Simulation Study of Silicon-Based Single-Photon Avalanche Diodes with Double Buried Layers and Deep Trench Electrodes

In this paper we present a study of a silicon-based Single-Photon Avalanche Diode (SPAD) in the near-infrared band with double buried layers and deep trench electrodes fabricated by the complimentary metal–oxide semiconductor (CMOS) technology. The deep trench electrodes aim to promote the movement of carriers in the device and reduce the transit time of the photo-generated carrier. The double buried layers are introduced to increase the electric field in the avalanche area and withstand a larger excess bias voltage as its larger depletion region. The semiconductor device simulation software TCAD is used to simulate the performance of this SPAD model, such as the I-V characteristic, the electric field and the Photon Detection Efficiency (PDE). Further optimization of the structure are studied with influence factors such as the doping concentration and depletion region thickness. Based on the results in this study, the designed a structure that can provide a high detecting efficiency in the near-infrared band.

SMALL-AMPLITUDE DISCONTINUOUS DISTURBANCES IN PLEISTOCENE DEPOSITS OF THE VOLYN-PODILSKA UPLAND

The paper presents the results of the study of the small-amplitude discon¬tinuous disturbances of the possibly cryogenic (thermokarst) origin. The dislocations were found in the outcrops of Middle and Upper Pleistocene sediments of the Volyn-Podilska Upland, accumulated in periglacial or sub-periglacial conditions. The distur¬bances are represented mostly by the micro-normal faults and also by sheared fractures and are very similar to tectonic (seismogenic) discontinuities. The tectonotypic fractures in the near-surface deposits of the Pleistocene terraces of Western Bug and Styr (five sections within Volhynian Upland, four of them – in the valley of Bug), as well as in the cover of the Late Pleistocene sediments on the slope of the valley of Dniester (Galician Prydnisterya) are subjected to consideration, analysis and interpretation. In the last location the ruptures are represented mostly by the dis¬turbances identified as sheared fractures. In all others there are small-amplitude normal faults. One reverse fault, timed to an ice-wedge cast, was also revealed. Typical micro-normal faults of all sections are steep and have a number of other common features, which testifies to the same or almost identical mechanism of their formation. These features, in particular, are as follows: 1) insignificant (usually up to 2–2.5 m) length in cross-section and small (several centimeters) amplitude of displacement along the rupture plane; 2) gradual attenuation of the fractures up and down the section. All micro-normal faults are confined to sediments (thicknesses) that are partially or completely composed of sand. The formation of the micro-normal faults and other examined ruptures can be ex¬plained by the uneven compaction and the gravitational subsidence of the rocks, and in the section on the slope of the Dniester valley – also by their displacement down along the slope. It is probable that these processes occurred due to: 1) the degradation of the permafrost; 2) the dehydration of the sand deposits during a significant decrease in the groundwater levels; 3) the melting of the buried layers and lenses of snow, which were accumulated during the winter season in the thickness of sandy the niveo-aeolian deposits. In the outcrops of this terrace, they occur no less frequently than the confidently identified ice wedge pseudomorphs. Key words: small-amplitude disturbances; microfaults; thermokarst; Volyn-Podilska Upland.

Characterizing the Layer Structures of the Lacquerware From the Palace Museum by Terahertz Imaging in Reflection Geometry

Chinese lacquerware is an important invention of arts and crafts in China. In this study, Chinese lacquerware is characterized using terahertz reflectometric imaging. The lacquerware studied herein comprises an ornamental wood panel covered by multiple layers of lacquers to portray motifs. For characterizing lacquerware, a terahertz time-domain spectroscopic reflectometric imaging system is proposed. The role of the proposed terahertz imaging system in highlighting the interface between layers during stratigraphic buildup in reflection geometry is proved. The proposed system provides a universal method for assessing the structural information of lacquered objects in a contactless and non-invasive manner; moreover, it provides two-dimensional images, subsurface three-dimensional images, and stratigraphic images (b-scans) in a contactless and non-invasive manner. Using the proposed system, we examine the buried layers of the lacquerware, including faults in the wooden layer and damages in the lacquerware. Research shows the promising prospects of terahertz time-domain spectroscopic reflectometric imaging as a non-destructive detection technique suited to lacquerware.

