Donor−acceptor(D−A)conjugated polymers are promising materials for organic transistors including organic field-effect transistors(OFETs)and organic electrochemical transistors(OECTs).The aggregated structure of D−A co...Donor−acceptor(D−A)conjugated polymers are promising materials for organic transistors including organic field-effect transistors(OFETs)and organic electrochemical transistors(OECTs).The aggregated structure of D−A conjugated polymer films,which strongly depends on the crystallization process,is crucial for the device performance.However,the crystallization of D−A conjugated polymers is complicated during solution processing,and the optimal film structure is various in different applications.Therefore,it is significantly important to reveal the relationship between the processing conditions and the resulting aggregated structures.This review provides a systematic understanding of how to control the aggregated structure of D−A conjugated polymer films from the fundamental mechanisms of polymer crystallization.We first discuss the possible nucleation and growth mechanisms of D−A conjugated polymers based on traditional theories or models and current findings.Then,recent progress in controlling the structure of D−A conjugated polymer films for OFETs and OECTs is reviewed.D−A conjugated polymers generally adopt chain-extended crystallization due to their strongly rigid backbone,which makes homogeneous nucleation difficult.A common strategy to control the aggregated structure of D−A conjugated polymer films is to manipulate the heterogeneous nucleation process by tuning the preaggregation.Besides,the effect of the crystallization rate and complicated conditions on the aggregated structure of D−A conjugated polymer films is also discussed.Finally,a concise summary is provided,followed by some current challenges in controlling the aggregated structure of D−A conjugated polymer films.展开更多
Optical multilayer thin film structures have been widely used in numerous photonic applications.However,existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design...Optical multilayer thin film structures have been widely used in numerous photonic applications.However,existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design targets,or are difficult to suit for different types of structures,e.g.,designing for different materials at each layer.These methods also cannot accommodate versatile design situations under different angles and polarizations.In addition,how to benefit practical fabrications and manufacturing has not been extensively considered yet.In this work,we introduce OptoGPT(Opto Generative Pretrained Transformer),a decoder-only transformer,to solve all these drawbacks and issues simultaneously.展开更多
The microstructure of CdI2 thin film grown during vapor-phase deposition was investigated by scanning electron microscopy (SEM). The thin film deposited on Si crystal consists of numerous sunflower-like aggregates. Th...The microstructure of CdI2 thin film grown during vapor-phase deposition was investigated by scanning electron microscopy (SEM). The thin film deposited on Si crystal consists of numerous sunflower-like aggregates. These aggregates display well self-assembly characteristics. The size of Sunflower-like aggregates is between 12 and 44 μm. Each sunflower-like aggregate is surrounded with many adjacent wings-'petals'. The structure of central region of the 'sunflower' is obviously difFerent from that of the 'petal'. Electron spectroscopy for chemical analysis (ESCA) was employed in determining the chemical valence of the thin film. Self-organization efFect is used to explain the coring growth process of CdI2 thin film展开更多
The dependence of the Recombination- Generation( R- G) current on the bulk trap characteristics and sili- con film structure in SOI lateral p+ p- n+ diode has been analyzed num erically by using the simulation tool,D...The dependence of the Recombination- Generation( R- G) current on the bulk trap characteristics and sili- con film structure in SOI lateral p+ p- n+ diode has been analyzed num erically by using the simulation tool,DESSIS- ISE.By varying the bulk trap characteristics such as the trap density and energy level spectrum systematically,the dependence of the R- G current on both of them has been dem onstrated in details.Moreover,the silicon film doping concentration and thickness are changed to make silicon body varies from the fully- depletion m ode into the partial- ly- depletion one.The influence of the transfer of silicon body characteristics on the R- G currenthas also been care- fully examined.A better understanding is obtained of the behavior of bulk trap R- G current in the SOI lateral gat- ed- diode.展开更多
A dominant intrinsic luminescence band, which is due to the surface potential barriers of crystalline grains, and an edge doublet, which arises as an LO-phonon repetition of the e-h band, has been revealed in the low-...A dominant intrinsic luminescence band, which is due to the surface potential barriers of crystalline grains, and an edge doublet, which arises as an LO-phonon repetition of the e-h band, has been revealed in the low-temperature photoluminescence spectra of fine-grained obliquely deposited films. Doping film with In impurity leads to quenching of the doublet band, while further thermal treatment causes activation of the intrinsic band, the half-width and the blue shift of the red edge of which correlates with the maximum value of anomalously high photovoltage generated by the film.展开更多
