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This communication presents the optical characterization of $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ films electroplated on Cu- and Ni-coated Cu substrates. $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ films were successfully deposited by using the electrochemical deposition method with cobalt acetate tetrahydrate as a cobalt precursor followed by annealing at $$350^{\circ }\hbox {C}$$ . The as-prepared films were characterized using X-ray diffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and stagnation temperature test. The characterization shows the presence of only the cubic spinal $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ phase in all films. The morphological analysis revealed the generation of unique fish-shaped $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ particles with uniform size distribution for the films obtained on the Ni-coated Cu substrate. The Cu substrate with and without nickel plating used for deposition has shown a profound effect on the optical characteristics of films. The solar absorbance as high as 0.96 and thermal emittance as low as 0.02 were obtained for the films deposited on the Ni-coated Cu substrate. The highest value of the figure of merit $$(F_{{1}})$$ of $$\sim $$ 0.34 and extrapolated stagnation temperature of $$\sim $$ 362 $$^{\circ }\hbox {C}$$ were realized for films having better optical characteristics. The results obtained indicate very good potential of the deposited films for solar thermal applications.

The present communication reports the structural, optical and electrical properties of p-CdTe films deposited by using spray pyrolysis technique on thoroughly cleaned sodalime glass substrates at 350 °C in inert N 2 atmosphere. The films were characterized by using XRD, Raman spectroscopy, XPS, thickness profiler, SEM, EDAX and UV–Visible spectroscopy and Hall parameters measurement. The structural studies showed the formation of pure cubic CdTe in resultant films with crystallite size = 32 nm. The texture coefficient TC ( h k l ) indicated preferential orientation of films along [3 1 1] and [5 1 1] directions. The SEM image showed almost spherical granules with average size of 0.25 μm. From UV–Visible spectral data, the maximum absorbance and direct band gap obtained using Tauc plot are found to be 0.94 and E g = 1.44 eV respectively for films having thickness, t = 3.2 μm. The Hot probe experiment, Hall coefficient R H = 1.478 × 10 3 cm 3 /C, and resistivity ρ = 2.228 × 10 1 Ω cm confirmed the p-type semiconducting behavior of CdTe films. The mobility of majority charge carriers – holes is found to be μ = 6.63 × 10 1 cm 2 /Vs. The films processed using present work can be treated as possible p-type candidate for fabrication of hetero-junction solar cell.

Uniformly distributed jet of fine droplets was created with control of spray rate ( S f ) to deposit nanocrystalline ZnO thin films by spray pyrolysis technique. X-ray diffraction analysis indicated the polycrystalline film growth with most preferred orientation along c -axis [0 0 2] direction for S f ⩽ 4.5 ml/min, above which films favored [1 0 1] direction. FE-SEM and AFM analysis revealed the uniform vertical growth of ZnO nano-rods for S f = 2.5 ml/min and the film exhibited highest transmittance (95%) with lowest dark resistivity (∼10 −2 Ω-cm). The deposition rate increased due to rise in S f . Alteration of crystallinity, grain size and film thickness with variation in S f lead to variation of band-gap energy from 3.198 eV to 3.302 eV. ZnO film deposited at optimal S f = 2.5 ml/min exhibited maximum electrical conductivity σ = 78.8 Ω −1 -cm −1 , minimum sheet resistance R s = 2.04 × 10 2 Ω/□ and highest figure of merit Φ TC = 2.93 × 10 −3 Ω −1 .

In biogas volatile fatty acid are the principle source of energy for methanogens and an increase in their concentration can enhance the process performance of biogas digester. A two phase anaerobic digestion system was used to study the effect of various factors on the net production of volatile fatty acid (VFA). For this purpose thermophilic digester maintained at 55°c (i.e. digester I) and the main digester was kept at ambient temperature (i.e. digester II). Co-digestion of vegetable waste and cow dung was investigated in two phase anaerobic biodigester system. A comparative study was carried out between control and experimental system. The amendment was controlled air supply in predigester (digester I) designed to supply with precise control in the experimental system and no aeration was done in the predigester of control system. The conditions of start up and operation were same in both the systems except controlled supply of air. A conversion of an average of 75% of organic solids fed into digester at total of 15 days hydraulic retention time (HRT) was obtained for both the system. The organic loading rate in phase I digester was 4-4.5 kg VS/m 3 /d. This phase effluent portray a drop in the pH to 4.4-4.7 as high volatile fatty acid produced in the range of 2380-5464 mg/lt with a corresponding gas production of 0.401 m 3 /kg vs. fed in the experimental system, which showed increased biogas yield than the control system. Due to the auto thermal thermophilic aerobic digestion the VFA production was enhanced which ultimately increased the biogas production by 39.72%, as compared to the control system. The NPK value of the digested sludge obtained was having 0.55% of Nitrogen, 0.56% of Phosphorous and 0.61% of Potash. Thus, limited quantity of oxygen can even lead to improved performance of anaerobic digestion reactor, under certain operating conditions. This fact is also supported by the increase in the viable count of bacteria in the experimental system, It was seen that the aeration in predigester (in two phase anaerobic digestion), could assist anaerobic digestion and would prove much beneficial, for treatment strategy for simultaneous waste treatment and energy generation.

