基底温度对直流磁控溅射ITO透明导电薄膜性能的影响

用直流磁控溅射法制备透明导电锡掺杂氧化铟(ITO)薄膜,靶材为ITO陶瓷靶,组分为m(In2O3):m(SnO2)=9∶1。运用分光光度计、四探针测试仪研究了基底温度对薄膜透过率、电阻率的影响,并用X射线衍射(XRD)仪对薄膜进行结构分析。计算了晶面间距和晶粒尺寸,分析了薄膜的力学性质。实验结果表明,在实验设备条件下,直流磁控溅射ITO陶瓷靶制备ITO薄膜时,适当的基底温度(200℃)能在保证薄膜85%以上高可见光透过率下,获得最低的电阻率,即基底温度有个最佳值。薄膜的结晶度随着基底温度的提高而提高。

沉积温度对氧化钇稳定氧化锆薄膜残余应力的影响

采用自制掺摩尔分数12%的Y2O3的ZrO2混合颗粒料为原料,在不同的沉积温度下用电子束蒸发方法沉积氧化钇稳定氧化锆(YSZ)薄膜样品。利用ZYGOMarkⅢ-GPI数字波面干涉仪对氧化钇稳定氧化锆薄膜的残余应力进行了研究,讨论了沉积温度对残余应力的影响。实验结果表明:随沉积温度升高,氧化钇稳定氧化锆薄膜中残余应力状态由张应力变为压应力,且压应力值随着沉积温度升高而增大;用X射线衍射仪表征了不同沉积温度下氧化钇稳定氧化锆薄膜的微观结构,探讨了薄膜微观结构与其应力的对应关系,并对比了纯ZrO2薄膜表现出的应力状态。

Laser induced damage threshold at 355 and 1064 nm of Ta2O5 films of different phases

Ta2O5 films are deposited on fused silica substrates by conventional electron beam evaporation method. By annealing at different temperatures, Ta2O5 films of amorphous, hexagonal and orthorhombic phases are obtained and confirmed by x-ray diffractometer ( XRD) results. X-ray photoelectron spectroscopy ( XPS) analysis shows that chemical composition of all the films is stoichiometry. It is found that the amorphous Ta2O5 film achieves the highest laser induced damage threshold ( LIDT) either at 355 or 1064 nm, followed by hexagonal phase and finally orthorhombic phase. The damage morphologies at 355 and 1064 nm are different as the former shows a uniform fused area while the latter is centred on one or more defect points, which is induced by different damage mechanisms. The decrease of the LIDT at 1064nm is attributed to the increasing structural defect, while at 355nm is due to the combination effect of the increasing structural defect and decreasing band gap energy.

Impact of thickness of GaN buffer layer on properties of AlN/GaN distributed Bragg reflectors grown by metalorganic chemical vapor deposition

We studied the impact of the thickness of GaN buffer layer on the properties of distributed Bragg reflector (DBR) grown by metalorganic chemical vapor deposition (MOCVD). The samples were characterized by using metallographic microscope, transmission electron microscope (TEM), atomic force microscopy (AFM), X-ray diffractometer (XRD) and spectrophotometer. The results show that the thickness of the GaN buffer layer can significantly affect the properties of the DBR structure and there is an optimal thickness of the GaN buffer layer. This work would be helpful for the growth of high quality DBR structures.

Structural characteristic of cubic GaN nucleation layers on GaAs(001) substrates by MOCVD

The structural characteristic of cubic GaN (C-GaN) nucleation layers on GaAs(0 0 1) substrates by metalorganic chemical vapor deposition was in detail investigated first by X-ray diffraction (XRD) measurements, using a Huber five-circle diffractometer and an intense synchrotron X-ray source. The XRD results indicate that the C-GaN nucleation layers are highly crystallized. Phi scans and pole figures of the (1 1 1) reflections give a convincing proof that the GaN nucleation layers show exactly cubic symmetrical structure. The GaN(1 1 1) reflections at 54.74degrees in chi are a measurable component, however (002) components parallel to the substrate surface are not detected. Possible explanations are suggested. The pole figures of {1 0 (1) over bar 0} reflections from H-GaN inclusions show that the parasitic H-GaN originates from the C-GaN nucleation layers. The coherence lengths along the close-packed [1 1 1] directions estimated from the (1 1 1) peaks are nanometer order of magnitude. (C) 2002 Elsevier Science B.V. All rights reserved.

