Structural,optical and electrical characterization of chemically deposited CdSe thin films

Cadmium selenide (CdSe) thin films have been deposited on glass substrate. CdSe thin films were characterized by various techniques such as X-ray diffraction, scanning electron microscopy and UV–vis–NIR double beam spectrophotometer. The electrical and thermo-electrical properties are also studied. The X-ray diffraction analysis shows that the film samples are in cubic crystal structure. The optical band gap energy (Eg) was found to be 1.7 eV.     

Influence of iron doping on morphological,structural and optical properties of zinc oxide thin films prepared by dip-coating method

Undoped zinc oxide and iron-doped zinc oxide thin films have been deposited by the sol-geldipcoating method. The Fe/Zn nominal volume ratio was 5% in the solution. The effects of Fe incorporation on morphological, structural, and optical properties of ZnO films were investigated. The scanning electron microscopy measurements showed that the surface morphology of the prepared thin films was affected by Fe doping. The X-ray diffraction patterns of the thin films showed that doped incorporation leads to substantial changes in the structural characteristics of ZnO thin films. The optical absorption measurements indicated a band gap in the range of 3.31 to 3.19 eV. The X-ray photoelectron spectroscopy demonstrated that Fe is incorporated in the ZnO matrix with 6.5 atomic percent (at %). The energy dispersive spectroscopy studies indicated the formation of ZnO with high efficiency.     

Boron and fluorine doped ZnO films obtained from zinc chloride precursor via chemical spray pyrolysis

Both boron (1, 2 and 3 at %) and fluorine (1, 3, 5 and 7 at %) doped zinc oxide thin films (ZnO:B:F) were fabricated using zinc chloride precursor by airbrush spray pyrolysis technique on glass substrates. X-ray diffraction (XRD) measurements show that all ZnO:B:F films have hexagonal wurtzite structure with a preferential growth along the [0 0 2] direction on glass substrates. Scanning electron microscope (SEM) results show that the morphologies of all doped films have a regular hexagonal shape. The optical measurements reveal that ZnO:B:F films have a direct band gap and optical energy gaps are increasing with boron and fluorine concentration. The optical transmittance of B and F doped ZnO films is measured very low due to columnar structure of prepared films. Moreover, it has been observed that the doping of ZnO films with boron and fluorine decreases the electrical resistance, and the lowest resistances of films were observed at 1%B–3%F and 2%B–3%F concentrations.     

Tailoring the Microstructural,Optical, and Electrical Properties of Nanocrystalline WO3 Thin Films Using Al Doping

We have studied the influence of Al doping on the microstructural, optical, and electrical properties of spray-deposited WO₃ thin films. XRD analyses confirm that all the films are of polycrystalline WO₃ in nature, possessing monoclinic structure. EDX profiles of the Al-doped films show aluminum peaks implying incorporation of Al ions into WO₃ lattice. On Al doping, the average crystallite size decreases due to increase in the density of nucleation centers at the time of film growth. The observed variation in the lattice parameter values on Al doping is attributed to the incorporation of Al ions into WO₃ lattice. Enhancement in the direct optical band gap compared to the undoped film has been observed on Al doping due to decrease in the width of allowed energy states near the conduction band edge. The refractive indices of the films follow the Cauchy relation of normal dispersion. Electrical resistivity compared to the undoped film has been found to increase on Al doping.     

Influence of indium doping on the properties of spray deposited CdS0.2Se0.8 thin films

Polycrystalline indium doped CdS_0.2Se_0.8 thin films with varying concentrations of indium have been prepared by spray pyrolysis at 300 °C. The as deposited films have been characterized by XRD, AFM, EDAX, optical and electrical resistivity measurement techniques. The XRD patterns show that the films are polycrystalline with hexagonal crystal structure irrespective of indium doping concentration. AFM studies reveal that the RMS surface roughness of film decreases from 34.68 to 17.76 with increase in indium doping concentration up to 0.15 mol% in CdS_0.2Se_0.8 thin films and further it increases for higher indium doping concentrations. Traces of indium in CdS_0.2Se_0.8 thin films have been observed from EDAX studies. The optical band gap energy of CdS_0.2Se_0.8 thin film is found to decrease from 1.91 eV to 1.67 eV with indium doping up to 0.15 mol% and increase after 0.15 mol%. The electrical resistivity measurement shows that the films are semiconducting with minimum resistivity of 3.71 × 10⁴ Ω cm observed at 0.15 mol% indium doping. Thermoelectric power measurements show that films exhibit n-type conductivity.     

