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1.
Wide band-gap BeZnO layers were grown on Al2O3 (0 0 0 1) substrate using radio-frequency magnetron co-sputtering. The rate of BexZn1−xO crystallized as a hexagonal structure was x=0.2. From the X-ray photoelectron spectroscopy measurement, the O–Zn bonds relating the crystal structure and the Be–O bonds related to the deviation of the stoichiometry in the BeZnO layer were caught at 530.4 and 531.7 eV in the O 1s spectrum, respectively. Thus, the observance on the Be 1s peak of 113.2 eV associated with the bonding Be–O indicates that the sputtered Be atoms are substituted for the host-lattice site in ZnO. This Be–O bonding shows a relatively low intense and broadening spectrum caused by large fluctuation of Be content in the BeZnO layer. From the photoluminescence and transmittance measurement, the free exciton and the neutral donor-bound exciton (D0, X) emissions were observed at 3.7692 and 3.7313 eV, respectively, and an average transmittance rate over 95% was achieved in a wide ultraviolet (UV)–visible region. Also, the binding energy for the (D0, X) emission was extracted to be 37.9 meV. Through the wide band-gap material BeZnO, we may open some possibilities for fabricating a ZnO-based UV light-emitting diode to be utilized as a barrier layer comprised of the ZnO/BeZnO quantum well structure and/or an UV light emitting material itself.  相似文献   

2.
Indium-doped Cd1−xZnxTe (CZT:In) single crystals were annealed by a two-step method, including a high-temperature step and a low-temperature step in sequence. IR transmittance spectrum, IV curve and PL spectrum were used to characterize the CZT single crystals. After annealing, the opto-electrical properties of the CZT:In crystals were improved obviously. The average IR transmittance was remarkably increased by about 23%, and the resistivity was enhanced by as high as four orders of magnitude. In the PL spectra, the intensity of the (D0, X) peak prominently increased, and the full-width-at-half-maximum was reduced. Meanwhile, the intensity of the DAP peak decreased greatly, and the structure became practically indistinguishable from the background. Moreover, the intensity of the Dcomplex peak also decreased. The investigation shows that these improvements in the physical properties after annealing are due to variations in the micro-structures. The two-step annealing method can eliminate precipitates/inclusions, remove impurities, compensate Cd vacancies, decrease dislocations and reduce internal stress.  相似文献   

3.
InxAl1−xN is a particularly useful group-III nitride alloy because by adjusting its composition it can be lattice matched to GaN. Such lattice-matched layers may find application in distributed Bragg reflectors (DBRs) and high electron mobility transistors (HEMTs). However, compared with other semiconducting nitride alloys, InxAl1-xN has not been researched extensively. In this study, thin InxAl1−xN epilayers were grown by metal-organic vapour phase epitaxy (MOVPE) on GaN and AlyGa1−yN layers. Samples were subjected to annealing at their growth temperature of 790 °C for varying lengths of time, or alternatively to a temperature ramp to 1000 °C. Their subsequent surface morphologies were analysed by atomic force microscopy (AFM). For both unstrained InxAl1−xN epilayers grown on GaN and compressively strained epilayers grown on AlyGa1−yN, surface features and fissures were seen to develop as a consequence of thermal treatment, resulting in surface roughening. It is possible that these features are caused by the loss of In-rich material formed on spinodal decomposition. Additionally, trends seen in the strained InxAl1−xN layers may suggest that the presence of biaxial strain stabilises the alloy by suppressing the spinode and shifting it to higher indium compositions.  相似文献   

4.
High quality Zn1−xFexO thin films were deposited on α-sapphireα-sapphire substrates by RF magnetron sputtering. X-ray absorption fine structure measurements showed that the chemical valence of Fe ions in the films was a mixture of 2+ and 3+ states, and Fe ions substituted mainly for the Zn sites in the films. DC-magnetization measurements revealed ferromagnetic properties from 5 to 300 K. The photoluminescence measurements at 15 K showed a sharp main transition peak at 3.35 eV along with a broad impurity peak at 2.45 eV. The structural and magnetization analyses of the Zn1−xFexO films strongly suggested that the ferromagnetism was the intrinsic properties of the films.  相似文献   

