We report the dc and rf performance of graphene rf field-effect transistors,where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates.Compo...We report the dc and rf performance of graphene rf field-effect transistors,where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates.Composite materials,benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics.The observation of n- and p-type transitions verifies the ambipolar characteristics in the graphene layers.While the intrinsic carrier mobility of CVD graphene is extracted to be 1200cm2/V·s,the parasitic series resistances are demonstrated to have a serious impact on device performance.With a gate length of 1 μm and an extrinsic transconductance of 72 mS/mm,a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors,illustrating the potential of the CVD graphene for rf applications.展开更多
Blue photoluminescence is observed in aged porous silicon samples anodized under Ar^(+)488 nm laser illumination.No samples have been undergone any heating treatment process.Both nanosecond and microsecond decay of bl...Blue photoluminescence is observed in aged porous silicon samples anodized under Ar^(+)488 nm laser illumination.No samples have been undergone any heating treatment process.Both nanosecond and microsecond decay of blue photoluminescence have been measured.Samples show a good monoexponential microsecond decay with lifetimes of about 5.3μs.Photoluminescence excitation spectra of blue and red Photoluminescence indicate there is a large Stokes shift(about 800-900meV)in the excitation spectra of red photoluminescence while no this marked Stokes shift in that of blue photoluminescence.The possible origin of the photoluminescence is discussed based on the experimental results.展开更多
A novel characteristic of the junction current drift effect in the Cu/porous silicon(Cu/PS)device prepared by electrodeposition in which Cu ions were deposited on porous silicon is reported.The junction current increa...A novel characteristic of the junction current drift effect in the Cu/porous silicon(Cu/PS)device prepared by electrodeposition in which Cu ions were deposited on porous silicon is reported.The junction current increases with time and gradually approaches to a saturated value when a certain forward bias is applied on the Cu/PS device.Moreover,after the bias was withdrawn for a period,a different drift process was observed when the same bias was applied again.The drifttime constant and the initial current of latter drift process depend on cut-off time.Such an effect is explained in terms of the model that only part of electrons from porous silicon contributes to the junction current while other electrons are captured by the traps in the interface between Cu and porous silicon in the Cu/PS device.展开更多
基金Supported by the National Science and Technology Major Project(No 2011ZX02707.3)the National Basic Research Program of China(2011CB921400)the National Natural Science Foundation of China under Grount Nos 61136005(Key Program),61006063 and 50772110.
文摘We report the dc and rf performance of graphene rf field-effect transistors,where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates.Composite materials,benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics.The observation of n- and p-type transitions verifies the ambipolar characteristics in the graphene layers.While the intrinsic carrier mobility of CVD graphene is extracted to be 1200cm2/V·s,the parasitic series resistances are demonstrated to have a serious impact on device performance.With a gate length of 1 μm and an extrinsic transconductance of 72 mS/mm,a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors,illustrating the potential of the CVD graphene for rf applications.
基金Supported by the National Natural Science Foundation of China under Grant No.59372108the Laboratory of Excited State Processes,Changchun Institute of Physics,Chinese Academy of Sciences。
文摘Blue photoluminescence is observed in aged porous silicon samples anodized under Ar^(+)488 nm laser illumination.No samples have been undergone any heating treatment process.Both nanosecond and microsecond decay of blue photoluminescence have been measured.Samples show a good monoexponential microsecond decay with lifetimes of about 5.3μs.Photoluminescence excitation spectra of blue and red Photoluminescence indicate there is a large Stokes shift(about 800-900meV)in the excitation spectra of red photoluminescence while no this marked Stokes shift in that of blue photoluminescence.The possible origin of the photoluminescence is discussed based on the experimental results.
基金Supported by the National Natural Science Foundation of China under Grant No.59372108.
文摘A novel characteristic of the junction current drift effect in the Cu/porous silicon(Cu/PS)device prepared by electrodeposition in which Cu ions were deposited on porous silicon is reported.The junction current increases with time and gradually approaches to a saturated value when a certain forward bias is applied on the Cu/PS device.Moreover,after the bias was withdrawn for a period,a different drift process was observed when the same bias was applied again.The drifttime constant and the initial current of latter drift process depend on cut-off time.Such an effect is explained in terms of the model that only part of electrons from porous silicon contributes to the junction current while other electrons are captured by the traps in the interface between Cu and porous silicon in the Cu/PS device.
