A new analytical model of high voltage silicon on insulator (SOI) thin film devices is proposed, and a formula of silicon critical electric field is derived as a function of silicon film thickness by solving a 2D Po...A new analytical model of high voltage silicon on insulator (SOI) thin film devices is proposed, and a formula of silicon critical electric field is derived as a function of silicon film thickness by solving a 2D Poisson equation from an effective ionization rate, with a threshold energy taken into account for electron multiplying. Unlike a conventional silicon critical electric field that is constant and independent of silicon film thickness, the proposed silicon critical electric field increases sharply with silicon fihn thickness decreasing especially in the case of thin films, and can come to 141V/μm at a film thickness of 0.1 μm which is much larger than the normal value of about 30 V/μm. From the proposed formula of silicon critical electric field, the expressions of dielectric layer electric field and vertical breakdown voltage (VB,V) are obtained. Based on the model, an ultra thin film can be used to enhance dielectric layer electric field and so increase vertical breakdown voltage for SOI devices because of its high silicon critical electric field, and with a dielectric layer thickness of 2 μm the vertical breakdown voltages reach 852 and 300V for the silicon film thicknesses of 0.1 and 5μm, respectively. In addition, a relation between dielectric layer thickness and silicon film thickness is obtained, indicating a minimum vertical breakdown voltage that should be avoided when an SOI device is designed. 2D simulated results and some experimental results are in good agreement with analytical results.展开更多
Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully ...Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr~ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.展开更多
Nanocrystalline VO2 thin films were deposited onto glass slides by direct current magnetron sputtering and postoxidation. These films undergo semiconductor-metal transition at 70 ℃, accompanied by a resistance drop o...Nanocrystalline VO2 thin films were deposited onto glass slides by direct current magnetron sputtering and postoxidation. These films undergo semiconductor-metal transition at 70 ℃, accompanied by a resistance drop of two magnitude orders. The crystal structures and surface morphologies of the VO2 films were characterized by x-ray diffraction (XRD) and atomic force microscope (AFM), respectively. Results reveal that the average grain size of VO2 nanograins measured by XRD is smaller than those measured by AFM. In addition, Raman characterization indicates that stoichiometric VO2 and oxygen-rich VO2 phases coexist in the films, which is supported by x-ray photoelectron spectroscopy (XPS) results. Finally, the optical properties of the VO2 films in UV-visible range were also evaluated. The optical band gap corresponding to 2p-3d inter-band transition was deduced according to the transmission and reflection spectra. And the deduced value, Eopt2p-3d : 1.81 eV, is in good agreement with that previously obtained by theoretical calculation.展开更多
Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals ...Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.展开更多
Fluorescence/phosphorescence hybrid white organic light-emitting devices(WOLEDs) based on double emitting layers(EMLs) with high color stability are fabricated.The simplified EMLs consist of a non-doped blue therm...Fluorescence/phosphorescence hybrid white organic light-emitting devices(WOLEDs) based on double emitting layers(EMLs) with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence(TADF) layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone(DMAC-DPS) and an ultrathin non-doped yellow phosphorescence layer employing bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2']iridium(acetylacetonate)((tbt)_2Ir(acac)).Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline(Bphen) and 1,3,5-tris(2-Nphenylbenzimidazolyl) benzene(TPBi) are selected as the electron transporting layer(ETL),and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l'Eclairage(CIE) coordinates variation of(0.017,0.009) at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency(EQE),current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer(FRET)from DMAC-DPS to(tbt)_2Ir(acac) is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.展开更多
Organic optoelectronic integrated devices(OIDs) with ultraviolet(UV) photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence(TADF) material 4, 5-bis(ca...Organic optoelectronic integrated devices(OIDs) with ultraviolet(UV) photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence(TADF) material 4, 5-bis(carbazol-9-yl)-1, 2-dicyanobenzene(2 CzPN) as host. The OIDs doping with typical red phosphorescent dye [tris(1-phenylisoquinoline)iridium(Ⅲ), Ir(piq)3], orange phosphorescent dye {bis[2-(4-tertbutylphenyl)benzothiazolato-N,C-(2')]iridium(acetylacetonate),(tbt)2 Ir(acac)}, and blue phosphorescent dye [bis(2, 4-di-fluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(Ⅲ), FIr6] were investigated and compared. The(tbt)2 Ir(acac)-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the(tbt)2 Ir(acac)-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.展开更多
