Growth of AgInSe2 thin films

Bulk AgInSe₂ was prepared by melting the constituent elements in stoichiometric pro proportions. Thin films were then grown from the bulk by a flash evaporation technique. X-ray diffraction studies were carried out on both the bulk material and the thin films. The data obtained were compared with data reported in the literature. The effect of the substrate temperature on the orientation of the films was also studied by electron diffraction. It was found that polycrystalline films of AgInSe₂ can be grown in the temperature range 150–250 °C.     

Growth of FeSb2 thin films by magnetron sputtering

The detailed growth of FeSb₂ films formed on quartz (0001) substrates by magnetron sputtering is reported. FeSb₂ films with different orientations and compositions can be produced by adjusting the Ar working gas pressure and the substrate temperature. By employing FeSb₂ thin layers produced at different substrate temperatures as templates, < 101>-, < 120>- and < 002>-textured FeSb₂ films were produced under identical growth conditions. The thermoelectric properties of film samples grown at different temperatures were measured and the effects of Sb and FeSb impurities were investigated.     

Growth and electrical properties of AgGaS2 thin films

Polycrystalline and amorphous thin films of AgGaS₂ were grown by flash evaporation for the first time. From a detailed investigation of the growthconditions it was possible to derive the first so-called structural phase diagram of a ternary chalcopyrite compound. In addition, the crystallization behaviour of amorphous films in a second heat treatment step was studied extensively. The crystal structures and chemical composition were analysed by X-ray diffraction, thermogravimetry and atomic absorption spectroscopy. The films were characterized by electrical and photo-electrical measurements.     

Growth and properties of well-oriented In2Te3 thin films

Well-oriented thin films of In₂Te₃ were grown on sapphire substrates by thermal evaporation at 350°C and were then annealed in an argon atmosphere at 400°C for 2 h. Studies of the d.c. conductivity and Hall effect for these films were carried out in the temperature range 77–295 K. The variation in the Hall mobility with temperature indicated that there is a considerable contribution from lattice scattering above 220 K.     

Growth of Cu2ZnSnS4 thin films using sulfurization of stacked metallic films

We fabricated Cu₂ZnSnS₄ (CZTS) thin films through sulfurization of stacked metallic films. Three types of Cu-Zn-Sn metallic films, i.e., Cu-rich, Cu-correct and Cu-poor precursor films were sputtered onto Mo-coated glass. The sulfurization of stacked Cu-Zn-Sn alloy films was performed at a relatively high temperature, 570 °C, with S-powder evaporation. CZTS films from Cu-rich and Cu-correct precursors showed a Cu_2 − xS phase on the film surface, while CZTS films from Cu-poor precursors didn't show the Cu_2 − xS phase. However, all films didn't exhibit any extra secondary phase and exhibited good crystalline textures even with Cu-ratio differences in metallic precursor films. Fabricated CZTS films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman scattering measurements. SEM cross-section images of CZTS films showed that Cu-poor CZTS films were grown with more smooth film surface compared with other types of CZTS films.     

Growth and Raman scattering characterization of Cu2ZnSnS4 thin films

In the present work we report the results of the growth, morphological and structural characterization of Cu₂ZnSnS₄ (CZTS) thin films prepared by sulfurization of DC magnetron sputtered Cu/Zn/Sn precursor layers. The adjustment of the thicknesses and the properties of the precursors were used to control the final composition of the films. Its properties were studied by SEM/EDS, XRD and Raman scattering. The influence of the sulfurization temperature on the morphology, composition and structure of the films has been studied. With the presented method we have been able to prepare CZTS thin films with the kesterite structure.     

Growth and structure of electron beam evaporated V2O5 thin films

The growth, structure and room temperature electrical conductivity of electron beam evaporated V₂O₅ thin films were studied in detail as a function of deposition temperature. The films deposited at T_s≈553 K and subsequently annealed in oxygen atmosphere at 693 K exhibited orthorhombic layered structure.     

Growth of crystalline HgCr2S4 thin films at mild reaction conditions

Thin films of crystalline HgCr₂S₄ have been deposited on glass substrates at low temperature as low as 65 °C using a chemical bath deposition method. Typical thickness of the deposited HgCr₂S₄ thin films was 264 nm.The films were composed of closely packed irregular grains of 165-175 nm in diameter. The X-ray diffraction analysis and the selected area electron diffraction analysis revealed the deposited thin films were polycrystalline with highly (2 2 0) preferential orientation. The films exhibit a pure faint black. Their direct band gap energy was 2.39 eV with room temperature electrical resistivity of the order of 10⁻³ Ω cm.     

