用于液晶光阀空间光调制器的ITO透明导电膜的研制

本文介绍了ITO(Indium Tin Oxide)透明导电膜的制备工艺,对影响其光学和电学特性的因素作了分析。并讨论了透明导电的机理,在K9玻璃上制备的ITO透明导电膜,在500～600nm波长范围内,典型的峰值透过率为90％,面电阻为40～50Ω/□。用该技术制备的样品作为透明电极,在液晶光阀空间光调制器中得到了应用。     

Electrical transport properties of single GaN and InN nanowires

The transport properties of single GaN and InN nanowires grown by thermal catalytic chemical vapor deposition were measured as a function of temperature, annealing condition (for GaN) and length/square of radius ratio (for InN). The as-grown GaN nanowires were insulating and exhibited n-type conductivity (n ≈ 2×10¹⁷ cm⁻³, mobility of 30 cm²/V s) after annealing at 700°C. A simple fabrication process for GaN nanowire field-effect transistors on Si substrates was employed to measure the temperature dependence of resistance. The transport was dominated by tunneling in these annealed nanowires. InN nanowires showed resistivity on the order of 4×10⁻⁴ Ω cm and the specific contact resistivity for unalloyed Pd/Ti/Pt/Au ohmic contacts was near 1.09×10⁻⁷ Ω cm². For In N nanowires with diameters <100 nm, the total resistance did not increase linearly with length/square of radius ratio but decreased exponentially, presumably due to more pronounced surface effect. The temperature dependence of resistance showed a positive temperature coefficient and a functional form characteristic of metallic conduction in the InN nanowires.     

Electrical and optical properties of deep ultraviolet transparent conductive Ga2O3/ITO films by magnetron sputtering

Ga2O3/ITO films were prepared by magnetron sputtering on quartz glass substrates. The transmittance and sheet resistance of ITO films and Ga2O3/ITO films were measured by using a double beam spectrophotometer and four point probes. The effect of the ITO layer and Ga2O3 layer thickness on the electrical and optical properties of Ga2O3/ITO bi-layer films were investigated in detail. Ga2O3 (50 nm)/ITO (23 nm) films exhibited a low sheet resistance of 323 Ω/□ and high deep ultraviolet transmittance of 77.6% at a wavelength of 280 nm. The ITO layer controls the ultraviolet transmittance and sheet resistance of Ga2O3/ITO films. The Ga2O3 layer thickness has a marked effect on the transmission spectral shape of Ga2O3/ITO films in the violet spectral region.     

Electrical and optical properties of ITO and ITO:Zr transparent conducting films

ITO and ITO:Zr films were deposited on glass substrates by magnetron sputtering. Electrical and optical properties of the films at different experiment parameters such as substrate temperature, oxygen flow rate and annealing temperature were contrastively studied. The increase in substrate temperature remarkably improves the electrical and optical properties of the films. ITO:Zr films show better quality at low substrate temperature. The excessive oxygen can worsen the optical properties of the films. Better optical–electrical properties of the films can be achieved after the proper annealing treatment. Obvious Burstin–Moss effect can be revealed by transmittance spectra with different parameters, and the direct transition models show the change of optical band gap. ITO:Zr films prepared by co-sputtering show better optical–electrical properties than ITO films.     

磁控溅射制备Ga2O3/ITO深紫外透明导电膜的光电性能

采用磁控溅射方法在石英玻璃基底上制备了Ga2O3/ITO膜,用紫外-可见分光光度计、四探针测试仪对ITO膜和 Ga2O3/ITO膜的光学透过率和面电阻进行了表征,详细研究了ITO层和Ga2O3层的厚度对Ga2O3/ITO双层膜光电性能的影响。研究表明,Ga2O3(50nm) /ITO(23nm)膜在280nm处的深紫外光学透过率高达77.6%,面电阻为323Ω/sq;ITO层控制Ga2O3/ITO膜的面电阻,影响Ga2O3/ITO膜的紫外透过率;Ga2O3层厚度调控Ga2O3/ITO膜的紫外区域的光谱形状。     

Rigorous optical modeling and optimization of thin‐film photovoltaic cells with textured transparent conductive oxides

Typical thin‐film photovoltaic (PV) cells incorporate a textured transparent conductive oxide to enhance light trapping and efficiently harvest solar energy. Rigorous coherent optical simulations of these devices and a complete characterization of these textured films are a challenging problem because of the several orders of magnitude difference between the wavelengths of interest and the spatial dimension of the sample that needs to be evaluated. In this paper, a practical approach for rigorous and predictive modeling of optical properties of thin‐film PV cells incorporating a vast variety of light‐trapping structures including semi‐coherent textured films and patterned coherent structures is presented. In contrast to the existing semi‐empirical device models, it is demonstrated that the presented methodology can accurately predict the scattering properties of textured fluorine‐doped tin oxide and aluminum‐doped zinc oxide conductive transparent films. It is further shown that the optical response of single‐junction and tandem‐junction PV devices incorporating such films can also be predicted with good accuracy as compared with the measured results. Next, a methodology to identify the sufficient statistical fingerprints of semi‐coherent textured films that are needed to unambiguously predict the light propagation in thin‐film cells is presented. This comprehensive approach then lends itself to identifying the optimal surface morphology needed for strong light trapping. This rigorous approach automatically includes the effects of important loss mechanisms such as the surface plasmon‐enhanced absorption in textured metal surfaces that are otherwise very difficult to account for semi‐coherent approaches based on scalar scattering theory. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrical and optical properties of transparent flexible electrodes: Effects of UV ozone and oxygen plasma treatments

