Atomically Smooth p-Doped Silicon Nanowires Catalyzed by Aluminum at Low Temperature

Abstract

Silicon nanowires (SiNWs) are powerful nanotechnological building blocks. To date, a variety of metals have been used to synthesize high-density epitaxial SiNWs through metal-catalyzed vapor phase epitaxy. Understanding the impact of the catalyst on the intrinsic properties of SiNWs is critical for precise manipulation of the emerging SiNW-based devices. Here we demonstrate that SiNWs synthesized at low-temperature by ultrahigh vacuum chemical vapor deposition using Al as a catalyst present distinct morphological properties. In particular, these nanowires are atomically smooth in contrast to rough {112}-type sidewalls characteristic of the intensively investigated Au-catalyzed SiNWs. We show that the stabilizing effect of Al plays the key role in the observed nanowire surface morphology. In fact, unlike Au which induces (111) and (113) facets on the nanowire sidewall surface, Al revokes the reconstruction along the [112] direction leading to equivalent adjacent step edges and flat surfaces. Our finding sets the lower limit of the Al surface density on the nanowire sidewalls at ∼2 atom/nm(2). Additionally, despite using temperatures of ca. 110-170 K below the eutectic point, we found that the incorporation of Al into the growing nanowires is sufficient to induce an effective p-type doping of SiNWs. These results demonstrate that the catalyst plays a crucial role is shaping the structural and electrical properties of SiNWs.

Ga and In adsorption on Si(112): Adsorption sites and superstructure

“…In the present case, the number of noncollinear Fourier components (up to four) is rather high from an experimental point of view. However, from literature [16][17][18][19][20][21][22][23] and Assuming that, in a first approximation, both atomic chains are populated equally, the simple two-position model described above can be used. Applying Eq.…”

“…14,15 However, it has already been shown [16][17][18][19][20][21] that the adsorption of group-III elements on Si(112) induces surface smoothening. For Al/Si(112), Ga/Si(112), and In/Si(112), different structural models have been proposed.…”

“…For Al/Si(112), Ga/Si(112), and In/Si(112), different structural models have been proposed. [16][17][18][19][20][21][22][23] In all these models, the group-III metal atoms adsorb on so-called terrace sites and/or on so-called step-edge sites. Both the step-edge sites as well as the terrace sites are arranged in chains along the [110] direction.…”

“…29 Al adsorption leads to a (5×1) reconstruction at coverages well below one monolayer and a transition to a (6×1) reconstruction at around a monolayer. 16,21 Density functional theory (DFT) calculations suggest that Al occupies both the stepedge sites and the terrace sites. 22 Within this model, the chains along the step-edge sites are periodically interrupted by vacancies at every 5 th or 6 th site, whereas the chains along the terrace sites are continuously occupied with Al.…”

Fabrication and optical simulation of vertically aligned silicon nanowires

“…Currently, several methods have been reported to grow Si-NWs vertically, viz., chemical vapor deposition (CVD), nanoparticles-assisted etching, reactive-ion etching (RIE), etc. (Yi et al 2011;Krylyuk et al 2010;Moutanabbir et al 2011;Shin and Filler 2012;Zhong et al 2011;Chen et al 2010;Huang et al 2008;Geyer et al 2012;Yuan et al 2012;Chang et al 2012;Cho et al 2011;Sainiemi et al 2011;Garnett and Yang 2010;Zhu et al 2009). The SiNWs prepared by these methods exhibit promising photoelectron conversion characteristics.…”