Influence of growth temperature on the optical and structural properties of ultrathin ZnO films

This study investigates the effect of growth temperature on the optical and structural properties of ultrathin ZnO films on the polished Si substrate. Thickness of the ultrathin ZnO films deposited by atomic layer deposition (ALD) method was about 10 nm. Photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques were used to measure the properties of ultrathin ZnO films. Experimental results showed that the ultrathin ZnO film deposited at 200 °C had excellent ultraviolet emission intensity, and the average roughness of the film surface was about 0.26 nm.     

Microstructure and electrical properties of thin films of ReSi1.75 produced by co-sputtering

Microstructural evolution and changes in electrical resistivity of ReSi_1.75 thin films produced by co-sputtering has been investigated as a function of annealing temperature. Crystallization of amorphous ReSi_1.75 thin films occurs at 600 °C without forming any metastable phases. The crystallization temperature for ReSi_1.75 is considerably higher than those observed for other transition-metal disilicides. The crystal structure as well as the domain (twinned) structure observed for crystallites in ReSi_1.75 thin films annealed above 600 °C are essentially the same as those observed in bulk crystals of ReSi_1.75. Although the grain size of crystallites increases with the increase in annealing temperature, thin films annealed below 650 °C exhibit a nano-crystalline structure. Thin films of amorphous and crystalline ReSi_1.75 and bulk polycrystalline ReSi_1.75 all exhibit electrical resistivity values decreasing with the increase in temperature, indicating the semiconducting nature. Values of electrical resistivity for crystallized thin films are systematically higher than those for amorphous ReSi_1.75 thin films and bulk polycrystalline ReSi_1.75 and increase with the decrease in annealing temperature, exhibiting a peak at just above the crystallization temperature. The high values of electrical resistivity around the crystallization temperature are discussed in terms of the formation of the nano-crystalline structure in thin films, for which the effective medium approximation is not valid.     

电化学沉积Nd掺杂ZnO薄膜的结构和光学性质的研究

用电化学沉积方法制备出了Nd掺杂的ZnO薄膜,并研究其结构和光学性质。X-射线衍射谱的结果表明Nd3 替代Zn2 进入到ZnO晶格中,并没有引起杂相的出现。吸收谱的分析表明,随着掺杂浓度的增大,吸收峰向短波长方向移动 ,即发生蓝移。光致发光谱的结果表明随着Nd3 掺杂浓度的增大,紫外峰强度减小,可见光部分强度增大了。     

Grain size effect on structural, electrical and mechanical properties of NiTi thin films deposited by magnetron co-sputtering

In the present study NiTi films have been deposited on Si (100) substrates by dc magnetron co-sputtering in the temperature range from room temperature to 923 K. The crystallization, surface morphology and structural features were studied using X-ray diffraction (XRD), atomic force microscope (AFM), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). In situ hot stage atomic force microscope was used to investigate the micro-structural changes during phase transformation in these films. Substrate temperature was found to have a great impact on the structural features and phase transformation behavior of NiTi films. The grain size and the crystallization extent increase with the increase in substrate temperature. Nanoindentation tests of these films were conducted at room temperature. Low hardness and depth recovery ratio was observed in case of the film deposited at substrate temperature of 923 K that could be due to the dominance of martensite phase at room temperature which results in more plastic deformation. The electrical properties of the films were studied using four probe resistivity method. Electrical resistance versus temperature plots show that grain size of NiTi films plays an important role in their electrical properties. NiTi based shape memory alloys exhibit a very interesting martensite to austenite phase transformation as crystal structure changes from monoclinic to cubic upon heating close to room temperature. The characteristics of this transformation are of immense technological importance due to a variety of MEMS applications.     

Effect of annealing treatment onoptical and electrical properties of ZnO films

The ZnO-Al films were prepared by R. F. magnetron sputtering system using a Zn-Al target (with purity of 99.99 %). The obtained films were characterized by X-ray diffraction, SEM and optical and electrical measurements. The experimental results show that the properties of ZnO films can be further improved by annealing treatment. The crystallinity of ZnO films becomes better, and the optical gap energy is decreased, but thermoelectric power is enhanced after heat treatment. The optical gap energy decreases from 3.75 eV to 3.68 eV when the annealing temperature increases from 25℃ to 400℃. This can be ascribed to the decrease of carrier concentration, resulting in Burstein shift.     

