I. General Information

The UWM Surface Analysis Facility began operation on January 2, 1989. Since then, the laboratory has developed into the most comprehensive facility for surface analysis in the state of Wisconsin. The VG ESCALAB MKII spectrometer features monochromatic and small spot XPS, 2000 A Auger and Scanning Auger Microscopy, SEM, and Rear View LEED. The primary mission of the facility is to:

* aid faculty, staff, and graduate students in their research

* instruct students in experimental surface techniques (XPS, XPD, AES, and LEED)

* provide a service to analyze materials for industrial clients in Wisconsin.

The Surface Analysis Facility is open from 9:00am to 5:00pm week days and is available to users with adequate training in the evenings and weekends. All users can do data analysis from remote work stations located in the Physics or Engineering building through the university computer (PACX) network. If you access the ESCA computer remotely during a week day, a phone call to the facility would be appreciated to tell who is using the computer and your phone number (in case the computer is having problems).

A weekly user log is posted in the lab (on the inside of the entrance door) to ensure availability of the facility to users upon request (see Appendix A). The user should call the facility (229-6426) to sign up for time on the spectrometer during the following week. Due to the large number of interested research groups, it is recommended to schedule time in advance.

(a) Safety

* No one is permitted to work in the lab alone at any time

* The door to the facility must be left open whenever the facility is in use

(b) Log-in

* All users are required to log-in the time and date in the black ESCALAB LOG BOOK when they arrive and then log-out at the end of their experiment.

* All samples brought into the lab are to be logged-in the sample log book and a Materials Safety Data Sheet of their chemical properties should be on file in the facility before introducing any sample into the vacuum system ( see Appendix B).

* Any accident or unusual behavior of the system should be recorded in the ESCALAB blue book.

(c) Base Pressure

* The pressure in the prep and/or analysis chamber should never go higher than 1 X 10-8 torr (except when sputtering).

(d) Instrument Check List

* The "Check Lists" folder contains procedures and check lists for operating every feature of the ESCALAB MKII system. The operator is required to use these check lists at all times during the use of the system. The Check Lists folder should be kept near the system's main control panel at all times (see part II).

(e) Data Backup

* Users should backup all of their data onto their own floppy disks on a monthly basis. Hard disk failures are not unknown. Files on the hard disk will be deleted at least every six months to free up computer memory. Adequate warning will be given.

(a) Conventional Solid Samples

The standard method in the facility to firmly hold a large (1cm by 1cm) single sample to an ESCALAB sample holder is to spot weld across the four corners of the sample with thin Ta wire. The spot welds should be made on the side of the holder and not on the surface.

i) Always use four corners or edges

ii) Check that the sample is firmly held against the holder with no slippage. The wires should be

as far from the center of the sample as possible.

iii) Check for electrical continuity across sample and stub for conductive samples.

iv) When all samples have been mounted on stubs it is a good policy to deGauss them before

transferring the samples into the vacuum chamber.

Sometimes double sided "sticky" tape or conducting carbon paste can be used to mount samples to holders. However, these methods require an extended pump down of the samples in the load-lock and the chamber pressures never reach their base pressure.

There are also square shape sample holders with tapped holes on the corners. Samples can be fastened using screws and spring clips.

(b) Powder Samples

Many powder sample methods have been tested and a few are reviewed below:

i) Sprinkle powder on doublesided sticky carbon tape. Fast and simple, but causes sample charging. Use only with XPS.

ii) Press powder onto gold foil. Some sample charging. Strong gold signal may dominate weak sample peaks. Good method if samples need to be heated.

iii) Press powder into a pellet(disk) and mount on a sample stub with thicker edge. Good if samples not pressure sensitive.

iv) Press powder onto Indium foil. Good method for nearly all powders. Sticking coefficients for most powders to In is good and In can be used as an internal calibration standard.

1. Powder is sprinkled uniformly over one half of foil.

2. In foil folded in half with the powder in the middle using two-finger pressure. N.B. use gloves for cleanliness and safety since In is slightly poisonous if ingested.

3. The foil is folded back and cut into two pieces using a razor blade. The powder will divide at an uncontaminated internal surface.

4. One of the pieces of In foil is fixed to a sample stub using Ta wire.

(c) Generic Auger Sample Holder

High spatial resolution experimental techniques (unlike XPS) such as Auger Spectroscopy or SEM do not require large sample surface areas for analysis. However, the samples do need to be firmly held in place to minimize vibrations. Also, the sample should be in good electrical contact with the holder. See VG manual for more details.

(d) Fiber Sample Holder

To avoid collecting substrate counts, fiber samples can be strung between two clamps on a special sample holder. See VG manual for more details.