Study on Black Phosphorus Characteristics Using a Two-Step Thinning Method

A mild two-step method of black phosphorus (BP) flake thinning was demonstrated in this article. Slight ultraviolet–ozone (UVO) radiation followed by an argon plasma treatment was employed to oxidize mechanically exfoliated BP flakes and remove the surface remains of previous ozone treatment. The annealing process introduced aims to reduce impurities and defects. Low damage and efficient electronic devices were fabricated in terms of controlling the thickness of BP flakes through this method. These results lead to an important step toward the fabrication of high-performance devices based on two-dimensioned materials.

Graphene Transfer: A Physical Perspective

Graphene, synthesized either epitaxially on silicon carbide or via chemical vapor deposition (CVD) on a transition metal, is gathering an increasing amount of interest from industrial and commercial ventures due to its remarkable electronic, mechanical, and thermal properties, as well as the ease with which it can be incorporated into devices. To exploit these superlative properties, it is generally necessary to transfer graphene from its conductive growth substrate to a more appropriate target substrate. In this review, we analyze the literature describing graphene transfer methods developed over the last decade. We present a simple physical model of the adhesion of graphene to its substrate, and we use this model to organize the various graphene transfer techniques by how they tackle the problem of modulating the adhesion energy between graphene and its substrate. We consider the challenges inherent in both delamination of graphene from its original substrate as well as relamination of graphene onto its target substrate, and we show how our simple model can rationalize various transfer strategies to mitigate these challenges and overcome the introduction of impurities and defects into the graphene. Our analysis of graphene transfer strategies concludes with a suggestion of possible future directions for the field.

Temperature Dependence Of Energy States And Band Gap Broadening

Statistical analysis of energy levels is carried out. The density of surface states of MIS structures based on silicon is investigated. A mathematical model is constructed for the temperature dependence of the spectrum of the density of surface states for a wide energy range. A formula is derived for the density of surface states as a function of temperature. The thermal contributions of the expanded bands to the band gap of the semiconductor are taken into account. The resulting formula allows one to determine the density of energy states in the forbidden band in an explicit form, without taking into account the influence of the broadening of the allowed bands. This improves the accuracy of determining the concentration of impurities and defects in silicon.

Observation of Damage of Cotton Fiber in the Processes of Blowing, Cleaning and Carding

The quality of the produced yarn mainly depends on the properties of the raw material, its preparation for spinning, the condition of the equipment, and the preservation of the natural quality of cotton fiber during processing. The question of the number of defects in cotton fiber and their total content is a very important issue for cotton spinning. The non-standardized number of defects in the raw material reduces the quality indicators and yarn yield, which requires additional technological processes; therefore, on the part of production, the requirements for reducing the share of cotton fiber defects are constantly increasing. During processing in blowing and cleaning units and on carding machines, the cotton fiber is mechanically damaged. To observation the damaged fibers, we used the Congo-Roth red paint according to the method of Ch. Dore. Despite the carding is considered the last stage in the process of cleaning the fibers from impurities and defects in the spinning system, 30% of impurities and fiber defects still remain on the card sliver. Besides, it should be noted the carding machine is also considered an additional occurrence of defects, in particular (neps), which reduce the quality indicators of the card sliver and the finished product.

Interactions between carbon impurities and defects produced by proton irradiation in α-iron

Resistivity recovery experiments are performed on α-Fe and an Fe - 220 at. ppm C alloy after 5 MeV proton irradiation at cryogenic temperature of 50 K. By comparing the recovery spectra of pure Fe and the Fe-C alloy we are able to resolve the effect of carbon atoms on the point defect kinetics. It is observed that carbon interacts with both interstitial and vacancy type of defects and delays their annihilation. At temperatures above 500 K the formation of carbides reduces the resistivity of the alloy.

Use of Wyckoff position splittings in the supercell model of crystals with point defects

The atomic sublattices occupying different Wyckoff positions in a host crystal are shown to be subdivided in the supercell model owing to the splitting of the occupied Wyckoff positions. The site symmetries of the split Wyckoff positions are in general different, which significantly increases the number of possible occupation schemes for impurities and defects in the supercell model. It is demonstrated that the use of the programs and retrieval tools of the Bilbao Crystallographic Server considerably simplifies the group-theoretical analysis of Wyckoff position splittings in the supercell model of a crystal with a point defect.Ab initiocalculations of electronic states of single defects in ZnO (Zn and O neutral vacancies) within the supercell model are performed to demonstrate the influence of Wyckoff position splittings on the results.