“Flextrodes” are flexible transparent electrodes consisting of ZnO(100 nm)/PEDOT:PSS/silver grid/polyethylene terephthalate (PET) fabricated using a roll-to-roll process. Flextrodes provide a zinc oxide surface on a high-conductivity electrode while maintaining reasonable transparency and good flexibility. They are optimized for use as cathodes (i.e. low work functions) in inverted organic solar cells (OSCs). As-received Flextrode samples have a surface contamination layer that insulates. Prior to use in OSCs, this contamination layer needs to be removed. We tested two surface cleaning methods, i.e., UV-ozone and oxygen plasma, with various treatment times. After cleaning samples were characterized in terms of water contact angle, UV–visible transmittance, and 4-point probe conductivity, using conductive atomic force microscopy, and X-ray/ultraviolet photoelectron spectroscopy. Based on these measurements, we identified optimal conditions and were able to recover work functions of 3.4–3.6 eV without damaging the Flextrodes.     

Electrical and optical properties of N-type Alx Ga1-x as grown by MO-VPE

Growth conditions and properties of Al_xGa_1-xAs (0.1 ≤ × ≤O.3) using metalorganic vapour phase epitaxy (MO-VPE) are investigated. N-type is achieved either by silicon or by selenium doping. Properties of the layers are evaluated by Hall effect, cathodoluminescence and photoluminescence. It is shown that selenium doping leads to luminescent material : when x = O.1, the efficiency is only a factor of 2 smaller than for GaAs. Deposition temperature is a critical parameter : increasing the growth temperature yields more luminescent Al_x Ga_1-x As. This work has been partly supported by the Délégation à la Recherche Scientifique et Technique (D.G.R.S.T.)     

Morphology and crystalline property of an AlN single crystal grown on AlN seed

AlN single crystal grown by physical vapor transport (PVT) using homogeneous seed is considered as the most promising approach to obtain high-quality AlN boule. In this work, the morphology of AlN single crystals grown under different modes (3D islands and single spiral center) were investigated. It is proved that, within an optimized thermal distribution chamber system, the surface temperature of AlN seed plays an important role in crystal growth, revealing a direct relationship between growth mode and growth condition. Notably, a high-quality AlN crystal, with (002) and (102) reflection peaks of 65 and 36 arcsec at full width at half maximum (FWHM), was obtained grown under a single spiral center mode. And on which, a high-quality Al_xGa_1–xN epitaxial layer with high Al content (x = 0.54) was also obtained. The FWHMs of (002) and (102) reflection of Al_xGa_1–xN were 202 and 496 arcsec, respectively, which shows superiority over their counterpart grown on SiC or a sapphire substrate.     

Morphology and crystalline property of an AIN single crystal grown on AIN seed

AIN single crystal grown by physical vapor transport (PVT) using homogeneous seed is considered as the most promising approach to obtain high-quality AIN boule.In this work,the morphology of AIN single crystals grown under different modes (3D islands and single spiral center) were investigated.It is proved that,within an optimized thermal distribution chamber system,the surface temperature of AIN seed plays an important role in crystal growth,revealing a direct relationship between growth mode and growth condition.Notably,a high-quality AIN crystal,with (002) and (102) reflection peaks of 65 and 36 arcsec at full width at half maximum (FWHM),was obtained grown under a single spiral center mode.And on which,a high-quality AlxGa1-xN epitaxial layer with high Al content (x =0.54) was also obtained.The FWHMs of (002) and (102) reflection of AlxGa1-xN were 202 and 496 arcsec,respectively,which shows superiority over their counterpart grown on SiC or a sapphire substrate.     

扩散温度和时间对晶体硅太阳电池性能的影响

研究了薄层方块电阻对单晶硅太阳电池的开路电压(Voc)、短路电流(Isc)、填充因子(FF)和转换效率(η)的影响。通过控制扩散温度和时间制备了具有不同薄层方块电阻的单晶硅太阳电池。结果表明:当扩散温度和时间分别为863℃和1 050 s时,电池性能得到了有效的改善,其平均开路电压、短路电流、填充因子和转换效率分别为0.64 V,5.58 A,0.755和17.3%。     

Effect of seed layers (Al,Ti) on optical and morphology of Fe-doped ZnO thin film nanowires grown on Si substrate via electron beam evaporation

The effects of Al and Ti seed layers were studied for undoped and Fe-doped ZnO thin films deposited on n-type Si substrates by electron beam (e-beam) evaporation. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The films grown on seed layers showed wurtzite hexagonal crystal nanorod and nanowire structures. A higher angle phase shift was observed in the doped thin films compared to the pristine ZnO films. Microstructural studies confirmed the growth of nanorods and nanowires with average widths of ~32 nm and ~8–29 nm, respectively. The nanostructures were denser and more crystalline on the Al seed layer than on the Ti seed layer for the doped thin films. However, in the undoped thin films, a more crystalline nature was observed on the Ti seeded layer than the Al seeded layer.     

