Synthesis of Cu<Subscript>2</Subscript>ZnSn(S<Subscript>x</Subscript>Se<Subscript>1−x</Subscript>)<Subscript>4</Subscript> thin films directly on transparent conductive glass substrates by solvothermal method

In this paper, the single-step solvothermal method was proposed to grow directly Cu₂ZnSn (S_xSe_1?x)₄ (CZTSSe) thin films on FTO substrates. The composition ‘x’ was varied by changing the molar ratios of thiourea to selenourea in the precursor solutions. The effects of the molar ratios of thiourea to selenourea on the structure, morphology and optical properties of CZTSSe thin films were investigated by X-ray diffraction, Raman spectroscopy, scanning electronic microscopy, energy dispersive spectrometry and UV–Vis spectrophotometry. The results indicated that CZTSSe thin films are composed of a large number of uniform sphere-like particles, and the diameter of particles varies from 600 to 280 nm when the molar ratios is changed from 1 to 0. The major XRD diffraction peaks shift towards lower diffraction angles, the Raman peak position of A1 mode of CZTSSe thin films moves consecutively towards the lower frequency due to the S replacement by Se. CZTS and CZTSe thin films are single kesterite structure, however, CZTSSe thin films are mixture structure of kesterite and wurtzite. By varying the molar ratios of thiourea to selenourea in the precursor solution, the atom ratios of S/Se in CZTSSe NCs thin films can be well controlled over the whole range, resulting in tunable optical band gap from 1.54 to 1.38 eV.     

Optical and photoelectric properties of α-Dy<Subscript>2</Subscript>S<Subscript>3</Subscript> and α-Dy<Subscript>2</Subscript>S<Subscript>3</Subscript>〈Pb〉 films

A process is described for the growth of thin crystalline α-Dy₂S₃ films by thermal evaporation from separate dysprosium and sulfur sources. The films were doped with Pb, and their reflection and transmission spectra were measured at room temperature and photon energies in the range (0.3−5.2) × 10⁻¹⁹ J. The α-Dy₂S₃ films were shown to have an exponential absorption edge. The photoconductivity of the doped films was measured at photon energies in the range (0.3−5.2) × 10⁻¹⁹ J and temperatures from 115 to 400 K.     

The optical and electrical transport studies of Zn<Subscript>x</Subscript>Co<Subscript>1−x</Subscript>S thin films

In an attempt to design and fabricate a suitable II–VI group material of variable optical gap, we have synthesized a series of Zn_xCo_1?xS (0 ≤ x ≤ 0.4) thin films via a facile chemical solution growth technique. To gain insight of the materials properties we have opted for different characterization techniques and are reporting our observations pertaining to the elemental analysis, magneto-topography, optical and electrical transport studies. Excellent agreement of binding energy values for Co2p, Zn2p and S2p levels in elemental analysis concluded the oxidation states as Co²⁺, Zn²⁺ and S^2?. Magnetic force microscopy confirmed the existence of randomly distributed magnetic domains mimicking the surface topography. The optical studies determined the high absorption coefficient (α ≈ 10⁴ to 10⁵ cm^?1) in the as-grown thin films. The optical band gap is found to be increased non-linearly from 1.59 to 2.50 eV as the composition parameter (x) is increased. The D.C. electrical conductivity measurements showed decrease in conductivity with increased composition parameter (x). The thermoelectric studies confirmed degenerative nature of the as-deposited thin films with n-type conduction.     

Structural and electrical studies of Cd<Subscript>1−x</Subscript>Zn<Subscript>x</Subscript> Te thin film by vacuum evaporation technique

Cd_1−xZn_xTe (where x = 0.02, 0.04, 0.06, 0.08) thin film have been deposited on glass substrate at room temperature by thermal evaporation technique in a vacuum at 2 × 10⁻⁵ torr. The structural analysis of the films has been investigated using X-ray diffraction technique. The scanning electron microscopy has been employed to know the morphology behaviour of the thin films. The temperature dependence of DC electrical conductivity has been studied. In low temperature range the thermal activation energy corresponding to the grain boundary—limited conduction are found to be in the range of 38–48 μeV, but in the high temperature range the activation energy varies between 86 and 1.01 meV. The built in voltage, the width of the depletion region and the operating conduction mechanism have been determined from dark current voltage (I–V) and capacitor-voltage (C–V) characteristics of Cd_1−xZn_xTe thin films.     

