Amorphous Glass Substrates Research Articles

Optical and Structural Properties of Spin Coated Cadmium Sulfide Thin Films

Thin films of cadmium sulfide have been synthesized using the spin coating technique. Films were fabricated on inexpensive amorphous glass substrates at spin speeds of 1500, 2200 and 2400 rpm for 30 seconds. Films were subsequently annealed at 200, 300 and 400 0C for one hour in air in order to crystallize the phase of CdS. Films were characterized using X-ray diffraction patterns (XRD) and UV-visible spectroscopy. According to XRD patterns, the phase of CdS was crystallized without any secondary phases. The particle size, dislocation density and strain were also estimated using XRD patterns. All the films indicate a strong orientation in (002) direction. The optical band gap was determined using UV absorption spectroscopy. Tauc model was employed to determine the optical band gap. According to our data, the optical band gap decreases with the particle size.

A single-source precursor approach to solution processed indium arsenide thin films.

This paper reports the synthesis of the novel single-source precursor, [{(MeInAs t Bu)3}2(Me2InAs( t Bu)H)2] and the subsequent first report of aerosol-assisted chemical vapour deposition of InAs thin films. Owing to the use of the single-source precursor, highly crystalline and stoichiometric films were grown at a relatively low deposition temperature of 450 °C. Core level XPS depth profiling studies showed some partial oxidation of the film surface, however this was self-limiting and disappeared on etch profiles. Valence band XPS analysis matched well with the simulated density of state spectrum. Hall effect measurements performed on the films showed that the films were n-type with promising resistivity (3.6 × 10-3 Ω cm) and carrier mobility (410 cm2 V-1 s-1) values despite growth on amorphous glass substrates.

Optical and morphological properties of thin films of bis-pyrenyl π-conjugated molecules.

1,4-Di-n-octyloxy-2,5-bis(pyren-1-ylethenyl)benzene (bis-pyrene) has been studied by the means of surface cavity ring-down (s-CRD) spectroscopy on an amorphous BK7 glass substrate and scanning tunnelling microscopy (STM) on Au(111). Absorption spectra show a modification of the optical properties as a function of coverage, i.e. appearance of a shoulder around 505 nm followed by a saturation of the intensity of this signal observed at higher coverages. We attribute this shoulder to the change of the molecular orientation between the first and the second monolayer and thus to an interfacial effect. These results are confirmed by scanning tunnelling microscopy (STM) measurements where the bis-pyrene molecules have been deposited on Au(111) at room temperature (RT) and onto a cold substrate. Independently of the temperature in the range from 210 K to RT, the first monolayer is always highly organized. At low temperature bis-pyrene molecules constituting the second monolayer are randomly distributed, suggesting that self-organisation is kinetically hindered. Deposited at room temperature, the molecular diffusion is enhanced and the formation of an organized second layer takes place after storing the sample for 150 minutes at room temperature. A HOMO-LUMO gap of 2.85 eV has been determined by scanning tunnelling spectroscopy, which is in very good agreement with the observed optical transition at 434 nm (2.86 eV) in s-CRD spectroscopy.

Effect of annealing temperature on microstructure and thermoelectric properties of bismuth–telluride multilayer thin films prepared by magnetron sputtering

N-type bismuth–telluride (Bi–Te) multilayer thin films with total thickness of about 900 nm were deposited on amorphous structure glass substrate by magnetron sputtering at room temperature. The films were annealed at different temperatures under Ar ambient for 1 hour. The effect of annealing temperature was investigated for Bi–Te multilayer thin films by surface topography, chemical composition, crystal structure and thermoelectric properties. The results show that the Bi–Te multilayer thin films are all transformed into Bi–Te-based compounds. With the annealing temperature increasing, the films undergo an island growth mode with column structure, and grain size increases from 16·4 to 23·1 nm; in addition, the electrical conductivity and carrier mobility increase monotonously. The maximum Seebeck coefficient (−98·5 μV K−1) and power factor (14·47 μW K−2 cm−1) can be obtained for stoichiometric Bi2Te3 films annealed at 150°C.

