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

这个职业项目探索半导体材料和电子领域的纳米科学和技术。这项研究活动旨在开辟材料科学和纳米技术之间的新接口。一种新的策略被用来在硅中通过外延封装原子有序的2D掺杂图案来制造纳米级的导电路径，这包括(1)通过用来自扫描隧道显微镜(STM)的电子束解吸H-原子来图案化H-端的硅表面，(2)加入含有掺杂剂的前体，如PH3和B2H6，它们与裸Si反应，但不与Si-H表面反应。当前驱体分子吸附到裸硅上时，形成自有序阵列，这有助于避免掺杂聚集，并确保STM暴露区域内的均匀覆盖；(3)外延硅的过度生长以激活单个掺杂，并将这些纳米级电路图案封装到体硅中。一个主要的目标是研究由栅极电压控制的纳米级掺杂图案之间的电子传输。当电激活时，P或As等单个施主的玻尔半径约为2.5 nm，因此在低温下，每个掺杂原子的电学直径约为5 nm。不同施主位置上的波函数在间隔约10 nm处开始重叠，从而在平均密度超过108 cm-3时引起隧穿并防止载流子冻结。因此，在小于10 nm的尺度上精确定位掺杂的能力意味着有可能对波函数重叠进行详细控制，并有可能制造任何所需的2D几何形状的人造导电晶格。通过重复这三步过程，可以实现3D电路。系统地研究了前体分子在各种硅氢化物表面的选择性沉积和分解，以及在掺杂饱和图案上的硅层的外延生长。将评估从最初的表面准备到最终的电接触的过程，以保存纳米级的掩埋掺杂图案。将开发低温表征技术来监控所装配结构的电学性能。%该项目解决具有高度技术相关性的材料科学的一个主题领域的基础研究问题。这项研究将在基础水平上为电子材料和先进器件的重要方面贡献基本的材料科学知识。该项目的范围将使学生面临来自材料生长、表面物理、表面化学和设备物理的挑战。该计划的一个重要特点是强调教育，强调研究和教育的结合，通过在一个具有根本和技术意义的研究领域对学生进行培训，通过发现来加强学习。这些领域的综合技能和知识将为未来在材料科学、物理和电子设备技术领域的职业生涯奠定坚实的基础。

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.