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Study On The Graphene/silicon Heterojucntion Photodetectors

Posted on:2016-07-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:M ZhuFull Text:PDF
GTID:1108330503956250Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
Light, as one of the most efficient carrier of information, is a key of modern advanced technologies in information storage and transmission.Photodetectors are commonly used in electrical devices for light detecting.Traditional materials used in photodetec tors are facing various problems such as performance restriction, low reservation, and high environmental pollution. Since the 1990 s, the rapid development of nanomaterials has provided new solution to the problems mentioned above. The emergence of graphene in recent years further brings vitality in the field of photodetection.In this work, heterojunction Schottky diode photodetectors are fabricated by combining silicon with multilayer graphene prepared by chemical vapor deposition(CVD) and reduced graphene oxide(r GO) prepared by thermal reduction of graphene oxide. With a focus on the mechanisms, the improvements in device’s structure and performance are systematically investigated in terms of materials surface and interfaces optimization. r GO/Si Schottky diode photodetector, whichpossesses various merits of simple fabrication, low cost and suitability to mass production is presented. Some drawbacks of CVD based devices,such as high cost and low production efficiency, are well overcome, yet showing better performance comparing with similar devices.Firstly, interfacial modification of the heterojunction istaken into account to approach a remarkable improvement of device performance. A thickness-controllable insulator layer is introduced at the interface between graphene and silicon, resulting in the significant decrease of dark current(about two orders) and strong improvement indetectivity, which are found to be higher than those of previous graphene-planar Si photodetectors. Subsequent systematic investigations of the device model and key detectionparameters show a good linearity of the light intensity response of the device with a linear dynamic range of 90 d B, as well as other excellent performances.Then, from the perspective of the enhancement to light adsorption and energy conversion,a Ti O2 functional layer is further introduced to improve the device photoresponse in ultraviolet region. Under 420 nm and 350 incident lights, the photo-conversion-efficiencies of the device are increased by 72.7% and 100%, respectively, by spin-coating a layer of 100 nm thick Ti O2 nanoparticles on the device surface. Correspondingly, the responsivity and detectivity of the device are also greatly improved. Attribute d to the porous structure of the Ti O2 layer, the performance of the Ti O2 coated device has been further improved by HNO3 vapor processing. C-2-V measurements are then performed to reveal theenhancement mechanism of Ti O2 layer.Finally, based on various merits of r GO in synthesis, functionalization and device fabrication,r GO/Si Schottky diode photodetector is presentedand the effects of the reduction level of r GO are discussed. The r GO/Si photodetector is fabricated by a simple drop-casting and thermal reduction process. As the reduction temperature increases, the responsivity and detectivity of the device at zero bias show an increase tendency with an optimal response time at 400 °C. Relevant mechanisms are discussed based on the oxygen-containing functional groups and structural defects in r GO film. Besides, the characteristics of r GO/Si Schottky diode are systematically investigated according to the temperature dependency. The current response of r GO/Si photodetector show that the photoelectric signals vary apparently for different gases, indicating its application potential in gas identification.
Keywords/Search Tags:Graphene, silicon, heterojunction, photodetector, detectivity
PDF Full Text Request
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