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 surface photovoltage spectroscopy (SPS) studies. A simple method of controlling the vibration amplitude of the probe is proposed which reduces mechanical instabilities of the vibrating capacitor, leading to an autonomous and reliable probe for monitoring work function changes over a prolonged period of time. A boss-type reference gold electrode is used to simultaneously study the work function changes with adsorbents and SPS on real surfaces of semiconductors. A current preamplifier used in the measuring circuit reduces the effect of parasitic input capacitance and facilitates the application of a biasing voltage. A feedback loop system and off-null technique are used for obtaining the contact potential difference. With this improved design of the probe setup a sensitivity of better than 0.1 mV has been achieved. Some experimental results are presented to show the performance of the setup. (C) 1996 American Institute of Physics.