Abstract
In this study, we report on the formation of a single-crystalline Ni 2 Ge/Ge/Ni 2 Ge nanowire heterostructure and its field effect characteristics by controlled reaction between a supercritical fluid-liquid-solid (SFLS) synthesized Ge nanowire and Ni metal contacts. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal a wide temperature range to convert the Ge nanowire to single-crystalline Ni 2 Ge by a thermal diffusion process. The maximum current density of the fully germanide Ni 2 Ge nanowires exceeds 3.5 × 10 7 A cm -2 , and the resistivity is about 88 μΩ cm. The in situ reaction examined by TEM shows atomically sharp interfaces for the Ni 2 Ge/Ge/Ni 2 Ge heterostructure. The interface epitaxial relationships are determined to be Ge[011̄] || Ni 2 Ge[01̄1] and Ge(11̄1̄) || Ni 2 Ge(100). Back-gate field effect transistors (FETs) were also fabricated using this low resistivity Ni 2 Ge as source/drain contacts. Electrical measurements show a good p-type FET behavior with an on/off ratio over 10 3 and a one order of magnitude improvement in hole mobility from that of SFLS-synthesized Ge nanowire. © 2010 IOP Publishing Ltd.