Effect of reduction/oxidation treatment on blue photorefraction in In:Fe:Cu:LiNbO3 crystals

In:Fe:Cu:LiNbO₃ crystals with reduced/oxidized treatments were prepared by the Czochralski method. The defect structure was analyzed by the UV‐Visible absorption spectra. The blue photorefractive properties, such as the refractive index change, response time, recording sensitivity, dynamic range as well as two‐wave coupling gain coefficient, were also investigated at 488 nm wavelength using the two‐wave coupling experiment. Comparing the as‐grown and oxidized In:Fe:Cu:LiNbO₃ crystals, the reduced sample has the highest recording sensitivity and largest dynamic range. Meanwhile, the high diffraction efficiency is still maintained. Experimental results definitely show that reduction treatment is an effective method to improve the blue photorefractive performance of In:Fe:Cu:LiNbO₃ crystals. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of thermal annealing and hydrogen-plasma treatment in boron-doped microcrystalline silicon

We have investigated the effects of temperature (during film growth and post-deposition thermal annealing) and H₂-plasma treatment on the electronic and structural properties of p-type microcrystalline silicon films (p-μc-Si:H) for solar cell applications. The highest dark conductivity is obtained in the thermally annealed p-μc-Si:H prepared at low substrate temperature of 50 °C. This dark conductivity is decreased by two orders of magnitude when the film is exposed to H₂-plasma, being completely restored after thermal annealing. Namely, reversible dual-conductivity cycle is observed between thermally annealed state and H₂-plasma-treated state in p-μc-Si:H. The dual-conductivity cycle is accompanied with the reversible change in the infrared-absorption spectrum at around 1845 cm^? 1 assigned as SiHB complex in p-μc-Si:H network structure. Taking into account of the reversible structural change by H₂-plasma-exposure and thermal-annealing cycles, necessary process-procedure condition has been proposed for obtaining high photovoltaic performance in thin-film-Si solar cells with high quality p-μc-Si:H.     

Enlarged ferromagnetic hysteresis in InMnP:Be epilayers formed by thermal diffusion using MBE-grown Mn/InP:Be bilayers

The p-type InMnP:Be epilayers, which were prepared by thermal diffusion of Mn through in-situ deposition of Mn layer using molecular beam epitaxy (MBE) onto MBE-grown InP:Be epilayers and subsequent in-situ annealing at 300–350 °C, were investigated. InMnP:Be epilayers prepared by the above sequence clearly showed the Mn-related emission band at 1.1–1.2 eV, which indicates the effective incorporation of Mn²⁺ ions into the host layer InP:Be. The samples demonstrated very large ferromagnetic hysteresis loops with enhanced coercivity, and the ferromagnetic-to-paramagnetic transition of the samples was observed to occur at ∼85 K. These results suggest that InP-based ferromagnetic semiconductor layers having enhanced ferromagnetism can be effectively formed by the above-mentioned sequential in-situ processes.     

Phosphorus gettering of precipitated Cu in single crystalline silicon based on rapid thermal process

In this paper, we have investigated the effect of phosphorus diffusion gettering on the precipitated Cu in silicon via rapid thermal process (RTP). It is found that, for dot-like or star-like precipitates, the RTP-based phosphorus diffusion technique is efficient for gettering out the precipitated Cu. A two-step RTP gettering process is much more effective than a single-step RTP process. Furthermore, the choice of oxygen ambient can enhance the Cu gettering efficiency due to the involvement of considerable self-interstitial silicon atoms. The minority carrier lifetime of the sample subjected to RTP-based phosphorus gettering has also been verified to be significantly enhanced. These results are of interest for the gettering engineering of high-efficiency silicon solar cells.     

Influence of thermal treatment upon the diffusion characteristics of Mo in Fe76Mo8Cu1B15 alloy

Mo tracer diffusion in Fe₇₆Mo₈Cu₁B₁₅ alloy was studied using serial sectioning method in the temperature range 548–648 K. Sputtering by Ar⁺ ions was applied as a sectioning technique. The measurement was carried out with the ribbon-like samples in as quenched state (q) and in two states after pre-anneals 683 K/1 h (a1) and 743 K/1 h (a2). The volume fraction of crystalline phase was checked by the Mössbauer spectroscopy. Measured concentration profiles consist of two distinct branches suggesting that two diffusion paths are operating. Diffusion coefficients D_v calculated from the near-surface branch were attributed to Mo volume diffusion in amorphous phase. Their values obtained for (a1) are lower than those obtained for (q) which is due to relaxation of free volume. The higher values, on the other hand, obtained for (a2) are influenced by faster short-circuit diffusion, which was attributed to diffusion in interfacial amorphous phase. Short-circuit diffusivity, P, of Mo was evaluated from concentration tails using both LeClaire’s analysis and Divinski’s theory derived for transition type-A/B regime.     

