Influence of ion-beam sputtering deposition parameters on highly photosensitive and transparent CdZnO thin films

CdZnO thin films with a nominal thickness of ~200 nm were grown on c-plane sapphire substrates by dual ion-beam sputtering deposition technique. The effect of substrate temperature (300–600 °C) and gas ambience on structural, morphological, compositional and opto-electronic properties was studied. X-ray diffraction patterns confirmed that all the films were polycrystalline in nature and were preferentially oriented along the c-axis. It was revealed that the films grown at Ar/O₂ ratio of 4:1 were structurally more ordered and the film quality was found to be the best at 500 °C. The compositional studies specify that approximately 11.8 at.% of cadmium were present in the film deposited at 300 °C in Ar–O₂ mixture. Investigations on optical properties by photoluminescence and absorption studies indicate band gap shrinkage with the increase in argon partial pressure and substrate temperature. It was found that photosensitivity of the deposited films was highly dependent on growth conditions. The photosensitivity was found to be 5000-fold higher for CdZnO film grown at 600 °C in Ar–O₂ ambience compared to the best reported result, and this was promising to realize high-performance opto-electronic devices on such CdZnO films.     

Optical characterization of ZnO thin films deposited by Sol-gel method

In this paper, ZnO thin film is deposited on Pt/TiO₂/SiO₂/Si substrate using the sol-gel method and the effect of annealing temperature on the structural morphology and optical properties of ZnO thin films is investigated. The ZnO thin films are crystallized by the heat treatment at over 400°C. The ZnO thin film annealed at 600°C exhibits the greatest c-axis orientation and the Full-Width-Half-Maximum (FWHM) of X-ray peak is 0.4360°. A dense ZnO thin film is deposited by the growth of uniform grains with the increase of annealing temperature but when the annealing temperature increases to 700°C, the surface morphology of ZnO thin film becomes worse by the aggregation of ZnO particles. In the results of surface morphology of ZnO thin film using atomic force microscope (AFM), the surface roughness of ZnO thin film annealed at 600°C is smallest, that is, approximately 1.048 nm. For the PL characteristics of ZnO thin film, it is observed that ZnO thin film annealed at 600°C exhibits the greatest UV (ultraviolet) exciton emission at approximately 378 nm, and the smallest visible emission at approximately 510 nm among ZnO thin films annealed at various temperatures. It is deduced that ZnO thin film annealed at 600°C is formed most stoichiometrically, since the visible emission at approximately 510 nm comes from either oxygen vacancies or impurities.     

Crystal orientation dependent microwave dielectric properties of sputtered SBTi thin films on fused silica substrates

Thin films of SBTi (SrBi₄Ti₄O₁₅) were deposited on fused silica substrates by rf-magnetron sputtering at substrate temperatures from 600 to 725 °C. The effect of substrate temperature on preferential orientation, microstructure, Raman scattering characteristics and microwave dielectric properties of SBTi thin films were investigated. Microwave dielectric properties were investigated using the Split Post Dielectric Resonator (SPDR) technique. As the substrate temperature increases, the preferential orientation changes from (119) to (0010). Films deposited at 700 °C exhibits less lattice distortion. It exhibits a dielectric constant about 110 and loss tangent about 0.06 at 10 GHz. It is seen from the Raman analysis that the films deposited at higher temperatures orients more towards c-axis which releases the torsional vibration mode involving TiO6 octahedra with a higher oscillator strength resulting in larger values of dielectric constant and dielectric loss for those films.     

Spray pyrolytic deposition of CuBiS2 thin films

Thin films of CuBiS₂ have been deposited on glass substrates using spray pyrolysis technique. The effect of substrate temperature on the growth of CuBiS₂ thin films is studied in the range of 150 to 400°C. The best quality films are grown at substrate temperature 250°C with 0·1 M composition. Other preparative parameters like spray rate, pressure, height of the solution, etc are optimized with respect to substrate temperature. Some optical and electrical properties of CuBiS₂ films are also studied and reported.     

