Growth Kinetics of Planar Nanowires
- PDF / 454,230 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 77 Downloads / 232 Views
Kinetics of Planar Nanowires V. G. Dubrovskiia* and I. V. Shtromb a
St. Petersburg National Research University of Information Technologies, Mechanics, and Optics (ITMO University), St. Petersburg, 197101 Russia b St. Petersburg State University, St. Petersburg, 199034 Russia *e-mail: [email protected] Received June 30, 2020; revised July 14, 2020; accepted July 15, 2020
Abstract—An approximate analytic equation is derived that describes the law of elongation of a semiconductor nanowire (NW) growing via the vapor–liquid–solid (VLS) mechanism in a substrate plane. Various growth regimes are theoretically analyzed as dependent on NW radius R and epitaxial deposition conditions. It is established that the growth rate of planar NWs can be controlled either by the Gibbs–Thomson effect (in the case of small catalyst droplet dimensions) or by the diffusion of adatoms from the substrate surface (for increasing radius of the crystal). Dependence of the diffusion-controlled growth rate on radius R obeys the R–m law, where the power exponent takes the values of 1, 3/2, or 2 depending on the character of surface diffusion. Keywords: planar nanowire, vapor–liquid–solid growth mechanism, surface diffusion, Gibbs–Thomson effect. DOI: 10.1134/S1063785020100223
Whisker nanocrystals (nanowires, NWs) of semiconductor compounds offer promising “structural blocks” for fundamental investigations and applied research in the fields of nanoelectronics and nanophotonics [1]. Vertical NWs growing in the 111 direction perpendicular to the substrate surface can be synthesized by various epitaxial methods according to the vapor–liquid–solid (VLS) mechanism [2] with the aid of catalysts such as gold (Au) [2] or Group III metals (e.g., for autocatalytic VLS growth of GaAs nanowires) [3]. The kinetic theory of semiconductor NWs— in particular, of III–V compound NWs—has been rather thoroughly developed (see, e.g., review [4]). Practical applications of NW-based nanoheterostructures, including those compatible with silicon electronic technology, are sometimes complicated by their vertical geometry leading to difficulties in manufacturing upper contacts and some other problems. In this respect, planar NWs grown on the substrate surface can be of considerable interest [5–12]. Semiconductor material systems in which planar NWs have been synthesized on various surfaces include Si [5], III–V compounds [6, 7], group III nitrides (III-N) [8], II–VI compounds [9–11], and oxides [12]. There were attempts [11, 13, 14] at generalizing well-known models formulated in the theory of vertical NW growth to the case of planar growth. The aim of the present work is to derive and analyze a kinetic equation for the growth rate of planar NWs with allowance for the Gibbs–Thomson effect in a liq-
uid drop [15] and various mechanisms of adatom diffusion [16, 17]. Consider the process of planar NW growth on the surface of a planar substrate (Fig. 1). Let the NW have the form of a half-cylinder of radius R lying on the substrate surface, and let a drop occurring
Data Loading...