Effect of gamma radiation on electrical and optical properties of (TeO<Subscript>2</Subscript>)<Subscript>0·9</Subscript> (In<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>0·1</Subscript> thin films

We have studied in detail the gamma radiation induced changes in the electrical properties of the (TeO₂)_0·9 (In₂O₃)_0·1 thin films of different thicknesses, prepared by thermal evaporation in vacuum. The current–voltage characteristics for the as-deposited and exposed thin films were analysed to obtain current versus dose plots at different applied voltages. These plots clearly show that the current increases quite linearly with the radiation dose over a wide range and that the range of doses is higher for the thicker films. Beyond certain dose (a quantity dependent on the film thickness), however, the current has been observed to decrease. In order to understand the dose dependence of the current, we analysed the optical absorption spectra for the as-deposited and exposed thin films to obtain the dose dependences of the optical bandgap and energy width of band tails of the localized states. The increase of the current with the gamma radiation dose may be attributed partly to the healing effect and partly to the lowering of the optical bandgap. Attempts are on to understand the decrease in the current at higher doses. Employing dose dependence of the current, some real-time gamma radiation dosimeters have been prepared, which have been found to possess sensitivity in the range 5–55 μGy/μA/cm². These values are far superior to any presently available real-time gamma radiation dosimeter.     

Effect of deposition ambient on structural and optical properties of Mg<Subscript>x</Subscript>Zn<Subscript>1−x</Subscript>O alloy thin films grown by RF sputtering

Mg_xZn_1−xO thin films were deposited on Corning eagle 2,000 glass substrates by a RF magnetron sputtering using a ceramic target. The effect of Ar/O₂ ratios on structural and optical properties was investigated. The XRD results showed that the film demonstrated the best structural properties when the Ar/O₂ ratio equal 7:3. Sputtering ambient seemed to have minor effect on the optical properties of Mg_xZn_1−xO thin films.     

Compositional effect on optical characteristics of solution grown (Cd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)S thin films

A good deal of information regarding the synthesis and optical properties of chemically grown (Cd_1?x Sn _x )S (x = 0.01–0.40) thin film has been reported. The growth of these films depends on various preparative parameters and deposition conditions. The reactant concentration, pH, deposition temperature, and rate of agitation were found to influence significantly the quality and thickness of the films. The photoconductive studies have been done with the help of rise and decay curves. Lifetime, mobility, and trap depth are calculated for observed parameters. Band gap measurements for the prepared films have been done with the help of optical transmission spectra using UV-VIS-IR spectrophotometer (190–1100 Å). Interesting results of PC rise and decay studies, optical absorption, and transmission spectra have been presented and discussed. Mobility is influenced significantly by Sn composition. The action spectra showed displacement in the absorption edge towards lower energy side by the addition of Sn mole content. The energy gap decreased from 2.1 to 1.9 eV for x = 0.01 and 1.85 eV for x = 0.02.     

Microstructure,dielectric and photoluminescence properties of Tm-doped Ba<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>TiO<Subscript>3 </Subscript>thin films fabricated by sol–gel method

Ba_0.8Sr_0.2TiO₃ thin films doped by Tm from 0 to 7 mol% were fabricated by sol–gel method on silicon and Pt/Ti/SiO₂/Si substrates. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy have been used to study variations of crystal structure, surface morphologies, and phase stability of Tm-doped BST films, respectively. The residual stress in BST films on silicon substrates can be reduced by Tm doping, as demonstrated by the blueshift of phonon peaks in Raman spectra. The dielectric measurements were conducted on metal-insulator-metal capacitors at the frequency from 1 kHz to 1 MHz. The grain size and dielectric constant decreased with increasing Tm concentration. While the variation of dielectric loss, tunability and the figure of merit were nonlinear with increasing Tm concentration. In addition, the photoluminescence property of 0.2 mol% Tm-doped BST was also studied. The effect of Tm doping on the microstructure, dielectric and photoluminescence properties were analyzed.     

