SS#_________________________

Grade_____________

Mat Sc 430

1998 - HW8 - due 5 pm 11/13/98 (with usual grace period)

1. For each of the following situations in the use of EM, indicate whether you would adjust filament current, emission, or accelerating voltage, and whether you would increase or decrease the selected parameter. Give your reasoning. Some cases may have multiple possible answers; indicate the best approach.

a. the specimen is being significantly damaged by the e beam

b. the total brightness is too low; more illumination is required

c. the filaments appear to be wearing out too quickly - one/day instead of expected one/month

d. the specimen is charging up under the beam, causing difficulties in obtaining good images

2. A program called "virtual SEM" can be accessed on the computers in 106 Steidle. Use this program to observe real SEM images taken under a variety of conditions, and to see how changes in operating parameters affect the images. Complete on-line instructions are included. Take your time going through the various descriptions and the simulator itself. Once you have become familiar with the program and feel that you understand the material, go to the "Assessment" section. For this problem set, turn in answers to the two questions whose numbers end with the last integer of your SS#. Give a clear explanation for each as to why your answer is right and why the other answers are wrong, incomplete, and/or not as good as your choice. (Make sure your can do this for all of the questions, since it's possible some may show up on an exam.)