The purpose of this paper was to describe the 3D nano-scaled surface topography of the aluminum nitride on sapphire. The structures were prepared by magnetron sputtering with heating of the sapphire substrate. The dependence of the layers topography on the substrate temperature was presented. Surface appearance was studied by atomic force microscopy (AFM). The quantitative topography data from AFM were used for surface characterization by fractal analysis and statistical parameters. The results of fractal analysis show the correlation of fractal dimension and statistical characteristics of surface topography. The data may contribute to manufacture of AlN thin films with desired surface characteristics.

Abstract The aim of this study is to characterize the surface topography of aluminum nitride (AlN) epilayers prepared by magnetron sputtering using the surface statistical parameters, according to ISO 25178-2:2012. To understand the effect of temperature on the epilayer structure, the surface topography was investigated through atomic force microscopy (AFM). AFM data and analysis of surface statistical parameters indicated the dependence of morphology of the epilayers on their growth conditions. The surface statistical parameters provide important information about surface texture and are useful for manufacturers in developing AlN thin films with improved surface characteristics. These results are also important for understanding the nanoscale phenomena at the contacts between rough surfaces, such as the area of contact, the interfacial separation, and the adhesive and frictional properties.

The paper deals with the successive localization and imaging of solar cell defects, going from macroscale to microscale. For the purpose of localization, the light emission from reversed bias samples is used. After rough macroscopic localization, microscopic localization by scanning probe microscopy combined with a photomultiplier (shadow mapping) is performed. The type of microscopic defects are discernable from their current-voltage plot or from noise measurements. Two specific defects, both of the avalanche type, with different voltage threshold, are presented in this paper. Current voltage plots and radiant flux versus voltage characteristics for two temperatures, topography, shadow map and corresponding SEM micrographs are shown for both samples.

We report on detection and localization of imperfections in silicon solar cell bulk and surface with sub-micrometer resolution. To obtain this resolution, a family of imaging techniques including SNOM, SEM and AFM is often separately used for this purpose. In this paper we combine several of these proximal methods together, because each of them brings complimentary information about the imperfection. First, we note that SNOM images often contain distortions due to the interaction of the probe tip and sample. Therefore, we look for the possibility to circumvent this weakness and obtain more realistic images. In our experiments, we take advantage of the fact that defects or imperfections in silicon solar cell structures under reverse-bias voltage exhibit microscale low light emitting spots, and we apply an improved SNOM measurement to localize these spots. As a result, this system allows a localization and measurement of low light emission on microscale. Consequently, the size and shape of imperfections can also be determined.

In this work, the etch rate of silicon carbide and aluminum oxide were studied as a function of the angle etching material and flow of plasma. Al2O3 and SiC are important materials in the design of optical and electronic devices and the topography of the wafers has a large influence on the device quality. Argon was applied for the dry etching of Al2O3 and SiC wafers. The wafer slope for highest obtained etch is defined. Atomic force microscopy was used to good morphology control of etched wafers. Statistical and correlation analysis was applied to estimate the surface perfection. Interferometry allowed to control etching rate.

The objective of the study is to characterize the dependence of the optical properties of solid solutions of silicon carbide and aluminum nitride on composition. Even small differences in composition provide manipulation of band gap features over a wide range. Data for this paper were collected by X-ray diffraction, photoluminescence and absorption spectroscopy. The evolution of the observed optical properties as a result of compositional changes were studied. X-ray studies confirm the presence of a(SiC)1-x(AlN)x solid solution. Investigation of absorption spectra shows the optical band gap of the sample with composition (SiC)0,88(AlN)0,12 is 3.5eV, and 4.24 eV for the (SiC)0,36(AlN)0,64 solid solution. The photoluminescence spectra demonstrate the strong dependence of the spectra on composition x. The experimental results are in agreement with theory. These data demonstrate the optimization of optical properties for particular optoelectronic applications by varying the (SiC)1-х(AlN)х composition.

