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Zn–In–Se thin films were fabricated on the ultrasonically cleaned glass substrates masked with clover-shaped geometry by thermal evaporation of its elemental sources. Temperature-dependent conductivity characteristics of the films were investigated under dark and illuminated conditions. The semiconductor type of the films was found as n-type by thermal probe test. According to the van der Pauw technique, the dark electrical conductivity analyses showed that the variations of conductivity of unannealed and annealed at 3 0 0 ∘ C samples are in exponential dependence of temperature. These conductivity profiles were found to be dominated by the thermionic emission at high temperature region whereas their behaviors at low temperatures were modeled by hopping theory. On the contrary, as a result of the further annealing temperatures, the surface of the samples showed semi-metallic characteristics with deviating from expected Arrhenius behavior. In addition, the temperature-dependent photoconductivity of the films was analyzed under different illumination intensities and the results were explained by the supra-linear characteristic based on the two-center recombination model. [ABSTRACT FROM AUTHOR]

ZnInSe2/Cu0.5Ag0.5InSe2 diode structures have been fabricated by thermal evaporation of stacked layers on indium tin oxide-coated glass substrates. Temperature-dependent dark current–voltage measurements were carried out to extract the diode parameters and to determine the dominant conduction mechanisms in the forward- and reverse-bias regions. The heterostructure showed three order of magnitude rectifying behavior with a barrier height of 0.72 eV and ideality factor of 2.16 at room temperature. In the high forward-bias region, the series and shunt resistances were calculated with the help of parasitic resistance relations, yielding room-temperature values of 9.54 × 102 Ω cm2 and 1.23 × 103 Ω cm2, respectively. According to the analysis of the current flow in the forward-bias region, abnormal thermionic emission due to the variation of the ideality factor with temperature and space-charge-limited current processes were determined to be the dominant conduction mechanisms in this heterostructure. In the reverse-bias region, the tunneling mechanism was found to be effective in the leakage current flow with trap density of 106 cm−3. Spectral photocurrent measurements were carried out to investigate the spectral working range of the device structure. The main photocurrent peaks observed in the spectrum corresponded to the band-edge values of the active thin-film layers. [ABSTRACT FROM AUTHOR]

This work indicates the device properties of polycrystalline p-AgGaInTe2 (AGIT) thin films deposited on bare and ITO-coated glass substrates with thermal evaporation technique. Device characteristics of n-CdS/p-AGIT heterostructure have been analyzed in terms of current–voltage (I–V) for different temperatures and capacitance–voltage (C–V) measurements for different frequencies, respectively. The series and shunt resistances were determined from the analysis of parasitic resistance for high forward and reverse bias voltages, respectively. The ideality factors were evaluated from I–V variation at each sample temperature as lying in between 2.51 and 3.25. The barrier height was around 0.79eV at room temperature. For low bias region, the variation in the diode parameters due to the sample temperature exhibited the thermionic emission with T0 anomaly, whereas space-charge-limited current analysis was also found to be pre-dominant carrier transport mechanism for this heterostructure. From C–V measurements, the obtained built-in potential and series resistances were found to be in good agreement with I–V results. [ABSTRACT FROM AUTHOR]

In this study, structural properties of the Zn-In-Se (ZIS) thin films deposited by thermal evaporation method were investigated. The as-grown and annealed ZIS films were found in polycrystalline structure with the main orientation in (112) direction. The compositional analysis of the films showed that they were in Zn-rich behavior and there was a slight change in the elemental contribution to the structure with annealing process. Raman analysis was carried out to determine the crystalline structure and the different vibration modes of ZIS thin films. According to these measurements, the highest Raman intensity was in the LO mode which was directly proportional to the crystallinity of the samples. The atomic force microscopy (AFM) analyses were done in order to obtain detailed information about the morphology of the thin film surface. The surface of the films was observed as nearly-smooth and uniform in as-grown and annealed forms. X-ray photoelectron spectroscopy (XPS) measurements were analyzed to get detailed information about surface and near-surface characteristics of the films. The results from the surface and depth compositional analyses of the films showed quite good agreement with the energy dispersive X-ray spectroscopy (EDS) analysis. [ABSTRACT FROM AUTHOR]

p-Si/n-ZnInSe 2 hetero-junction diode was deposited by thermal evaporation of elemental evaporation sources on the 600 μm thick p-type (1 1 1) mono-crystalline Si wafers having the resistivity value of 1 - 3 (Ω.cm). Detailed electrical characterization of the hetero-junction was performed by the help of temperature dependent current-voltage measurements. The forward current-voltage behaviour of the hetero-junction diode was investigated under the evaluation of possible current transport mechanisms. In the studied temperature range, thermionic emission and space charge limited current were found to be predominant transport models for this hetero-junction. In addition, the parasitic resistance, ideality factor and barrier height were determined. The contribution of the p- and n-layer in the junction was studied under the spectral photo-response measurement. [ABSTRACT FROM AUTHOR]

