Said Benramache

Influence of growth time on crystalline structure, conductivity and optical properties of ZnO thin films

This paper examines the growth of ZnO thin films on glass substrate at 350 °C using an ultrasonic spray technique. We have investigated the influence of growth time ranging from 1 to 4 min on structural, optical and electrical properties of ZnO thin films. The as-grown films exhibit a hexagonal structure wurtzite and are (002) oriented. The maximum value of grain size G = 63.99 nm is attained for ZnO films grown at 2 min. The average transmittance is about 80%, thus the films are transparent in the visible region. The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min. The minimum value of electrical resistivity of the films is 0.13 Ωcm obtained at 2 min. A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350 °C has been reported.

Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater

The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s−1. Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s−1 with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency.

Effect of substrate temperature on the stability of transparent conducting cobalt doped ZnO thin films

Transparent conducting Co doped ZnO thin films have been fabricated by Ultrasonic spray. The thin films were deposited at three different substrate temperatures of 300, 350 and 400 °C. The obtained films had a hexagonal wurtzite structure with a strong (002) preferred orientation. The maximum crystallite size value of the film deposited at 350 °C is 55.46 run. Spectrophotometer (UV-vis) of a Co doped ZnO film deposited at 350 °C shows an average transmittance of about 90%. The band gap energy increased from 3.351 to 3.362 eV when the substrate temperature increased from 300 to 350 °C. The electrical conductivity of the films deposited at 300, 350 and 400 °C were 7.424, 7.547 and 6.743 (Ω·cm)−1 respectively. The maximum activation energy value of the films at 350 °C was 1.28 eV, indicating that the films exhibit a n-type semiconducting nature.

Preparation of transparent, conductive ZnO:Co and ZnO:In thin films by ultrasonic spray method

This paper examines the growth of undoped and doped thin films with (Co and In) on glass substrate at 350°C using ultrasonic spray technique. We have investigated the influence of doping concentrations ranging from 0 to 4 wt.% on structural, optical, and electrical properties of ZnO thin films. Zinc acetate dehydrate, CoCl3 4H2O or InCl3, ethanol, and monoethanolamine were used as a starting materials, dopant source, solvent, and stabilizer, respectively. The X-ray diffraction analysis indicated that the undoped and doped ZnO thin films have polycrystalline nature and hexagonal wurtzite structure with (002) preferential orientation. The maximum average crystallite sizes of ZnO:Co and ZnO:In were 55.46 and 45.78 nm at concentrations of 2 wt.% Co and 3 wt.% In, respectively, indicating that the crystallinity of doped films improved after doping. The optical absorption spectra showed that all undoped and doped ZnO films are transparent within the visible wavelength region. The band gap energy of ZnO:Co thin films increased after doping from 3.25 to 3.36 eV; however, the optical gap of ZnO:In decreases after doping from 3.25 to 3.18 eV, indicating the increase and decrease, respectively, in the transition tail width. The electrical conductivity of doped films is stabilized after doping. Transparent, conductive Co-doped ZnO thin films deposited by ultrasonic spray technique are of good quality.

Preparation of transparent conducting ZnO：Al films on glass substrates by ultrasonic spray technique

Transparent conductive Al doped ZnO thin films were deposited by ultrasonic spray technique. Conditions of preparation have been optimized to get good quality. A set of aluminum (Al) doped ZnO (between 0 and 5 wt%) thin films were grown on glass substrate at 350 °C. Nanocrystalline films with a hexagonal wurtzite structure show a strong (002) preferred orientation. The maximum value of grain size G = 32.05 nm is attained of Al doped ZnO film with 3 wt%. All the films have low absorbance in the visible region, thus the films are transparent in the visible region; the band gap energy increased from 3.10 to 3.26 eV when Al concentration increased from 0 to 3 wt%. The electrical conductivity of the films increased from 7.5 to 15.2 (Ωcm)−1. So the best results are achieved in Al doped ZnO film with 3 wt%.

