Ge/Si core/shell nanowires are fabricated with narrow (20 nm) Ge core and thin (2 nm) Si shell. Ge nanowires are prepared by vapor–liquid–solid (VLS) chemical vapor deposition (CVD). The low‐temperature (450 °C) process by using Si2H6 gas as a Si CVD source is essential to form ultrathin layer of epitaxial Si film onto very narrow Ge nanowires. Accumulation of holes in Ge nanowires confined in the Si shell is confirmed by electrical measurement.

Germanium/silicon core/shell nanowires (Ge/Si NWs) are expected to exceed the properties of single‐element Ge and Si nanowires as 1D structure materials. This is due to the valence band offset between Ge and Si at the heterostructure interface that serves as a confinement potential for the quantum well. In their work presented on pp. http://doi.wiley.com/10.1002/pssa.201532340, Noguchi et al. synthesized Ge/Si NWs with controlled thickness of Si shell in a low‐pressure chemical vapor deposition reactor (LPCVD) using gold nanoparticles as catalyst. The Ge NWs were first grown at low temperature (280 °C), followed by in situ deposition of Si shell at 450 °C. The Si shell was deposited epitaxially at the Ge NW core sidewalls. The nanowires have a core diameter of 20 nm and a shell thickness of 2 nm. A low deposition temperature is essential for the formation of thin Si shell. The authors also fabricated devices to measure the electrical and thermal properties of the Ge/Si NWs. The obtained results indicate the potential of Ge/Si NWs for thermoelectric devices.