An economic CVD technique for pure SnO 2 thin films deposition: Temperature effects

A modified new method of CVD for formation of pure layers of tin oxide films was developed. This method is very simple and inexpensive and produces films with good electrical properties. The effect of substrate temperature on the sheet resistance, resistivity, mobility, carrier concentration and transparency of the films has been studied. The best sheet resistance obtained at substrate temperature of 500 °C was about 27 Ω/cm². X-ray diffraction showed that the structure of deposited films was polycrystalline with a grain size between 150–300 Å. The preferred orientation was (211) for films deposited at substrate temperature of about 500 °C. FESEM micrographs revealed that substrate temperature is an important factor for increasing grain size and modifies electrical parameters. UV-visible measurement showed reduction of transparency and bandgap of the layers with increasing substrate temperature.     

Effect of the substrate temperature on the structural, optical and electrical properties of spray-deposited CdS:B films

Boron doped CdS films have been deposited by spray pyrolysis method onto glass substrate temperature in the range of 350–450 °C. And the effect of substrate temperature (T _s) on the structural, electrical and optical properties of the films were studied. The structural properties of boron doped CdS films have been investigated by (XRD) X-ray diffraction techniques. The X-ray diffraction spectra showed that boron doped CdS films are polycrystalline and have a hexagonal (wurtzite) structure. By using SEM analysis, the surface morphology of the films was observed as an effect of the variation of substrate temperature. The substrate temperature is directly related with the shift detected in the band gap values derived from optical of parameters and the direct band gap values were found to be in the region of 2.08–2.44 eV. The electrical studies showed that the film deposited at the substrate temperature 400 °C had high carrier concentration and Hall mobility and minimum resistivity. This resistivity value decreased with increase in temperature up to 400 °C indicating the semiconducting nature of B- doped CdS films. The lattice parameter, grain size, microstrain and dislocation densities were calculated and correlated with the substrate temperature (T _s ).     

Effects of growth temperature on electrical and structural properties of sputtered GaN films with a cermet target

GaN films have been deposited at 100–400 °C substrate temperature on Si (100) and sapphire (0001) substrates by RF reactive sputtering in an (Ar + N₂) atmosphere. A (Ga + GaN) cermet target for sputtering was made by hot pressing the mixed powders of metallic Ga and ceramic GaN. The effects of substrate temperature on the GaN formation and its properties were investigated. The diffraction results showed that GaN films with a preferential (10–10) growth plane had a wurtzite crystalline structure. GaN films became smoother at higher substrate temperature. The Hall effect measurements showed the electron concentration and mobility were 1.04 × 10¹⁸ cm^?3 and 7.1 cm² V^?1 s^?1, respectively, for GaN deposited at 400 °C. GaN films were tested for its thermal stability at 900 °C in the N₂ atmosphere. Electrical properties slightly degraded after annealing. The smaller bandgap of ~3.0 eV is explained in terms of intrinsic defects and lattice distortion.     

Influence of RF power on structural,morphology, electrical,composition and optical properties of Al-doped ZnO films deposited by RF magnetron sputtering

In this study, influence of RF power on the structural, morphology, electrical, composition and optical properties of Al-doped ZnO (ZnO:Al) films deposited by RF magnetron sputtering have been investigated. Films were systematically and carefully investigated by using variety of characterization techniques such as low angle X-ray diffraction, UV–visible spectroscopy, Raman spectroscopy, Hall measurement, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy etc. Low angle X-ray diffraction analysis showed that the films are polycrystalline with hexagonal wurtzite structure and which was further confirmed by Raman spectroscopy analysis. Its preferred orientation shifts from (102) to (002) with increase in RF power. The average grain size was found in the range of 15–21 nm over the entire range of RF power studied. The FE-SEM analysis showed that grain size and surface roughness of ZnO:Al films increase in with increase in RF power. The UV–visible spectroscopy analysis revealed that all films exhibit transmittance >85 % in the visible region. The optical band gap increases from 3.37 to 3.85 eV when RF power increased from 75 to 225 W. Hall measurements showed that the minimum resistivity has been achieved for the film deposited at 200 W. The improvement in the electrical properties may attribute to increase in the carrier concentration and Hall mobility. Based on the experimental results, the RF power of 200 W appears to be an optimum sputtering power for the growth of ZnO:Al films. At this optimum sputtering power ZnO:Al films having minimum resistivity (8.61 × 10^?4 Ω-cm), highly optically transparent (~87 %) were obtained at low substrate temperature (60 °C) at moderately high deposition rate (22.5 nm/min). These films can be suitable for the application in the flexible electronic devices such as TCO layer on LEDs, solar cells, TFT-LCDs and touch panels.     