Organic electrochemical transistors(OECTs) exhibit significant potential for applications in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. ...Organic electrochemical transistors(OECTs) exhibit significant potential for applications in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. Expanding OECTs to the fexible devices will significantly facilitate stable contact with the skin and enable more possible bioelectronic applications. In this work,we summarize the device physics of fexible OECTs, aiming to offer a foundational understanding and guidelines for material selection and device architecture. Particular attention is paid to the advanced manufacturing approaches, including photolithography and printing techniques, which establish a robust foundation for the commercialization and large-scale fabrication. And abundantly demonstrated examples ranging from biosensors, artificial synapses/neurons, to bioinspired nervous systems are summarized to highlight the considerable prospects of smart healthcare. In the end, the challenges and opportunities are proposed for fexible OECTs. The purpose of this review is not only to elaborate on the basic design principles of fexible OECTs, but also to act as a roadmap for further exploration of wearable OECTs in advanced bio-applications.展开更多
We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn un...We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.展开更多
A series of FeCoHfO films were fabricated by dc magnetron reactive sputtering at varying partial pressure of oxygen (Po2) from 0 to 11.7%, and the electrical and magnetic properties of films have been studied. It is...A series of FeCoHfO films were fabricated by dc magnetron reactive sputtering at varying partial pressure of oxygen (Po2) from 0 to 11.7%, and the electrical and magnetic properties of films have been studied. It is shown that optimal Fe43.29 Co19.51Hf7.49 O29.71 films with desired properties can be obtained when the films were prepared under Po2= 5.1%. The films show superior properties of low coereivity, Hc ∽5.5 Oe, relatively high saturation magnetization, 47rMs · 18.3 kG, high anisotropy field Hk ∽ 65 Oe, and high electrical resistivity ρ∽ 2675 μΩ·cm. Permeability spectra shows that the natural ferromagnetic resonant frequency is as high as 3.1 GHz. The combined merits of the film make the films taken as an ideal candidate material for high-frequency applications such as noise suppressor. In addition, the effects of the film thickness and annealing treatment on the magnetic properties are also reported.展开更多
Cobalt ferrite thin films were deposited on TbFeCo(10 nm)/Si(100) and Si(100) substrates at a substrate temperature of 350 ℃ by RF magnetron sputtering. The heat treated films were analyzed by Vibrating Sample Magnet...Cobalt ferrite thin films were deposited on TbFeCo(10 nm)/Si(100) and Si(100) substrates at a substrate temperature of 350 ℃ by RF magnetron sputtering. The heat treated films were analyzed by Vibrating Sample Magnetometer (VSM) and X-Ray Photoelectron Spectroscopy (XPS). Results showed that all films had high coercivity and perpendicular anisotropy especially for the films deposited on TbFeCo underlayer. TbFeCo underlayers increase the coercivity, magnetization and remanence ratio of CoFe2O4 films, films on TbFeCo underlayer had coercivity and magnetization as high as 832×103 A·m-1 and 450×103 A·m-1, and its romance ratio reaches 0.9, which was related to the Tb3+ diffusion from the underlayer into the film.展开更多
Si p^+n junction diodes operating in the mode of avalanche breakdown are capable of emitting light in the visible range of 400-900 nm. In this study, to realize the switching speed in the GHz range, we present a trans...Si p^+n junction diodes operating in the mode of avalanche breakdown are capable of emitting light in the visible range of 400-900 nm. In this study, to realize the switching speed in the GHz range, we present a transient model to shorten the carrier lifetime in the high electric field region by accumulating carriers in both p and n type regions. We also verify the optoelectronic characteristics by disclosing the related physical mechanisms behind the light emission phenomena. The emission of visible light by a monolithically integrated Si diode under the reverse bias is also discussed. The light is emitted as spatial sources by the defects located at the p-n junction of the reverse-biased diode. The influence of the defects on the electrical behavior is manifested as a current-dependent electroluminescence.展开更多
