Structural origin for the insulator-metal transition in LaTiO3 thin films

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization Pub Date : 2025-04-25 DOI:10.1016/j.matchar.2025.115085

Beibei Qiao , Tingting Yao , Xuexi Yan , Neng He , Qianqian Jin , Zhiqing Yang , Hengqiang Ye , Chunlin Chen

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Abstract

LaTiO₃ is a typical perovskite Mott-Hubbard insulator that exhibits abundant electrical properties. The extremely small band gap of LaTiO₃ facilitates the metal-insulator transition and makes the electrical properties easy to control. In this study, the electrical properties and microstructure of LaTiO₃ thin films fabricated on different substrates by pulse laser deposition have been investigated. Hall-effect measurements reveal that the LaTiO₃/LaAlO₃ thin film is an n-type semiconductor with low carrier mobility, carrier density and Hall coefficient, while the LaTiO₃/SrTiO₃ thin film exhibits a metallic conductivity with high carrier mobility, carrier density and Hall coefficient. TEM characterizations reveal that both films are epitaxial and the densities of domain boundaries are similar. However, the LaTiO₃/SrTiO₃ interface is coherent, suggesting that the LaTiO₃ film undergoes a strong compressive strain induced by the SrTiO₃ substrate. On the contrast, the LaTiO₃/LaAlO₃ interface is a semi-coherent interface and the strain in the LaTiO₃ film is released due to the formation of misfit dislocations. XPS and EELS analyses suggest that both films comprise Ti³⁺ and Ti⁴⁺ ions but the LaTiO₃/SrTiO₃ thin film has a higher concentration of Ti⁴⁺ ions. EDS measurements reveal that the LaTiO₃/SrTiO₃ thin film contains ~2 at.% Sr due to the Sr diffusion from the substrate. These results suggest that the high compressive strain and the elemental doping of Sr in the LaTiO₃/SrTiO₃ thin film should be the structural origin for the insulator-metal transition.

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LaTiO3薄膜中绝缘体-金属过渡的结构起源

LaTiO3是一种典型的钙钛矿Mott-Hubbard绝缘体，具有丰富的电性能。极小的带隙有利于金属-绝缘体过渡，电性能易于控制。本文研究了脉冲激光沉积在不同衬底上制备的LaTiO3薄膜的电学性能和微观结构。霍尔效应测量结果表明，LaAlO3薄膜具有低载流子迁移率、低载流子密度和低霍尔系数的n型半导体，而lao3薄膜具有高载流子迁移率、高载流子密度和高霍尔系数的金属导电性。TEM表征表明，两种薄膜均为外延薄膜，且畴边界密度相似。然而，LaTiO3/SrTiO3界面是一致的，这表明LaTiO3薄膜经历了SrTiO3衬底引起的强压缩应变。相反，LaAlO3 / LaTiO3界面是半相干界面，由于失配位错的形成，LaAlO3膜中的应变被释放。XPS和EELS分析表明，两种薄膜都含有Ti3+和Ti4+离子，但LaTiO3/SrTiO3薄膜的Ti4+离子浓度更高。EDS测量表明，该薄膜中含有~2 at。% Sr由于Sr从衬底扩散。这些结果表明，高压缩应变和Sr元素在LaTiO3/SrTiO3薄膜中的掺杂可能是绝缘体-金属转变的结构根源。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Materials Characterization 工程技术-材料科学：表征与测试

CiteScore

7.60

自引率

8.50%

发文量

746

审稿时长

36 days

期刊介绍： Materials Characterization features original articles and state-of-the-art reviews on theoretical and practical aspects of the structure and behaviour of materials. The Journal focuses on all characterization techniques, including all forms of microscopy (light, electron, acoustic, etc.,) and analysis (especially microanalysis and surface analytical techniques). Developments in both this wide range of techniques and their application to the quantification of the microstructure of materials are essential facets of the Journal. The Journal provides the Materials Scientist/Engineer with up-to-date information on many types of materials with an underlying theme of explaining the behavior of materials using novel approaches. Materials covered by the journal include: Metals & Alloys Ceramics Nanomaterials Biomedical materials Optical materials Composites Natural Materials.