Structure, Growth Kinetics, and Ledge Flow during Vapor−Solid−Solid Growth of Copper-Catalyzed Silicon Nanowires

Abstract

We use real-time observations of the growth of copper-catalyzed silicon nanowires to determine the nanowire growth mechanism directly and to quantify the growth kinetics of individual wires. Nanowires were grown in a transmission electron microscope using chemical vapor deposition on a copper-coated Si substrate. We show that the initial reaction is the formation of a silicide, eta'-Cu(3)Si, and that this solid silicide remains on the wire tips during growth so that growth is by the vapor-solid-solid mechanism. Individual wire directions and growth rates are related to the details of orientation relation and catalyst shape, leading to a rich morphology compared to vapor-liquid-solid grown nanowires. Furthermore, growth occurs by ledge propagation at the silicide/silicon interface, and the ledge propagation kinetics suggest that the solubility of precursor atoms in the catalyst is small, which is relevant to the fabrication of abrupt heterojunctions in nanowires.

Growth of Crystalline Copper Silicide Nanowires in High Yield within a High Boiling Point Solvent System

“…This shows that after the initial Cu source on the substrate has been consumed in the formation of Cu silicide nanocrystals, additional Si vapour supply results in the formation of pure, elemental Si NWs with well faceted Cu silicide tips (indicating a VSS NW growth mechanism). 26,44 When considering the growth mechanism for the Cu 15 Si 4 NWs in this report (depicted schematically Supporting Information Figure S10), there are noticeable parallels with the mechanisms proposed for the growth of the Ni silicide NWs. 31,32 There, the formation of Ni silicide crystallites was assumed to be a prerequisite for NW growth.…”

“…Similarly, previous reports using Cu as a seed for elemental Si NW formation have always led the formation of orthorhombic Cu 3 Si catalyst seeds from the initial Cu nanoparticles. [36][37][38] It thus seems likely that pure Si NWs would have been formed in this system had Cu 3 Si crystallites been formed on the Cu substrate rather than Cu 15 Si 4 crystallites. Therefore, the phase of silicide (or germanide) formed on the substrate plays an important role in determining whether pure Si (or Ge) NWs or silicide (germanide) NWs form.…”

Nanomaterial-Based Biosensor as an Emerging Tool for Biomedical Applications

“…22 At present, most SiNWs used in nanodevices are synthesized by vaporliquid-solid (VLS) and vapor-solid-solid (VSS) growth processes. 33,125,127 Usually, SiNWs fabricated using VLS or VSS techniques have well-defined surfaces and well-controlled diameters. These SiNWsrelated FETs are quite sensitive because SiNWs have a high carrier mobility and high surface-to-volume ratio which ensures that mass carriers can be controlled easily by applying a weak electrical field on the gate.…”

Concurrent Growth of Kirkendall Pores and Vapor–Solid–Solid Protuberances on Ni Wires During Mo Vapor-Phase Deposition

“…Researchers have recently demonstrated that nanowires and/or whiskers may grow below the eutectic temperature without the presence of liquid phases in a vaporsolid-solid (VSS) mechanism which is explained by the size-dependent eutectic temperature depression hypothesis [19,20] or by the formation of catalyzing intermetallic phases. [21][22][23][24][25] However, prevailing studies on both VLS and VSS are mostly addressing nanowire and/or whiskers growth at the sub-micron and nanometric scale. We are not aware of reports on VLS or VSS features with supra-micron scales, as described in the present study.…”