Influence of annealing temperature on structural,electrical and optical properties of undoped zinc oxide thin films

The undoped zinc oxide thin films were grown on quartz substrate at a substrate temperature of 750 °C by radio frequency magnetron sputtering and post annealed at different temperatures (600–800 °C) for a period of 30 min. The influence of annealing temperature on the structure, electrical and optical properties of undoped ZnO thin films was investigated by X-ray diffraction, Hall-effect, photoluminescence and optical transmission measurements. Results indicated that the electrical properties of the thin films were extremely sensitive to the annealing temperature and the conduction type could be changed dramatically from n-type to p-type, and finally changed to weak p-type when the temperature increased from 600 to 800 °C. Electrical and photoluminescence results indicate that native defects, such as oxygen and zinc vacancies, could play an important role in determining the conductivity of these nominally undoped ZnO thin films. The conversion of the conduction type was attributed to the competition between Zn vacancy acceptor and oxygen vacancy and interstitial Zn donors. At an intermediate annealing temperature of 750 °C, the film behaves the best p-type characteristic, which has the lowest resistivity of 12 Ωcm, hall mobility of 2.0 cm²/V s and carrier concentration of 1.5 × 10¹⁷ cm^?3. The photoluminescence results indicated that the Zn vacancy might be responsible for the intrinsic better p-type characteristic in ZnO thin films.     

Properties of pulse electrodeposited copper indium selenide films

Copper Indium Selenide films were deposited by the pulse plating technique at different bath temperatures in the range of 30–80 °C and at 50 % duty cycle (15 s ON and 15 s OFF). X-ray diffraction studies indicated the formation of single phase chalcopyrite copper indium selenide films. The band gap of the films decreased from 1.17 to 1.05 eV with decrease of duty cycle. Atomic force microscope studies indicated that the surface roughness and grain size increased with duty cycle. Room temperature resistivity of the films is in the range of 0.01–2.0 ohm cm. Films deposited at 50 % duty cycle have exhibited a V_oc of 0.59 V, J_sc of 15 mA cm^?2, FF of 0.75 and efficiency of 6.64 %.     

Dependence of structural, optical and electrical properties on substrate temperature for hexagonal MgxZn1−xO films

Single hexagonal-phase Mg_xZn_1?xO films were deposited on glass substrates by pulsed laser deposition from a ZnO target mixed with MgO. The effect of substrate temperature on the structural, electrical and optical properties was investigated by X-ray diffraction and the transmittance measurements. It was observed that Mg incorporation lead to a clear shift of the (002) peak position to lower angle with reference to pure ZnO films due to the residual stress change with deposition temperature. It was also found that Mg doping increased the resistivity by 2 orders of magnitude and the maximum resistivity was 0.072 Ω·cm at 550 °C with the carrier concentration of 1.1 × 10¹⁹ cm^?3. The visible transmittance of above 80 % was obtain in the alloy films, which optical band gap was observed to increase with the substrate temperature, attaining 3.85 eV at 600 °C. The possible mechanism was discussed.     

Structural,optical and electrical properties of SnO<Subscript>2</Subscript>:F thin films deposited by spray pyrolysis for application in thin film solar cells

Fluorine doped tin oxide (FTO) thin films with adequate properties to be used as transparent electrical contact for PV solar cells were synthesised using the spray pyrolysis technique, which provides a low cost operation. The deposition temperature and the fluorine doping have been optimized for achieving a minimum resistivity and maximum optical transmittance. No post-deposition annealing treatments were carried out. The X-ray diffraction study showed that all the FTO films were polycrystalline with a tetragonal crystal structure and preferentially oriented along the (200) direction. The grain size ameliorates with the increase in substrate temperature. The samples deposited with the substrate temperature at 440 °C and fluorine content of 20 wt % exhibited the lowest electrical resistivity (1.8 × 10^?4 Ω cm), as measured by four-point probe. Room-temperature Hall measurements revealed that the 20 wt% films are degenerate and exhibit n-type electrical conductivity with carrier concentration of ~4.6 × 10²⁰ cm^?3, sheet resistance of 6.6 Ω/□ and a mobility of ~25 cm² V^?1 s^?1. In addition, the optimized growth conditions resulted in thin films (~500 nm thickness) with average visible transmittance of 89 % and optical band-gap of 3.90 eV. The electrical and optical characteristics of the deposited films revealed their excellent quality as a TCO material.     

