Nanoporous Helium–Silicon Co‐Deposition Thin Film via Plasma‐Assisted Process for Lithium‐Ion‐Battery Anodes

In this study, silicon (Si) deposition is performed in a high‐density (10 18 m −3 ) helium (He) plasma environment, and He–Si co‐deposition layers, where He atoms are implanted into the Si thin film, are formed. The He‐containing thin film, which has a porosity of ≈0.5, is composed of smaller clusters with the size of 100–200 nm including many pores with different sizes, which is advantageous for lithium‐ion‐battery (LIB) negative electrode. It is also shown that substrate copper (Cu) atoms are diffused into the deposition layer and Cu doping occurred naturally. The LIB performance of the He–Si co‐deposited thin film (>1 μm in thickness) is evaluated. When the substrate temperature is at 523 K during the deposition, the Si layer has amorphous structure, and the LIB discharge capacity remains 1800 mAh g −1 after 100 cycles. In the results, it is shown that the Si–He co‐deposition method can be a novel method to fabricate Cu‐doped porous amorphous Si thin film for high‐performance LIB application.