Piezoelectric driven Kelvin probe for contact potential difference studies

Abstract

A convenient piezoelectric driven Kelvin probe for the measurement of work function changes is described. The probe has a simple construction, is small, bakeable, and can be mounted on any 35-mm-i.d. UHV flange. As the piezoelectric device is inside the vacuum chamber, only one electrical feedthrough is needed for operating the probe. The distance between reference electrode and sample can be varied within ±0.5 mm simply by applying a dc voltage to the piezoelectric device in addition to the ac oscillator-driving voltage, not requiring any mechanical driving and feedthrough provisions. The probe was tested studying the adsorption of O2 on Pt(111). The sensitivity for contact potential measurements is better than 0.1 mV at a response time of 10 sec.

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2-Based Nanomaterials

“…Thus, for example, the ionization energy of the semiconductor (IE S , defined as the energy needed to excite an electron from the valence band edge at the surface to the local vacuum level) can be measured by photoemission spectroscopy (e.g., UPS) [176]. On the other hand, the Kelvin probe method can be used for determination of the contact potential difference (CPD), that is, of the difference between the work function of a semiconductor and the work function of the metal tip of the probe (with known position on the energy vacuum scale) [177]. Moreover, the latter technique can be combined with illumination in the so-called surface photovoltage spectroscopy in which the changes of the CPD (i.e., of surface voltage) upon illumination are measured [178,179].…”

Surface photovoltage phenomena: theory, experiment, and applications

“…Both the former [142] and the latter [143] approaches are still employed in modern day high performance Kelvin probes. However, it is the piezoelectric drive technique, ®rst suggested by Besocke and Berger [144], which is currently most commonly used. In this approach, the vibrating electrode is mounted on an oscillator reed, which is fastened at the other end to a piezoelectric ceramic.…”

Properties of Carbon Nanotubes: Defects, Adsorbates, and Gas Sensing

“…While it is well known that the work function of metals can be modulated by annealing in a forming gas (indeed, this is a well utilized procedure in semiconductor manufacturing facilities to assist with barrier tuning), work functions have also been shown to change in the presence of various gas species [52]. Since it is possible for CNTs to have very narrow band gaps (many on the order of 0.25 eV), even slight changes in work function could result in a large impact on the threshold voltage.…”