Catalyzed Nucleation and Growth of Semiconductor Nanowires

技术.本计画针对半导体奈米线之局部触媒成核与成长，结合模拟与模型化，并进行原位与非原位实验。计算和实验紧密结合的方法将有助于从根本上理解NW结构演化的机制以及如何控制它们。原子模型和控制实验的NW成核和生长动力学将进行，以便提供直接的比较。以下问题与金属催化的NW合成将得到解决：Q1。NW在不同基质上的成核机制是什么？它与某些催化剂-NW体系中观察到的深亚共晶成核有何关系？Q2.什么机制控制正常的NW生长并导致生长异常（例如扭结）？Q3. NW生长终止（催化剂纳米颗粒固化）的机制是什么？使用Si/Ge NW系统作为试验台，在受控温度和压力条件下CVD生长期间的原位和非原位测量将与数值预测进行比较，验证和指导计算方法的发展，以克服成核事件建模中的时间尺度挑战。后者是一个众所周知的原子模拟的适用范围的主要限制。由于成核事件在物理、化学和生物过程中经常发生，因此所获得的新理解有望有益于原子建模的更广泛领域。该项目涉及电子/光子材料科学领域的基础研究问题，具有技术相关性。这项基础研究是在全球学术和工业实验室努力在新设备中使用半导体纳米线的背景下进行的，预计将产生强大的技术影响。通过该项目获得的有关核武器合成的结果可能对这些技术和其他新兴技术的发展产生影响。半导体纳米线所带来的新的科学和技术突破的前景吸引了本科生、研究生和教师对这种研究的浓厚兴趣。PI计划利用这种“兴奋”，并在其教育和推广活动中建立起来。将在以下方面采取具体行动：1）通过与一名高中科学教师合作，向代表性不足的少数民族推广科学教育; 2）在拟议研究的计算和实验部分提供本科生经验; 3）根据研究结果开发本科生和研究生课程模块。

Technical. This project addresses locally catalyzed nucleation and growth of semiconductor nanowires (NWs); the approach combines simulation and modeling with in situ and ex situ ex-periments. The closely coupled computational and experimental approach should help to gain fundamental understanding of mechanisms of NW structure evolution and how they can be con-trolled. Atomistic modeling and controlled experiments on NW nucleation and growth kinetics will be carried out so as to provide direct comparisons. The following questions related to metal-catalyzed NW synthesis will be addressed: Q1. What is the mechanism of NW nucleation on dif-ferent substrates and how does it relate to the observed deep sub-eutectic nucleation reported in some catalyst-NW systems? Q2. What mechanisms control normal NW growth and result in growth abnormalities (e.g. kinking)? Q3. What is the mechanism of the termination of NW growth (catalyst nanoparticle solidification)? Using the Si/Ge NW system as a test bed, in situ and ex situ measurements during CVD growth at controlled temperature and pressure conditions will be compared with numerical predictions, validating and guiding the development of compu-tational methods to overcome time scale challenges in the modeling of nucleation events. The latter is a well known major limit to the range of applicability of atomistic simulations to date. The new understanding gained is expected to benefit the broader field of atomistic modeling due to the common occurrence of nucleation events in physical, chemical and biological processes.Non-Technical. The project addresses fundamental research issues in a topical area of elec-tronic/photonic materials science having technological relevance. This basic research, being con-ducted within the context of worldwide efforts among academic and industrial labs to use semi-conductor NWs in new devices, is expected to have strong technological impact. Results ob-tained through this project on NW synthesis may have impact on the development of these and other emerging technologies. The prospect of new science and technology breakthroughs enabled by semiconductor NWs attracts strong interest in such research among undergrads, graduate stu-dents, and faculty. The PIs plan to leverage this 'excitement' and build on it in their education and outreach activities. Specific initiatives will be pursued in: 1) science education outreach to under-represented minorities through a collaboration with a high school science teacher; 2) un-dergraduate experiences in both computational and experimental components of the proposed re-search; and 3) undergraduate and graduate course module development based on research find-ings.