Rutile TiO2 nanorods on fluorine-doped thin oxide glass substrates via the hydrothermal technique were synthesized and decorated with a sputtered CdTe layer to fabricate a core–shell type n-TiO2/p-CdTe solar cell. Absorbance spectrum verified the absorption contribution of both TiO2 and CdTe to the absorption process. The solar cell parameters, such as open circuit voltage, short circuit current density, fill factor and power conversion efficiency were found to be 0.34V, 1.27mAcm−2, 28% and 0.12%, respectively. [ABSTRACT FROM AUTHOR]

In this study, optical and electrical characteristics of the Cu 0.5 Ag 0.5 InSe 2 (CAIS) polycrystalline thin films were investigated. They were deposited on soda lime glass substrates with the evaporation of pure elemental sources by using physical thermal evaporation technique at 200 °C substrate temperature. The thin films were characterized firstly in as-grown form, and then annealed under the nitrogen environment to deduce the effects of annealing on the optical and electrical properties of the deposited thin films related to their structural changes. In fact, these material properties of the CAIS thin films were studied by carrying out transmission, Hall Effect, and temperature dependent dark- and photo-conductivity measurements as a function of annealing temperature. From the optical analysis, the band gap energies were found between 1.44 and 1.51 eV for the as-grown and annealed films, respectively. The analysis of electrical conductivity showed that electrical properties of the films were dependent on the variable range hopping and thermionic emission conduction mechanisms at low temperature region and above the room temperature, respectively. Under different illumination intensities, the photo-conductivity properties of CAIS film samples were analyzed under the consideration of two-center model. [ABSTRACT FROM AUTHOR]

Zn-In-Se (ZIS) thin films were prepared by sequential evaporation of its elemental sources on the glass substrates. The effect of thermal annealing under nitrogen environment on the optical properties of the films was discussed. In addition to the comparative study of three different annealing temperatures, the results were analyzed by relating with their structural and compositional characteristics. The optical analyses were based on the observed interference fringes on their transmission spectra of the films. The refractive indices were calculated by means of envelope method (EM) and the continuity of the refractive indices was evaluated by three-term Cauchy fitting process. From the results of the refractive index calculations, the real and imaginary part of the dielectric constant were determined. The optical absorption coefficients of the films were found in the range of 10 3 –10 4 cm −1 over the visible and near-infrared region and by using these values, the extinction coefficients were calculated. Moreover, the band gap values were calculated from the corresponding Tauc plots, and the refractive index dispersion over the measured wavelength range was investigated with single-oscillator model (SOM) and the related parameters were obtained. [ABSTRACT FROM AUTHOR]

Zinc telluride (ZnTe) is one of the attractive semiconducting compounds used in various optoelectronic devices. The usage of ZnTe in optoelectronic applications directs researchers to search its optical characteristics in great detail. For this purpose, structural and optical properties of magnetron sputtered ZnTe thin films were studied by means of x-ray diffraction and transmission spectroscopy measurements. Structural analyses indicated that ZnTe thin films having cubic crystalline structure were successfully grown on soda-lime glass substrates. Transmittance spectra in the 400–1000 nm were recorded in between 10 and 300 K temperature region. The analyses of absorption coefficient spectra resulted in band gap energies decreasing from around 2.31 (10 K) to 2.26 eV (300 K). Temperature dependency of gap energy was studied by Varshni and O'Donnell-Chen relations to determine various optical parameters like absolute zero temperature band gap energy, change of gap energy with temperature, phonon energy. • ZnTe thin films were grown by magnetron sputtering technique. • Temperature dependent (10–300 K) band gap energies of films were reported. • Analyses resulted in gap energies of 2.31 and 2.26 eV at 10 and 300 K, respectively. [ABSTRACT FROM AUTHOR]

