Optoelectronic properties of graphene quantum dots with molybdenum disulfide
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.50
Optoelectronic properties of graphene quantum dots with molybdenum disulfide Misook Min1, Gustavo A. Saenz1,2, and Anupama B. Kaul1, 2* 1
Department of Materials Science and Engineering, PACCAR Technology Institute, University of North Texas, Denton, TX 76207, USA 2
Department of Electrical Engineering, University of North Texas, Denton, TX 76207, USA *Corresponding Author Email: [email protected]
ABSTRACT
The presence of a direct optical bandgap in the transition metal dichalcogenide (TMD) layers leads to promising applications in optoelectronic devices such as phototransistors and photodetectors. These devices are commonly fabricated using few-layer and monolayer MoS2 sheets obtained using mechanical exfoliation or chemical vapor deposition techniques. The hybrid structure of quantum dots (QDs) and 2D materials has been investigated to provide outstanding properties for various applications. Herein we report the fabrication of a hybrid QDs/MoS2 photodetector consisting of graphene quantum dots (GQDs) and multilayer MoS2 sheets. The hybrid GQDs and MoS2 films are characterized by atomic force microscopy (AFM); additionally, the I-V characteristics are measured by two-point probe station.
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INTRODUCTION Among the various TMD materials [1,2], Molybdenum disulfide (MoS2) primarily represents n-type semiconductor. While it exhibits an indirect bandgap (1.2 eV) in bulk form, it possesses a direct bandgap (1.8 eV) in monolayer form. Such characteristic enables its applications in photo-electronics such as photocatalysts and phototransistor devices [3-10]. Monolayer MoS2 demonstrated mobility of ~0.1-10 cm2V-1s-1 and on/off ratios of 108 at room temperature [11-12]. Also, a hybrid phototransistor using 2D materials and quantum dots has been reported to show higher gain and optical sensitivity than a phototransistor using only 2D materials [13-14]. Here we present a quantum dots/MoS2 photodetector consisting of graphene quantum dots (GQDs) and multilayer MoS2 sheets. Our hybrid GQDs/MoS2 photodetectors are fabricated by facile method to show a high photo-responsive property. EXPERIMENTAL DETAILS Graphene quantum dots (GQDs) were synthesized according to previously reported procedures [15]. They were characterized by atomic force microscopy (AFM, Bruker Multimode 8 AFM with Nanoscope V controller). The MoS2 flakes used in this study were exfoliated from a bulk MoS2 crystal (2D Semiconductor Inc.) using the mechanical exfoliation method. The multilayer MoS2 flakes were transferred to a p-doped Si substrate with a 270 nm thick SiO2. Conventional optical photolithography (Karl Suss MJB-3 mask aligner) was used to pattern electrodes on the MoS2 flakes on the SiO2. The residual photoresist was remove
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