Optical characterization of HfO2 thin films

Hafnia films prepared onto silicon wafers at three substrate temperatures of 40, 160 and 280 °C are optically characterized utilizing the multi-sample method. The characterization uses the combination of variable angle spectroscopic ellipsometry and spectroscopic reflectometry within the spectral region 1.24-6.5 eV (190-1000 nm). The structural model of the HfO₂ films includes boundary nanometric roughness, thickness non-uniformity and refractive index profile. Spectral dependences of the film optical constants are expressed using a recently developed parametrized joint density of states model describing the dielectric response of both interband transitions and excitations of localized states below the band gap. It is shown that the observed weak absorption below the band gap does not correspond to the Urbach tail.     

One-step electrodeposition of CuGaSe2 thin films

CuGaSe₂ thin films have been prepared by one-step electrodeposition and rapid thermal annealing process. According to composition and morphology analysis, deposition potential of − 0.6 V vs. SCE is considered to be optimum for electrodeposition. From the X-ray diffraction and Raman studies, the as-deposited film exhibits poor crystallinity without the evidence of CuGaSe₂ or other Ga-containing phases, while the rapid thermal annealing-treated film shows chalcopyrite structure CuGaSe₂ phase containing MoSe₂ phase between the Mo substrate and the absorber and minor second phase Cu_2 − xSe. The obtained CuGaSe₂ thin film has a band gap of about 1.68 eV and p-type conductivity.     

Spectroellipsometric assessment of HfO2 thin films

Present paper looks into the possibilities and limitations of near ultraviolet-visible range spectroscopic ellipsometry in investigating HfO₂ thin films (thickness < 7 nm). The “high k” dielectric films were produced by Atomic Layer Deposition—ALD, sputtering, and Metalo-Organic Chemical Vapour Deposition—MOCVD, on silicon and on silicon/silicon dioxide structures. Using a simple optical model (Cauchy dispersion, with an Urbach absorption tail), suitable for the optical range investigated, we extract the thickness of the layers and their optical constants. Results related to the optical properties show the important impact made by the initial surface and the growth/deposition procedure. It is also shown that for the case of ALD HfO₂ films grown on RTO oxides a significant increase in the absorption coefficient is recorded in the 4.7-5.15 eV range; this can be linked with the formation of defects related to oxygen vacancies. Subsequent anneal cycles performed in oxygen reveal that changes do occur both at the transition layer level, and in the structure of the HfO₂ film, for which an increase in the absorption is recorded.     

Electrodeposition of As2Se3 thin films

Semiconducting As₂Se₃ thin films have been prepared from an aqueous bath at room temperature onto stainless steel and fluorine-doped tin oxide (F.T.O.)-coated glass substrates using an electrodeposition technique. It has been found that As₂O₃ and SeO₂ in the volumetric proportion as 4:6 and their equimolar solutions of 0.075 M concentration forms good quality films of As₂Se₃. The films are annealed in a nitrogen atmosphere at temperature of 200 °C for 2 h. The films are characterised by scanning electron microscopy, X-ray diffraction and optical absorption techniques. Studies reveal that asdeposited and annealed thin films are polycrystalline in nature. The optical band gap has been found to be 2.15 eV for the above-mentioned composition and concentration of the film.     

Growth and characterization of WS2 thin films deposited by dip method

Tungsten disulphide has been grown by dip technique on glass substrate using sodium tungstate and thiourea as sources of tungsten and sulphide ion respectively. X-ray diffraction of as deposited thin film indicated polycrystalline character with rhombohedral phase. Optical study shows a direct band gap nature with band gap energy 1.4 eV. Conductivity measurement showed a semiconductor-type temperature dependence characterized by activation energy 0.659 eV.     

Growth of RuO2 thin films by liquid injection atomic layer deposition

We have grown RuO₂ films by pulsed liquid injection atomic layer deposition using (Ru(thd)₂(cod)) dissolved in pyridine. The deposition process took place at 290 °C and consisted of four steps. The films exhibited smooth surface. Analysis of the films using secondary ion mass spectroscopy (SIMS) revealed low content of carbon in the films. Resistivity of the RuO₂ film at room temperature was about 160 µΩ cm.     

Photoconductivity effects in CuInS2, CuInSe2 and CuInTe2 thin films

Photoconductivity response spectra for CuInS₂, CuInSe₂ and CuInTe₂ thin films are reported. The temperature dependences of the spectra are utilized to determine the bandgap energies as functions of temperature. Photoconductive response times are measured for these I–III–VI₂ ternary semiconductors and are discussed in terms of deposition parameters and post-deposition treatments. The photoconductive decay times are in the range 10^-3 – 10¹ ms.     

