The influence of annealing temperature on the structural, electrical and optical properties of ion beam sputtered CuInSe2 thin films

CuInSe₂ (CIS) thin films were prepared by ion beam sputtering deposition of copper layer, indium layer and selenium layer on BK7 glass substrates followed by annealing at different temperatures for 1 h in the same vacuum chamber. The influence of annealing temperature (100-400 °C) on the structural, optical and electrical properties of CIS thin films was investigated. X-ray diffraction (XRD) analysis revealed that CIS thin films exhibit chalcopyrite phase and preferential (112) orientation when the annealing temperature is over 300 °C. Both XRD and Raman show that the crystalline quality of CIS thin film and the grain size increase with increasing annealing temperature. The reduction of the stoichiometry deviation during the deposition of CIS thin films is achieved and the elemental composition of Cu, In and Se in the sample annealed at 400 °C is very near to the stoichiometric ratio of 1:1:2. This sample also has an optical energy band gap of about 1.05 eV, a high absorption coefficient of 10⁵ cm⁻¹ and a resistivity of about 0.01 Ω cm.     

F-doped SnO2 thin films grown on flexible substrates at low temperatures by pulsed laser deposition

Fluorine-doped tin oxide (SnO₂:F) films were deposited on polyethersulfone plastic substrates by pulsed laser deposition. The electrical and optical properties of the SnO₂:F films were investigated as a function of deposition conditions such as substrate temperature and oxygen partial pressure during deposition. High quality SnO₂:F films were achieved under an optimum oxygen pressure range (7.4-8 Pa) at relatively low growth temperatures (25-150 °C). As-deposited films exhibited low electrical resistivities of 1-7 mΩ-cm, high optical transmittance of 80-90% in the visible range, and optical band-gap energies of 3.87-3.96 eV. Atomic force microscopy measurements revealed a reduced root mean square surface roughness of the SnO₂:F films compared to that of the bare substrates indicating planarization of the underlying substrate.     

Effects of oxygen concentration on the properties of sputtered SnO2:Sb films deposited at low temperature

Antimony doped tin oxide (SnO₂:Sb) films have been prepared by d.c. magnetron sputtering and the properties of the films depend on deposition conditions, such as O₂ gas ratio, were investigated. The gas composition was found to affect the properties of the films. With the incorporation additional oxygen, the electrical and optical properties of films significantly improved. The minimum value of resistivity of the films was 4.9 × 10^− 3 Ω cm at the oxygen concentration of 30% and the optical transmittance was over 80%.     

Blue shift of optical band-gap in LiNbO3 thin films deposited by sol-gel technique

Lithium niobate (LN) thin films were deposited on quartz substrates by sol-gel technique. The measured absorption and photoluminescence spectra show that the band structure of LN thin films is direct unlike indirect band-gap in bulk LN and the optical band-gap of these LN thin films was measured to be 4.7 eV which is ~ 1 eV greater than that for stoichiometric bulk LN. The dependence of the blue shift of band-gap on several parameters like quantum confinement, composition (Li:Nb ratios of LN thin films) and strain was also investigated. The results obtained show that the large blue shift in band-gap of LN thin films is primarily due to strain in the film.     

P-type transparent Ti-V oxides semiconductor thin film as a prospective material for transparent electronics

In this paper electrical and optical properties of mixed titanium and vanadium oxides (Ti-V oxides) thin films have been outlined. Thin films were deposited by sputtering of mosaic Ti-V target in reactive oxygen plasma using high energy magnetron sputtering process. From elemental analysis results, 19 at.% of vanadium was incorporated into thin films and X-ray diffraction investigations displayed their amorphous behavior. However, images obtained by the use of an atomic force microscope displayed a densely packed nanocrystalline structure. It has been found that V addition considerably improves the electrical conduction of prepared Ti-V oxide thin films as compared to undoped TiO₂ and results in p-type electrical conduction. Resistivity of Ti-V oxides thin films was found at the order of 10⁵ Ω cm. Optical measurements have shown the average transmission coefficient of about 73% in the visible spectral range and that the position of fundamental absorption edge has been shifted by 40 nm towards the longer wavelength as compared to the undoped TiO₂. The results testified that the prepared Ti-V oxides thin films might be considered as a p-type transparent oxide semiconductors for future application in transparent electronics.     

Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films

We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other.     