Growth and optical properties of gallium nitride film on glass substrates

AbstractIn this study, gallium nitride (GaN) films were grown on the quartz glass substrates using metal organic chemical vapor deposition with AlN buffer layer. The AlN layer was deposited using rf‐magnetron sputtering. Although the direct nucleation of GaN on quartz glass substrate is difficult, with AlN as the nucleation layer, a large‐area polycrystalline GaN film can be obtained. The structural and optical properties were investigated. The results show that the GaN film has a preferential orientation along (0002). There are mainly three emission regions in the photoluminescence spectra, including the band‐edge, green (2.45‐2.55eV) and yellow (2.0‐2.35 eV) emission regions. The origin and temperature dependence of the peak position, full‐width of half‐magnitude and intensity were also discussed. The findings may help to understand the growth and improve the properties of GaN film grown on amorphous glass substrates. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nano-ZnS thin films for solar cell

In this paper, we report the effect of deposition time on the properties of zinc sulfide thin films. The ZnS thin films have been grown on amorphous glass substrates and at various deposition periods ranging from 30 to 120 min by chemical bath deposition technique. Other parameters, such as reactant concentration, solution pH, and bath temperature were kept constant for the all depositions. Morphological characterizations of the surface were studied using the atomic force microscopy (AFM). The AFM images confirmed that the grain size of ZnS increased with increased deposition time. Average diameter of nanoparticles was between 60 and 90 nm, while the roughness ranged from 6 to 11 nm. Optical properties, which were determined from UV‐VIS spectrophotometry, were obtained by analyzing the measured absorbance and transmittance spectrum. The zinc sulfide thin films show high transmittance in the visible region and the ZnS band gap value was estimated to be in range of 3.99 ‐ 4.05 eV.

Zinc oxide films prepared via the lateral growth of aligned nanorod arrays

Continuous polycrystalline zinc oxide films 5 to 15 μm in thickness have been produced on both single-crystal silicon and transparent amorphous glass substrates via the growth of aligned nanorod arrays by chemical vapor deposition followed by lateral growth of the nanorods. The growth of the lateral faces of the nanorods was carried out under specially adjusted conditions in the same reactor as was used to grow the nanorods. The resultant films consisted of intergrown columnar crystals oriented along the c axis of the ZnO lattice (perpendicular to the substrate surface). The cathodoluminescence spectrum of the films was dominated by excitonic emission in the near-UV spectral region. The films had high electrical conductivity (ρ = 0.45 Ω cm), due to excess zinc. Prolonged annealing in air increased the resistivity of the films by five orders of magnitude (to ρ = 6 × 104 Ω cm). According to X-ray diffraction and Raman spectroscopy data, the films had good structural perfection, comparable to that of zinc oxide nanorods.

The influence of voltage applied between the electrodes on optical and morphological properties of the InGaN thin films grown by thermionic vacuum arc.

The aim of this research is to investigate the optical and morphological properties of the InGaN thin films deposited onto amorphous glass substrates in two separate experiments with two different voltages applied between the electrodes, i.e. 500 and 600 V by means of the thermionic vacuum arc technique. This technique is original for thin film deposition and it enables thin film production in a very short period of time. The optical and morphological properties of the films were investigated by using field emission scanning electron microscope, atomic force microscope, spectroscopic ellipsometer, reflectometer, spectrophotometer, and optical tensiometer. Optical properties were also supported by empirical relations. The deposition rates were calculated as 3 and 3.3 nm/sec for 500 and 600 V, respectively. The increase in the voltage also increased the refractive index, grain size, root mean square roughness and surface free energy. According to the results of the wetting experiments, InGaN samples were low-wettable, also known as hydrophobic.

Roles of grain boundaries on the semiconductor to metal phase transition of VO2 thin films

Vanadium dioxide (VO2) thin films with controlled grain sizes are deposited on amorphous glass substrates by pulsed laser deposition. The grain boundaries (GBs) are found as the dominating defects in the thin films. The semiconductor to metal transition (SMT) properties of VO2 thin films are characterized and correlated to the GB density. The VO2 films with lower GB density exhibit a sharper SMT with a larger transition amplitude. A high resolution TEM study at GB area reveals the disordered atomic structures along the boundaries and the distorted crystal lattices near the boundaries. The VO2 SMT amplitude and sharpness could be directly related to these defects at and near the boundaries.

Hardness of Mn2V2O7 thin films and its influential factors

Mn2V2O7 thin films were deposited onto amorphous glass substrates using a chemical bath deposition method and different deposition time. X-ray diffraction (XRD) analysis was used to define the structure of the films. Their roughness, thickness, and surface properties were evaluated through atomic force microscopy (AFM). The hardness of the films was measured using a nanohardness tester. The film thickness, average grain size, and roughness were positively correlated with each other. These three parameters were observed to increase with the deposition time. The film thickness and average grain size were inversely correlated with the hardness and roughness. In addition, the number of crystallites per unit area and the dislocation density were observed to be positively correlated with the hardness and roughness. This study was designed to elucidate and formalize the underlying reasons for these relationships.