The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge t...The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.展开更多
The multilayered structure thin films(Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb) were prepared through sol-gel and spin-coating method,while the average thinness was nearly 140 nm.We investigated the up-con...The multilayered structure thin films(Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb) were prepared through sol-gel and spin-coating method,while the average thinness was nearly 140 nm.We investigated the up-conversion luminescence of Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,The results show that the double-layer structured thin films are able to increase the emission intensity.The fluorescence enhancement factors of the luminescence from Gd_(2)(MoO_(4))_(3):Ho/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,located at540 and 662 nm,reach 7.5 and 4.3,respectively.And the enhancement factors of emissions located at450,475 and 650 nm(Gd_(2)(MoO_(4))_(3):Tm/Yb@Gd_(2)(MoO_(4))_(3):Yb) reach 9,2 and 2,respectively.The considerable enhancement is due to the suppression of surface quenching and energy harvesting via the Yb ions in the outer shell.In addition,the emission color of thin films can be modulated from yellow to blue via tuning the number of Gd_(2)(MoO_(4))_(3):Ho/Yb and Gd_(2)(MoO_(4))_(3):Tm/Yb layers,which provides a feasible strategy to tune the up-conversion emission color.展开更多
The Indium tin oxide（ITO） thin film possesses excellent photoelectric properties that enable it to act as an ideal transparent conductor.To obtain high-quality ITO films through sol-gel method, the ionic surfactant ...The Indium tin oxide（ITO） thin film possesses excellent photoelectric properties that enable it to act as an ideal transparent conductor.To obtain high-quality ITO films through sol-gel method, the ionic surfactant monoethanolamine and the non-ionic surfactant polyethylene glycol（PEG） were added to the ITO precursor slurry.The influences of surfactants on the structural and photoelectric properties of ITO film samples were investigated.XRD patterns indicated that surfactant monoethanolamine contributed to film predominant grain orientation along the（400） plane.The high transmittance（over 95%） was attributed to the preferred orientation and the grain size expansion of ITO films.SEM showed that the surface particle size and the morphology of ITO films were strongly dependent on the kind of surfactants used.Moving to the shortwave region, the absorption edge of the films exhibited the Burstein-Moss shift.展开更多
The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphi...The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.展开更多
The films deposited at low temperature（LT-films） have increasingly attracted theoretical and technical interests since such films exhibit obvious difference in structure and performances compared to those deposited ...The films deposited at low temperature（LT-films） have increasingly attracted theoretical and technical interests since such films exhibit obvious difference in structure and performances compared to those deposited at room temperature.Studies on the tribological properties of LT-films are rarely reported in available literatures.In this paper,the structure,morphology and tribological properties of Ag films,deposited at LT（166 K） under various Ar pressures on AISI 440C steel substrates by arc ion plating（AIP）,are studied by X-ray diffraction（XRD）,atomic force microscopy（AFM） and a vacuum ball-on-disk tribometer,and compared with the Ag films deposited at RT（300 K）.XRD results show that（200） preferred orientation of the films is promoted at LT and low Ar pressure.The Crystallite sizes are 70 nm-80 nm for LT-Ag films deposited at 0.2 Pa and 0.8 Pa and larger than 100 nm for LT-Ag films deposited at 0.4 Pa and 0.6 Pa,while they are 55 nm-60 nm for RT-Ag films deposited at 0.2 Pa-0.6 Pa and 37 nm for RT-Ag films deposited at 0.8 Pa.The surfaces of LT-Ag films are fibre-like at 0.6 Pa and 0.8 Pa,terrace-like at 0.4 Pa,and sphere-like at 0.2 Pa,while the surfaces of RT-Ag films are composed of sphere-like grains separated by voids.Wear tests reveal that,due to the compact microstructure LT-Ag films have better wear resistances than RT-Ag film.These results indicate that the microstructure and wear resistance of Ag films deposited by AIP can be improved by low temperature deposition.展开更多
