Nd掺杂对BiFeO3薄膜微结构和电学性能的影响

采用化学溶液方法,在LaNiO3/Si(100)衬底上生长了Nd掺杂的BiFeO3薄膜.XRD分析结果表明,随着Nd掺杂量的增加,薄膜晶格变小,Nd掺杂量为20%时,薄膜出现杂相.介电测试表明,随着Nd掺杂量的增加,介电常数和损耗减小,Nd掺杂量为2%的薄膜表现出很强的介电色散现象并出现介电损耗弛豫峰,其符合类德拜模型特征.随着Nd掺杂量增加,薄膜的漏电流减小,在低电场下,电流输运遵从SCLC模型,在高场下,电流输运遵循Poole-Frenkel模型.分析结果表明Nd掺杂对薄膜微结构和电学性能有显著影响.     

Peak effect in Jc of the cation-stoichiometric SmBa2Cu3Oy superconductor

Cation-stoichometic SmBa₂Cu₃O_7−d samples were prepared by a solid-state reaction method and exhibited a peak effect in their J_c vs H characteristics. Oxygen contents of the samples were determined by a coulometric titration method. A sample annealed at 350°C for 40 h showed the largest peak among those studied in this work. The oxygen content of this sample was 7−d=6.84, which was lower than those of other samples. Tetragonal regions were revealed in the orthorhombic matrix of this sample by a transmission electron microscope (TEM) observation. On the other hand, a sample annealed at the same temperature (350°C) for a long period (200 h) showed a small peak. The former sample was thought to contain some oxygen deficiency which would play a role of pinning centers to cause a peak effect in the J_c vs H characteristics.     

Effect of multistep annealing on mechanical and surface properties of electroplated Cu thin films

Electroplated (EP) Cu films demonstrate a microstructural transition at room temperature, known as self-annealing, that involves grain growth and texture changes. In this paper, we have investigated the annealing behavior of EP Cu films grown on a Cu seed layer deposited on top of a TaN barrier layer. A grazing incident x-ray diffraction (GIXRD) pattern shows stronger x-ray reflections form Cu (111) and (220) planes but weaker reflections from (200), (311), and (222) planes in all the EP Cu samples. Nanoindentation was performed on all the samples using the continuous stiffness measurement technique. The elastic modulus varied from 121 GPa to 132 GPa, while the hardness varied from 1 GPa to 1.3 GPa, depending on the annealing conditions. The surface morphology and roughness of the Cu films were characterized using atomic force microscopy (AFM). The tribological properties of the copper films were measured using the Bench Top chemical mechanical polishing (CMP) tester (CETR, Inc., Campbell, CA). Nanoindentation was performed on the samples after CMP, and an increase in hardness and modulus was observed. This may be attributed to the work hardening of the Cu films during CMP.     

The effect of strain on abnormal grain growth in Cu thin films

To understand a grain growth mechanism in Cu thin films that were deposited on rigid substrates by sputter deposition and subsequently annealed at various temperatures, microstructures of the Cu films with or without the rigid substrates were analyzed by x-ray diffraction (XRD), transmission electron microscopy (TEM), and electrical resistivity measurements. Significant grain growth (with bimodal grain size distribution) was observed during room-temperature storage in the Cu films deposited on the Si₃N₄ and rock salt substrates. However, in the free-standing Cu films, no grain growth was observed during room temperature storage. The present result suggested that the grain growth rates in the Cu thin films were strongly influenced by the existence of the rigid substrates, indicating stress (or strain) introduced in the films was a primary factor to induce the grain growth in the Cu films.     

