New electric functionality of lattice matched ferroelectric semiconductor heterostructures

1)通过铁电异质结构的电流输运发现电流通过钙钛矿半导体上的（Pb，La）（Zr，Ti）0_3铁电体呈现二极管特性，其极性普遍由半导体的载流子导电类型决定。所观察到的电流-电压（IV）特性，极性依赖性，弛豫，和调制是可以解释的，如果我们假设一个pn或pp结在铁电半导体界面。一个持久的高度可再现的电阻调制的直流电压，它具有很短的保留时间，被观察到，并归因于一个带弯曲的铁电体的带电状态的形成。在（Pb，La）（Zr，Ti）0_3/SrTiO_3：Nb中，由于自发极化（P）开关引起的能带弯曲，在脉冲电压下观察到了可重复的电阻调制，并具有较长的保持时间。（p：空穴传导型，a：电子传导型）。此外， ...更多信息 在Pb（Ti，Zr）0_3铁电/SrTiO_3外延异质结构中，电流随温度的降低而电导。通过与其它铁电外延异质结构的电流-电压特性的比较和能带图分析表明，电流是通过Pb（Ti，Zr）O_3和SrTiO_3形成的Rn结隧穿的，并进一步研究了铁电体单畴部分的纳米级电接触特性。也就是说，无限带隙材料，具有自发极化。基于这一假设，人们提出了有限尺寸效应、畴结构和退极化场不稳定性的理论。然而，大多数氧化物钙钛矿铁电体具有3至4 eV的有限带隙。我们表明，有限带隙效应的包含急剧改变传统的理解的有限尺寸效应，域结构和其他。从本方法中提取的结论与最近的实验结果是一致的。少

1) Current transport through ferroelectric heterostructuresCurrent through (Pb, La)(Zr, Ti)0_3 ferroelectrics on perovskite semiconductors is found to exhibit diode characteristics of which polarity is universally deternuned by the carrier conduction type of the semiconductors. The observed current voltage (IV) characteristics, the polarity dependence, the relaxation, and the modulation are explicable, if we assume a pn or a pp junction at the ferroelectric semiconductor interface. A persisting highly reproducible resistance modulation by a dc voltage, which has a short retention, is observed and is ascribed to a band bending of the ferroelectric by the formation of charged states. A reproducible resistance modulation by a pulse voltage, which has a long retention, is observed in (Pb, La)(Zr, Ti)0_3/SrTiO_3 : Nb due to a possible band bending by the spontaneous polarization (P) switching. (p : hole conduction type, a : electron conduction type).Additionally, an anomalous increase of el … More ectric conduction with decreasing temperature was found in the current through Pb(Ti, Zr)0_3 ferroelectric/SrTiO_3 epitaxial heterostructures. Comparison with current-voltage characteristics of other ferroelectric epitaxial heterostructures and the analysis using the band diagram indicate that the current is tunneling through the Rn lunction formed by Pb(Ti, Zr)O_3 and SrTiO_3.Furthermore, properties of nm-scale electrical contact on single domained part of ferroelectric is investigated.2) Construction of theoretical frame workIdeal ferroelectrics have mostly been modeled as insulators, i.e., infinite band gap materials, having a spontaneous polarization. Based on this assumption, theories for the finite size effect, the domain configuration, and the depolarization field instability have been proposed. However, most of oxide perovskite ferroelectrics have finite band gaps of 3 to 4 eV.We show that the inclusion of the finite band gap effect changes drastically conventional understanding of the finite size effect, domain structares and others. The conclusions extracted from the present approach are consistent with recent experimental results. Less