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

9875129 Shen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。研究活动旨在打开材料科学和纳米技术之间的新接口。采用一种新的策略，通过外延封装原子有序的2D掺杂剂图案来在硅中制造纳米级导电通路;这涉及（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封端的Si表面，（2）用含掺杂剂的前体（例如PH 3和B2 H6）给药，其与裸Si反应而不与Si-H表面反应。前体分子在吸附到裸Si上时形成自有序阵列，这有助于避免掺杂剂聚集并确保STM暴露区域内的均匀覆盖，（3）外延Si的过度生长以激活单个掺杂剂并将这些纳米级电路图案封装到体硅中。一个主要的目的是研究电子输运之间的纳米级掺杂剂图案控制的栅极电压。当被电激活时，单个施主如P或As的玻尔半径大约为2.5 nm，因此在低温下，每个掺杂剂原子的直径约为5 nm。不同施主位置上的波函数开始在约10 nm的间隔处重叠，导致隧穿并防止平均密度超过108 cm-3的载流子冻结。因此，在小于10 nm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，以及制造任何期望的2D几何形状的人工导电晶格的可能手段。通过重复三步工艺可以实现3D电路。将系统地研究在各种Si氢化物表面上选择性沉积和分解前驱物分子以及在掺杂剂饱和图案上外延生长Si层。从最初的表面准备到最终的电接触过程将被评估为纳米级掩埋掺杂剂图案的保存。将开发低温表征技术来监测制造结构的电性能。%该项目涉及具有高度技术相关性的材料科学专题领域的基础研究问题。该研究将为电子材料和先进设备的重要方面提供基础材料科学知识。该项目的范围将使学生面临来自材料生长，表面物理，表面化学和器件物理的挑战。该计划的一个重要特点是强调教育，以及研究和教育的整合，通过在基础和技术上重要的研究领域培养学生，通过发现来加强学习。这些领域的综合技能和知识将为材料科学，物理学和电子器件技术的未来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.