The Effect of Ga Doping Concentration on the Low-Frequency Noise Characteristics and Photoresponse Properties of ZnO Nanorods-Based UV Photodetectors

This study investigates the control of Ga doping in ZnO nanorods (NRs) grown on an amorphous ZnO-seeded glass substrate through hydrothermal method. ZnO was doped with various Ga concentrations (0.25, 0.5, and 1 mM). The average lengths of the resulting NRs were approximately 2.36, 1, and 1.5 μm, respectively, and the average diameters were 123, 78, and 117 nm, respectively. In addition, Ga-doped ZnO (GZO) NR-based ultraviolet photodetectors (PDs) with a sharp cutoff at 370 nm were fabricated. With an applied voltage of 1 V, different Ga precursor solution concentrations of 0.25, 0.5, and 1 mM yielded measured device responsitivities of 2.2 × 10−2, 14.9, and 14.1 A/W, respectively. The Ga concentration can be used to control the responsivity of the fabricated PDs. Furthermore, the measured noise equivalent power of the PDs at 0.25, 0.5, and 1 mM were 1.06 × 10−9, 3.13 × 10−11, and 1.29 × 10 −10 W, respectively. The corresponding detectivities of the GZO NR PDs were measured at 1.24 × 10 10, 4.21 × 1011 W, and 1.01 × 1011 cm·Hz0.5·W −1, respectively.

Growth of AlGaAs nanostructures on crystallized Al2O3 interlayers for semiconducting nanowire growth on glass substrate

We report on the growth of nanowires and AlGaAs nanostructures on an amorphous glass substrate using the crystallization techniques of amorphous Al2O3 interlayers prepared by atomic layer deposition. On the planar Al2O3 interlayers on the glass substrates after the hydrogen annealing treatment at 975 °C in the reactor of metal–organic vapor phase epitaxy set-up, AlGaAs hexagonal nanopillars (or nanodisks) and tetrahedral nanostructures are formed in addition to AlGaAs polycrystals. Structural characterizations by X-ray diffraction analysis and transmission electron microscopy show that the growth of AlGaAs{111}A or B planes is predominant even on the glass substrates. Cross-sectional lattice images reveal that the crystallized γ-Al2O3 grains are formed in the planar Al2O3 interlayers after the hydrogen annealing treatment. We observe that the 〈111〉 direction of γ-Al2O3 crystal grains tends to be titled against the substrate surface in the crystallized Al2O3 interlayers. By using AlGaAs nanostructure buffers in combination with the crystallized Al2O3 interlayers, we realize the nanowire formation tilted on the glass substrates. No AlGaAs growth is observed on the glass substrates without any crystallized Al2O3 interlayers, nor GaAs growth on the crystallized Al2O3 interlayers on the glass substrates without any AlGaAs nanostructure buffers. It is important to introduce the AlGaAs nanostructure buffers and crystallized Al2O3 interlayers for the nanowire growth on an amorphous glass substrate.

Properties of spray deposited nanocrystalline indium selenide thin films

Metal chalcogenide and chalcopyrite thin films have attracted great deal of attention due to their exciting photoelectrical characteristics. Indium selenide thin films have been deposited by computerized chemical spray pyrolysis technique on amorphous glass substrates. The as deposited films are characterized for wide range of properties including structural, surface morphological, optical and electrical, Hall effect and thermo-electrical measurements. X-ray diffraction study revealed that indium selenide thin films are polycrystalline with hexagonal crystal structure irrespective of substrate temperature. Surface morphology and film composition have been analyzed using atomic force microscopy and energy dispersive analysis by X-rays. Nearly stoichiometric deposition of the film at 350 °C was confirmed from EDAX analysis. Optical absorption measurements show that the deposited films possess a direct band gap value of 1.78 eV. The Hall effect study reveals that the films exhibit n-type conductivity.

Morphological and structural modifications of chemically‐prepared emeraldine polyaniline and zinc oxide in PAni‐ZnO composite

AbstractIn this paper, the characteristic changes on the surface morphology and structure of both emeraldine polyaniline (PAni) and ZnO films in the chemically‐prepared PAni‐ZnO composite are presented. The PAni‐ZnO composite on amorphous glass substrate was fabricated utilizing chemical bath deposition technique. The ZnO films were first synthesized using appropriate amounts of zinc sulphate and ammonium hydroxide. Emeraldine form polyaniline films were then grown on as‐prepared ZnO films using appropriate amounts of aniline hydrochloride and ammonium peroxydisulphate. The formation of zinc hydroxychloride hexagonal‐plate structures in the composite film resulted to morphological and structural modifications of PAni and ZnO composite films. The highly‐crystalline emeraldine polyaniline became amorphous when deposited as part of the composite while increased tensile strain was observed for ZnO in the composite due to stretching‐effect caused by zinc hydroxychloride along the outward‐planar direction. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of post-deposition heat treatment on optical properties derived from UV–vis of cadmium telluride (CdTe) thin films deposited on amorphous substrate

