氦离子辐照烧结碳化硅损伤效应的研究

Study of process and evolution of irradiation-induced damage in He irradiated sintered SiC, which can not only clarify, validate and develop the current theory of irradiation-induced damage of He irradiated SiC, further the knowledge of irradiation-induced defects which lead to the change of fracture and thermal conductivity, but also supply important data for fabricating advanced semiconductor facilities. In the project, using He ions which are provided by HIRFL irradiated sintered SiC. Combined with kinds of measurements and analyses, we will pay attention to the formation mechanism of planar nano-scale bubbles/cavities in He irradiated sintered SiC, distinguishing from the relationship of two-dimensional defects which are planar helium bubbles, to explore the nucleation and growth of interstitial-type defects in the vicinity of bubbles/cavities, and research further the effects of irradiation-induced damage on material ductility and thermal conductivity. What's more, we are going to establish a growth model of helium bubbles and nano-cavities in sintered SiC based on thoroughly analyzing the experimental results and data simulation, and the basic theory of damages produced by He irradiation. In addition, we are going to use the theories to explain the mechanism of He embrittlement and the deterioration of thermal conductivity. The investigations will supply a scientific foundation of SiC as a kind of nuclear materials and for fabricating chips of new grand scale integration by using nano-scale cavities in future.

探索氦离子辐照烧结碳化硅损伤过程以及损伤演化机理，不但可以澄清、验证和拓广现有的氦离子辐照碳化硅损伤理论，深化对碳化硅内部辐照缺陷引起材料韧性和热导率变化规律的认识，而且还可以为制备先进功能的半导体器件提供重要帮助。利用兰州重离子加速器提供的氦离子辐照烧结碳化硅，通过多种测试手段和分析方法，研究氦离子辐照烧结碳化硅内部氦泡、纳米空腔的盘状团簇的形成机理，澄清它与氦的另一类二维缺陷-盘状气泡的形成机理的联系与区别，探索气泡、空腔周围间隙型缺陷的形核和生长规律，并进一步研究辐照损伤对材料韧性和热导率性能的影响。在此基础上，通过综合分析现有实验数据，并根据氦离子辐照损伤基本理论和数值模拟，建立烧结碳化硅内部氦泡和纳米空腔生长模型，并从理论上解释碳化硅氦脆和热传导性能退化的原因，为碳化硅作为核能材料和今后利用纳米空腔缺陷工程制备新型超大规模集成电路芯片提供科学依据。

SiC是一种宽带隙半导体材料，具有击穿电压高、电子饱和迁移率大、介电系数小、抗辐照能力强和化学稳定性好等优良特性，因而在航空航天、核能仪器、雷达通讯等方面备受青睐。此外，由于SiC还具有高熔点、高耐腐蚀性能、高热导率、低热膨胀系数和低中子反应截面等优点，SiC非常适合用于先进核能反应堆和加速器驱动次临界装置等极端环境。在核能领域，由于(n, a)嬗变反应产生大量的氦，这些氦聚集形成氦泡，导致材料脆化，蠕变和硬化，所以研究氦辐照碳化硅，缺陷形成和演化机制对于碳化硅材料在强辐射环境中的应用有重要科学意义。. 在项目执行期，进行了如下九个方面的研究，其中包括：.1. 氦离子辐照烧结碳化硅，辐照温度、退火温度和晶界对氦泡形核的影响；.2. 硅、氦离子辐照4H-SiC和烧结碳化硅，级联碰撞密度对辐照损伤的影响；.3. 非晶碳化硅高温退火，碳化硅的重结晶过程；.4. 快重离子辐照引起的缺陷退火效应；.5. 氢离子辐照碳化硅，损伤效应的研究；.6. 氦、硅离子辐照烧结碳化硅，辐照缺陷引起材料硬度和热导率的变化；.7. 双束辐照与单束辐照烧结碳化硅，辐照损伤对比；.8. 4H-SiC在铅铋溶液中的腐蚀效应研究；.9. 离子辐照氮化镓、氧化铝、硅晶体，损伤效应的研究。. 项目达到了预期目标，包括氦泡形核、能态、辐照硬化、热导率变化方面研究任务，这些研究结果为碳化硅应用提供了重要科学数据。