Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-3290, United States.
ACS Nano. 2014 Jun 24;8(6):6081-8. doi: 10.1021/nn501403v. Epub 2014 May 13.
The vapor-liquid-solid (VLS) mechanism is widely used for the synthesis of semiconductor nanowires (NWs), yet several aspects of the mechanism are not fully understood. Here, we present comprehensive experimental measurements on the growth rate of Au-catalyzed Si NWs over a range of temperatures (365-480 °C), diameters (30-200 nm), and pressures (0.1-1.6 Torr SiH4). We develop a kinetic model of VLS growth that includes (1) Si incorporation into the liquid Au-Si catalyst, (2) Si evaporation from the catalyst surface, and (3) Si crystallization at the catalyst-NW interface. This simple model quantitatively explains growth rate data collected over more than 65 distinct synthetic conditions. Surprisingly, upon increasing the temperature and/or pressure, the analysis reveals an abrupt transition from a diameter-independent growth rate that is limited by incorporation to a diameter-dependent growth rate that is limited by crystallization. The identification of two distinct growth regimes provides insight into the synthetic conditions needed for specific NW-based technologies, and our kinetic model provides a straightforward framework for understanding VLS growth with a range of metal catalysts and semiconductor materials.
汽液固（VLS）机制被广泛用于半导体纳米线（NWs）的合成，但该机制的几个方面尚未完全理解。在这里，我们在 365-480°C 的一系列温度、30-200nm 的直径和 0.1-1.6Torr SiH4 的压力范围内，对 Au 催化的 SiNWs 的生长速率进行了全面的实验测量。我们开发了一种 VLS 生长的动力学模型，该模型包括（1）Si 掺入液体 Au-Si 催化剂，（2）Si 从催化剂表面蒸发，以及（3）Si 在催化剂-NW 界面处结晶。这个简单的模型定量解释了在超过 65 种不同合成条件下收集的生长速率数据。令人惊讶的是，随着温度和/或压力的增加，分析表明从由掺入控制的直径独立生长速率到由结晶控制的直径依赖生长速率的突然转变。两种不同生长模式的确定为特定基于 NW 的技术所需的合成条件提供了深入的了解，我们的动力学模型为理解具有各种金属催化剂和半导体材料的 VLS 生长提供了一个简单的框架。