Oriented In<Subscript>3–<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>4</Subscript> films on the (100) surface of Si,GaAs, and InP single crystals

Spray pyrolysis of aqueous solutions, with thiourea as a sulfurizing agent, has been used to grow cubic indium sulfide films on single-crystal substrates: In_3–x S₄(111)/Si(100), In_3–x S₄(111)/GaAs(100), and In_3–x S₄(111)/InP(100). The lattice parameter a of the sulfide has been shown to increase with an increase in the lattice parameter of the substrate, whereas the film grown on GaAs has the highest lattice strain (as assessed from X-ray diffraction line broadening). The films have a constant phase composition and (111) texture, in contrast to films grown on glassy substrates by the same method.     

Characterization and electrical conductivity of La<Subscript>1−x</Subscript>Sr<Subscript>x</Subscript>CrO<Subscript>3</Subscript> NTC ceramics

The La_1?xSr_xCrO₃ (x?=?0–0.1) negative temperature coefficient (NTC) ceramics have been prepared by the traditional solid state reaction method. X-ray diffraction (XRD) analysis has revealed that the as-sintered ceramics crystallize in a single perovskite structure. Scanning Electron Microscope (SEM) images show that the doped Sr²⁺ contributes to in the decrease in porosity. X-ray photoelectron spectroscopy (XPS) analysis indicates the existence of Cr³⁺ and Cr⁶⁺ ions on lattice sites, which result in hopping conduction. The presence of the Cr⁶⁺ is one of the key factors that affect the electrical conductivity of La_1?xSr_xCrO₃. Resistance–temperature characteristics were studied in the range of ?80 to 10?°C for the ceramic samples, the electrical characterizations show that the electrical resistivity and material constant B decrease with the increase of the strontium content.     

Comparative study of multilayered ZnO/TiO<Subscript>2</Subscript>/ZnO and TiO<Subscript>2</Subscript>/ZnO/TiO<Subscript>2</Subscript> thin films prepared by sol–gel dip coating method

The aim of this research work is to represent the comparative study of ZnO/TiO₂/ZnO (ZTZ) and TiO₂/ZnO/TiO₂ (TZT) thin films deposited by sol–gel dip coating on FTO substrates. After deposition, the films were annealed at 500 °C for 1 h. Structural, surface morphology, optical and electrical properties of these films were studied by X-ray diffractrometer (XRD), Raman spectra, atomic force microscope (AFM), photoluminescence spectra (PL) and four point probe technique respectively. XRD and Raman spectra confirmed the anatase, brookite phases of TiO₂ and cubic phase of ZnO. AFM confirmed the formation of nano particles with average sizes of 18.4 and 47.2 nm of TZT and ZTZ films respectively. According to PL spectra, both the multilayer films slowdown the electron hole recombination rate and enhances the optoelectronic properties of the materials. Also it showed the peaks in the visible region of spectrum. The four point probe results showed that the average sheet resistivity of the films is 450 and 120 (ohm-m) respectively.     

