Vapor–liquid–solid silicon nanowires growth catalyzed by indium: study of indium oxide effect

In this work, we report on vapor–liquid–solid growth of silicon nanowires (SiNWs) catalyzed by indium, a low-eutectic post-transition metal. The indium catalyst is synthesized ex situ by annealing indium-coated substrates using two different annealing processes: rapid thermal annealing (RTA) and conventional process. The effect of annealing parameters on indium catalyst properties is studied. We show that after conventional annealing at 600 °C during 45 min, the indium layer is cracked into elongated and inhomogeneous islands of different sizes. X-ray diffraction (XRD) analysis depicts in addition to pure indium planes the presence of new peaks attributed to indium oxide planes formed during annealing. While by using RTA process, oxide-free indium particles were successfully grown in one step by during short time (5 min) at 400 and 450 °C. Quasi-spherical and homogeneously distributed indium particles were obtained at 450 °C. A comparative study between SiNWs catalyzed by indium catalyst prepared following the two different processes was carried out. The indium oxide presence negatively affected the catalytic property of indium, resulting in a lower density of the grown SiNWs. An improvement of the SiNWs density was achieved with RTA-annealed catalyst, as more indium particles were present to act as active catalyst to the growth. The catalyst annealing conditions also affected the size of the SiNWs, with shorter wires with RTA process. However, the shape of the SiNWs was similar in both studied cases, where the wires were bent and kinked. The morphology investigation of the SiNWs also shows that the SiNWs have a core–shell structures consisting of amorphous and crystalline silicon.