Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)—nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO₂ nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.     

Structural and morphological properties of thin ZnO films grown by pulsed laser deposition

The pulsed laser deposition technique was used to produce zinc oxide thin films onto silicon and Corning glass substrates. Homogeneous surfaces exhibiting quite small Root Mean Square (RMS) roughness, consisting of shaped grains were obtained, their grain diameters being 40-90 nm at room temperature and at 650 °C growth respectively. Films were polycrystalline, even for growth at room temperature, with preferential crystallite orientation the (0 0 2) basal plane of wurtzite ZnO. Temperature increase caused evolution from grain to grain agglomeration structures, improving crystallinity. Compressive to tensile stresses transition with temperature was found while the lattice constant decreased.     

Structural properties of the titanium dioxide thin films grown by atomic layer deposition at various numbers of reaction cycles

A dependence of structural properties of TiO₂ films grown on both Si- and Ti-substrates by atomic layer deposition (ALD) at the temperature range of 250-300 °C from titanium ethoxide and water on the number of reaction cycles N was investigated using Fourier-transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD). TiO₂ films grown on both Si- and Ti-substrates revealed amorphous structure at low values of N < 400. However, an increase of N up to values 400-3600 resulted in the growth of polycrystalline TiO₂ with structure of anatase on both types of substrates and according to XRD-measurements the sizes of crystallites rose with the increase of N. The maximum anatase crystallite size for TiO₂ grown on Ti-substrate was found to be on ∼35% lower in comparing with that for TiO₂ grown on Si-substrate. A use of titanium methoxide as a Ti precursor with the ligand size smaller than in case of titanium ethoxide allowed to observe an influence of the ligand size on both the growth per cycle and structural properties of TiO₂. The average growth per cycle of TiO₂ deposited from titanium methoxide and water (0.052 ± 0.01 nm/cycle) was essentially higher than that for TiO₂ grown from titanium ethoxide and water (0.043 ± 0.01 nm/cycle). Ligands of smaller sizes were found to promote the higher crystallinity of TiO₂ in comparison with the case of using the titanium precursor with ligands of bigger sizes.     

Modelling ion-assisted deposition of CeO2 films

The theory presented explains quantitatively the experimentally observed increase in film density of a vapor-deposited CeO₂ film when bombarded during growth with low-energy O ₂ ⁺ ions. The density enhancement is expressed in terms of the yields for recoil implantation of surface atoms, ion incorporation and sputtering, which have been determined by employing a three-dimensional Monte Carlo cascade calculation. Ion-to-vapor flux ratios between 0 and 1.4 and O⁺ ion energies between 25 and 600 eV have been examined. The density shows an almost linear increase with the ratio of ion-to-vapor fluxes. An optimum O⁺ ion energy for densification is found at about 200 eV which is in agreement with experiment.     

Photocatalytic properties of TiO2 thin films obtained by glancing angle deposition

Titanium dioxide (TiO₂) thin films with different nanostructures such as nano-particles and separated vertical columns were grown by glancing angle deposition (GLAD) in an electron beam evaporation system. The photocatalytic properties of grown TiO₂ films with different deposition angles and different annealing temperatures were evaluated by following decomposition of methyl orange under ultraviolet (UV) light irradiation. The results suggest that increased surface area due to the GLAD process could improve the photocatalytic properties of TiO₂ films.     

利用脉冲激光沉积技术在双轴织构的Ni基带上外延CeO2薄膜

利用脉冲激光沉积技术在氢还原气氛下成功地在双轴织构的Ni基带上外延了高质量的CeO2薄膜.x射线衍射θ-2θ扫描和ω扫描结果表明,CeO2薄膜在Ni基带上呈c轴方向生长,存在很强的平面外织构;极图和ψ扫描显示它具有良好的平面内织构.Ni基片上织构的CeO2薄膜为进一步在其上外延高质量的YBa2Cu3O7-x超导薄膜提供了很好的模板.     

