Photoelectrochemical properties of P and N type tungsten disulfide

Electrochemical and photoelectrochemical properties of single crystals of n or p type WS2 electrodes have been studied using several redox couples in aqueous solution. The current-voltage characteristics without illumination indicated the rectifying nature of the electrolyte-semiconductor interface. The flat-band potential has been determined from capacitance measurements (Mott-Schottky plots) and from photopotentials vs redox potentials. With [math] species present in solution the flat-band potential shifts to more cathodic values, this is discussed in terms of specific adsorption of iodine at the semiconductor surface. The shift of the flat-band potential is related to the smooth or stepped nature of the semiconductor surface

The study of the electronic structure of RuS2

In this study, through theoretical and experimental analyses, we demonstrated that unlike most semiconductors, RuS2 has different indirect bandgaps, which makes it a distinct energy conversion and storage device. In our experimental work, we used the chemical vapor transport and solvent evaporation methods. We obtained RuS2 at a low temperature of 800°C with different stoichiometric shifts of sulfur, such as RuS2.00,RuS1.96, andRuS1.90. Moreover, we studied the correlation between the band structure of RuS2 calculated using the linear muffin-tin orbitals-atomic sphere approximation (LMTO-ASA) method and the growth parameters for each sample. We obtained some noteworthy values of indirect bandgap, such as, 1.84,1.72,1.42,and1.25eV,and direct transition, such as, 2.04,1.93,1.77,and1.49eV. The bandgap values obtained by LMTO-ASA are.1.80727,1.69614,1.46743,and1.23522eV.We obtained indirect bandgaps and a direct transition at the gamma point; their values are 2.04,1.94,1.77, and 1.49eV. We found that RuS2 has valence and conduction bands. The gap energy evaluated by LMTO-ASA was close to the value of that obtained through experimental measurements. We showed that band energy is insensitive to the lattice constant, a. Bandgaps depend on the method of preparation because they change with the temperature and structure (ν). Similar results were obtained for the effective mass. We found two phonons at X and M points, as well as the probability of the existence of two indirect transitions to the bandgap. To the best of our knowledge, this is the first study to confirm that the position of sulfur and S–S distance significantly affect the bandgap

Crystal Growth of RuS2 Using a Chemical Vapor Transport Technique and Its Properties

In this work, we study the effect of increasing temperature on the structure parameters (lattice, sulfur–sulfur distance, and ruthenium–sulfur distance) and the energy gap of RuS2. However, it was very challenging to obtain a sample of RuS2 due to many factors, some of which are discussed in the introduction. To prepare the crystal growth of RuS2, we have used the chemical vapor transport technique. The crystals obtained show a pyrite structure, of which we studied its crystallographic structure, including the structure of crystals in surface (100). The sample was then characterized by X-ray diffraction and by microprobe analysis. We determine the relationship between the energy gap and the sulfur–sulfur distance. We analyzed the S-S bond compared with the S2 molecule