| Two-dimensional molybdenum disulfide(MoS2)has attracted considerable attention owing to its remarkable characteristics including variable band gap,high carrier mobility,and good transmittance.Many of these properties have contributed to its marvelous performance in the field of photodetection.MoS2-based photodetectors with fast response,low noise level,and wide spectrum response have already been demonstrated.Here in this article,we have studied the growth conditions of two-dimensional MoS2 and Molybdenum Selenide(MoSe2)using chemical vapor deposition(CVD)method.Large-scale and high-quality films were synthesized prior to fabrication and investigation of pristine MoS2 photodetector.Later,to improve performance of Photodetectors,heterostructures were fabricated by introducing zinc oxide quantum dots and stacking MoSe2 on MoS2.The Significant highlights of this article are as follows:(1)The large size and high quality MoS2 single crystals were successfully synthesized on sapphire substrates by controlling the growth temperature,time and vapor concentration.MoS2-based photodetectors were fabricated from high-quality single MoS2 crystals by photolithography and thermal evaporation technique.Excellent detectability(1010 Jones),optical switch ratio(over 400)and broadband detection wavelength covering from UV to NIR were demonstrated.The device can work at a low voltage(0.5 V),which consumes less energy than other competitor photodetector devices based on other 2D materials.(2)The Zinc Oxide quantum dots(ZnO QDs)were synthesized by the solution-gel method.By analyzing the quantum dots,it was found that the synthesized QDs were of controllable size,high crystal quality and band gap of 3.42 eV,which are ideal UV detection.Moreover,high-quality MoS2-based photodetectors were fabricated using photolithography and thermal evaporation technique.The performance of the device was Investigated systematically.Finally,ZnO QDs/MoS2 heterostructure photodetector was fabricated by spin coating ZnO quantum dots solution,and its performance was studied and compared with the pristine device.Under the same illumination power,the photocurrent of the heterostructure device is nearly four times higher than that of the pristine device,It is worth noting that the detectability reaches 1011 Jones,and the response/recovery time decreases from 9.5 s and 17.4 s to 1.5 s and 1.1 s.It was confirmed that performances of the device can significantly be improved by introducing of ZnO QDs into the MnS2 pristine devices.We believe that the improvement in Photodetection owes to the band structure of heterostructure.(3)By carefully adjusting the conditions for synthesis process in CVD we successfully obtained large area,high-quality MoS2 and MoSe2 thin films on sapphire substrates.The measured thickness was 4.5 nm,Vertical heterostructures were successfully fabricated on flexible and transparent PET substrates by wet transfer technique,and large-area flexible photodetectors were fabricated by photolithography and thermal evaporation.It was found that the responsivity of the heterostructure device was 1.6 mA/W and the detectivity was as high as 4,42×1013 Jones.The built-in electric field was generated due to the unusual energy band alignment(staggered gap)and effectively separated the photo-generated carriers and device with a photo-voltaic equivalent effect was achieved.Its response and recovery time were only 1.05 s and 2.3 s under zero biased.It is worth mentioning that after multiple bending tests and exposure to air for a month,the responsivity of the device was almost unaffected,which established the reliability and excellent performance of our device. |
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