Effect of heat treatment on the low-temperature thermal conductivities of vitreous silica and neutron-irradiated vitreous silica

Heat treating neutron-irradiated vitreous silica erases the effects of irradiation on the thermal conductivity at temperatures below 1 K. This indicates that the density of low-energy, localized excitations in vitreous silica is restored to its pre-irradiation value.     

Electronic properties of Cu/SiO2/Cu structures at different temperatures

In this experimental work, some electronic properties of vacuum evaporated Cu/SiO₂/Cu structures such as circuiting I_c and emission I_e currents versus the applied voltage, electron attenuation lengths in both copper and SiO₂ layers and the role of the latter layers have been investigated. Experimental results show that these devices undergo an electroforming process leading to resistivity decrease of several orders of magnitude along with a negative resistance region in their current–voltage characteristics. By decreasing the temperature, both I_c and I_e are decreased and at low temperatures the negative resistance region disappears completely. Electron attenuation lengths are measured between 6 and 14 V for copper and SiO₂ layers and their significance are discussed on the base of electron-impurity and electron-defect scatterings. The conduction mechanism is also discussed on the base of a filamentary model.     

Ultra-soft magnetic properties and giant magneto-impedance of Co68Fe4.5Si12·5B15

We have prepared an amorphous Co₆₈Fe_4.5Si_l2·₅B₁₅ alloy, annealed it in the temperature range of 200-580 °C and carried out a detailed study of the effect of crystallization on its magnetic properties. When annealed in an optimized condition, a very high value of initial permeability of the order of ~ 10⁴ has been attained in association with a drastic decrease of the relative loss factor. This change of properties has been attributed due to the formation of nanograins of fcc Co and Co₃B, as identified by X-ray diffraction and differential thermal analysis. The activation energy of crystallization is 4.18 eV. Hysteresis loop parameters were then extensively studied for the samples annealed at various temperatures. Finally, a very high value of giant magneto-impedance (GMI)—which is a characteristic property of Co-based amorphous alloys derived from well defined anisotropy axis (around 375) has been observed for a sample annealed at 380 °C.     

The injected carbon impurities in intermixed GaAs/AlAs multiple quantum wells during thermal treatment

Photoluminescence (PL) measurements were performed in order to investigate the carbon impurity effects on the intermixing behavior of GaAs/AlAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The GaAs/AlAs MQWs were annealed with a carbon source in a furnace annealing system. The PL spectra show that the magnitude of the intermixing of Al and Ga induced by thermal annealing in GaAs/AlAs MQWs increases with depth. The nonuniformity of the intermixing as a function of the depth originated from the carbon impurities which were injected during thermal treatment.     

Epitaxial growth in the (111)Ag/Cu and (111)Au/Cu systems

The initial stages of epitaxial growth in the (111)Ag/Cu and (111)Au/Cu systems were investigated using UHV-RHEED and TEM on the same specimens. Flat, monocrystalline (111)Cu substrates, 1100 Å thick, were formed in situ in the RHEED system on (111)NaCl/mica bilayers. The latter consisted of air-cleaved mica on which 150 Å of NaCl was vacuum-evaporated to form a (111)NaCl monocrystalline film. The NaCl layer allowed easy removal in water of the subsequently deposited bilayer metal film. RHEED showed that these Cu films grew with extremely flat surfaces at 400°C and 10 Å/sec deposition rates. They were then annealed at 500°C for 15 min to reduce their dislocation content and finally used as substrates for subsequent deposition of thin Ag or Au superlayers. The average Ag and Au superlayer thicknesses were varied from fractions of an Angstrom to approximately 20 Å. It was shown that despite the elongated streaks in the RHEED patterns, film growth occurred by an island mechanism, the islands having flat top surfaces. In the initial growth processes, the islands merely thickened. After a few average monolayers were deposited, the islands began to widen, often by means of much thinner islands, finally coalescing into a continuous film. The Au overgrowths became continuous in the 6–11 Å thickness range. In the case of Ag, there still were some open areas in the overgrowth at 20 Å. In both cases the continuous regions of the Ag and Au overgrowths consisted of sharply delineated thick and thin areas that gave rise to steps on the otherwise flat surface.     

