Photoluminescence at room temperature in amorphous SrTiO3 thin films obtained by chemical solution deposition

Intense photoluminescence in highly disordered strontium titanate amorphous thin films prepared by the polymeric precursor method was observed at room temperature (300 K). The luminescence spectra of SrTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region. X-ray absorption near edge structure was used to probe the local atomic structure of SrTiO3 amorphous and crystalline thin films. Photoluminescence intensity in the 535 nm range was found to be correlated with the presence of non-bridging oxygen defects. A discussion is presented of the nature of this photoluminescence, which may be related to the disordered structure in SrTiO3 amorphous thin films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Correlation between the surface morphology and structure and the photoluminescence of amorphous PbTiO3 thin films obtained by the chemical route

A polymeric precursor method was used to synthesis PbTiO3 amorphous thin film processed at low temperature. The luminescence spectra of PbTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region, the visible emission band was found to be dependent on the thermal treatment history, Photoluminescence properties Versus different annealing temperatures were investigated. The experimental results (XRD, AFM, FL) indicate that the nature of photoluminescence (PL) must be related to the disordered structure of PbTiO3 amorphous thin films, Copyright (C) 2000 John Wiley & Sons, Ltd.

Thin films prepared from tungstate glass matrix

Vitreous samples containing high concentrations of WO3 (above 40% M) have been used as a target to prepare thin films. Such films were deposited using the electron beam evaporation method onto soda-lime glass substrates. These films were characterized by X-ray diffraction (XRD), perfilometry, X-ray energy dispersion spectroscopy (EDS), M-Lines and UV-vis absorption spectroscopy. In this work, experimental parameters were established to obtain stable thin films showing a chemical composition close to the glass precursor composition and with a high concentration of WO3. These amorphous thin films of about 4 mu m in thickness exhibit a deep blue coloration but they can be bleached by thermal treatment near the glass transition temperature. Such bleached films show several guided modes in the visible region and have a high refractive index. Controlled crystallization was realized and thus it was possible to obtain WO3 microcrystals in the amorphous phase. (C) 2007 Elsevier B.V. All rights reserved.

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb1-XLaXTiO3 thin films, (X = 0.0; 13 and 0.27 mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO2/Si (1 1 1), Si (1 0 0) and glass substrates by spin coating, and annealed in the 200-300degreesC range in an O-2 atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO3. The films deposited on Pt/Ti/SiO2/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Diverse Amorphous Carbonaceous Thin Films Obtained by Plasma Enhanced Chemical Vapor Deposition and Plasma Immersion Ion Implantation and Deposition

Diverse amorphous hydrogenated carbon and similar films containing additional elements were produced by Plasma Enhanced Chemical Vapor Deposition (PECVD) and by Plasma Immersion Ion Implantation and Deposition (PIIID). Thus a-C:H, a-C:H:F, a-C:H:N, a-C:H:Cl and a-C:H:O:Si were obtained, starting from the same feed gases, using both techniques. The same deposition system supplied with radiofrequency (RF) power was used to produce all the films. A cylindrical stainless steel chamber equipped with circular electrodes mounted horizontally was employed. RF power was fed to the upper electrode; substrates were placed on the lower electrode. For PIIID negative high tension pulses were also applied to the lower electrode. Raman spectroscopy confirmed that all the films are amorphous. Chemical characterization of each pair of films was undertaken using Infrared Reflection Absorption Spectroscopy and X-ray Photoelectron Spectroscopy. The former revealed the presence of specific structures, such as C-H, C-O, O-H. The latter allowed calculation of the ratio of hetero-atoms to carbon atoms in the films, e. g. F:C, N:C, and Si:C. Only relatively small differences in elemental composition were detected between films produced by the two methods. The deposition rate in PIIID is generally reduced in relation to that of PECVD; for a-C:H:Cl films the reduction factor is almost four.

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb1-xLaxTiO3 thin films, (X=0.0; 13 and 0.27mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO2/Si(111), Si(100) and glass substrates by spin coating, and annealed in the 200-300°C range in an O2 atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO3. The films deposited on Pt/Ti/SiO2/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration. © 2002 Elsevier Science B.V. All rights reserved.

