Study On The Preparation And Properties Of Graphene Electronic Devices Based On The Photoreduction Of Graphene Oxide

At the end of 2004,A.K.Geim,a scientist from the University of Manchester in England,cut graphite into pieces during pencil sharpening and obtained two-dimensional and single-atom thick carbon crystals by repeated tearing,which was named as graphene.Subsequently,researchers all over the world found that graphene has many exceptional physical and chemical properties,such as very high carrier mobility(greater than 10~4 cm~2/V·s),good mechanical strength,transparence,conductivity,quantum Hall effect at room temperature and biocompatibility.These unique properties of graphene make it widely studied in the fields of hybrid materials,transparent electrodes,lithium ion batteries,super capacitors,organic photovoltaics,field effect transistors,high-sensitive sensors and so on.Especially,as a kind of transparent electrode material,graphene film has excellent mechanical strength,high transparency,excellent flexibility and good conductivity.Graphene can well replace the metal electrode and the traditional ITO conductive glass because it can overcome the disadvantages of expensive cost,bad transparency and not being able to bend repeatedly.For metal-based electrodes,the transparency is not good,and they also suffers from poor flexibility.For thin ITO electrode,shortcomings including the lack of indium content,poor acid-base stability,unstable resistance that increases with bending degree and other issues significantly restrict their applications.Besides,graphene can also serve as semiconductor materials upon suitable treatment,graphene also shows electric field effect,high electron mobility,good flexibility and stability,which make it excellent candidate for developing field effect transistors.These advantages of graphene FETs can overcome the shortcomings of organic semiconductor-based OFET and TFT devices,and show a dramatic improvement in the two aspects of electron mobility and stability,bringing about a revolutionary change for the development of flexible driving circuits.However,graphene is a zero bandgap semiconductor,tailoring its bandgap through a controlled manner is of great importance for developing graphene-based electronics.In this paper,we use graphene oxide as starting materials.We further tune their properties through controllable photoreduction strategies,various light sources including the sun light,camera flash and femtosecond lasers have been employed for reduction of GO.The photoreduction methods reveal several advantages such as chemical-free treatment,fast and effective reduction of graphene oxide,flexible patterning and structuring,which helps for preparation graphene-based electronics such as field-effect transistors and moisture-sensitive sensors.The main research contents are listed as follows:1.We studied the fabrication of flexible field-effect transistors(FETs)by sun light reduction of graphene oxide and discussed the mechanism of solar photoreduction of graphene oxide.At the same time,reduction degree was investigated by XPS and other methods.Performance test results show that the on/off ratio of the resultant FET can reach 111;the hole mobility is 0.17 cm~2/V·s,which is much higher than those RGO-based FETs prepared by other photo reduction strategies.Compared with other GO photo reduction protocols,the solar reduction method is simple,convenient and effective,and is suitable for low-cost production of graphene-based electronic devices.2.We studied the femtosecond laser processing of all graphene field-effect transistors on flexible substrates.Using femtosecond laser direct writing technology,we patterned the all-carbon flexible field-effect transistor(FET)device by tuning the laser intensity.Femtosecond laser direct writing of graphene oxide enables effective reduction of GO.By tuning the oxygen content,the bandgap and the conductivity can be modulated.,at the same time by XPS and other means of characterization femtosecond laser direct writing reduction of graphene oxide reduction degree,after the device performance test,we have the switch ratio of 2.04,the hole mobility of0.27 cm~2/V·s FET devices to achieve the graphene oxide device preparation process controllable reduction conditions,the processing area is optional,the device size is adjustable,flexible and variable pattern.3.We introduced the production of high-performance humidity sensors by flash-reduced of graphene oxide,and described the mechanism of flash-reduced graphene oxide.The XPS and other characterization methods confirmed the removal of oxygen groups on graphene oxide sheets.In the test of device performance,the humidity sensor shows high sensitivity and fast response.We deem that the flash photoreduction of GO film may find broad application in eco-friendly wearable computers,human–machine interaction and smart robots.In summary,we have investigated the core technology fabricating graphene-based electronic devices using graphene oxide as starting materials.Systematic research on photo reduction of graphene oxides lays a solid technical foundation for the development of graphene-based flexible electronics.