5.
Cd1−xZnxS films with 0x0.18 were grown by chemical bath deposition technique on glass substrates from an aqueous solution containing cadmium and zinc sulfate, ammonia and thiourea. Microstructural features, obtained from X-ray diffraction and scanning electron microscopy (SEM) measurements, reveal a predominance of Wurtzite structure and an homogenous microstructure formed by densely microcrystallines for all the samples studied. Cd1−xZnxS semiconductor was found to be resistive and of n-type. Also, the electron density decreases with increased x and the mobility reaches a maximum around x=0.12. Which means that the Cd1−xZnxS films at this composition are of high crystalline quality, i.e. having reduced intrinsic defect concentrations.  相似文献   

6.
The thermal stability of ∼200-nm-thick InGaN thin films on GaN was investigated using isothermal and isochronal post-growth anneals. The InxGa1−xN films (x=0.08–0.18) were annealed in N2 at 600–1000 °C for 15–60 min, and the resulting film degradation was monitored using X-ray diffraction (XRD) and photoluminescence (PL) measurements. As expected, films with higher indium concentration showed more evidence for decomposition than the samples with lower indium concentration. Also for each alloy composition, decreases in the PL intensity were observed starting at much lower temperatures compared to decreases in the XRD intensity. This difference in sensitivity of the PL and XRD techniques to the InGaN decomposition suggest that defects that quench luminescence are generated prior to the onset of structural decomposition. For the higher indium concentration films, the bulk decomposition proceeds by forming metallic indium and gallium regions as observed by XRD. For the 18% indium concentration film, measurement of the temperature-dependent InGaN decomposition yields an activation energy, EA, of 0.87±0.07 eV, which is similar to the EA for bulk InN decomposition. The InGaN integrated XRD signal of the 18% film displays an exponential decrease vs. time, implying InGaN decomposition proceeds via a first-order reaction mechanism.  相似文献   

7.
The recent results on the growth of the AlxGa1−xN bulk single crystals (0.22≤x≤0.91) from solution in liquid Ga under high nitrogen pressure are discussed. We focus on the influence of temperature and the choice of the Al source on the crystal growth. The experiments involving different sources of aluminum such as Al metal, pre-reacted polycrystalline AlyGa1−yN and AlN powder are compared. The best results were achieved using pre-reacted polycrystalline AlyGa1−yN or/and AlN. Single-crystal structure refinement data of these AlxGa1−xN crystals are presented. We also update the p–T phase diagram of (Al,Ga)N compound at high N2 pressure for various Al content, which is the basis for (Al,Ga)N synthesis.  相似文献   

8.
Near-stoichiometric LiTaO3 (SLT) and Zn-doped near-stoichiometric LiTaO3 (Zn:SLT) crystals with 10–15 mm in diameter and 10 mm in length were grown by using TSSG technique with K2O as the flux. The effect of adding amount of K2O was discussed in the growing process. The crystals were characterized by inductively coupled plasma-optical emission (ICP-OES), X-ray diffraction (XRD) and differential thermal analysis (DTA). The lattice constants of Zn:SLT were smaller than those of SLT and Curie temperature was higher than that of SLT. It was found that Zn doping is an efficient way to improve the optical damage resistance ability of SLT crystal. Compared with SLT crystal, Zn:SLT exhibited a much higher optical damage threshold, more than 500 MW/cm2, which was attributed to Zn self-compensated effect that formed the charge compensated complexes, (ZnTa)3−–3(ZnLi)+ in SLT crystal.  相似文献   

9.
No biocompatible Ti-based glassy alloys without a harmful element have been reported. We have examined the mechanical and chemical properties of Ti-Pd-Zr-Si glassy alloy in comparison with pure Ti metal and Ti-6Al-4V alloy which have been used so far for biomaterials. The present Ti-Pd base glassy alloys do not contain Al and Ni elements which are considered to be rather toxic. Melt-spun Ti45Zr50−xPdxSi5 glassy alloy ribbons (x = 35, 40, 45) exhibited good bend ductility and had higher Vickers’s hardness and lower Young’s modulus as compared to pure titanium and Ti-6Al-4V alloy. In addition, the Ti45Zr50−xPdxSi5 glassy alloys had higher corrosion resistance and were passivated over a wide range and at the lower passive current density of approximately 10−2 Am−2 than at of pure titanium and Ti-6Al-4V alloy in 1 mass% lactic acid and PBS(−) solutions at 310 K.  相似文献   