Bismuth-based cubic pyrochlore materials have attractive dielectric properties,especially dielectric tunability.The Bi_(1.5)MgNb_(1.5)O_(7) ceramic samples were prepared by solid state reaction.The XRD results and SEM...Bismuth-based cubic pyrochlore materials have attractive dielectric properties,especially dielectric tunability.The Bi_(1.5)MgNb_(1.5)O_(7) ceramic samples were prepared by solid state reaction.The XRD results and SEM pictures prove the raw material are well mixed and co-fired and the BMN cubic pyrochlore is well crystallized,no second phase was found in the result.BMN thin film were fabricated by depositing BMN ceramic nanoparticles on the sapphire.The BMN thin film has a high dielectric tunability of 43%at a bias voltage of 1.5 MV/cm,with loss tangent lower than 0.009.A Raman study of BMN cubic pyrochlore reveals O′-A-O′and O-A-O bending modes contribute to 80%of dielectric permittivity,obstructing these modes such as applying external electric field can have apparent influence on dielectric constant.Berry Phase calculation results shows that A2O′tetrahedrons are more easy to distort under an external field.The A-site Mg have the highest displacement(0.765028 A),followed by A-site Bi cations(0.346317˚A).Compared to zero-bias thin film,˚the biased one with A-O and A-O′bonds being stretched and external coulomb force applied on cations and anions,the dielectric constant under bias field dramatically decreased.展开更多
Growth of cadmium sulfide (CdS) thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using Cd(S2CNEt2)2 as the single precursor. Changes in th...Growth of cadmium sulfide (CdS) thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using Cd(S2CNEt2)2 as the single precursor. Changes in the surface morphology of the deposited CdS thin films were investigated by atomic force microscope (AFM) as the function of substrate temperature (Ts), vaporizing temperature (Tv), and Ar flow rate. With the increase of Tv, CdS thin films evolved from pyramidal structure with fine grains to columnar structure with large grains. X-ray diffraction (XRD) patterns indicated that the CdS films had random orientation at the lower Tv and preferred orientation at the higher Tv. In addition, Ts had a great effect on the surface roughness of the CdS films, and a quantum dot-like structural CdS films were obtained in a narrow range of Ts with high Ar flow rate. Furthermore, the optical properties of the CdS films were measured using ultraviolet-visible (UV/VIS) spectrometer.展开更多
Unipolar resistive switching behaviors of the ZnO and ALO/ZnO films fabricated on flexible substrates by pulse laser deposition were studied in this paper. The films were deposited at room temperature without post-ann...Unipolar resistive switching behaviors of the ZnO and ALO/ZnO films fabricated on flexible substrates by pulse laser deposition were studied in this paper. The films were deposited at room temperature without post-annealing treatment during the process. Xray diffraction results indicated that ZnO film has a dominant peak at(002). Scanning electron microscopy observation showed a columnar grain structure of the ZnO film to the substrate. The bilayer device of ALO/ZnO films had stable resistive switching behaviors with a good endurance performance of more than 200 cycles, high resistive switching ratio of over 103 at a read voltage of 0.1V, which is better than that of the single oxide layer device of ZnO film. A possible resistive switching filamentary mode was demonstrated in this paper. The conduction mechanisms of high and low resistance states can be explained by space charge limited conduction and Ohmic’s behaviors. The endurance of the bilayer(BL) device was not degraded upon bending cycles, which indicates the potential of the flexible resistive switching random access memory applications.展开更多
Cd3As2, as a three-dimensional(3D) topological Dirac semimetal, has attracted wide attention due to its unique physical properties originating from the 3D massless Dirac fermions. While many efforts have been devoted ...Cd3As2, as a three-dimensional(3D) topological Dirac semimetal, has attracted wide attention due to its unique physical properties originating from the 3D massless Dirac fermions. While many efforts have been devoted to the exploration of novel physical phenomena such as chiral anomaly and phase transitions by using bulk crystals, the development of high-quality and large-scale thin films becomes necessary for practical electronic and optical applications. Here, we report our recent progress in developing single-crystalline thin films with improved quality and their optical devices including Cd3As2-based heterojunctions and ultrafast optical switches. We find that a post-annealing process can significantly enhance the crystallinity of Cd3As2 in both intrinsic and Zn-doped thin films. With excellent characteristics of high mobility and linear band dispersion, Cd3As2 exhibits a good optical response in the visible-to-mid-infrared range due to an advantageous optical absorption, which is reminiscent of 3D graphene. It also behaves as an excellent saturable absorber in the mid-infrared regime. Through the delicate doping process in this material system, it may further open up the long-sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources.展开更多
