Optical properties of La2O3 doped diamond-like carbon films

A novel kind of La₂O₃ doped diamond-like carbon (DLC) films with thickness of 100-120 nm were deposited by unbalanced magnetron sputtering. Raman spectra and photoluminescence properties were measured by Raman spectrometer operated by 325 nm He-Cd laser and 514 nm Ar⁺ laser, respectively. The intensities of Raman spectra and photoluminescence are higher than those of pure DLC films. The La₂O₃ doped DLC films have the potential promising for the application of solar cell coatings.     

Fabrication and photoluminescence characteristics of In2O3 nanohillocks

Uniformly distributed polycrystalline indium nanohillocks are synthesized on silicon substrates with Au catalyst by using the radio frequency magnetic sputtering technique. The results show that the Au catalyst plays a key role in the formation of indium nanohillocks. After thermally oxidizing the indium nanohillocks at 500 ℃ in air for 5 h, the indium nanohillocks totally transform into In₂O₃ nanohillocks. The energy-dispersive X-ray spectroscopy result indicates that many oxygen vacancies and oxygen-indium vacancy pairs exist in the In₂O₃ nanohillocks. Photoluminescence spectra under an Ne laser excitation at 280 nm show broad emissions at 420 nm and 470 nm with a shoulder at 450 nm related to oxygen vacancies and oxygen-indium vacancies at room temperature.     

Optical properties of p-type CuAlO2 thin film grown by rf magnetron sputtering

We report the structural and optical properties of copper aluminium oxide (CuAlO₂) thin films, which were prepared on c-plane sapphire substrates by the radio frequency magnetron sputtering method. X-ray photoelectron spectroscopy (XPS) along with X-ray diffraction (XRD) analysis confirms that the films consist of delafossite CuAlO₂ phase only. The optical absorption studies show the indirect and direct bandgap is 1.8 eV and 3.45 eV, respectively. Room temperature photoluminescence (PL) measurements show three emission peaks at 360 nm (3.45 eV), 470 nm (2.63 eV) and 590 nm (2.1 eV). The first one is near band edge emission while the other two are originated from defects.     

Si/SiO2 multilayers: synthesis by reactive magnetron sputtering and photoluminescence emission

This paper relates a complete study of Si/SiO₂ multilayer (ML) structures. First, we suggest an original way of synthesis based on reactive magnetron sputtering of a pure silica target. The photoluminescence spectra of these MLs consist of two Gaussian bands in the visible-near infrared spectral region. The stronger one (I band) is fixed at about 780 nm and probably due to interface states. The weaker one (Q band) is tuneable with the Si sublayer thickness and originates from a radiative recombination within the nanosized Si layers. For this latter band the peak position is a function of the Si sublayer thickness and shows a discontinuity at 30 Å. This corresponds to an Si phase change. For thicknesses above 30 Å, the sublayers are composed of nanocrystalline silicon whereas below 30 Å the sublayers are made of amorphous silicon. We develop a model based on a quantum well to which we have added an interfacial region between Si and SiO₂. It is characterised by an interfacial potential of 0.3 eV. This model depicts the simultaneous behaviour of Q and I bands for an Si sublayer thickness below 30 Å.     

Investigation of the electrical properties of metal-oxide-metal structures formed from RF magnetron sputtering deposited MgTiO3 films

Thin films of MgTiO₃ high-k dielectric have been prepared by RF magnetron sputtering deposition at various substrate temperatures. X-ray diffraction, atomic force microscopy were used to characterize the deposited films. Experimental results show that substrate temperature has little effect on the stoichinometry. The electrical properties of MgTiO₃ metal-insulator-metal (MIM) capacitors were investigated at various deposition temperatures, Pt/MgTiO₃/Pt/SiO₂/n-Si, were studied. It is shown that the MgTiO₃ (210 nm) MIM capacitor fabricated at 200 °C shows an overall high performance, such as a high capacitance density of ∼1.2 nF/um², a low leakage current of 1.51 × 10⁻⁹ A/cm² at 5 V, low-voltage coefficients of capacitance, and good frequency dispersion properties. All of these indicate that the MgTiO₃ MIM capacitors are very suitable for use in Si analog circuit application or dynamic random access memory (DRAM) cell.     

