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In power electronics, compound semiconductors with large bandgaps, like silicon carbide (SiC), are increasingly being used as material instead of silicon. They have a lot of advantages over silicon but are also intolerant of nanoscale material defects, so that a defect inspection with high accuracy is needed. The different defect types on SiC samples are measured with various measurement methods, including optical and tactile methods. The defect types investigated include carrots, particles, polytype inclusions and threading dislocations, and they are analysed with imaging ellipsometry, coherent Fourier scatterometry (CFS), white light interference microscopy (WLIM) and atomic force microscopy (AFM). These different measurement methods are used to investigate which method is most sensitive for which type of defect to be able to use the measurement methods more effectively. It is important to be able to identify the defects to classify them as critical or non-critical for the functionality of the end product. Once these investigations have been completed, the measurement systems can be optimally distributed to the relevant defects in further work to realize a hybrid analysis of the defects. In addition to the identification and classification of defects, such a future hybrid analysis could also include characterizations, e.g. further evaluation of ellipsometric data by using numerical simulations. [ABSTRACT FROM AUTHOR]

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Dicarboxylic acids are ubiquitous in atmospheric aerosol particles, but their roles as surfactants in cloud condensation nuclei (CCN) activity remain unclear. In this study, we investigated CCN activity of inorganic salt (sodium chloride and ammonium sulfate) and dicarboxylic acid (including malonic acid (MA), phenylmalonic acid (PhMA), succinic acid (SA), phenylsuccinic acid (PhSA), adipic acid (AA), pimelic acid (PA), and octanedioic acid (OA)), mixed particles with varied organic volume fractions (OVFs), and then directly determined their surface tension and phase state at high relative humidity (over 99.5 %) via atomic force microscopy (AFM). Our results show that CCN-derived κCCN of studied dicarboxylic acids ranged from 0.003 to 0.240. A linearly positive correlation between κCCN and solubility was obtained for slightly dissolved species, while negative correlation was found between κCCN and molecular volume for highly soluble species. For most inorganic salts and dicarboxylic acids (MA, PhMA, SA, PhSA and PA), a good closure within 30 % relative bias between κCCN and chemistry-derived κChem was obtained. However, κCCN values of inorganic salt–AA and inorganic salt–OA systems were surprisingly 0.3–3.0 times higher than κChem , which was attributed to surface tension reduction, as AFM results showed that their surface tensions were 20 %–42 % lower than that of water (72 mN m -1). Meanwhile, semisolid phase states were obtained for inorganic salt–AA and inorganic salt–OA and also affected hygroscopicity closure results. Our study highlights that surface tension reduction should be considered when investigating aerosol–cloud interactions. [ABSTRACT FROM AUTHOR]

Carbonate biological hard tissues are valuable archives of environmental information. However, this information can be blurred or even completely lost as hard tissues undergo diagenetic alteration. This is more likely to occur in aragonitic skeletons because bioaragonite often transforms into calcite during diagenesis. For reliably using aragonitic skeletons as geochemical proxies, it is necessary to understand in depth the diagenetic alteration processes that they undergo. Several works have recently investigated the hydrothermal alteration of aragonitic hard tissues during short-term experiments at high temperatures (T > 160 ∘C). In this study, we conduct long-term (4 and 6 months) hydrothermal alteration experiments at 80 ∘C using burial-like fluids. We document and evaluate the changes undergone by the outer and inner layers of the shell of the bivalve Arctica islandica, the prismatic and nacreous layers of the hard tissue of the gastropod Haliotis ovina, and the skeleton of the coral Porites sp. combining a variety of analytical tools (X-ray diffraction, thermogravimetry analysis, laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction and atomic force microscopy). We demonstrate that this approach is the most adequate to trace subtle, diagenetic-alteration-related changes in aragonitic biocarbonate structural hard materials. Furthermore, we unveil that the diagenetic alteration of aragonitic biological hard tissues is a complex multi-step process where major changes occur even at the low temperature used in this study, well before any aragonite into calcite transformation takes place. Alteration starts with biopolymer decomposition and concomitant generation of secondary porosity. These processes are followed by abiogenic aragonite precipitation that partially or totally obliterates the secondary porosity. Only subsequently does the transformation of the aragonite into calcite occur. The kinetics of the alteration process is highly dependent on primary microstructural features of the aragonitic biomineral. While the skeleton of Porites sp. remains virtually unaltered for the entire duration of the conducted experiments, Haliotis ovina nacre undergoes extensive abiogenic aragonite precipitation. The outer and inner shell layers of Arctica islandica are significantly affected by aragonite transformation into calcite. This transformation is extensive for the prismatic shell layer of Haliotis ovina. Our results suggest that the majority of aragonitic fossil archives are overprinted, even those free of clear diagenetic alteration signs. This finding may have major implications for the use of these archives as geochemical proxies. [ABSTRACT FROM AUTHOR]