VO 2 thin films with good switching properties were prepared by controlling the annealing time and the annealing temperature in a vacuum system. The structural, optical and electrical properties of the samples were ch...VO 2 thin films with good switching properties were prepared by controlling the annealing time and the annealing temperature in a vacuum system. The structural, optical and electrical properties of the samples were characterized by using XRD、XPS、UV-VIS and electrical measurements. The switching parameters of VO 2 thin film were investigated too. The results indicate that before and after phase transition the resistance of VO 2 thin films changes about three orders of magnitude, the variation of film transmittance of 40 % has been carried out with the absorptivity switching velocity of about 0.260 7 /min at 900 nm . The structural property of samples has been improved but the phase-transition properties have been decreased by increasing the annealing time and annealing temperature. The valence of V ions and the structure of samples have great effect on phase transition properties of VO 2 thin films. Discussion on the effects of annealing time and annealing temperature on the phase-transition temperature and hysteresis width shows that the best reasonable annealing time and annealing temperature can be achieved.展开更多
Diamond-like carbon （DLC） films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous s...Diamond-like carbon （DLC） films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous structure and typical characteristics. The topographies of the films are presented by AFM images. Effective thermal conductivities of the films are measured using a nanosecond pulsed photothermal reflectance method. The results show that thermal conductivity is dominated by the microstructure of the films.展开更多
The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characteriz...The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700℃. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite （OZn）, interstitial oxygen （Oi）, interstitial zinc （Zni） and zinc vacancy （VZn^-）, which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.展开更多
In this work,a simple and facile one-pot oleylamine solvothermal synthetic method was developed to synthesize Cu2ZnSnS4（CZTS） nanocrystals.And the Cu2ZnSn（S,Se）4（CZTSSe） thin films were prepared by selenizing CZ...In this work,a simple and facile one-pot oleylamine solvothermal synthetic method was developed to synthesize Cu2ZnSnS4（CZTS） nanocrystals.And the Cu2ZnSn（S,Se）4（CZTSSe） thin films were prepared by selenizing CZTS nanocrystals.The obtained CZTS nanocrystals and CZTSSe films were studied using X-ray diffraction（XRD）,transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDX）,and ultraviolet–visible spectrophotometer（UV–Vis）.TEM results show that the sphere–like CZTS nanoparticles with diameter between 12 and 35 nm are polydispersed.XRD studies indicate that the prepared CZTS nanocrystals form kesterite crystal structure,and the CZTSSe films with kesterite crystal structure are also obtained at the annealing temperatures of 500 and550 °C.In particular after annealing at 500 °C for 20 min,the CZTSSe film exhibits a smooth,uniform,crack-free,and large-grained topography and possesses Cu-poor and Sn-rich composition.Moreover,it shows strong optical absorption from visible to near-infrared（IR） region,and its optical band gap（Eg） is found to be about 1.44 e V.展开更多
Thin films of zinc-doped cadmium oxide with different Zn-doping levels（0, 2, 4, 6, and 8 at%） were deposited on glass substrates by employing an inexpensive, simplified spray technique using perfume atomizer at rela...Thin films of zinc-doped cadmium oxide with different Zn-doping levels（0, 2, 4, 6, and 8 at%） were deposited on glass substrates by employing an inexpensive, simplified spray technique using perfume atomizer at relatively low substrate temperature（375 °C） compared with the conventional spray method. The effect of Zn doping on the structural,morphological, optical, and electrical properties of the films was investigated. XRD patterns revealed that all the films are polycrystalline in nature having cubic crystal structure with a preferential orientation along the（1 1 1） plane irrespective of Zn-doping level. Zn-doping level causes a slight shift in the（1 1 1） diffraction peak toward higher angle. The crystallite size of the films was found to be in the range of 28–37 nm. The band gap value increases with Zn doping and reaches a maximum of 2.65 eV for the film coated with 6 at% Zn doping and for further higher doping concentration it decreases.Electrical studies indicate that Zn doping causes a reduction in the resistivity of the films and a minimum resistivity of15.69 X cm is observed for the film coated with 6 at% Zn.展开更多
The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction...The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm^-2 at the donor density of 10×1018 cm^-3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.展开更多
A kinetic Monte Carlo （kMC） simulation is conducted to study the growth of ultrathin film of Co on Cu（001） surface. The many-body, tight-binding potential model is used in the simulation to represent the interatom...A kinetic Monte Carlo （kMC） simulation is conducted to study the growth of ultrathin film of Co on Cu（001） surface. The many-body, tight-binding potential model is used in the simulation to represent the interatomic potential. The film morphology of heteroepitaxial Co film on a Cu（001） substrate at the transient and final state conditions with various incident energies is simulated. The Co covered area and the thickness of the film growth of the first two layers are investigated. The simulation results show that the incident energy influences the film growth and structure. There exists a transition energy where the interracial roughness is minimum. There are some void regions in the film in the final state, because of the influence of the island growth in the first few layers. In addition, there are deviations from ideal layer-by-layer growth at a coverage from 0 - 2 monolayers （ML）.展开更多
Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2&...Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2·2H_2O] as precursor and isopropanol and monoethanolamine（MEA） as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.展开更多
Single crystal Ga X In 1-X As films have grown up on GaAs(100) substrate at 375℃ and on InP(100) substrate at 390℃, respectively, by the method of rf sputtering with using undoped GaInAs polycrystal as ...Single crystal Ga X In 1-X As films have grown up on GaAs(100) substrate at 375℃ and on InP(100) substrate at 390℃, respectively, by the method of rf sputtering with using undoped GaInAs polycrystal as target. However, on Si(100) or Si(111) substrates at 260～390℃, even at 465℃, only polycrystalline films were obtained. In addition, the structure, composition, electrical characteristic and optical properties of the Ga X In 1-X As films were investigated using X ray diffraction (XRD), reflection of high energy electron diffraction (RHEED), energy dispersion analyzer of X ray (EDAX), Hall measurements and spectroscopic ellipsometry.展开更多
Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic devices.However,such electronic devices need to be subjected to external loads durin...Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic devices.However,such electronic devices need to be subjected to external loads during operation,which can easily induce delamination of the thin-film electronic device from the substrate.This study aims to investigate the instability characteristics of hard films on flexible substrate surfaces from theoretical analysis and numerical simulation perspectives.Considering finite-thickness substrates,this paper establishes theoretical models for pure bending,bent wrinkle,partial delamination,and total delamination buckling of film/substrate structures based on the nonlinear Euler–Bernoulli beam theory and the principle of minimum energy;then the effects of material and geometric parameters of the structure,interfacial adhesion strength,and pre-strain on the evolutionary path of the four patterns are discussed.The study results show that:the greater Young’s modulus of the substrate is,the larger the parameter region where partial delamination of the film/substrate structure occurs,and the smaller the parameter region where bent wrinkle occurs.By varying Young’s modulus,thickness of the film and substrate,interfacial adhesion coefficient,and pre-strain,the buckling pattern of the structure can be predicted and regulated.The parametric design intervals for each pattern are summarized in the phase diagram.The results of this paper provide theoretical support for the design and reliability evaluation of flexible electronic devices.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52433009,22203028)the Natural Science Foundation of Hunan Province,China(Grant No.2024JJ5138).
文摘Donor−acceptor(D−A)conjugated polymers are promising materials for organic transistors including organic field-effect transistors(OFETs)and organic electrochemical transistors(OECTs).The aggregated structure of D−A conjugated polymer films,which strongly depends on the crystallization process,is crucial for the device performance.However,the crystallization of D−A conjugated polymers is complicated during solution processing,and the optimal film structure is various in different applications.Therefore,it is significantly important to reveal the relationship between the processing conditions and the resulting aggregated structures.This review provides a systematic understanding of how to control the aggregated structure of D−A conjugated polymer films from the fundamental mechanisms of polymer crystallization.We first discuss the possible nucleation and growth mechanisms of D−A conjugated polymers based on traditional theories or models and current findings.Then,recent progress in controlling the structure of D−A conjugated polymer films for OFETs and OECTs is reviewed.D−A conjugated polymers generally adopt chain-extended crystallization due to their strongly rigid backbone,which makes homogeneous nucleation difficult.A common strategy to control the aggregated structure of D−A conjugated polymer films is to manipulate the heterogeneous nucleation process by tuning the preaggregation.Besides,the effect of the crystallization rate and complicated conditions on the aggregated structure of D−A conjugated polymer films is also discussed.Finally,a concise summary is provided,followed by some current challenges in controlling the aggregated structure of D−A conjugated polymer films.
基金the National Science Foundation(PFI-008513 and FET-2309403)for the support of this work.
