Electrical and structural properties of nanocrystalline solids of C80 fullerene encapsulated with a Lu3N cluster, Lu3N@C80, have been studied by measuring x-ray photoemission spectra, x-ray diffraction, and current-vo...Electrical and structural properties of nanocrystalline solids of C80 fullerene encapsulated with a Lu3N cluster, Lu3N@C80, have been studied by measuring x-ray photoemission spectra, x-ray diffraction, and current-voltage characteristics of the Lu3N@C80/Au Schottky contact in the temperature range of 300 - 500 K. The nanocrystalline solid sample of Lu3N@C80 fullerene consists of grains characterized with an fcc structure and those grains become larger in size after pressing the powder sample at 1.25 GPa. The current-voltage characteristics measured at various temperatures showed that there are no significant dependences on both the Schottky barrier and the carrier mobility on electric field. The Schottky barrier of the Lu3N@C80/Au contact is determined to be 0.71 ± 0.04 eV.展开更多
Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promis...Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promise for next-generation information circuits,still suffer from poor contact quality at the metal–semiconductor junction interface,which severely hinders their further applications.Here,a novel contact strategy is proposed,where Bi_(2)Te_(3)nanosheets with high conductivity were in-situ epitaxially grown on MoS_(2)as van der Waals contacts,which can effectively avoid the damage to MoS_(2)caused during the device manufacturing process,leading to a high-performance MoS_(2)FET.Moreover,the small work function difference between Bi_(2)Te_(3)and MoS_(2)(Bi_(2)Te_(3):4.31 eV,MoS_(2):4.37 eV,measured by Kelvin probe force microscopy(KPFM)),enables small band bending and Ohmic contact at the junction interface.Electrical characterizations indicate that the MoS_(2)FET device with Bi_(2)Te_(3)contacts possesses a high current on/off ratio(5×107),large effective carrier mobility(90 cm^(2)/(V·s)),and low flat-band SBH(60 meV),which is favorable as compared with MoS_(2)FET with traditional Cr/Au electrodes contacts,and superior to the vast majority of the reported chemical vapor deposition(CVD)MoS_(2)-based FET device.The demonstration of epitaxial van der Waals Bi_(2)Te_(3)contacts will facilitate the application of 2D MoS_(2)nanosheet in next-generation low-power consumption electronics and optoelectronics.展开更多
The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of curr...The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.展开更多
The effects of various notch structures on direct current(DC) and radio frequency(RF) performances of AlGaN/GaN high electron mobility transistors(HEMTs) are analyzed.The AlGaN/GaN HEMTs,each with a 0.8-μm gate lengt...The effects of various notch structures on direct current(DC) and radio frequency(RF) performances of AlGaN/GaN high electron mobility transistors(HEMTs) are analyzed.The AlGaN/GaN HEMTs,each with a 0.8-μm gate length,50-μm gate width,and 3-μm source-drain distance in various notch structures at the AlGaN/GaN barrier layer,are manufactured to achieve the desired DC and RF characteristics.The maximum drain current(I_(ds,max)),pinch-off voltage(V_(th)),maximum transconductance(gm),gate voltage swing(GVS),subthreshold current,gate leakage current,pulsed I-V characteristics,breakdown voltage,cut-off frequency(f_(T)),and maximum oscillation frequency(f_(max)) are investigated.The results show that the double-notch structure HEMT has a 30% improvement of gate voltage swing,a 42.2% improvement of breakdown voltage,and a 9% improvement of cut-off frequency compared with the conventional HEMT.The notch structure also has a good suppression of the current collapse.展开更多
AIM： To examine the expression of high mobility group box-1（HMGB-1） and intercellular adhesion molecule-1（ICAM-1） in the retina and the hippocampal tissues; and further to evaluate the association of these two mo...AIM： To examine the expression of high mobility group box-1（HMGB-1） and intercellular adhesion molecule-1（ICAM-1） in the retina and the hippocampal tissues; and further to evaluate the association of these two molecules with the alterations of blood-retinal barrier（BRB） and blood-brain barrier（BBB） in a rat model of type 2 diabetes.METHODS： The type-2 diabetes mellitus（DM） model was established with a high-fat and high-glucose diet combined with streptozotocin（STZ）. Sixteen weeks after DM induction, morphological changes of retina and hippocampus were observed with hematoxylin-eosin staining, and alternations of BRB and BBB permeability were measured using Evans blue method. Levels of HMGB-1 and ICAM-1 in retina and hippocampus were detected by Western blot. Serum HMGB-1 levels were determined by enzyme-linked immunosorbent assay（ELISA）.RESULTS： A significantly higher serum fasting blood glucose level in DM rats was observed 2wk after STZ injection（P 〈0.01）. The serum levels of fasting insulin,Insulin resistance homeostatic model assessment（IRHOMA）,total cholesterol（TC）, total triglycerides（TG） and low density lipoprotein cholesterol（LDL-C） in the DM rats significantly higher than those in the controls（all P 〈0.01）.HMGB-1（0.96±0.03, P 〈0.01） and ICAM-1（0.76±0.12, P 〈0.05） levels in the retina in the DM rats were significantly higher than those in the controls. HMGB-1（0.83±0.13, P 〈0.01） and ICAM-1（1.15 ±0.08, P 〈0.01） levels in the hippocampal tissues in the DM rats were alsosignificantly higher than those in the controls. Sixteen weeks after induction of DM, the BRB permeability to albumin-bound Evans blue dye in the DM rats was significantly higher than that in the controls（P 〈0.01）.However, there was no difference of BBB permeability between the DM rats and controls. When compared to the controls, hematoxylin and eosin staining showed obvious irregularities in the DM rats.CONCLUSION： BRB permeability increases sig展开更多
文摘Electrical and structural properties of nanocrystalline solids of C80 fullerene encapsulated with a Lu3N cluster, Lu3N@C80, have been studied by measuring x-ray photoemission spectra, x-ray diffraction, and current-voltage characteristics of the Lu3N@C80/Au Schottky contact in the temperature range of 300 - 500 K. The nanocrystalline solid sample of Lu3N@C80 fullerene consists of grains characterized with an fcc structure and those grains become larger in size after pressing the powder sample at 1.25 GPa. The current-voltage characteristics measured at various temperatures showed that there are no significant dependences on both the Schottky barrier and the carrier mobility on electric field. The Schottky barrier of the Lu3N@C80/Au contact is determined to be 0.71 ± 0.04 eV.
