陶瓷/半导体纳米线室温塑性变形机制研究

Possessing direct band gap and hign electron mobilty, binary compound ceramics/semiconductors, such as GaAs, ZnO and SiC, have been applied to efficient photovoltaic devices, radio-frequency electronics and optoelectronics. However, room-temperature brittleness of their bulk materials is the main limitation to restric their wide application. Whereas their nanostructural counterparts exhibit phase transformation, dislocation and amorphization when they subject to external loading, showing well plasticity. Therefore, to develop room-temperature plasticity for ceramics/semiconductors, a useful appoach is to introduce nonastructure. We have recently observed dislocation dominated room temperature compressive plastcity in GaAs nanowires by combining in-situ transmission electron microscope observation and molecular dynamics simulations. Dislocation dominated plasticity is common in metals but rarely reported in ceramic/semiconductor materials. Activation and propagation of dislocations in ceramics/semiconductors still remain elusive so far. This proposal aims to elucidate the mechanism of dislocation, phasetransformation and amorphization dominated plasticity in GaAs, ZnO and SiC nanowires; to ascertain the critical scale for brittle-to-plastic transition by an approach combining in-situ transmission electron microscope, density functional theory, molecular dynamics and molecular statistical thermodynamics simulations. This research may provide theoretical mechanism on microstructural design for more ceramic/semiconductor nanomaterials with room-temperature plasticity.

二元化合物陶瓷/半导体GaAs、ZnO和SiC具有直接带隙和高电子活性，在高效光伏器件、射频电子及光电子领域已有应用。但是，GaAs等块体材料的室温脆性一直是制约其广泛应用的主要因素。而这些材料的纳米结构受外载作用时，则分别产生相变、位错和非晶化，表现出良好的塑性。因此，引入纳米结构是发展陶瓷/半导体材料具有室温塑性的方法之一。最近，申请人结合透射电镜原位压缩实验和分子动力学模拟，发现GaAs纳米线表现出位错主导的室温压缩塑性。位错在金属中很常见，但在陶瓷/半导体材料中的激发机制和传播规律还不清楚。申请项目拟采用透射电镜原位变形实验结合密度泛函、分子动力学和分子统计热力学方法，力图阐明GaAs等纳米线中位错活动、相变和非晶化主导的塑性行为的力学机制，揭示脆-塑性转变的临界尺寸的规律。该研究可能在微结构设计上，为人工合成更多具有室温塑性的陶瓷/半导体纳米材料提供理论机理。

二元化合物陶瓷/半导体GaAs、ZnO 和SiC 的室温脆性是制约其广泛应用的主要因素。为提高其室温塑性变形能力，研究者们在这些材料中发展了纳米结构。但是，受现有实验条件限制，对其室温塑性变形机制缺乏理解。申请人结合透射电镜原位变形实验和分子动力学及分子统计热力学模拟：（1）研究了SiC和ZnO纳米线中相变主导的塑性变形行为，阐明了这类纳米结构中位错活动、相变和非晶化主导的塑性行为的力学机制；（2）以GaAs和ZnO纳米线为例，研究了纳米结构诱发的塑性行为的尺寸效应，揭示了脆-塑性转变的临界尺寸的规律；（3）分析了纳米结构对陶瓷/半导体力学性能的影响，提出采用纳米尺度堆垛层错提高脆性材料强度的方案。该项目的成果可能在微结构设计上，为人工合成更多具有室温塑性且兼具高强度的陶瓷/半导体纳米结构提供理论机理。