文摘Optical multilayer thin film structures have been widely used in numerous photonic applications.However,existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design targets,or are difficult to suit for different types of structures,e.g.,designing for different materials at each layer.These methods also cannot accommodate versatile design situations under different angles and polarizations.In addition,how to benefit practical fabrications and manufacturing has not been extensively considered yet.In this work,we introduce OptoGPT(Opto Generative Pretrained Transformer),a decoder-only transformer,to solve all these drawbacks and issues simultaneously.
文摘The microstructure of CdI2 thin film grown during vapor-phase deposition was investigated by scanning electron microscopy (SEM). The thin film deposited on Si crystal consists of numerous sunflower-like aggregates. These aggregates display well self-assembly characteristics. The size of Sunflower-like aggregates is between 12 and 44 μm. Each sunflower-like aggregate is surrounded with many adjacent wings-'petals'. The structure of central region of the 'sunflower' is obviously difFerent from that of the 'petal'. Electron spectroscopy for chemical analysis (ESCA) was employed in determining the chemical valence of the thin film. Self-organization efFect is used to explain the coring growth process of CdI2 thin film
基金摩托罗拉和北京大学的联合研究项目!"Gated-Diode Method Application Development and Sensitivity Analysis"的资助 (合同号 :MSPSESTL
文摘The dependence of the Recombination- Generation( R- G) current on the bulk trap characteristics and sili- con film structure in SOI lateral p+ p- n+ diode has been analyzed num erically by using the simulation tool,DESSIS- ISE.By varying the bulk trap characteristics such as the trap density and energy level spectrum systematically,the dependence of the R- G current on both of them has been dem onstrated in details.Moreover,the silicon film doping concentration and thickness are changed to make silicon body varies from the fully- depletion m ode into the partial- ly- depletion one.The influence of the transfer of silicon body characteristics on the R- G currenthas also been care- fully examined.A better understanding is obtained of the behavior of bulk trap R- G current in the SOI lateral gat- ed- diode.
文摘A dominant intrinsic luminescence band, which is due to the surface potential barriers of crystalline grains, and an edge doublet, which arises as an LO-phonon repetition of the e-h band, has been revealed in the low-temperature photoluminescence spectra of fine-grained obliquely deposited films. Doping film with In impurity leads to quenching of the doublet band, while further thermal treatment causes activation of the intrinsic band, the half-width and the blue shift of the red edge of which correlates with the maximum value of anomalously high photovoltage generated by the film.
基金the Fund of Natural Science Founda-tion of Shaanxi Provincial(No.2021JQ-111)the Fund of Basic and Applied Fundamental Research of Guangdong Provincial(No.2020A1515110861).
文摘The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.
基金Project supported by the National Natural Science Foundation of China(11474078)。
文摘The multilayered structure thin films(Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb) were prepared through sol-gel and spin-coating method,while the average thinness was nearly 140 nm.We investigated the up-conversion luminescence of Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,The results show that the double-layer structured thin films are able to increase the emission intensity.The fluorescence enhancement factors of the luminescence from Gd_(2)(MoO_(4))_(3):Ho/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,located at540 and 662 nm,reach 7.5 and 4.3,respectively.And the enhancement factors of emissions located at450,475 and 650 nm(Gd_(2)(MoO_(4))_(3):Tm/Yb@Gd_(2)(MoO_(4))_(3):Yb) reach 9,2 and 2,respectively.The considerable enhancement is due to the suppression of surface quenching and energy harvesting via the Yb ions in the outer shell.In addition,the emission color of thin films can be modulated from yellow to blue via tuning the number of Gd_(2)(MoO_(4))_(3):Ho/Yb and Gd_(2)(MoO_(4))_(3):Tm/Yb layers,which provides a feasible strategy to tune the up-conversion emission color.
基金supported by the National High-Tech Research and Development Program of China (No. 2004AA303542)
文摘The Indium tin oxide（ITO） thin film possesses excellent photoelectric properties that enable it to act as an ideal transparent conductor.To obtain high-quality ITO films through sol-gel method, the ionic surfactant monoethanolamine and the non-ionic surfactant polyethylene glycol（PEG） were added to the ITO precursor slurry.The influences of surfactants on the structural and photoelectric properties of ITO film samples were investigated.XRD patterns indicated that surfactant monoethanolamine contributed to film predominant grain orientation along the（400） plane.The high transmittance（over 95%） was attributed to the preferred orientation and the grain size expansion of ITO films.SEM showed that the surface particle size and the morphology of ITO films were strongly dependent on the kind of surfactants used.Moving to the shortwave region, the absorption edge of the films exhibited the Burstein-Moss shift.