Microstructure of high Jc NdBa2Cu3Ox/Nd4Ba2Cu2O10 composite superconductor

Single crystalline NdBa₂Cu₃O_x (Nd123) superconductors with dispersed Nd₄Ba₂Cu₂O₁₀ (Nd422) particles were produced by the floating zone partial melting and solidification (FZPMS) method. The initial composition of the precursor material was Nd_1.8Ba_2.4Cu_3.4O_x with or without 0.1 wt% Pt addition. FZPMS was carried out in a low oxygen partial pressure atmosphere. Microstructure of quenched samples were investigated by optical microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Furthermore, superconductive properties were measured by superconducting quantum interference device (SQUID). The results of SQUID measurements indicate that the critical temperature (T_c) of the samples with Pt addition so produced with the oxygen heat treatment (623 K for 300 h) was 94 K and the critical current density (J_c) was 2.3×10⁴ A/cm² at 77 K, 0.2 T.     

Y1Ba2Cu3O7-x半导体薄膜的红外热辐射响应研究

采用直流磁控溅射后退火法制备了Y1Ba2Cu3O7-x/Si和Y1Ba2Cu3O7-x/ZrO2/SiO2两种半导体薄膜，对该薄膜进行了红外热辐射响应特性研究。采用X射线衍射、电阻温度系数法、喇曼散射表征手段对薄膜的显段结构进行了详细分析。结果表明，有过渡层的Y1Ba2Cu3O7-x半导体薄膜均匀性好，信噪比高，在红外波段和亚毫米波段甚至毫米波段都有良好的热辐射响应，适于制做非制冷探测器的敏感元。     

Processing of large YBa2 Cu3Ox domains for levitation applications by a Nd1+x Ba2−x Cu3 Oy-Seeded melt-growth technique

YBa₂Cu₃O_x domains for levitation applications have been produced by a seeding technology that includes Nd_1+x Ba_2−x Cu₃O_y seeds and melt-processing technologies such as conventional melt-textured growth, melt-texturing with PtO₂ and Y₂BaCuO₅ additions, and the new solid-liquid-melt-growth technology. Large domains (∼20 mm) with high levitation forces (F₁ up to 8.2 N) have been produced. The reproducibility of the results is good, and the capability of producing a large number of pellets in a single batch indicates good potential for the production of large amounts of this material.     

Photoelectric properties of Cu2ZnSnS4 thin films deposited by thermal evaporation

正Sn/Cu/ZnS precursor were deposited by evaporation on soda lime glass at room temperature,and then polycrystalline thin films of Cu_2ZnSnS_4(CZTS) were produced by sulfurizing the precursors in a sulfur atmosphere at a temperature of 550℃for 3 h.Fabricated CZTS thin films were characterized by X-ray diffraction,energy dispersive X-ray spectroscopy,ultraviolet-visible-near infrared spectrophotometry,the Hall effect system,and 3D optical microscopy.The experimental results show that,when the ratios of[Cu]/([Zn]+[Sn]) and[Zn]/[Sn]in the CZTS are 0.83 and 1.15,the CZTS thin films possess an absorption coefficient of larger than 4.0 x 10~4 cm~(-1) in the energy range 1.5-3.5 eV,and a direct band gap of about 1.47 eV.The carrier concentration,resistivity and mobility of the CZTS film are 6.98 x 10~(16) cm~(-3),6.96Ω-cm,and 12.9 cm~2/(V-s),respectively and the conduction type is p-type.Therefore,the CZTS thin films are suitable for absorption layers of solar cells.     

The effect of annealing on the properties of Ga2O3 anodic films

The effect of annealing and oxygen plasma on the electrical characteristics of gallium oxide films has been investigated. Ga₂O₃ films with thicknesses of 200–300 nm were formed by the anodic oxidation of n-GaAs wafers with the donor concentration N _d = (1–2) × 10¹⁶ cm⁻³. It is shown that, after annealing at 900°C for 30 min, the gallium arsenide films contain only the β Ga₂O₃ phase. The effect of the duration of oxygen plasma treatment prior to annealing on the nucleation of β-phase crystallites with different orientations has been studied. It has been established that the electrical conductivity of the Ga₂O₃ films can be managed by annealing and variation in the duration of oxygen plasma treatment. It is shown that the response of the V/Ni-GaAs-Ga₂O₃-V/Ni structure to a mixture exhaled by a person depends on the value and sign of the potential on the control electrode.     