Atomic layer deposition of HfO2: Effect of structure development on growth rate, morphology and optical properties of thin films

HfO₂ films were grown by atomic layer deposition from HfCl₄ and H₂O on Si(1 0 0), Si(1 1 1) and amorphous SiO₂ substrates at 180-750 °C and the effect of deposition temperature and film thickness on the growth rate and optical properties of the film material was studied. Crystallization, texture development and surface roughening were demonstrated to result in a noticeable growth rate increase with increasing film thickness. Highest surface roughness values were determined for the films deposited at 350-450 °C on all substrates used. The density of the film material increased with the concentration of crystalline phase but, within experimental uncertainty, was independent of orientation and sizes of crystallites in polycrystalline films. Refractive index increased with the material density. In addition, the refractive index values that were calculated from the transmission spectra depended on the surface roughness and crystallite sizes because the light scattering, which directly influenced the extinction coefficient, caused also a decrease of the refractive index determined in this way.     

Structural and morphological study of ZnO thin films electrodeposited on n-type silicon

In this work, we report on the electrodeposition of ZnO thin films on n-Si (1 0 0) and glass substrates. The influence of the deposition time on the morphology of ZnO thin films was investigated. The ZnO thin films were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDS) and scanning electron microscopy (SEM). The results show a variation of ZnO texture from main (0 0 2) at 10 min to totally (1 0 1) at 15 min deposition time. The photoluminescence (PL) studies show that both UV (∼382 nm) and blue (∼432 nm) luminescences are the main emissions for the electrodeposited ZnO films. In addition, the film grown at 15 min indicates an evident decrease of the yellow-green (∼520 nm) emission band comparing with that of 10 min. Finally, transmittance spectra show a high transmission value up to 85% in the visible wavelength range. Such results would be very interesting for solar cells applications.     

Spray-pyrolysis deposition of CeO2 thin films using citric or tartaric complexes as starting materials

Thin films of CeO₂ were deposited by spray-pyrolysis on β-quartz or optical grade silica glass substrates heated at 350–500 °C. Ethylene glycol solutions of Ce(NO₃)₃ and cerium citrates or tartrates (prepared using Ce(NO₃)₃ or CeCl₃ as cerium sources) were used as starting materials. Crystalline films may be obtained “in situ”. Post deposition annealing at 800 °C leads to bigger crystallites and cell constant closer to that of a reference material. The influence of the deposition temperature and the nature of the cerium compounds on the crystal structure and morphology of the films were studied.     

Influence of deposition conditions on nanostructured InSe thin films

In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxide (ITO)-coated glass substrate using electrochemical deposition (ECD) from aqueous solution containing In(SO₄)₃.H₂O and SeO₂. The effects of deposition potential (−0.70 to −1.35 V), time (30-3600 s), temperature (25-80 °C) and pH (2.58 for A samples; 2 for B samples and 1.45 for C samples) on growth of the InSe thin films were examined in terms of their structural, morphological and optical properties. X-ray diffraction (XRD) analysis confirmed that the InSe thin films are in polycrystalline structure. It was found that the values of grain size decreased and the full width half maximum (FWHM) values increased with the increasing deposition potential. According to the absorption measurements, optical properties of the thin films varied with changes in deposition conditions. Based on the atomic force microscopy (AFM) and the scanning electron microscopy (SEM) images, surface morphology of the thin films was influenced by deposition potential and pH of the electrolyte, and non-homogeneous depositions distributed across the entire surface were observed. In addition, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR) analyses were used to further examine crystal quality, vibration, chemical binding conditions, In/Se orientation and structure of the prepared InSe thin films. When Raman results are examined, the B12 sample shows a more intensity and narrow peak at 248 cm⁻¹. XPS measurements sowed that A6 sample exhibited more growth in low potential for a long time and better film stoichiometry compared to the other three samples. Also, FT-IR studies prove the presence of InSe. According to the results, the film did not form at low temperatures and short times. However, the film formation began with the increasing deposition temperature and time at the low potential value of −0.730 V. But, it is clear that a high quality film can be obtained in cathodic potential with −1.3 V and shorter deposition time with 300 s at room temperature respectively. Overall results showed that the high quality thin films can be obtained by the ECD technique. However, deposition conditions must be sensitively adjusted to control morphology of the electrodeposited nanoparticles.     