Optical, mechanical and surface properties of amorphous carbonaceous thin films obtained by plasma enhanced chemical vapor deposition and plasma immersion ion implantation and deposition

Diverse amorphous hydrogenated carbon-based films (a-C:H, a-C:H:F, a-C:H:N, a-C:H:Cl and a-C:H:Si:O) were obtained by radiofrequency plasma enhanced chemical vapor deposition (PECVD) and plasma immersion ion implantation and deposition (PIIID). The same precursors were used in the production of each pair of each type of film, such as a-C:H, using both PECVD and PIIID. Optical properties, namely the refractive index, n, absorption coefficient, α, and optical gap, ETauc, of these films were obtained via transmission spectra in the ultraviolet-visible near-infrared range (wavelengths from 300 to 3300 nm). Film hardness, elastic modulus and stiffness were obtained as a function of depth using nano-indentation. Surface energy values were calculated from liquid drop contact angle data. Film roughness and morphology were assessed using atomic force microscopy (AFM). The PIIID films were usually thinner and possessed higher refractive indices than the PECVD films. Determined refractive indices are consistent with literature values for similar types of films. Values of ETauc were increased in the PIIID films compared to the PECVD films. An exception was the a-C:H:Si:O films, for which that obtained by PIIID was thicker and exhibited a decreased ETauc. The mechanical properties - hardness, elastic modulus and stiffness - of films produced by PECVD and PIIID generally present small differences. An interesting effect is the increase in the hardness of a-C:H:Cl films from 1.0 to 3.0 GPa when ion implantation is employed. Surface energy correlates well with surface roughness. The implanted films are usually smoother than those obtained by PECVD. ©2013 Elsevier B.V. All rights reserved.

Polymeric precursor method to the synthesis of XWO(4) (X = Ca and Sr) thin films-Structural, microstructural and spectroscopic investigations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pressure-induced electrical and structural anomalies in Pb1-xCaxTiO3 thin films grown at various oxygen pressures by chemical solution route

Lead calcium titanate (Pb1-xCaxTiO3 or PCT) thin films have been thermally treated under different oxygen pressures, 10, 40 and 80 bar, by using the so-called chemical solution deposition method. The structural, morphological, dielectric and ferroelectric properties were characterized by x-ray diffraction, FT-infrared and Raman spectroscopy, atomic force microscopy and polarization-electric-field hysteresis loop measurements. By annealing at a controlled pressure of around 10 and 40 bar, well-crystallized PCT thin films were successfully prepared. For the sample submitted to 80 bar, the x-ray diffraction, Fourier transformed-infrared and Raman data indicated deviation from the tetragonal symmetry. The most interesting feature in the Raman spectra is the occurrence of intense vibrational modes at frequencies of around 747 and 820 cm(-1), whose presence depends strongly on the amount of the pyrochlore phase. In addition, the Raman spectrum indicates the presence of symmetry-breaking disorder, which would be expected for an amorphous (disorder) and mixed pyrochlore-perovskite phase. During the high-pressure annealing process, the crystallinity and the grain size of the annealed film decreased. This process effectively suppressed both the dielectric and ferroelectric behaviour. Ferroelectric hysteresis loop measurements performed on these PCT films exhibited a clear decrease in the remanent polarization with increasing oxygen pressure.

Photoluminescence at room temperature in disordered Ba(0.50)Sr(0.)5(0)(Ti0.80Sn0.20)O-3 thin films

Photoluminescence (PL) properties at room temperature of disordered Ba0.50Sr0.50(Ti0.80Sn0.20)O-3 (BST:Sn) thin films were obtained by the polymeric precursor method. X-ray diffraction data and corresponding PL properties have been measured using the 488 nm line of an argon ion laser. The PL spectra of the film annealed at 350 degrees C for 21 h are stronger than those of the film annealed at 350 degrees C for 28 h, indicating a disorganized structure. The energy band gaps of the crystalline and amorphous BST:Sn thin films were 3.35 and 2.25 eV, respectively. The doped BST thin films also tend to a cubic structure, resulting from TiO6 deformations. (c) 2006 American Institute of Physics.

The influence of crystallization route on the properties of lanthanum-doped Bi4Ti3O12 thin films prepared from polymeric precursors

Pure and lanthanum-doped Bi4Ti3O12 thin films were deposited on Pt/Ti/SiO2/Si substrate using a polymeric precursor solution. The spin-coated films were specular and crack-free and crystalline after annealing at 700 degreesC for 2 h. Crystallinity and morphological evaluation were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Multilayered films obtained using the intermediate-crystalline layer route present a dense microstructure with spherical grains. Films obtained using the intermediate-amorphous layer, present elongated grains around 250 nm in size. The dielectric and ferroelectric properties of the lanthanum-doped Bi4Ti3O12 films are strongly affected by the crystallization route. The hysteresis loops are fully saturated with a remnant polarization and drive voltage of the films, heat-treated by the intermediate-crystalline (P-r = 20.2 muC/cm(2) and V = 1.35 V) and for the film heat-treated by amorphous route (P-r = 22.4 muC/cm(2) and V = 2.99 V). (C) 2004 Elsevier B.V. All rights reserved.