Nanocrystalline ZnO thin films were deposited at different temperatures (Ts = 325 °C–500 °C) by intermittent spray pyrolysis technique. The thickness (300 ± 10 nm) independent effect of Ts on physical properties was explored. X-Ray diffraction analysis revealed the growth of wurtzite type polycrystalline ZnO films with dominant c-axis orientation along [002] direction. The crystallite size increased (31 nm–60 nm) and optical band-gap energy decreased (3.272 eV–3.242 eV) due to rise in Ts. Scanning electron microscopic analysis of films deposited at 450 °C confirmed uniform growth of vertically aligned ZnO nanorods. The films deposited at higher Ts demonstrated increased hydrophobic behavior. These films exhibited high transmittance (>91%), low dark resistivity (∼10−2 Ω-cm), superior figure of merit (∼10−3 Ω−1) and low sheet resistance (∼102 Ω/□). The charge carrier concentration (η -/cm3) and mobility (μ – cm2V−1s−1) are primarily governed by crystallinity, grain boundary passivation and oxygen desorption effects.

The preparation of cobalt oxide (Co 3 O 4 ) films containing 1-D interlinked nanowires by spray pyrolysis technique using cobaltous acetate (CH 3 COO) 2 Co⋅4H 2 O solutions in 1:1 water–methanol mixture and study of their optical properties are reported in this paper. The films are characterized by using different physical techniques- X-ray diffraction (XRD), UV–Visible and Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The characterization studies showed that the resultant films are impurity free, phase pure with cubic spinel Co 3 O 4 and contain 1-D interlinked nanowires having diameter and length in the ranges of 250–350 nm and 2–10 μm respectively. The resultant films also showed the better values of absorptance ( α ) = 0.94, emittance ( e ) = 0.17 as compared to the data reported in literature. The selectivity of resultant films is found to be 5.529. These films are found to have good prospects for selective solar absorption coatings because their optical properties indicate the red shift of absorption peaks, exhibiting thereby quantum-confined effect and behavior of semiconductor.

TiO 2 thin films were deposited on glass substrates by sol-gel method. Nanocrystalline TiO 2 thin films were prepared at ambient conditions and titanium tetraisopropoxide [ C 12 H 28 O 4 Ti ] was used as a Ti -precursor. The effect of annealing temperature on optical properties of nanocrystalline TiO 2 thin films was studied. The as-deposited films were dried at 100 °C for 1 hr. The films formed were further heated in temperature between 200 and 500 °C for 1 hr. The films were characterized by different techniques: XRD, UV-visible spectroscopy, FTIR spectroscopy and FESEM. The characterization studies revealed that the films are crystallized as anatase phase and nano-structured with better optical properties α = 0.89 as compared to reported data. The optical measurement showed the indirect band gap between 3.31 and 3.35 eV with corresponding crystallite sizes between 8.9 and 3.7 nm. The FESEM image of film annealed at 400 °C showed spherical nanocrystalline structure of TiO 2 particles. The crystallite sizes obtained from FESEM image are found to be between 30 and 100 nm. It is also observed that refractive index of the film increases with increasing the annealing temperature. The smaller crystallite size gives larger band gap due to quantum size effects.

The preparation of Co 3 O 4 films containing 1-D interlinked nanowires by electrochemical deposition technique using CH 3 COO )2 Co .4 H 2 O solutions in distilled water and study of their optical properties are reported in this paper. The films are characterized by using XRD, UV-visible & FTIR spectroscopies, XPS and SEM. The characterization studies showed that the resultant films are impurity free, phase pure Co 3 O 4 with cubic spinel symmetry and contain 1-D interlinked nanowires having diameter & length between 250-350 nm & 2-10 μm respectively. The resultant films showed the better values of absorptance (α) = 0.94, emittance (ε) = 0.17 and selectivity = 5.529 as compared to reported data. These films are found to have good prospects for selective solar absorption coatings because their optical properties indicate the red shift of absorption peaks, exhibiting thereby quantum-confined effect and behavior of semiconductor.