Structural, optical, and electrical properties of indium-doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition

Indium-doped cadmium oxide (CdO:In) films were prepared on glass and sapphire substrates by pulsed filtered cathodic arc deposition (PFCAD). The effects of substrate temperature, oxygen pressure, and an MgO template layer on film properties were systematically studied. The MgO template layers significantly influence the microstructure and the electrical properties of CdO:In films, but show different effects on glass and sapphire substrates. Under optimized conditions on glass substrates, CdO:In films with thickness of about 125 nm showed low resistivity of 5.9 × 10^?5 Ωcm, mobility of 112 cm²/Vs, and transmittance over 80 % (including the glass substrate) from 500 to 1500 nm. The optical bandgap of the films was found to be in the range of 2.7 to 3.2 eV using both the Tauc relation and the derivative of transmittance. The observed widening of the optical bandgap with increasing carrier concentration can be described well only by considering bandgap renormalization effects along with the Burstein–Moss shift for a nonparabolic conduction band.     

P-type semiconducting Cu2O–NiO thin films prepared by magnetron sputtering

P-type semiconducting thin films consisting of a new multicomponent oxide composed of Cu₂O and NiO were deposited on glass substrates by r.f. magnetron sputtering using Cu₂O–NiO mixed powder targets. The multicomponent oxide thin films deposited in an Ar atmosphere with a Ni content (Ni/(Cu + Ni) atomic ratio) in the range from 0 to 100 at.% were found to be p-type semiconductors. As the Ni content was increased in the range from 0 to about 30 at.%, the energy bandgap of the resulting films gradually increased as well as the obtained resistivity increased from 70 to 4 × 10⁴ Ω cm, a consequence of decreases in both the Hall mobility and the hole concentration. The films prepared with a Ni content of about 30–50 at.% exhibited a relatively constant resistivity and energy bandgap. The resistivity and the energy bandgap of films prepared with a Ni content above about 60 at.% considerably increased as the Ni content was increased. Furthermore, a pn thin-film heterojunction prepared by depositing undoped n-ZnO and p-multicomponent oxide (Ni content of 50 at.%) thin films exhibited a rectifying I–V characteristic.     

Influence of incorporation of Al3+ ions on the structural, optical and AC impedance characteristics of spin coated ZnO thin films

Aluminium doped zinc oxide thin films were deposited onto glass substrate using spin coating technique. The effects of Al doping on structural, optical and electrical properties of these films were investigated. X-ray diffraction analysis showed that all the thin films were of polycrystalline hexagonal wurtzite structure with (002) as preferential orientation except 2 at.% of Al doped ZnO films. The optical band gap was found to be 3.25 eV for pure ZnO film. It increases up to 1.5 at.% of Al doping (3.47 eV) and then decreased slightly for the doping level of 2 at.% (3.42 eV). The reason for this widening of the optical band gap up to 1.5 at.% is well described by Burstein–Moss effect. The photoluminescence spectra of the films showed that the blue shift and red shift of violet emission were due to the change in the radiative centre between zinc vacancy and zinc interstitial. Variation in ZnO grain boundary resistance against the doping concentration was observed through AC impedance study.     

Annealing effect on the structural,electrical and 1/f noise properties of Mn–Co–Ni–O thin films

Thin films of Mn_1.4Co_1.0Ni_0.6O₄ (MCN) spinel oxide are grown by radio frequency (RF) magnetron sputtering method on amorphous Al₂O₃ substrate. We investigate the annealing effect on the micro structural and electrical properties of RF sputtered MCN films. It is found that the crystallinity of MCN film is improved with increasing annealing time at 750 °C, and the annealed films present excellent cubic spinel (220) preferred orientation in X-ray diffraction patterns. Comparing to as-sputtered thin film, the annealed films show a decrease of 60 to 70 % in resistivity at 300 K. The annealed samples with post annealing time longer than 18 min acquire a negative temperature coefficient of resistance of about ?3.73 %K^?1 and resistivity of about 210–220 Ω cm at 300 K. 1/f noise of MCN films are also studied and the Hooge’s parameters (γ/n) are calculated. After annealing for 18 to 90 min, the γ/n values of the films are on the order of 10^?21 cm³, which ranks about two orders lower than that of amorphous silicon.     