文摘The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.
基金supported by National Basic Research Program of China(973 Project,Grant No.2007CB607601)National Natural Science Foundation of China (Grant No. 50301015)
文摘The films deposited at low temperature（LT-films） have increasingly attracted theoretical and technical interests since such films exhibit obvious difference in structure and performances compared to those deposited at room temperature.Studies on the tribological properties of LT-films are rarely reported in available literatures.In this paper,the structure,morphology and tribological properties of Ag films,deposited at LT（166 K） under various Ar pressures on AISI 440C steel substrates by arc ion plating（AIP）,are studied by X-ray diffraction（XRD）,atomic force microscopy（AFM） and a vacuum ball-on-disk tribometer,and compared with the Ag films deposited at RT（300 K）.XRD results show that（200） preferred orientation of the films is promoted at LT and low Ar pressure.The Crystallite sizes are 70 nm-80 nm for LT-Ag films deposited at 0.2 Pa and 0.8 Pa and larger than 100 nm for LT-Ag films deposited at 0.4 Pa and 0.6 Pa,while they are 55 nm-60 nm for RT-Ag films deposited at 0.2 Pa-0.6 Pa and 37 nm for RT-Ag films deposited at 0.8 Pa.The surfaces of LT-Ag films are fibre-like at 0.6 Pa and 0.8 Pa,terrace-like at 0.4 Pa,and sphere-like at 0.2 Pa,while the surfaces of RT-Ag films are composed of sphere-like grains separated by voids.Wear tests reveal that,due to the compact microstructure LT-Ag films have better wear resistances than RT-Ag film.These results indicate that the microstructure and wear resistance of Ag films deposited by AIP can be improved by low temperature deposition.
文摘VO 2 thin films with good switching properties were prepared by controlling the annealing time and the annealing temperature in a vacuum system. The structural, optical and electrical properties of the samples were characterized by using XRD、XPS、UV-VIS and electrical measurements. The switching parameters of VO 2 thin film were investigated too. The results indicate that before and after phase transition the resistance of VO 2 thin films changes about three orders of magnitude, the variation of film transmittance of 40 % has been carried out with the absorptivity switching velocity of about 0.260 7 /min at 900 nm . The structural property of samples has been improved but the phase-transition properties have been decreased by increasing the annealing time and annealing temperature. The valence of V ions and the structure of samples have great effect on phase transition properties of VO 2 thin films. Discussion on the effects of annealing time and annealing temperature on the phase-transition temperature and hysteresis width shows that the best reasonable annealing time and annealing temperature can be achieved.
基金Supported by the National Natural Science Foundation of China under Grant Nos 90607003 and 60806038, and the National High Technology Research and Development Program of China under Grant Nos 2006AA040106 and 2006AA040102.
文摘Diamond-like carbon （DLC） films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous structure and typical characteristics. The topographies of the films are presented by AFM images. Effective thermal conductivities of the films are measured using a nanosecond pulsed photothermal reflectance method. The results show that thermal conductivity is dominated by the microstructure of the films.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60877029, 10904109, 60907021 and 60977035, the Natural Science Foundation of Tianjin under Grant Nos 09JCYBJC01400 and 07JCYBJC06400, and Tianjin Key Subject for Materials Physics and Chemistry.
文摘The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700℃. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite （OZn）, interstitial oxygen （Oi）, interstitial zinc （Zni） and zinc vacancy （VZn^-）, which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.
基金financially supported by the National Natural Science Foundation of China(Nos.11564027 and 51262020)the Scientific Research Foundation of the Higher Education Institutions of Inner Mongolia Autonomous Region of China(No.NJZY16379)
文摘In this work,a simple and facile one-pot oleylamine solvothermal synthetic method was developed to synthesize Cu2ZnSnS4（CZTS） nanocrystals.And the Cu2ZnSn（S,Se）4（CZTSSe） thin films were prepared by selenizing CZTS nanocrystals.The obtained CZTS nanocrystals and CZTSSe films were studied using X-ray diffraction（XRD）,transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDX）,and ultraviolet–visible spectrophotometer（UV–Vis）.TEM results show that the sphere–like CZTS nanoparticles with diameter between 12 and 35 nm are polydispersed.XRD studies indicate that the prepared CZTS nanocrystals form kesterite crystal structure,and the CZTSSe films with kesterite crystal structure are also obtained at the annealing temperatures of 500 and550 °C.In particular after annealing at 500 °C for 20 min,the CZTSSe film exhibits a smooth,uniform,crack-free,and large-grained topography and possesses Cu-poor and Sn-rich composition.Moreover,it shows strong optical absorption from visible to near-infrared（IR） region,and its optical band gap（Eg） is found to be about 1.44 e V.
