Transformation of germanium to fluogermanates

The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO3 chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in aOE (c) 101 > direction. Local vibrational mode analysis confirms the presence of N-H and Ge-F vibrational modes in addition to Ge-O stretching modes. Energy dispersive studies reveal the presence of hexagonal alpha-phase GeO2 crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow photoluminescence at room temperature

Formation of germanates on germanium by chemical vapor treatment

The surface of a single crystal Germanium wafer was transformed to fluoride and oxide crystals upon exposure to a vapor of HF and HNO3 chemical mixture. Ellipsometry. X-ray, SEM and photoluminescence were used to investigate the physical properties of the resultant surface structure The analysis indicates that the transformation results in a polycrystalline hexagonal ammonium fluogermanates and a hexagonal alpha-Germanium oxide Clusters with a preferential crystal growth orientation in direction The fluogermanates grow particularly around the germanium oxide Clusters as evidenced by electron dispersive spectroscopy profiling Local vibrational mode analysis confirm the presence of N-H and Ge-F vibrational modes of NH4+ and GeF6- ions. The vibrational modes at around 840 cm(-1) is significative of GeOx stretching bands originating from the partial coverage surface oxide formed together with the fluogermanates and clusters oil the Germanium Electronic band structure as probed by ellipsometry is typical of Ge and any discrepancy was associated with disorder induced band tailing effects originating possibly from the effect of oxide clustering

Experimental and theoretical study of the thermal solubility of the vacancy in germanium

Quenching experiments are performed using state of the art p-type Czochralski-grown Ge samples. The vacancy formation energy and thermal equilibrium concentration are determined on the basis of resistivity changes measured after quenching, using van der Pauw and Hall measurements. The results are compared with previously published experimental data and with results from analytical and ab initio calculations of the formation energy of the vacancy in different charge states. The deep levels introduced during the quenching step are studied with deep level transient spectroscopy and with FTIR, revealing besides the typical quenching related defects which are probably connected with vacancies also the presence of Cu