Modulation of microstructure and interface properties of co-sputter derived Hf<Subscript>1−x</Subscript>Ti<Subscript>x</Subscript>O<Subscript>2</Subscript> thin films with various Ti content

Hf_1?xTi_xO₂ dielectric thin films were deposited on Si (100) substrates by RF reactive co-sputtering with the variation in RF power of Ti target. The compositional, morphological, structural and optical properties of Hf_1?xTi_xO₂ films with various Ti concentration were systematically investigated by X-ray photoelectron spectroscopy (XPS), Field emmission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectroscopy techniques respectively. The electrical properties of the co-sputtered thin films were studied by capacitance–voltage and current density–voltage measurements. The XRD study has shown the enhancement in the the crystalline property of Hf_1?xTi_xO₂ film up to 60 W of Ti target power and amorphous like behaviour was observed for higher RF power. The Ti content in Hf_1?xTi_xO₂ was calculated from the XPS measurements, where the Ti content was found to be increased with rise in RF power. FESEM micrographs depict the increase in grain size upto the RF power 60 W. The Raman spectrum of the Hf_1?xTi_xO₂ film has shown that the major generated phase was titanium-substituted monoclinic phase of HfO₂. The flatband voltage (V_fb) and oxide charge density (Q_ox) were extracted from the high frequency (1 MHz) C–V curve. The D_it has a minimum value for the film deposited at 60 W RF power of Ti target. The leakage current density of the Hf_1?xTi_xO₂ films was found to be minimum for the RF power 60 W.     

Structural,optical and electrical properties of ZnTe<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Se<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript> thin films

ZnTe_1−x Se _x films were deposited on glass substrates kept at 200 °C by the electron beam evaporation technique. These films exhibited cubic structure and the lattice parameter increased with increase of Tellurium concentration in the films which confirmed the solid solution formation. The grain size is found to increase with Te content. The dislocation density and lattice strain show a decreasing trend with increasing of Te content. Band gap values of 2.73 eV, 2.63 eV, 2.52 eV and 2.41 eV have been calculated for the films of composition ‘x’ = 0.2, 0.4, 0.6 and 0.8, respectively, which confirmed the formation of solid solution between ZnSe and ZnTe. Refractive index of the films increased from 2.535 to 2.826 as the concentration of Te increased. All the films showed high resistivity values. Laser Raman spectral studies of ZnTe_1−x Se _x revealed LO phonon frequencies whose values are located in between the LO phonon frequencies of ZnSe and ZnTe.     

Crystal growth,X-ray diffraction characterization,and Mössbauer spectroscopy of FeIn<Subscript>2</Subscript>S<Subscript>4</Subscript>-In<Subscript>2</Subscript>S<Subscript>3</Subscript> solid solutions

Crystals of (FeIn₂S₄)_{1 ? x} (In₂S₃) _x solid solutions consisting of large blocks have been grown by directional solidification (horizontal Bridgman process). FeIn₂S₄, In₂S₃, and the solid solutions are shown to crystallize in the spinel structure. The composition dependence of their unit-cell parameter a follows Vegard's law. The local states of the Fe ions in the solid solutions have been studied by Mössbauer spectroscopy in a transmission geometry.     

Supercapacitive performance of hydrous ruthenium oxide (RuO<Subscript>2</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O) thin films deposited by SILAR method

The amorphous hydrous ruthenium oxide (RuO₂·nH₂O) thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. These films were characterized for their structural, surface morphological, and compositional study by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDAX) techniques. The wettability test was carried out by measuring the water contact angle. The scanning electron microscopy study showed small RuO₂ particles are grouped together to form porous agglomerates. The FT-IR study confirmed the formation of hydrous ruthenium oxide films. The hydrophilic nature of ruthenium oxide (RuO₂·nH₂O) thin films was observed from water contact angle measurement. The presence of Ru and O in the film was confirmed by EDAX analysis. The supercapacitor behavior of these films studied in 0.5 M H₂SO₄ electrolyte showed maximum specific capacitance of 162 F g⁻¹ at 10 mV s⁻¹ scan rate. These films exhibit 80% cycling performance after 2,000 cycles. The charge–discharge studies carried at 1 mA cm⁻² current density revealed the specific power of 3.5 KW kg⁻¹ and specific energy of 29.7 W Kg⁻¹ with 93% coulombic efficiency.     

