• 
  Stegemann, B.; Schoepke, A.; Sixtensson, D.; Gorka, B.; Lussky, T.; Schmidt, M.: Hydrogen passivation of interfacial gap state defects at UHV prepared ultrathin SiO₂ layers on Si(111), Si(110), and Si(100). Physica E 41 (2009), p. 1019-1024

10.1016/j.physe.2008.08.012

Abstract:
A complete in situ process from preparation and hydrogen passivation to interface gap state analysis by near-UV photoelectron spectroscopy (NUV-PES) without breaking ultrahigh vacuum (UHV) conditions is applied to ultrathin oxide layers on Si(111), (110), and (100). RF plasma oxidation with thermalized neutral oxygen atoms allows the growth of homogeneous ultrathin SiO2 layers (< 2 nm) and the preparation of compositionally and structurally abrupt Si/SiO2 interfaces with minimal amounts of suboxides ranging from 2% on Si(100) to 4% on Si(110). The oxide growth is independent of the crystallographic orientation. Appropriate plasma treatment with nearly thermalized hydrogen atoms (Ekin < 1 eV) leads to significant passivation of dangling bonds at the ultrathin-SiO2/Si interfaces and is most efficient on Si(100). In contrast, energetic hydrogen plasma treatment of these interfaces with kinetic energies exceeding 120 eV, which is conventionally applied for polycrystalline Si thin film solar cells, imparts large amounts of energy and deteriorates the electrical properties as is reflected in interface degradation and increased densities of defect states.