Low-Temperature and High-Speed Fabrication of Nanocrystalline Ge Films on Cu Substrates Using Sub-Torr-Pressure Plasma Sputtering

Abstract

We fabricated nanocrystalline Ge films using radio-frequency (RF) magnetron plasma sputtering deposition under a high Ar-gas pressure. The Ge nanograins changed from amorphous to crystalline when the distance between the Ge sputtering target and the substrate was decreased to 5 mm and the RF input power was 11.8 W/cm 2 (60 W), where the deposition rate was as high as 660 nm/min. In addition, the size of the nanocrystalline grains increased from 100 to 307 nm when the RF input power for plasma production was increased from 11.8 W/cm 2 (60 W) to 17.7 W/cm 2 (90 W). In the developed narrow-gap plasma process at sub-Torr pressures, nanocrystalline Ge films were successfully fabricated on Cu substrates at low temperatures, without the substrate being heated. However, when annealing was conducted under an N2 atmosphere, which is the conventional method to induce solid-phase crystallization, the amorphous Ge layer on a Cu substrate changed to a Cu3Ge crystal layer through interdiffusion of Ge and Cu atoms at 400-500 °C.

Fabrication of amorphous LiPON, LiAlGePO, and GeSn films in low-temperature plasma sputtering process for all-solid-state Li+-ion battery

“…[28][29][30][31] A large number of isolated nanoparticles and radical atoms as adhesive are simultaneously deposited on substrates without aggregation in the plasma process. 22,32,33) We have already successfully generated a dispersed arrangement of monodisperse nanograins without aggregation using an Ar high-pressure plasma process in the sub-Torr range. 34,35) In the present study, we used Ar highpressure sputtering to fabricate GeSn nanomaterials for Li + -ion battery anodes.…”