BaTiO3/Cu复合材料的制备和性能研究

以Cu为基体,100 nm的BaTiO3颗粒为增强材料,用热压烧结的方法制备了BaTiO3/Cu复合材料,对其微观结构和性能进行了研究.结果表明:当BaTiO3颗粒的加入量为5vol;时,复合材料的微观结构均匀;BaTiO3颗粒的加入量增加到10vol;时,在复合材料中有颗粒团聚体存在.BaTiO3颗粒的加入对BaTiO3/Cu复合材料的硬度影响不大,但能提高其抗弯强度.强度提高的原因是BaTiO3颗粒能阻止位错的移动.动态力学性能检测结果表明:BaTiO3/Cu复合材料的阻尼损耗因子值有较大的提高,而储存模量有较大的下降.BaTiO3颗粒的加入量为5vol;时,BaTiO3/Cu复合材料的阻尼增强效果最佳.BaTiO3/Cu复合材料的阻尼机理可能包括位错阻尼、晶界阻尼、界面阻尼、压电阻尼和压电-导电耗散机制的协同效应.     

The influence of Ag substitution for Cu on glass-forming ability and thermal properties of Mg-based bulk metallic glasses

A group of pseudo-ternary Mg–(Cu–Ag)–Dy bulk metallic glasses (BMGs) was developed by copper mold casting. The glass-forming ability (GFA) is significantly improved by the coexistence of similar elements of Ag and Cu. The critical diameter for glass formation increases from 10 mm for ternary Mg_56.5Cu₃₂Dy_11.5 alloy to 18 mm for pseudo-ternary Mg_56.5Cu₂₇Ag₅Dy_11.5 alloy. Thermal stability, crystallization and melting behaviors of the Mg-based BMGs were evaluated. The decrease of Gibbs free energy difference between undercooled liquid and crystalline phases caused by similar element substitution with optimal amount can be responsible for the increase in GFA of the resulting alloys.     

Cu:KNSBN晶体生长及其光折变效应的研究

在KNSBN晶体中掺进CuO,采用硅钼棒作加热体,以Czochralski技术生长Cu:KNSBN晶体.以二波耦合光路,测试晶体的衍射效率和记录时间,计算折射率变化值Δn.Cu:KNSBN晶体的衍射效率,记录速度和折射率变化值皆高于Fe:LiNbO3晶体.尤其记录速度比Fe:LiNbO3晶体高一个数量级以上.测试Cu:KNSBN晶体位相共轭反射率R和自泵浦位相共轭反射率RC.Cu:KNSBN晶体的自泵浦位相共轭反射率RC值达到64;,是纯KNSBN晶体的二倍.以Cu:KNSBN晶体自泵浦位相共轭镜进行消畸变实验.实验结果表明:输出光波确系输入探测光波的位相共轭光波.     

Effect of thermal history on conductivity and electrical relaxation in alkali silicate glasses

Electrical conductivity σ₀ and electric field relaxation measurements have been carried out as a function of thermal history for two alkali silicate glasses, Na₂O3SiO₂ and K₂O3SiO₂. Specimens of each glass with three different thermal histories, two of the anneal-and-quench type and one of the rate-cool type, were studied. The average structural or fictive temperature T_f of each of the specimens was characterized by measuring their indices of refraction. Effects of thermal history on σ₀ and its activation enthalpy $\text{H}{}_{\mathrm{\sigma }}{}^1$ were in accord with results of previous investigators. That is, for a given type of thermal history σ₀ was lower and $\text{H}{}_{\mathrm{\sigma }}{}^1$ higher the lower T_f. In addition it was found that for two specimens with the same T_f or index of refraction but different thermal histories the rate-cooled specimen exhibited a lower conductivity than the annealed-and-quenched specimen, in accord with the results of Ritland. The distribution of relaxation times τ_σ for decay of the electric field due to ionic migration was found to be due primarily to a distribution in the pre-exponential term ln $\text{τ}{}_{\mathrm{\sigma }}{}^1$ in the equation $\text{ln}\text{τ}{}_{\mathrm{\sigma }}\text{=}\text{ln}\text{τ}{}_{\mathrm{\sigma }}{}^1\text{+ H}{}^1\text{/RT}$; the distribution in $\text{H}{}^1$ was extremely narrow. Differences in thermal history caused small differences in the distribution of τ_σ, but no difference in the average activation enthalpy $\text{〈H}{}^1\text{〉}$ for τ_σ. From this result it appeared that the dependence of the conductivity activation enthalpy $\text{H}{}_{\mathrm{\sigma }}{}^1$ on thermal history was due to the effect of thermal history on the temperature dependence of the distribution in τ_σ.     