Investigation of {111}A and {111} planes of c-GaN epilayers grown on GaAs(001) by MOCVD

A determination of {1 1 1}A and {1 1 1}B in cubic GaN(c-GaN) was investigated by X-ray diffraction technique in detail. The c-GaN films are grown on GaAs(0 0 1) substrates by metalorganic chemical vapor deposition(MOCVD). The difference of integrated intensities measured by omega scan for the different order diffractions from {1 1 1}A and {1 1 1}B planes in the four-circle diffractometer gives convincing evidence as to which is the {1 1 1}A and which is the {1 1 1}B planes. The lesser deviation between the ratios of /F-h k l/(2)//F-(h) over bar (k) over bar (l) over bar/(2) and the calculated values after dispersion correction for atomic scattering factor shows that the content of parasitic hexagonal GaN(h-GaN) grown on c-GaN{1 1 1}A planes is higher than that on {1 1 1}B planes. The reciprocal space mappings provide additional proof that the h-GaN inclusions in c-GaN films appear as lamellar structure. (C) 2001 Published by Elsevier Science B.V.

X-Ray diffraction determination of the fractions of hexagonal and twinned phases in cubic GaN layers grown on (001)GaAs substrate

Being an established qualitative method for investigating presence of additional phases in single crystal materials, X-ray diffraction has been used widely to characterize their structural qualities and to improve the preparation techniques. Here quantitative X-ray diffraction analysis is described which takes into account diffraction geometry and multiplicity factors. Using double-crystal X-ray four-circle diffractometer, pole figures of cubic (002), {111} and hexagonal {10 (1) over bar0} and reciprocal space mapping were measured to investigate the structural characters of mixed phases and to obtain their diffraction geometry and multiplicity factors. The fractions of cubic twins and hexagonal inclusions were calculated by the integrated intensities of rocking curves of cubic (002), cubic twin {111}, hexagonal {10 (1) over bar0} and hexagonal {10 (1) over bar1}. Without multiplicity factors, the calculated results are portions of mixed phases in only one {111} plane of cubic GaN. Diffraction geometry factor can eliminate the effects of omega and X angles on the irradiated surface areas for different scattered planes. (C) 2001 Elsevier Science B.V. All rights reserved.

Microtwins and twin inclusions in the 3C-SiC epilayers grown on Si(001) by APCVD

Microtwins in the 3C-SiC films grown on Si(001) by APCVD were analyzed in detail using an X-ray four-circle diffractometer. The empty set scan shows that 3C-SiC films can grow on Si substrates epitaxially and the epitaxial relationship is revealed as (001)(3C-SiC)//(001)(Si), [111](3C-SiC)//[111](Si). Other diffractions emerged in the pole figures of the (111) 3C-SiC. We performed the (10 (1) over bar0) h-SiC and the reciprocal space mapping of the (002) plane of twins for the first time, finding that the diffractions at chi = 15.8 degrees result from not hexagonal SiC but microtwins of 3C-SiC, and twin inclusions are estimated to be 1%.

Multiplicity factor and diffraction geometry factor for single crystal X-ray diffraction analysis and measurement of phase content in cubic GaN/GaAs(001) epilayers

On the basis of integrated intensity of rocking curves, the multiplicity factor and the diffraction geometry factor for single crystal X-ray diffraction (XRD) analysis were proposed and a general formula for calculating the content of mixed phases was obtained. With a multifunction four-circle X-ray double-crystal diffractometer, pole figures of cubic (002), {111} and hexagonal {1010} and reciprocal space mapping were measured to investigate the distributive character of mixed phases and to obtain their multiplicity factors and diffraction geometry factors. The contents of cubic twins and hexagonal inclusions were calculated by the integrated intensities of rocking curves of cubic (002), cubic twin {111}, hexagonal {1010} and {1011}.

Point defects in III-V compound semiconductors

Point defects in III-V compound semiconductors were analyzed systematically in this paper. The effects of substitutes, antisites, interstitials, and vacancies on lattice parameters in III-V compound semiconductors were calculated with a simple model. The formation energies of vacancies in compound semiconductors can be obtained by this calculation. A practical technique established on this model has been utilized for measuring the stoichiometry in GaAs. The relationship between stoichiometry and deep level centers in GaAs was also investigated.