Nickel-induced microwheel-like surface morphological evolution of ZnO thin films by spray pyrolysis

Nickel?Czinc oxide (Ni?CZnO) thin films were deposited onto glass and tin-doped indium oxide-coated glass substrates by using a pneumatic spray pyrolysis technique at 450?°C from aqueous solutions of zinc acetate and nickel acetate precursors. The effect of nickel doping on structural, morphological and optical properties of the ZnO thin films has been studied. The X-ray diffraction patterns confirmed the polycrystalline nature of the films having hexagonal crystal structure. Ni?CZnO films with appropriate nickel doping revealed the occurrence of novel wheel-like surface morphology. The absorption edge of the Ni?CZnO films showed a red shift, meaning that the optical band gap energy decreases as the nickel doping concentration increases. A growth model is developed and proposed for the novel wheel-like morphology. All the thin films exhibited room-temperature photoluminescence. Pure ZnO and Ni?CZnO thin films were tested for their photoelectrochemical performance in 0.5 M Na₂SO₄ electrolyte solution. The values of fill factor and open circuit voltage were improved for the Ni?CZnO thin films.     

Layer-by-layer deposition of Ti-4,4′-oxydianiline hybrid thin films

Features of the two thin-film techniques, atomic layer deposition (ALD) and molecular layer deposition (MLD), are combined to build up a stable novel inorganic-organic hybrid material of the (-Ti-N-C₆H₄-O-C₆H₄-N-)_n type, deposited from successive pulses of TiCl₄ and 4,4′-oxydianiline precursors. Depositions in the temperature range of 160-230 °C resulted in unstable films, while the films obtained in the temperature range of 250-490 °C were found stable in atmospheric air. The growth rate increased with increasing temperature, from 0.3 Å per cycle at 160 °C to 1.1 Å per cycle at 490 °C.     

原子层沉积HfO_2薄膜的激光损伤特性分析

以目前激光惯性约束聚变中应用最广泛的高折射率材料二氧化铪(HfO2)为研究对象,在熔石英基底上分别采用TEMAH和HfCl4前驱体制备了HfO2薄膜,沉积温度分别为100,200和300℃。采用椭偏仪和激光量热计对薄膜的光学性能进行了测量分析,采用X射线衍射仪(XRD)对薄膜的微结构进行了测量。最后在小口径激光阈值测量平台上按照1-on-1测量模式对薄膜的损伤阈值进行了测试,并采用扫描电子显微镜(SEM)对损伤形貌进行了分析。研究表明,用同一种前驱体源时,随着沉积温度升高,薄膜折射率增加,吸收增多,损伤阈值降低。在相同温度下,采用有机源制备的薄膜更容易在薄膜内部形成有机残留,导致薄膜吸收增加,损伤阈值降低。采用HfCl4作为前驱体源在100℃制备氧化铪薄膜时,损伤阈值能够达到31.8J/cm2(1064nm,3ns)。     

溶胶凝胶法制备参氟二氧化锡薄膜

利用溶胶凝胶方法，在硅碱玻璃底板上制备的透明低电阻SnO2:F薄膜，是一种低辐射导电薄膜。将SnCl4·5H2O 和 NH4F 溶解在50%乙醇和50%水的溶液中。制备条件为底板温度450℃，喷嘴与底板之间的距离60mm,载气流速8 L/min，制备时间5分钟。制成的SnO2:F薄膜面电阻为2Ω/□，可重复性好。并且文中还定性给出了SnO2:F薄膜其红外反射率与面电阻之间的关系。     

Stimuli-responsive self-assembled multilayer azo thin films: Photo-switchable absorbance and morphological characteristics

Light has been employed as a source of energy for surface modulation, tuning and control in photo-responsive azo-incorporating self-assembled polyelectrolyte multilayer thin films. A custom built setup for controlled exposure enabled successful photo-switching. Spectral changes were characterized through UV–vis spectroscopy, while scanning electron microscopy technique was employed to study structural properties and response of the films. The effects of chromophore aggregation and dispersion on thin film photo-responsiveness have been studied, with significant contributions made to a recently proposed model correlating structural and spectral properties of the azo thin films. Structural and optical photo-responses have been acquired for surface tuning and modulation, while photo-reversibility is also achieved to control surface properties cyclically.     