喷涂法制备缓冲层CuI薄膜的生长

采用乙腈为溶剂的喷涂工艺制备晶粒尺寸约为35nm的CuI薄膜。研究乙腈溶液中碘掺杂浓度对CuI薄膜结构、形貌和光学性能的影响。XRD衍射结果表明：碘掺杂的CuI薄膜具有γ态立方闪锌矿结构,沿（111）晶面择优取向生长。SEM结果显示CuI薄膜的微结构与乙腈溶液中碘掺杂量有关;当乙腈溶液中掺杂碘为0.025g时,所制备的CuI薄膜均匀、致密,在可见光区域光学透过率可达75.4%,禁带宽度接近2.96eV。     

Doping effect of M (M = Nb,Ce, Nd,Dy, Sm,Ag, and/or Na) on the growth of pulsed-laser deposited V2O5 thin films

V₂O₅ thin films were prepared by using a pulsed-laser deposition technique. We investigate the doping effect of elements such as Nb, Ce, Nd, Dy, Sm, Ag, and/or Na, on the growth of V₂O₅ films. X-ray photoelectron spectroscopy results indicate that the oxidation state of vanadium is almost highest. X-ray diffraction study reveals that the doping of Nb urges to crystallize the V₂O₅ films. The Raman measurement shows that the doping of rare earth elements leads to the shift from 146 to 149 cm^?1 about –O–V–O–O–V– bond and from 995 to 998 cm^?1 about VO double bond. The optical measurement study reveals that the doping effect on the VO double bond is classified into two types. The addition of Nb, Ce, Nd, Sm, and/or Dy results in an increase of band gap, while those of Ag, and/or Na decreases a band gap. The electrochromic parameters of V₂O₅ films doped with Nb, and/or Na are superior to that of other elements as an electrochromic device (ECD).     

溶胶-凝胶法制备掺铁钛酸铋铁电薄膜光学性能的研究

通过溶胶-凝胶法制备了不同掺杂浓度的Fe-BTO铁电薄膜以减小其光学带隙,研究不同Fe掺杂浓度对BTO铁电薄膜铁电光伏效应的影响。结果表明,使用溶胶-凝胶法对BTO铁电薄膜掺杂不同浓度的Fe,所制备的薄膜结晶度较好、网状结构明显、空间分布均匀,晶粒大小均一;通过溶胶-凝胶法制备Fe-BTO铁电薄膜在Fe掺杂浓度x=0.9附近可以明显减小其禁带宽度。     

Annealing temperature dependence of the optical and structural properties of selenium-rich CdSe thin films

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM). Analyses of the absorption spectra in the wavelength range (200-2500 nm) of SR-CdSe thin films indicates the existence of direct and indirect optical transition mechanisms. The optical band gap (E_g) of as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively. After annealing, the absorption coefficient and optical band gap were found to decrease, while the values of refractive index (n) and the extinction coefficient (k_ex) increase. The dispersion of the refractive index is described using the Wimple-Di Domenico (WDD) single oscillator model and the dispersion parameters are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant (?_∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline transformations.     

