Study On The Fabrication And Electron Transport Mechanism Of Nanogap Channel Devices

Vacuum electronic devices have been widely utilized in many fields due to the advantages of high frequency,high power and reliability.Limited by the machining complexity,however,the traditional vacuum electronics are difficult to achieve miniaturization and integration.With the maturity of solid-state electronic devices and integrated circuits,vacuum electronics have faded out of the public view gradually.Meanwhile,the development of the processing technology and novel nanomaterials provides the possibilities of breaking through the bottleneck of vacuum electronics.Recently,the nanogap structures have been injecting new vitality to this field.Nanogap,formed by vacuum or dielectric layer nano-channel,has been attracting attentions as the channel smaller than the mean free path of electron can behave as vacuum without scattering or collision.In this case,the nanogap channel devices could function regularly with less vacuum packaging.Here,we aim to explore the process route,mechanism and potential feasibility of nanogap.The principal research work is listed as follows:(1)Fabrication of planar vacuum nanogap arrays with electron beam lithography and focused ion beam etching.Modulation of the nanoscale channel from 10 to 30 nm with large-scale and high integration.With the in-situ probe testing system,we explore the field emission performance of nanogap with varying structure parameters and vacuum degrees,showing remarkable stability that widens the applied range of the nanogap devices.(2)Design and fabrication of planar side-gate nanogap transistor.It is observed that the optimization of side-gate structure and emitter/collector morphology could effectively enhance the emission properties of nanogap.Mean flight model was also demonstrated to study the frequency response characteristic with equivalent circuit model,making a theoretical foundation of vacuum nanogap transistor.(3)In situ characterization and measurement of graphene to verify and investigate the mechanism of electron transportation in vacuum condition.With the fabrication of suspended graphene on interdigital electrodes,we experimentally and theoretically discuss that the suspended structure could acquire a better enhancement than the conventional exfoliated graphene.With graphene directly transferred onto substrate,we demonstrate the possibility of improving the efficiency of graphene-based vacuum nano-devices with high-precision integration.(4)Combination of graphene and nanogap structure with traditional semiconductor technology.Graphene-based vertical dielectric layer nanogap and planar vacuum nanogap transistors were realized with ultraviolet/electron beam lithography,etching and deposition process.With large-scale graphene film(2×2 cm~2),nanoscale vacuum channel(<100 nm),low operating voltage(<20 V)and high switch ratio(146.4)compared to the conventional graphene transistor,the graphene-based nanogap transistor holds prospects for the future vacuum integrated circuits.