论文标题
第一原理研究二维电子和孔 - 尾巴和尾巴180 $^\ circ $ tomain walls pbtio $ _ {3} $铁电薄膜
First-principles study of two-dimensional electron and hole gases at the head-to-head and tail-to-tail 180$^\circ$ domain walls in PbTiO$_{3}$ ferroelectric thin films
论文作者
论文摘要
我们从第一原则研究了头对头（HH）和尾巴（TT）180 $^\ Circ $域壁的结构和电子性能，该壁壁是孤立的独立式PBTIO $ _ {3} $板。对于足够厚的域（$ n $ = 16个PBTIO $ _ {3} $的单位单元），将电荷从自由表面转移到域壁上形成局部电子（在HH中）和TT（在TT）气体中（在TT）气体中，以筛选界限偏置电荷。从平滑的自由电荷密度与结合电荷分布之间的完美匹配中可以清楚地看到该电子重建背后的静电驱动力，这些匹配是根据晶格自由度放松后获得的极化分布的有限差异计算得出的。大约六个单位单元格的域壁宽度大于常规180 $^\ circ $中性配置中的域宽度。由于我们的模拟中没有引入缺氧或掺杂原子，因此所有先前的物理量都是系统的内在限制。我们的结果支持在域壁上存在额外的电荷来源，以解释在某些原型壁壁中观察到的电导率的增强，在散装，钙钛矿氧化物中进行绝缘。
We study from first-principles the structural and electronic properties of head-to-head (HH) and tail-to-tail (TT) 180$^\circ$ domain walls in isolated free-standing PbTiO$_{3}$ slabs. For sufficiently thick domains ($n$ = 16 unit cells of PbTiO$_{3}$), a transfer of charge from the free surfaces to the domain walls to form localized electron (in the HH) and hole (in the TT) gases in order to screen the bound polarization charges is observed. The electrostatic driving force behind this electronic reconstruction is clearly visible from the perfect match between the smoothed free charge densities and the bound charge distribution, computed from a finite difference of the polarization profile obtained after the relaxation of the lattice degrees of freedom. The domain wall widths, of around six unit cells, are larger than in the conventional 180$^\circ$ neutral configurations. Since no oxygen vacancies, defects or dopant atoms are introduced in our simulations, all the previous physical quantities are the intrinsic limits of the system. Our results support the existence of an extra source of charge at the domains walls to explain the enhancement of the conductivity observed in some domains walls of prototypical, insulating in bulk, perovskite oxides.