The properties of Al doped ZnO thin films deposited on various substrate materials by RF magnetron sputtering

Transparent conductive Al-doped ZnO (AZO) thin films were deposited on various substrates including glass, polyimide film (PI) and stainless steel, using radio frequency magnetron sputtering method. The structural, electrical and optical properties of AZO thin films grown on various substrates were systematically investigated. We observe that substrate materials play important roles in film crystallization and resistivity but little on optical transmittance. X-ray diffractometer study shows that all obtained AZO thin films have wurtzite phase with highly c-axis preferred orientation, and films on glass present the strongest (002) diffraction peaks. The presence of compression stress plays critical role in determining the crystalline structure of AZO films, which tends to stretch the lattice constant c and enlarge the (002) diffraction angle. Although the films on the glass present the finest electrical properties and the resistivity reaches 12.52 × 10-4 Ωm, AFM study manifests that films on flexible substrates, especially stainless steel, bestrew similar inverted pyramid structure which are suitable for window material and electrode of solar cells. The average optical transmittance of AZO thin films deposited on glass and PI are both around 85% in the visible light range (400–800 nm).     

Influence of substrate temperature on the physical properties of thermally evaporated nanocrystalline bismuth sulfide thin films

Nanocrystalline bismuth sulfide thin films were deposited on glass substrate by thermal evaporation technique using the solvothermally synthesized nanometer-sized bismuth sulfide powder as the source material. X-ray diffraction (XRD) analysis revealed that the films are polycrystalline in nature with orthorhombic structure. The crystallinity of the thin films improved with substrate temperature, and the estimated crystallite size are in the nanometer regime. Scanning electron microscope (SEM) analysis showed homogenous distribution of grains with well defined grain boundaries. The optical transmittance of the nanocrystalline bismuth sulfide thin films increases with the increase in substrate temperature, and the optical transition was found to be direct and allowed. The estimated optical band gap energy was found to decrease with the increase in substrate temperature. The electrical resistivity of the bismuth sulfide thin films is of the order of 10⁻⁴ Ω-cm and exhibits semiconductor nature. Experimental results demonstrate that the structural, optical and electrical properties of bismuth sulfide thin films have strong dependence on the substrate temperature.     

Effects of substrate temperatures on the thermal stability of Al-doped ZnO thin films grown by DC magnetron sputtering

In this work, Al-doped (4 at%) ZnO(AZO) thin films were prepared by DC magnetron sputtering using a home-made ceramic target at different substrate temperatures. The microstructure, optical, electrical and thermal stability properties of these thin films were characterized systematically using scanning electron microscopy, UV–Vis-NIR spectrometry, X-ray diffraction, and Hall measurements. It was observed that the AZO thin films deposited at 350 °C exhibited the lowest resistivity of 5.76 × 10⁻⁴ Ω cm, high average visible transmittance (400–800 nm) of 92%, and the best thermal stability. Comparing with the AZO thin films deposited at low substrate temperatures, the AZO thin films deposited at 350 °C had the highest compact surface morphology which could hinder the chemisorbed and diffused oxygen. This was considered to be the main mechanism which was responsible for the thermal degradation of AZO thin films.     

Effect of firing temperature on microstructure and dielectric properties of chromium oxide based glass composite thick films on stainless steel substrate

We report the influence of firing temperature on Al₂O₃–chromium oxide based (Cr₂O₃–Bi₂O₃–B₂O₃–SiO₂–Al₂O₃) glass composite (named as GC-1 composite) thick films of thickness (27?±?3) µm deposited onto 0.6 mm thick austenitic grade stainless steel (DIN 1.4301/AISI 304) substrate by screen printing technique, which can be used as a substitute to alumina substrate. Prior to formulation of glass composite, the chromium oxide based glass (named as GC-1) phase was prepared separately by melt-quench technique. X-ray diffraction analysis confirmed amorphous nature of the GC-1 glass. The thermo gravimetric analysis and differential scanning calorimetry of the GC-1 glass shows thermal stability over the temperature range of 20–1000 °C. We observed that the firing temperature significantly influences microstructural and dielectric properties of the GC-1 composite film. The deposited GC-1 composite films onto stainless steel base were fired at temperatures between the range of 550–750 °C, showed the surface resistivity in the range of (1.0–6.9?±?0.2) × 10¹² ohms per square. The microstructure of these composite films recorded using scanning electron microscopy and electrical properties recorded using LCR meter were correlated with each other. The study revealed that the film fired at 600 °C were found to be superior among the samples under investigation in terms of microstructure, stable relative permittivity [36 (±?1)] and low loss tangent [0.02 (±?0.002)] in frequency range of 1–200 kHz, and surface resistivity (~?5.1?×?10¹² ohms per square).     