Ti4+ substitution for Fe3+ in Ni0.5Zn0.5Fe2O4(NZF) ferrite thin films were realized by sol-gel method and annealing at 600 ℃ for 30 min in the air. Crystal structure and lattice constant determination was performed b...Ti4+ substitution for Fe3+ in Ni0.5Zn0.5Fe2O4(NZF) ferrite thin films were realized by sol-gel method and annealing at 600 ℃ for 30 min in the air. Crystal structure and lattice constant determination was performed by X-ray diffractometer(XRD). Surface microstructure was observed by scanning electron microscope(SEM) and atomic force microscope(AFM),and the magnetic properties were measured by vibrating sample magnetometer(VSM). XRD analyses of the samples show that Ni0.5+xZn0.5TixFe2-2xO4(NZTF) films with x varying from 0 to 0.15 in steps of 0.05 are composed of single phase with spinel structure. And the lattice parameter,particle size and the diffraction intensity of the films increase with substitution of Ti as the result of the larger radius ions entering the lattice. SEM and AFM show homogeneous grain size of each sample,but there is a few differences in grain size with different Ti-substitution contents. As the nonmagnetic Ti4+ substitutes Fe3+,both the saturation magnetization and coercivity decrease.展开更多
The microwave permeability of laminated composites based on thin FeCoBSi films was under study.The level of permeability increased with increasing of the ferromagnetic inclusions in the laminates.The intrinsic permeab...The microwave permeability of laminated composites based on thin FeCoBSi films was under study.The level of permeability increased with increasing of the ferromagnetic inclusions in the laminates.The intrinsic permeability spectra of ferromagnetic inclusion are parametrically reconstructed.The obtained parameters of magnetic resonance were specially analyzed.To avoid the effect of eddy current and to obtain large-volume fractions of ferromagnetic constituent,laminates consisting of alternating FeCoBSi/SiO2 multi-layers and mylar substrates were also investigated.For the same volume fractions of ferromagnetic constituent (8.7%),laminates based on multi-layered films are found to possess higher values of permeability than those based on one-layered films.展开更多
Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-...Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP)/ 8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines- cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.展开更多
Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT ...Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT of VO_(2)thin film is important for the applications of this material in various devices.Here,the changes in thermal conductivity of epitaxial and polycrystalline VO_(2)thin film across MIT are probed by the time-domain thermoreflectance(TDTR)method.The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO_(2)film to attenuate the impact from extra thermal interfaces.It is demonstrated that the method is feasible for the VO_(2)films with thickness values larger than 100 nm and beyond the phase transition region.The observed reasonable thermal conductivity change rates across MIT of VO_(2)thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate,which is different from the reported behavior of single crystal VO_(2)nanowires.The recovery of the relationship between thermal conductivity and electrical conductivity in VO_(2)film may be attributed to the increasing elastic electron scattering weight,caused by the defects in the film.This work demonstrates the possibility and limitation of investigating the thermal properties of VO_(2)thin films by the TDTR method without depositing any metal thermoreflectance layer.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 60436030)National Laboratory of Analogue Integrated Circuits,China (Grant No 9140C090305060C09)
文摘A new analytical model of high voltage silicon on insulator (SOI) thin film devices is proposed, and a formula of silicon critical electric field is derived as a function of silicon film thickness by solving a 2D Poisson equation from an effective ionization rate, with a threshold energy taken into account for electron multiplying. Unlike a conventional silicon critical electric field that is constant and independent of silicon film thickness, the proposed silicon critical electric field increases sharply with silicon fihn thickness decreasing especially in the case of thin films, and can come to 141V/μm at a film thickness of 0.1 μm which is much larger than the normal value of about 30 V/μm. From the proposed formula of silicon critical electric field, the expressions of dielectric layer electric field and vertical breakdown voltage (VB,V) are obtained. Based on the model, an ultra thin film can be used to enhance dielectric layer electric field and so increase vertical breakdown voltage for SOI devices because of its high silicon critical electric field, and with a dielectric layer thickness of 2 μm the vertical breakdown voltages reach 852 and 300V for the silicon film thicknesses of 0.1 and 5μm, respectively. In addition, a relation between dielectric layer thickness and silicon film thickness is obtained, indicating a minimum vertical breakdown voltage that should be avoided when an SOI device is designed. 2D simulated results and some experimental results are in good agreement with analytical results.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11028409 and 60976061)the Fundamental Research Funds for the Central Universities of China (Grant No. ZYGX2009Z0001)
文摘Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr~ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.
