such are much less expensive to buy and far easier to install and maintain. ||

Review what I have done for this week. And read over all info that I have found and printed. ||
 * **12/07/07 Friday**