In present paper, we report the preparation of CdTe films on thoroughly cleaned glass substrates by using the novel spray pyrolysis technique with CdCl 2. H 2 O and TeO 2 as precursor materials. The films were deposited on glass substrates by using the parameters: (a) spray nozzle - substrate distance = 30 cm, (b) sparing solution conc. = 0.02 M, (c) carrier N 2 gas flow rate = 15 lpm, (d) substrate temperature = 350°C, (e) deposition time = 15 min. (f) N 2 gas purging time for deposition chamber = 45 min. and (g) amount of spray solution = 50 ml solution. The resultant films were characterized by using physical techniques: XRD, FTIR, EDAX and SEM. The characterization results showed that the resultant films are having material purity and cubic CdTe phase purity with zinc blend symmetry. The SEM study revealed the nano-rod morphological feature of CdTe films with rod diameter in range of 100 - 250 nm and average rod length ~ 5μm. The values of absorptance (α) and band gap energy ( E g ) for these films are found to be 0.91 and ~ 1.42 eV respectively. These results indicated the high potential of CdTe films prepared in the present work for solar cell applications.

Contact angle (CA) measurement is used as an empirical diagnostic method to pre-evaluate the performance of N3 related dye-sensitized solar cells. The method uses a 30 min sensitization of ZnO nanoplatelet-based electrodes, and the CA value of ∼48° is optimized for a maximum short-circuit current density of about 6.7 mA cm−2. On account of local inhomogeneity, resulting from the Zn2+/dye complex layer, a systematic study of the effect of dye-loading time on the surface wettability and solar-to-electrical conversion performance of dye-sensitized solar cells is undertaken. The wurzite structure and nanoplatelet morphology are confirmed by X-ray diffraction and high-resolution scanning electron microscopy, respectively.

Nanocrystalline undoped and Al doped ZnO thin films were synthesized by the chemical spray pyrolysis of Zinc acetate and Aluminium chloride solution. The optoelectronic properties of undoped and Al:ZnO films were investigated. The XRD patterns of films were preferably oriented along c-axis [0 0 2] plane with the hexagonal wurtzite structure. The Al-doping caused no additional X-ray diffraction peaks when compared with XRD of undoped film, indicating Al2O3 content was below the detection limit. The crystallite size of undoped and Al doped film was 48 nm and 51nm respectively, as measured from X-ray diffractogram. The films are of high optical transmittance (≥ 90%). The resistivity of the film was found to decrease because of Al doping. The dark resistivity measurement for Al:ZnO film was of the order of 10-3 Ω-1cm-1. The band gap energy of the film was found to vary from 3.25 to 3.32eV indicating the Moss Burstein shift. Al:ZnO films can be used as transparent conducting oxide layers for photovoltaic applications.

Silicon nitride films are deposited in presence of nitrogen gas plasma by ‘Activated Reactive Evaporation (ARE)’ process on silicon substrates maintained at room temperature. Silicon powder was evaporated by e-beam evaporation in the presence of nitrogen gas plasma excited by a radio frequency (RF) power source (13.56 MHz). Depositions were carried out at different RF plasma powers. The deposited films were characterized by X-ray diffraction, X-ray photoelectron and UV–Visible spectroscopy, scanning electron microscopy and ellipsometry techniques. The X-ray diffraction pattern reveals the polycrystalline nature of the films with characteristics of hexagonal structure. X-ray photoelectron spectroscopy showed formation of silicon-rich silicon nitride. Observation of the films under scanning electron microscope shows a smooth and pinhole-free surface. The film deposited at 70 W RF plasma power for 18-min deposition time showed the refractive index (‘ η ’ at λ = 632.8 nm) and the thickness ( d ) 1.98 and 68.5 nm, respectively. The minimum reflectivity R = 1.74% is obtained from UV–Visible spectroscopy at λ = 547 nm. For the condition of near quarter wavelength single layer antireflection coating the optical thickness of the layer was taken as a quarter wavelength d = λ /4 η at the minimum reflectivity observed for the film. The above results show the feasibility of using ‘ARE’ silicon nitride as antireflection coating.

Highly transparent and conductive Boron doped zinc oxide (ZnO:B) thin films were deposited using chemical spray pyrolysis (CSP) technique on glass substrate. The effect of variation of boron doping concentration in reducing solution on film properties was investigated. Low angle X-ray analysis showed that the films were polycrystalline fitting well with a hexagonal wurtzite structure and have preferred orientation in [002] direction. The films with resistivity 2.54×10 −3 Ω-cm and optical transmittance >90% were obtained at optimized boron doping concentration. The optical band gap of ZnO:B films was found ∼3.27 eV from the optical transmittance spectra for the as-deposited films. Due to their excellent optical and electrical properties, ZnO:B films are promising contender for their potential use as transparent window layer and electrodes in solar cells.