Optical and hall properties of Al-doped ZnO thin films fabricated by pulsed laser deposition with various substrate temperatures

The 3 wt% Al-doped zinc oxide (AZO) thin films were fabricated on quartz substrates at a fixed oxygen pressure of 200 mTorr with various substrate temperatures (room temp. ～500 °C) by using pulsed laser deposition in order to investigate the microstructure, optical, and electrical properties of AZO thin films. All thin films were shown to be c-axis oriented, exhibiting only a (002) diffraction peak. The AZO thin film, fabricated at 200 mTorr and 400 °C, showed the highest (002) orientation and the full width at half maximum (FWHM) of the (002) diffraction peak was 0.42°. The c-axis lattice constant decreased with increasing substrate temperature. The electrical property indicated that the highest carrier concentration (1.27 × 10²¹ cm^?3) and the lowest resistivity (6.72 × 10^?4 Ωcm) were obtained in the AZO thin film fabricated at 200 mTorr and 400 °C. The optical transmittance in the visible region was higher than 80 %. The Burstein-Moss effect, which shifts to a high photon energy, was observed.     

Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films

ZnO epitaxial thin films were grown on p-type Si(100) substrates by dual ion beam sputtering deposition system. The crystalline quality, surface morphology, optical and electrical properties of as-deposited ZnO thin films at different growth temperatures were studied. Substrate temperature was varied from 100 to 600 °C at constant oxygen percentage O₂/(O₂ + Ar) % of 66.67 % in a mixed gas of Ar and O₂ with constant chamber pressure of 2.75 × 10^?4 mBar. X-Ray diffraction analyses revealed that all the films had (002) preferred orientation. The minimum value of stress was reported to be ?0.32 × 10¹⁰ dyne/cm² from ZnO film grown at 200 °C. Photoluminescence measurements demonstrated sharp near-band-edge emission (NBE) was observed at ~375 nm along with deep level emission (DLE) in the visible spectral range at room temperature. The DLE Peak was found to have decrement as ZnO growth temperature was increased from 200 to 600 °C. The minimum FWHM of the NBE peak of 16.76 nm was achieved at 600 °C growth temperature. X-Ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies point defects in ZnO film grown at 400 °C. The ZnO thin film was found to be highly resistive when grown at 100 °C. The ZnO films were found to be n-type conducting with decreasing resistivity on increasing substrate temperature from 200 to 500 °C and again increased for film grown at 600 °C. Based on these studies a correlation between native point defects, optical and electrical properties has been established.     

Nd:YAG pulsed laser deposition of AlVO4 thin films on alumina and monocrystalline MgO

AlVO₄ thin films were prepared by infrared Nd:YAG pulsed laser deposition on two different substrates (polycrystalline Al₂O₃ and monocrystalline MgO). The distance between the target-substrate (30 mm) and the partial oxygen pressure (0.14 mbar) during the deposition process were chosen taking into account the previous experiences with other oxides. The substrate temperature was varied between 300 and 600 °C finding an optimum at about 400 °C. At higher temperatures, the vanadium seems to evaporate from substrate surface with a strong change of stoichiometry. Preferential growth of AlVO₄ films in the direction (022), were grown on MgO substrates. A very high sensitivity of these films to a flux of NO₂ gas is also shown.     

Synthesis of LaCrO3 films using spray pyrolysis technique

LaCrO₃ thin films on electrolyte yttria-stabilized zirconia (YSZ) substrates were prepared by spray pyrolysis technique in the temperature range of 600–750 °C using lanthanum and chromium nitrates as precursors. Thin films obtained at 600–650 °C appear to be a mixture of cubic La(OH)CrO₄ and cubic LaCrO₄ phases, which transforms to pure cubic LaCrO₄ with the substrate temperature increasing to 700–750 °C. After being annealed at 900 °C for 2 h, all films convert to a single cubic LaCrO₃ phase. The change of Cr2p spectra in X-ray photoelectron spectroscopy (XPS) analysis shows the similar phase transformation process. Reaction processes with respect to the substrate temperature were proposed according to X-ray diffraction (XRD) and XPS analysis. The surface morphology of the films was found to depend strongly on the substrate temperature, which would be the deciding factor of the film growth mechanisms.     