预制层衬底加热对Cu2ZnSnS4薄膜性能的影响

本文采用二步法制备Cu2ZnSnS4(CZTS)薄膜,首先通过真空热蒸发制备CuZnSn (CZT)预制层,其衬底加热温度分别为20℃、50℃、75℃和100℃,然后对所制备的CZT预制层在400℃下硫化60 min,从而制备出CZTS薄膜.利用XRD、Raman、SEM、反射谱和透射谱对所制备的CZTS薄膜进行了表征,实验结果表明,预制层衬底加热温度对CZTS薄膜结构与光学特性有很大影响,在衬底加热50℃时制备预制层硫化后所得CZTS薄膜具有高的结晶度、致密均匀的薄膜表面和最佳1.5 eV光学带隙.此外,与衬底未加热制备预制层在500℃和90 min最佳硫化条件下所制备的高纯CZTS薄膜相比,在50℃预制层衬底加热条件下所制备CZTS薄膜具有更好地结晶质量、更低的硫化温度和更短的硫化时间,这种现象表明衬底加热制备金属预制层利于更高品质CZTS薄膜的制备,可有效的降低硫化温度和缩短硫化时间,当前的研究结果为在低温下实现高质量CZTS薄膜的制备提供了一种有效的途径.     

基底温度对ZnO/Cu/ZnO透明导电膜性能的影响

采用射频磁控溅射ZnO陶瓷靶、直流磁控溅射Cu靶的方法在不同基底温度下制备了ZnO/Cu/ZnO多层膜.用X射线衍射仪、原子力显微镜、紫外可见分光光度计和四探针测试仪对样品的性能进行了表征.结果表明,随着基底温度的升高,ZnO层c轴择优取向明显,结晶程度变好,Cu层的结晶性先变好后逐渐变差;多层膜表面均方根粗糙度随基底温度的升高而增加;光学透过率随基底温度的升高逐渐增大,基底温度为300 ℃时最大透过率接近90;;面电阻随基底温度的升高逐渐增加,最小面电阻为12.4 Ω/□.     

Dislocation densities in copper single crystals after thermal treatment

Copper crystals of high purity and doped with nickel were subjected to a long time thermal treatment at 1050°C, in order to reduce the as-grown dislocation density of about 10⁷ cm⁻². A dissolution of the dislocations during their motion to the crystal surface was observed. Regions of different dislocation densities arose. Finally the crystals exhibited constant dislocation densities of 10² cm⁻². Such a perfection or a better one of the crystals is reached only by a long time treatment, since the dislocation velocity without external stresses cannot exceed 1 · 10⁻⁷ cm · s⁻¹ in copper single crystals of high purity.     

Magneto-optical Kerr effect in glass/Cu/CoFeSiB/SnO2 thin films

We report on the Kerr signal enhancement as a result of the capping effect of SnO₂ on the CoFeSiB amorphous layer. The magnetic layer was deposited by pulsed laser deposition method on Cu buffer layer and was capped by SnO₂ with different thicknesses. The magnetic behavior of the samples was investigated by the Kerr effect. As the SnO₂ thickness increased up to about 70 nm, the Kerr signal increased and then reduced. The results were analyzed using the formalism based on the matrix method.     

Effect of Cu additive on the electrical properties of Ge–Se alloy

Electrical measurements have been carried out on a-(Ge₂₀Se₈₀)_100−xCu_x (x = 0.0, 0.5, 1.0, 1.5 and 2.0 at.%) thin films. The dark conductivity (σ_d) and photoconductivity (σ_ph) measurements are done in the temperature range 252–349 K. The values of σ_d, σ_ph increase and dark activation energy (ΔE_d), photo activation energy (ΔE_ph) decrease as the concentration of Cu additive increases (up to 1.0 at.%). Photosensitivity (σ_ph/σ_d) increases and decay time constant (τ_d) decreases as the concentration of Cu increases (up to 1.0 at.%). The charge carrier concentration (n_σ) increases with Cu incorporation (up to 1.0 at.%). A reverse in the trend takes place in all these parameters as the Cu concentration is further increased (>1.0 at.%). These results are explained on the basis of change in the density of defect states present in the mobility gap of Ge–Se–Cu alloy.     

Effect of Cu/In ratio on properties of CuInSe2 thin films prepared by selenization of Cu‐In layers

In this paper, the chalcopyrite CuInSe2 thin films were fabricated from a selenization of electrodeposited Cu‐In layers. In this study, the electrodeposition time of the In layer was set, but that for the Cu layer was not. The thin films were selenized in a sealed glass tube with pure Se powder by three different Cu layer samples at various electrodeposition times at 500 °C for 2 hours. An FE‐SEM image of the sample shows that the copper‐rich product has irregular agglomerates with a dense surface. The X‐ray diffraction patterns show CuInSe₂ peaks for all samples. However, the X‐ray diffraction pattern reveals CuSe₂ peaks when the electrodeposition time of the Cu layer increases. On the other hand, the band gap (E_g) of the samples decreases from 1.15 to 1.07 eV when the Cu/In ratio increases.