Morphologically controlled photodetector performance of molybdenum disulfide nanostructures

The objective of this work is to control the morphology of molybdenum disulfide nanostructures using hydro-thermal technique for improving the visible-light photodetector performance. The morphology comprises nanosheets with dimensions and packing density that are dependent on the synthesis temperature. As the syn-thesis temperature increases from 170 to 210 degrees C, the dimensional change of nanosheets is accompanied by increased packing density, as confirmed from scanning and transmission electron microscopy images. The dark current increases from 0.9 to 1.18 & mu;A while the bright current increases from 78.57 to 112.59 & mu;A as synthesis temperature increases from 170 to 210 degrees C. In addition, there is an improvement in all other parameters such as sensitivity, responsivity and detectivity of the photodetector with increase in synthesis temperature. The MoS2 based photodetectors revealed an ultrahigh sensitivity and responsivity of 95% and 11.25 mA/W, very high detectivity of 0.11 x 1011 Jones and fast rise-time and fall-time of around 0.5 and 0.7 ms respectively. X-ray diffraction and x-ray photoelectron spectroscopy studies reveal that there is no change either in the crystallo-graphic texture or stoichiometry of the samples with change in morphology. It is, thus concluded that improved photodetector performance is entirely morphological in origin. The present work represents a facile method based on morphological control to improve the visible light photodetector performance of MoS2 nanostructures.