Doping Effect on the Structure of Polycrystalline Silicon Films Grown via Silane Pyrolysis

X-ray diffraction, transmission and scanning electron microscopy, and secondary-ion mass spectrometry data demonstrate that the grain size, structure, and composition of polycrystalline silicon (poly-Si) films grown using hydride pyrolysis depend on the GeH₄ : SiH₄ volume ratio in the gas mixture, dopant (boron or phosphorus) concentration, substrate temperature, and heat-treatment temperature. The films grown at substrate temperatures below 600°C are amorphous, and those deposited at 600°C are amorphous-crystalline. Textured poly-Si films are only obtained at 620°C or higher substrate temperatures. Doping with germanium, an isovalent impurity, improves the structural perfection of poly-Si films.     

Influence of substrate temperature on the growth and properties of reactively sputtered In-rich InAlN films

Indium-rich InAlN films were prepared on Si (111) substrates by using reactive co-sputtering in a mixed Ar-N₂ atmosphere. The substrate temperature was varied from room temperature to 300 °C to investigate the film’s growth and properties at different temperatures. Structural and optical properties of the films were evaluated through high resolution XRD and Raman spectroscopy respectively, surface morphology and roughness analysis was performed by using FE-SEM and AFM respectively, whereas the electrical characterizations were made through resistivity and current–voltage (I–V) measurements respectively. Highly c-axis oriented nanocrystalline InAlN films with wurtzite structure were obtained at a substrate temperature of 100 °C and above. Structural quality of the films was improved with increase of the substrate temperature. The Raman spectroscopy revealed A₁ (LO) modes which became more intense by the increasing the substrate temperature. The electrical studies indicated n-type nature of InAlN film having electron concentration in the range 3 × 10¹⁹–20 × 10¹⁹ cm^?3. The electrical resistivity exhibited a decreasing trend with increase of the deposition temperature. The I–V measurements showed a noticeable increase in the value of current by increasing the substrate temperature to 300 °C.     

Magnetization in Nanocrystalline PLD Zinc Ferrite Thin Films Deposited on Fused Quartz Substrate

The nanocrystalline zinc ferrite (ZnFe₂ O ₄) thin films were grown on the fused quartz substrate using pulsed laser deposition. The effects of atmospheric conditions on structural, magnetic, and morphological properties have been systematically studied using X-ray diffraction, vibrating sample magnetometry, and atomic force microscopy. The films showed textured growth of zinc ferrite for the substrate temperatures at ≥ 600 °C irrespective of the ambient environment. Interestingly, thin films of zinc ferrite showed a magnetic hysteresis loop in contrast to the paramagnetic nature of their bulk counterpart. The value of saturation magnetization (4π M _s) increased from 130 to 360 G when the substrate temperature was increased from room temperature (RT) to 800 °C in the oxygen atmosphere. In the absence of oxygen pressure, the value of 4π M _s is observed to be 330 G for the film deposited at RT and found to increase to a value of 670 G when the film is deposited at 400 °C and the maximum value of 2580 G is observed for the film deposited at 700 °C. However, the value of 4π M _s of 800 °C dropped down to 2000 G.     

Modified sol–gel preparation of LiNbO3 target for PLD

When preparing LiNbO₃ thin layer by PLD, the maximal density of polycrystalline target is important. In this work, we prepared the precursor powders by sol–gel method and used them at PLD target synthesis. The gels were synthesized by Pechini polyesterification, using citric acid and ethylene glycol as an organic matrix constituents, and then decomposed using various temperatures (800, 600 and 400 °C) and atmospheres (air, nitrogen and oxygen in sequence). Out of several combinations tested, the decomposition at 800 °C in nitrogen followed by the oxidation at 400 °C in oxygen was found to be the best way to achieve the minimal particle size of powder precursor resulting in denser targets. The prepared targets were characterized by XRD and SEM.The optimized process was subsequently used for preparation of LiNbO₃ target. Thin layers prepared by PLD from this target resulted smoother than the layers prepared from commercial monocrystalline target.     

