Modulating Optoelectronic Performance Of MoSe₂ And WSe₂ Field Effect Transistors

Two-dimensional transition metal dichalcogenides(TMDs)have aroused great scientific interest due to their unique structures and properties.Molybdenum selenide(MoSe₂)and tungsten selenide(WSe₂)are N-type and P-type transition metal disulfides,respectively,and they have been proved to be ideal materials for electronic and optoelectronic devices.Studies have found that the performance of two-dimensional materials is greatly affected by factors such as the number of layers and defects.However,the photoelectric properties of intrinsic two-dimensional materials need to be improved.Therefore,in this paper,multilayer MoSe₂ and multilayer WSe₂ are used as the research objects to prepare photodetectors,through the introduction of oxygen defects and other methods adjust the performance of optoelectronic devices.Finally get a high-performance photodetector.The main work and conclusions of this paper are as follows:(1)The MoSe₂ field effect tube was successfully prepared by mechanical peeling method and electrode transfer technology,and the intrinsic materials were characterized by Raman spectroscopy,photoluminescence spectroscopy;we also poerformed the characterization of electrical and optical properties.The experimental results show that the contact resistance between the multilayer MoSe₂and the metal electrode is large,the photoresponse rate is low,and the lowest detection power of the original device is only 7n W.(2)Optoelectronic properties of MoSe₂ are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerably increase of electron and hole mobilities reveal the highly improved electron and holetransport.Furthermore,the photocurrent is enhanced by near four orders of magnitudes under 7n W laser exposure after annealing.The remarkable enhancement in the photoresponse is attributed toan increase in hole trapping centers and a reduction in resistance.Besides,the annealed photodetector shows a fast time response on the order of 10ms and a responsivity of3×10⁴A/W,the minimum detection of the device is from the lowest 7n W to the lowest 0.22p W.Finally,we tried to use hydrogen peroxide and gold chloride solution to control the device by hole doping effect,the photoelectric performance was also improved to a certain extent.(3)We have achieved a high performance multilayer WSe₂ phototransistors with both a fast response time and a high responsivity.This performance is achieved by introducing oxygen defects through annealing under air atmosphere,which is characterized by Raman spectroscopy and photoluminescence(PL)spectroscopy.Electrical measurement shows a p-type doping effect in WSe₂ after introducing oxygen defects.In addition,the hole mobility of WSe₂ is increased by 420 times,revealing the highly improved hole transport in the WSe₂ channel.Specifically,WSe₂transistors exhibits high responsivity up to 2.27A/W under 532nm laser and 0V gate voltage,and a time response on the order of tens of ms after annealing.The remarkable enhancement in the photoresponse is attributted to defect trapping and photogating effect.This technique could also be applicable to different 2D materials to realize high performance photodetector.