Effect of deposition temperature on the properties of sputtered YIG films grown on quartz

Yttrium Iron Garnet (YIG), Y₃Fe₅O₁₂, is an oxide material that has potential applications in the magneto-optical recording media and microwave device industries. These materials, when synthesized in thin film form, usually require post-deposition annealing in order to enhance their physical properties. Furthermore, integration of YIG based optical components requires the synthesis of high quality YIG material on quartz, a process that may be problematic due to poor adhesion and lattice mismatch. Thus, we have conducted a study on the effect of deposition temperature (from 25 to 800 °C) and post-deposition annealing (at 740 °C) on the crystalline quality and chemical composition of YIG thin films, grown by radio-frequency magnetron sputtering, on quartz substrates. X-ray diffraction (XRD) shows that as-grown layers are amorphous, and subsequent annealing is necessary to induce film crystallization. Rutherford backscattering spectrometry analyses were also conducted and the chemical composition of the films was found to depend on initial deposition temperature and is affected by post-deposition anneals. Comparison of the XRD and RBS results point out to the existence of an optimal deposition temperature at about 700 °C for the formation of high crystalline quality and stoichiometric YIG thin films. Magnetic measurements were found to correlate to the XRD and RBS analyses.     

Growth and characterization of indium tin oxide thin films deposited on PET substrates

Transparent and conductive indium tin oxide (ITO) thin films were deposited onto polyethylene terephthalate (PET) by d.c. magnetron sputtering as the front and back electrical contact for applications in flexible displays and optoelectronic devices. In addition, ITO powder was used for sputter target in order to reduce the cost and time of the film formation processes. As the sputtering power and pressure increased, the electrical conductivity of ITO films decreased. The films were increasingly dark gray colored as the sputtering power increased, resulting in the loss of transmittance of the films. When the pressure during deposition was higher, however, the optical transmittance improved at visible region of light. ITO films deposited onto PET have shown similar optical transmittance and electrical resistivity, in comparison with films onto glass substrate. High quality films with resistivity as low as 2.5 × 10^− 3 Ω cm and transmittance over 80% have been obtained on to PET substrate by suitably controlling the deposition parameters.     

Influence of rapid thermal annealing on surface texture-etched Al-doped ZnO films prepared by various magnetron sputtering methods

The influence of rapid thermal annealing (RTA) on surface texture formation as well as the light management obtainable by wet-chemically etching was investigated for transparent conducting Al-doped ZnO (AZO) thin films prepared by various types of magnetron sputtering deposition (MSD) with an oxide target. Texture-etched AZO films prepared by an r.f. (13.56 MHz) power-superimposed d.c. magnetron sputtering deposition (rf + dc-MSD) exhibited a higher haze value than found in equivalent films prepared by d.c. MSD. The order that the RTA treatment and the etching were conducted considerably affected the obtainable surface texture. Conducting the etching after a heat treatment with RTA in air resulted in larger etch pits as well as higher haze values than were obtained in AZO films that were etched before the RTA. A high haze value generally above 70% in the range from visible to near infrared (at wavelengths up to 1200 nm) was obtained in texture-etched AZO thin films that were prepared by rf + dc-MSD and etched after RTA at a temperature of 500 °C for 3 min.     

Structural and mechanical properties of titanium oxide thin films for biomedical application

Titanium oxide thin films were deposited by radiofrequency reactive sputtering in Ar-O₂ atmosphere on silicon (100) wafers and titanium alloy plates (Ti-6Al-4V). Thin films structural characterization was carried out by grazing incidence X-ray diffraction, atomic force microscopy, scanning and transmission electron microscopies. Chemical composition was checked by X-ray wavelength dispersive spectroscopy. Mechanical assessment was achieved by nano-indentation and nano-scratch measurements. The films deposited on silicon substrates are over-stoechiometric in oxygen, with an oxygen to titanium ratio of about 2.2. The growth of anatase and rutile phases was promoted by ranging the total and oxygen partial pressures between 0.17-1.47 Pa and 35-85%. The growth rate of films, determined by grazing incidence X-ray reflectivity, was ranging from 35 to 55 nm/h. The rutile single-phased films possess a hardness of about 2.5 times higher and a lower friction coefficient than the anatase films. The films which contain anatase possess a high surface root-mean-square roughness and a reduced elastic modulus of around 120 GPa close to reduced elastic moduli of hydroxyapatite bioceramic and titanium alloy. So the anatase film could be the best candidate as a titanium oxide intermediate layer between hydroxyapatite and titanium alloy in the field of biomedical implants.     

