Search results for "Thin"
showing 10 items of 3618 documents
Outstanding nonlinear optical properties of methylammonium- and Cs-PbX3 (X = Br, I, and Br–I) perovskites: Polycrystalline thin films and nanoparticl…
2019
Metal Halide Perovskites (MHPs) have arisen as promising materials to construct cost-effective photovoltaic and light emission devices. The study of nonlinear optical properties of MHPs is necessary to get similar success in nonlinear photonic devices, which is practically absent in the literature. The determination of the third order nonlinear coefficients is typically done by the Z-scan technique, which is limited by the scattering of polycrystalline thin films. In this work, we have studied nonlinear optical properties of polycrystalline CH3NH3PbX3 (MAPbX3) thin films and colloidal CsPbX3 nanoparticles with three different bandgaps (X3 = I3, Br3, and Br1.5I1.5). Their bright generation o…
Rhodamine (B) photocatalysis under solar light on high crystalline ZnO films grown by home-made DC sputtering
2018
Abstract ZnO thin films were deposited by home-made DC sputtering of zinc target under mixed gases (Argon, Oxygen) plasma on glass substrates. Films were deposited by varying oxygen partial pressure (PO2) from 0.09 to 1.3 mbar in the deposition chamber, at a fixed substrate temperature of 100 °C. The samples were characterized by photoluminescence (PL), X-ray diffraction (XRD), optical transmissions (UV–vis), scanning electron microscopy (SEM) and electrical (Hall effect) measurements. The results indicate that by varying the oxygen pressure in the deposition chamber, the films show a precise and well defined photoluminescence emissions for each range of pressure covering almost the entire …
X-Ray studies on optical and structural properties of ZnO nanostructured thin films
2006
Abstract X-ray absorption near-edge fine structure (XANES) studies have been carried out on nanostructured ZnO thin films prepared by atmospheric pressure chemical vapour deposition (APCVD). Films have been characterized by X-ray diffraction (XRD) and optical luminescence spectroscopy exciting with laser light (PL) or X-ray (XEOL). According to XRD measurements, all the APCVD samples reveal a highly (002) oriented crystalline structure. The samples have different thickness (less than 1 μm) and show significant shifts of the PL and XEOL bands in the visible region. Zn K-edge XANES spectra were recorded using synchrotron radiation at BM08 of ESRF (France), by detecting photoluminescence yield…
Epitaxial growth of perovskite oxide films facilitated by oxygen vacancies
2021
The authors would like to thank P. Yudin for valuable discussions, N. Nepomniashchaia for VASE studies, and S. Cichon for XPS analysis. The authors acknowledge support from the Czech Science Foundation (Grant No. 19-09671S), the European Structural and Investment Funds and the Ministry of Education, Youth and Sports of the Czech Republic through Programme ‘‘Research, Development and Education’’ (Project No. SOLID21 CZ.02.1.01/0.0/0.0/16-019/0000760), and ERA NET project Sun2Chem (E. K. and L. R.). Calculations have been done on the LASC Cluster in the ISSP UL.
Fabrication and characterization of low cost Cu 2 O/ZnO:Al solar cells for sustainable photovoltaics with earth abundant materials
2016
Abstract The low cost electrodeposition method was used to grow Cu2O thin films and experimentally determine the optimal absorber layer thickness. Raman scattering studies indicate the presence of solely crystalline Cu2O and SEM images show that the thin films consist of grains with a pyramidal shape. The influence of the thickness of the light absorbing Cu2O layer on the basic characteristic of the heterojunction and their properties have been investigated using reflectivity, current–voltage (J–V), capacitance–voltage (C–V) and the external quantum efficiency (EQE) measurements. The depletion layer, the charge collection length of the minority carrier, and reflectivity are the main factors…
Thermal stability of magnetic characteristics of Co/Ag/Fe and Co/Ag/Fe20Ni80 spin-valve structures
2017
Abstract We investigated the thermal stability of magnetic characteristics of Co/Ag/Fe and Co/Ag/Fe 20 Ni 80 spin-valve structures. Thin film systems were obtained with the help of sputtering method. For the first type of systems two particular thicknesses ( d ML = 3 and 20 nm) and different disposition of magnetic layers (ML) were used. For the second type different thickness of Ag ( d NML ) spacer layer was used. The research of the crystal structure was performed with the transmission electron microscope. The results demonstrate that every investigated as-deposited sample does not include solid solutions, intermetallic compounds or impurities. It has been found that among the spin-valve…
Band gap of corundumlike α−Ga2O3 determined by absorption and ellipsometry
2017
The electronic structure near the band gap of the corundumlike $\ensuremath{\alpha}$ phase of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400--190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which y…
Reducing the Schottky barrier height at the MoSe2/Mo(110) interface in thin-film solar cells: Insights from first-principles calculations
2016
Abstract We report on first-principles calculations of the properties of the MoSe2/Mo(110) interface. Due to mismatch between the lattice parameters of the two structures, different patterns can form at the interface. We have studied the formation energy and the band alignment of six patterns for the MoSe2 (0001)/Mo(110) interface and one pattern for the MoSe2 (11 2 0)/Mo(110) interface. The MoSe2 (11 2 0)/Mo(110) interface is more stable than the MoSe 2 (0001)/Mo(110) interface and in contrast to MoSe2 (0001)/Mo(110), no Schottky barrier forms at MoSe2 (11 2 0)/Mo(110). Doping with Na modifies the band alignment at the interfaces. The Schottky barrier height decreases, provided that a Na a…
Determination of refractive index of submicron-thick films using resonance shift in a four-layer slab waveguide
2017
The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide la…
Evaluation and Comparison of Novel Precursors for Atomic Layer Deposition of Nb2O5 Thin Films
2012
Atomic layer deposition (ALD) of Nb2O5 thin films was studied using three novel precursors, namely, tBuN═Nb(NEt2)3, tBuN═Nb(NMeEt)3, and tamylN═Nb(OtBu)3. These precursors are liquid at room temperature, present good volatility, and are reactive toward both water and ozone as the oxygen sources. The deposition temperature was varied from 150 to 375 °C. ALD-type saturative growth modes were confirmed at 275 °C for tBuN═Nb(NEt2)3 and tBuN═Nb(NMeEt)3 together with both oxygen sources. Constant growth rate was observed between a temperature regions of 150 and 325 °C. By contrast, amylN═Nb(OtBu)3 exhibited limited thermal stability and thus a saturative growth mode was not achieved. All films we…