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin (II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2:F thin films were deposited at a 350 °C pending time (5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9 (Ωcm)−1 for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.

Correlation between electrical conductivity—optical band gap energy and precursor molarities ultrasonic spray deposition of ZnO thin films

ZnO thin films were deposited using the simple, flexible and cost-effective spray ultrasonic technique at different precursor molarities values. The films were deposited on a glass substrate at 350 °C. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with precursor molarity of ZnO thin films. The ZnO films exhibit higher electrical n-type semiconductors, whose band gap energy increased from 3.08 to 3.37 eV with an increasing of precursor molarity of 0.05 to 0.1 M. The maximum value of electrical conductivity of the films is 7.96 (ωcm)−1 obtained in the ZnO thin film for precursor molarity 0.125 M. The correlation between the electrical and the optical properties with the precursor molarity suggests that the electrical conductivity of the films is predominantly influenced by the band gap energy and the precursor molarity. The measurement of the electrical conductivity of the films with correlation is equal to the experimental with the error is about 1% in the higher conductivity.

Correlation between crystallite size-optical gap energy and precursor molarities of ZnO thin films

We investigated the structural and optical properties of ZnO thin films as an n-type semiconductor. The films were deposited at different precursor molarities using an ultrasonic spray method. In this paper we focused our attention on a new approach describing a correlation between the crystallite size and optical gap energy with the precursor molarity of ZnO thin films. The results show that the X-ray diffraction (XRD) spectra revealed a preferred orientation of the crystallites along the c-axis. The maximum value of the crystallite size of the films is 63.99 nm obtained at 0.1 M. The films deposited with 0.1 M show lower absorption within the visible wavelength region. The optical gap energy increased from 3.08 to 3.37 eV with increasing precursor molarity of 0.05 to 0.1 M. The correlation between the structural and optical properties with the precursor molarity suggests that the crystallite size of the films is predominantly influenced by the band gap energy and the precursor molarity. The measurement of the crystallite size by the model proposed is equal to the experimental data. The minimum error value was estimated by Eq. (4) in the higher crystallinity.

Structural, optical and electrical properties of zinc oxide thin films deposited by a spray pyrolysis technique

Zinc oxide (ZnO) thin films were deposited on glass substrates by spray pyrolysis technique decomposition of zinc acetate dihydrate in an ethanol solution with 30 mL of deposition rate, the ZnO thin films were deposited at two different temperatures: 300 and 350 °C. The substrates were heated using the solar cells method. The substrate was R217102 glass, whose size was 30 × 17.5 × 1 mm3. The films exhibit a hexagonal wurtzite structure with a strong (002) preferred orientation. The higher value of crystallite size is attained for sprayed films at 350 °C, which is probably due to an improvement of the crystallinity of the films at this point. The average transmittance of obtain films is about 90%–95%, as measured by a UV—vis analyzer. The band gap energy varies from 3.265 to 3.294 eV for the deposited ZnO thin film at 300 and 350 °C, respectively. The electrical resistivity measured of our films are in the order 0.36 Ωcm.

Study on the correlation between crystallite size and optical gap energy of doped ZnO thin film

In the present paper, we have studied a new approach to the description ofcorrelation between the optical and structural properties of ZnO thin films withdoping levels of Al, Co, and In. The doped zinc oxide thin films were depositedusing ultrasonic spray technique on a glass substrate at 350°C. Thecorrelation between structural and optical properties with doping level suggeststhat the crystallite size of the films is predominantly estimated by the bandgapenergy and the concentration of Al, Co, and In. Also, the gap energy of dopedfilms was estimated by the crystallite size and doping level. The measurement inthe crystallite size and optical gap energy of doped films with correlation isequal to the experimental data. The minimum error value was estimated in dopedZnO thin films with indium and cobalt. Thus, results indicate that such Co-dopedZnO thin films are chemically purer and have many fewer defects and lessdisorder, owing to an almost complete chemical decomposition.