Collaborative Research: Directed Templating of Semiconductor Nanocrystals Through Laser Melting

光子和电子器件中的许多应用需要在支撑材料上的高质量半导体晶体生长，所述支撑材料不固有地促进，也不与当前的制造工艺兼容。关键的，但仍然具有挑战性的步骤是故意模板的纳米晶体与所需的大小，方向和放置精度在这样的基板上。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畴以及制造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。耦合的实验和计算方法和最先进的nanofabelets国家将提供新的机会，本科生和研究生，特别是代表性不足的少数民族有研究经验和国家的最先进的培训，在纳米科学和工程，从而积极影响工程教育。Nanocrystal种子具有高度均匀的大小和方向将通过激光结晶在有限的nanodomains制造。该研究小组将通过将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，实现对纳米畴中激光结晶的基本理解。这种独特的综合研究方法将使工程的纳米约束几何形状和强加的瞬态激光协议参数可靠地产生良好控制的种子纳米晶体。将利用现有技术的聚焦离子束（FIB）处理和激光干涉光刻来限定最小直径为10 nm的纳米腔，其中将沉积非晶半导体（Si，Ge）。利用纳米压印技术，利用FIB制作的模具，可以制作出大面积的纳米腔体。脉冲激光辐射与调制的背景加热相结合，将被用来将非晶沉积物转化为纳米晶体与故意设计的大小和晶体取向。这样产生的局部晶体可以用作结晶晶种，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理解。最后，籽晶结晶工艺将使得能够在外延非参与衬底上控制大面积单晶薄层的生长。

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.