Effects of heat treatment on morphological, optical and electrical properties of ITO films by sol-gel technique

Indium-tin-oxide（ITO） films were prepared on the quarts glass by sol-gel technique. Effects of different heat treatment temperatures and cooling methods on the morphological, optical and electrical properties of ITO films were measured by TG/DTA, IR, XRD, SEM, UV-VIS spectrometer and four-probe apparatus. It is found that the crystallized ITO films exhibit a polycrystalline cubic bixbyite structure. The heat treatment process has significant effects on the morphological, optical and electrical properties of ITO films. Elevating the heat treatment temperature can perfect the crystallization process of ITO films, therefore the optical and electrical properties of ITO films are improved. But the further increasing of heat treatment temperature results in the increment of ITO films＇ resistivity. Compared with ITO films elaborated by furnace cooling, those prepared through air cooling have following characteristics as obviously decreased crystalline size, deeply declined porosity, more compact micro-morphology, improved electrical property and slightly decreased optical transmission.     

Filtered vacuum arc deposition of undoped and doped ZnO thin films: Electrical, optical, and structural properties

Filtered vacuum (cathodic) arc deposition (FVAD, FCVD) of metallic and ceramic thin films at low substrate temperature (50-400 °C) is realized by magnetically directing vacuum arc produced, highly ionized, and energetic plasma beam onto substrates, obtaining high quality coatings at high deposition rates. The plasma beam is magnetically filtered to remove macroparticles that are also produced by the arc. The deposited films are usually characterized by their good optical quality and high adhesion to the substrate. Transparent and electrically conducting (TCO) thin films of ZnO, SnO₂, In₂O₃:Sn (ITO), ZnO:Al (AZO), ZnO:Ga, ZnO:Sb, ZnO:Mg and several types of zinc-stannate oxides (ZnSnO₃, Zn₂SnO₄), which could be used in solar cells, optoelectronic devices, and as gas sensors, have been successfully deposited by FVAD using pure or alloyed zinc cathodes. The oxides are obtained by operating the system with oxygen background at low pressure. Post-deposition treatment has also been applied to improve the properties of TCO films.The deposition rate of FVAD ZnO and ZnO:M thin films, where M is a doping or alloying metal, is in the range of 0.2-15 nm/s. The films are generally nonstoichiometric, polycrystalline n-type semiconductors. In most cases, ZnO films have a wurtzite structure. FVAD of p-type ZnO has also been achieved by Sb doping. The electrical conductivity of as-deposited n-type thin ZnO film is in the range 0.2-6 × 10^− 5 Ω m, carrier electron density is 10²³-2 × 10²⁶ m^− 3, and electron mobility is in the range 10-40 cm²/V s, depending on the deposition parameters: arc current, oxygen pressure, substrate bias, and substrate temperature. As the energy band gap of FVAD ZnO films is ∼ 3.3 eV and its extinction coefficient (k) in the visible and near-IR range is smaller than 0.02, the optical transmission of 500 nm thick ZnO film is ∼ 0.90.     

Emergence of Ag particles and their effects on the mechanical properties of TaN-Ag nanocomposite thin films

TaN-Ag nanocomposite films were deposited by reactive co-sputtering on tool steel substrates. The films were then annealed using RTA (Rapid Thermal Annealing) at 350 °C for 2, 4, 8 min respectively to induce the nucleation and growth of Ag particles in TaN matrix and on film surface. C-AFM (Conductive Atomic force Microscopy) and FESEM (Field-Emission Scanning Electron Microscopy) were applied to examine the Ag nano-particles emerged on the surface of these thin films. A nano-indenter and a pin-on-disk tribometer were used to study the effect of annealing on the films' mechanical properties. The results reveal that annealing by RTA can cause Ag nano-particles to emerge on the TaN surface. Consequently, the mechanical properties of the films will vary depending on annealing conditions, Ag content, and Ag particle emergence.     