基金The authors are grateful to the National Key R&D Program of China(No.2022YFA1402501)the National Natural Science Foundation of China(Nos.51902098,62090035,U22A2013,and U19A2090)+3 种基金the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Program of Hunan Province(Nos.2021RC3061,2020RC2028,and 2021RC2042)the Natural Science Foundation of Hunan Province(No.2021JJ20016)the Project funded by China Postdoctoral Science Foundation(Nos.2020M680112 and 2021M690953).
文摘Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promise for next-generation information circuits,still suffer from poor contact quality at the metal–semiconductor junction interface,which severely hinders their further applications.Here,a novel contact strategy is proposed,where Bi_(2)Te_(3)nanosheets with high conductivity were in-situ epitaxially grown on MoS_(2)as van der Waals contacts,which can effectively avoid the damage to MoS_(2)caused during the device manufacturing process,leading to a high-performance MoS_(2)FET.Moreover,the small work function difference between Bi_(2)Te_(3)and MoS_(2)(Bi_(2)Te_(3):4.31 eV,MoS_(2):4.37 eV,measured by Kelvin probe force microscopy(KPFM)),enables small band bending and Ohmic contact at the junction interface.Electrical characterizations indicate that the MoS_(2)FET device with Bi_(2)Te_(3)contacts possesses a high current on/off ratio(5×107),large effective carrier mobility(90 cm^(2)/(V·s)),and low flat-band SBH(60 meV),which is favorable as compared with MoS_(2)FET with traditional Cr/Au electrodes contacts,and superior to the vast majority of the reported chemical vapor deposition(CVD)MoS_(2)-based FET device.The demonstration of epitaxial van der Waals Bi_(2)Te_(3)contacts will facilitate the application of 2D MoS_(2)nanosheet in next-generation low-power consumption electronics and optoelectronics.
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083) Science Foundation of Central South University( 0601059)
文摘The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61674117 and 61974108)the State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology of Xidian University,China。
文摘The effects of various notch structures on direct current(DC) and radio frequency(RF) performances of AlGaN/GaN high electron mobility transistors(HEMTs) are analyzed.The AlGaN/GaN HEMTs,each with a 0.8-μm gate length,50-μm gate width,and 3-μm source-drain distance in various notch structures at the AlGaN/GaN barrier layer,are manufactured to achieve the desired DC and RF characteristics.The maximum drain current(I_(ds,max)),pinch-off voltage(V_(th)),maximum transconductance(gm),gate voltage swing(GVS),subthreshold current,gate leakage current,pulsed I-V characteristics,breakdown voltage,cut-off frequency(f_(T)),and maximum oscillation frequency(f_(max)) are investigated.The results show that the double-notch structure HEMT has a 30% improvement of gate voltage swing,a 42.2% improvement of breakdown voltage,and a 9% improvement of cut-off frequency compared with the conventional HEMT.The notch structure also has a good suppression of the current collapse.
基金Supported by the Project of Education Bureau Foundation of Hubei Province(No.Q20151901)
文摘AIM： To examine the expression of high mobility group box-1（HMGB-1） and intercellular adhesion molecule-1（ICAM-1） in the retina and the hippocampal tissues; and further to evaluate the association of these two molecules with the alterations of blood-retinal barrier（BRB） and blood-brain barrier（BBB） in a rat model of type 2 diabetes.METHODS： The type-2 diabetes mellitus（DM） model was established with a high-fat and high-glucose diet combined with streptozotocin（STZ）. Sixteen weeks after DM induction, morphological changes of retina and hippocampus were observed with hematoxylin-eosin staining, and alternations of BRB and BBB permeability were measured using Evans blue method. Levels of HMGB-1 and ICAM-1 in retina and hippocampus were detected by Western blot. Serum HMGB-1 levels were determined by enzyme-linked immunosorbent assay（ELISA）.RESULTS： A significantly higher serum fasting blood glucose level in DM rats was observed 2wk after STZ injection（P 〈0.01）. The serum levels of fasting insulin,Insulin resistance homeostatic model assessment（IRHOMA）,total cholesterol（TC）, total triglycerides（TG） and low density lipoprotein cholesterol（LDL-C） in the DM rats significantly higher than those in the controls（all P 〈0.01）.HMGB-1（0.96±0.03, P 〈0.01） and ICAM-1（0.76±0.12, P 〈0.05） levels in the retina in the DM rats were significantly higher than those in the controls. HMGB-1（0.83±0.13, P 〈0.01） and ICAM-1（1.15 ±0.08, P 〈0.01） levels in the hippocampal tissues in the DM rats were alsosignificantly higher than those in the controls. Sixteen weeks after induction of DM, the BRB permeability to albumin-bound Evans blue dye in the DM rats was significantly higher than that in the controls（P 〈0.01）.However, there was no difference of BBB permeability between the DM rats and controls. When compared to the controls, hematoxylin and eosin staining showed obvious irregularities in the DM rats.CONCLUSION： BRB permeability increases sig
