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S.H. Jabarov, V.B. Aliyeva, T.G. Mammadov, A.I. Mammadov, S.E. Kichanov, L.S. Dubrovinsky, S.S. Babayev, E.G. Pashayeva and N.T. Dang

Abstract

Raman spectroscopy measurements of a monoclinic layered semiconductor TlGaSe2were performed in a pressure range up to 10.24 GPa. The pressure-induced first-order phase transition accompanied by reconstruction of the layer structure was observed at the pressure P ~ 0.9 GPa. The mode-Grüneisen parameters of intralayer bonds were calculated for TlGaSe2. The contribution of thermal expansion to temperature changes of phonon frequencies was defined. The type of intralayer bonds and their pressure transformation were analyzed in layered TlGaSe2. It was shown that the nature of intramolecular forces in molecular crystals and intralayer forces in layered GaS, GaSe and TlGaSe2is similar

Open access

R. Vasanthakumar, W. Nirmala, R. Santhakumari, R. Meenakshi and A. Sinthiya

Abstract

4-aminopyridinium adipate monohydrate (4APA) was grown by slow evaporation solution growth technique. The functional groups in the grown crystal were identified from FT-IR spectral evaluation. The optical properties together with transmittance of the grown crystal were obtained from UV-Vis spectroscopic study. The mechanical and thermal properties of the grown crystal were studied using Vickers microhardness and TGA/DTA analyses, respectively. Microhardness test revealed that 4-aminopyridinium adipate monohydrate crystal is a soft category material. The density functional method (DFT) was performed using B3LYP with the 6-311G (d,p) basis set. The electronic charge distribution, reactivity of the molecules and the molecular electrostatic potential (MEP) of the grown crystal were analyzed using the B3LYP method. The intermolecular interactions that exist in the crystal structure of the 4APA have also been investigated by Hirshfeld surface analysis. The nonlinear optical properties of the 4APA crystal were confirmed by Kurtz-Perry technique.

Open access

Bartłomiej Dec, Mateusz Ficek, Michał Rycewicz, Łukasz Macewicz, Marcin Gnyba, Mirosław Sawczak, Michał Sobaszek and Robert Bogdanowicz

Abstract

The main subject of this study are molecular structures and optical properties of boron-doped diamond films with [B]/[C]ppm ratio between 1000 and 10 000, fabricated in two molar ratios of CH4-H2mixture (1 % and 4 %). Boron-doped diamond (BDD) film on the fused silica was presented as a conductive coating for optical and electronic purposes. The scanning electron microscopy images showed homogenous and polycrystalline surface morphology. The Raman spectroscopy confirmed the growth of sp3 diamond phase and sp2carbon phase, both regular and amorphous, on the grain boundaries, as well as the efficiency of boron doping. The sp3/sp2ratio was calculated using the Raman spectra deconvolution method. A high refractive index (in a range of 2.0 to 2.4 at λ= 550 nm) was achieved for BDD films deposited at 700 °C. The values of extinction coefficient were below 1.4 at λ= 550 nm, indicating low absorption of the film

Open access

I.S. Yahia, Mohd. Shkir, V. Ganesh, M.M. Abutalib, H.Y. Zahran and S. Alfaify

Abstract

Herein, we report a successful development of nano-scale pure and Al and Mn co-doped PbI2 using facile microwaveassisted route. Structural study was done through X-ray diffraction analysis of grain size, dislocation density and lattice strain. The crystallite size was found to vary from 28 nm to 40 nm due to Al:Mn co-doping in PbI2. The presence of various vibrational modes was confirmed by FT-IR spectroscopy and red shifting was observed in peak positions compared to the bulk. Surface morphology, examined using a scanning electron microscope, confirmed the formation of single crystal nanosheets of a thickness in the range of 10 nm to 30 nm. The single crystal nanosheets were found to be transformed to large area nanosheets due to the doping. Enhancement in dielectric constant from ~7.5 to 11 was observed with increasing Al doping concentration. Linear attenuation coefficient was calculated and showed the enhancement of blocking gamma rays with increasing doping concentration. Its value was found to increase from 7.5 to 12.8 with the doping. The results suggest that the synthesized nanostructures can be used for detection and absorption of gamma rays emitted by 137Cs and 241Am sources.

Open access

C.H. Voon, B.Y. Lim, S.C.B. Gopinath, Y. Al-Douri, K.L. Foo, M.K. Md Arshad, S.T. Ten, A.R. Ruslinda, U. Hashim and V.C.S. Tony

Abstract

Cuprous oxide, a narrow bandgap p-type semiconductor, has been known as a potential material for applications in supercapacitors, hydrogen production, sensors, and energy conversion due to its properties such as non-toxicity, easy availability, cost effectiveness, high absorption coefficient in the visible region and large minority carriers diffusion length. In this study, Cu2O nanostructured thin film was fabricated by anodizing of Cu plates in ethylene glycol containing 0.15 M KOH, 0.1 M NH4F and 3 wt.% deionized water. The effects of anodizing voltage and temperature of electrolyte were investigated and reported. It was found that nanoporous Cu2O thin film was formed when anodizing voltages of 50 V and 70 V were used while a dense Cu2O thin film was formed due to the aggregation of smaller nanoparticles when 30 V anodizing voltage was used. Nanoplatelets thin film was formed when the temperature of electrolyte was reduced to 15 °C and 5 °C. X-ray diffraction confirmed the presence of Cu2O phase in thin film formed during anodizing of Cu plates, regardless of the anodizing voltage and temperature of electrolyte. Photoluminescence spectroscopy showed the presence of Cu2O peak at 630 nm corresponding to band gap of 1.97 eV. A mechanism of the formation of Cu2O thin film was proposed. This study reported the ease of tailoring Cu2O nanostructures of different morphologies using anodizing that may help widen the applications of this material

