多元透明导电氧化物的能带调控与电子输运特性研究

Transparent Conductive Oxides (TCOs) display versatile optoelectronic properties that originate from the variety of crystal structure and constituent elements. However, the application of TCOs is hindered by the absence of the low-cost n-type conductivity and the high p-type conductive materials. So we emphasize this investigation on modulations of charge transport and bandstructure of TCOs. We employ strategies of theoretical simulation followed by experimental fabrication and measurements to explore the multi-component oxides (MTCOs). The initial pool of MTCOs is made up of various impurity-doped In2O3 (IMTO, M=Zn, Cu, Cd, Mg, Ni, Al and Ga etc.）and A2B2O3 (A=K、Na, B=Sn、Pb) materials. We aim to find key factors to modulate the fine bandstructure of TCOs via modifying the geometric structures, such as constituents, local symmetry and strains etc.. Thus we could make clear how to increase the dispersion of bandstructures for TCOs materials. We predominantly study affections on bandstructures produced by hybridizations of various atomic orbitals in the crystalline lattice, and then explore the variations of carrier effective masses and the optical band gap of MTCOs accordingly. Finally we expect to obtain the theoretical model of bandstructure modulation for MTCOs. Based on these models, we plan to design the appropriate fabrication methods for MTCOs utilizing the inverse design approach, which could be helpful in the applications of TCOs in solar cell and touch panel displayers etc. The theoretical simulations adopt HSE+G0W0+BSE approach to analyze the fine near band structure induced by exitons. The experimental investigations are performed by means of radio frequency magnetron sputtering methods and other measurements approaches.

透明导电氧化物（TCOs）因晶格结构和组分元素变化多样而呈丰富的电磁特性，但价格低廉的n型和导电率高的p型TCOs难以获得。我们将研究TCOs的突破口置于对其能带结构和输运特性进行调控上面。采用理论模拟为先导、以实验表征为支撑的方法，选择IMTO（M=Zn、Cu、Cd、Mg、Ni、Al和Ga等）、A2B2O3（A=K、Na，B=Sn、Pb）为代表的多元透明导电氧化物（MTCOs），通过调整几何结构（化学组分、晶格对称性、应力等），寻找调控MTCOs的能带精细结构和增加其带边发散性的关键因素，重点研究晶格内部原子轨道间的杂化作用对能带结构的影响，进而分析载流子的有效质量和材料的光学带宽的变化，建立MTCOs能带调控的理论模型。以此为基础由反向物性设计法获取优良MTCOs的制备方法。我们使用HSE+G0W0+BSE方法精确描述由束缚激子引起的带边精细结构，使用磁控溅射法制备MTCOs。

透明导电氧化物（TCOs）因其晶体结构和组分元素变化多样而呈现丰富的电磁特性，被广泛应用于平板液晶显示、薄膜晶体管和印刷电路等领域中。本项目使用组分替换、相变等手段调控基于In2O3的透明导电材料的光电特性。通过几何结构、电子结构的理论分析发现Zn/Sn共掺可提高In2O3中杂质的掺杂比例，降低In的含量，并且能够降低导带底部的空间局域性和轨道局域性，这些都有利于载流子的产生和传输。其它的杂质掺杂形成的IMTO（In-M-Sn-O系统，M=Zn，Ga和Hg）也能够有效降低材料载流子的有效质量和空间、轨道局域性。实验制备了IZTO(In-Zn-Sn-O)-TFT，其迁移率达到17.53cm2V-1s-1，Ion/off为106。制备了ITO/AZO复合薄膜，发现其在近红外光谱区的透过率有很大的提高。本项目提供了一种可替代ITO的材料制备方案，更有利于TCOs朝低成本和高性能方向的发展。研究了以NiO为代表的p型TCOs，我们制备的NiO:Cu材料的空穴迁移率最高可达45cm2V-1s-1，制成的NiO同质p-n节的电学性能优良。研究了半导体材料中载流子的散射机制，分析了在钙钛矿材料中声子散射对载流子迁移率的影响。使用理论模拟的方法对材料载流子的有效质量随温度的变化关系作了研究，发现载流子的迁移率或者其所遭受的散射并能不简单的套用某一种模型的公式就可以描述，必须结合材料的晶格结构和晶格振动做具体、合理的分析，尤其是要注意载流子的有效质量随温度变化这一现象。本项目的研究成果能有力的促进多元透明导电材料的进一步发展。本项目共发表SCI收录论文13篇。