10.
High-quality ZnMgO films were grown by the radio frequency (RF) magnetron sputtering technique in pure oxygen ambient. Single-crystal films were obtained, when the Mg concentration was Zn0.87Mg0.13O or lower in the case of ZnMgO/Al2O3 and when it was Zn0.65Mg0.35O or lower in the case of ZnMgO/ZnO. Polycrystalline films were obtained when the growth temperature was lower than 500 °C, regardless of the Mg concentration. Position of the photoluminescence (PL) ultraviolet (UV) peak of the ZnMgO film shifted with the addition of Mg, from 3.33 eV (ZnO) to 3.51 eV (Zn0.87Mg0.13O) and 3.70 eV (Zn0.65Mg0.35O). It was also observed that growth of the ZnMgO films at higher temperature resulted in higher band-gap energy. It was proposed that this phenomenon is because concentration of the substitutional Mg atoms occupying Zn site is increased as the growth temperature increases.  相似文献   

11.
Zn1‐xCdxO layers were deposited on the sapphire substrate using the radio‐frequency magnetron co‐sputtering system. The grown Zn1‐xCdxO layers were carried out in the post‐annealing treatment for 1 min at the 800 °C oxygen‐ambient by the rapid thermal annealing (RTA) method. X‐ray diffraction (XRD) experiment shows that the Zn1‐xCdxO layers are changed from the single phase of the hexagonal structure at 0≤x ≤0.08 to the double phase of hexagonal‐and‐cubic structure at x =0.13. Thus, the maximum Cd‐composition ratio with the hexagonal structure was found out to be x =0.08. Also, the crystallinity of Zn1‐xCdxO layers at x =0.13 was remarkably improved by the RTA annealing treatment. This crystal quality improvement was thought to be associated with the relaxation of the compressive strain remaining in the Zn1‐xCdxO layers. Therefore, the results of XRD and transmittance lead that the crystal quality of the Zn1‐xCdxO layers forming the hexagonal ZnO phase is better than that forming the cubic CdO phase. Consequently, the reliable formation and the crystallinity of the Zn1‐xCdxO layers were achieved by using the RTA method of short‐time thermal‐annealing at the high temperature. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
Photoluminescence (PL) emitted from Cd1‐xZnxS and CdS1‐ySey solid solution semiconductor was significantly stronger than PL from the pure CdS and CdSe semiconductor. The samples were prepared using an improved Se‐S‐Na2S flux route. Photoluminescence in Cd1‐xZnxS crystal was brightly yellow at the room temperature under VU radiation. The phase and composition of the solid solution was measured by the XRD and was confirmed by UV‐NIS spectrum as x of 0.3 and y of 0.2. The enhanced photoluminescence was presumably due to the introduction of extra defect (vacancies) by solid solution action and consequently the increasing of luminescence center concentration. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
A route for synthesizing high Mg content single-phase wurtzite MgZnO films having band gaps in the solar-blind region is demonstrated by employing molecular beam epitaxy on Al2O3 substrates. Importantly, a low Mg content “quasi-homo” buffer, Mg0.17Zn0.83O, was applied to accommodate a host of structural discrepancies and therefore, avoiding phase separation in a high Mg content film, Mg0.55Zn0.45O, as proved by X-ray diffraction. The Mg fraction in the overgrown single-phase epilayer, Mg0.55Zn0.45O, was confirmed by Rutherford backscattering spectrometry.  相似文献   

14.
J.S. Zhang  J. Yan  W. Liang  E.L. Du  C.X. Xu 《Journal of Non》2009,355(14-15):836-839
Two kinds of Mg-rich and low neodymium Mg–Zn–Nd alloys including icosahedral quasicrystal phase (I-phase) were prepared under conventional casting conditions. The microstructures and phases of Mg–Zn–Nd quasicrystal alloys were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The results indicate that the I-phase in Mg–Zn–Nd quasicrystal alloy is a simple icosahedral quasicrystal with quasi-lattice of aR = 0.525 nm. It has been proved that the as-cast Mg70.8Zn28Nd1.2 quasicrystal alloy mainly consisted of I-phase and Mg7Zn3 matrix phase. While the as-cast Mg70.5Zn28.5Nd1 alloy mainly consisted of I-phase, Mg7Zn3 matrix phase, dendrite α-Mg phase and a new rod-like hexagonal phase.  相似文献   