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure silane (SiH 4 ) without hydrogen dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical, and structural properties of these films are systematically studied as a function of process pressure ( P r ). The device quality a-Si:H films with a photosensitivity >10 5 were deposited at a deposition rate >40 A/s at low process pressure. However, a-Si:H films deposited at higher process pressures show degradation in their electrical and structural properties. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low process pressure contain hydrogen mainly in mono-hydrogen (Si–H) configuration whereas films deposited at higher process pressure have hydrogen in di-hydrogen (Si–H 2 ) or poly hydrogen (SiH 2 ) n complexes. The hydrogen content ( C H ) in the films was found to be less than 4 at.% over the entire range of process pressure studied. This indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen gets incorporated in the film via gas-phase reactions and substrate–gas interactions. The band gap, however was found ∼1.71 eV or much higher. We attribute high band gap at low hydrogen content may be due to presence of microvoids. Raman spectroscopic analysis showed increase in structural disorder and Rayleigh scattering with increase in the process pressure.

Thin films of silicon oxynitride (SiO x N y ) were deposited successfully on silicon wafer substrates using electron beam physical vapor deposition (EB-PVD) technique by varying the substrate temperature ( T =100–450 °C) and deposition time ( t =0.5–2.5 min). The films were characterized by UV–Visible and X-ray photoelectron spectroscopy (XPS), Tally step measurement and Ellipsometry. The minimum reflectivity R =1.72% is obtained for the films deposited under the conditions of T =350 °C, t =1.5 min at λ =548 nm. Further, the characterization results revealed that the refractive index (RI) of the films increases with increase in the substrate temperature due to increase in silicon nitride content. The refractive index and the thickness of the films were found to be in the range of n =1.72–1.90 and d =40–138 nm, respectively. The values n =1.88 and d =79 nm observed corresponding to the minimum reflectivity R =1.72% satisfy the condition of near quarter wavelength single layer antireflection coating. Thus, the above films might have the tremendous potential for antireflective coating applications.

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure saline (SiH 4 ) without hydrogen dilution by the hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural properties of these films are systematically studied as a function of filament temperature ( T fil ). The device quality a-Si:H films which were obtained at high deposition rate (3≤ r d ≤85 A/s) using filament temperature (1400≤ T fil ≤1900 °C) without hydrogen dilution show good structural, optical and electrical properties. However, the films deposited at higher filament temperature show an amorphous-to-microcrystalline transition. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low filament temperature contain hydrogen mainly in mono-hydride (Si–H) configuration whereas films deposited at higher filament temperature have hydrogen in di-hydride (Si–H 2 ) or poly-hydride (SiH 2 ) n complexes. The low hydrogen content ( C H ) in the films indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen is incorporated in the film via gas phase reactions and substrate–gas interactions. The band gap, however, was found to be ∼1.71 eV or much higher. We suggest high band gap at low hydrogen content may be due to the presence of microvoids. Raman spectroscopic analysis showed the increase in structural disorder and Rayleigh scattering with increase in filament temperature.

Hydrogenated amorphous silicon germanium (a-SiGe:H) films were deposited using SiH4 and GeH4 mixture without H dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural of these films are systematically studied as a function of substrate temperature (Tsub). The FTIR spectroscopic studies showed that a-SiGe:H films deposited at high Tsub contain H mainly the monohydride configuration whereas the films deposited at low Tsub has H in polyhydrides or (Si–H2)n complexes form. The low CH in a-SiGe:H films indicates that the growth of film is mainly from the atomic species evaporated from the hot filament and H gets incorporated in the film via gas phase reactions and substrate–gas interactions. Raman spectroscopic studies showed that the structural order of a-SiGe:H films improve with increase in Tsub. The T sub =300 ° C was found to be the optimized substrate temperature for the synthesis of device quality a-SiGe:H films.

Multilayer structures of the type a-Si:H/μc-Si:H were fabricated for the first time by hot wire chemical vapor deposition (HW-CVD) technique. These multilayers were studied for their opto-electronic and photovoltaic properties as a function of a-Si:H sublayer thickness. The microcrystalline phase of a-Si (μc-Si:H) of thickness 250 A have been used to create drift field in these multilayer structures. The quantum size and photovoltaic effects are observed in these multilayer structures. The persistent photoconductivity measurements clearly indicate the existence of interface defects and spatial charge separation due to the formation of p-n junction field. The best photovoltaic performance was obtained with the fill factor 0.4062 and conversion efficiency ( η ) 2.08% over an active area of 0.0132 cm 2 . The advantage in these multilayer structures is that no hazardous gases are involved in the fabrication process because no intentional doping is performed and all depositions were carried out in a single deposition chamber.

