Robert Szoszkiewicz1 , Wojciech Spychalski2 , Marcin Pisarek3
1University of Warsaw, Chemistry, Poland
2Warsaw University of Technology, Materials Science and Engineering, Poland
3Institut of Physical Chemistry of the Polish Academy of Sciences, , Poland
Because of profound applications of MoS$_2$ crystals in electronics, their oxidation is the subject of substantial interest. We report on oxidation of the surface of single MoS$_2$ crystals, which were heated within a precision muffle furnace at a series of increasing temperatures up to 500$^°$C. Using electron dispersion X-ray spectroscopy (EDS) at ambient conditions, we observed an increase of oxide content with increasing heating temperature and obtained an apparent activation energy for the oxidation process of the order of 1 kcal/mol. This value is at least 8 times smaller than an activation energy for surface formation of MoO$_3$ and according to the literature points rather to physisorbed oxygen species. Our Auger electron spectroscopy (AES) results also pointed out toward the physisorbed oxygen, similarly as our further heating studies within elevated relative humidity conditions. The Mo oxide leftovers on the sample were investigated using atomic force microscopy (AFM) and showed dendritic structures. Surface appearance of those dendrites, their fractal dimension between 1.61 and 1.66, and their surface distribution were reminiscent of the diffusion-limited aggregation (DLA) growth. On the basis of analysis of AFM topographs, we hypothesized that the DLA process was controlled by a surface diffusion of the initially physisorbed oxygen, which had to diffuse to reaction centers in order to facilitate the subsequent chemical conversion of MoS$_2$ layers to volatile Mo oxides.
Abderrahim Hadj Larbi1 , Said Hiadsi2 , Moufdi Hadjab3 , Fayçal Bouzid4 , Ammar Haboussi5
1Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga 16014, Algiers, Thin Films Development and Applications Unit - (UDCMA) -Setif- Algeria, Algeria
2Laboratoire de Microscope Electronique et Sciences des Matériaux, Université d’Oran des Sciences et de la Technologie Mohamed Boudiaf, Département de Génie Physique, BP 1505 El m’naouar, Oran, Algerie, , Algeria
3Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga 16014, Algiers, , Algeria
4Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga 16014, Algiers, , Algeria
5Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga 16014, Algiers, , Algeria
Inorganic halide perovskites show a great potential utilization in ceramic scintillators. In this study, we predict the electronic, and optical properties of ABCl3 (A=alkali, B=alkali-earth) perovskite compounds using the full potential linearized augmented plane wave (FP-LAPW) method, based on density functional theory (DFT), implemented in Wien2k code. The exchange and correlation potential was applied using GGA-PBE approximation to relax the internal atomic positions and to calculate the structural properties. In addition, the modified Becke-Johnson (TB-mBJ) potential was used for calculating the electronic and optical properties. Our results are in good agreement with the experimental data, and other theoretical calculations. In the case of orthorhombic phase, the compound reveals that Cl-p states dominate the valence band. The present study of the optical properties shows the isotropic nature of the compounds, the dielectric function, refractive index, energy loss spectra, and absorption coefficient are plotted.
1The University of Nottingham Malaysia Campus, Department of Chemical and Environmental Engineering, Malaysia
Much effort is currently being devoted to the study of nanomaterials mainly due to their wide variety of applications. Particularly, nanoparticles have generated a large research effort because of their properties which differ markedly from those of their bulk counterpart. Many different approaches have been applied to the fabrication of nano-entity, such as co-precipitation, microemulsion, supercritical sol-gel processing, hydrothermal synthesis, or high energy ball milling. Directed to the problems of these conventional methods, new synthetic methods have received increased attention in recent years. Cavitation, an approach for synthesizing a variety of compounds at milder conditions is already the rage in materials engineering. The major advantage of this new method is that it affords a reliable and facile route for the control of both the synthetic process and nanostructure in advanced materials. Also, this process provides chemical homogeneity and reactivity through atomic level mixing within the precursor system, and phase pure crystalline materials can be prepared by annealing at reduced temperatures. Various nanomaterials and nanodispersions have been generated using this technique for the development of biosensors. More importantly, novel carbon materials such as Graphene and Fullerene have been exploited for the functionalization and in the development of nanocomposites to be employed in the sensors.
1Universidad del País Vasco UPV/EHU, Departamento de Electricidad y Electrónica, Spain
Soft amorphous ferromagnetic alloys: from basic properties to new applications