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...
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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.
A SiO2 buffer layer was introduced to deposite high c-axis oriented LiNbO3 film on Si substrate by radio-frequency (RF) magnetron sputtering technique. The crystal orientation, composition and surface morphology of th...
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A SiO2 buffer layer was introduced to deposite high c-axis oriented LiNbO3 film on Si substrate by radio-frequency (RF) magnetron sputtering technique. The crystal orientation, composition and surface morphology of the thin films were characterized by the X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), and scanning electron microscopy (SEM), respectively. The effects of the amorphous SiO2 buffer layer on the c-axis orientation of LiNbO3 film were investigated. The results show that when the thickness of amorphous SiO2 buffer layer is from 10 nm to 50 nm, the c-axis orientation of LiNbO3 film deposited on Si (100) substrate is enhanced with the increase of the thickness of the amorphous SiO2 buffer layer, but when the thickness of the buffer layer exceeds 30 nm, the change of the c-axis orientation is little;the LiNbO3 film deposited on Si (111) substrate has high c-axis orientation and good crystalline quality, when the thickness of amorphous SiO2 buffer layer is 10 nm. The texture coefficient of the c-axis orientation of LiNbO3 film is 90%, but the c-axis orientation of LiNbO3 film is weakened as the thickness of the buffer layer increases.
The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition （MOCVD） has been studied. Results indicate that the GaP low temperature buffer layer can provide a high densi...
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The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition （MOCVD） has been studied. Results indicate that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature （HT） GaP growth. These sites can promote the two-dimensional （2D） growth of HT GaP and reduce the surface roughness. A GaP single crystal layer grown at 680 ℃ is obtained using a 40-nm thick GaP buffer layer. The full-width at half-maximum （FWHM） of the （111） plane of GaP layer, measured by DCXRD, is 560 arcsec. The GaP layer grown on GaN without low temperature GaP buffer layer shows a rougher surface. However, the FWHM of the （111） plane is 408 arcsec, which is the indication of better crystal quality for the GaP layer grown on GaN without a low temperature buffer layer. Because it provides less nucleation sites grown at high growth temperature, the three-dimensional （3D） growth is prolonged. The crystalline quality of GaP is lightly improved when the surface of GaN substrate is pretreated by PH3, while it turned to be polycrystalline when the substrate is pretreated by TEGa.
The potential of PIN triple-junction Si-based thin film solar cells incorporatiing microcrystalline silicon as sub-cell(a-Si/a-SiGe/μc-Si) with a high conversion efficiency was estimated in terms of transparent condu...
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The potential of PIN triple-junction Si-based thin film solar cells incorporatiing microcrystalline silicon as sub-cell(a-Si/a-SiGe/μc-Si) with a high conversion efficiency was estimated in terms of transparent conductivity oxide(TCO) substrate glass. Only varying μc-Si bottom-cell thickness, it is found that the performance of the triple-junction cells is not affected due to the mid-cell current limit. The quantum efficiency(QE) results of the sub-cells reveal that the ZnO back reflection(BR) layer assists the optical absorption only above 800 nm wavelength.
Series of devices have been made based on a poss end capped polyfluorene and poly (N vinylcarazole) (PVK) as the host, a red Ir complex as the guest. An efficiency of 5.48cd/A was achieved, which surpassed that of dev...
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Series of devices have been made based on a poss end capped polyfluorene and poly (N vinylcarazole) (PVK) as the host, a red Ir complex as the guest. An efficiency of 5.48cd/A was achieved, which surpassed that of device based on PVK as the host. The activity of PVK at the device based on PFO-poss as the host was also studied. We found PVK as the hole-transport layer also participate the process of energy exchange, which can raise the efficiency of the device.
The performance of an organic photovoltaic （OPV） cell based on copper phthatocyanine CuPc/C60 with a tris- （8-hydroxyquinolinato） aluminum （Alq3） buffer layer has been investigated. It was found that the power c...
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The performance of an organic photovoltaic （OPV） cell based on copper phthatocyanine CuPc/C60 with a tris- （8-hydroxyquinolinato） aluminum （Alq3） buffer layer has been investigated. It was found that the power conversion efficiency of the device was 1.51% under illumination with an intensity of 100 mW/cm^2, which was limited by a squareroot dependence of the photocurrent on voltage. The photocurrent optical power density characteristics showed that the OPV cell had a significant space-charge limited photocurrent with a varied saturation voltage and a three quarters power dependence on optical power density. Also, the absorption spectrum was measured by a spectrophotometer, and the results showed that the additional Alq3 layer has a minor effect on photocurrent generation.