The effect of annealing on the physical properties of thermally evaporated CuIn2n+1S3n+2 thin films (n=0, 1, 2 and 3)

In this study, the annealing effect on structural, electrical and optical properties of CuIn_2n+1S_3n+2 thin films (n=0, 1, 2 and 3) are investigated. CuIn_2n+1S_3n+2 films were elaborated by vacuum thermal evaporation and annealed at 150 and 250 °C during 2 h in air atmosphere. XRD data analysis shows that CuInS₂ and CuIn₃S₅ (n=0 and 1) crystallize in the chalcopyrite structure according to a preferential direction (112), CuIn₅S₈ and CuIn₇S₁₁ (n=2 and 3) crystallize in the cubic spinel structure with a preferential direction (311). The optical characterization allowed us to determine the optical constants (refractive indexes 2.2–3.1, optical thicknesses 250–500 nm, coefficients of absorption 10⁵ cm^?1, coefficients of extinction <1, and the values of the optical transitions 1.80–2.22 eV) of the samples of all materials. We exploited the models of Cauchy, Wemple–DiDomenico and Spitzer–Fan for the analysis of the dispersion of the refractive index and the determination of the optical and dielectric constants.     

Interfacial properties of YBa2Cu3O7−x thin films on AI2O3 substrates prepared by pulsed laser deposition

The interfaces of YBa₂Cu₃O_7−x (YBCO) superconducting thin films grown on (1 102) r-plane A1₂O₃ by pulsed laser deposition have been investigated by a transmission electron microscopy and an Auger electron spectroscopy depth profile. We used the PrBa₂Cu₃O_7−x (PBCO) buffer layer to prevent the interdiffusion and compared the interfaces of YBCO/A1₂O₃ and YBCO/PBCO/A1₂O₃. The intermediate layer in the YBCO film deposited on bare sapphire is visible between the film and the substrate but no boundary layer in the film grown on PBCO buffered sapphire was observed directly by the cross-section image of TEM. The thickness of the intermediate layer in the film on bare sapphire is about 30 nm. This result of TEM observation is consistent with that of AES depth profile.     

Achieving superconductivity through reductive treatments of YSr2(Cu1−xFex)3Oy

In order to obtain massive Fe nano clustering coexisting with superconductivity, the dependence of the structural, magnetic, and superconductive properties of YSr₂(Cu_1−xFe_x)₃O_y (x < 0.13 or x < 0.167) on annealing conditions is explored. Materials are initially prepared by conventional solid state technique with an annealing for two days at T < 1000K and is termed oxygenating preparation (OP). The materials treated by OP method show no signs of superconductivity above 5K. Subsequently, Gd getter annealing is used to control reductions at T < 1000K for four days followed by reoxidation at 800K for 1 h and is termed reducing preparation (RP). For x < 0.13, the RP treatment results in the development of superconductivity with T_c-onset< 40K. For x < 0.167, a T_c-onset< 30K is achieved. A local thermodynamic model based on the stabilities of various Fe cluster arrangements is used to explain the effect of the thermal treatments.     

The effect of electromotive-force generation on electrical properties of thin samarium sulfide films

Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300–580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440–470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects.     

Influence of Cu doping on physical properties of sol-gel processed SnS thin films

Copper-doped tin sulfide thin films (Cu-SnS) with different Cu doping concentrations were prepared by using the spin coating technique and their structural, electrical, and optical properties were studied. All the prepared films were polycrystalline and exhibited diffraction peaks corresponding to orthorhombic SnS with the preferred (111) orientation. The XRD spectra revealed improvement in the preferential orientation and crystalline quality with up to 4% Cu doping concentration, whereas Cu doping concentrations above 4% deteriorate the preferential orientation and crystalline quality. It has been observed that upon Cu doping the band gap decreased significantly from 1.46 eV (pure SnS) to 1.37 eV (4% of Cu-doped SnS). Hall measurements revealed the p-type semiconducting nature of the SnS thin films. The observations revealed that doping of SnS with Cu causes a noticeable drop in the room-temperature resistivity value from 10⁵ Ω-cm for pure SnS to 10³ Ω-cm for 4% Cu-doped SnS.     

