The Optoelectronic Properties of CVD grown MoS2 Nanowalls

Ankit Sharma, Avinash Nayak, Rudresh Ghosh, Hsiao-Yu Chang

Abstract


Two-dimensional materials, such as graphene, have garnered interest from the research community for their wide-ranging electrical properties and prospective applications. One such material, molybdenum disulfide (MoS2), is a transition metal dichalcogenide composed of stacked quasi-two-dimensional sheets of molybdenum covalently bonded with two sheets of sulfur above and below it. These layers are separated by weak van der Walls forces along the c-axis of its crystal system, making the properties of MoS2 anisotropic. MoS2 has shown potential as a photodetector in its monolayer, bilayer, and multilayer analogs. Here we show the potential of another structure, MoS2 nanowall, to have a high optical absorption allowing for its use in optoelectronics. These rare nanowall structures, grown by a vapor transport method, are composed of MoS2 layers of various thicknesses growing perpendicularly to the substrate. To examine these structures in greater detail we employed photoluminescence measurements, Raman spectroscopy, and scanning electron microscopy with cross-section x-ray microanalysis. Our photoluminescence measurements indicate a bulk material and an indirect bandgap. The presence of the E12g and A1g Raman modes indicate MoS2. Microscopy confirms the presence of well-ordered, layered nanostructures. Here, we will demonstrate the applications of the as-formed nanowalls as an efficient photodetector. Our nanowall photodetectors exhibit broadband photogains and a distinct light trapping behavior. We credit these characteristics to nanowall properties of lower optical reflectance. The photoconductive gain and interesting behaviors of MoS2 nanowall paves way for the potential uses of novel nanostructures in high-performance photonics.


Keywords


Nanowalls; MoS2; Band Gap; Light Trapping; Optoelectronics

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