Gold-enhanced oxidation of MBE-grown silicon nanowires

Abstract

Thermal oxidation of MBE-grown silicon nanowires with a gold droplet on their tips was investigated. Two kinds of oxidation behavior were observed: (i) enhanced axial oxidation, if there was a direct contact between the gold droplet and the nanowire, and (ii) conventional oxidation for nanowires when there was no direct contact between the gold and silicon. For a dry atmosphere, such enhanced oxidation takes place at temperatures down to 500 • C. Under a wet atmosphere, remarkable oxidation was observed even for temperatures down to 250 • C. 2. Experiment Undoped single-crystalline 1 1 1 Si NWs were grown in a MBE chamber at a temperature of 525 • C and at a pressure

Rapid thermal oxidation of silicon nanowires

“…For example, recent investigations of dry furnace oxidation revealed reduced oxidation rate of SiNWs compared to planar Si and showed the dependence of oxidation rate on the NW diameter. 3,6,7 This behavior is in a qualitative agreement with a model by Kao et al 8 for the oxidation of cylindrical Si microstructures. However, in some cases, enhanced oxidation of SiNWs compared to Si wafers has been observed.…”

“…We expect that longer RTO treatments would result in further decrease in the growth rate as observed for conventional furnace oxidation. 3,6,7,9 A weaker dependence of oxide thickness on r c for 1000°C oxidation as compared to 900°C ͑Fig. 2͒ is also consistent with the model of Kao et al because 1000°C is higher than the viscous flow point for SiO 2 ͑Ϸ960°C͒ ͑Ref.…”

“…However, in some cases, enhanced oxidation of SiNWs compared to Si wafers has been observed. 3,7,9 In the present study, we analyzed the oxidation kinetics of SiNWs using rapid thermal oxidation ͑RTO͒. RTO offers several advantages over conventional furnace oxidation for planar silicon, including superior-quality gate oxide layers with low fixed-charge density, high breakdown dielectric field, and smooth Si/ SiO 2 interface.…”

Metal‐Assisted Chemical Etching of Silicon: A Review

“…That is, the Si atoms that are in contact with a noble metal are dissolved in the noble metal and then diffuse through the noble metal to the noble metal/solution interface where the silicon atoms are oxidized and etched away at the noble metal/solution interface (Model II, Figure 2). This mechanism would somehow be analogous to the well‐known phenomenon that a Si substrate covered with a noble metal (film or particle) is catalytically oxidized at low temperature, or even at room temperature, in oxygen or air 69–73. In this phenomenon, the back bonds of the Si atoms at the interface between the Si substrate and the noble metal are broken; the free Si atoms are dissolved into the noble metal, diffuse through the noble metal, and are thermally oxidized on the surface of the noble metal.…”

Lithography-free synthesis of freestanding gold nanoparticle arrays encapsulated within dielectric nanowires

“…[42][43][44][45][46] Unlike the thermal oxidation of Au-free Si, where Si-Si bond breaking controls the Si/SiO 2 interface reaction rate, 47 oxidation at the Au surface is more efficient due to a lowering of the activation energy and a corresponding increase in the reaction rate. The Au-enhanced oxidation occurs in three steps: 1) Si atoms migrate through the Au, 2) oxygen diffuses through SiO 2 film, and 3) Si atoms are oxidized at Au/SiO 2 interface.…”