General synthesis of manganese-doped II-VI and III-V semiconductor nanowires

A general approach for the synthesis of manganese-doped II-VI and III-V nanowires based on metal nanocluster-catalyzed chemical vapor deposition has been developed. High-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy studies of Mn-doped CdS, ZnS, and GaN nanowires demonstrate that the nanowires are single-crystal structures and homogeneously doped with controllable concentrations of manganese ions. Photoluminescence measurements of individual Mn-doped CdS and ZnS nanowires show characteristic pseudo-tetrahedral Mn2+ ((4)T1-->(6)A1) transitions that match the corresponding transitions in bulk single-crystal materials well. Photoluminescence studies of Mn-doped GaN nanowires suggest that manganese is incorporated as a neutral (Mn3+) dopant that partially quenches the GaN band-edge emission. The general and controlled synthesis of nanowires doped with magnetic metal ions opens up opportunities for fundamental physical studies and could lead to the development of nanoscale spintronic devices.     

The sol-gel technology application of cotton textile processing

In this research, pure cotton textile was modified by the sol-gel technology with low thermal post-treatment temperatures: drying at 90 °C for 10 min after curing at 120, 140 and 160 °C for 2 min. The impact of the cotton textile coating by sol-gel technology, different curing temperatures and multiple washing cycles to the adhesion of the coating, textile air permeability and abrasion resistance were studied. The morphology changes of the cotton textile surface before and after coating, and after multiple washing cycles were evaluated by scanning electron microscopy. The sol-gel treatment can impart antibacterial properties to the textile against Pseudomonas aeruginosa and Staphylococcus epidermidis, by the reduction of the bacteria adhesion with the cotton textile. All test results evince about a very good coating containing Zn and Si adhesion with cotton textile fibres..     

Controlled synthesis of AlN/GaN multiple quantum well nanowire structures and their optical properties

We report the controlled synthesis of AlN/GaN multi-quantum well (MQW) radial nanowire heterostructures by metal-organic chemical vapor deposition. The structure consists of a single-crystal GaN nanowire core and an epitaxially grown (AlN/GaN)(m) (m = 3, 13) MQW shell. Optical excitation of individual MQW nanowires yielded strong, blue-shifted photoluminescence in the range 340-360 nm, with respect to the GaN near band-edge emission at 368.8 nm. Cathodoluminescence analysis on the cross-sectional MQW nanowire samples showed that the blue-shifted ultraviolet luminescence originated from the GaN quantum wells, while the defect-associated yellow luminescence was emitted from the GaN core. Computational simulation provided a quantitative analysis of the mini-band energies in the AlN/GaN superlattices and suggested the observed blue-shifted emission corresponds to the interband transitions between the second subbands of GaN, as a result of quantum confinement and strain effect in these AlN/GaN MQW nanowire structures.     

Effects of gold diffusion on n-type doping of GaAs nanowires

The deposition of n-GaAs shells is explored as a method of n-type doping in GaAs nanowires grown by the Au-mediated metal-organic chemical vapor deposition. Core-shell GaAs/n-GaAs nanowires exhibit an unintended rectifying behavior that is attributed to the Au diffusion during the shell deposition based on studies using energy dispersive X-ray spectroscopy, current-voltage, capacitance-voltage, and Kelvin probe force measurements. Removing the gold prior to n-type shell deposition results in the realization of n-type GaAs nanowires without rectification. We directly correlate the presence of gold impurities to nanowire electrical properties and provide an insight into the role of seed particles on the properties of nanowires and nanowire heterostructures.     

Renewable Energy Sources and Pricing of Electrical Power

This report deals with some characteristics of the electric power system of Bulgaria. Emphasis is put on the benefits of joining the small photovoltaic plants in the tourist areas of the country. As an example of that the town of Pomorie is examined. Data on the quality of the consumed electric energy and the price per a four-member family are presented. The amount of the solar radiation for the town of Pomorie is audited through the PVGIS （Photovoltaic Geographical Information System）. Discussed are the types of photovoltaic panels offered on the market by manufacturers in terms of the received power efficiency. Developed is a model of creating a photovoltaic system on the roof of a house, inhabited by several families. Calculations are made on the cost of the electricity generated by the proposed system. Compared is the cost of the electricity supplied by the electricity provider EVN （Energie Verntinftig Nutzen） in the town of Pomorie to the one that will be obtained using the proposed PV-system.     

The interplay of structural and optical properties in individual ZnO nanostructures

Semiconductor nanostructures exhibit unique properties distinct from their bulk counterparts by virtue of nanoscale dimensions; in particular, exceptionally large surface area-to-volume ratios relative to that of the bulk produce variations in surface state populations that have numerous consequences on materials properties. Of the low-dimensional semiconductor nanostructures, nanowires offer a unique prospect in nanoscale optoelectronics due to their one-dimensional architecture. Already, many devices based upon individual nanowires have been demonstrated, but questions about how nano-size and structural variations affect the underlying materials properties still remain unanswered. Here, we focus on understanding the growth mechanism and kinetics of ZnO nanowires and related nanowalls, and their effects on nanoscale structural and optical properties.