铁电薄膜漏电流的应变调控

基于密度泛函理论的第一性原理并结合非平衡格林函数, 探讨了应变对 BaTiO₃ 铁电薄膜漏电流的影响规律.研究表明,压应变能有效地抑制BaTiO₃ 铁电薄膜漏电流, 特别是当压应变为4%时,其漏电流相对无应变状态降低了近10 倍.通过考察体系的透射系数和电子态密度发现: 一方面压应变状态下铁电隧道结的透射几率要比张应变时小,特别是在费米面附近;另一方面随着张应变过渡至压应变时,价带的位置逐渐向低能区移动而导带向高能区移动,导致了其带隙的增大, 从而有效抑制了漏电流. 本研究为寻找抑制铁电薄膜漏电流,提高铁电薄膜及铁电存储器的性能提供合适的方法.关键词：铁电薄膜双轴应变漏电流第一性原理

Strain control of the leakage current of the ferroelectric thin films

Combining nonequilibrium Green's functions and first-principles quantum transport calculations in density-functional theory, we investigate the effect of biaxial strain on the leakage current of BaTiO₃ ferroelectric thin film. The results show that the compressive strain can effectively reduce the leakage current of ferroelectric thin film. Especially when the compressive strain is 4%, the leakage current will be reduced by nearly 10 times that of strain-free case. By calculating the transmission coefficient and the density of states, we find that the transmission probability of ferroelectric tunnel junction with compressive strain is smaller than that with tensile strain. Moreover, we find that the valence band shifts toward the lower energy zone while the conduction band moves toward the high energy zone, which leads to the enlarged energy band gap, thereby reducing the leakage current. Our study suggestes a suitable way to reduce the ferroelectric thin film leakage current and improve the performance of ferroelectric thin film and its relevant ferroelectric memory.