Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA.
J Chem Phys. 2009 Dec 14;131(22):224702. doi: 10.1063/1.3246169.
Vapor-phase mechanisms [e.g., vapor-liquid-solid (VLS), vapor-solid-solid, oxide-assisted growth, and the self-catalytic growth mechanisms] for the unidirectional nanowire (NW) growth are not yet well understood. For this understanding, growths of GaN and InN NWs in our laboratory, without and with the assistance of foreign element catalytic agents (FECAs), such as Au and In, were performed. GaN NW growth, in the presence of FECA identical withNi, was possible at temperatures below the Ni/Ga eutectic temperature. InN NWs were grown, in the presence of Au, and at temperatures in the vicinity of Au/In eutectic temperature. They were found to have Au at the NW tip, NW base, and NW sidewalls. Extensive investigation of the fundamentals underlying these anomalies has been carried out. The temperature dependence of the VLS mechanism has also been elucidated. A large number of available elemental and compound semiconductor NWs exhibiting similar characteristics have been considered for the investigation. Based on this investigation, a chemicophysical mechanism called the vapor-quasisolid-solid (VQS) (or vapor-semisolid-solid, or vapor-quasiliquid-solid, or vapor-semiliquid-solid) mechanism has been proposed. The cause of temperature dependence of the VLS growth under different growth conditions and growth environments, and the possible relationship between the VLS and the VQS mechanisms has been presented. To better describe the vapor-phase mechanisms, including the VQS mechanism, a unified definition of droplets has been proposed. A series of experimental evidences has been set forth to substantiate the validity of the proposed mechanism, and to justify the definition of the unified droplet model. They together appear to explain the fundamental basis of the NW growth by various mechanisms, including the VQS mechanisms. They also provide solutions of many known problems, conflicts, confusions, and controversies involving NW growth.
气相机制[例如，气-液-固（VLS）、气-固-固、氧化物辅助生长和自催化生长机制]对于单向纳米线（NW）的生长尚未得到很好的理解。为此，我们在实验室中进行了 GaN 和 InN NW 的生长实验，没有和有外加元素催化剂（FECA），如 Au 和 In。在 FECA 与 Ni 相同的情况下，GaN NW 的生长可以在低于 Ni/Ga 共晶温度的温度下进行。在 Au 的存在下，InN NW 的生长可以在接近 Au/In 共晶温度的温度下进行。在 NW 尖端、NW 基底和 NW 侧壁都发现了 Au。对这些异常现象的基础进行了广泛的研究。也阐明了 VLS 机制的温度依赖性。考虑了大量具有类似特性的可用元素和化合物半导体 NW 进行研究。基于这项研究，提出了一种称为气相准固态-固态（VQS）（或气相半固态-固态、气相准液态-固态、气相半液态-固态）的化学物理机制。提出了不同生长条件和生长环境下 VLS 生长的温度依赖性的原因，以及 VLS 和 VQS 机制之间的可能关系。为了更好地描述气相机制，包括 VQS 机制，提出了一个统一的液滴定义。提出了一系列实验证据来证实所提出的机制的有效性，并证明统一的液滴模型的定义是合理的。它们似乎一起解释了各种机制（包括 VQS 机制）的 NW 生长的基本基础。它们还为涉及 NW 生长的许多已知问题、冲突、困惑和争议提供了解决方案。