Morphology and optical properties of Co doped ZnO textured thin films

Depending on the ZnO seed-layers, a new kind of cobalt doped zinc oxide (Zn_1−xCo_xO) thin films with controllable morphology were prepared by a facile solvothermal method. A series of ZnO thin films with different Co contents were applied to study the effect of doped Co on morphology, structural and optical properties. It is found that the doped content plays an important role on morphology evolution of Zn_1−xCo_xO films. The results of scanning electron microscope (SEM) indicate that the Zn_1−xCo_xO films are highly uniform and porous. Co has been successfully doped into the ZnO lattice structure and revealed by X-ray diffraction (XRD) and energy dispersive spectrum (EDS). It can be found that Zn_1−xCo_xO thin films possess good crystalline quality through the characterization of transmission electron microscope (TEM) and high-resolution transmission electron microscopy (HRTEM). All of the samples show a stronger violet emission and ultraviolet absorption, and the violet emission peaks shift towards red with increasing of Co content. In addition, the magnetic result demonstrates that the prepared Co-doped ZnO thin films are room-temperature ferromagnetic materials.     

Low-temperature growth and optical properties of ZnO nanorods

Zinc oxide (ZnO) nanorods were grown on ITO conducting glass by the chemical solution deposition method (CBD) in an aqueous solution that contained zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and methenamine (C₆H₁₂N₄). The size of ZnO nanorods increased with molar concentration of zinc nitrate, and the nanorods with different aspect ratios also formed through tuning the reaction time when the molar concentration was 0.1 M. The length of nanorods increased significantly with the reaction time, but the thickness of the film deposited on the substrate only slightly increased. From the X-ray measurement results, it can be seen that the growth orientation of the as-prepared ZnO nanorods was [0 0 2]. Photoluminescence measurements were also carried out, the result showed a blue shift in violet emission with the reduction in crystal size.     

Effect of annealing treatment on the structural, optical, and electrical properties of Al-doped ZnO thin films

Highly conductive and transparent Al-doped ZnO (AZO) thin films were prepared from a zinc target containing Al (1.5 wt.%) by direct current (DC) and radio frequency (RF) reactive magnetron sputtering. The structural, optical, and electrical properties of AZO films as-deposited and submitted to annealing treatment (at 300 and 400 ℃, respectively) were characterized using various techniques. The experimental results show that the properties of AZO thin films can be further improved by annealing treatment. The crystallinity of ZnO films improves after annealing treatment. The transmittances of the AZO thin films prepared by DC and RF reactive magnetron sputtering are up to 80% and 85% in the visible region, respectively. The electrical resistivity of AZO thin films prepared by DC reactive magnetron sputtering can be as low as tering have better structural and optical properties than that prepared by DC reactive magnetron sputtering.     

溅射气压对ZnO透明导电薄膜光电性能的影响

采用射频磁控溅射方法,在普通玻璃上制备了具有高度c轴取向的ZnO薄膜,研究了溅射气压(0.2～1.5 Pa)对ZnO薄膜的微观结构和光电性能的影响.AFM、XRD、UV-Vis分光光度计及四探针法研究表明:随着溅射气压的增大,ZnO薄膜沿c轴方向的结晶质量提高,晶粒细化,薄膜表面更加致密,晶粒大小更加均匀;ZnO薄膜在400～900nm范围内的平均透过率均高于85%,其中在0.5～1.5 Pa范围内其透过率高于90%;样品在高纯氮气气氛中经350 ℃,300 s退火后,电阻率最低达到10-2 Ω-cm量级.     

Structural, optical and magnetic properties of Eu-doped ZnO films

Polycrystalline Zn_1−xEu_xO (x = 0, 0.02, 0.05) films were deposited on silicon (1 0 0) substrates by radio-frequency magnetron sputtering. The structural, optical and magnetic properties of the films were investigated. The results from both the X-ray diffraction and photoluminescence spectra reveal that Eu³⁺ ions successfully substitute for Zn²⁺ ions in the ZnO lattice. The magnetic field and temperature dependence of magnetization curves demonstrate that the Zn_0.95Eu_0.05O films are ferromagnetic at room temperature. No impurity phase was found in Eu-doped films with X-ray diffraction, Raman spectroscopy and zero-field-cooled measurements. The ferromagnetism is attributed to the intrinsic property of Eu-doped ZnO films and could be interpreted by the bound-magnetic-polaron model.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

Effects of Mg substitution on the structural, optical, and electrical properties of CuAlO2 thin films

Mg-doped CuAlO₂ thin films are prepared by the chemical solution method. The XRD results show that the solid solubility of Mg species on Al sites in CuAlO₂ lattice is lower than 2 at.%. When less than 2 at.% of Mg is added to the CuAlO₂ film, the surface roughness of the films was reduced with Mg substitution. Moreover, the c-axis orientation of the films improves because the in-plane fusion between CuAlO₂ crystallites is hindered. Optical and electrical measurements show that substituting Al³⁺ in the films with Mg²⁺ increases both their transmittance in the visible region and their optical band gaps. As well, their electrical conductivity is enhanced. At 300 K, the conductivity of the 1 at.% Mg-doped sample is up to 5.2 × 10⁻³ S/cm. Thus, Mg-doped CuAlO₂ films may have potential applications as transparent conductive oxides.     

