Work Function Of Gold Research Articles

The work function of gold

The work function of gold films prepared by evaporation of spectrographically pure gold under ultra-high vacuum was determined. Two methods were used: (a) photoelectric emission, and (b) the retarding potential technique. For a fresh gold film deposited at a temperature of about 50 °C the work function was 5.30 eV. After sintering at 200 °C it increased to 5.38 eV. For a gold film deposited at higher temperature the work function was 5.45 eV. Oxygen gas does not bring about a measurable change in the work function of gold at room temperature.

The surface potential of oxygen on thorium

The contact potential difference between ultra-high vacuum-deposited films of gold and of thorium has been followed during the admission of oxygen at room temperature. With the knowledge that the work function of gold remains invariant in pressures of oxygen up to 10-3 torr and varies in a known fashion thereafter, the work function of the thorium film could be deduced under all conditions of coverage. Initial adsorption of oxygen produced a positive surface potential rising to a maximum of 0.47 ev, but continued adsorption under a constant rate of admittance caused a reversal to a negative surface potential after a long time. After reaching a minimum of -0.48 ev, the direction of change of the surface potential reversed abruptly and then rose steadily to a constant value of 0.48 ev, corresponding to a work function of 2.98 ev. The latter figure is within the range of values observed for ThO2. The results have been interpreted in terms of penetration of the surface layers of the thorium by oxygen, followed by transformation of the saturated layers to ThO2. It is suggested that the initial steps in the reaction between any electronegative element and a metal are penetration of the element into the metal followed by transformation of the surface layers into a new phase, the reaction product.

Work Function of Gold

The work functions of sixteen gold surfaces have been determined by measurement of their contact differences of potential with respect to barium reference surfaces of known work function. The gold surfaces were prepared by subjecting spectroscopic standard gold to repetitive fusion-solidification outgassing followed by fractional distillation and condensation on tantalum; the barium surfaces by a similar technique which yields surfaces reproducible and constant to 0.01 ev. Measurement was by the Kelvin method with a time interval of 15 seconds between deposition and measurement of a fresh surface.The contact difference of potential Au-Ba is found to be 2.31\ifmmode\pm\else\textpm\fi{}0.02 volts and the work function of gold 4.83\ifmmode\pm\else\textpm\fi{}0.02 ev, referred to a barium work function of 2.52 ev.