Isotopically Controlled Semiconductors: Diffusion and Nanocrystals

该项目涉及(1)晶体薄膜多层结构中的原子扩散物理和(2)由同位素控制的半导体组成的纳米粒子的性质。首次在应变和松弛的硅-锗(SiGe)多层结构中直接和同时研究自扩散(即同位素互扩散)和掺杂扩散。这些研究旨在揭示各种扩散机制背后的物理机制。预期的结果将扩展基本的固态知识库，可能导致新的扩散工艺的发现，并将直接用于未来的SiGe电子器件的设计者。该提案进一步讨论了同位素纯锗纳米晶体的性质。选择性中子嬗变掺杂(NTD)将用于形成受主(70Ge)或供体(74Ge)。NTD过程看起来很有希望，因为它发生的温度足够低，新形成的掺杂原子可以留在纳米晶体内。同位素组成的选择也允许选择具有或不具有核自旋的同位素。具有可控核自旋分布的半导体目前对迅速崛起的“自旋电子学”领域非常感兴趣。这项拟议的研究为研究生和本科生提供了几个科学技术领域的前沿研究培训。该项目涉及(1)晶体薄膜多层结构中的扩散研究和(2)由半导体元素硅和锗的浓缩同位素组成的纳米粒子的性质。原子自扩散和掺杂扩散被用于制造现代半导体器件(芯片)的几个关键工艺中。本研究旨在揭示硅和锗混合物中的原子级扩散机制。这些结果将扩展固态基础知识库，并可能导致新的扩散过程的发现。后者将直接用于未来超高速电子设备的设计者。该提案进一步讨论了使用选择性核技术掺杂的同位素纯锗纳米晶体的性质。同位素组成的选择也允许选择具有核自旋的同位素，这些同位素目前对迅速崛起的“自旋电子学”领域非常感兴趣。这项拟议的研究为研究生和本科生提供了几个科学技术领域的前沿研究培训。

This project addresses (1) the physics of atomic diffusion in crystalline thin film multilayer structures and (2) the properties of nano-particles composed of isotopically controlled semiconductors. Self-diffusion (i.e., isotope inter-diffusion) and dopant diffusion will be studied directly and simultaneously for the first time in strained and relaxed silicon-germanium (SiGe) multi-layer structures. The studies are designed to reveal the physics underlying the various diffusion mechanisms. The expected results will expand the fundamental solid-state knowledge base, may lead to the discovery of new diffusion processes, and will be of direct use to the designers of future SiGe electronic devices. The proposal further addresses the properties of isotopically pure germanium nano-crystals. Selective Neutron Transmutation Doping (NTD) will be used to form acceptors (70Ge) or donors (74Ge). The NTD process looks promising because it occurs at temperatures sufficiently low for the newly formed dopant atoms to remain inside the nanocrystal. Choice of the isotopic composition also allows selection of isotopes with or without nuclear spin. Semiconductors with controlled nuclear spin distribution are of great current interest to the rapidly emerging field of "spintronics." The proposed research offers graduate and undergraduate students training in cutting-edge research in several fields of science and technology.This project addresses (1) the study of diffusion in crystalline thin film multilayer structures and (2) the properties of nano-particles composed of enriched isotopes of the semiconductor elements silicon and germanium. Atom self-diffusion and dopant diffusion are used in several of the key processes used to fabricate modern semiconductor devices ("chips"). The present studies are designed to reveal the atomic-level diffusion mechanisms in mixtures of silicon and germanium. The results will expand the fundamental solid-state knowledge base, and may lead to the discovery of new diffusion processes. The latter will be of direct use to the designers of future very high-speed electronic devices. The proposal further addresses the properties of isotopically pure germanium nano-crystals that have been doped using selective nuclear techniques. Choice of the isotopic composition also allows selection of isotopes with nuclear spin that are of great current interest to the rapidly emerging field of "spintronics." The proposed research offers graduate and undergraduate students training in cutting-edge research in several fields of science and technology.