Experimental Investigation of Spray-Deposited Fe-Doped ZnO Nanoparticle Thin Films: Structural, Microstructural, and Optical Properties

Structural, microstructural, and optical properties of the undoped and Fe-doped zinc oxide (ZnO) thin films grown by spray pyrolysis technique using zinc nitrate as a host precursor have been reported here. X-ray diffraction spectra confirm that all the films have stable wurtzite structure and the effects of Fe dopants on the diffraction patterns have been found to be in agreement with the Vegard’s law. Scanning electron microscopy results show good uniformity and dense surface having spherical-shaped grains. Energy dispersive x-ray analyses with elemental mapping of the Fe-doped films show that the Fe dopants are incorporated homogeneously into the ZnO film matrix. The x-ray photoelectron spectroscopy spectra confirm the presence of 3+ oxidation state of Fe in the doped films. Atomic force microscopy analyses clearly show that the average surface roughness and the grain size decrease with the addition of Fe dopants. Optical studies reveal that the optical band gap value decreases on Fe doping. The 1 at.% Fe-doped film shows normal dispersion for the wavelength range 450-700 nm. The PL spectra of the films show a strong ultraviolet emission centered at ~388 nm in the case of 1 at.% Fe-doped film. A slow photo current response in the films has been observed in the transient photoconductivity measurement.     

Conductive Poly(3-methylthiophene) Thin Films

The work described herein represents an efficient method in the deposition of poly(3-methylthiophene),P3MeTh,thin films utilizing a microwave plasma system in combination with a simultaneous doping with iodine.It was envisaged that,an alternative poly(3-methylthiophene),P(3MeTh),with an electron donating methyl substituent,would reduce the degree of ring opening which reportedly occur to a certain extent during the plasma polymerization process of its parent compound polythiophene.An alkyl substituent would also increase the solubility of the materials.P(3MeTh)thin film deposition has been performed utilizing microwave-induced plasma polymerization in order to directly grow films on glass substrates.Moreover,simultaneous doping of the so-formed polymer with iodine has been carried out as opposed to the post-synthesis doping method.This is aimed to prolong electrical conducting lifetime of the materials.The synthesized films were characterized by attenuated total reflection fourier transform infrared(ATR FT-IR)spectroscopy and energy dispersive X-ray spectroscopy(EDS)to confirm the incorporation of iodine dopant into the films.Scanning electron microscopy showed uniformly deposited films.It has been observed that the electrical conductivity of the doped film is 2 orders of magnitude higher than the undoped counterpart.The doped fabricated films exhibited UV-vis spectra indicative of increased π-conjugation(536 nm).Furthermore,electrical conductivity of the in situ doped P(3MeTh)is more highly sustained over a longer period of time.     

Effect of film thickness on microstructure parameters and optical constants of CdTe thin films

Different thickness of cadmium telluride (CdTe) thin films was deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The XRD experiments showed that the films are polycrystalline and have a zinc-blende (cubic) structure. The microstructure parameters, crystallite size and microstrain were calculated. It is observed that the crystallite size increases and microstrain decreases with the increase in the film thickness. The fundamental optical parameters like band gap and extinction coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.481 to 1.533 eV with the increase in the film thickness. It was found that the optical band gap increases with the increase in thickness. The refractive indices have been evaluated in transparent region in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index can be extrapolated by Cauchy dispersion relationship over the whole spectral range, which extended from 400 to 2500 nm. It is observed that the refractive index, n increases on increasing the film thickness up to 671 nm and then the variation of n with higher thickness lie within the experimental errors.     

Effect of ammonia solution on properties of sprayed ZnO thin films consisting of nano-pyramids

Hexagonal wurtzite zinc oxide (ZnO) thin films were deposited at substrate temperatures from 300 to 500 °C with surfactant of ammonia solution. The effect of ammonia on the structural, surface morphology, compositional, optical and electrical properties of ZnO thin films was studied. X-ray diffraction shows that the all films are polycrystalline in nature and have a hexagonal wurtzite structure with a high preferential orientation (002) plane for ammonia solution. High-resolution SEM studies reveal the formation of ZnO films consisting of nano-pyramids with uniformly distributed grains over the entire surface of the substrates. Photoluminescence studies indicate the presence of two emission peaks: (a) a sharp ultra-violet near band edge ～392 nm, (b) a sharp visible deep-level green emission peak ～564 nm. The optical properties show that the direct band gap energy values increase with increasing substrate temperatures.     