The electrical, structural and optical properties of hydrogenated amorphous silicon (a-Si:H) films deposited from pure silane (SiH 4 ) using hot wire chemical vapor deposition (HW-CVD) technique are systematically studied as a function of silane flow rate F SiH 4 between 5 and 30 sccm. We found that the properties are greatly affected by the silane flow rate over the range we studied. The device quality a-Si:H films with a photosensitivity >10 5 were deposited by HW-CVD at a deposition rate >10 A s −1 using low silane flow rate. However, a-Si:H films deposited at higher silane flow rate and/or higher deposition rates show degradation in their structural and electrical properties. The FTIR studies indicate that the hydrogen bonding in a-Si:H films shifts from mono-hydrogen (Si–H) to di-hydrogen (Si–H 2 ) and (Si–H 2 ) n complexes when films were deposited at higher silane flow rate. The hydrogen content in the a-Si:H films increases with increase in silane flow rate and was found to be less than 10 at.%. The Raman spectra show increase in disorder and the Rayleigh scattering with increase in silane flow rate. The optical band gap also shows an increasing trend with silane flow rate. Therefore, only the hydrogen content cannot be accounted for the increase in the optical band gap. We think that the increase in the optical band gap may be due to the increase in the voids. These voids reduce the effective density of material and increase the average Si–Si distance, which is responsible for the increase in the band gap. Silane flow rate of 5 sccm, appears to be an optimum flow rate for the growth of mono-hydrogen (Si–H) bonded species having low hydrogen content (∼4.25 at%) in a-Si:H films at high deposition rate (∼12.5 A s −1 ), high photosensitivity (∼10 5 ) and small structural disorder.

In this letter, we report narrow band gap (1.39–1.53 eV) a-SiGe:H films with high photosensitivity (∼10 4 –10 5 ) are grown successfully by HW-CVD using a mixture of (GeH 4 +SiH 4 ) at low flow rates and without hydrogen dilution with higher deposition rates (>10 A/s). These films are characterized by Raman spectroscopy, FTIR spectroscopy and UV–Visible spectroscopy. The band gap of a-SiGe:H films can be narrowed by increasing the germane gas fraction without apparent degradation in their electronic properties. The low hydrogen content in a-SiGe:H films indicates that the growth of a-SiGe:H films is mainly from the atomic species (Si, Ge and H) evaporated from the hot filament.

The electrical, structural and optical properties of undoped and phosphorus doped μc-Si:H films prepared by a HW-CVD technique have been studied. The hydrogen (H 2 ) dilution of silane has been varied carefully to produce undoped μc-Si:H films. The amorphous-to-microcrystalline transition was observed for a hydrogen dilution ratio >0.75. The phosphorus doped μc-Si:H films were deposited by varying the phosphine (PH 3 ) gas flow rate. The structural properties of these films have been investigated by Raman spectroscopy, low angle X-ray diffraction spectroscopy and Fourier transform infrared vibrational spectroscopy. Electrical characterization has been carried out by dark conductivity and charge carrier activation energy measurements. The phosphorus doped μc-Si:H films showed that the addition of PH 3 to the source gases promotes the growth of crystallinity. The increase in crystallite size and crystalline volume fraction with the addition of PH 3 to the source gases indicates that it enhances the crystallization of the μc-Si:H film. Low angle XRD studies shows that the PH 3 doped μc-Si:H does not show any preferential orientation crystallites. For optimized deposition conditions PH 3 doped μc-Si:H films with high dark conductivity (0.4 S/cm), low activation energy (0.03 eV) and high band gap (1.82 eV) were obtained with a high deposition rate (13 A/s). However, for these optimized conditions, the hydrogen content was relatively large (8.3 at.%).

Obtaining thickness uniformity over a large substrate area seems to be a bottleneck as far as the industrial applications of the hot-wire CVD (Cat-CVD) process is concerned. In order to address the different issues in this respect, we have simulated the hot-wire CVD growth process and proposed a proper filament geometry for maximum thickness uniformity. The hot filament was assumed as a one-dimensional assembly of point sources. Five types of commonly used filament geometries were considered for their performance to identify the best filament geometry for maximum thickness uniformity. Here, the chamber pressure was assumed to be low enough so that the Knudsen number Kn>1. Based on our results, we propose a parallel filament geometry for maximum thickness uniformity over large substrate areas. By applying the model further to the parallel filament geometry, the relations between substrate–filament distance and minimum filament length, as well as the number of parallel filaments and the separation between them, which are necessary for the required thickness uniformity over the given substrate area, were determined. The validity of the model was checked using the ‘Matched-Pair t-test’. The effect of chamber pressure on thickness uniformity and growth rate, when it is sufficiently high to make the Knudsen number Kn