Electrical and optical properties of copper indium ditelluride crystals grown from near-stoichiometric compositions

CuInTe₂ crystals grown by zone-leveling of nominally stoichiometric material are highly p-type. The net acceptor density is reduced by in-diffusion of zinc which acts as a donor impurity. Zinc-annealed crystals transmit in the infrared and exhibit an absorption edge at 0.92 eV.     

Structural,optical dispersion and dielectric properties of novel chromium nickel organic crystalline semiconductors

A novel organic crystalline semiconductor, [Cr(DPPP)(DPPM)(Ni-ap)(CO)₂] (Cr–Ni OSC) (6a), (DPPP=diphenylphosphino-propanone, DPPM=diphenylphosphino-methane and Ni-ap=nickel apyrazole ring) (6a) was synthesized. Structural characteristics of the Cr–Ni OSC complex have been investigated by IR, ¹HNMR, ³¹P NMR, thermal analysis (TG/DTA), and XRD. Thermal analysis of Cr–Ni OSC implies that, the complex was thermally stable up to 218 °C, and the melting point of it was 193 °C. Two discrete regions of (44.46%, 128–421 °C) and (41.15%, 600–823 °C) by TG analysis of Cr–Ni OSC complex was determined. XRD crystal data of Cr–Ni OSC showed the formation of monoclinic (P2₁/n). Transmittance and reflectance have been used to determine the optical dispersion and dielectric properties of the Cr–Ni OSC complex in the range of 200–800 nm. The transparency of the complex is 75–80% in the visible range. The optical and transport energy gaps were estimated as 1.87 eV and 2.01 eV respectively. Optical dispersion parameters have been calculated by using single term Sellmeier dispersion relation and Wemple–DiDomenico single oscillator model. Several dispersion parameters were determined by analysis of refractive index dispersion. The optical conductivity, surface and volume energy loss functions, and the electric modulus were also estimated from the optical dielectric constant analysis.     

Characteristics and optical properties of MgO nanowires synthesized by solvothermal method

Magnesium oxide (MgO) nanowires were synthesized by solvothermal method using magnesium nitrate hexahydrate and sodium hydroxide. Field emission scanning electron microscopy (FE-SEM) and transmission scanning electron microscopy (TEM) measurements indicate that the product consists of a large quantity of nanowires with average diameter of 20 nm and average length of several micrometers. Explorations of X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), Fourier transformer infrared spectroscopy (FTIR), selected area electronic diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) indicate that the product is high-quality cubic single-crystalline nanowires. The optical properties of the samples are investigated using UV–visible spectroscopy to study the refractive index and optical dielectric constant. The photoluminescence (PL) measurement suggests that the product has an intensive emission centered at 437 nm, showing that the product has potential application in optical devices. The advantages of our method lie in high yield, the easy availability of the starting materials and allowing their large-scale production at low cost.     

Electrical and optical properties of lodine doped CdZnTe layers grown by metalorganic vapor phase epitaxy

Electrical and photoluminescence properties of iodine doped CdZnTe (CZT) layers grown by metalorganic vapor phase epitaxy have been studied. Doped layers showed an n-type conductivity from the Zn composition x=0 (CdTe) to 0.07. Above x=0.07, resistivities of doped layers increased steeply up to 10⁶ Ω-cm. Resistivities of doped CZT layers were higher than those of undoped layers above x=0.6. Photoluminescence intensity of doped layers increased compared to undoped layers. Doped CdTe and ZnTe layers showed neutral donor bound exciton emission lines at the exciton related region. Also, these layers showed an increase in emission intensity at the donor acceptor pair recombination bands. Sharp emission lines were observed in doped CZT layers at around 1.49 eV. These emission lines were considered to be originated from GaAs substrates which were optically excited by the intense emission from doped CZT layers.     

Electrical and optical properties of oxygen doped GaN grown by MOCVD using N2O

Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N₂O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried ammonia using nitrogen (N₂) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface. Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N₂O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations in the range of 4×10¹⁶ cm⁻³ to 4×10¹⁸ cm⁻³ as measured by Hall effect. The observed carrier concentration increased with increasing N₂O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B exciton emission an exciton bound to a shallow donor. With increasing N₂O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons. These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius and electronegativity arguments.     

单晶CuS纳米线的电沉积合成及结构表征

采用多孔AAO模板辅助的有机溶剂电化学沉积技术,制备出尺寸均匀,平均直径30nm的单晶CuS纳米线。利用透射电子显微技术研究了纳米线的晶体结构和元素成分,分析了不同沉积电流密度对CuS纳米晶形核及生长过程的影响。研究结果表明,电流密度过小,容易导致S单质向S2-还原速度竞争不过Cu2+与S2-反应成核的速度,从而出现Cu34S32(即CuS0.95);电流密度过大,则会导致成核过程抑制生长过程,得到的CuS纳米晶均为多晶形态。