CO<Subscript>2</Subscript> gas sensitivity of sputtered zinc oxide thin films

For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO₂ gas sensor. Zinc oxide thin films have been synthesized using reactive d.c. sputtering method for gas sensor applications, in the deposition temperature range from 130–153°C at a chamber pressure of 8·5 mbar for 18 h. Argon and oxygen gases were used as sputtering and reactive gases, respectively. ZnO phase could be crystallized using a pure metal target of zinc. The structure of the films determined by means of X-ray diffraction method indicates that the zinc oxide single phase can be fabricated in this substrate temperature range. The sensitivity of the film synthesized at substrate temperature of 130°C is 2·17 in the presence of CO₂ gas at a measuring temperature of 100°C.     

Optical properties of the c-axis oriented LiNbO3 thin film

C-axis oriented Lithium Niobate (LiNbO₃) thin films have been deposited onto epitaxially matched (001) sapphire substrate using pulsed laser deposition technique. Structural and optical properties of the thin films have been studied using the X-ray diffraction (XRD) and UV-Visible spectroscopy respectively. Raman spectroscopy has been used to study the optical phonon modes and defects in the c-axis oriented LiNbO₃ thin films. XRD analysis indicates the presence of stress in the as-grown LiNbO₃ thin films and is attributed to the small lattice mismatch between LiNbO₃ and sapphire. Refractive index (n = 2.13 at 640 nm) of the (006) LiNbO₃ thin films was found to be slightly lower from the corresponding bulk value (n = 2.28). Various factors responsible for the deviation in the refractive index of (006) LiNbO₃ thin films from the corresponding bulk value are discussed and the deviation is mainly attributed to the lattice contraction due to the presence of stress in deposited film.     

Epitaxial growth of ferromagnetic CrO2 films in air

Epitaxial growth of CrO₂ films under atmospheric pressure has been investigated. Single crystal films of CrO₂ were obtained by the thermal decomposition of gaseous CrO₃ onto the substrates of rutile single crystals in air. The optimum temperature of the substrate for the pure CrO₂ epitaxial films was found to be 390°C. At the substrate temperature of 380°C, the obtained film included Cr₂O₅ as impurities, and Cr₂O₃ appeared at 400°C. Magnetic domain patterns of these films were observed by longitudinal Kerr effect. The growth patterns of domain were obtained with applied field.     

Oriented growth of thin films of samarium oxide by MOCVD

Thin films of Sm₂O₃ have been grown on Si(100) and fused quartz by low-pressure chemical vapour deposition using an adducted β-diketonate precursor. The films on quartz are cubic, with no preferred orientation at lower growth temperatures (∼ 550°C), while they grow with a strong (111) orientation as the temperature is raised (to 625°C). On Si(100), highly oriented films of cubic Sm₂O₃ at 625°C, and a mixture of monoclinic and cubic polymorphs of Sm₂O₃ at higher temperatures, are formed. Films grown on either substrate are very smooth and fine-grained. Infrared spectroscopic study reveals that films grown above 600° C are free of carbon.     

Preparation and characterization of highly <Emphasis Type="Italic">c</Emphasis>-axis textured MgO buffer layer grown on Si(100) substrate by RF magnetron sputtering for use as growth template of ferroelectric thin film