Effects of O2/Ar ratio and annealing temperature on electrical properties of Ta2O5 film prepared by magnetron sputtering

The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies.     

Characterization of single-crystalline In2O3 films deposited on Y-stabilized ZrO2 (1 0 0) substrates by MOCVD

Epitaxial In₂O₃ films have been deposited on Y-stabilized ZrO₂ (YSZ) (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). The films were deposited at different substrate temperatures (450-750 °C). The film deposited at 650 °C has the best crystalline quality, and observation of the interface area shows a clear cube-on-cube epitaxial relationship of In₂O₃(1 0 0)||YSZ(1 0 0) with In₂O₃[0 0 1]||YSZ[0 0 1]. The Hall mobility of the single-crystalline In₂O₃ film deposited at 650 °C is as high as 66.5 cm² V⁻¹ s⁻¹ with carrier concentration of 1.5 × 10¹⁹ cm⁻³ and resistivity of 6.3 × 10⁻³ Ω cm. The absolute average transmittance of the obtained films in the visible range exceeds 95%.     

Response improvement for In2O3-TiO2 thick film gas sensors

In₂O₃ is introduced into TiO₂ by sol-gel method to improve the response/recovery rate and expand the operating temperature, when the In₂O₃-TiO₂ mixed system is exposed to H₂/O₂. The sensor is fabricated by thick film technology. Influence of In₂O₃ on the film phase composition, microstructure and sensing characteristics is discussed. Dynamic response properties show that the operating temperature of the mixed system is at 500-800 °C, which is about 600-800 °C for pure TiO₂. Response time of the sensor is about 200-260 ms (millisecond) while recovery time is in a narrow range of 60-280 ms at 600-800 °C. The promoting mechanism is suggested to arise from the introduction of In₂O₃ and grain size effect of the sensing film. Then In₂O₃-TiO₂ thick films are surface-modified by Pt using chloroplatinic acid. The promoting effect of Pt dispersed on the mixed system is also investigated.     

Synthesis and electrical properties of In2O3(ZnO)m superlattice nanobelt

One-dimensional（ID） In₂O₃（ZnO）_m superlattice nanobelts are synthesized by a chemical vapor deposition method.The formation of the In₂O₃（ZnO）_m superlattice is verified by the high-resolution transmission electron microscopy images.The typical zigzag boundaries could be clearly observed.An additional peak at 614 cm^-1 is found in the Raman spectrum,which may correspond to the superlattice structure.The study about the electrical transport properties reveals that the In₂O₃（ZnO）_m nanobelts exhibit peculiar nonlinear I-V characteristics even under the Ohmic contact measurement condition,which are different from the Ohmic behaviors of the In-doped ZnO nanobelts.The photoelectrical measurements show the differences in the photocurrent property between them,and their transport mechanisms are also discussed.     

Photocatalytic TiO2 thin films deposited on flexible substrates by radio frequency (RF) reactive magnetron sputtering

Titanium dioxide (TiO₂) thin films were deposited on flexible polycarbonate (PC) substrates by radio frequency (RF) reactive magnetron sputtering. The target was metallic titanium, argon was the plasma gas and oxygen was the reactive gas. Taguchi’s method, which uses an L₉ (3⁴) orthogonal array, signal-to-noise ratio and analysis of variance (ANOVA), was employed to study the performance of the deposition process. The effects of the deposition parameters on the structure, morphology and photocatalytic performance of the TiO₂ films were analyzed using scanning electron microscopy (SEM), X-ray diffraction, and UV-vis-NIR spectroscopy. Experiments varied RF power (50, 100, 150 W), deposition time (2, 3, 4 h), O₂/(Ar + O₂) argon/oxygen ratios (40, 60, 80%) and substrate temperatures (room, 80, 120 °C), to optimize the photoinduced decomposition of methylene blue (MB). The experimental results illustrate the effectiveness of this approach.     