Spectroscopic ellipsometry and positron annihilation investigation of sputtered HfO2 films

Hafnium oxide (HfO₂) films were prepared using a pulsed sputtering method and different O₂/(O₂ + Ar) ratios, deposition pressures, and sputtering powers. Spectroscopic ellipsometry (SE) and positron annihilation spectroscopy (PAS) were used to investigate the influence of the deposition parameters on the number of open volume defects (OVDs) in the HfO₂ films. The results reveal that a low O₂/(O₂ + Ar) ratio is critical for obtaining films with a dense structure and low OVDs. The film density increased and OVDs decreased when the deposition pressure was increased. The film deposited at high sputtering power showed a denser structure and lower OVDs. Our results suggest that SE and PAS are effective techniques for studying the optical properties of and defects in HfO₂ and provide an insight into the fabrication of high-quality HfO₂ thin films for optical applications.     

Microstructure and optical properties of photoactive TiO2:N thin films

In this work, we have chosen oxidation of TiN thin films as a feasible method for preparation of nitrogen-doped titanium dioxide thin films, TiO₂:N, for photocatalytic applications. DC reactive magnetron sputtering with the plasma emission control was used for deposition of stoichiometric TiN thin films. The microstructure and chemical composition of films before and after oxidation were investigated by means of RBS, X-ray diffraction (XRD) in grazing incidence diffraction (GID) configuration, AFM and XPS techniques. The electrical conductivity was measured by the van der Pauw method as a function of the oxidation temperature. The optical transmittance and reflectance spectra of the films were measured over the visible and UV ranges of the light spectrum. GID diffraction patterns of as-sputtered TiN thin films and those after oxidation indicate that TiO₂ rutile is formed at around 300 °C. Nitrogen is still present as indicated by XPS studies even when XRD detects the rutile only. Optical absorption of thin films oxidized at 450 °C is shifted towards the visible range of the light spectrum.     

The effects of the doping elements on the optical properties of silver-based alloy layers for storage media usage

The effects of doping with copper and titanium on the optical properties of a silver alloy layer for storage media usage were investigated in this study. Doped silver alloy thin films were deposited using specially prepared targets and direct current (DC) sputtering. The results show that copper content ranging from 0.5 wt.% (AC0.5) to 1.5 wt.% (AC1.5) enhances the uniformity of thin film and reduces its grain size. For environmental stability, titanium was introduced, although this dopant will decrease the reflectivity of the silver-based alloy thin films. The silver alloy thin films with 1 wt.% titanium (ACT1) have good corrosion-resistant behavior. Films with 3 wt.% titanium (ACT3) are difficult to manufacture since the uniformity of the mechanical properties is poor and the grain size is coarser.     

Preparation and characterisation of tin-doped indium oxide films

Tin-doped In₂O₃ (ITO) thin films were prepared by reactive evaporation from new pulverulent mixture of indium oxide, tin oxide and metallic indium at different partial pressures of oxygen. The films were annealed in a secondary vacuum just after deposition. Under optimal conditions of evaporation, these films are stoichiometric, show a good crystallinity and feature high transmission in visible region (T>90%) and high reflection in near IR region versus oxygen pressure.     

A ZnO/PET assembly study: Optimization and investigation of the interface region

Zinc oxide thin films are deposited on polyethylene terephthalate (PET) by r.f. magnetron sputtering process from a ceramic target in oxygen–argon plasmas. Structural studies show that the thin films are highly oriented along the (0 0 2) direction of the würtzite phase when the oxygen partial pressure is lower than 0.2 Pa. The crystallinity is accentuated when the oxygen partial pressure of the sputtering gas is increased from 0 to 0.02 Pa. The composition of the films determined by Rutherford backscattering spectrometry (RBS) varies in a wide range and it is necessary to add a few amount of oxygen in the plasma composition to establish the stoichiometry. The oxygen partial pressure is found to influence also the microstructure and consequently the density of the coatings.Various cold plasmas are used to treat the polymer surface before the deposition of zinc oxide films. Wettability measurements show an increase in the polar component of the PET surface free energy whatever the nature of the plasma used for the treatment. This increase is more obvious with the carbon dioxide plasma. XPS examinations of the CO₂ plasma treated PET surface in optimized conditions show a functionalisation of the polymer surface. The carbon dioxide plasma treatments of PET surface are found to enhance the peeling energy. The adhesion level depends also on the sputtering parameters, mainly the oxygen partial pressure and the r.f. power which influence the coating properties. The zinc oxide/PET interface is studied by XPS at the different stages of deposition and at various take-off angles. AFM observations show a regular growth of zinc oxide layers with smooth topographies on PET films. The different findings obtained from C1s, O1s, Zn2p3/2, Zn3p peaks and Auger Zn L₃M_4.5M_4.5 peak are corroborated and discussed. New chemical bonds between the polymer and the further coming zinc oxide thin layer are evidenced.     