Highly c-axis textured MgO thin films were grown directly on Si(100) substrates without any buffer layer by RF magnetron sputtering for use as growth template of ferroelectric film. We fixed the target-to-substrate spacing of 40 mm and then changed the substrate temperature, deposition pressure, and RF power to study the effect of deposition parameters on the growth of c-axis textured MgO thin films. The as-grown films were post-annealed by the rapid thermal annealing (RTA) and furnace annealing to improve the film quality. The experimental results show that the optimum deposition parameters are substrate temperature of 350 °C, oxygen pressure of 15 mTorr and RF power of 75 W. The full width at half maximum intensity (FWHM) of MgO(200) peak obtained from the XRD measurement was 0.8°, and it was further reduced to 0.5° and 0.27° after annealing by RTA and furnace, respectively. Highly c-axis textured PZT and BaTiO₃ films could be obtained on this template. Hysteresis loops of the BaTiO₃ films deposited on MgO(100) single crystalline substrate and MgO(200)/Si(100) template were measured for comparison. The results show that MgO/Si templates thus obtained are suitable for the synthesis of perovskite ferroelectric thin films.     

Structural investigation of silicon films chemically vapour deposited onto amorphous SiO2 substrates

The influence of substrate temperature and the silane-to-nitrogen ratio on the structure of silicon films 0.5–0.6 μm thick deposited onto amorphous SiO₂ substrates was investigated by X-ray diffraction. The investigations were carried out for silicon films deposited at various temperatures in the range 500–750 °C and with various silane-to-nitrogen ratios in the range 3.04 × 10^-4-2.84 × 10^-3 by volume. The silicon films deposited at 500 °C were amorphous while the films deposited at 550 °C were randomly oriented polycrystalline. The films deposited in the temperature range 600–700 °C were polycrystalline with a preferred orientation that changed from 〈110〉 through 〈100〉 to 〈111〉. The structure of the films deposited at 750 °C was randomly oriented polycrystalline. Investigations of the influence of the silane-to-nitrogen ratio on the silicon film structure revealed that the structure of films deposited at a substrate temperature of 500 °C was independent of the silane-to-nitrogen ratio. The structure of the films deposited at 600 °C depended on the silane-to-nitrogen ratio and changed from polycrystalline with a 〈110〉 preferred orientation to randomly oriented polycrystalline when the ratio was increased. The structure of films deposited at 700 °C also depended on the silane-to-nitrogen ratio and changed from randomly oriented polycrystalline to polycrystalline with double preferred orientation (〈100〉 and 〈111〉) when the ratio was increased.     

Electrochemical processing of high-T c Bi(Pb)-Sr-Ca-CuO thin films

Superconducting thin films of Bi(Pb)-Sr-Ca-CuO system were prepared by depositing the film onto silver substrate by d.c. electrodeposition technique with dimethyl sulphoxide bath in order to examine the effect of Pb addition to the BSCCO system. The films were deposited at the potential of -0.8 V vs saturated calomel electrode (SCE) onto the silver substrate. The different preparative parameters such as deposition potential, deposition time were studied and optimized. These films were then oxidized electro-chemically at room temperature in an alkaline (1 N KOH) solution, and also at 600°C temperature in an oxygen atmosphere. The films showed the superconducting behaviour, with T_c values ranging between 85 K and 96 K, respectively.     

Photoluminescence behaviors in ZnGa2O4 thin film phosphors deposited by a pulsed laser ablation

ZnGa₂O₄ thin film phosphors have been deposited using a pulsed laser deposition technique on Si (1 0 0) and Al₂O₃ (0 0 0 1) substrates at a substrate temperature of 550 °C with various oxygen pressures 100, 200 and 300 mTorr, and various substrate temperatures of 450, 550 and 650 °C with a fixed oxygen pressure of 100 mTorr. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. Under the different substrate temperatures, ZnGa₂O₄ thin films show the different crystallinity and luminescent intensity. The crystallinity and photoluminescence (PL) of the ZnGa₂O₄ films are highly dependent on the deposition conditions, in particular, oxygen pressure, substrate temperature, a kind of substrates. The luminescent spectra show a broad band extending from 350 to 600 nm peaking at 460 nm. The PL brightness data obtained from the ZnGa₂O₄ films grown under optimized conditions have indicated that the sapphire is one of the most promised substrates for the growth of high quality ZnGa₂O₄ thin film phosphor.