面心立方相硅纳米晶的铝硅合金相分离可控制备法及材料性质研究

Face-centered cubic silicon (fcc-Si) is one of the high-pressure metal phases of silicon and it is different from the traditional semiconductor cubic-diamond silicon (cd-Si). So far, fcc-Si is still a material that cannot be controllably fabricated nor carefully studied. Given the great importance and wide application of semiconductor silicon, to realize the controllable fabrication of fcc-Si shows a great value in science and it may lead to important application. However, the formation pressure of fcc-Si reaches about 80 GPa, which pressure is too high to grow the bulk fcc-Si material through the state-of-art high-pressure technology. To solve this problem, we proposed a new method of Al-Si alloy phase separation and now have succeeded to fabricate the thin films that contain obvious fcc-Si nanocrystal under normal-pressure condition. Base on the above work, we would like to systematically investigate the formation mechanism and controllable fabrication of fcc-Si nanocrystals in this project. Also, we would like to reveal the material properties and electronic structure of fcc-Si nanocrystal using both experiment and calculation methods. Finally, we would like to explore the possibility of the application of fcc-Si in semiconductor devices. We believed that this project would help us to understand the formation mechanism of high-pressure phase Si materials, to enrich their fabrication method, to master their material properties, and to explore their possibility of device application.

面心立方相硅晶体是一种不同于金刚石相硅晶体的高压相硅材料，迄今为止尚未得到可控制备和系统研究。鉴于半导体硅产业的重要性和广泛性，实现面心立方相硅材料的可控制备将具有很高的科学价值和潜在的应用价值。然而，高达80GPa左右的平衡相变压力阻碍了面心立方相硅材料的制备和研究。针对这一问题，我们采用常压条件下的铝硅合金相分离法初步制备了含有面心立方相硅纳米晶的薄膜；基于此工作，我们拟在本项目中系统研究面心立方相硅纳米晶在非平衡相变压力条件下的形成规律和可控制备，同时采用实验和计算相结合的方法揭示其材料特性和电子结构，并初步探索其器件应用潜力。本项目的实施和完成将有助于进一步理解高压相硅材料的形成机制、丰富其制备方法、了解其材料性质、奠定其应用基础。

面心立方相（FCC）硅晶体是一种不同于金刚石相（CD）硅晶体的高压相硅材料，迄今为止尚未得到可控制备和系统研究。实现面心立方相硅材料的可控制备将具有很高的科学价值和潜在的应用价值。按照相图理论，常规的金刚石结构晶体硅需要在80GPa左右的压力下才能转变为面心立方相硅材料，因此通常情况下无法获得面心立方相的硅晶体。本项目研究了面心立方相硅纳米晶在非平衡相变压力条件下的形成规律和可控制备，同时采用实验和计算相结合的方法揭示其材料特性和电子结构。. 具体来说，我们采用磁控溅射法或等离子体增强化学气相沉积法制备了磷掺杂的非晶态SiCx薄膜、Si薄膜，通过800-1200oC高温退火使薄膜结晶，通过高分辨透射电镜及选区电子衍射技术，发现并详细表征了FCC相的硅纳米晶颗粒。我们采用热力学原理，理论推导出FCC相纳米晶颗粒形核所需的热力学临界条件。FCC硅纳米晶能否形成取决于FCC相硅纳米晶与金刚石相相硅纳米晶之间的形核竞争，只有当FCC相硅纳米晶的形核吉布斯自由能低于CD相硅纳米晶的形核吉布斯自由能时，且同时满足FCC相硅纳米晶核心可以稳定存在的热力学条件时，FCC相晶核才可以形成并生长。我们又通过第一性原理计算，计算了FCC相硅晶体的电子结构，并探索FCC硅晶体的各种光电性质。. 另外，我们也做了其他的应用研究，主要是制备了不同结晶度和掺杂浓度的纳米晶硅薄膜，并将其应用于晶体硅材料的表面钝化和载流子收集，可称之为钝化接触技术。研究显示，重掺杂纳米晶硅薄膜与氧化硅薄膜结合对硅的表面具有优异的钝化效果。最后，我们利用硅纳米晶薄膜获得了优异的钝化指标，也制备了高效率的硅太阳电池。