Structure of SnF2-SnO-P2O5 Glasses

AbstractLow melting point glasses, specifically tin fluorophosphates, have recently received attention as a successful host matrix to rare earth metals to be used in photon conversion for solar cell applications. We have used high resolution X-ray photoelectron spectroscopy and Raman microscopy to investigate the structure of 50SnF2-20SnO-30P2O5 glass. To compliment this experimental study density functional theory was used to predict Raman spectra. The O 1s X-ray photoelectron spectra indicate a high non-bridging to bridging oxygen ratio, a sign of relatively high durability needed for this glass to be applied to solar energy. The experimental results are in good agreement with theoretical calculations

Parametrizace fotosvětlání a fototmavnutí in-situ kinetik v napařených vrstvách GeSe2

Thermally evaporated chalcogenide glass thin films are known to be highly photosensitive revealing both metastable and transient photoinduced changes of optical transmission at the fundamental absorption edge region. In-situ kinetics of metastable photobleaching and transient photodarkening as well as following light-off relaxations for as-deposited GeSe2 thin films were studied and fitted with the stretched exponential function. Dependences of kinetic parameters beta and tau a on film thickness, temperature, sample prehistory and wavelength of light irradiation were analyzed. The obtained results were discussed within current approaches to mechanisms of photoinduced kinetic phenomena and structural relaxation in glasses.Vakuově napařené tenké vrstvy chalkogenidových skel jsou známé pro svoji vysokou fotocitlivost odhalující metastabilní a přechodné fotoindukované změny optické propustnosti v regionu fundamentální absorpční hrany. Byly studovány a fitovány n-situ kinetiky metastabilního fotosvětlání a přechodného fototmavnutí čerstvě deponovaných vrstev GeSe2, jakožto i relaxace při vypnutí zdroje expozice. Byla analyzována závislost parametrů kinetiky beta a tau na tloušťce, teplotě, historii vzorku a vlnové délce použitého záření. Získané výsledky byly diskutovány v rámci současných přístupů k mechanismům fotoindukovaných jevů a strukturální relaxace ve sklech

Foto-odezva anorganicko-organických tenkovrstevnatých kompozitů na bázi chalkogenidových skel

Spin coated chalcogenide thin films have different structural and chemical properties than the films obtained by traditional methods such as thermal evaporation or sputtering. The solution-based method provides lower sensitivity of glass matrix to the influence of bandgap and superbandgap light. This property is very useful for non-linear optical applications based on high transparency of these materials in infrared spectral region. Arsenic selenide spin coated thin films were obtained by chemical dissolution of bulk glasses in ethylenediamine. The influence of preparation conditions, especially the annealing temperatures at the final stage of thin films synthesis, on in-situ kinetics of photodarkening (bleaching) at various energies and intensities of UV-VIS light was studied. It was found that at certain annealing conditions only transient photoinduced effects can be obtained by eliminating metastable kinetic component. Mechanisms of the photoinduced effects are discussed based on the parameters of relaxation functions.Spin-coatingem deponované chalkogenidové tenké vrstvy mají rozdílnou strukturu a chemické vlastnosti než vrstvy získané tradičními metodami jako je vakuové napařování nebo naprašování. Roztokové depoziční metody poskytují nižší citlivost skelné matrice vůči účinku světla o bandgapových a superbandgapových energií. Tato vlastnost je velice užitečná pro nelineární optické aplikace založené na vysoké propustnosti těchto materiálů v IČ oblasti spektra. Tenké vrstvy selenidu arsenitého byly získány rozpouštěním objemového skla v etylendiaminu. Vliv podmínek během přípravy, zvláště pak teplota temperace v posledních fází přípravy vrstev, na in-situ kinetiky fototmavnutí (světlání) při různých energiích a intenzitách UV-VIS táření byly studovány v této práci. Bylo zjištěno, že pouze při určitých podmínkách temperace lze získat vratné fotoindukované změny díky eliminaci metastabilní kinetické komponenty. Mechanismus fotoindukovaných jevů je dále diskutován na základě parametrů relaxačních funkcí

