CAREER: Exploring Nanostructures Based on Atomically Ordered 2D Dopant Patterns in Si

这个CAREER项目探索半导体材料和电子领域的纳米科学技术。这项研究活动的目的是在材料科学和纳米技术之间开辟一个新的界面。采用外延封装原子有序二维掺杂模式的新策略在硅中制备纳米级导电通路；这包括(1)通过扫描隧道显微镜（STM）的电子束解吸h原子来形成h端Si表面的图案，(2)添加含有掺杂剂的前体，如PH3和B2H6，它们与裸Si反应，但不与Si- h表面反应。前驱体分子吸附在裸硅上形成自有序阵列，这有助于避免掺杂团簇并确保在stm暴露区域内均匀覆盖。(3)外延硅的过度生长激活单个掺杂剂并将这些纳米级电路模式封装到体硅中。主要目的是研究由栅极电压控制的纳米级掺杂模式之间的电子传输。当电激活时，单个给体（如P或as）的玻尔半径约为2.5 nm，因此在低温下，每个电掺杂原子的直径约为5 nm。不同给体位点上的波函数在~ 10nm的间隔处开始重叠，导致隧道效应，并防止载流子在平均密度超过108cm -3时冻结。因此，在小于10nm的尺度上精确定位掺杂剂的能力意味着对波函数重叠进行详细控制的潜力，以及制造任何所需二维几何形状的人工导电晶格的可能手段。可通过重复上述三步过程来实现三维电路。前驱体分子在各种硅氢化物表面的选择性沉积和分解以及硅层在掺杂饱和模式上的外延生长将被系统地研究。从最初的表面制备到最终的电接触过程将被评估，以保存纳米级埋藏的掺杂模式。低温表征技术将被开发，以监测制造结构的电性能。该项目涉及具有高技术相关性的材料科学主题领域的基础研究问题。该研究将为电子材料和先进器件的重要方面提供基础材料科学知识。项目的范围将使学生接触到材料生长、表面物理、表面化学和器件物理等方面的挑战。该计划的一个重要特点是强调教育，并强调研究与教育的结合，通过培养学生在基础和技术上重要的研究领域的发现来提高学习。这些领域的综合技能和知识将为未来在材料科学、物理和电子器件技术方面的职业生涯提供坚实的基础。

9875129ShenThis CAREER project explores nanoscale science and technology in semiconductor materials and electronics. The research activity is aimed at opening a new interface between materials science and nanotechnology. A novel strategy is employed for fabricating nanoscale conducting pathways in silicon by epitaxially encapsulating atomically ordered 2D dopant patterns; this involves (1)patterning H-terminated Si surfaces by desorbing H-atoms with an e-beam from a scanning tunneling microscope (STM), (2)dosing with dopant-containing precursors such as PH3 and B2H6 which react with bare Si but not with Si-H surfaces. The precursor molecules form self-ordered arrays when adsorbed onto bare Si, which help to avoid dopant clustering and ensure uniform coverage within the STM-exposed regions, (3)overgrowth of epitaxial Si to activate individual dopants and encapsulate these nanoscale circuit patterns into bulk silicon. A primary objective is to study electron transport between nanoscale dopant patterns controlled by a gate voltage. When electrically activated, the Bohr radius for individual donors such as P or As is roughly 2.5 nm, so that electrically each dopant atom is ~5 nm in diameter at low temperatures. Wavefunctions on different donor sites begin to overlap at separations of ~10 nm, causing tunneling and preventing carrier freeze-out at average densities in excess of 108 cm-3. The ability to accurately position dopants on a scale smaller than 10 nm thus implies the potential for detailed control over wavefunction overlap and a possible means to fabricate artificial conducting lattices of any desired 2D geometry. 3D circuits may be realized by repeating the three-step process.Selective deposition and decomposition of precursor molecules on various Si hydride surfaces and epitaxial growth of Si layers over the dopant-saturated patterns will be systematically studied. Processes from initial surface preparation to final electrical contact will be assessed for preservation of the nanoscale buried dopant patterns. Low-temperature characterization techniques will be developed to monitor the electrical properties of the fabricated structures.%%%The project addresses fundamental research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important aspects of electronic materials and advanced devices. The scope of the project will expose students to challenges from materials growth, surface physics, surface chemistry, and device physics. An important feature of the program is the emphasis on education, and on the integration of research and education to enhance learning through discovery through the training of students in a fundamentally and technologically significant research area. Integrated skills and knowledge in these areas will provide a solid basis for future careers in materials science, physics, and electron device technology.