Impact of Different Morphological Structures on Physical Properties of Nanostructured SnSe

Abstract

Nanostructured SnSe samples with specific morphologies like rods, rod-flowers, flakes, and flake-flowers were synthesized using the same reactants but with a control over various growth parameters involved in a hydrothermal reaction process. The morphology and detailed microstructure of the obtained samples have been studied by means of field-emission scanning electron microscopy (FE SEM) and high resolution transmission electron microscopy (HR-TEM). The sample quality, homogeneity, and phase purity have been thoroughly studied by selective area electron diffraction (SAED) and X-ray diffraction (XRD) analysis. Crystal structure study by refinement of powder XRD profiles using the least-squares fitting strategy indicates all samples to be pure single phase and provides its lattice parameters. The impact of changing morphology on the electrical, optical, and sensing properties of SnSe has been systematically evaluated. Temperature dependent electrical transport measurements highlight the increasingly 2D nature of the nanoflakes, while the lowest resistivity is obtained for nanorods. The mechanism for charge transport shows a crossover from thermally activated band conduction to a Coulomb interaction induced localization of charge carriers. The optical gap energy and absorbance profile also show a morphology dependent response, as monitored using ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy. Resistive sensors for humidity sensing application show quite high sensitivity (∼1500%), good repeatability, low hysteresis in the absorption-desorption process, and good reproducibility at room temperature. Among different SnSe samples, the rod morphology gives the best sensing performance. © 2018 American Chemical Society.