Large-distance rf- and dc-sputtering of epitaxial La1 − xSrxMnO3 thin films

Studies on large-distance sputtering as an effective alternative to molecular beam epitaxy, pulsed laser deposition or off-axis sputtering for the deposition of epitaxial La_1 − xSr_xMnO₃ (LSMO) thin films, are reported. The focus of this study is on the quality of the samples and their structural and magnetic properties. The dependence of the characteristics of the LSMO films on the sputtering mode (rf, dc) and the sputtering parameters, in particular on the oxygen partial pressure is established and discussed. It is shown that large-distance sputtering can provide high quality LSMO thin films without the need for post-annealing.     

Influence of the plasma expansion dynamics on the structural properties of pulsed laser ablation deposited tin oxide thin films

Tin oxide thin films were deposited by pulsed laser ablation at different oxygen partial pressures and substrate temperatures. Information on the structural and morphological properties of the deposited thin films has been obtained by means of X-ray photoelectron, Fourier transform infrared absorption spectroscopies and scanning electron microscopy. The expansion of the laser generated plasma has been studied by means of time resolved fast photography. Different expansion regimes were observed: in vacuum the plasma follows a free expansion one while the raise of the background oxygen pressure leads to the development of a shock wave. It was found that only at 13.3 Pa of oxygen gas, in the presence of a shock wave, the deposition of stoichiometric films, at relatively low substrates temperature, is attainable. The correlation between the observed dynamics of the plasma expansion and the structural properties of the deposited films is presented and discussed.     

Effect of aluminum and indium co-doping on zinc oxide films prepared by dc magnetron sputtering

Aluminum and indium co-doped zinc oxide (AIZO) thin films were prepared by direct current (dc) magnetron sputtering on glass substrate in pure argon atmosphere. Three inches of zinc oxide ceramic with 0.5 wt.% of aluminum and indium doping was used as a target in static mode. The influence of sputtering conditions i.e. substrate-target distance, pressure and power on AIZO films was studied. The electrical resistivity and microstructure of thin films were investigated by the four point probe technique and the scanning electron microscope, respectively. The optical transmittance of AIZO films was measured by UV visible spectrophotometer in the wavelength of 300-1100 nm. Depending on the deposited conditions, highly transparent films up to 80% with low resistivities in the range of 2.6-7.9 × 10^− 4 Ω cm were achieved at room temperature. Possible mechanism in the processing which, ultimately, determines the physical properties of AIZO films will be discussed.     

Property variations of direct-current reactive magnetron sputtered copper oxide thin films deposited at different oxygen partial pressures

Cuprous oxide (Cu₂O) and cupric oxide (CuO) thin films were deposited on glass substrates at different oxygen partial pressures by direct-current reactive magnetron sputtering of pure copper target in a mixture of argon and oxygen gases. Oxygen partial pressure was found to be a crucial parameter in controlling the phases and, thus, the physical properties of the deposited copper oxide thin films. Single-phase Cu₂O thin films with cubic structure were obtained at low oxygen partial pressure between 0.147 Pa and 0.200 Pa while higher oxygen partial pressure promoted the formation of CuO thin films with base-centered monoclinic structure. Polycrystalline Cu₂O thin films deposited with oxygen partial pressure at 0.147 Pa possessed the lowest p-type resistivity of 1.76 Ω cm as well as an optical band gap of 2.01 eV. On the other hand, polycrystalline CuO thin films deposited with oxygen partial pressure at 0.320 Pa were also single phase but showed a n-type resistivity of 0.19 Ω cm along with an optical band gap of 1.58 eV.     

SnO2-x薄膜非化学计量比对气敏性能的影响

采用反应磁控溅射法制备SnO2薄膜经常出现化学计量比的失衡问题。通过控制溅射过程中的氧分压制备不同化学计量比的SnO2-x薄膜,研究非化学计量比对薄膜结构、成分以及气敏性能的影响。XRD结果表明氧分压对材料结构和取向的影响非常显著。薄膜的O／Sn和表面化学成分通过XPS进行确定,分析发现氧分压的增加促使薄膜接近化学计量比,但表面化学吸附氧含量在0．33Pa氧分压下达到最大。气敏性能测试表明,非化学计量比主要影响薄膜表面的化学吸附氧数量,从而影响导电性和气体敏感性。氧分压对薄膜化学吸附氧的影响趋势与对气敏性能的影响趋势一致。0．33Pa氧分压下制备的薄膜拥有最多的表面吸附氧,同时对氢气的灵敏度高达45．6％。另外,在0．2～0．5Pa氧分压下制备的薄膜对氢气具有较好的选择性。