15.
16.
In the present paper, the effect of carbon on the microstructural evolution of Zr66.7−xNi33.3Cx (x = 0, 1, 3) alloys during mechanical alloying has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that these three alloys undergo similar amorphization and crystallization processes, and the final milling product is a metastable fcc-Zr66.7−xNi33.3Cx phase. The carbon addition can shorten the milling time for the complete amorphization reaction and enhance the stability of the formed amorphous alloy, which can suppress the mechanically induced amorphous-crystalline phase transformation with further increasing milling time.  相似文献   

17.
Optical properties related to lattice vibrations of bulk Zn1‐xBexSe, Zn1‐x‐yBexMnySe and Cd1‐xBexSe alloys are reported. Optical phonons of the mixed crystals grown by the Bridgman method have been investigated by infrared spectroscopic ellipsometry in the wave‐number range 300‐8000 cm‐1. The complex dielectric functions can be reproduced using a model with two or three classical damped oscillators corresponding to the BeSe‐like transverse‐optical phonon‐modes and a Drude contribution from the free carriers. The frequencies of longitudinal‐optical phonons have been found from the imaginary parts of the dielectric loss functions. The influence of the alloy composition on the zone‐centre optical phonon frequencies is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

18.
X.Y. Li  A.X. Lu  Zh.H. Xiao  Ch.G. Zuo 《Journal of Non》2008,354(31):3678-3684
Two series (A and B series) of oxynitride glasses were prepared by melting batches at 1580 °C for 3 h under local CO reducing atmosphere in a Si-Mo-heated resistance furnace. Nominal compositions of A and B series glasses in equivalent percent (eq.%) are (28−x)Y:xMg:48Si:24Al:83O:17N and (28−x)Y:xMg:56Si:16Al:83O:17N (x = 0, 7, 14, 21), respectively. The influences of Mg/Y and Al/Si ratios on the properties such as glass transition temperature (Tg), crystallization temperature (TC), knoop hardness (H), three-point bending strength (σ) and chemical durability in 20%HF were investigated. At the same time, the relationship between these properties and the structures of the glasses were discussed. At constant ratio Si-Al-O-N, Tg decreases nonlinearly but glass leaching ratio increases linearly with increasing Mg/Y ratio. However, H and σ increase first and then decrease as the Mg/Y ratio increases. When the Y/Mg/O/N ratio is constant, Tg decreases slightly but H and σ increase slightly as the Al/Si ratio increases.  相似文献   

19.
The use of a selenium–tellurium (SeTe) mixed source in the isothermal close space sublimation growth of CdSe epilayers is considered. The epitaxial growth was performed in flowing helium by sequential exposures of the substrate to vapors of the mixed SeTe source and elemental cadmium at temperatures within 350–410 °C. In spite of the mixed source (proposed to decrease the partial pressure of Se), tellurium incorporation was small and CdSexTe(1−x) (x∼0.98) epilayers were obtained. X-ray diffraction reciprocal space mapping shows the existence of hexagonal inclusions mainly on the (1 1 1) facets of the cubic phase. Material deposition on areas of the graphite crucible exposed to the sources, contamination of the Cd source and large growth rates suggest the existence of a selenium transport process via graphite. This transport might be the result of the combination of selenium deposition on graphite with a subsequent activated desorption of selenium under cadmium exposure. It affects Cd source purity and growth kinetic bringing on a modification of the usual atomic layer deposition regimen; however, a reproducible growth rate of the epilayers was obtained.  相似文献   

20.
Refractory bulk metallic glasses and bulk metallic glass composites are formed in quaternary Ni-Nb-Ta-Sn alloy system. Alloys of composition Ni60(Nb100−xTax)34Sn6 (x = 20, 40, 60, 80) alloys were prepared by injection-casting the molten alloys into copper molds. Glassy alloys are formed in the thickness of half mm strips. With thicker strips (e.g., 1 mm), Nb2O5 and Ni3Sn phases and the amorphous phase form an in situ composite. Glass transition temperatures, crystallization temperatures, and ΔTx, defined as Tx1 − Tg (Tx1: first crystallization temperature, Tg: glass transition temperature) of the alloys increase dramatically with increasing Ta contents. These refractory bulk amorphous alloys exhibit high Young’s modulus (155-170 GPa), shear modulus (56-63 GPa), and estimated yield strength (3-3.6 GPa).  相似文献   

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