Chemical Vapor Deposition Growth of Silicon Nanowires with Diameter Smaller Than 5 nm

Abstract

Quantum confinement effects in silicon nanowires (SiNWs) are expected when their diameter is less than the size of the free exciton (with a Bohr radius ∼5 nm) in bulk silicon. However, their synthesis represents a considerable technological challenge. The vapor–liquid–solid (VLS) mechanism, mediated by metallic nanoclusters brought to the eutectic liquid state, is most widely used for its simplicity and control on the SiNWs size, shape, orientation, density, and surface smoothness. VLS growth is often performed within high-vacuum physical vapor deposition systems, where the eutectic composition and the pressure conditions define the minimum diameter of the final nanowire usually around 100 nm. In this article, we present and discuss the SiNWs’ growth by the VLS method in a plasma-based chemical vapor deposition system, working in the mTorr pressure range. The purpose is to demonstrate that it is possible to obtain nanostructures with sizes well beyond the observed limit by modulating the deposition parameters, like chamber pressure and plasma power, to find the proper thermodynamic conditions for nucleation. The formation of SiNWs with sub-5 nm diameter is demonstrated.

Synthesis, Characterization, and Analysis of Hybrid Carbon Nanotubes by Chemical Vapor Deposition: Application for Aluminum Removal

“…CNTs are grown using several methods, such as arc discharge, laser ablation, and chemical vapor deposition (CVD). CVD technique is more effective as it is a cost-effective technique and provides high-purity material under controlled growth conditions [ 18 ].…”

Silicon Nanowires Synthesis by Metal-Assisted Chemical Etching: A Review

“…Another advantage is the possibility to obtain Si NWs with a diameter down to about 10 nm as shown by Lieber’s group [ 5 ] and even below this limit. Recently, Puglisi et al demonstrated the realization of Si NWs with a diameter under 10 nm by varying the plasma power and the gas pressure in a VLS process realized by a plasma enhanced chemical vapor deposition [ 40 ]. However, their synthesis is still complex and the Si NWs showed in these papers have different orientations making more complex their implementation for real applications.…”

“…However, their synthesis is still complex and the Si NWs showed in these papers have different orientations making more complex their implementation for real applications. Hence, even if it is possible to reach less than 10 nanometer in diameter, it leads to a lack of orientation control of the Si NW growth [ 40 , 41 ].…”

Room Temperature Growth of Silica Nanowires on Top of Ultrathin Si Nanowires Synthesized with Sn‐Cu Bimetallic Seeds

“…Developing quantum size Si nanowires (SiNWs) is of interest for different optoelectronic and photovoltaic applications. [1][2][3][4] Si nanowires with a diameter below 10 nm have a bandgap that increases as their diameter decreases. [5] Interestingly, they can also adopt the metastable hexagonal diamond crystalline structure, [6] the calculated electronic structure of which would have specific and interesting opto-electronic properties (increased absorption).…”

“…Some authors have achieved the synthesis of small diameter SiNWs, using well-defined gold nanoclusters as catalysts in a vapor-liquid-solid (VLS) growth process or in a supercritical hexane solution phase. [3,[8][9][10] However, these methods deliver a small fraction of NWs with sufficiently small diameters. Moreover, the use of gold brings undesirable impurities.…”