Characterization of Sn-doped BST thin films on LaNiO<Subscript>3</Subscript>–coated Si substrate

Sn-doped (Ba,Sr)TiO₃(BSTS) thin films have been deposited on highly (200) oriented LaNiO₃(LNO) thin films by sol-gel method. The atomic force microscope (AFM) images exhibited that the dopant Sn did not decrease the crystalline grain size of BST thin films. The structure of the BST film, determined by X-ray diffraction (XRD), presented the higher intensity (110) and (200) peaks, while the latter was distinctly induced by LNO layer. Evidently, Sn-doped BST thin films on LNO/Si substrate were found to decrease the dielectric constant and the dielectric loss, which is favourable to potentially improve the figures of merits (F _D ) of pyroelectric materials. The BSTS thin films on LNO layer also displayed an excellent leakage current property comparing with the BST thin film on Pt/Ti/SiO₂/Si and LNO/Si substrates.     

Optical property and crystalline quarity of Si and Ge added β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films

A transparent electrode of β-Ga₂O₃ films for solar cells, flat panel displays and other devices, which consist in chemically abundant and ecological elements of gallium and oxygen, were grown on quartz or silicon substrates by RF magnetron sputtering using a sintered Ga₂O₃ target. The impurities of Si or Ge were also added into the grown films. The polycrystalline β-Ga₂O₃ grew by the thermal annealing after RF sputtering. Optical absorption measurements indicated that the grown β-Ga₂O₃ film after 600°C annealing have a band gap of about 5 eV.     

Optical and electrical properties of Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O thin films by sol–gel method

Mg _x Zn_1−x O (0 ≤ x ≤ 0.35) thin films have been deposited by sol–gel technique and the composition related structural, electrical, and optical properties are investigated. All the films have hexagonal wurtzite structure and the separation of MgO phase occurs when x = 0.3 and 0.35. With the increase of Mg content, the densification of the films decrease and band gap values increase. The maximum band gap value reaches 3.56 eV when x = 0.15. After Mg doping the conductivities of the Mg _x Zn_1−x O films are reduced greatly and the electrical current–voltage (I–V) characteristics show nonlinearity for x > 0.15.     

(Ga<Subscript>54.59</Subscript>In<Subscript>44.66</Subscript>Er<Subscript>0.75</Subscript>)<Subscript>2</Subscript>S<Subscript>300</Subscript> single crystal: novel material for detection of γ-radiation by photoinduced nonlinear optical method

It was shown a possibility to use the (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystal as optoelectronics detectors of gamma-irradiation using photoinduced nonlinear optical methods and photoluminescence. The crystal was irradiated by a ⁶⁰Co source at ambient conditions. The average energy of the incident γ-rays was about 1.25 MeV. The luminescence excitation was carried out using a 150 mW cw laser with wavelength 532 nm. The best results sensitive to the gamma irradiation were obtained for the third harmonic generations (THG) of the materials treated by bicolor Er: glass laser two beams propagated at angles about 21°–24°. The photoinduced gratings profile also were explored and their correlation with the gamma radiation and nonlinear optical response were explored. Comparison of photoluminescence and photoinduced nonlinear optical sensitivity to radiations was performed.     

Cd(S<Subscript>(1 − <Emphasis Type="Italic">x</Emphasis>)</Subscript> + CO<Subscript>3(<Emphasis Type="Italic">x</Emphasis>)</Subscript>) thin films by chemical synthesis

A microcrystalline mixture of cadmium carbonate (CdCO₃) and cadmium sulfide (CdS) were grown in the thin film format onto glass substrates by means of chemical bath. The temperature of the bath (T_d) was selected in the interval 23–80^∘C. At low temperatures, CdCO₃ is the compound predominant in the layers. At high temperatures CdS is the compound deposited on the substrate. At intermediate T_d-values a mixture of both materials are present, i.e., the gradual transition from an insulator (CdCO₃) to a semiconductor (CdS) growth occurs when T_d increases. Physical properties of films were studied by means of X-ray diffraction and optical absorption. The forbidden energy band gap of direct electronic transitions (E_g) was calculated by applying the α² ∝ (hν − E_g) relation to the optical absorption spectra.