| New carbon based materials are playing increasingly important roles in the fields of science,technology,economy and military with their excellent physical and chemical properties,abundant natural reserves and pollution-free.Graphene and diamond like carbon(DLC)are new types of carbon-based functional film materials with broad application prospects in the fields of machinery,automotive,electronics,biology and medical.For modern sensing technology,the new sensor based on carbon-based functional films has the advantages of small size,fast response,high detection sensitivity,low processing cost and good biocompatibility.Therefore,it is one of the most important development directions of sensors in the future.But at present,the sensor based on graphene is still in its infancy and some factors make the research results of it remain in the laboratory.For example,graphene can not be manufactured in large quantities and at low cost,graphene transfer technology is only suitable for small-area films,and the structure of the sensor still has room for optimization.For the DLC film,although some related results have been put into use,the application conditions and application scope of DLC films are greatly limited due to the shortcomings of the film,such as large internal stress and poor conductivity.Thus,in-depth study of micro-nanofabrication and processing technology of graphene and DLC functional films for advanced sensing applications will help break through the bottleneck of current key technologies,which is of positive significance for the practical application of new sensors.The main research and results of this paper are as follows:Graphene films were prepared by cold wall chemical vapor deposition(CVD)based on copper foil,and two novel graphene sensors were designed and fabricated.Firstly,a gold film with a thickness of 70 nm and an area of 100 ?m×100 ?m was fabricated as an electrode on a silica substrate by photolithography,magnetron sputtering and lift-off.A layer of titanium with a thickness of 10 nm was sputtered between the substrate and the gold electrode as the adhesion layer.Each pair of electrodes is connected by four equalwidth graphene channels and the length of the channels is designed to 30 ?m and 80 ?m,respectively.The single layer graphene deposited on the copper foil was successfully transferred to the target substrate by improved wet transfer technology of graphene.Then the graphene film is patterned by photolithography and plasma etching to form the channels.Characterized by optical microscopy and electron microscopy,the two graphene sensors show complete structures.Especially,the graphene film is very flat and almost has no holes.Finally,the graphene sensors are used for chemical detection of three different concentrations of Rhodamine B solution.The results show that the prepared graphene sensors have meet the requirements and has great potential in biochemical detection and sensing.In order to improve the conductivity and adhesion of the DLC films,nitrogen doping at different concentrations was carried out.Four kinds of hydrogen-free DLC films with different nitrogen doping concentrations were prepared on the silica substrate by closed field unbalanced magnetron sputtering.The sputtering duration of each film was 20 minutes.The elemental content and chemical structure of the films were characterized by X-ray photoelectron spectroscopy and Raman spectroscopy.The minimum nitrogen content of the films was 0,i.e.pure DLC film,the highest nitrogen content reached 23.37%.As the nitrogen-doped concentration increases,the sp3 hybrid bond content of the DLC films decreases,and the graphite phase of the film increases.The thickness and growth rate of the film were investigated by surface profiler.The thickness of the film was between 180 nm and 350 nm.The higher the nitrogen flow rate during sputtering,the faster the growth rate of the films.The nano-mechanical properties of the films were tested by in-situ nanomechanical test system.The friction coefficients of all films were less than 0.11.With the increase of nitrogen doping content,the nano-hardness of the films gradually decreased from 15.45655 GPa to 10.1798 GPa.The surface roughness of the film was studied by atomic force microscope.It was found that the surface of all films was very smooth and all of the root mean square roughness were less than 1 nm.Finally,the DLC films were fabricated into electrodes,and the resistivity of the films was measured by four-probe tester.The results show that the nitrogen doping greatly reduces the resistivity of the DLC film.Electrochemical workstations were used to study the potential windows of film electrodes in dilute sulfuric acid solutions.Compared with traditional glassy carbon electrodes,the potential window,mechanical properties and biocompatibility of nitrogen doped DLC film electrodes are better.This indicates that nitrogen doped DLC film electrodes have great potential for application in high voltage oxidation-reduction reaction and bio electrode sensing. |
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