基金Project partly supported by the National Natural Science Foundation of China (Grant No. 60736005)
文摘Nanocrystalline VO2 thin films were deposited onto glass slides by direct current magnetron sputtering and postoxidation. These films undergo semiconductor-metal transition at 70 ℃, accompanied by a resistance drop of two magnitude orders. The crystal structures and surface morphologies of the VO2 films were characterized by x-ray diffraction (XRD) and atomic force microscope (AFM), respectively. Results reveal that the average grain size of VO2 nanograins measured by XRD is smaller than those measured by AFM. In addition, Raman characterization indicates that stoichiometric VO2 and oxygen-rich VO2 phases coexist in the films, which is supported by x-ray photoelectron spectroscopy (XPS) results. Finally, the optical properties of the VO2 films in UV-visible range were also evaluated. The optical band gap corresponding to 2p-3d inter-band transition was deduced according to the transmission and reflection spectra. And the deduced value, Eopt2p-3d : 1.81 eV, is in good agreement with that previously obtained by theoretical calculation.
基金Project(20123227120021)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(BK2012156)supported by the Natural Science Foundation of Jiangsu Province,China+3 种基金Project(KFJJ201105)supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(CJ20125001)supported by the Application Program for Basic Research of Changzhou,ChinaProject(13KJB430006)supported by the Universities Natural Science Research project of Jiangsu Province,ChinaProject supported by the Industrial Center of Jiangsu University Undergraduate Practice-Innovation Training Program,China
文摘Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675041 and 61605253)the Foundation for Innovation Research Groups of the National Natural Science Foundation of China(Grant No.61421002)the Science&Technology Department Program of Sichuan Province,China(Grant No.2016HH0027)
文摘Fluorescence/phosphorescence hybrid white organic light-emitting devices(WOLEDs) based on double emitting layers(EMLs) with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence(TADF) layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone(DMAC-DPS) and an ultrathin non-doped yellow phosphorescence layer employing bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2']iridium(acetylacetonate)((tbt)_2Ir(acac)).Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline(Bphen) and 1,3,5-tris(2-Nphenylbenzimidazolyl) benzene(TPBi) are selected as the electron transporting layer(ETL),and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l'Eclairage(CIE) coordinates variation of(0.017,0.009) at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency(EQE),current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer(FRET)from DMAC-DPS to(tbt)_2Ir(acac) is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant No.61675041)the National Science Funds for Creative Research Groups of China(Grant No.61421002)
文摘Organic optoelectronic integrated devices(OIDs) with ultraviolet(UV) photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence(TADF) material 4, 5-bis(carbazol-9-yl)-1, 2-dicyanobenzene(2 CzPN) as host. The OIDs doping with typical red phosphorescent dye [tris(1-phenylisoquinoline)iridium(Ⅲ), Ir(piq)3], orange phosphorescent dye {bis[2-(4-tertbutylphenyl)benzothiazolato-N,C-(2')]iridium(acetylacetonate),(tbt)2 Ir(acac)}, and blue phosphorescent dye [bis(2, 4-di-fluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(Ⅲ), FIr6] were investigated and compared. The(tbt)2 Ir(acac)-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the(tbt)2 Ir(acac)-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.