文摘Thin films of zinc-doped cadmium oxide with different Zn-doping levels（0, 2, 4, 6, and 8 at%） were deposited on glass substrates by employing an inexpensive, simplified spray technique using perfume atomizer at relatively low substrate temperature（375 °C） compared with the conventional spray method. The effect of Zn doping on the structural,morphological, optical, and electrical properties of the films was investigated. XRD patterns revealed that all the films are polycrystalline in nature having cubic crystal structure with a preferential orientation along the（1 1 1） plane irrespective of Zn-doping level. Zn-doping level causes a slight shift in the（1 1 1） diffraction peak toward higher angle. The crystallite size of the films was found to be in the range of 28–37 nm. The band gap value increases with Zn doping and reaches a maximum of 2.65 eV for the film coated with 6 at% Zn doping and for further higher doping concentration it decreases.Electrical studies indicate that Zn doping causes a reduction in the resistivity of the films and a minimum resistivity of15.69 X cm is observed for the film coated with 6 at% Zn.
文摘The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm^-2 at the donor density of 10×1018 cm^-3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.
基金supported by National Natural Science Foundation of China (Nos.10574047,20490210)China‘973’Plan (No.2006CB921606)
文摘A kinetic Monte Carlo （kMC） simulation is conducted to study the growth of ultrathin film of Co on Cu（001） surface. The many-body, tight-binding potential model is used in the simulation to represent the interatomic potential. The film morphology of heteroepitaxial Co film on a Cu（001） substrate at the transient and final state conditions with various incident energies is simulated. The Co covered area and the thickness of the film growth of the first two layers are investigated. The simulation results show that the incident energy influences the film growth and structure. There exists a transition energy where the interracial roughness is minimum. There are some void regions in the film in the final state, because of the influence of the island growth in the first few layers. In addition, there are deviations from ideal layer-by-layer growth at a coverage from 0 - 2 monolayers （ML）.
文摘Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2·2H_2O] as precursor and isopropanol and monoethanolamine（MEA） as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.
文摘Single crystal Ga X In 1-X As films have grown up on GaAs(100) substrate at 375℃ and on InP(100) substrate at 390℃, respectively, by the method of rf sputtering with using undoped GaInAs polycrystal as target. However, on Si(100) or Si(111) substrates at 260～390℃, even at 465℃, only polycrystalline films were obtained. In addition, the structure, composition, electrical characteristic and optical properties of the Ga X In 1-X As films were investigated using X ray diffraction (XRD), reflection of high energy electron diffraction (RHEED), energy dispersion analyzer of X ray (EDAX), Hall measurements and spectroscopic ellipsometry.
基金funded by the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University(Grant No.2021201712).
文摘Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic devices.However,such electronic devices need to be subjected to external loads during operation,which can easily induce delamination of the thin-film electronic device from the substrate.This study aims to investigate the instability characteristics of hard films on flexible substrate surfaces from theoretical analysis and numerical simulation perspectives.Considering finite-thickness substrates,this paper establishes theoretical models for pure bending,bent wrinkle,partial delamination,and total delamination buckling of film/substrate structures based on the nonlinear Euler–Bernoulli beam theory and the principle of minimum energy;then the effects of material and geometric parameters of the structure,interfacial adhesion strength,and pre-strain on the evolutionary path of the four patterns are discussed.The study results show that:the greater Young’s modulus of the substrate is,the larger the parameter region where partial delamination of the film/substrate structure occurs,and the smaller the parameter region where bent wrinkle occurs.By varying Young’s modulus,thickness of the film and substrate,interfacial adhesion coefficient,and pre-strain,the buckling pattern of the structure can be predicted and regulated.The parametric design intervals for each pattern are summarized in the phase diagram.The results of this paper provide theoretical support for the design and reliability evaluation of flexible electronic devices.
