Browsing by Author "Mokeddem, Kamel"

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    Effect of nitrogen mole fraction on hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering: transition between metallic and reactive sputtering
    (Wiley Online Library, 2014) Mokeddem, Kamel; Kechouane, Mohamed
    The hydrogenated amorphous silicon nitride thin films are deposited by DC magnetron sputtering in argon, molecular hydrogen and nitrogen plasma mixture. The films are deposited at 150 °C and at 130 W sputtering power with wide range of nitrogen mole fraction. The plasma is characterized by the target voltage measurement. The samples are characterized by the optical transmission measurements and the physicochemical structure is studied by the FTIR absorption spectroscopy. When the nitrogen mole fraction increases from 0.075 to 0.24 the target voltage decrease from 413 to 325 V and increases suddenly to 450 V when nitrogen mole fraction increases to 0.69. The decrease of target voltage may be due to the transition from metallic to reactive sputtering process and its increase can be explained by the implantation of reactive ions in the target. Sputtering rate and refractive index decrease respectively from 8.33 to 1.73 Å/sec and from 2.52 to 1.68 with nitrogen mole fraction. The value of refractive index at critical nitrogen mole fraction is about 1.8. When the nitrogen mole fraction increases the frequency related to Si-H band, on FTIR spectrum, shift from 2097 cm-1 to reach 2209 cm-1 at the critical nitrogen mole fraction. Thereafter it varies sharply to 2190 cm-1 and remains constant. A sudden change is observed on the sputtering rate, on the intensity of the band attributed to the stretching vibration of N-H and Si-H bonds. From these results we believe that the stoichiometric composition is reached at the critical nitrogen mole fraction and beyond this the deposited films are rich of nitrogen and hydrogen. This is consistent with the explanation given of the variation of the target voltage. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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    Effect of TiN thin films deposited by oblique angle sputter deposition on sol-gel coated TiO2 layers for photocatalytic applications
    (Elsevier, 2024) Naas, Lazhari-Ayoub; Bouaouina, Boudjemaa; Bensouici, Fayçal; Mokeddem, Kamel; Abaidia, Seddik-El-Hak
    TiO2 monolayer and TiN/TiO2 bilayer coatings were deposited on soda-lime glass prepared by mixing two techniques, TiO2 was deposited by sol-gel dip-coating and TiN film was deposited by oblique angle deposition using reactive magnetron sputtering at α=45° Structural analysis showed typical peaks of TiO2 anatase phase and cubic (Na-Cl type) structure of TiN. Roughness value of 3 nm was obtained for the TiN/TiO2 bilayer film with a rise and elongated grains size. It was found that the optical band gap energy decreases after coupling the TiN sub-layer which is explained by the incorporation of N atoms into TiO2 structure. At constant UV irradiation time, the photo-degradation of methylene blue rate increased for TiN/TiO2 film by 4 % compared to TiO2 film
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    Hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering
    (Elsevier, 2006) Mokeddem, Kamel; Aoucher, M.; Smail, T.
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    Negative capacitance in Aluminum/hydrogenated amorphous silicon nitride/n type crystalline silicon structure
    (Elsevier, 2015) Mokeddem, Kamel; Kechouane, Mohamed
    The dynamic admittance of Al/a-SiNx:H/n-c-Si structure as function of bias voltage (V) and frequency (ω) have been investigated in wide ranges of frequency (300 Hz–1 MHz) and bias voltage (0–9 V) respectively at room temperature. Negative capacitance (NC) behavior has been observed at forwards bias voltages. It appears from value of bias voltage which depends on the frequency. This value corresponds on the current–voltage characteristics at the beginning bias voltage of thermionic emission regime of electrical conduction. Therefore the injection of electrons at a-SiNx:H/n-c-Si interface by thermionic emission may be involved in the NC mechanism. In C−ω plot, a strong peak of NC has been observed at low-frequency, its intensity is about 110 times the geometrical capacitance. The frequency and the intensity of the NC peak show a linear variation versus a square root of bias voltage in semi logarithmic representation. The NC behavior is always accompanied with relatively high conductance “G/ω”