Revisiting the Vital Drivers and Mechanisms of β-Glucan Masking in Human Fungal Pathogen, Candida albicans

Among the several human fungal pathogens, Candida genus represents one of the most implicated in the clinical scenario. There exist several distinctive features that govern the establishment of Candida infections in addition to their capacity to adapt to multiple stress conditions inside humans which also include evasion of host immune responses. The complex fungal cell wall of the prevalent pathogen, Candida albicans, is one of the main targets of antifungal drugs and recognized by host immune cells. The wall consists of tiered arrangement of an outer thin but dense covering of mannan and inner buried layers of β-glucan and chitin. However, the pathogenic fungi adopt strategies to evade immune recognition by masking these molecules. This capacity to camouflage the immunogenic polysaccharide β-glucan from the host is a key virulence factor of C. albicans. The present review is an attempt to collate various underlying factors and mechanisms involved in Candida β-glucan masking from the available pool of knowledge and provide a comprehensive understanding. This will further improve therapeutic approaches to candidiasis by identifying new antifungal targets that blocks fungal immune evasion.

Stratigraphic analysis of intercalated graphite electrodes in aqueous inorganic acid solutions

A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric (HClO4) and sulfuric (H2SO4) electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions. By combining time-of-flight secondary ion mass spectrometry (ToF-SIMS) and in-situ atomic force microscopy (AFM), we provide a picture of the chemical species involved in the intercalation reaction. The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process, where the local morphology of the basal plane plays a crucial role. Solvated anions are mostly located within the first tens of nanometers of graphite, but electrolytes also diffuse inside the buried layers for hundreds of nanometers, the latter process is also aided by the presence of mesoscopic crystal defects. Residual material from the electrolyte solution was found localized in well-defined circular spots, which represent preferential interaction areas. Interestingly, blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite (HOPG) surface were found in the buried layers, confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.

Wavelength-Selective Coatings on Glass with High Hardness and Damage Resistance

Wavelength-selective coatings are broadly applied across diverse industries such as solar energy management, infrared sensing, telecommunications, laser optics, and eye-protective lenses. These coatings have historically not been optimized for hardness or mechanical durability and typically suffer from higher susceptibility to scratch and damage events than uncoated glass. In this work, we describe a family of wavelength-selective coatings with hardness and scratch resistance that are significantly higher than the chemically strengthened glass substrates on which the coatings are fabricated. The coatings are made using industrially scalable reactive sputtering methods. Wavelength-selective coatings are fabricated with nanoindentation hardness as high as 16–20 GPa over indentation depths ranging from 200 to 800 nm, as well as excellent durability in aggressive scratch testing. Tunable visible to near-infrared wavelength selectivity ratios (reflectance of stopband: reflectance of passband) as high as 7:1 are achieved. The feasibility of narrowband hard coating design is also demonstrated, with visible narrowband transmission having a peak FWHM of ~8 nm (~1.6%). A unique “buried layers” hard coating design strategy is shown to deliver particularly excellent hardness profiles. These designs can be tailored for a variety of different wavelengths and selectivity ratios, enabling new uses of wavelength-selective optics in mechanically demanding applications.

Buried Soil Carbon Vulnerability to Decomposition with Landscape Disturbance

Buried layers of ancient soil organic carbon (SOC) can store significant amounts carbon (C). Persistence of this C is favored by burial, which disconnects the soil from atmospheric conditions and limits plant derived C inputs, thus reducing microbial activity. However, erosion exposes buried paleosols to modern surface conditions and results in influx of root-derived C through the processes of root exudation and root turnover. These C inputs stimulate microbial activity and leave paleosol C vulnerable to decomposition. Understanding turnover of ancient soil C is critical for predicting the response of this large C reservoir to environmental change and feedbacks to climate. Yet, the effects of root-derived C inputs on decomposition of buried C is not well established. With this study we aim to quantify how root derived C inputs affect decomposition of paleosol C located along varying degrees of isolation from modern surface conditions, Our field site is located in Wauneta, NE where erosion has brought a Pleistocene era soil -the Brady soil- closer to the surface. We collected Brady soil from 0.2m, 0.4m, and 1.2m below the modern surface, and conducted two controlled laboratory incubations, Soils were amended with (1) a lab synthesized 13C labeled (12 atom% 13C) solution to mimic root exudates (0.3 mg C g-1 soil), and (2) root litter enriched with 92% atom% 13C (0.3mg C g-1 soil), in 30 day, and 240 day laboratory incubation experiments, respectively. We measured 13C-CO2 respiration from airtight microcosms throughout the incubations and used the isotopic label to partition between root derived C and Brady soil C respiration. Our data show that Brady soil C is highly vulnerable to decomposition via soil C priming upon addition of root-derived C regardless of burial depth, indicating that exposure of paleosols to modern surface conditions may result in a positive C cycle feedback to climate.