Non-stoichiometry-induced metal-to-insulator transition in nickelate thin films grown by pulsed laser deposition

While controlling the cation contents in perovskite rare-earth nickelate thin films, a metal-to-insulator phase transition is reported. Systematic control of cation stoichiometry has been achieved by manipulating the irradiation of excimer laser in pulsed laser deposition. Two rare-earth nickelate bilayer thin-film heterostructures with the controlled cation stoichiometry (i.e. stoichiometric and Ni-excessive) have been fabricated. It is found that the Ni-excessive nickelate film is structurally less dense than the stoichiometric film, albeit both of them are epitaxial and coherent with respect to the underlying substrate. More interestingly, as a temperature decreases, a metal-to-insulator transition is only observed in the Ni-excessive nickelate films, which can be associated with the enhanced disproportionation of the Ni charge valence. Based on our theoretical results, possible origins (e.g. anti-site defects) of the low-temperature insulating state are discussed with the need of future work for deeper understanding. Our work can be utilized to realize unusual physical phenomena (e.g. metal-to-insulator phase transitions) in complex oxide films by manipulating the chemical stoichiometry in pulsed laser deposition.     

ZnS thin films grown by atomic layer deposition on GaAs and HgCdTe substrates at very low temperature

ZnS films grown on GaAs and HgCdTe substrates by atomic layer deposition (ALD) under very low temperature were investigated in this work. ZnS films were grown under several temperatures lower than 140 °C. The properties of the films were investigated with high-resolution X-ray diffraction (HRXRD), scanning electron microscope (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed the ZnS films were polycrystalline. The growth rate monotonically decreased with temperature, as well as the root mean square (r.m.s) roughness measured by AFM. XPS measurement revealed the films were stoichiometric in Zn and S.     

Effects of deposition temperature on the structural and morphological properties of thin ZnO films fabricated by pulsed laser deposition

ZnO thin films were grown on Si(1 0 0) substrates using pulsed laser deposition in O₂ gas ambient (10 Pa) and at different substrate temperatures (25, 150, 300 and 400 °C). The influence of the substrate temperature on the structural and morphological properties of the films was investigated using XRD, AFM and SEM. At substrate temperature of T=150 °C, a good quality ZnO film was fabricated that exhibits an average grain size of 15.1 nm with an average RMS roughness of 3.4 nm. The refractive index and the thickness of the thin films determined by the ellipsometry data are also presented and discussed.     

Nanostructural and surface morphological evolution of chemically sprayed SnO2 thin films

Physical properties of a nanocrystalline thin film is greatly influenced by its morphological and structural evolution. We try to understand the transition of SnO₂ thin films from amorphous to nanocrystalline structure with XRD, IR, SEM, AFM and surface profiler studies. A 2D layer like structure resulting from quantum confinement is found for the films prepared at 400 °C. We observed a new IR band at 530 cm⁻¹ that was theoretically predicted and report it for the first time. A correlation of population of defects in SnO₂ films with change in lattice parameters and FWHM of IR bands are reported. The electric and optical properties of the films have been discussed.     

Photocatalytic and optical properties of titanium dioxide thin films prepared by metalorganic chemical vapor deposition

Titanium dioxide thin films have been deposited by metalorganic chemical vapor deposition (MOCVD) over sodalime glass substrates at substrate temperatures ranging from 250 °C to 450 °C. The effect of deposition temperature on the structure and microstructure of the obtained films has been studied by x-rays diffraction (XRD) and scanning electron microscopy (SEM), respectively. Diffraction patterns show the existence of a pure anatase phase beside a texture change with the increase of deposition temperature. Micrographs show grain fragmentation with the increase in deposition temperature. UV–Vis. spectra have been recorded by spectrophotometery. The optical energy gap has been calculated for the deposited films from the spectrophotometrical data. Photocatalytic experiments have been carried out. The photocatalytic activity has been found to decrease with the increase in deposition temperature.