Hydrogen influence on gallium arsenide thin films prepared by rf-magnetron sputtering technique

We investigate the effect of the hydrogen intentional incorporation on the structural properties of the amorphous gallium arsenide prepared by rf-magnetron sputtering technique. The properties of the non-hydrogenated films are: band gap of 1.4 eV (E-04), Urbach energy of 110 meV, stoichiometric composition ([As]/[Ga] = 0.50), and dark conductivity of about 3.2 x 10(-5) (Omega.cm)(-1). Hydrogen was incorporated in the films by the introduction of an electronically controlled H-2 flux during deposition, keeping constant the other deposition parameters. It was observed that small hydrogen incorporation produces a great change in the structural properties of the films. The main changes result from the formation of GaAs nanocrystals with mean sizes of about 7 nm into the amorphous network.

Local and global magnetic properties of Zn1-xCoxO and Mn-doped GaAs thin films

Amorphous and crystalline thin films of Mn-doped(0.5%-10%) GaAs and crystalline thin films of Zn1-xCoxO(x = 3%-20%) were investigated by means of magnetic susceptibility and electron spin resonance (ESR). For the Mn-doped GaAs samples, our results show the absence of ferromagnetic ordering for the amorphous films in the 300 > T > 2 K temperature range, in contrast to the ferromagnetism found in crystalline films for T-C < 110 K. A single ESR line with a temperature independent g-value (g similar to 2) is observed for the amorphous films, and the behavior of this ESR linewidth depends on the level of crystallinity of the film. For the Mn-doped GaAs crystalline films, only a ferromagnetic mode is observed for T < TC when the film is ferromagnetic. Turning now the Zn1-xCoxO films, ferromagnetic loops were observed at room temperature for these films. The magnetization data show an increasing of the saturation magnetization M. as a function of x reaching a maximum value for x approximate to 10%. ESR experiments at T = 300 K in the same films show a strong anisotropic ferromagnetic mode (FMR) for x = 0.10.

Preparation, structural and optical characterization of BaWO4 and PbWO4 thin films prepared by a chemical route

Polycrystalline BaWO4 and PbWO4 thin films having a tetragonal scheelite structure were prepared at different temperatures. Soluble precursors such as barium carbonate, lead acetate trihydrate and tungstic acid, as starting materials, were mixed in aqueous solution. The thin films were deposited on silicon, platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure of the thin films were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, and specular reflectance infrared Fourier transform spectroscopy, respectively. Nucleation stages and surface morphology evolution of thin films on silicon substrates have been studied by atomic force microscopy. XRD characterization of these films showed that BaWO4 and PbWO4 phase crystallize at 500 degreesC from an inorganic amorphous phase. FTIR spectra revealed the complete decomposition of the organic ligands at 500 degreesC and the appearance of two sharp and intense bands between 1000 and 600 cm(-1) assigned to vibrations of the antisymmetric stretches resulting from the high crystallinity of both thin films. The optical properties were also studied. It was found that BaWO4 and PbWO4 thin films have Eg = 5.78 eV and 4.20 eV, respectively, of a direct transition nature. The excellent microstructural quality and chemical homogeneity results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of BaWO4 and PbWO4 thin films. (C) 2003 Elsevier Ltd. All rights reserved.

Ba1-xSrxTiO3 thin films by polymeric precursor method

Stoichiometric Ba1-xSrxTiO3 (BST; x = 0.4) thin films were prepared by the polymeric precursor method. High quality polycrystalline films of BST with low roughness (approximate to 3 nm) were obtained from a Pt/Ti/SiO2/Si substrate deposited by spin-coating technique. Microstructure and morphological evaluation were done using grazing incident X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Grazing incident angle XRD characterization of these films showed that BST phase crystallizes at 600 degrees C from an inorganic amorphous matrix. No intermediate crystalline phase was identified. A linear relationship between roughness and grain size was observed. (C) 2000 Elsevier B.V. B.V. All rights reserved.