Collaborative Research: Directed Templating of Semiconductor Nanocrystals Through Laser Melting

在光子和电子设备中的许多应用需要在支撑材料上生长高质量的半导体晶体，这些支撑材料本身并不促进，也与当前的制造工艺不兼容。最重要但仍然具有挑战性的一步是刻意在这些衬底上以所需的尺寸、取向和放置精度将纳米晶体模板化。该奖项支持基础研究，以获得实现成核和晶体生长过程的纳米级控制的知识。这项研究将为在廉价和丰富的衬底上制备薄晶区以及制备量子纳米器件开辟道路。应用包括用于先进显示器的薄膜晶体管、高性能薄膜太阳能电池、三维电子设备和量子计算机。这项研究将使美国的工业、经济和社会受益。实验和计算相结合的方法和最先进的纳米制造将为本科生和研究生，特别是代表不足的少数族裔提供新的机会，在纳米科学和工程方面拥有研究经验和最先进的培训，从而对工程教育产生积极影响。研究小组将通过将原位透射电子显微镜(TEM)的直接成像与详细的多尺度计算建模和分子动力学(MD)模拟相结合，实现对纳米领域激光结晶的基本了解。这种独特的集成研究方法将使工程的纳米限制几何和强加的瞬变激光协议参数可靠地产生良好控制的种子纳米晶体。最先进的聚焦离子束(FIB)处理和激光干涉光刻将被用来定义最小直径为10 nm的纳米腔，其中将沉积非晶态半导体(Si，Ge)。利用FIB制作的模具进行纳米压印，可以制作大面积的纳米空腔。利用脉冲激光辐射和调制背景加热相结合的方法，将非晶态沉积转化为具有特意设计的尺寸和晶体取向的纳米晶体。这种产生的局域晶体可以作为结晶种子，克服与非工程自发成核相关的不确定性。分子动力学(MD)模拟将在相同的长度尺度上进行，以提供对纳米限制域中的传热、成核机制、晶体生长和缺陷演化的基本了解。最后，种子晶化过程将能够在非参与的外延衬底上控制生长大面积单晶薄层。

Many applications in photonic and electronic devices require high quality semiconductor crystal growth on supporting materials that do not intrinsically promote, nor are compatible with current manufacturing processes. The essential, but still challenging step is the deliberate templating of nanocrystals with the desired size, orientation and placement accuracy on such substrates. This award supports fundamental research to acquire knowledge for achieving nanoscale control of nucleation and crystal growth processes. The research will open the way to the fabrication of thin crystalline domains on inexpensive and abundant substrates as well to the fabrication of quantum nanodevices. Applications include thin film transistors for advanced displays, high performance thin film solar cells, three-dimensional electronic devices and quantum computers. The research will benefit the U.S. industry, economy and society. The coupled experimental and computational methodology and state of the art nanofabrication will provide new opportunities for undergraduate and graduate students and in particular underrepresented minorities to have research experiences and state-of-the-art training in nanoscience and engineering, consequently positively impacting engineering education.Nanocrystal seeds with highly uniform size and orientations will be manufactured by laser crystallization in confined nanodomains. The research team will achieve fundamental understanding of laser crystallization in nanodomains by combining direct imaging via in situ Transmission Electron Microscopy (TEM) with detailed multi-scale computational modeling and molecular dynamics (MD) simulations. This uniquely integrated research approach will enable engineering of the nanoconfinement geometry and the imposed transient laser protocol parameters for reliable generation of well-controlled seeding nanocrystals. State of the art focused ion beam (FIB) processing and laser interference lithography will be utilized to define nanocavities with minimum diameter 10 nm wherein amorphous semiconductors (Si, Ge) will be deposited. Nano-cavities on large area will be fabricated by nanoimprinting with FIB fabricated molds. Pulsed laser radiation in combination with modulated background heating will be utilized to convert the amorphous deposits into nanocrystals with deliberately engineered size and crystallographic orientation. Such generated localized crystals can serve as crystallization seeds, overcoming uncertainty associated to un-engineered spontaneous nucleation. Molecular Dynamics (MD) simulation will be performed at the same length scale to provide fundamental understanding of heat transfer, nucleation mechanism, crystal growth and defect evolution in nano-confined domains. Finally, a seeded crystallization process will enable controlled growth of a large area monocrystalline thin layer on epitaxially non-participating substrates.