应变对氧化锌压电性能的调制机理研究

Study on the strain-modulation mechanism on the piezoelectricity of ZnO

本文采用基于密度泛函理论的第一性原理方法,研究了ZnO材料的压电性能与其所处应变状态的关系,探索并揭示了应变对ZnO材料压电性能的调制规律和影响机制.结果表明,随着体系所处的应变状态依次从较大的压应变、较小的压应变、较小的拉应变到较大的拉应变变化时,ZnO材料沿[0001]方向的压电系数e33单调递减,而并非定值.体系受较大拉应变时的压电系数仅约为受较大压应变时的1/8.我们发现体系沿[0001]方向的波恩有效电荷的变化与应变产生的与极化方向不共线的化学键的旋转的共同作用,可能是导致体系压电性能随应变状态发生变化的主要原因.这种由应变引起的机电耦合性能调制效应可为涉及ZnO及同类材料压电性能的器件设计和应用提供新的思路和理论支撑.

The strain-modulation mechanism on the piezoelectricity of ZnO is investigated by using first-principles calculations. It is shown that the piezoelectric coefficient along the [0001] axis e33 is not a constant, but monotonically decreases with the strain states changing from larger compressive strain, smaller compressive strain, smaller tensile strain, to larger tensile strain. And the piezoelectric coefficient in the larger tensile strain state is only about l/8 of the value when the system is in the larger compressive strain state. It is shown that the collaborative work of the strain-induced variety of Born Effective Charge along the [0001] axis and rotation of Zn--O bonds which is non-collinear with the [0001] axis is the main reason for the variation of piezoelectricity with the changing strain states of ZnO. Such modulation effect of electromechanical coupling induced by strain could provide some new ideas and theoretical supports for the device designs and applications involving piezoelectricity of ZnO and related materials.