This study describes the principles of synthesis and technological features of composition ceramics formation on the basis of silicon carbide and aluminum nitride by hot-pressing. The structural properties and composition of the ceramics were investigated by scanning electron microscope and the formation of the solid solution is confirmed. The elements distribution on the surface of failure pattern is shown. The results of the study are useful for optimization of manufacturing process of structural and functional high-density ceramics.

The paper describes the process of sapphire and silicon carbide substrates preparation by dry plasma etching and its characterization. The study confirms the possibility of using dry plasma etching processes for wide band gap materials treatment, since the condition of the substrate surface is an important parameter for electronic and optoelectronic devices manufacturing. Processed substrates were studied by interferometry to define the etch depth, and by atomic force microscopy to study the topography and statistical analysis of surface roughness before and after etching. The interferometry reveals the dependence of etch rate on the angle between the substrates and defocused beam of argon ions. It is also shown in low scale image that the surface damage occurs after the substrate treatment. But the common large area surface topography indicates the decreasing of roughness. In order to have purely physical etching the argon plasma was used. Thus this combination of methods allows determine optimal conditions of the substrate preparation.

The performance and lifetime of solar cells critically depends on bulk and surface defects. To improve performance of solar cells, localization and characterization of defects on the microscale is an important issue. This paper describes a variety of microstructural defects in crystalline silicon solar cells which appear during the cell processing steps. The set of defects have been investigated and localized using visible light emission under reversed bias voltage. A light beam induced photocurrent method allows localization of defects having impact on the sample current-voltage plot and reversed bias light emission characteristics. These are shown together with the micrographs of defective surface areas. As a result, particular defects which induce nonlinearity and local breakdown in the current-voltage plot were identified in tested solar cell structures. Furthermore, measurements at various temperatures allows to identify the breakdown mechanism of the investigated defects. An interesting result of the investigation is that the majority of defects are associated with surface inhomogeneities, but not all surface inhomogeneities act as defects. (C) 2014 Elsevier B.V. All rights reserved.

The research in this field is focused to the investigation of biological structures with superior optical features. The study presents atomic force microscopy of biological optical structures on butterfly wings. The bright blue and dark black color scales exhibit the different topography. These scales were compared to the visually the same color scales of other two species of butterflies. The histograms of heights distribution are presented and show similar results for the scales of one color for different species.

The objective of the study is a growth of SiC/(SiC)1−x(AlN)x structures by fast sublimation epitaxy of the polycrystalline source of (SiC)1−x(AlN)x and their characterisation by proximal scanning electron microscopy and atomic force microscopy. For that purpose optimal conditions of sublimation process have been defined. Manufactured structures could be used as substrates for wide-band-gap semiconductor devices on the basis of nitrides, including gallium nitride, aluminum nitride and their alloys, as well as for the production of transistors with high mobility of electrons and also for creation of blue and ultraviolet light emitters (light-emitted diodes and laser diodes). The result of analysis shows that increasing of the growth temperature up to 2300 K allows carry out sublimation epitaxy of thin layers of aluminum nitride and its solid solution.

Monocrystalline silicon is still very interesting material for solar cells fabrication due to its quality and external efficiency. Nevertheless during a tailoring of eligible silicon wafers, some inhomogeneities or irregularities emerge and provide defects which give trouble to good operation of solar panels. Generally, there are two classes of defects in silicon wafer: material defects due to imperfections or irregularity in crystal structure (point, line, square or volume defects), and defects induced by wafer processing. To avoid a use of damaged cells, macroscopic and microscopic measurement techniques must be applied. In this paper we present a microscopic method combining electrical noise measurements with scanning probe localization of luminous micro-spots defects. The paper brings experimental results showing local electric and optical investigations of defects in etched monocrystalline silicon solar cells and a use of cold field emission tungsten electrode as a local probe for apertureless scanning near-field optical microscope.

