**2. VLS process**

The bottom-up approach is presented as an interesting alternative for lowcost nanowires growth. Indeed, it requires few technological steps with the possibility of SiNWs' growth on any substrate. Several techniques have been reported, mainly chemical vapor deposition (CVD), plasma-assisted chemical vapor deposition (PECVD), laser ablation, and molecular beam epitaxy (MBE). PECVD is the technique adopted in this work. It has the same principle as the conventional CVD except that the chemical reactions will take place after the formation of plasma from the reactor gases, offering the possibility to work at low temperatures. The deposited layers' properties strongly depend on the substrate temperature, the pressure, the growth time, the reactive gases, and the gas flow rates. The principle of SiNWs' growth by PECVD can be resumed in four main steps:


The SiNWs' growth is generally explained by the vapor–liquid–solid (VLS) mode proposed by R. S. Wagner and W. C. Ellis. In this mode, the growth depends on three main elements: the precursor in its gaseous state, and the metal-silicon

*Investigation of Indium Oxide Effect on Indium Particles Properties Used as Silicon Nanowires… DOI: http://dx.doi.org/10.5772/intechopen.93648*

alloy in the liquid state, the nanowire in the solid state, and hence the nomination vapor–liquid–solid mode.

The SiNWs' growth in a PECVD reactor is carried out by following the next steps:


$$\text{Si}H\_4 \rightarrow \text{Si} + 2H\_2 \tag{1}$$

• Incorporation of Si atoms in the droplet, formation of the metal-Si alloy, and the silicon diffusion toward the alloy-substrate interface. The silicon concentration in the droplet will exceed the equilibrium concentration at the working temperature, leading to the droplet saturation and the silicon nucleation.
