Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan, Republic of China.
ACS Appl Mater Interfaces. 2013 Mar;5(6):2269-77. doi: 10.1021/am400128e. Epub 2013 Mar 14.
The surface formation oxide assists of visible to ultraviolet photoelectric conversion in α-In2Se3 hexagonal microplates has been explored. Hexagonal α-In2Se3 microplates with the sizes of 10s to 100s of micrometers were synthesized and prepared by the chemical vapor transport method using ICl3 as a transport agent. Many vacancies and surface imperfection states have been found in the bulk and on the surface of the microplate because of the intrinsic defect nature of α-In2Se3. To discover physical and chemical properties and finding technological uses of α-In2Se3, several experiments including transmission electron miscopy (TEM), X-ray photoelectron spectroscopy (XPS), surface photovoltage (SPV), photoluminescence (PL), surface photoresponse (SPR), photoconductivity (PC), and thermoreflectance (TR) measurements have been carried out. Experimental results of TEM, XPS, SPV, PL, and SPR measurements show that a surface oxidation layer α-In2Se3-3xO3x (0 ≤ x ≤ 1) has formed on the crystal face of α-In2Se3 in environmental air with the inner layer content close to In2Se3 but the outermost layer content approaching In2O3. The near band edge transitions of α-In2Se3 microplates have been probed experimentally by TR and PC measurements. The direct band gap of α-In2Se3 has been determined to be 1.453 eV. The SPV result shows a maximum quantum efficiency of the surface oxide α-In2Se3-3xO3x (0 ≤ x ≤ 1) that presents a peak photoresponse near 2.18 eV. The analyses of SPV, SPR, PL, TR, and PC measurements revealed that the surface oxide layer facilitates the conversion of the ultraviolet to the visible range while the native defects (Se and In vacancies) sustain photoconductivity in the near-infrared region. On the basis of the experimental results a wide-energy-range photodetector that combines PC- and SPR-mode operations for α-In2Se3 microplate has been made. The testing results show a well-behaved function of photoelectric conversion in the near-infrared to ultraviolet region via the auxiliary forming of surface oxide on the crystalline face of the α-In2Se3 microplates.
已经探索了在 α-In2Se3 六方微板中表面形成的氧化物对可见到紫外光电的转换的辅助作用。使用 ICl3 作为传输剂，通过化学气相传输法合成并制备了尺寸为 10 到 100 微米的数十个的六方α-In2Se3 微板。由于α-In2Se3 的固有缺陷性质，在微板的体中和表面上发现了许多空位和表面缺陷状态。为了发现α-In2Se3 的物理和化学性质并找到其技术用途，进行了包括透射电子显微镜（TEM）、X 射线光电子能谱（XPS）、表面光电压（SPV）、光致发光（PL）、表面光响应（SPR）、光电导（PC）和热反射率（TR）测量在内的多项实验。TEM、XPS、SPV、PL 和 SPR 测量的实验结果表明，在环境空气中，在α-In2Se3 的晶面上形成了一层表面氧化层α-In2Se3-3xO3x（0≤x≤1），其内层含量接近 In2Se3，但最外层含量接近 In2O3。通过 TR 和 PC 测量实验探测了α-In2Se3 微板的近带边跃迁。确定α-In2Se3 的直接带隙为 1.453 eV。SPV 结果表明，表面氧化物α-In2Se3-3xO3x（0≤x≤1）的最大量子效率在 2.18 eV 附近呈现出峰值光响应。SPV、SPR、PL、TR 和 PC 测量的分析表明，表面氧化层有助于将紫外线转换为可见光范围，而本征缺陷（Se 和 In 空位）则在近红外区域维持光电导性。基于实验结果，为α-In2Se3 微板制作了结合 PC 和 SPR 模式操作的宽能区光电探测器。测试结果表明，通过在α-In2Se3 微板的晶面上辅助形成表面氧化物，在近红外到紫外区域实现了良好的光电转换功能。
