We fabricated nanostructured Ge and GeSn films using He radio-frequency magnetron plasma sputtering deposition. Monodisperse amorphous Ge and GeSn nanoparticles of 30–40 nm size were arranged without aggregation by off-axis sputtering deposition in the high He-gas-pressure range of 0.1 Torr. The Ge film porosity was over 30%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge and GeSn anodes. The Ge anode with a dispersed arrangement of nanoparticles showed a Li-storage capacity of 565 mAh/g after the 60th cycle. The capacity retention was markedly improved by the addition of 3 at% Sn in Ge anode. The GeSn anode (3 at% Sn) achieved a higher capacity of 1128 mAh/g after 60 cycles with 92% capacity retention. Precise control of the nano-morphology and electrical characteristics by a single step procedure using low temperature plasma is effective for stable cycling of high-capacity Ge anodes.

We present a study on morphological control of nanostructured Ge films by the Ar gas pressure in plasma sputtering deposition. In the low Ar-gas-pressure range, aggregated islands of amorphous grains are formed on the film surface, while in the high-pressure range of 500 mTorr monodisperse nano-grains of about 30 nm in size are orderly arranged without aggregation. The film porosity shows a high value of over 10%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge films as anodes. The battery cell with an ordered arrangement structure maintained a high capacity of 434 mAh g−1 after 40 charge/discharge cycles, while that with an aggregated structure exhibited a rapid degradation of capacity to 5.08–183 mAh g−1. An ordered arrangement of Ge nano-grains with a high porosity, which is realized in a simple one-step procedure using high Ar-gas-pressure plasma sputtering, is effective for the stable cycling of high-capacity metal anodes.

Plasma-sputtered amorphous films for all-solid-state Li+-ion batteries are investigated. In LiPON electrolyte films, the amount of N incorporated into LiPO films is controlled by the sputtering discharge gas. Ionic conductivity increases with increasing N2 gas proportion in Ar/N2 discharge, reaching a maximum of 2.7 × 10−6 S/cm at Li2.39PO3.71N0.13. In amorphous LiAlGePO electrolyte films, the amounts of Al and Ge incorporated into LiPO films are controlled in a combinatorial approach using two-source co-sputtering. The P/Ge ratio varies over a wide range from 23.3 to 1.61 at the radial substrate positions, and the highest ionic conductivity of 4.32 × 10−5 S/cm is achieved at Li4.80Al0.80Ge1.16P3O13.1. We evaluate all-solid-state Li+-ion batteries fabricated using the developed amorphous LiPON electrolyte and GeSn anode films, where GeSn films with about 50 nm nanograins are fabricated by high-gas-pressure sputtering at 500 mTorr. A maximum capacity of 2.86 µAh/cm2 is attained for all-solid state Li+-ion battery.

We fabricated nanostructured Ge and GeSn films in He radio-frequency magnetron plasma sputtering deposition. Monodisperse amorphous Ge and GeSn nanoparticles of 30-40 nm in size were orderly arranged without aggregation by off-axis sputtering deposition in high He-gas-pressure range of 0.1 Torr. The Ge film porosity was over 30%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge and GeSn anodes. The Ge anode with an ordered arrangement of nanoparticles showed Li-storage capacity of 565 mAh/g after the 60th. The capacity retention was markedly improved by the addition of 3at% Sn in Ge anode. GeSn anode (3at% Sn) achieved a higher capacity of 1,128 mAh/g after 60th cycles with 92% capacity retention. Precise control of the nano-morphology and electrical characteristics by a single step procedure using low temperature plasma is effective for stable cycling of high-capacity Ge anodes.