Controlling Heterojunction Abruptness in VLS-Grown Semiconductor Nanowires via in situ Catalyst Alloying

Abstract

For advanced device applications, increasing the compositional abruptness of axial heterostructured and modulation doped nanowires is critical for optimizing performance. For nanowires grown from metal catalysts, the transition region width is dictated by the solute solubility within the catalyst. For example, as a result of the relatively high solubility of Si and Ge in liquid Au for vapor-liquid-solid (VLS) grown nanowires, the transition region width between an axial Si-Ge heterojunction is typically on the order of the nanowire diameter. When the solute solubility in the catalyst is lowered, the heterojunction width can be made sharper. Here we show for the first time the systematic increase in interface sharpness between axial Ge-Si heterojunction nanowires grown by the VLS growth method using a Au-Ga alloy catalyst. Through in situ tailoring of the catalyst composition using trimethylgallium, the Ge-Si heterojunction width is systematically controlled by tuning the semiconductor solubility within a metal Au-Ga alloy catalyst. The present approach of alloying to control solute solubilities in the liquid catalyst may be extended to increasing the sharpness of axial dopant profiles, for example, in Si-Ge pn-heterojunction nanowires which is important for such applications as nanowire tunnel field effect transistors or in Si pn-junction nanowires.

3D Silver Nanoparticles Decorated Zinc Oxide/Silicon Heterostructured Nanomace Arrays as High-Performance Surface-Enhanced Raman Scattering Substrates

“…Upon supersaturation of the liquid, the SiH x precipitated at the liquid−substrate interface, and the nanoneedles grew in a layerby-layer process. 45 As expected, the Si nanoneedles were successfully prepared on the surface of ZnO nanorods by PECVD. In our experimental conditions, the size of Au−Si droplet gets smaller and smaller owing to the loss and shrinkage that leads to gradual tapering nanoneedles taking place.…”

Step-Flow Kinetics Model for the Vapor–Solid–Solid Si Nanowires Growth

“…Unfortunately, plenty of experiments had shown that the liquid alloy catalysts were fundamentally unable to form the atomically abrupt interfaces, especially for group IV nanowires (Si/Ge). 7,8 This is because the high solubility of growth species in the liquid alloy (for example, Si and Ge in Au−Si or Au−Ge catalyst droplet) result in a "reservoir effect" that creates a composition gradient at the heterostructure interfaces when switching between grown materials. 9,10 There was an alternative approach to reduce the reservoir effect by using the solid catalyst instead of liquid alloy droplet, which was called vapor−solid−solid (VSS) growth.…”

Formation of gold and silver cluster arrays using vacuum-thermal evaporation on a non-heated substrate

“…Arrays of nanometer-sized clusters attract the interest of researchers due to the wide range of possible applications of such structures. In particular, the metal nanoparticles are used as a catalyst for growth of carbon nanotubes [1][2][3], nanowires of silicon and other semiconductors [4][5][6][7][8], as a catalyst for various chemical processes [9,10], in spectroscopy of surface enhanced Raman scattering [11,12], for medical purposes [13,14], in memory cells [15][16][17], in antireflection coatings of solar energy converters [18][19][20], in photonics and plasmonics [21][22][23].…”