基金sponsored by the Regional Joint Fund of the National Science Foundation of China via Grant No. U21A20492the National Natural Science Foundation of China (NSFC) via Grant No. 62275041+2 种基金the Sichuan Science and Technology Program via Grant Nos. 2022YFH0081, 2022YFG0012 and 2022YFG0013the Sichuan Youth Software Innovation Project Funding via Grant No. MZGC20230068the Sichuan Province Key Laboratory of Display Science and Technology。
文摘Organic electrochemical transistors(OECTs) exhibit significant potential for applications in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. Expanding OECTs to the fexible devices will significantly facilitate stable contact with the skin and enable more possible bioelectronic applications. In this work,we summarize the device physics of fexible OECTs, aiming to offer a foundational understanding and guidelines for material selection and device architecture. Particular attention is paid to the advanced manufacturing approaches, including photolithography and printing techniques, which establish a robust foundation for the commercialization and large-scale fabrication. And abundantly demonstrated examples ranging from biosensors, artificial synapses/neurons, to bioinspired nervous systems are summarized to highlight the considerable prospects of smart healthcare. In the end, the challenges and opportunities are proposed for fexible OECTs. The purpose of this review is not only to elaborate on the basic design principles of fexible OECTs, but also to act as a roadmap for further exploration of wearable OECTs in advanced bio-applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004067,11974070,62027807,and 52272137)the National Key R&D Program of China(Grant No.2022YFA1403000)。
文摘We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.
基金Supported by the National Basic Research Program of China under Grant No 2007CB310407, the National Natural Science Foundation of China under Grant Nos 60721001 and 60771047, and the International S&T Cooperation Program of China under Grant No 2007DFR10250.
文摘A series of FeCoHfO films were fabricated by dc magnetron reactive sputtering at varying partial pressure of oxygen (Po2) from 0 to 11.7%, and the electrical and magnetic properties of films have been studied. It is shown that optimal Fe43.29 Co19.51Hf7.49 O29.71 films with desired properties can be obtained when the films were prepared under Po2= 5.1%. The films show superior properties of low coereivity, Hc ∽5.5 Oe, relatively high saturation magnetization, 47rMs · 18.3 kG, high anisotropy field Hk ∽ 65 Oe, and high electrical resistivity ρ∽ 2675 μΩ·cm. Permeability spectra shows that the natural ferromagnetic resonant frequency is as high as 3.1 GHz. The combined merits of the film make the films taken as an ideal candidate material for high-frequency applications such as noise suppressor. In addition, the effects of the film thickness and annealing treatment on the magnetic properties are also reported.
基金Supported by Program for New Century Excellent Talents in University (NCET-09-0265), Sichuan Provincial Science Foundation for Youths (No 2010JQ0002), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University (No 201011005), and Foundation Franco Chinoise pour la Science et ses Applications (FFCSA), respectively.
文摘铟听氧化物(ITO ) 层被在房间温度劈啪作响的 rf 磁控管在 polymethylmethacrylate 和聚乙烯 terephthalate 上准备。他们的 3D-AFM 图象和可见发射度系列对比地被描绘并且学习。他们的最高的 ITO 层上的聚合物底层的有趣的词法效果被观察。从光系列推出的主导的直接、间接的转变类型令人惊讶地在不同聚合物上在 ITO 电影被发现。而且,质的乐队结构被考虑,并且关于光乐队的关联的一些理论讨论组织接口 / 表面形态学和搬运人密度也被介绍。[从作者抽象]
基金the National Natural Science Foundation of China (60490296 ,60671029 ,90306015)
文摘Cobalt ferrite thin films were deposited on TbFeCo(10 nm)/Si(100) and Si(100) substrates at a substrate temperature of 350 ℃ by RF magnetron sputtering. The heat treated films were analyzed by Vibrating Sample Magnetometer (VSM) and X-Ray Photoelectron Spectroscopy (XPS). Results showed that all films had high coercivity and perpendicular anisotropy especially for the films deposited on TbFeCo underlayer. TbFeCo underlayers increase the coercivity, magnetization and remanence ratio of CoFe2O4 films, films on TbFeCo underlayer had coercivity and magnetization as high as 832×103 A·m-1 and 450×103 A·m-1, and its romance ratio reaches 0.9, which was related to the Tb3+ diffusion from the underlayer into the film.