Structural,optical and electrical characterization of chemically deposited CdSe thin films

Cadmium selenide (CdSe) thin films have been deposited on glass substrate. CdSe thin films were characterized by various techniques such as X-ray diffraction, scanning electron microscopy and UV–vis–NIR double beam spectrophotometer. The electrical and thermo-electrical properties are also studied. The X-ray diffraction analysis shows that the film samples are in cubic crystal structure. The optical band gap energy (Eg) was found to be 1.7 eV.     

Studies of photovoltaic properties of nanocrystalline thin films of CdS-CdTe

Nanocrystals of CdS and CdTe were synthesized by aqueous chemical route. From the optical absorption spectra the particle sizes (diameter) were estimated to be around 7 and 4 nm for CdS and CdTe, respectively. The photovoltaic device was fabricated using these nanocrystalline materials on an indium tin oxide (ITO) coated glass substrate using a spin coating method. From the room temperature photoluminescence study a drastic quenching of photoluminescence the CdS-CdTe thin film was observed. Light intensity dependent current-voltage measurements of CdS-CdTe thin film shows photovoltaic effect; with increase in light intensity the current density increases, however, the open circuit voltage does not show any change. The low efficiency of the device has been explained on the basis of the defects and diffusion of Te ions into CdS.     

退火处理对ITO和ITO:Zr薄膜性能的影响

利用磁控溅射在室温条件下沉积ITO薄膜和ITO：Zr薄膜,对比研究在空气中退火处理对ITO和ITO：Zr薄膜性能的影响。结果表明,Zr的掺杂促进了（400）晶面的取向,随着退火温度的升高,薄膜表面颗粒增大,表面粗糙度有所降低。室温下Zr的掺杂显著改善了薄膜的光电性能,随着退火温度的升高,ITO和ITO：Zr薄膜的方阻都表现为先降后升的趋势,ITO：Zr薄膜在较低的退火温度下可见光透过率就可达到80%以上,直接跃迁模型确定的光学禁带宽度Eg呈现了先升后降的变化。ITO：Zr薄膜比ITO薄膜显示了更高的效益指数,揭示了ITO：Zr薄膜具有更好的光电性能。     

Evolution of structural, surfacial and mechanical properties of titanium-nickel-copper thin films during rapid thermal annealing

The structural, surfacial and nanoscale mechanical properties evolution of Ti-Ni-Cu thin films, prepared by the co-sputtering of TiNi and Cu targets during rapid thermal annealing (RTA) were investigated. Crystallization took place in a few seconds at 480 °C. With increasing annealing time (up to 180 s), roughness increased dramatically, and was far more prominent than in films crystallized by conventional thermal annealing (CTA). Although RTA is energy efficient due to the lower annealing time, the film roughness is less ideal than CTA, which may prove limiting in specific applications. The surface and subsurface chemical states of Ti, Ni and Cu was similar for RTA and CTA processed materials, demonstrating they are exposed to comparable redox potentials during annealing. Using X-ray absorption spectroscopy (XAS), it was found that the RTA (180 s) and CTA (1 h) films possessed longer range order. The evolution of nanoscale mechanical properties of the RTA films during rapid thermal annealing was also studied.     

CuS-based thin films for architectural glazing applications produced by co-evaporation: Morphology, optical and electrical properties

Copper sulphide thin films in the 90–300 nm thickness range have been deposited on soda–lime glass substrates by thermal co-evaporation of Cu and S. Depending on the film thickness, the optical transmittance in the visible region is of about 50% for the thinnest film and 19% for the thickest film, with the corresponding near-infrared transmittance dropping from 11% to near-zero at 2500 nm as the film thickness increases from 90 to 300 nm. A resistivity of ρ ~ 10^− 4 Ω cm has been obtained for the films. The optoelectronic properties of the films remained practically unchanged after one year stored under laboratory ambient. The optical properties obtained for selected CuS-based films make them suitable for their use as effective solar control glazings in warm climates.