Study On The Graphene/Silicon Schottky Betavoltaic Nuclear Microbattery For High Volume Power Density

With the development of MEMS,the betavoltaic isotope battery has become an ideal micro energy source for MEMS because of its advantages such as long life,strong environmental adaptation,compact structure and non-maintenance.The new two-dimensional nanostructure materials of Graphene,with many excellent properties is expected as the new option into the development of betavoltaic isotope battery.In this paper,graphene with the excellent conductivity expected to replace the metal material layer of traditional Schottky junction betavoltaic isotope battery and solved the problem of the blocking action of radioactive decay particles from traditional metal material layer and its poor electrical conductivity.Also based on the thickness advantage of graphene,the graphene/silicon Schottky junction betavoltaic isotope battery with high volume power density was designed and developed.The main research works are as follows:Firstly,from the perspective of overall structure design,a graphene/silicon Schottky junction betavoltaic isotope battery based on double-sided 63Ni radioactive source was proposed.Then,the self-absorption effect of 63Ni radioactive source and the transport of ? particles in the Graphene and Silicon were investigated.The parameters of graphene/silicon Schottky junction betavoltaic isotope battery with high volume power density were optimized.The results show that,the graphene has almost no blocking effect on ?-particles and can effectively improve the energy deposition of ?-particles in semiconductor materials.When the source thickness was reduced from 3?m to 0.3 ?m,the theoretical output power density of the graphene/silicon Schottky junction betavoltaic isotope battery will increase by about 60%under the same total activity of the radioactive source.If the 15 ?m ultra-thin silicon was used,the volume power density of graphene/silicon Schottky junction betavoltaic isotope battery can be increased to 18.8 ?W/cm3,which is nearly two times higher than that of traditional devices.Secondly,from the point of radioactive source,the preparation method of 0.3 ?m(about 300 ?g/cm2)self-supporting 63Ni radioactive source film was studied.Electrochemical polishing and electroplating is an ideal method for preparing self-supporting nickel thin films.The effects of coppe substrate surface morphology and electroplating current density on the properties of self-supporting nickel thin films were investigated.The results show that,the surface roughness of copper substrate can be effectively reduced by appropriately increasing the electrochemical polishing voltage and prolonging the electrochemical polishing time,and the uniform and flat nickel film can be deposited on the surface of copper substrate under low current density.A self-supporting nickel thin film with a thickness of 280±10 ?g/cm2 was successfully prepared on a copper substrate under the current density of 12.5 mA/cm2 and the polishing condition of 7 V 20 s,which meet the design requirements.Then,the graphene/silicon Schottky junction betavoltaic isotope battery was designed and realized.And the effects of graphene energy band regulation(layer number control and nitric acid doping)on the device performance were revealed.The results show that compared with single-layer graphene,the ideal factor and barrier height of graphene/silicon Schottky junction devices with fewer layers graphene are improved.Furthermore,the multilayer graphene/silicon Schottky junction devices were fabricated by the method of lamination transfer of graphene.The characteristics of multilayer graphene/silicon Schottky junction devices are significantly improved with the increase of the graphene transfer times,which is close to the ideal Schottky junction.Under the irradiation of 63Ni radioactive source,the open-circuit voltage and short-circuit current density of the device both show an increasing trend.Compared with undoped graphene/silicon devices,the Schottky barrier height and reverse saturation current density of the devices are significantly optimized with the increase of nitric acid doping time.In particular,the output short-circuit current density of the device increases from 10.0 nA/cm2 to 16.8 nA/cm2 under the irradiation of the 63Ni radioactive source,which increases by about 60%.Finally,the reverse saturation current,the Schottky barrier height and the series-parallel resistance of four laminated transfer based on graphene and 2 min nitric acid preparation of multilayer graphene/silicon Schottky junction betavoltaic isotope battery were improved obviously.Under the irradiation of 63Ni radioactive source with an activity of 5 mCi/cm2,the device obtained the open circuit voltage of 48 mV and the short-circuit current density of 30.3 nA/cm2,which achieved the higher density of output short-circuit current and the performance is better than that of similar devices.By comparing the output performance of graphene/silicon devices with only nitric acid doped or only laminated transfer graphene,the synergistic mechanism of nitric acid doped and laminated transfer graphene on the performance improvement of graphene/silicon devices is revealed,and the application prospect of graphene materials in Schottky betavoltaic isotope batteries is also confirmed.To sum up,the high volume power density graphene/silicon Schottky junction betavoltaic isotope battery was design,also the preparation technology of the self-supporting thin film radioactive source and the factors affecting the output power density of graphene/silicon Schottky junction devices were explored,which will provide an important experimental reference for the development of Schottky betavoltaic isotope battery with high volume power density in the future.