In this study, the material properties of CuO thin films fabricated by sputtering technique and electrical properties of CuO/n-Si structure were reported. Temperature-dependent current-voltage (I-V) measurement was carried out to determine the detail electrical characteristics of this structure. The anomaly in thermionic emission (TE) model related to barrier height inhomogeneity at the interface was obtained from the forward bias I-V analysis. The current transport mechanism at the junction was determined under the assumption of TE with Gaussian distribution of barrier height. In this analysis, standard deviation and mean zero bias barrier height were evaluated as 0.176 and 1.48 eV, respectively. Depending on the change in the diode parameters with temperature, Richardson constant was recalculated as 110.20 Acm−2K−2 with the help of modified Richardson plot. In addition, density of states at the interface were determined by using the forward bias I-V results. • CuO films were coated onto glass and n-type silicon substrates by RF magnetron sputtering technique. • Structural properties of CuO layer were determined via XRD, SEM and EDX measurements. • Electrical properties of Au-Cu/CuO/n-Si structure were analyzed. [ABSTRACT FROM AUTHOR]

Temperature-dependent transmission experiments were performed for tin selenide (SnSe) thin films deposited by rf magnetron sputtering method in between 10 and 300 K and in the wavelength region of 400–1000 nm. Transmission spectra exhibited sharp decrease near the absorption edge around 900 nm. The transmittance spectra were analyzed using Tauc relation and first derivative spectroscopy techniques to get band gap energy of the SnSe thin films. Both of the applied methods resulted in existence of two band gaps with energies around 1.34 and 1.56 eV. The origin of these band gaps was investigated and it was assigned to the splitting of valence band into two bands due to spin-orbit interaction. Alteration of these band gap values due to varying sample temperature of the thin films were also explored in the study. It was seen that the gap energy values increased almost linearly with decreasing temperature as expected according to theoretical knowledge. • SnSe thin films were deposited by RF sputtering technique. • Temperature dependent transmission measurements were achieved in between 10 and 300 K. • Tauc and derivative spectral methods revealed the presence of two band gap energies. • Crystal field and spin-orbit interactions were also discussed for band structure. [ABSTRACT FROM AUTHOR]

Abstract In this work, structural and temperature dependent optical properties of thermally evaporated CdS thin films were investigated. X-ray diffraction, energy dispersive spectroscopy and Raman spectroscopy experiments were carried out to characterize the thin films and obtain information about the crystal structure, atomic composition, surface morphology and vibrational modes. Temperature-dependent transmission measurements were performed in between 10 and 300 K and in the spectral range of 400–1050 nm. The analyses of transmittance spectra were accomplished by two different methods called as the absorption coefficient and the derivative spectrophotometry analyses. All evaluated band gap energy values at each studied temperature were in good agreement with each other depending on the applied analyses techniques. Room temperature gap energy values were found around 2.39 eV and 2.40 eV from absorption coefficient and derivative spectrophotometry analyses, respectively. Band gap energy depending on the sample temperature was studied under the light of two different models to investigate average phonon energy, electron phonon coupling parameter and the rate of change of band gap energy with temperature. [ABSTRACT FROM AUTHOR]

Characterization of Cu 2 ZnSnSe 4 (CZTSe) thin films deposited by thermal evaporation sequentially from the pure elemental sources and in-situ post annealing was carried out at 400 C under Se evaporation atmosphere. Another annealing process was applied in nitrogen atmosphere at 450 °C to get polycrystalline monophase CZTSe film structure. XRD analysis together with Raman spectroscopy was used to determine the structural properties. Spectral optical absorption coefficient evaluated from transmission data showed the band gap value of 1.49 eV for annealed film. Electrical measurements indicated that CZTSe thin films have p-type semiconductor behavior with the carrier density and mobility values of 10 −19 cm −3 and 0.70 cm 2 /(V.s). Illumination effects on the device properties of Ag/n-Si/p-CZTSe/In heterostructure were investigated by analyzing current-voltage(I-V) and frequency dependent capacitance-voltage(C-V) data. Under the illumination, Ag/n-Si/p-CZTSe/In heterostructure showed photodiode behavior having V oc value of 100 mV and I sc value of 27.5 μA. With the illumination, series resistances (R s ), diode ideality factor (n) and barrier height (Φ b ) decreased and shunt resistance (R sh ) increased. Capacitance value at lower frequency decreased due to the illumination effect. [ABSTRACT FROM AUTHOR]

