Preparation Of Protective Films On Flexible Graphene/PET Substrates And Investigation Of The Properties Of The Hybrid Films

Transparent conductive film?TCFs?is a kind of important optical and electrical materials,with the transmittance of 74%to 90%within the visible lights?wavelength380-760 nm?and the square resistance of tens of ohms.It is widely used as the front electrodes in solar cells,flat liquid crystal displays,sensors,aircraft windshield glass.Indium tin oxide?ITO?transparent conductive thin film is the widely industrial used transparent conductive thin film.It is expensive due to rare storage of indium,non-flexibility due to its high brittleness.Graphene has the advantages of high conductivity,transparency,thermal properties,high strength,ultra-thin and flexibility.Therefore,flexible graphene transparent conductive film has its promising potential to replace the traditional brittle transparent conductive film.However,graphene is only with a single or double layers of carbon atom and the scratch resistance is not ideal.The scratch may destroy its conductivity.Therefore,it is very important and meaningful to select suitable protective layers on graphene by suitable preparation approaches.The purpose of this paper is to prepare protective layers on the double-layer graphene/PET?dg/PET?substrates,which are able to keep the optical and electrical properties of graphene as well as to protect graphene layer from scratching.ZnO,TiN and GaN thin films were prepared on dg/PET by magnetron sputtering and vacuum evaporation,respectively.The optical and electrical properties of the hybrid films were measured by spectrophotometer and Hall Effect measurement.The morphology and bonds structures were checked by scanning electron microscopy?SEM?and X-ray photoelectron microscope?XPS?.The results showed that ZnO,TiN and GaN protective films on dg/PET substrates sputtered by RF magnetron sputtering were with square resistances of 2.3×10⁶?·sq^-1,1.4×10⁶?·sq^-1and 1.1×10⁶?·sq^-1,respectively;ZnO,TiN and GaN protective films on dg/PET substrates sputtered by pulsed magnetron sputtering were with square resistances of 3.7×10⁶?·sq^-1,1.3×10⁶?·sq^-1,and 1.4×10⁶?·sq^-11 respectively;ZnO,TiN and GaN protective films on dg/PET substrates by vacuum thermal evaporation were with square resistances of 5530?·sq^-1,835?·sq^-11 and 334?·sq^-1,respectively.The square resistances of zinc oxide?ZnO?,titanium nitride?TiN?and gallium nitride?GaN?prepared on graphene?dg?/PET substrates by pulsed and radio frequency magnetron sputtering were 10⁶?·sq^-1,which were much larger than that of graphene itself,157?·sq^-1.The square resistance of the prepared ZnO/dg/PET hybrid film prepared by vacuum thermal evaporation was much larger than that of graphene itself.It was observed that the cracks were existed on the surface of the TiN/dg/PET hybrid film by SEM morphological graphs,and the surface of graphene was not covered completely by TiN layer.The GaN layer prepared by vacuum thermal evaporation approach uniformly covered the surface of the double layer graphene without formation of the C-N bond.The structure of the GaN layer showed to be amorphous.When the thickness of the GaN layer was thinner than 35 nm,the transmittance of the GaN/dg/PET hybrid film reached 80%at the incident light of 600 nm,and the square resistance was 216?·sq^-1,which was comparable with that of the double layer graphene itself.The optical and electrical properties of the hybrid film meet the requirements of transparent conductive film in many applications.Therefore,GaN/dg/PET ultra-thin transparent conductive film prepared by vacuum evaporation has a promising application to replace the ITO films.