Open access

Ahmad Irfan

Abstract

Various photovoltaic parameters, i.e., electron injection (ΔGinject.), electronic coupling constants (|VRP|), light harvesting efficiencies (LHE), band alignment and electronic properties of five chalcone derivatives were studied by density functional theory (DFT) and time domain. The light was also shed on the effect of different electron donating groups and their strength intensity on the electronic and charge transfer properties. The balanced hole and electron reorganization energies for Comp 4 showed that it might have better ambipolar charge transfer in nature. The strong electron donating group(s) usually enhance(s) the ΔGinject. and |VRP| of chalcones as -N(CH3)2 > OCH3 > OH. Additionally, ΔGinject. and |VRP| of various substituted chalcone derivatives have been observed as trimethoxy > dimethoxy > monomethoxy. The greater electron donating ability of substituents is also favorable for the staggered band alignment. The superior ΔGinject. of all the studied chalcones than of the referenced compounds disclosed that the prior compounds would be proficient photovoltaic materials.

Open access

S.A. Surma, J. Brona and A. Ciszewski

Abstract

Work function (WF) and some physicochemical data for several most prominent crystal planes of three metals of typical structures are calculated within the linear approximation employing the surface dipole and 2D gas models. “Composite” crystal of a homogeneous bulk phase and a thick surface composed of eight (h k l)-oriented facets with different unsaturated bonds is treated as a nine-phase nine-component system with two degrees of freedom. It contains the two-dimensional metal-lattice plasma of free electrons and the immobile atom-core network. For twenty four (h k l) surfaces, the WF and dipole barrier term, chemical and electrostatic potential levels, electron charge densities, surface dipole fields, and other parameters are calculated and tabularized. WF values obtained from the thermodynamics based formula are compared to the ones obtained from the quantum mechanics based formula, which shows good agreement with experiment and also reveals a specific deviation in the case of field emission method for the most packed plane. A set of accurate face dependent data can be of interest to electronics and materials science workers

Open access

Jia Zhu, Lei Xiang, Yazhou Zhou and Juan Yang

Abstract

Cotton-like CoS cluster has been successfully synthesized via a simple one-step hydrothermal route assisted by diethylenetriamine (DETA) as a ligand and structure-directing agent. The structure and morphology of the product were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) and N2 adsorption-desorption isotherm. The CoS sample which has a hexagonal phase without any impurities possesses a microscopic morphology made by cotton-like clusters. The as-fabricated CoS as a supercapacitor electrode presents desirable supercapacitive performance with a high specific capacitance (664 F∙g-1 at 0.5 A∙g-1), remarkable rate capability and excellent cycling stability (85.7 % specific capacitance retention after 1000 cycles), making it applicable as an electrode for high-performance supercapacitors.

Open access

Gnana Praveena Nethala, Ravindar Tadi, Aroli Venkateswara Anupama, Satish Laxman Shinde and V. Veeraiah

Abstract

Mg substituted cobalt ferrite spinel powder samples with the general formula MgxCO1-xFe2O4(x = 0 to 0.25) were synthesized chemically through sol-gel method and annealed at 1100 °C for 2 h. They were initially screened for the structural and morphological properties by X-ray diffraction and field emission scanning electron microscopy, respectively. Vibrational properties of the samples were studied by Raman and infrared spectroscopies. X-ray diffraction confirmed the formation of single pure or near-pure phase with cubic spinel structure for all the samples with expected occupancy values. The field emission scanning electron microscopy revealed a decrease in the particle size with an increase in Mg concentration. Both structural and magnetic properties of the samples were characterized using Mössbauer spectroscopy while the magnetic properties were studied using vibrating sample magnetometry. The changes in magnetic moment of ions, their coupling with neighboring ions and cation exchange interactions were confirmed from the Mössbauer spectroscopy analysis. Saturation magnetization and coercivity values can be explained based on the Slater-Pauling curve. The magnetometry results showed a decrease in saturation magnetization of the samples with increase in Mg concentration

Open access

Ishu Sharma and Sruthi Sunder

Abstract

Glass forming ability of lone-pair semiconductors was analyzed for (x = 0, 2, 4, 6, 8, 10) system. Values of lone pair electrons L were calculated using average coordination number of valence electrons. These values were found to decrease, as the system was moving towards the rigid region. L > 3 values showed vitreous state. Deviation of the stoichiometry confirmed the chalcogen-rich region. A linear correlation was found between the mean bond energy and glass transition temperature. Chemical Bond Approach model was applied to calculate the cohesive energy of the system. A linear relationship was found to exist between the cohesive energy and the theoretical band gap, calculated using Shimakawa relation. A decrease in both parameters was explained on the basis of average stabilization energy and electronegativity of the system. The density values were found to increase and may account for higher refractive index of the system. Large Bohr radius of the Bi atom accounted for an increase in the polarizability. Other parameters viz. degree of covalency, packing density, compactness, molar volume, free volume percentage, excess volume and polaron radius were also calculated. An effort was made to correlate the effect of Bi addition to Ge12Se76 - xAs12Bixlone-pair semiconductor on the basis of the structure of the glassy matrix or the connectedness of the material.