磁控溅射法合成纳米β-FeSi2/a-Si多层结构

β-FeSi₂作为一种环境友好的半导体材料，颗粒化及非晶化正在成为提高其应用性能和改善薄膜质量、膜基界面失配度的有效途径.利用射频磁控溅射法在单晶Si基体上沉积Fe/Si多层膜，合成纳米β-FeSi₂/Si多层结构.通过透射电子显微镜、高分辨电子显微术等分析手段，研究了多层结构和制备工艺之间的相互关系.研究结果表明，采用磁控溅射Fe/Si多层膜的方法，不需要退火就可以直接沉积得到β-FeSi₂相小颗粒.β-FeSi₂相 关键词： 2')" href="#">β-FeSi₂ 磁控溅射 透射电子显微镜 半导体薄膜     

射频磁控反应溅射制备的Ag2O薄膜的椭圆偏振光谱研究

Ag₂O薄膜在新型超高存储密度光盘和磁光盘方面具有潜在的应用前景.利用射频磁控反应溅射技术, 通过调节衬底温度在沉积气压为0.2 Pa、氧氩比为2:3的条件下制备了一系列Ag₂O 薄膜.利用通用振子模型(包括1个Tauc-Lorentz振子和2个Lorentz 振子)拟合了薄膜的椭圆偏振光谱.在1.5-3.5 eV能量区间,薄膜的折射率在2.2-2.7之间, 消光系数在0.3-0.9之间. 在3.5-4.5 eV能量区间,薄膜呈现了明显的反常色散,揭示Ag₂O薄膜的等离子体振荡频率在 3.5-4.5 eV之间. 随着衬底温度的升高,薄膜的光学吸收边总体上发生了红移, 该红移归结于薄膜晶格微观应变随衬底温度的升高而增大. Ag₂O薄膜的光学常数表现出典型的介质材料特性.     

Chemical quenching of positronium in Fe2O3/Al2O3 catalysts

Fe₂O₃/Al₂O₃ catalysts were prepared by solid state reaction method using α-Fe₂O₃ and γ-Al₂O₃ nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ₃ and τ₄ are attributed to positronium annihilation in two types of pores distributed inside Al₂O₃ grain and between the grains, respectively. With increasing Fe₂O₃ content from 3 wt% to 40 wt%, the lifetime τ₃ keeps nearly unchanged, while the longest lifetime τ₄ shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe₂O₃ content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ₄ is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores.     

Optimization of annealing conditions of In2S3 thin films deposited by vacuum thermal evaporation

In₂S₃ thin films were grown on glass substrates by means of the vacuum thermal evaporation technique and subsequently thermally annealed in nitrogen and free air atmosphere from 250 to 350 °C for different durations. Experimental parameters have been adjusted in order to optimize the annealing conditions, and to obtain high band gap energy at low deposition temperature, as required for photovoltaic applications. In order to improve our understanding of the influence of the deposition and annealing parameters on device performance, we have investigated our indium sulfide material by X-ray diffraction, energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM) and spectrophotometry. The optical and structural properties of the films were studied as a function of the annealing temperature and durations. X-ray diffraction analysis shows the initial amorphous nature of deposited In-S thin films and the phase transition into crystalline In₂S₃ upon thermal annealing. Films show a good homogeneity and optical direct band gap energy about 2.2 eV. An annealing temperature of 350 °C during 60 min in air atmosphere were the optimal conditions.     

Electronic structure analysis of Mn- and Fe-codoped In2O3 by photoemission yield measurements

The valence band electronic structures of Mn- and/or Fe-doped In₂O₃, i.e., In₂O₃:Mn, In₂O₃:Fe, and In₂O₃:(Mn, Fe), are investigated by photoemission yield measurements. Significant changes are observed in the threshold energy of photoemission, depending on the doped magnetic ions, which indicates that an additional occupied band appears above the top of the valence band of In₂O₃ owing to doping with Mn and/or Fe ions. It is confirmed that the order of the threshold energies of photoemission, E_PET, is E_PET(In₂O₃:Mn)<E_PET(In₂O₃:(Mn, Fe))<E_PET(In₂O₃:Fe)<E_PET(In₂O₃). To gain a better understanding of these results, first-principles molecular orbital calculations are also carried out, which successfully explain the observed changes in the photoemission threshold energies.     