基金Project supported by the National Natural Science Foundation of China(Grant No.61704019)
文摘Si p^+n junction diodes operating in the mode of avalanche breakdown are capable of emitting light in the visible range of 400-900 nm. In this study, to realize the switching speed in the GHz range, we present a transient model to shorten the carrier lifetime in the high electric field region by accumulating carriers in both p and n type regions. We also verify the optoelectronic characteristics by disclosing the related physical mechanisms behind the light emission phenomena. The emission of visible light by a monolithically integrated Si diode under the reverse bias is also discussed. The light is emitted as spatial sources by the defects located at the p-n junction of the reverse-biased diode. The influence of the defects on the electrical behavior is manifested as a current-dependent electroluminescence.
基金supported by the National Natural Science Foundation of China(Grant No.51602037)the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices(Grant No.KFJJ201510).
文摘Bismuth-based cubic pyrochlore materials have attractive dielectric properties,especially dielectric tunability.The Bi_(1.5)MgNb_(1.5)O_(7) ceramic samples were prepared by solid state reaction.The XRD results and SEM pictures prove the raw material are well mixed and co-fired and the BMN cubic pyrochlore is well crystallized,no second phase was found in the result.BMN thin film were fabricated by depositing BMN ceramic nanoparticles on the sapphire.The BMN thin film has a high dielectric tunability of 43%at a bias voltage of 1.5 MV/cm,with loss tangent lower than 0.009.A Raman study of BMN cubic pyrochlore reveals O′-A-O′and O-A-O bending modes contribute to 80%of dielectric permittivity,obstructing these modes such as applying external electric field can have apparent influence on dielectric constant.Berry Phase calculation results shows that A2O′tetrahedrons are more easy to distort under an external field.The A-site Mg have the highest displacement(0.765028 A),followed by A-site Bi cations(0.346317˚A).Compared to zero-bias thin film,˚the biased one with A-O and A-O′bonds being stretched and external coulomb force applied on cations and anions,the dielectric constant under bias field dramatically decreased.
基金supported by the Project of Key Technologies Research & Development Programme of Chengdu under Grant No.06GGYB512GX-030
文摘Growth of cadmium sulfide (CdS) thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using Cd(S2CNEt2)2 as the single precursor. Changes in the surface morphology of the deposited CdS thin films were investigated by atomic force microscope (AFM) as the function of substrate temperature (Ts), vaporizing temperature (Tv), and Ar flow rate. With the increase of Tv, CdS thin films evolved from pyramidal structure with fine grains to columnar structure with large grains. X-ray diffraction (XRD) patterns indicated that the CdS films had random orientation at the lower Tv and preferred orientation at the higher Tv. In addition, Ts had a great effect on the surface roughness of the CdS films, and a quantum dot-like structural CdS films were obtained in a narrow range of Ts with high Ar flow rate. Furthermore, the optical properties of the CdS films were measured using ultraviolet-visible (UV/VIS) spectrometer.