Boron-doped hydrogenated microcrystalline silicon (μc-Si:H) films were prepared using hot-wire chemical vapor deposition (HWCVD) technique. Structural, electrical and optical properties of these thin films were systematically studied as a function of B2H6 gas (diborane) phase ratio (Variation in B2H6 gas phase ratio, dopant gas being diluted in hydrogen, affected the film properties through variation in doping level and hydrogen dilution). Characterization of these films from low angle X-ray diffraction and Raman spectroscopy revealed that the high conductive film consists of mixed phase of microcrystalline silicon embedded in an amorphous network. Even a small increase in hydrogen dilution showed marked effect on film microstructure. At the optimized deposition conditions, films with high dark conductivity (0.08 (Ω cm)−1) with low charge carrier activation energy (0.025 eV) and low optical absorption coefficient with high optical band gap (∼2.0 eV) were obtained. At these deposition conditions, however, the growth rate was small (6 A/s) and hydrogen content was large (9 at%).

Undoped a-SiGe : H films were deposited by the RF plasma chemical vapor deposition method. Films deposited at different substrate temperatures ranging between 100°C and 300°C were studied for their optoelectronic and structural properties. Structural defects like vacancies and microvoids were studied by positron lifetime spectroscopy (PLTS) at room temperature. Optoelectronic properties of the films were correlated with the PLTS measurements. The observations show a decrease in the deposition rate with substrate temperature. Good optoelectronic properties and proper structural relaxation have been obtained with a decrease in microvoid concentration.

The properties of a-SiGe:H films prepared by the glow discharge plasma CVD method at various interelectrode separation were studied systematically. This study was done at two different rf power densities. It has been found that interelectrode separation plays an important role in determining film properties. It shows a more marked effect on photosensitivity at lower rf power density than at higher rf power density. Photosensitivity, in general, decreased, whereas growth rate increased with the increase in interelectrode separation. High photosensitivity (1.3×105) was obtained even at higher growth rate (245 A/min) just by controlling the interelectrode separation. Bandgap of the films was about 1.4 eV. Structural properties of the films were studied by positron life time spectroscopy (PLTS).

Boron doped p-type hydrogenated microcrystalline silicon (μc-Si:H) films have been prepared by radio-frequency glow discharge method. Highly conductive p-type μc-Si:H films can be obtained even with lower concentration of hydrogen in the rf glow discharge plasma if chamber pressure is low. Effects of increase in hydrogen (H 2 ) flow rate and chamber pressure have been studied. The structural properties of the films have been studied by X-ray diffractometry. The electrical and optical characterization have been done by dark conductivity, Hall measurements and optical absorption measurements respectively. Film with conductivity 0.1(Ω-cm) −1 with band gap 2.1 eV has been obtained.

In this paper, we analyse the performance of a suspended plate solar air heater working at low and moderate temperatures with a fluid flow on both sides of the absorber plate. A theoretical model for the system and subsequent numerical analysis of the system is presented in steady state. Some experimental measurements of the fabricated collector under realistic parameters is made, and an optimal design is given.

Fluorine-doped indium oxide films were prepared by the spray pyrolysis technique. The physical properties of these films were investigated with respect to various process parameters, namely variation of dopant concentration (in the solution), deposition temperature (Ts), carrier gas (air) flow rate and the thickness of the film. The best films had a Hall mobility of the order of 28 cm2V−1 s−1 and a carrier density of 2.7 × 1020 cm−3. These films were deposited at Ts=425 °C at an air flow rate of 71 min−1 for an atomic ratio of fluorine to indium of 72%. The electrical resistivity of these films was of the order of 10−4 Ω cm and the average transmission in the visible range was found to be 80–90%. The films were polycrystalline, n-type semiconductors with [400] as a preferred orientation. The preferred orientation changes from [400] to [222] depending upon the process parameters.

Transparent conducting films of In2O3 have been prepared by the electron beam evaporation technique (EBET) at a substrate temperature of -25 °C. As-deposited films are dark in colour. Subsequent heat treatment of these films in air resulted in crystallization of all films. In order to obtain more insight into the annealing phenomenon, three series of heat treatments were performed. The physical properties resulting from each series are discussed.

Black cobalt deposits were formed on glass substrates for use in all glass evacuated collectors. Glass was made conducting by depositing fluorine doped tin oxide films using spray pyrolysis. The reflectivity of this glass was further improved by electroplating a thin nickel layer (0.35 μm) on it. Cobalt oxide thin films were deposited on these nickel coated conducting glass substrates using spray pyrolysis. The effect of cobalt acetate concentration in the precursor solution on the performance of these multilayer coatings was studied. Solar absorptances as high as 0.93–0.94 and thermal emittances as low as 0.09 were obtained for films deposited with lower concentrations. For films deposited with higher concentrations the selectivity significantly reduces from ~ 33 to ~ 3.0. Structural analysis confirms the presence of Co 3 O 4 .

