Adsorption of O2 and HF(O2) on Thermally Evaporated Tellurium Films PDF

Keywords

Condensed matter, electrical properties of thin films, surface status

Abstract

The room temperature variation of surface conductance of tellurium (Te) films with thickness has been studied. The measurements were performed in an atmosphere of oxygen (O2) or oxygen bubbled through hydrofluoric acid (HF(O2)). Tellurium films of thicknesses 500, 1000, 1500 and 2000A were deposited by thermal evaporation ata vacuum maintained at about 10-5 torr during the evaporation process. Some of the Te samples were annealed at 200 °C for 20 minutes. For the current (I)- voltage (V) measurements, the two-point probe configuration was adopted using aluminium (Al) electrodes. The surface conductance at zero bias was determined from the I-V data. The results reveal that the surface conductance of Te films is enhanced by the adsorption of O2, while the adsorption of HF(O2) reduces the surface conductance of the samples. The evaluated increase in surface conductance at zero bias, due to the adsorption of O2 ranges from 92% to 113% as the thickness of the films varied from 500 to 2000A. Also, the value of the reduction in surface conductance due to the adsorption of HF(O2) is between 27% and 33% as the thickness of the films varied from 500 to 2000A. The surface conductance of all the samples investigated increases exponentially with thickness. Finally, the surface conductance of as deposited Te films is higher than that of heat-treated Te samples.