Preparation Of Graphene/copper Composite Nanosheets And Their Applications For Fabricating Field Effect Transistor

Since the discovery of graphene,due to its high carrier mobility at room temperature,it has a wide range of application in electronic devices.However,graphene is a zero band gap semiconductor.When it is used in logic circuits,especially in field effect transistor(FET),the current switching ratio is small.On the other hand,due to different preparation methods to graphene and manufacturing processes,the actual carrier mobility is low,which leads to the failure of FET to meet the normal working requirements.Since the discovery of graphene,it has been widely used in electronic devices because of its high carrier mobility at room temperature.However,graphene is a semiconductor whose bandgap is zero.When it is used in logic circuits,especially in FET,the current switching ratio is small.On the other hand,due to different graphene preparation methods and manufacturing processes,the actual carrier mobility of graphene is low,which is hard for graphene FET to meet the normal working requirements.In this paper,graphene/copper composite nanosheets was successfully prepared by thermal decomposition of copper oleate in oleic acid under a protective atmosphere.It was found that the composite had a certain band gap.By changing the thermal decomposition condition,the influence of different conditions on the composite was studied.The growth mechanism of the composite was analyzed.Then,the properties of the composite were studied by optical and electrical characterization.Based on the preparation and performance research,the composite was applied to the back-gated FET,and the electrical property of the device were characterized and analyzed.First of all,the products of thermal decomposition were studied under four conditions:the thermal decomposition temperature,holding time in maximum temperature,the heating rate and the different solvents.The results showed that the copper oleate in oleic acid was decomposed into graphene and copper nanosheet composite.When the thermal decomposition temperature reached 250?,compared with other temperature,the maximum size of the nanosheet could reached 16?m.The average size could reach 8?m.And the morphology was mainly complete and triangular.The composite with larger size could be obtained by prolonging the maximum temperature holding time and decreasing the heating rate.The composite with centimeter size could be obtained through the thermal decomposition of 1:1mixture of copper oleate in octanol and oleic acid solvent at 250?.According to the results of characterization,the growth mechanism of the composite was explained.But further research was still needed through other characterization methods.Secondly,the optical and electrical properties of the composite were studied.In the fluorescence spectrum,when the excitation wavelength was about 350 nm-420 nm,the composite had strong fluorescence characteristics.In the ultraviolet visible spectrum,the composite had a strong absorption at 406 nm,indicating that the composite has a certain bandgap.The copper oleate in oleic acid was decomposed on the surface of the copper film.The results of I-V test showed that the composite had certain semiconductor property.Finally,based on the performance characterization of the composite,the back-gated FET was fabricated by using the composite prepared at 250?as the channel material.The device was electrically characterized when the gate dielectric layer(Si O₂)thickness was 80 nm-140 nm,.The results showed that the resistance of the channel was large without gate voltage and the source drain current was only?A level.The current from drain to source reached A level even if the gate voltage was only 1 V.In this condition,the current amplification was more than 2000 times,which realized the current amplification function at a small voltage.When the voltage from drain to source was constant,the maximum switch ratio of the device was 71 with the change of gate voltage.Compared with the large area graphene FET,the switch ratio is relative large.