Study Of Photo-detectors Based On Graphene And Low Dimensional Semiconductors

Electromagnetic waves play important roles in our daily life.Various colours can be captured by our naked eyes,massive information is being receivecd by all kinds of terminal and an X-ray photograph on film can tell if the bones are broken.While taking advantages of electromagnetic waves and doing researches about it,xwe can see the photo-detectors are very crucial to obtain the signals.Tranditional photo-detectors are mostly based on semiconductors which is good photo-absorbers.Photo-signals are converted into electric signals by photo-detectors using photoelectric effect and the electric signals can be detected by amperemeters.In 2004,the rise of graphene broadened the horizon of photo-detectors.Graphene is the thinnest material in the world and it is consisted of one layer carbon atoms as a two dimensional(2D)material.As the first 2D material appeared to our world,graphene owns numerous unique properties such as fast carrier mobility,low carrier density,high mechanical properties,high surface to volume ratio etc.Photo-detectors based on graphene are studied by many scientists.Especially when the discovery of chemical vapor deposition method is coming to our sight,graphene-based photo-detectors are only one step from practical applications.How can we hybrid graphene with other materials and obtain new kinds of photo-detectors is becoming a major topic among all researches.Forcus on this topic,the content of this paper is listed as followed:1.We come up with a wide-spectrum photodetector based on CVD graphene and composite oxide quantum functional materials which can response from visible light to ultraviolet light.In this experiment,this layer number,the composition-adjustable high-level perovskite structure and graphene are combined for the first time,and the ferroelectric layer itself is permanently polarized with the help of the built-in electric field between the substrate and the material.Photogenerated electrons are transferred to graphene with the aid of ferroelectric polarization,which in turn changes the resistance state of graphene.In this paper,the traditional two-layer structure detector was converted into a three-layer structure for the first time.Compared with the control experiment,this three-layer structure increased the photoelectric detection signal by 200 times and was more stable.2.An ultraviolet photodetector based on CVD graphene and anatase single crystal titanium oxide nanosheet array was prepared.As a traditional wide bandgap semiconductor,TiO2 itself has very good UV absorption,and anatase has also been confirmed to have the best photocatalytic effect.In this experiment,the anatase's high Miller index single crystal TiO2 nanostructures were composited with graphene for the first time.The electrical transport properties of graphene and anatase TiO2 at the interface were studied in detail.The data proved that the mutually supportive sheet-like structures have better UV absorption characteristics and are more suitable for the preparation of graphene composite ultraviolet photodetectors.3.We proposed an asymmetrical structure which based on an electric field driven method,to arrange the carbon quantum dots between the graphene electrode arrays.Finally a concentration gradient forms between the graphene electrodes.We used a variety of methods to verify this asymmetric structure in the experiment and studied its electrical properties.The device has very good rectification behaviors,the switching ratio is up to 104,and it is very little affected by the temperature or electric field,etc.,and it has good sensitivity to visible light,the light responsivity can reach 1500 A/W,and it can respond to 2500 Hz of incident light signal.The experiment in this paper has very important significance.It not only produces a multi-functional device with excellent performance,but also provides a simple assembly method,an asymmetrical structure,and an idea of structure control performance.The Final part is for the work summary and outlook,sums up the work of the former chapters,and looks forward to the follow-up work.