An In-Plane Solid-Liquid-Solid Growth Mode for Self-Avoiding Lateral Silicon Nanowires

We report an in-plane solid-liquid-solid (IPSLS) mode for obtaining self-avoiding lateral silicon nanowires (SiNW) in a reacting-gas-free annealing process, where the growth of SiNWs is guided by liquid indium drops that transform the surrounding $a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ matrix into crystalline SiNWs. The SiNWs can be $\sim \mathrm{mm}$ long, with the smallest diameter down to $\sim 22\mathrm{nm}$. A high growth rate of $>{10}^2\mathrm{nm}/\mathrm{s}$ and rich evolution dynamics are revealed in a real-time in situ scanning electron microscopy observation. A qualitative growth model is proposed to account for the major features of this IPSLS SiNW growth mode.

Figure 1

(a)–(d) the basic experimental procedure for the growth of IPSLS SiNWs; (e) illustrates the IPSLS growth mode of SiNW, with $J_{\mathrm{Si}}^{\mathrm{out}}$ ($J_{\mathrm{Si}}^{\mathrm{in}}$), $R_m$, $L_m$, $R_{\mathrm{SiNW}}$ and $H_a$, the flux of Si atoms from In drop to SiNW (from $a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ into In drop), the cross section and length of the In catalyst drop, the cross section of SiNW and the thickness of $a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ layer, respectively. (f) and (g) depict two possible situations for the actual absorbed $a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ thickness ($H_a^{*}$). (h) illustrates the origin of the drawing force at the imbalanced triple phase line due to continuous absorption at the $\mathrm{In}/a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ interface.

Figure 2

(a) A typical SEM image of the lateral SiNWs, (b) a side-view of a SiNW sitting in a trench structure in the $a\mathrm{\text{−}}\mathrm{Si}:\mathrm{H}$ matrix, and (c) one of the smallest lateral SiNWs.

Figure 3

(a) AFM image of a single SiNW with vertical scale from black to white of 160 nm, and (b) its corresponding crystalline Si Raman peak signal mapping (integrated in the spectral window $521\pm 5{\mathrm{cm}}^{-1}$). The inset in (a) shows the Raman spectrum recorded from the position marked with an $\mathit{x}$ in (b).

Figure 4

(a)–(f) a series of six frames captured in sequential order (with $t=0$, 1, 2, 4, 5, 47 s) in a real-time in situ SEM observation. A gradual squeezing of the In drop by the SiNW behind can be clearly witnessed in (a)–(d), followed by a quick restoration (d)–(e).

Figure 5

shows three SiNWs (A, B, and C) obtained on the same sample but with different morphologies.