Microwave assisted chemical bath deposited polyaniline films for supercapacitor application

In the present investigation, we are reporting the first time synthesis of polyaniline (PANI) thin films by microwave assisted chemical bath deposition (MW-CBD) method on the stainless steel substrate. The PANI thin films are prepared by the oxidation of aniline in the domestic microwave oven working with frequency 2.45 GHz. The PANI thin films are characterized for their structural, morphological and optical studies by means of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and UV-vis spectrophotometer. The wettability study is carried out by measuring the contact angle. The supercapacitive behavior of PANI electrode is studied in 0.5 M H₂SO₄ using cyclic voltammetric (CV) measurements. The X-ray diffraction pattern showed the films are amorphous. Morphological study revealed PANI thin film is well covered over the entire substrate surface with less overgrown fine spherical granules. The optical band gap of PANI thin film is found to be 2.5 eV. The hydrophilic nature of the PANI thin films is observed from water contact angle measurement. A maximum specific capacitance is found to be 753 F g⁻¹ at the scan rate of 5 mV s⁻¹.     

Effect of Deposition Potential on Synthesis,Structural,Morphological and Photoconductivity Response of Cu_2O Thin Films by Electrodeposition Technique

The present work describes the effect of deposition potentials on structural, morphological, optical, electrical and photoconductivity responses of cuprous oxide(Cu_2O) thin films deposited on fluorine-doped tin oxide glass substrate by employing electrodeposition technique. X-ray diffraction patterns reveal that the deposited films have a cubic structure grown along the preferential(111) growth orientation and crystallinity of the film deposited at. 0.4 V is improved compared to the films deposited at. 0.2,. 0.3 and. 0.5 V. Scanning electron microscopy displays that surface morphology of Cu_2O film has a well-defined three-sided pyramid-shaped grains which are uniformly distributed over the surface of the substrates and are significantly changed as a function of deposition potential. Raman and photoluminescence spectra manifest that the film deposited at. 0.4 V has a good crystal quality with higher acceptor concentration compared to other films. UV–visible analysis illustrates that the absorption of Cu_2O thin film deposited at. 0.4 V is notably higher compared to other films and the band gap of Cu_2O thin films decreases from 2.1 to 2.04 eV with an increase in deposition potential from. 0.2 to. 0.5 V.The frequency–temperature dependence of impedance analysis shows that the film deposited at. 0.4 V has a high conductivity.I – V measurements elucidate that the film deposited at. 0.4 V exhibits a good photoconductivity response compared to films deposited in other deposition potentials.     

Study of bactericidal efficiency of magnetron sputtered TiO2 films deposited at varying oxygen partial pressure

TiO₂ thin films have been deposited at different Ar:O₂ gas ratios (20:80,70:30,50:50,and 40:60 in sccm) by rf reactive magnetron sputtering at a constant power of 200 W. The formation of TiO₂ was confirmed by X-ray photoelectron spectroscopy (XPS). The oxygen percentage in the films was found to increase with an increase in oxygen partial pressure during deposition. The oxygen content in the film was estimated from XPS measurement. Band gap of the films was calculated from the UV-Visible transmittance spectra. Increase in oxygen content in the films showed substantial increase in optical band gap from 2.8 eV to 3.78 eV. The Ar:O₂ gas ratio was found to affect the particle size of the films determined by a transmission electron microscope (TEM). The particle size was found to be varying between 10 and 25 nm. The bactericidal efficiency of the deposited films was investigated using Escherichia coli (E. coli) cells under 1 h UV irradiation. The growth of E. coli cells was estimated through the Optical Density measurement by UV-Visible absorbance spectra. The qualitative analysis of the bactericidal efficiency of the deposited films after UV irradiation was observed through SEM. A correlation between the optical band gap, particle size and bactericidal efficiency of the TiO₂ films at different argon:oxygen gas ratio has been studied.     

