Photoemission characterization of the H2 plasma-etched surface of CdS

Abstract

The effects of H2 plasma exposure of CdS as a function of substrate temperature was studied by synchrotron radiation soft x-ray photoemission spectroscopy and optical emission spectroscopy. The low-power H2 plasma was generated with a commercial electron cyclotron resonance plasma source using pure H2 with the plasma exposure being performed at ambient temperatures of 100 and 200°C. Plasma species were identified with optical emission spectroscopy. In situ photoemission measurements were acquired after each plasma exposure in order to observe changes in the valence-band electronic structure as well as changes in the Cd 4d and S 2p core lines. The results were correlated in order to relate the plasma species and characteristics to changes in surface chemistry and electronic structure. These measurements indicate that the H2 plasma exposure type converts the CdS surface to an n-type surface and that the magnitude of the band bending is dependent on substrate temperature during plasma exposure.