Graphene Nanowalls And Its Applications In Photodetector

Photodetectors have a wide applications in military and civilian,in the field of military are used for remote sensing,night vision,missile guidance and for smoke alarm,health care,security in civilian.GNWS is a three dimensions?3D?materials which exhibit excellent optical and electric performance,can be synthesized both in large area and low cost,making it a promising candidate in the application of photodetector.In this thesis,we have a particular investigation on Graphene nanowalls and its performance of photoelectricity.The detail researches are following:Part one:The synthesis and characterization of GNWS.Different height of GNWS is obtained by a RF-PECVD method with controlled gas ratio,growth temperature and growth time.GNWS is synthesized both on copper and silicon substrate.The surface morphology,structure,optical absorption are characterized by SEM,AFM,Raman spectrum and infrared spectrum.Part two:The transfer process of GNWSThe way of transferring GNWS is similar to graphene,a PMMA-free method is adopted here because GNWS is robust than graphene,which no need to be protected.Otherwise,a relative moderate etchant APS is choose to etch copper.For an easy transfer,substrates is treated with oxygen plasma or UV Ozone to shift Hydrophobicity.Part three:The investigationof polymer flexible substrates and GNWS composed device.Device with different temperature coefficient of resistance?TCR?is obtained by transferring GNWs on three substrates with different coefficient of thermal expansion?CTE?,including silicon,PET and PDMS.For PDMS/GNWS device,it owns anomalous TCR of 180%/K and relatively high current change rate of 16%under body infrared radiation.It primarily attribute to the ultra-high infrared absorption of the GNWSs and large CTE of PDMS.In addition,the GNWSs/PDMS device possesses excellent detection performance in infrared?IR?region with a responsivity of¹.15mA/W.The calculated detectivity is up to 1.07×10⁸ cmHz^1/2W^-1,which is one or two orders of magnitude larger than that of the traditional carbon-based infrared detector.As for flexibility,a repeated bending is applied on device,even after 1000 times,performance of device shows no obvious degradation,which is important in practical application.For PET/GNWS device,it shows ability of wideband infrared detect.Meanwhile,it also demonstrated possess great flexibility.There is hardly report about using GNWS as infrared sensor materials,our work indicated that GNWS is potentially utilized in the filed of infrared detect.Part four:The fabrication and research of Si/GNWS based photoconductive deviceGNWS is directly synthesized on different doped silicon substrates,Si/GNWS device with schottky barrier is obtained.Photoelectric response is realized with different height of GNWS and size of channel.Since the smallchannel of GNWS is highly desired,we investigated pattern of GNWS through the platform of semiconductor fabrication.Moreover,gate voltage is applied on the back of silicon to adjust the height of Si/GNWSSchottky barrier,so as to increase the lifetime of carriers.Eventually,gain of device is greatly enhanced as well as the response.