Antimony‐doped tin oxide films were deposited by spray pyrolysis technique. The effect of antimony doping on structural and electrical properties was investigated in detail using the x‐ray diffraction technique and room‐temperature Hall measurements. Antimony doping did not affect the preferred growth along [200] to a considerable extent. These results were analyzed on the basis of structure factor calculations. From the Hall measurements, the lowest electrical resistivity, i.e., 5.2×10−4 Ω cm was observed for the films with a doping level of 2.3 at. % in the solution. This value of electrical resistivity is the lowest reported so far in the case of spray deposited antimony‐doped SnO2 films. The grain boundary and ionized impurity scattering were observed to be prevalent in governing the electronic transport of lightly and heavily doped films, respectively.

Antimony-doped tin oxide films were deposited by spray pyrolysis on Corning 7059 substrates. The structural and electrical properties of the films deposited with different doping levels were studied. Relative variations in the structural properties were explained on the basis of structure factor calculations. The results show that the incorporation of antimony atoms takes place only at substitutional sites. As expected, the substitutional replacement of tin by antimony atoms increased appreciably the free carrier density of the film.

Indium-doped zinc oxide (IZO) films were prepared by the spray pyrolysis technique. The effect of gradual incorporation of indium cations on the structural, electrical, and compositional properties of IZO films was studied in detail. It was observed that even a small addition of indium modifies the preferred growth of IZO film from the [002] direction to the [101] direction. Such a modification in growth pattern is a result of more nucleating centers created by indium doping. Indium dopant improves the electrical properties of the films. The carrier concentration depends mainly on the indium dopant level while the mobility is affected by the changes in crystal orientation that take place due to addition of dopants. X-ray photoelectron spectroscopy results show that indium doping does not lead to any stoichiometric changes in the IZO films and the dopant incorporation in the film is linearly proportional to that in the solution.

Indium oxide films were deposited by an electron beam evaporation technique on Corning® glass substrates at various substrate temperatures ranging from 25 to 300 °C. As-deposited films appeared to be dark or semitransparent; whether they were amorphous or polycrystalline depended on the substrate temperature. In order to obtain good opto-electronic properties, these films were subjected to a heat treatment in air at various temperatures ranging from 250 to 600 °C. The In2O3 film prepared at 25 °C and annealed at 500 °C in air was found to be a good transparent conductor. The optical, electrical and structural properties of films deposited at various substrate temperatures and annealed at various temperatures are discussed.

Using the spray pyrolysis technique thin films of indium oxide were prepared on Corning glass (7059) at a substrate temperature of 425 °C at different flow rates. The electrical and structural properties of these films were studied. The Hall measurements at room temperature showed that the films prepared in an air flow rate of 7 litre min−1 have the highest mobility of 47 cm2 V−1 s−1 and a minimum resistivity of 1.125 × 10 −3 Ω cm. The X-ray diffraction patterns showed that the films have a preferred orientation of [400] which peaks at the air flow rate of 7 litre min−1.

For highly conducting transparent films, thickness is an important parameter. This investigation optimizes the film thickness to obtain high electrical conductivity without appreciably affecting the transparency. Undoped Indium oxide films having different thickness have been deposited on Corning glass (7059) by using the spray pyrolysis technique. Study of the structural, electrical and optical properties of these films reveals that the mobility increases as the film thickness increases till its value is 6500 A° after which the mobility decreases. This behaviour of the mobility is closely related to the crystallinity of the films. A high value of mobility of 53 cm 2 V −1 s −1 has been achieved. The variation in the number of charge carriers with thickness is small. At 6500 A° the lowest value of resistivity obtained is 9.3 × 10 −4 щ cm and the visible transmission is 82 %. Another interesting feature of this work is the improvement in both electrical and optical film properties for the thickest film (1.03 μm) when the substrate temperature is increased from 425°C to 475°C.

Thin films of undoped In 2 O 3 have been deposited at different substrate temperatures using the spray pyrolysis technique. These films show a preferred orientation which depends upon the deposition temperature of the substrate. The number of charge carriers and their mobility for the films have been measured and attempts have been made to explain these results. The results of optical transmission and energy band gap measurements are also included.

Indium-doped zinc oxide (IZO) films were deposited on Corning 7059 substrates by the spray pyrolysis technique. To achieve higher electrical conductivity both the zinc acetate concentration and indium concentration in the solution were varied. The films were characterized for their structural and electrical properties. Film stability in H2 plasma was also checked for possible use in amorphous and microcrystalline silicon related fields. It was observed that the films can be sustained in a hydrogen plasma, and hence IZO films of high conductivity can be used for the development of amorphous and microcrystalline silicon solar cells.