In this work, we report on post-deposition heat treatment (annealing)-induced change in optical properties derived from UV–vis study of CdTe thin films prepared on amorphous glass substrate by electron beam evaporation technique. Annealing effect gives rise to the enhancement in crystalline nature (zinc blende structure) of CdTe films with (111) preferred orientation. The average transmittance was increased with the annealing temperature and the slight shift in transmission threshold towards higher wavelength region revealed the systematic reduction in optical energy band gap. The existence of shallow level just below the conduction band, within the band gap was identified in the range of 0.23 and 0.14eV for the films annealed at 200 and 450°C, respectively. The optical quality of deposited films was confirmed by the photoluminescence study. In addition, the scanning electron microscopic measurement supports the result of X-ray diffraction study. The Swanepoel, Hervé-Vandamme, and Wemple−DiDomenico models have been employed to evaluate the various optical parameters of CdTe films. These results are correlated well with other physical properties and discussed with the possible concepts underlying the phenomena.

Semiconducting properties of aluminum-doped ZnO thin films grown by spray pyrolysis technique

Highly transparent and preferential c-axis oriented nanocrystalline undoped and Al doped zinc oxide (AZO) thin films have been deposited onto amorphous glass substrate by spray pyrolysis. The XRD studies reveal that AZO with a hexagonal (wurtzite) crystal structure having (002) preferred orientation is formed. The atomic force microscope (AFM) shows uniform surface topography. The optical band gap values of undoped and AZO thin films were changed from 3.34 to 3.35 eV. The band gap energy and photoluminescence are found to depend on the Al doping. Thermoelectric power measurement shows film having n-type in nature. Dielectric constant and loss (tan δ) were found to be frequency dependent. Interparticle interactions in the deposited films are studied by complex impendence spectroscopy.

Microstructure and magnetic properties of (0 01) textured L10 FePt films on amorphous glass substrate

L10 FePt thin films with an island-like morphology and magnetic perpendicular anisotropy were grown at low temperature (300<Tdep<375°C) by magnetron sputtering on Hoya glass substrates using a 30-nm thick Cr (200) underlayer. An MgO buffer layer with a thickness of 2nm was used to inhibit the diffusion from the Cr underlayer and promote the growth of (001) oriented L10 FePt films by inducing an in-plane lattice distortion. By varying the substrate temperature and the Ar sputter pressure (3.5<PAr<15mTorr) during the deposition, the degree of chemical order, the microstructure and the magnetic properties were tuned and the best properties in term of squareness ratio (Mr/Ms∼0.95) and coercive field (Hc∼14kOe) were observed for films deposited at Tdep=350°C and PAr=5mTorr, due to the appearance of a tensile strain, which favors the perpendicular anisotropy. The analysis of the angular dependence of remanent magnetization curves on the optimized sample suggests that the magnetization reversal is highly incoherent due to the inter-island interactions. Our results provide useful information on the low temperature growth of FePt films with perpendicular anisotropy onto glass substrates, which are relevant for a variety of technological applications, such as magnetic recording and spintronic devices.

Wavefront correction in the extreme ultraviolet wavelength range using piezoelectric thin films.

A new scheme for wavefront correction in the extreme ultraviolet wavelength range is presented. The central feature of the scheme is the successful growth of crystalline piezoelectric thin films with the desired orientation on an amorphous glass substrate. The piezoelectric films show a high piezoelectric coefficient of 250 pm/V. Using wavefront calculations we show that the grown films would enable high-quality wavefront correction, based on a stroke of 25 nm, with voltages that are well below the electrical breakdown limit of the piezoelectric film.

Effects of elastic strain and diffusion-limited aggregation on morphological instabilities in sputtered nitride thin films

Abstract

Piezoelectric Transducers on Curved Dispersive Bending Wave and Poke-Charged Touch Screens

Ferroelectric thin films of lead zirconate titanate Pb(Zr0.52,Ti0.48)O3(PZT) and bismuth titanate Bi4Ti3O12(BiT) were prepared by photochemical metal-organic deposition as electromechanical transducers used in optoelectronic devices. Both solutions were deposited on flat and convex amorphous glass substrates to poke-charge the device or detect the touch point coordinate on new generation of free-shaped screens. The effects of optimization on UV exposure, precursor type and annealing temperature (600–800 °C) were investigated on microstructural, optical and ferroelectric properties of deposited thin films. Suppressing the non-uniformity of the film thicknesses due to repetitive deposition, actually there is no structural difference between the two types of substrates and their effects on the film properties. Polarization-voltage hysteresis loops showed relatively larger remnant polarization of P r = 9.3 µC/cm2 and 6.1 µC/cm2 for optimized UV-irradiated PZT and BiT thin films, respectively, than uncured samples.