Annealing effect on the structural and optical properties of the quaternary Cu–Ag–In–Se thin film deposited by the thermal evaporation has been investigated. The evaporation source was prepared by using vertical Bridgman–Stockbarger crystal growth system. Structural analysis indicated that annealing the films following to the deposition resulted in the changes from amorphous to polycrystalline phase with the preferred orientation along (1 1 2) direction. In order to determine the optical properties of the thin films as a function of annealing temperature, the transmission measurements were carried out in between 300 and 2000 nm. The optical band gap values were lying in between 1.29 and 1.50 eV upon annealing the thin films in the temperature range of 300–500 °C. The refractive indices of the samples were in the range of 2.7–3.8 depending on the wavelength region and annealing temperature by applying the Envelope Method. The other optical constants of the samples were also calculated using Cauchy Method and Single Oscillator Model. [ABSTRACT FROM AUTHOR]

CdSe x Te (1-x) (CST) ternary thin films were fabricated by stacking thermally evaporated CdSe and electron beam evaporated CdTe layers. The final structure was achieved in a stoichiometric form of approximately Cd:Se:Te = 50:25:25. The post-annealing processes at 300, 400, and 450 °C were applied to trigger the compound formation of CST thin films. The X-ray diffraction (XRD) profiles revealed that CdTe and CdSe have major peaks at 23.9° and 25.5° corresponds to (111) direction in cubic zinc-blend structure. Raman modes of CdTe were observed at 140 and 168 cm−1, while Raman modes of CdSe films were detected at 208 and 417 cm−1. The post-annealing process was found to be an effective method in order to combine both diffraction peaks and the vibrational modes of CdTe and CdSe, consequently to form CST ternary alloy. Transmission spectroscopy analysis revealed that CST films have direct band gap value of 1.6 eV. • CdSexTe1-x thin films were deposited by sequential growth using double sources. • Post annealing was used to trigger interdiffusion of the binary CdTe and CdSe layers. • By increasing annealing temperature, the crystallinity of the films was improved. [ABSTRACT FROM AUTHOR]

SnS 2 thin films grown by magnetron sputtering technique were characterized by structurally and optically in the present work. Crystalline parameters, atomic compositions, and surface characteristics of SnS 2 thin films were presented according to results of applied structural techniques. Optical studies of SnS 2 thin films were accomplished by Raman spectroscopy and transmission methods. Raman spectrum exhibited two modes around 198 and 320 cm−1. Transmittance data obtained for various temperatures between 10 and 300 K were analyzed to reveal various optical characteristics like band gap energy, variation rate of gap energy with temperature, average phonon energy, gap energy at absolute zero. Band gap energy of SnS 2 thin films were reported as 2.18 and 2.22 eV at 300 and 10 K, respectively. The temperature-band gap energy dependency was analyzed taking into account the Varshni and O'Donnell-Chen models. [ABSTRACT FROM AUTHOR]

• CuZnSe 2 (CZSe) thin films were co-deposited by magnetron sputtering method. • CZSe films have stoichiometric elemental composition and polycrystalline nature. • E g value decreased from 2.31 (10 K) to 2.27 eV (300 K) with increase of temperature. • Band gap energy with temperature was analyzed by Varshni and O'Donnell models. • Dark- and photo-conductivity values were investigated by thermionic emission model. In the present work, CuZnSe 2 (CZSe) thin films were co-deposited by magnetron sputtering of ZnSe and Cu targets. The structural analyses resulted in the stoichiometric elemental composition and polycrystalline nature without secondary phase contribution in the film structure. Optical and electrical properties of CZSe thin films were investigated using temperature-dependent optical transmission and electrical conductivity measurements. The band gap energy values were obtained using transmittance spectra under the light of expression relating absorption coefficient to incident photon energy. Band gap energy values were found in decreasing behavior from 2.31 to 2.27 eV with increase in temperature from 10 to 300 K. Temperature-band gap dependency was evaluated by Varshni and O'Donnell models to detail the optical parameters of the thin films. The experimental dark and photoconductivity values were investigated by thermionic emission model over the grain boundary potential. Room temperature conductivity values were obtained in between 0.91 and 4.65 (× 10−4 Ω−1cm−1) under various illumination intensities. Three different linear conductivity regions were observed in the temperature dependent profile. These linear regions were analyzed to extract the activation energy values. [ABSTRACT FROM AUTHOR]