基金supported by the National Key Research and Development Program of China under Grant No.2016YFB0700201the National Natural Science Foundation of China under Grant No.51372030
文摘Unipolar resistive switching behaviors of the ZnO and ALO/ZnO films fabricated on flexible substrates by pulse laser deposition were studied in this paper. The films were deposited at room temperature without post-annealing treatment during the process. Xray diffraction results indicated that ZnO film has a dominant peak at(002). Scanning electron microscopy observation showed a columnar grain structure of the ZnO film to the substrate. The bilayer device of ALO/ZnO films had stable resistive switching behaviors with a good endurance performance of more than 200 cycles, high resistive switching ratio of over 103 at a read voltage of 0.1V, which is better than that of the single oxide layer device of ZnO film. A possible resistive switching filamentary mode was demonstrated in this paper. The conduction mechanisms of high and low resistance states can be explained by space charge limited conduction and Ohmic’s behaviors. The endurance of the bilayer(BL) device was not degraded upon bending cycles, which indicates the potential of the flexible resistive switching random access memory applications.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303302 and 2018YFA0305601)the National Natural Science Foundation of China(Grant Nos.61322407,11474058,61674040,and 11874116)
文摘Cd3As2, as a three-dimensional(3D) topological Dirac semimetal, has attracted wide attention due to its unique physical properties originating from the 3D massless Dirac fermions. While many efforts have been devoted to the exploration of novel physical phenomena such as chiral anomaly and phase transitions by using bulk crystals, the development of high-quality and large-scale thin films becomes necessary for practical electronic and optical applications. Here, we report our recent progress in developing single-crystalline thin films with improved quality and their optical devices including Cd3As2-based heterojunctions and ultrafast optical switches. We find that a post-annealing process can significantly enhance the crystallinity of Cd3As2 in both intrinsic and Zn-doped thin films. With excellent characteristics of high mobility and linear band dispersion, Cd3As2 exhibits a good optical response in the visible-to-mid-infrared range due to an advantageous optical absorption, which is reminiscent of 3D graphene. It also behaves as an excellent saturable absorber in the mid-infrared regime. Through the delicate doping process in this material system, it may further open up the long-sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources.
文摘Ti4+ substitution for Fe3+ in Ni0.5Zn0.5Fe2O4(NZF) ferrite thin films were realized by sol-gel method and annealing at 600 ℃ for 30 min in the air. Crystal structure and lattice constant determination was performed by X-ray diffractometer(XRD). Surface microstructure was observed by scanning electron microscope(SEM) and atomic force microscope(AFM),and the magnetic properties were measured by vibrating sample magnetometer(VSM). XRD analyses of the samples show that Ni0.5+xZn0.5TixFe2-2xO4(NZTF) films with x varying from 0 to 0.15 in steps of 0.05 are composed of single phase with spinel structure. And the lattice parameter,particle size and the diffraction intensity of the films increase with substitution of Ti as the result of the larger radius ions entering the lattice. SEM and AFM show homogeneous grain size of each sample,but there is a few differences in grain size with different Ti-substitution contents. As the nonmagnetic Ti4+ substitutes Fe3+,both the saturation magnetization and coercivity decrease.
基金Funded by the National Natural Science Foundation of China(Nos.60701016,60911130130)the Fundamental Research Funds for the Central Universities (No.ZYGX2009J032)
文摘The microwave permeability of laminated composites based on thin FeCoBSi films was under study.The level of permeability increased with increasing of the ferromagnetic inclusions in the laminates.The intrinsic permeability spectra of ferromagnetic inclusion are parametrically reconstructed.The obtained parameters of magnetic resonance were specially analyzed.To avoid the effect of eddy current and to obtain large-volume fractions of ferromagnetic constituent,laminates consisting of alternating FeCoBSi/SiO2 multi-layers and mylar substrates were also investigated.For the same volume fractions of ferromagnetic constituent (8.7%),laminates based on multi-layered films are found to possess higher values of permeability than those based on one-layered films.
基金National Natural Science Foundation of China (Grant No.60425101)Program for New Cen-tury Excellent Talents in University (Grant No.NCET-06-0812)the Young Excellence Project of UESTC (Grant No.060206.)
文摘Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP)/ 8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines- cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61825102,51872038,and 52021001)the“111”Project,China(Grant No.B18011).
文摘Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT of VO_(2)thin film is important for the applications of this material in various devices.Here,the changes in thermal conductivity of epitaxial and polycrystalline VO_(2)thin film across MIT are probed by the time-domain thermoreflectance(TDTR)method.The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO_(2)film to attenuate the impact from extra thermal interfaces.It is demonstrated that the method is feasible for the VO_(2)films with thickness values larger than 100 nm and beyond the phase transition region.The observed reasonable thermal conductivity change rates across MIT of VO_(2)thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate,which is different from the reported behavior of single crystal VO_(2)nanowires.The recovery of the relationship between thermal conductivity and electrical conductivity in VO_(2)film may be attributed to the increasing elastic electron scattering weight,caused by the defects in the film.This work demonstrates the possibility and limitation of investigating the thermal properties of VO_(2)thin films by the TDTR method without depositing any metal thermoreflectance layer.