Reconsideration of Nanowire Growth Theory at Low Temperatures.

Vladimir G Dubrovskii

doi:10.3390/nano11092378

Abstract

We present a growth model that describes the nanowire length and radius versus time in the absence of evaporation or scattering of semiconductor atoms (group III atoms in the case of III-V NWs) from the substrate, nanowire sidewalls or catalyst nanoparticle. The model applies equally well to low-temperature metal-catalyzed or selective area growth of elemental or III-V nanowires on patterned substrates. Surface diffusion transport and radial growth on the nanowire sidewalls are carefully considered under the constraint of the total material balance, yielding some new effects. The nanowire growth process is shown to proceed in two steps. In the first step, the nanowire length increases linearly with time and is inversely proportional to the nanowire radius squared and the nanowire surface density, without radial growth. In the second step, the nanowire length obeys the Chini equation, resulting in a non-linear increase in length with time and radial growth. The nanowire radii converge to a stationary value in the large time limit, showing a kind of size-narrowing effect. The model fits the data on the growth kinetics of a single self-catalyzed GaAs nanowire on a Si substrate well.

Highlights

IntroductionHere we develop the NW growth theory in the absence of desorption of a semiconductor (Si or Ge) or group III (Ga or In) atoms from the substrate, NW sidewalls or catalyst nanoparticles, using the material balance for these atoms and considering their surface diffusion that contributes into the axial and radial growths
Theory at Low Temperatures.Semiconductor nanowires (NWs), III-V NWs, are widely considered as fundamental building blocks for nano-research and are useful for applications in nanoelectronics and nanophotonics [1]
These NWs are produced by different epitaxy techniques, including molecular beam epitaxy (MBE) and vapor phase epitaxy (VPE) via the metalcatalyzed vapor-liquid-solid (VLS) growth or catalyst-free selective area growth (SAG) [4]

Summary

Introduction

Here we develop the NW growth theory in the absence of desorption of a semiconductor (Si or Ge) or group III (Ga or In) atoms from the substrate, NW sidewalls or catalyst nanoparticles, using the material balance for these atoms and considering their surface diffusion that contributes into the axial and radial growths. The low-temperature NW growth considered here requires that no material is evaporated or scattered from different surfaces and that a finite diffusion length on the NW sidewalls is limited by surface evaporation causing the radial NW growth Whenever these conditions apply, the model can be used for growth modeling of II-VI, oxide or III-N NWs. The model geometry is illustrated in Figure 1 for SAG or metal-catalyzed NW growth.

Results and Discussion

Aspect

Conclusions