Anisotropy in the optical and electrical properties of many transition metal dichalcogenides provides a great variety of possibilities for device applications. The present work attempts to exploit the anisotropy in photoresponse of pure and Co-incorporated WSe₂ crystals. Energy-dispersive analysis of X-rays affirmed the elemental composition of the crystals grown by the direct vapour transport technique. The surface morphology of the crystals was studied by optical microscopy and scanning electron microscopy, both of which confirmed the layered structure of the same. Layers of the samples and the lattice fringes were concluded under high-resolution transmission electron microscopy. The crystalline nature and hexagonal phase of the crystals were confirmed from X-ray diffraction, further highlighted in the results observed from the selected area electron diffraction pattern. Anisotropic charge conduction properties under illumination due to the layered structure of the sample were analysed. The anisotropy in the photoresponse was confirmed from the current-voltage (I-V) characteristics, which were further explored from its time-dependent photoresponse. The crystals proved to be self-powered photodetectors with higher values of photocurrent (μA), photoresponsivity (μAW⁻¹) and photodetectivity (~10⁷-10⁸ Jones) recorded for contacts taken parallel to the crystallographic c-axis of the crystals. The effect of Co in improving the photoconductivity of WSe₂ has been analysed based on the photoresponse recorded for pure and Co-incorporated WSe₂. The present work also illustrates the effect of intensities of illumination and wavelengths of incident radiations in the photocurrent. Photocurrent in μA range observed in the absence of biasing voltage makes the crystals suitable candidates for self-powered photodetection applications.

中文翻译：

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掺钴二硒化钨三元合金瞬态可见光各向异性光响应的增强

许多过渡金属二硫属化物的光学和电学性质的各向异性为器件应用提供了多种可能性。目前的工作试图利用纯和共掺 WSe _{2的光响应中的各向异性}晶体。X 射线的能量色散分析证实了通过直接蒸汽传输技术生长的晶体的元素组成。通过光学显微镜和扫描电子显微镜研究了晶体的表面形貌，两者都证实了晶体的层状结构。在高分辨率透射电子显微镜下对样品层和晶格条纹进行了总结。通过 X 射线衍射证实了晶体的结晶性质和六方相，在从选区电子衍射图中观察到的结果中进一步突出。分析了由于样品的层状结构在光照下的各向异性电荷传导特性。光响应中的各向异性由电流 - 电压（IV) 特征，从其时间相关的光响应中进一步探索。晶体被证明是自供电光电探测器，具有较高的光电流 (μA)、光响应性 (μAW ^-1 ) 和光电探测率 (~10 ⁷ -10 ⁸ Jones)，记录平行于晶体的晶体学c轴的接触。_{Co 对 WSe 2}光电导率的改善作用已基于纯和 Co 掺入的 WSe _{2记录的光响应进行了分析。}. 目前的工作还说明了光电流中照明强度和入射辐射波长的影响。在没有偏置电压的情况下观察到的 μA 范围内的光电流使晶体成为自供电光电探测应用的合适候选者。