A Langmuir-Blodgett （LB） inducing method was firstly used to prepare single layer and multilayer conducting composite PEDOT-PSS film. The film-forming ability of ionization ODA and ODA-SA monolayer spread on PEDOT-P...
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A Langmuir-Blodgett （LB） inducing method was firstly used to prepare single layer and multilayer conducting composite PEDOT-PSS film. The film-forming ability of ionization ODA and ODA-SA monolayer spread on PEDOT-PSS nanoparticle sub-phase and the behavior of ODA/PEDOT-PSS assembly particles on pure water were firstly investigated. The results indicated that nanoparticles in the suphase are packed in the ionization monolayer and stable complex Langmuir film is formed at the air/water interface. It has been found that the best film-forming conditions for composite film are as follows：distinct interface was formed between ODA and PEDOT-PSS layer and single layer thickness of PEDOT-PSS was about 23 nm,well accordant to the size of PEDOT-PSS nanoparticles. Different structures were designed to test the conductive ability of these composite films and a variable range hopping （VRH） model was used to explain the film conductive mechanism. The results indicated that a 3D-VRH model explained well the transferring of charge carrier in the multilayer film.
This talk will address some important issues regarding the μSIRI as an enabling tool for quantitative 3D imaging in microscopy. The main issues to be discussed involve in reformulating the image formation of the μSI...
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This talk will address some important issues regarding the μSIRI as an enabling tool for quantitative 3D imaging in microscopy. The main issues to be discussed involve in reformulating the image formation of the μSIRI by introducing a concept of active micro stereoscopy, characterizing the lateral and longitudinal resolutions of the μSIRI microscopy in three dimensions and suggesting a strategy of calibration for the μSIRI microscope. Some preliminary experiment results are also presented to verify the presented approach.
This paper discusses the influence of Si3N4 barrier layer on photoelectric properties of black silicon photodetector. A barrier layer is added between the black silicon layer and the electrode in the metal-semiconduct...
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This paper discusses the influence of Si3N4 barrier layer on photoelectric properties of black silicon photodetector. A barrier layer is added between the black silicon layer and the electrode in the metal-semiconductor-metal (MSM) structure in order to increase the Schottky barrier, leading to the decrease of the dark current. According to the experiment, under the same lighting condition, the dark current obtained by adding barrier layer is one order of magnitude lower than the one without barrier layer and decreases by one order of magnitude when the thickness of the layer adds every 30 nm, while the photo current does not change obviously. This method lowers noise current and improves the signal-to-noise ratio (SNR) of black silicon photodetector.
Using a novel yellow iridium complex phosphorescent dye of bis[2-(4-tertbutylphenyl) benzothiazolato-N, C2'] iridium (acetylacetonate) [(t-bt)2Ir(acac)] as the ultrathin layer, organic light-emitting devices (OLED...
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Using a novel yellow iridium complex phosphorescent dye of bis[2-(4-tertbutylphenyl) benzothiazolato-N, C2'] iridium (acetylacetonate) [(t-bt)2Ir(acac)] as the ultrathin layer, organic light-emitting devices (OLEDs) are fabricated with a structure of indium tin oxide (ITO)/N, N'-bis(naphthalen-1-yl)-N, N'-bis(phenyl)-benzidine (NPB) (45 nm)/(t-bt)2Ir(acac) (d)/NPB (5 nm)/2, 2', 2″(1, 3, 5-benzenetriyl) tris-(1-phenyl-1H-benzimidazole) (TPBI) (30 nm)/Mg: Ag (200 nm). By changing the thickness of the ultrathin phosphor layer, the OLED properties influenced by the thickness are investigated. The results show that the device with a 0.2-nm-thick phosphor layer has a maximum brightness of 18400 cd/m2. and the white light emission is obtained with commission internationale de l'Eclairage (CIE) coordinates of (0.33, 0.32) at a bias of 6 V. The device with a 0.1-nm-thick phosphor layer has the highest power efficiency of 5.4 lm/W. The analysis indicates that the high performance results from both the direct carriers trapping of phosphor dye to confine the complex emission zone as well as an effective energy transfer from NPB to the phosphor dye.
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