Collaborative Research: Directed Templating of Semiconductor Nanocrystals Through Laser Melting

在光子和电子器件中的许多应用需要在支持材料上生长高质量的半导体晶体，这些材料本身并不促进，也不与当前的制造工艺兼容。最重要的，但仍然具有挑战性的一步是在这种基板上精心制作具有所需尺寸、方向和放置精度的纳米晶体模板。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造薄晶域以及制造量子纳米器件开辟道路。应用领域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、三维电子器件和量子计算机。这项研究将有利于美国的工业、经济和社会。耦合实验和计算方法以及最先进的纳米制造将为本科生和研究生，特别是代表性不足的少数民族提供新的机会，让他们在纳米科学和工程方面获得研究经验和最先进的培训，从而对工程教育产生积极影响。在有限的纳米畴内，通过激光结晶可以制备出尺寸和取向高度均匀的纳米晶种子。研究团队将通过原位透射电子显微镜（TEM）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理解。这种独特的综合研究方法将使纳米约束几何结构的工程和施加的瞬态激光协议参数能够可靠地产生良好控制的播种纳米晶体。将利用最先进的聚焦离子束（FIB）处理和激光干涉光刻技术来定义最小直径为10纳米的纳米腔，其中将沉积非晶半导体（Si, Ge）。利用FIB制备的模具进行纳米压印，制备出大面积的纳米空腔。脉冲激光辐射与调制背景加热相结合，将利用非晶沉积转化为具有精心设计的尺寸和晶体取向的纳米晶体。这种产生的局部晶体可以作为结晶种子，克服了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，晶体生长和缺陷演变的基本理解。最后，种子结晶工艺将使大面积单晶薄层在外延非参与衬底上的可控生长成为可能。

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.