Okba Belahssen

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.

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.

The calculation of band gap energy in zinc oxide films

We investigated the optical properties of undoped zinc oxide thin films as the n-type semiconductor; the thin films were deposited at different precursor molarities by ultrasonic spray and spray pyrolysis techniques. The thin films were deposited at different substrate temperatures ranging between 200 and 500 ℃. In this paper, we present a new approach to control the optical gap energy of ZnO thin films by concentration of the ZnO solution and substrate temperatures from experimental data, which were published in international journals. The model proposed to calculate the band gap energy with the Urbach energy was investigated. The relation between the experimental data and theoretical calculation suggests that the band gap energies are predominantly estimated by the Urbach energies, film transparency, and concentration of the ZnO solution and substrate temperatures. The measurements by these proposal models are in qualitative agreements with the experimental data; the correlation coefficient values were varied in the range 0.96–0.99999, indicating high quality representation of data based on Equation (2), so that the relative errors of all calculation are smaller than 4%. Thus, one can suppose that the undoped ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition and contained higher optical band gap energy.

Corrosion and wear resistance of 32CrMoV13 steel nitrided by plasma

This paper presents corrosion and wear behavior of the plasma-nitrided 32CrMoV13 steel. Untreated and plasma nitrided samples were tested. The structure of layers was determined by X-ray diffraction, the morphology was observed by scanning electron microscopy (SEM). The corrosion behavior was evaluated by electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy). The corrosion tests were carried out in acid chloride solution (HCl 1 M). The plasma nitriding behaviors of 32CrMoV13 steel have been assessed by evaluating tribological properties and surface hardness by using a pin-on-disk wear machine and microhardness tester. Experimental results showed that the nitrides e-Fe2-3N and γ′-Fe4N present in the white layer are nobler than the substrate but may promote, by galvanic effect, a localized corrosion through open porosity. Better corrosion protection was observed for the nitrided sample. It is found that plasma nitriding improves the wear rate, and the presence of a hard and brittle compound layer on the surface causes an increase in wear of the specimen surface.

Effect of Urbach energy with precursor molarity on the crystallite size in undoped ZnO thin film

We investigated the structural and optical properties of ZnO thin films as the n-type semiconductor, the thin films were deposited at different precursor molarities by ultrasonic spray method on glass substrate at 350 ◦ C, as discussed in our published paper. In this paper we focused our attention on the present a new approach to the description of correlation between crystallite size and Urbach energy with precursor molarities, this correlation based on experimental data of our study previously published. The correlation between structural and optical properties with precursor molaritie was investigated. The measurement of the crystallite sizes of undoped ZnO thin films were realized at different model proposals; these measurements shows that the crystallite sizes of the films can be estimated by varying the Urbach energy and the concentration of ZnO solution, which are in qualitative agreements with the experimental data. The best estimate result is measured by Equation (9) with minimum relative errors values were limited to 1 %. Thus results indicate that the ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition.

Effect of heat treatments on structural, microstructural and mechanical properties of Al 2017 alloy

The effect of ageing at 300°C before and after quenched at two temperatures of 180 and 280°C on the Al 2017 alloy was studied. The structural properties were investigated using X-ray diffraction; the microstructural evolution was investigated using scanning electron microscopy and microhardness measurement for the mechanical properties. After various states of ageing, the Al–Cu–Fe alloy shows significant changes in the microstructure and mechanical behavior. After ageing, the microstructure of the matrix consisted of a three solid solution of α-Al–Cu-Fe, β-AlFe and θ-A2Cu phases precipitations. After two-step heat treatment (quenching and ageing), the alloy reveals the formation of β and θ phases precipitates. After ageing at 300°C of original sample, the alloy reveals higher β precipitates, corresponding to the minimum value of microhardness, the volume fraction of this precipitates becomes higher. On the other hand, the TTT curves for the discontinuous and continuous precipitation reaction in this alloy have been suggested.

Effect of crystallite size and precursor molarities on electrical conductivity in ZnO thin films

In present paper, ZnO thin films were deposited using the simple, flexible and cost-effective spray ultrasonic technique at different precursor molarity values. The films deposited on glass substrate at 350 °C. The electrical and structural properties were studied as a function of precursor molarity. The as sprayed films exhibit an hexagonal structure wurtzite and (002) oriented with the maximum value of crystallite size G = 31.82 nm is measured of ZnO film sprayed with 0.1 M. The crystallites size in the thin films depend by the defect (less defects), where the minimum defects confirmed the high crystallinity. The maximum value of electrical conductivity of the films is 7.96 (Ω.cm)-1 obtained in ZnO thin film for precursor molarity 0.125 M. The correlation between the electrical and the structural properties with the precursor molarity suggests that the electrical conductivity of the films is predominantly influenced by the crystallite size and the precursor molarity. The measurement in the electrical conductivity of the films with correlation it is equal to the experimental with the error is about 0.3 % in the higher conductivity.