The aim of this paper is to discuss the impact of nanoparticles in epoxy matrix on dielectric parameters in the course of ageing. One of the directions pursued in the development of epoxy resins is the addition of nanofillers which act as efficient barriers for the propagation of electrical trees. In view of the prospects for the potential replacement of currently-used epoxy-based electric insulations with epoxy nanocomposites, it is necessary to know the behavior of such epoxy resins with nanofillers during aging. For this purpose, epoxy nanocomposites were exposed to accelerated aging and changes in dielectric properties were observed. Experimental samples were manufactured from bisphenol-A based epoxy resin for high voltage applications and oxide nanofillers. The volume of nanofiller added into epoxy resin was 1.5 wt %. Sample thickness was of the order of a few hundreds of μm. Complex permittivity (ε), inner resistivity (ρi) and loss factor (tan δ) were measured at temperatures from -153 °C to +167 °C and in the frequency range 10-2 to 106 Hz.

Monocrystalline silicon wafer is up-to-date most used material for the fabrication of solar cells. The recent investigation shows that the quality of cells is often degraded by structural defects emerging during processing steps. Hence the paper gives first an overview of solar cell efficiency investigation on macroscale. Then a detection and microscale localization of tiny local defects in solar cell structures which evidently affect electrical and photoelectrical properties of the cells is targeted. The local defects can be classified as microfractures, precipitates and other material structure inhomogeneities. Detection and localization of the defects in the structure and the assigning of particular defects to corresponding degradation of photoelectrical parameters are key points for solar cell lifetime and efficiency improvement. Although the breakdown can be evident in current-voltage plot, the localization of defects on the sample has to be provided by microscopic investigations as well as by defects light emission measurement under electrical bias conditions.The experimental results obtained from samples where the defects were microscopically repaired by focused ion beam are presented. Electrical and photoelectrical properties of sample before and after milling processing are also discussed.

Scanning probe microscopes are powerful tool for micro-or nanoscale diagnostics of defects in crystalline silicon solar cells. Solar cell is a large p-n junction semiconductor device. Its quality is strongly damaged by the presence of defects. If the cell works under low reverse-biased voltage, defects emit a light in visible range. The suggested method combines three different measurements: electric noise measurement, local topography and near-field optical beam induced current and thus provides more complex information. To prove its feasibility, we have selected one defect (truncated pyramid) in the sample, which emitted light under low reverse-biased voltage.

A process for ion-plasma formation of aluminum nitride (AlN) nanolayers on nitrided sapphire (Al2O3) substrates is presented. The method is based on the direct current magnetron sputtering of a high-purity aluminum target in the presence of an argon–nitrogen gas mix and high frequency-activated nitrogen plasma. The method, combined with ion etching, produced matched layers by nitration of Al2O3 in the (0001) plane, and formation of high quality AlN epilayers on this surface was observed. The processing characteristics and morphology dependence on synthesis parameters were studied using atomic force microscopy.

This study describes the structural coloration of the butterfly Vanessa Atalanta wings and shows how the atomic force microscopy (AFM) can be applied to the study of wings morphology and wings surface behavior under the temperature. The role of the wings morphology in colors was investigated. Different colors of wings have different topology and can be identified by them. AFM in semi-contact mode was used to study the wings surface. The wing surface area, which is close to the butterfly body, has shiny brown color and the peak of surface roughness is about 600 nm. The changing of morphology at different temperatures is shown.

In this study the optical properties of SiC/(SiC)(1-x)(AlN)(x) heterostructures were investigated. The photoluminescence spectrum of (SiC)(1-x)(AlN)(x) samples at different temperatures and also the dependence of photoluminescence on wavelength of exciting light were studied. Absorption factor is defined using measured values of transmitting efficiency. The results of study of morphology and composition of obtained samples confirm growth regularity in single-crystal phase. It was observed that n-SiC/p-(SiC)(1-x)(AlN)(x) begins to shine at reverse voltage that a little exceed the voltage of irreversible breakdown.