Catalytic Growth of CdS Nanowires by Microplasma-Prepared\nGold Nanoparticles

Integrating\nsemiconductor nanowires with silicon platforms can\ncombine the advantages of both materials to provide new functionality\ncompared with each type of material. However, the direct localized\ngrowth of semiconductor nanowires on silicon platforms still remains\na challenge. Herein, an atmospheric pressure microplasma jet, based\non the integration of microplasma with the 3D printing technique,\nwas applied for the synthesis of gold nanoparticles (AuNPs). The obtained\nAuNPs were then used as catalysts for the physical vapor deposition\n(PVD) growth of cadmium sulfide nanowires (CdS NWs). The results showed\nthat AuNPs can be directly fabricated on the surface of silicon wafers\nin one step without chemical reducing agents. They also demonstrated\ngood catalytic activity in the growth of CdS NWs via a typical vapor–liquid–solid\n(VLS) mechanism, where CdS NWs of straight sidewalls with a AuNP at\ntheir tips were formed. Complementary characterization reveals that\nCdS NWs possess crystalline structure, with the atomic ratio of Cd/S\nclose to 1:1 stoichiometry. The energy band gap was estimated to be\n2.5 eV from the photoluminescence spectrum. In addition, the influence\nof process parameters like the Au<sup>3+</sup> concentration and plasma\nprocessing time on the products was studied. Both increase of the\nAu<sup>3+</sup> concentration and plasma processing time led to the\nformation of high-density AuNPs and CdS NWs. With the rise of the\nAu<sup>3+</sup> concentration, the average diameter of the AuNPs gradually\nincreased from 13.17 nm at 0.02 mM to 17.0 nm at 0.05 mM and finally\n20.44 nm at 0.1 mM. This also led to the formation of CdS NWs of large\ndiameters. This work offers a simple, direct, and green way for localized\nfabrication of metal catalysts on target substrates for the growth\nof NWs and has unprecedented potential in various fields like catalysis,\nsurface modification, and additive manufacturing.