Improved Cu2O/AZO Heterojunction by Inserting a Thin ZnO Interlayer Grown by Pulsed Laser Deposition

Cu2O/ZnO:Al (AZO) and Cu2O/ZnO/AZO heterojunctions have been deposited on glass substrates by a unique three-step pulsed laser deposition process. The structural, optical, and electrical properties of the oxide films were investigated before their implementation in the final device. X-ray diffraction analysis indicated that the materials were highly crystallized along the c-axis. All films were highly transparent in the visible region with enhanced electrical properties. Atomic force and scanning electron microscopies showed that the insertion of a ZnO layer between the Cu2O and AZO films in the heterojunction enhanced the average grain size and surface roughness. The heterojunctions exhibited remarkable diode behavior and good rectifying character with low leakage current under reverse bias. The presence of the ZnO interlayer film significantly reduced the parasitic and leakage currents across the barrier, improved the quality of the heterostructure, made the energy band between AZO and Cu2O layers smoother, and eliminated the possibility of interface recombination, leading to much longer electron lifetime

Characterization of An Expansive Clay Treated with Lime: Effect of Compaction on The Swelling Pressure

This work focuses on the study of the compaction effect on the stabilization of a highly expansive clay soil by adding lime. To this end, we used two types of swelling clay soils, the first one is intact and the other derivative (reconstituted, prepared from a natural soil and bentonite mixture with the following proportions: 70 and 30%. The results of the recorded oedometric tests show that the incorporation of the lime reduces the soil swelling pressures at each dosing lime in agreement with many reported previous studies. The contents of lime greatly affect swelling; indeed for a dosage of 6% lime the swelling pressures are reduced by 27% for the sample of disturbed soil. The compaction test performed on the reconstituted incorporated lime soil shows that for a dosage of 2% lime, we have a reduction of the swelling pressure of 96%

Effect of nitrogen mole fraction on hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering: transition between metallic and reactive sputtering

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

Negative capacitance in Aluminum/hydrogenated amorphous silicon nitride/n type crystalline silicon structure

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

Quenched-in Defects in CW Laser Irradiated Virgin Silicon.

ABSTRACTQuenched-in defects in cw laser irradiated silicon have been identified using deep level transient spectroscopy. Four among the five dominant defect states arise from transition metal impurities (iron, chromium) present in precipitates in the as-grown material and dispersed into the crystal upon heat treatment. Native defects are involved in the form of phosphorous-vacancy complexes, which account for the remaining level.</jats:p

Photocatalysis of rhodamine B and methyl orange degradation under solar light on ZnO and Cu2O thin films

We report the photocatalytic properties of ZnO and Cu2O thin films deposited on glass substrates at room temperature by DC sputtering and pulsed laser deposition. The photoactivity of the films was investigated through the degradation of rhodamine B (RhB) and methyl orange (MO) under solar light. In order to select the most suitable film of ZnO for the of RhB and MO degradation, the relationship between the characteristics (e.g. energy levels and defects concentration) of ZnO films and their effectiveness in the photocatalytic yield of RhB and MO been studied, where several films were deposited by using different oxygen partial pressures (PO2: 0.05–1.3&nbsp;mbar), while Cu2O films were grown under a pressure of 0.01&nbsp;mbar. The XRD patterns show that all ZnO films have (002) preferential orientation, and crystallite size increases from 73 to 122&nbsp;nm raising PO2. The gap Eg of ZnO (3.26 and 4.15&nbsp;eV) depends on PO2, and the films present photoluminescence emission in the UV–Vis-near IR region. On the basis of structural, optical and electrical characterizations of both films, a comparative study was carried out on the dyes degradation. Cu2O films exhibit a high photoactivity with MO (81.69%) under solar light (6&nbsp;h), whilst for RhB the best elimination rate (60.85%) was achieved with ZnO films deposited at 0.1&nbsp;mbar, which were also the ones exhibiting the highest PL peak intensity at the characteristic absorption wavelength of RhB (553&nbsp;nm)