重离子辐照调控p型透明氧化物半导体CuAlO2薄膜缺陷及其热电性能研究

P-type transparent oxide semiconductors (TOS) CuAlO2 film is a promising candidate for transparent thermoelectric devices due to its transparency and excellent thermoelectric properties in theory. However, its thermoelectric performance is far from the theoretical prediction since the charge carrier concentration and phonon scattering in CuAlO2 films could not be modulated simultaneously. Heavy ion irradiation is believed to be an effective strategy to address this issue. The thermoelectric performance of CuAlO2 films will be significantly improved by increasing defect concentration and decreasing film density. In this project, heavy ions are proposed to irradiate CuAlO2 transparent films for creating defects. We aim to enhance the power factor and ZT value of the CuAlO2 films. A series of investigations will be performed on the irradiation effects by varying experimental parameters, including ion species, ion energy, intensity and dose. The comprehensive study is accomplished on the changes of defect concentration, film density, morphology, structure, transparency and electrical conductivity, especially the thermoelectric properties of the CuAlO2 films. The irradiation effect of heavy ions on CuAlO2 films will be concluded through a comparative study on the irradiated and unirradiated samples. The connections between defect concentration, film density and thermoelectric properties will be built. The intrinsic physical mechanisms are clarified in the connections. It will provide a reliable technical and theoretical support for the thermoelectric improvement of p-type TOS films. Moreover, the proposed project will also generate a design guideline of transparent thermoelectric devices.

p型透明氧化物半导体（TOS）CuAlO2薄膜具有优异的理论热电性能，是实现透明热电器件的重要候选材料，但实验结果与理论计算相差甚远，主要源于载流子浓度和声子散射无法被同时有效调控。重离子辐照技术可解决上述难题，通过增大缺陷浓度、降低薄膜密度，共同改进p型TOS-CuAlO2薄膜热电性能。本项目提出采用重离子辐照CuAlO2透明薄膜可控构造缺陷，显著提升CuAlO2薄膜的功率因子和热电优值ZT值。通过改变辐照参数，包括离子种类、离子能量、流强大小、辐照剂量等，深入系统研究CuAlO2薄膜缺陷浓度、薄膜密度对样品形貌、结构、透明性、导电性，特别是热电性能的调控规律。通过比较辐照前后CuAlO2薄膜热电性能变化，构建微观缺陷、薄膜密度与宏观热电性能间的物理关联性，澄清内在物理机制。为p型TOS薄膜的热电应用提供可靠的理论依据和技术支持，开展本项目研究具有非常重要的科学意义和应用价值。

p型CuAlO2薄膜在透明热电器件领域有着潜在的应用前景，缺陷工程和薄膜密度调控是改善其热电性能的重要手段。利用重离子辐照技术调控热电薄膜的载流子浓度和声子散射具有天然优势。本项目中，我们在已有CuAlO2薄膜研究基础上，首先利用SRIM程序进行辐照模拟，然后运用不同种类、不同能量的重离子辐照未掺杂和掺杂CuAlO2薄膜，揭示CuAlO2薄膜结构、透明性、导电性、热电性能变化的物理规律和内在机理。.在中科院近物所兰州重离子加速器（HIRFL）大型研究平台上，对Ni掺杂CuAlO2薄膜进行300 MeV/u的氪离子脉冲式辐照研究，发现Ni掺杂和CuO相的存在抑制了CuAlO2薄膜在快速重离子辐照下的非晶化，降低了CuAlO2薄膜的表面粗糙度，掺杂薄膜表现出更高的透明性（74%）和更低的电阻率（11.5Ωcm），辐照增强了薄膜的光敏性，这些结果主要归因于高能离子的热尖峰效应。与高能离子辐照相比，中低能离子持续性辐照的效果相对稍弱，但更适合CuAlO2薄膜热电性能的调控。理论研究发现CuAlO2薄膜中的空穴载流子浓度在1.90×1020 cm-1时可获得较理想的塞贝克系数，载流子浓度太高不利于热电性能。.在中科院近物所320KV高压平台上利用1 MeV/u的Fe10+辐照CuAlO2薄膜，研究发现薄膜电导率提高了200倍，室温塞贝克系数达到190 μV K-1，功率因子为9.15μW m-1K-2，且薄膜透光率仍高于60%。在CuAlO2薄膜中进行Fe掺杂和Ag、Fe共掺杂，再进行1 MeV/u的Fe10+辐照的技术路线，发现掺杂工程和重离子辐照的综合运用，实现了CuAlO2热电薄膜室温塞贝克系数达到412 μV K-1，573 K时的功率因子为105 μW m-1 K-2，ZT值为0.023的预期目标。热电性能的改善主要是由于辐照薄膜中铜空位缺陷的增加和薄膜密度的降低，且未显著降低薄膜结晶度。这为改善半导体薄膜的热电性能提供了一种很有前途的策略。.另外，在本项目支持下利用MWCNTs/CuAlO2复合策略，将CuAlO2块材的导电性提升了三个数量级，在1 wt.% MWCNTs掺杂样品中得到了较好的常温热电性能，有效拓展了CuAlO2材料在热电领域的使用范围。中科院近物所的合作者成功研制了用于医用重离子加速器的碳剥离膜等工作。