Nanocrystalline copper selenide thin films by chemical spray pyrolysis

Thin films of copper selenide were deposited onto amorphous glass substrates at various substrate temperatures by computerized spray pyrolysis technique. The as deposited copper selenide thin films were used to study a wide range of characteristics including structural, surface morphological, optical and electrical, Hall Effect and thermo-electrical properties. X-ray diffraction study reveals that the films are polycrystalline in nature with hexagonal (mineral klockmannite) crystal structure irrespective of the substrate temperature. The crystalline size is found to be in the range of 23–28 nm. The SEM study reveals that the grains are uniform with uneven spherically shaped and spread over the entire surface of the substrates. EDAX analysis confirmed the nearly stoichiometric deposition of the film at 350 °C. The direct band gap values are found to be in the range 2.29–2.36 eV depending on the substrate temperature. The Hall Effect study reveals that the films exhibit p-type conductivity. The values of carrier concentration and mobility for the film are found to be 5.02 × 10¹⁷ cm^?3 and 5.19 × 10^?3 cm² V^?1 s^?1; respectively for film deposited at 350 °C.     

Preparation and characterization of ZnS nanocrystalline thin films by low cost dip technique

Nanocrystalline ZnS semiconducting nanopowder and thin films have been deposited by simple low cost technique based on combination of dip coating and thermal reaction process. The deposited films and the prepared nanopowder have been characterized in the structurally, optically and electrically point of views. The effect of preparation conditions has been also optimized for good quality films. X-ray diffraction analysis performed the ZnS cubic phase in the reaction temperatures in the range 473–593 K. Above 593 K mixed cubic and hexagonal crystallographic phases have been resolved. Crystallite size and micro strain have been calculated to be 2.65 and 0.011 nm, respectively. The deposited film surface and cross section morphologies show that neither cracks nor peels have been observed and good film adhesion with the substrate was performed. Energy dispersive X-ray measurements of the film agree well with the calculated concentrations of the precursor components. Optical measurements confirm the optical characteristics of nanocrystalline ZnS film such as absorption and dispersion properties. Copper doped ZnS reduces the band gap while indium doped ZnS increases the band gap. Electrical characterization shows that copper doped ZnS increases the resistivity by one order of magnitude due to electron compensation process while indium doped ZnS decreases the resistivity three orders of magnitude due to increase of the carriers concentration. Hot probe thermoelectric quick test of ZnS:Cu and ZnS:In show opposite sign of thermoelectric voltage due to bipolar p and n types, respectively.     

Effect of substrate temperature on structural, morphological and optical properties of crystalline titanium dioxide films prepared by DC reactive magnetron sputtering

Titanium dioxide (TiO₂) thin films have been deposited with various substrate temperatures by dc reactive magnetron sputtering method onto glass substrate. The effects of substrate temperature on the crystallization behavior and optical properties of the films have been studied. Chemical composition of the films was investigated by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) analysis of the films revealed that they have polycrystalline tetragonal structure with strong (101) texture. The surface morphological study revealed the crystalline nature of the films at higher substrate temperatures. The TiO₂ films show the main bands in the range 400–700 cm^?1, which are attributed to Ti–O stretching and Ti–O–Ti bridging. The transmittance spectra of the TiO₂ thin film measured with various substrate temperatures ranged from 75 to 90 % in the visible light region. The optical band gap values of the films are increasing from 3.44 to 4.0 eV at growth temperature from 100 to 400 °C. The structural and optical properties of the films improved with the increase in the deposition temperature.     

CuInGaSe2 crystals synthesis by selenization of Cu–In–Ga alloy in H2Se atmosphere for solar cell applications

Copper indium gallium diselenide (CuInGaSe₂) crystals were synthesized using two step growth strategy. A facile solution route was employed as a primary step to synthesize Cu–In–Ga (CIG) metallic precursor using ethylenediamine as a solvent. Thin films of CIG metallic precursor have been deposited using spray deposition technique on to molybdenum coated soda lime glass substrate under inert atmosphere. The subsequent step involved the selenization of metallic precursor thin films in H₂Se atmosphere at 450 °C for 90 min followed by annealing in Ar thus yielding solar cell applicable dense CuInGaSe₂ crystals. The surface morphology, phase structure and composition of the deposited films were analyzed by field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and electrical resistivity measurement respectively. The results revealed that annealed films were crystalline in nature exhibiting homogeneous single chalcopyrite phase.