Long Germanium Nanowires Prepared by Electrochemical Etching

Abstract

Germanium (Ge) nanowires have been produced by electrochemical etching of single-crystalline n-type Ge [100] in a HCl-containing aqueous electrolyte. Macropores could be etched at various etching currents after an optimized procedure for homogeneous pore nucleation was used. Because of the narrow band gap of Ge (0.66 eV), the leakage current through pore walls is much higher than that, for example, in Si, leading to a constant dissolution of the pore walls. At sufficiently high current densities, it is then possible to form nanowires with diameters determined by the width of the space charge region, ranging from roughly 50 to 500 nm, and a length of several hundred micrometers. The role of the space charge region for stabilizing pore formation and in the formation of nanowires will be discussed.

Electrochemical pore formation onto semiconductor surfaces

“…Similarly Ge [17], Si 1Àx Ge x compounds and all polytypes of SiC can also be made porous using aqueous HF solutions [50,51]. However, square shaped pores and nanowires have recently been grown on Ge in aqueous HCl [145] and NH 4 F has been successfully used to porosify SiC [146,147].…”

Deep germanium etching using time multiplexed plasma etching

“…In addition, germanium is the common substrate to III-V materials' growth, thanks to its lattice match with GaAs enabling epitaxy of III-V materials on germanium for photonic and photovoltaic applications. The high aspect ratio germanium patterns have been formed using growth, 1 electrochemical etching, 2 and plasma etching, 3 the latter one being the most appropriate technique for local and defined patterns' formation.…”

Chemical route for Si/C coated germanium nanowires

“…Other procedures are vapor-solid-solid (VSS) synthesis [19], non-catalytic procedure [20,21], laser ablation [22,23], glancing angle deposition [24], modified surfactant mediated epitaxy [25], supercritical fluid-liquid-solid process [26,27], supercritical fluid-solid-solid synthesis [28], thermal evaporation [29], electrochemical etching [30]. Usually, starting precursor are very simple -elemental Ge [16][17][18] or germanes GeH 4 [2][3][4][5][6][7][8][9][10][11][12], GeI 4 [31], GeCl 4 [32] and Ge 2 H 6 * Corresponding author.…”