In order to probe into the growth mechanism of sprayed SnO2 films, the films were deposited with different Sn concentrations in the precursor solution. The orientational properties were determined using grazing incidence x‐ray diffraction. The preferred growth changed from [110] to [200] direction as the Sn incorporation was increased. Such a change in growth can be anticipated from structure factor calculations. The compositional analysis was done using x‐ray photoelectron spectroscopy. The Hall effect measurements indicated that the carrier concentration and mobility are sensitively dependent on the orientation and composition of the films.

Tin oxide thin films were deposited by the spray pyrolysis technique on Corning 7059. The X-ray diffraction results indicated that all deposited films were polycrystalline with a tetragonal (rutile) structure. The films showed preferred [200] orientation irrespective of the deposition conditions for a fixed solution composition. Hence, attempts were made to control the preferred growth by changing the composition of the aqueous solution. It seems that by varying the amount of hydrated SnCl 4 one can achieve better control on the preferred orientation. The experimental results have been explained on the basis of the calculated structure factors. A correlation between the structural and electrical properties is also discussed.

Nanocrystalline ZnO films were synthesized by a chemical spray pyrolysis of zinc acetate solution. The deposition temperature (450degC) was kept constant by obstructing the spray after regular intervals. The XRD patterns of ZnO films were preferably oriented along c-axis (0 0 2) plane with the hexagonal wurtzite structure. The dependence of texture coefficient (TC) and standard deviation (sigmag) on spray obstruction time was also studied. The films synthesized were highly transparent (>94%) and conductive (dark conductivity 24.67 Omega-cm). The energy gap of the film was found to vary between 3.18 eV to 3.22 eV. The variation in sheet resistance (Omega/ ) and figure of merit (PhiTC) was also studied in view of their possible applications in optoelectronic devices.

Electron Beam Physical Vapor Deposited (EB-PVD) silicon oxynitride (SiOxNy) films of various compositions between SiO2 and Si3N4 were grown by changing the substrate temperature and deposition time The SiOxNy films were deposited at various temperatures ranging from 100°C to 400°C on single crystal wafer ( single side polish)and soda lime glass substrates. Films were characterized by using XPS, EDS, Photoluminescence, UV-Visible spectroscopy and Ellipsometry. The ellipsometric measurements shows that the values of refractive indices , n and k are in the range of 1.60 to 1.98 and 0.03 to 0.08 respectively. The reflectivity of 1.64% was observed for the SiOxNy films deposited at T=350°C ant t=1.5 min. The XPS and EDS analysis shows the incorporation of nitrogen in the films increases with increase in substrate temperature and deposition time. The incorporation of nitrogen in the films is further confirmed by photoluminescence spectra. The photoluminescence spectroscopy measurements were done at room temperature. The energy of the PL peak for 2.54eV (~490 nm) excitation is 2.30 eV (~560 nm). From the above results we feel that the EBPVD deposited SiOxNy films has tremendous potential in antireflective applications.

As-deposited thin films of SnO 2 with substrate temperatures of 50, 200 and 350°C revealed that the films required an additional step of annealing to change the SnO 2 phase to SnO 2 with acceptable optical and electrical properties. Films deposited at 350°C and annealed at 650°C for 2h met the desired requirements

Publisher Summary Transparent conducting oxide (TCO) films are useful as transparent electrodes in various electro-optical devices, solar cells, window coating, etc. Properties of TCO differ from one technique to another because of various process parameters involved during the deposition or post-deposition treatment of these films. But for all, the aim is to achieve best physical and chemical properties. Among the metal oxide semiconductors, it seems that In2O3: Sn (ITO) thin films are most promising materials as they exhibit better opto-electronic properties. Therefore, in this chapter, In203 and ITO films were selected as the base materials for preparation of thin films of transparent conducting coatings.

Transparent conducting tin oxide films were prepared by an electron beam evaporation technique. As-deposited films were amorphous or polycrystalline depending on the substrate temperature and the time of deposition. In order to get transparent and conducting thin films of SnO2, as-deposited films were subjected to further heat-treatment in air at 650°C for 2 hours. Physical properties of as-deposited and annealed films are discussed with reference to substrate temperature and deposition time.

A study of a series of chemiplated Cu x S films deposited on varying CdS film structures and under different deposition parameters by electro-chemical analysis was carried out. A morphological model was developed. This study provided a complementary method for distinguishing grain surface and grain boundary growth. Values of grain surface and grain boundary thickness were also evaluated from XPS and XAES depth profiles. A good agreement between the values determined by both approaches illustrated the validity of the model.

This report deals with electrical and structural properties of sprayed CdS films produced under varying process parameters such as pyrolysis temperature, solution concentration and film thickness. The number of traps appears to depend on the structural quality factor of the CdS films. However, electrical properties are dependent on the presence of oxygen or cadmium in the grain boundaries, which significantly alters the grain boundary potential barrier and hence the mobility.