TiO2 thin films for dyes photodegradation

The aim of the present study is to investigate the influence of the TiO₂ specific surface (powder, film) on the photocatalytic degradation of methyl orange. Porous TiO₂ films were deposited on transparent conducting oxide substrates by spray pyrolysis deposition. The films were characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy, and the UV-Vis spectroscopy. The XRD spectra of nanoporous TiO₂ films revealed an anatase, crystalline structure that is known as the most suitable structure in photocatalysis. The average thickness of the films was 260 nm and the measured band gap is 3.44 eV. The influence of the operational parameters (dye concentration, contact time) on the degradation rate of the dye on TiO₂ was examined. There were calculated the kinetic parameters and the process efficiency. Using thin films of TiO₂ is technologically recommended but raises problems due to lowering the amount of catalyst available for the dye degradation.     

CuGaSe2 thin films for photovoltaic applications

Of the I-III-VI₂ group chalcopyrites, CuInSe₂ has already proved its suitability for thin film solar cells owing to its excellent optical and transport properties. CuGaSe₂ is expected to exhibit comparable properties from this point of view. With its band gap of 1.7 eV it is a candidate for use in photovoltaic tandem systems.

The preparation of CuGaSe₂ thin films by means of the vacuum evaporation of the constituent elements (four-temperature method) is described. The structural, electrical and optical properties of these films were investigated. Secondary electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction examination and measurements of the optical transmission, resistivity and thermoelectric power were used to determine the film properties relative to the preparation parameters and stoichiometry. The growth conditions were optimized for solar cell applications. Heterojunctions were prepared by the in situ evaporation of Zn_xCd_1−xS onto the CuGaSe₂ films. The characteristic data of the cells are a short-circuit current of 6 mA and an open-circuit voltage of 620 mV at an illumination at air mass 1.5 on an area of 1 cm².     

Growth of Cu2SnS3 thin films by solid reaction under sulphur atmosphere

Cu₂SnS₃ thin film have been synthesized by solid state reaction under vapour sulphur pressure at 530 °C, during 6 h, via a sequentially deposited copper and tin layers Cu/Sn/Cu…Sn/Cu/Sn. The structure and the composition were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA). X-ray diffraction revealed that as the deposited film crystallizes in the cubic structure and the crystallites exhibit preferential 111 orientation of the grains. Moreover, EPMA analysis confirmed that the obtained film is stoichiometric. The SEM study shows the presence of spherical particles of ≈100-120 nm diameters. The optical absorption coefficient and band gap of the film were estimated by means of transmission and reflection optical measurements at room temperature. A relatively high absorption coefficient in the range of 10⁴ cm⁻¹ was indeed obtained and the band gap value is of the order of 1.1 eV. On the other hand, the electrical conductivity of Cu₂SnS₃ film prepared in the present experiment is suitable for fabricating a thin film solar cell based on not cheaper and environmental friendly material.     

A study of textured non-stoichiometric MoTe2 thin films used as substrates for textured stoichiometric MoS2 thin films

Textured MoTe₂ films have been prepared by sequential evaporation of the constituents followed by annealing under a tellurium pressure. The films are systematically textured with the c-axis of the crystallites perpendicular to the plane of substrate, however, the film composition is difficult to control and even after process optimization the films are tellurium deficient. This is thought to be caused by the electro negativity difference of the constituents.The textured MoTe₂ films have been used as substrates on which to grow MoS₂ films by annealing under a pressure of sulfur that allows textured MoS₂ films to be grown with good crystalline properties. The presence of sulfur at the surface and annealing under dynamic vacuum is important for this process and moreover, suppresses the superficial oxidation of the Mo and Te constituents.     

Preparation and super-hydrophilic properties of TiO2/SnO2 composite thin films

SnO₂-TiO₂ composite thin films were fabricated on soda-lime glass with sol-gel technology. By measuring the contact angle of the film surface and the degradation of methyl orange, we studied the influence of SnO₂ doping concentration, heat-treatment temperature and film thickness on the super-hydrophilicity and photocatalytic activity of the composite films. The results indicate that the doping of SnO₂ into TiO₂ can improve their hydrophilicity and photocatalytic activity, and the composite film with 1-5 mol% SnO₂ and heat-treated at 450°C is of super-hydrophilicity. The optimal SnO₂ concentration for the photocatalytic activity is 10 mol% and larger film thickness is helpful to reduce the contact angle of the composite films.