  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 indicate that the transformation results
in a germanate polycrystalline layer consisting of germanium oxide and ammonium
fluogermanate with a preferential crystal growth orientation in <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 a yellow photoluminescence at room
temperature.
