Schottky contacts in germanium nanowire network devices synthesized from nickel seeds

• Ge nanowires were grown by VLS method using Ni as catalysts.
• All nanowires presented reduced diameters and high single crystalline quality.
• The small size of the nanowires led to phonon localization effect.
• Temperature dependent Schottky barriers were observed on GeNWs network devices.

This paper presents reliable process to the synthesis of germanium nanowires by the vapor–liquid–solid method using nickel as an alternative catalyst to gold, the most commonly used metal, without toxic gas precursors. The structural study showed single-crystalline germanium nanowires with diamond structure, lengths of tens of microns and diameters smaller than 40 nm. The reduced dimensions of the nanowires led to phonons localization effect, with correlation lengths of the same order of the nanowires diameters. Additionally, the analysis of electronic properties of metal-nanowire-metal devices indicated the presence of Schottky barriers, whose values depend linearly on temperature. This linear dependence was assigned to the tunneling process through an insulator layer (mostly GeOx) at the metal-semiconductor interface. These results point to the existence of another channel for electrons transference from metal to semiconductor being very significant to electronic devices fabrication.