The microstructure and physical properties of thin SnO2 films

Thin polycrystalline SnO₂ films were deposited on glass substrates by magnetron sputtering. Electrical, optical, and gas-sensing properties, as well as the structure and phase composition of the films, were studied. The electrical resistance of the films and the concentration and mobility of free charge carriers were determined by the four-point-probe and van der Pauw methods. The band gap and the type of optical transitions in the films were derived from optical absorption spectra. The sensitivity to toxic and explosive gases was measured. The composition, morphology, and crystal structure of the films annealed at 600°C were examined by X-ray diffraction and electron microscopy. The films were found to contain only a tetragonal SnO₂ phase and have good crystallinity. The average grain size in the annealed films is 11–19 nm. A model of the electrical conduction in the polycrystalline SnO₂ films is discussed.     

Preparation of high Tc (Yb,Y)Ba2Cu3O7-δ thin films by co-evaporation from effusion cells

We have prepared superconducting thin films of (Yb,Y)Ba₂Cu₃O_7-δ by evaporation of copper, ytterbium or yttrium, and barium fluoride from Knudsen effusion cells. A simple two chamber vacuum system produced stable evaporation rates of 5–10 nm/min using various Knudsen cells without realtime feedback control. Excellent stoichiometry was obtained in the films by optimizing the deposition of Cu from a dual filament cell, Yb from a single filament cell and Y and BaF₂ from high temperature cells. Films were deposited mainly on SrTiO₃ substrates at temperatures ranging from 120 to 600° C and O₂ partial pressure up to 1.5 ⋻ 10⁻⁵ Torr. Post deposition anneals in O₂ and O₂ + H₂O produced films with room temperature resistivities as low as 227μΩ-cm andT _c (R = 0) at 91 K. Films were characterized using x-ray diffractometry, Rutherford backscattering spectrometry, energy dispersive x-ray analysis, scanning electron microscopy as well as electronic transport measurements.     

The effect of Sn impurity on the optical and structural properties of thin silicon films

The effect of tin impurity on the structure and optical properties of thin-film amorphous silicon is investigated. It is established that tin impurity accelerates crystallization of amorphous silicon. Immediately after deposition of a film onto a substrate at a temperature of ∼300°C, there is a crystalline phase of silicon in samples with tin. High-vacuum annealing at 350–750°C leads to growth of the crystalline phase in films with tin: nanocrystals grow in size from ∼3.0 to 4.5 nm. At the same time, in films without tin, only the degree of the short-range order increases. Silicon film without tin remains amorphous over the entire range of annealing temperatures.     

制备参数和后处理对ZnO薄膜光学性质的影响

采用脉冲激光沉积技术在不同生长气氛氧压(10-3pa1、0-2Pa、10-1Pa、1Pa、10Pa)和生长衬底温度(250~600℃)下制备了高度c轴取向的ZnO薄膜。光致发光(PL)光谱表明,氧压和衬底温度对ZnO的光学性质有重要影响。制备紫外(UV)发射强的ZnO薄膜,要综合考虑氧压和衬底温度两个参数,衬底温度升高,氧气氛压强要相应升高。进一步研究表明,在化学配比失衡的情况下,升高衬底温度和退火会在ZnO中产生缺陷和杂质束缚电子态,束缚电子态引起的晶格弛豫使局域电子态发生多声子无辐射跃迁,ZnO深能级发射由辐射复合变为无辐射复合。     

Preparation and gas-sensing properties of α-Fe2O3 thin films

Haematite (α-Fe₂O₃) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe₂O₃ films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.