AUTOMATED REED-TYPE KELVIN PROBE FOR WORK FUNCTION AND SURFACE PHOTOVOLTAGE STUDIES

This paper reports the design of a compact, inexpensive, and ultrahigh vacuum compatible reed-type Kelvin probe for work function and surfac e photovoltage spectroscopy (SPS) studies. A simple method of controll ing the vibration amplitude of the probe is proposed which reduces mec hanical instabilities of the vibrating capacitor, leading to an autono mous and reliable probe for monitoring work function changes over a pr olonged period of time. A boss-type reference gold electrode is used t o simultaneously study the work function changes with adsorbents and S PS on real surfaces of semiconductors. A current preamplifier used in the measuring circuit reduces the effect of parasitic input capacitanc e and facilitates the application of a biasing voltage. A feedback loo p system and off-null technique are used for obtaining the contact pot ential difference. With this improved design of the probe setup a sens itivity of better than 0.1 mV has been achieved. Some experimental res ults are presented to show the performance of the setup. (C) 1996 Amer ican Institute of Physics.