Electronic structure and optical response for Zn1−xBexSe

The electronic structures and optical properties of the Zn1−xBexSe semiconductor ternary alloys have been investigated by using the full-potential linear augmented plane wave (FP-LAPW) method. From this study, the energy band gap has a value of about 1.2 eV for zinc-blende ZnSe. However, for Zn0.50Be0.50Se and BeSe, the fundamental band gap energy is found to occur at the highly symmetric X point in the Brillouin zone and has values of about 2.3 eV and 2.8 eV, for Zn0.50Be0.50Se and BeSe, respectively. Optical parameters, such as dielectric constant, refractive index and reflectivity are calculated and analyzed. The results demonstrated that the compounds Zn1−xBexSe have the potential to be used for optoelectronic applications. Keywords: Band structure, Optical properties, Zn1−xBexSe alloys, FP-LAPW metho

Thermally induced changes in optical and electrical properties of SnSb

Sulfosalt SnSb2S4 films for optical and electrical applications have been prepared on glass substrates by thermal evaporation and subsequently thermally annealed in vacuum at temperatures from 100 to 200 °C. The optical and structural properties of the films were studied as a function of the annealing temperature. The SnSb2S4 films exhibit a polycrystalline structure and undergo abrupt changes in electrical and optical properties at a transition temperature of 140 °C. After annealing below the transition temperature, the films are highly resistive with a dominant amorphous component, but when annealed above this temperature, the samples exhibit p+-type semiconductor behaviour with a dominant crystalline componen

Correlation between hysteresis phenomena and hole-like trap in capacitance-voltage characteristics of AlGaN/GaN of Schottky barrier diode

In this work we report on the characteristics of (Ni/Au)/AlGaN/GaN/SiC Schottky barrier diode (SBD). A variety of electrical techniques such as capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS) measurements were used to characterize the diodes. We observed an hysteresis phenomenon on the C-V characteristics in the Schottky diode. The parasitic effect can be attributed to the presence of traps in the heterostructure. Deep defects analysis was performed by deep-level transient spectroscopy (DLTS). One hole trap have been detected with an activation energy and a capture cross-section of 0.75 eV and 1.093 × 10−11 cm2. The localization and the identification of this trap have occurred and a correlation between the defect and the hysteresis phenomenon has been discussed. At high temperatures, the DLTS signal sometimes becomes negative, likely due to an artificial surface-state effect

Parasitic effects and traps in AlGaN/GaN HEMT on sapphire substrate

AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O3) substrates reveal anomalies like kink effect, current collapse, hysteresis phenomena on Ids-Vds and Ids-Vgs. These parasitic effects can be attributed to the presence of traps in the hetero-structure. Deep defects analysis was performed by conductance deep level transient spectroscopy (CDLTS) under drain pulse. Four electron traps have been detected with activation energy and capture cross-section of 2.62 eV, 1.18 eV, 0.97 eV, 0.48 eV, σn = 2.4 × 10-17 cm2 and σn = 2.37 × 10-14 cm2, σn = 2 × 10-12 cm2 and σn = 4.67 × 10-14 cm2 respectively. The localisation and the identification of these traps have occurred and a correlation between defects and parasitic effects has been discussed

Hole emission processes from InAs quantum dots grown on p-type InAlAs/InP(0 0 1)

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Engineering of electronic and optical properties of PbS thin films via Cu doping

Copper-doped PbS polycrystalline thin films were deposited by chemical bath deposition by adding small amount of Cu (y(solution) = [Cu2+]/[Pb2+]) between 0.5 and 2 at%. The composition, structure, morphology, optical and electrical properties of the films were investigated by means of X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), UV-visible near infrared (UV-Vis-NIR) spectrophotometry and Hall effect measurements. The XRD studies showed that the undoped films have PbS face centered cubic structure with (111) preferential orientation, while preferential orientation changes to (200) plane with increasing Cu doping concentration. The AFM and SEM measurements indicated that the film surfaces consisted of nanosized grains with pyramidal shape. Optical band gap was blue shifted from 0.72 eV to 1.69 eV with the increase in Cu doping concentration. The film obtained with the [Cu2+]/[Pb2+] ratio equal to 1.5 at% Cu showed the minimum resistivity of 0.16 Omega cm at room temperature and optimum value of optical band gap close to 1.5 eV. 1.5 at% Cu-doped PbS thin films exhibit the best optical and electrical properties, suitable for solar cells applications. (C) 2016 Elsevier Ltd. All rights reserved

An Eco-Friendly Synthetic Approach for Copper Nanoclusters and Their Potential in Lead Ions Sensing and Biological Applications

A new preparation route for high-luminescent blue-emission pepsin copper nanoclusters (Pep-CuNCs) is introduced in this work. The synthesized nanoclusters are based on a pepsin molecule, which is a stomach enzyme that works to digest proteins that exist in undigested food. Here, we have developed an eco-friendly technique through microwave-assisted fast synthesis. The resulting copper nanoclusters (CuNCs) exhibit significant selectivity towards Pb(II) ions. The pepsin molecule was utilized as a stabilizer and reducing agent in the production procedure of Pep-CuNCs. The characteristics of the resulting Pep-CuNCs were studied in terms of size, surface modification, and composition using various sophisticated techniques. The CuNCs responded to Pb(II) ions through the fluorescence quenching mechanism of the CuNCs’ fluorescence. Thus, great selectivity of Pep-CuNCs towards Pb(II) ions was observed, allowing sensitive determination of this metal ion at lab-scale and in the environment. The CuNCs have detection limits for Pb(II) in very tenuous concentration at a nanomalar scale (11.54 nM). The resulting Pep-CuNCs were utilized significantly to detect Pb(II) ions in environmental samples. Additionally, the activity of Pep-CuNCs on different human tumor cell lines was investigated. The data for the observed behavior indicate that the Pep-CuNCs displayed their activity against cancer cells in a dose dependent manner against most utilized cancer cell lines