XPS: PHI VersaProbe 4
The newest addition to SNSF's Surface Analysis Lab is the VersaProbe 4 XPS (Physical Electronics, Inc.). The VersaProbe 4 combines the most popular features of the VersaProbe 3 with improved sensitivity and additional capabilities.
Additional VP4 Capabilities:
- 2" Transfer Vessel: For samples needing air-free transfer, the VP4 can accommodate the 2" platen in the transfer vessel for analysis of more samples in one session.
- Double-window Intro chamber: An ex-situ camera is mounted over a second window so a top-down photo is possible while using the transfer vessel.
- 4-contact Heating/Cooling Stage: In-situ heating/cooling experimentation is possible through a temperature range of -120oC to 500oC. Specialized sample holder has 4 contact points connected through stage control for in-situ electrochemical experimentation.
- Gas Cluster Sputtering with Cluster Size Measurement tool: Advanced Gas Cluster Ion Beam Gun (GCIB) has the ability to tune Ar+ cluster size and therefore milling rate for specific applications.
- Reflection Electron Energy Loss Spectroscopy (REELS): The reflected electron energy loss spectrum can reveal details about excited atomic states, valence band transitions, and material bandgap. This technique is used to measure bandgap, detect hydrogen content, and distinguish sp2/sp3 carbon bonds.
- Ultraviolet Photoelectron Spectroscopy (UPS): He I or He II photons are used to produce a spectrum that can reveal the ionization energy and highest occupied molecular orbital (HOMO) of a material.
- Low Energy Inverse Photoelectron Spectroscopy (LEIPS): LEIPS provides the lowest unoccupied molecular orbital (LUMO) from which electron affinity can be determined. UPS and LEIPS in combination can provide important information about the valence band structure of semiconductor materials.
Basic XPS Capabilities:
- Detection limits (all elements except H and He): ~ 0.01 monolayer, or ~ 0.1% bulk
- Measurement depth: 10 - 50 Å;
- Spot sizes: 10um - 200 um or 1400 um x 100 um with High Power setting.
- Sample size: Samples must fit a 1" or 2" diameter platen; max 5 mm thick.
- Spectrometer: Monochromatized Al(Kα) Source; Vacuum ~ 1.2x10E(-7) Pa
XPS Background Info: There are numerous texts discussing the use of XPS. Some useful examples are:
- Electron Spectroscopy: Theory, Techniques and Applications. C. R. Brundle and A. D. Baker, eds. (a 5 volume series)
- Practical Surface Analysis, D. Briggs and M. P. Seah eds.
- Handbook of XPS, C. D. Wagner (published by Physical Electronics, Inc.)
- Or try http://www.york.ac.uk/org/esca/tech/xps.html.