**2.1 Growth of Si NW**

Si NWs were prepared by vapor-liquid-solid (VLS) method by using chemical vapor deposition (CVD) with a silane gas. The obtained Si NWs is shown in **Figure 1**. The main steps of the VLS growth can be summarized as follows:


Before starting the growth, the Si substrate [the (111)] is immersed in a dilute HF solution (2%) to remove the native oxide. Subsequently, we evaporate 2 nm thick Au film or drop cast a gold nanoparticle on the Si surface. The gold nanoparticles can control the diameter of the Si NWs. The substrate is annealed

**Figure 1.** *SEM image of VLS-grown Si NWs with lengths of 3 ± 1 μm and diameters of 60 ± 10 nm.*

*Heterojunction-Based Hybrid Silicon Nanowires Solar Cell DOI: http://dx.doi.org/10.5772/intechopen.84794*

#### **Figure 2.**

*The chlorination/alkylation system. In Figure 4, different reactions are carried in the same time.*

under vacuum at the CVD chamber to 580°C for 10 min. The temperature was then reduced to 520°C, and a mixture of 10:5 sccm (standard cm3 min<sup>−</sup><sup>1</sup> ) of Ar:SiH4 was introduced for 20 min at a pressure of 0.5–2 mbar. The growth time can basically control the final length of the Si NWs (see **Figure 1**).

The VLS-grown Si NW can be with lengths from 1 to 20 μm and diameters of 10–100 nm [33]. As shown in the SEM image, the Si NWs were grown in random orientations.
