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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Nb and Ta layer doping effects on the interfacial energetics and electronic properties of LaAlO3/SrTiO3 heterostructure: first-principles analysis
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Nb and Ta layer doping effects on the interfacial energetics and electronic properties of LaAlO3/SrTiO3 heterostructure: first-principles analysis

机译：Nb和Ta层掺杂对LaAlO3 / SrTiO3异质结构界面能和电子性能的影响：第一性原理分析

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The two-dimensional electron gas (2DEG) formed at the n-type (LaO)(+1)/(TiO2)(0) interface in the polaronpolar LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) has emerged as a prominent research area because of its great potential for nanoelectronic applications. Due to its practical implementation in devices, desired physical properties such as high charge carrier density and mobility are vital. In this respect, 4d and 5d transition metal doping near the interfacial region is expected to tailor electronic properties of the LAO/STO HS system effectively. Herein, we studied Nb and Ta-doping effects on the energetics, electronic structure, interfacial charge carrier density, magnetic moment, and the charge confinements of the 2DEG at the n-type (LaO)(+1)/(TiO2)(0) interface of LAO/STO HS using first-principles density functional theory calculations. We found that the substitutional doping of Nb(Ta) at Ti [Nb(Ta)@Ti] and Al [Nb(Ta)@Al] sites is energetically more favorable than that at La [Nb(Ta)@La] and Sr [Nb(Ta)@Sr] sites, and under appropriate thermodynamic conditions, the changes in the interfacial energy of HS systems upon Nb(Ta)@Ti and Nb(Ta)@Al doping are negative, implying that the formation of these structures is energetically favored. Our calculations also showed that Nb(Ta)@Ti and Nb(Ta)@Al doping significantly improve the interfacial charge carrier density with respect to that of the undoped system, which is because the Nb(Ta) dopant introduces excess free electrons into the system, and these free electrons reside mainly on the Nb(Ta) ions and interfacial Ti ions. Hence, along with the Ti 3d orbitals, the Nb 4d and Ta 5d orbitals also contribute to the interfacial metallic states; accordingly, the magnetic moments on the interfacial Ti ions increase significantly. As expected, the Nb@Al and Ta@Al doped LAO/STO HS systems show higher interfacial charge carrier density than the undoped and other doped systems. In contrast, Nb@Ti and Ta@Ti doped systems may show higher charge carrier mobility because of the lower electron effective mass.
机译：在极性/非极性LaAlO3 / SrTiO3（LAO / STO）异质结构（HS）的n型（LaO）（+ 1）/（TiO2）（0）界面处形成的二维电子气（2DEG）出现了由于其在纳米电子领域的巨大潜力，因此成为一个突出的研究领域。由于其在设备中的实际实现，所需的物理特性（例如高电荷载流子密度和迁移率）至关重要。在这方面，预计界面附近的4d和5d过渡金属掺杂将有效地调整LAO / STO HS系统的电子性能。在这里，我们研究了Nb和Ta掺杂对n型（LaO）（+ 1）/（TiO2）（0）上2DEG的能量，电子结构，界面电荷载流子密度，磁矩和电荷限制的影响。 ）使用第一原理密度泛函理论计算的LAO / STO HS接口。我们发现，在Ti [Nb（Ta）@Ti]和Al [Nb（Ta）@Al]位上Nb（Ta）的替代掺杂在能量上比在La [Nb（Ta）@La]和Sr处更有利。 [Nb（Ta）@Sr]位置，在适当的热力学条件下，Nb（Ta）@Ti和Nb（Ta）@Al掺杂时HS体系的界面能变化为负，表明这些结构的形成受到大力支持。我们的计算还表明，与未掺杂的体系相比，Nb（Ta）@Ti和Nb（Ta）@Al掺杂显着提高了界面电荷载流子密度，这是因为Nb（Ta）掺杂剂将过量的自由电子引入了电子。这些自由电子主要存在于Nb（Ta）离子和界面Ti离子上。因此，Nb 4d和Ta 5d轨道与Ti 3d轨道一起也有助于界面金属态。因此，界面Ti离子上的磁矩显着增加。不出所料，Nb @ Al和Ta @ Al掺杂的LAO / STO HS系统显示出比未掺杂和其他掺杂系统更高的界面电荷载流子密度。相反，由于较低的电子有效质量，Nb @ Ti和Ta @ Ti掺杂的系统可能显示出较高的载流子迁移率。

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