Evolution of Cu-In Catalyst Nanoparticles under Hydrogen Plasma Treatment and Silicon Nanowire Growth Conditions

• Published in: Nanomaterials (Basel, Switzerland) Vol. 13; no. 14; p. 2061
• Main Authors: Wang, Weixi, Ngo, Éric, Bulkin, Pavel, Zhang, Zhengyu, Foldyna, Martin, Roca I Cabarrocas, Pere, Johnson, Erik V, Maurice, Jean-Luc
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12-07-2023; MDPI
• Subjects: Bimetals; Carbon; Catalysts; Chemical synthesis; Coalescence; Copper; Cores; Cu-In nanoparticle; Diamonds; Engineering Sciences; Evaluation; Gold; Growth conditions; Hydrogen; Hydrogen plasma; Nanoparticles; Nanotechnology; Nanowires; PECVD; Phase transitions; Photovoltaic cells; Physics; Plasma; Plasma enhanced chemical vapor deposition; Plasma physics; plasma treatment; Silanes; Silicon; silicon nanowire; TEM; Transmission electron microscopy; Vapors; France; United States > US; silicon nanowire; plasma treatment; PECVD; Cu-In nanoparticle; TEM
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano13142061

We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 °C and the SiNW growth itself in a hydrogen-silane plasma at 420 °C. We show that the H
-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 °C induces a phase transformation of the catalyst cores to Cu
In
; while a hydrogen plasma treatment at 420 °C without silane can lead to the formation of the Cu
In
phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid-solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs-below 10 nm-among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap.