核/壳微结构氮化硅陶瓷线圈超弹性动力学理论与实验研究

With the rapid development of the microelectronics industry, the feature size of basic device is becoming smaller. The brittleness of traditional ceramics can not meet the operating requirement and this is the greatest drawback in making the ceramics available as engineering materials. It is an effective way of questing ceramics with excellent super elastic property. Based on it, we conduct the study on super elastic dynamics theory and experiment of silicon nitride with core /shell microstructure. The feature size and interfacial bonding status of both core and shell parts, as well as the effects on the superelasticity behavior, are studied by calculating and analyzing results to establish an accurate expression of elastic potential energy. The superelasticity behavior characteristics and differences under full and partial load cycles are analyzed in order to obtain the reasonable theoretical models of super elastic dynamics. The super elastic property of silicon nitride is investigated experimentally for the purpose of emphatically verifying and correcting the elastic potential energy expressions and super elastic dynamics models put forward in theoretical study. The super elastic dynamics theory and quantitative forecasting models of silicon nitride with core/shell microstructure is accurately established on the basis of summarizing various factors and relationships between each other. The objective of the present study is to clarify the superelasticity reason and behavior mechanism of silicon nitride with core/shell microstructure, and to provide the theoretical and technical foundation for preparing the superelasticity ceramics and a new generation of microelectronic devices.

随着微电子行业的飞速发展，基础器件的特征尺寸在不断缩小，而传统脆性陶瓷不能满足其使用要求，成为制约该技术发展的瓶颈，寻求超弹性陶瓷是解决此问题的有效途径之一。基于此，本项目通过理论与实验相结合的方法对核/壳微结构氮化硅陶瓷线圈的超弹性进行基础科学研究。理论计算与分析微结构中核、壳两部分的特征尺寸和界面结合态及其对线圈超弹性行为的影响规律，研究完全和部分加载循环下不同超弹性行为特征与差异，建立合理的弹性势能表达式和超弹性动力学理论模型；实验研究核/壳微结构氮化硅线圈超弹性，并对理论研究中提出的弹性势能表达式和超弹性动力学理论模型进行验证和修正，在对各种影响因素及相关性理论总结的基础上建立准确的核/壳微结构氮化硅陶瓷超弹性动力学理论及定量预测模型。本项目旨在澄清核/壳微结构氮化硅陶瓷超弹性成因及力学行为机制，为制备超弹性陶瓷及研制出新一代微电子基础器件奠定理论和技术基础。

作为结构功能一体化陶瓷，氮化硅将会在微纳器件领域大放异彩，而超弹性陶瓷是研究热点。本项目建立了氮化硅纳米陶瓷线圈模型，并利用分子动力学模拟研究了超弹性性能。结果表明，加载-伸长量曲线中，拉伸最大伸长量为3nm时，五次循环后，线圈可恢复到原来的状态，加载和卸载曲线的斜率相同，展示了稳定的弹性性能。当拉伸最大伸长量为5nm时，斜率为0.72 N•m-1，且随应变而逐渐增加，卸载后线圈存在可逆性，表明氮化硅陶瓷线圈的超弹性是存在的，使其在微尺度电子领域如纳米弹性能量存储器件等具有广阔的应用。此外，考察了[1010]方向氮化硅纳米线不同加载温度和应变下的拉伸性能，结果表明，在应变低于0.025时，展示线性行为，在应变高于0.025时，展示非线性行为；当加载温度从300K增大到1100K时，断裂应力从45GPa降低到35.1GPa，同时，断裂应变从0.055降低到0.038，这归因于大量Si-Si键和单个N原子断键缺陷；当应变速率逐渐增加时，断裂应力和应变也逐渐变大，当应变速率从0.5×109s-1增加到6×109 s-1时，断裂应力从44.6GPa增加到50GPa，而且断裂应变从0.057增加到0.065，高应变下没有发现明显的大量缺陷，但会导致裂纹的延迟，这可能归结于冲击变形的响应趋势。最后，采用第一性原理计算了稀土元素铈掺杂氮化硅体系的电子结构及其光学性能，结果表明，体系的带隙逐渐变窄，接近与半导体相匹配的带隙；能带密度逐渐增加，总能带数分别为80，84和88；差分电荷密度图表明，随掺杂浓度的提高，铈与氮成键的共价性逐渐降低，离子性逐渐升高；掺一个铈原子体系在低能区的介电常数和损耗较小，表明其作为电介质材料在光电器件应用中具有较长的使用寿命。总的来说，本项目计算结果可为微纳光电器件用新型氮化硅陶瓷的设计提供坚实的理论基础。