X-ray-diffraction study of quasipseudomorphic ErSi1.7 layers formed by channeled ion-beam synthesis

ErSi1.7 layers with high crystalline quality (chi(min) of Er is 1.5%) have been formed by 90 keV Er ion implantation to a dose of 1.6X10(17)/cm(2) at 450 degrees C using channeled implantation. The perpendicular and parallel elastic strain e(perpendicular to)=-0.94%+/-0.02% and e(parallel to)=1.24%+/-0.08% of the heteroepitaxial erbium silicide layers have been measured with symmetric and asymmetric x-ray reflections using a double-crystal x-ray diffractometer. The deduced tetragonal distortion e(T(XRD))=e(parallel to)-e(perpendicular to)=2.18%+/-0.10%, which is consistent with the value e(T(RBS))2.14+/-0.17% deduced from the Rutherford backscattering and channeling measurements. The quasipseudomorphic growth of the epilayer and the stiffness along a and c axes of the epilayer deduced from the x-ray diffraction are discussed.

Effects of point defects on lattice parameters of semiconductors

A model for analyzing the correlation between lattice parameters and point defects in semiconductors has been established. The results of this model for analyzing the substitutes in semiconductors are in accordance with those from Vegard's law and experiments. Based on this model, the lattice strains caused by the antisites, the tetrahedral and octahedral single interstitials, and the interstitial couples are analyzed. The superdilation in lattice parameters of GaAs grown at low temperatures by molecular-beam epitaxy can be interpreted by this model, which is in accordance with the experimental results. This model provides a way of analyzing the stoichiometry in bulk and epitaxial compound semiconductors nondestructively.

X-ray diffraction study of GaAs/InAs/GaAs ultrathin single quantum well

Ultrathin single quantum well (about one monolayer) grown on GaAs(001) substrate with GaAs cap layer has been studied by high resolution x-ray diffractometer on a beamline of the Beijing Synchrotron Radiation Facility. The interference fringes on both sides of the GaAs(004) Bragg peak are asymmetric and a range of weak fringes in the higher angle side of the Bragg peak is observed. The simulated results by using the kinematical diffraction method shows that the weak fringe range appears in the higher angle side when the phase shift introduced by the single quantum well is very slightly smaller than m pi (m:integer), and vice versa. After introducing a reasonable model of single quantum well, the simulated pattern is in good agreement with the experiment. (C) 1996 American Institute of Physics.

Magnetic characterization of Co1-xNixFe2O4 (0 <= x <= 1) nanoparticles prepared by co-precipitation route

Magnetic nanoparticles of Ni-doped cobalt ferrite [Co1-xNixFe2O4(0 <= x <= 1)] synthesized by coprecipitation route have been studied as a function of doping concentration (x) and particle size. The size of the particles as determined by X-ray diffractometer (XRD) and transmission electron microscope (TEM) analyses was found in the range 12-48 nm. The coercivity (H-C) and saturation magnetization (M-S) showed a decreasing behavior with increasing Ni concentration. M-S of all the samples annealed at 600 degrees C lies in the range 65.8-13.7 emu/gm. Field-cooled (FC) studies of the samples showed horizontal shift (exchange bias) and vertical shift in the magnetization loop. Strong decrease in exchange bias (H-b) and vertical shift (delta M) was found for low Ni concentrations while negligible decrease was found at higher concentrations. The presence of exchange bias in the low Ni-concentration region has been explained with reference to the interface spins interaction between a surface region (with structural and spin disorder) and a ferrimagnetic core region. M(T) graphs of the samples showed a decreasing trend of blocking temperature (T-b) with increasing Ni concentration. The decrease of T-b with increasing Ni concentration has been attributed to the lower anisotropy energy of Ni+2 ions as compared to Co+2 that increases the probability of the jump across the anisotropy barrier which in turn decreases the blocking temperature of the system.

Structural and photoluminescent properties of ZnO films deposited by radio frequency reactive sputtering

Zinc oxide films with c-axis preferred orientation were deposited on silicon (100) substrates by radio frequency (RF) reactive sputtering. The properties of the samples were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy and fluorescent-spectrophotometer. The effect of sputtering power and substrate temperature on the structural and photoluminescent (PL) properties of the ZnO films was investigated. The results indicated that when the sputtering power is 100 W and the substrate temperature is 300-400 degrees C, it is suitable for the growth of high c-axis orientation and small strain ZnO films. A violet peak at about 380 nm and a blue band at about 430 nm were observed in the room temperature photoluminescence spectra, and the origin of blue emission was investigated.