The molecular structure of plasma polymerized thiophene and pyrrole thin films produced by double discharge technique

Production of polythiophene (PTH) and polypyrrole (PPY) thin films via double discharge plasma system has been studied. The double discharge system is a superposition of an ordinary low-pressure dc glow discharge and a high-current pulsed one. The glass substrates were located simultaneously at three different positions in the reactor and the thin films were synthesized at constant plasma parameters to evaluate the influence of the position on the molecular structure. And, the as-grown and iodine doped thin films were investigated to find out the correlation between molecular structure variation of the iodine–film interactions, too. The PTH (C₄H₄S) and PPY (C₄H₅N) monomers without using any carrier gases have been used as plasma precursors, each at 1 mbar operating pressure. The thin films were compared by using Fourier transform infrared (FTIR), X-ray photoelectron (XPS), and UV–visible absorption spectroscopy. It is found that the thin films obtained at the pulsed plasma region where the gas phase polymerization is dominated resemble to conventional polymeric structure. The XPS depth profiles revealed that while the stoichiometry of the monomer was almost preserved with the successive depth of PTH samples, but at the PPY one was not preserved. Moreover, the atomic concentration of oxygen and nitrogen observed at the surface of the films significantly drops down beneath the surface which indicates that they could be employed as anti-corrosive materials. It is found that chemical bonding with iodine take place after doping and the value of the optical band gap of polymers (E_g) are reduced proportionally with doping time.     

Ruthenium disulfide thin films prepared by the successive ionic layer adsorption and reaction (SILAR) method

RuS2 thin films were prepared by the cost-effective chemical method-successive ionic layer adsorption and reaction (SILAR). The structural, optical, and electrical properties were investigated using X-ray diffraction, scanning electron microscopy, optical transmittance, and electrical resistivity methods. The results indicate that the films are homogeneous and dense; the structure of the as-deposited fdms is amorphous and they crystallize after annealed at 500°C for 30 min. The band gap of the as-deposited films is found to be 1.85 eV, and the electrical resistivity of them is in the order of 105 Ω.cm.     

Substrate Evolution to Microstructural and Optoelectrical Properties of Evaporated CdS Thin Films Correlated with Elemental Composition

A typical high-e fficiency solar cell device needs the best lattice matching between different constituent layers to mitigate the open-circuit voltage loss. In the present work, the physical properties of CdS thin films are investigated where films with 100 nm thickness were fabricated on the different types of substrates viz. soda–lime glass, indium-doped tin oxide(ITO)-and fl uorine-doped tin oxide(FTO)-coated glass substrates, and silicon wafer using electron beam evaporation. The X-ray diffraction patterns confirmed that deposited thin films showed cubic phase and had(111) as predominant orientation where the structural parameters were observed to be varied with nature of substrates. The ohmic behaviour of the CdS films was disclosed by current–voltage characteristics, whereas the scanning electron microscopy micrograph revealed the uniform deposition of the CdS films with the presence of round-shaped grains. The elemental analysis confirmed the CdS films deposition where the Cd/S weight percentage ratio was changed with nature of substrates. The direct energy band gap was observed in the 1.63–2.50 eV range for the films grown on different substrates. The investigated properties of thin CdS layers demonstrated that the selection of substrate(in terms of nature) during device fabrication plays a crucial role.     

Characterization of the polysilicon thin film transistors elaborated in high and low temperature processes. Study of the density of traps

The states density of traps (DOS) in the gap has been determined by a study of the temperature influence on the field-effect conductance of polycrystalline silicon thin film transistors fabricated in high and low temperature technologies. The effect on the DOS value of the granular structure, film thickness (between 50 and 150 nm) and technological process has been investigated. On the one hand, for thin film transistors (TFTs) fabricated in a high temperature process, we observed that, when the film thickness is greater than 50 nm, the DOS distribution has a ‘band tailing’ with an exponential shape. The slope increases when the thickness decreases. This indicates the enhancement of the disorder due to an important density of defects localized in the grain and or in the grain boundaries. Moreover, for thin films (t_f = 50 nm), the DOS curve shows a characteristic hump which proves the presence of dangling bonds. They are localized at 0.35 eV above the top of the valence band. On the other hand, the effect of the low temperature process produces particularities on the TFT DOS. The classical doped drain (CDD) exhibits a high density of states with a classical distribution (band tailing with an exponential shape). However, the lightly doped drain (LDD) TFT DOS shows a hump localized at 0.4 eV below the bottom of the conduction band. The difference observed on the DOS distributions is related to the in situ doping level of the polysilicon-deposited thin films.