We developed a method for examining ice formation on solid substrates exposed to cloud-like atmospheres. Our experimental approach couples video-rate optical microscopy of ice formation with high-resolution atomic-force microscopy (AFM) of the initial mineral surface. We demonstrate how colocating stitched AFM images with video microscopy can be used to relate the likelihood of ice formation to nanoscale properties of a mineral substrate, e.g., the abundance of surface steps of a certain height. We also discuss the potential of this setup for future iterative investigations of the properties of ice nucleation sites on materials. [ABSTRACT FROM AUTHOR]

As one of the intense anthropogenic emission regions across the relatively high-latitude (>40 ∘ N) areas on Earth, northeast China faces the serious problem of regional haze during the heating period of the year. Aerosols in polluted haze in northeast China are poorly understood compared with the haze in other regions of China such as the North China Plain. Here, we integrated bulk chemical measurements with single-particle analysis from transmission electron microscopy (TEM), nanoscale secondary ion mass spectrometry (NanoSIMS), and atomic force microscopy (AFM) to obtain morphology, size, composition, aging process, and sources of aerosol particles collected during two contrasting regional haze events (Haze-I and Haze-II) at an urban site and a mountain site in northeast China and further investigated the causes of regional haze formation. Haze-I evolved from moderate (average PM2.5 : 76–108 µ g m -3) to heavy pollution (151–154 µ g m -3), with the dominant PM2.5 component changing from organic matter (OM) (39–45 µ g m -3) to secondary inorganic ions (94–101 µ g m -3). Similarly, TEM observations showed that S-rich particles internally mixed with OM (named S-OM) increased from 29 % to 60 % by number at an urban site and 64 % to 74 % at a mountain site from the moderate Haze-I to heavy Haze-I events, and 75 %–96 % of Haze-I particles included primary OM. We found that change of wind direction caused Haze-I to rapidly turn into Haze-II (185–223 µ g m -3) with predominantly OM (98–133 µ g m -3) and unexpectedly high K+ (3.8 µ g m -3). TEM also showed that K-rich particles internally mixed with OM (named K-OM) increased from 4 %–5 % by number to 50 %–52 %. The results indicate that there were different sources of aerosol particles causing the Haze-I and Haze-II formation: Haze-I was mainly induced by accumulation of primary OM emitted from residential coal burning and further deteriorated by secondary aerosol formation via heterogeneous reactions; Haze-II was caused by long-range transport of agricultural biomass burning emissions. Moreover, abundant primary OM particles emitted from coal and biomass burning were considered to be one typical brown carbon, i.e., tar balls. Our study highlights that large numbers of light-absorbing tar balls significantly contribute to winter haze formation in northeast China and they should be further considered in climate models. [ABSTRACT FROM AUTHOR]

Understanding the impact of sea spray aerosol (SSA) on the climate and atmosphere requires quantitative knowledge of their chemical composition and mixing states. Furthermore, single-particle measurements are needed to accurately represent large particle-to-particle variability. To quantify the mixing state, the organic volume fraction (OVF), defined as the relative organic volume with respect to the total particle volume, is measured after generating and collecting aerosol particles, often using deposition impactors. In this process, the aerosol streams are either dried or kept wet prior to impacting on solid substrates. However, the atmospheric community has yet to establish how dry versus wet aerosol deposition influences the impacted particle morphologies and mixing states. Here, we apply complementary offline single-particle atomic force microscopy (AFM) and bulk ensemble high-performance liquid chromatography (HPLC) techniques to assess the effects of dry and wet deposition modes on the substrate-deposited aerosol particles' mixing states. Glucose and NaCl binary mixtures that form core–shell particle morphologies were studied as model systems, and the mixing states were quantified by measuring the OVF of individual particles using AFM and compared to the ensemble measured by HPLC. Dry-deposited single-particle OVF data positively deviated from the bulk HPLC data by up to 60 %, which was attributed to significant spreading of the NaCl core upon impaction with the solid substrate. This led to underestimation of the core volume. This problem was circumvented by (a) performing wet deposition and thus bypassing the effects of the solid core spreading upon impaction and (b) performing a hydration–dehydration cycle on dry-deposited particles to restructure the deformed NaCl core. Both approaches produced single-particle OVF values that converge well with the bulk and expected OVF values, validating the methodology. These findings illustrate the importance of awareness in how conventional particle deposition methods may significantly alter the impacted particle morphologies and their mixing states. [ABSTRACT FROM AUTHOR]