The structure and photocatalytic activity of TiO2 thin films deposited by dc magnetron sputtering

This paper seeks to determine the optimal settings for the deposition parameters, for TiO₂ thin film, prepared on non-alkali glass substrates, by direct current (dc) sputtering, using a ceramic TiO₂ target in an argon gas environment. An orthogonal array, the signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. Using the Taguchi method for design of a robust experiment, the interactions between factors are also investigated. The main deposition parameters, such as dc power (W), sputtering pressure (Pa), substrate temperature (°C) and deposition time (min), were optimized, with reference to the structure and photocatalytic characteristics of TiO₂. The results of this study show that substrate temperature and deposition time have the most significant effect on photocatalytic performance. For the optimal combination of deposition parameters, the (1 1 0) and (2 0 0) peaks of the rutile structure and the (2 0 0) peak of the anatase structure were observed, at 2θ ∼ 27.4°, 39.2° and 48°, respectively. The experimental results illustrate that the Taguchi method allowed a suitable solution to the problem, with the minimum number of trials, compared to a full factorial design. The adhesion of the coatings was also measured and evaluated, via a scratch test. Superior wear behavior was observed, for the TiO₂ film, because of the increased strength of the interface of micro-blasted tools.     

Influence of charged particle bombardment and sputtering parameters on the properties of HfO2 films prepared by dc reactive magnetron sputtering

HfO₂ films prepared on glass substrates by dc reactive magnetron sputtering in an Ar + O₂ atmosphere are investigated. The films are polycrystallized with a pure monoclinic phase, and the crystallization strongly relates to the technology environment. Charged particle bombardment mainly caused by negative oxygen ions during sputtering on the films results in rougher surface morphology and worse crystalline property. Influence of sputtering pressure, substrate temperature and Ar:O₂ flow ratio is studied. The main orientations of the films are (−1 1 1) and (1 1 1). The (−1 1 1) orientation is stable, but (1 1 1) orientation is very sensitive to the sputtering condition, and it can be suppressed effectively by introducing charged particle bombardment, lowing sputtering pressure and increasing oxygen concentration.     

Synthesis and performance of core-shell structured ZnO/In2O3 composites in situ growth

Core-shell structured ZnO/In₂O₃ composites were successfully synthesized via situ growth method. Phase structure, morphology, microstructure and property of the products were investigated by X-ray diffraction (XRD), TG-DTA, field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), transmission electron microscope (TEM) and photoluminescence (PL). Results show that the core-shell structures consist of spindle-like ZnO with about 800 nm in length and 200 nm in diameter, and In₂O₃ particles with a diameter of 50 nm coated on the surface of ZnO uniformly. HMTA plays an important role in the formation of core-shell structures and the addition of In₂O₃ has a great effect on PL spectrum. Possible mechanism for the formation of core-shell structures is also proposed in this paper.     

High temperature ferromagnetism of the vacuum-annealed (In1−xFex)2O3 powders

(In_1−xFe_x)₂O₃ (x = 0.02, 0.05, 0.2) powders were prepared by a solid state reaction method and a vacuum annealing process. A systematic study was done on the structural and magnetic properties of (In_1−xFe_x)₂O₃ powders as a function of Fe concentration and annealing temperature. The X-ray diffraction and high-resolution transmission electron microscopy results confirmed that there were not any Fe or Fe oxide secondary phases in vacuum-annealed (In_1−xFe_x)₂O₃ samples and the Fe element was incorporated into the indium oxide lattice by substituting the position of indium atoms. The X-ray photoelectron spectroscopy revealed that both Fe²⁺ and Fe³⁺ ions existed in the samples. Magnetic measurements indicated that all samples were ferromagnetic with the magnetic moment of 0.49-1.73 μ_B/Fe and the Curie temperature around 783 K. The appearance of ferromagnetism was attributed to the ferromagnetic coupling of Fe²⁺ and Fe³⁺ ions via an electron trapped in a bridging oxygen vacancy.     

Cu掺杂Ga2O3薄膜的光学性能

采用射频磁控溅射和N₂气氛退火处理制备了多晶Ga₂O₃薄膜和Cu掺杂Ga₂O₃薄膜.用X射线衍射仪、紫外-可见分光光度计、荧光光谱仪对Ga₂O₃薄膜和Cu掺杂Ga₂O₃薄膜的结构和光学性能进行了表征.结果表明,Cu掺杂后Ga₂O₃薄膜的结晶质量变差,透过率明显降低,吸收率增加,光学带隙减小.本征Ga₂O₃薄膜在紫外、蓝光和绿光出现了发光带,Cu掺杂后紫外和蓝光发射增强,且在475 nm 处出现了一个新的发光峰.