Strukturní původ povrchových transformací v tenkých vrstvách sulfidu arsenitého vyvolaných UV expozicí

Photostructural transformations within AsxS100-x (x = 30, 33, 35, 40) thin films upon exposure to LED light of different wavelengths, in both air and argon environments have been studied by high resolution XPS, Raman spectroscopy and LEIS methods. These complementary results show that light of energies close to the band gap does not modify chemical composition of the surface, but induces simple photopolymerization reactions. Superbandgap UV light, however, significantly increases S/As ratio on the surface due to formation of S-rich layer under both environmental conditions. It is proposed that photovaporization of both oxide and non-oxide cage-like molecules is responsible for the observed effect.Fotostrukturální tranformace ve vrstvách AsxS100-x (x = 30, 33, 35, 40) vyvolané vlivem expozice LED zářením různých vlnových délek jak na vzduchu, tak i v argonu byla studována metodou XPS, Ramanovou spektroskopií a metodou LEIS. Tyto komplementární výsledky ukazují, že světlo o energii blízké optické šířce zakázaného pásu nemění chemické složení povrchu, ale indukuje jednoduché fotopolymerizační reakce. UV záření však výrazně zvyšuje poměr As/S na povrchu materiálu díky formaci na síru bohaté vrstvy v obou použitých prostředích. Za účelem vysvětlení pozorovaných změn byl navržen mechanismus fotoindukovaného odparu jak oxidových, tak i neoxidových molekul (ve tvaru klece)

Effect of Bi Additive on the Physical Properties of Ge2Se3-Based Equichalcogenide Glasses and Thin Films

International audienceThe influence of Bi on the structure and physical properties of Ge2Se3-based equichalcogenide glasses and thin films is studied. Thermal analysis shows increased crystallization ability for Bi-modified glasses. Direct current (DC) and alternating current (AC) electrical conductivity for bulk glasses and thin films is investigated in a broad range of temperatures and frequencies, showing a strong dependence on the presence of Bi modifiers. Exposure wavelength dependence of photocurrent is studied at different temperatures for the visible range of spectrum, and correlated with the existence of localized states in the mobility gap of these amorphous semiconductors. Structural peculiarities of the obtained thin films and bulk samples are assessed from X-ray diffraction (XRD) and high-resolution X-ray photoelectron spectroscopy (XPS) measurements. Optical, electrical, and thermal properties are shown to be suitable for various applications in photonics, electronics, and sensor systems

Broadband Photosensitive Medium Based on Amorphous Equichalcogenides

International audienceA photosensitive medium based on amorphous equichalcogenide thin films containing germanium and antimony is proposed with characteristics promising for applications in all-chalcogenide photonics, sensors, and photovoltaics. Optical properties, temperature, and exposure wavelength dependence of DC electrical conductivity are shown to be comparable with those for halide perovskites, which potentially makes amorphous equichalcogenides a very attractive alternative. The change in dark resistivity with temperature is found to follow exponential decay, covering 2 orders of magnitude over a 70 K temperature interval. Light exposure leads to several orders of relative changes in a current when compared to its dark value. A strong photocurrent response is observed under low power (milliwatts range) exposure across the entire 400-1000 nm range of the investigated wavelengths. An increase in temperature leads to a decrease in the photoresponse of the developed material, which is found to vanish at temperatures higher than 120 degrees C when only a few milliwatts of exposure power is used

Phase-change materials based on amorphous equichalcogenides

International audiencePhase-change materials, demonstrating a rapid switching between two distinct states with a sharp contrast in electrical, optical or magnetic properties, are vital for modern photonic and electronic devices. To date, this effect is observed in chalcogenide compounds based on Se, Te or both, and most recently in stoichiometric Sb(2)S(3) composition. Yet, to achieve best integrability into modern photonics and electronics, the mixed S/Se/Te phase change medium is needed, which would allow a wide tuning range for such important physical properties as vitreous phase stability, radiation and photo-sensitivity, optical gap, electrical and thermal conductivity, non-linear optical effects, as well as the possibility of structural modification at nanoscale. In this work, a thermally-induced high-to-low resistivity switching below 200 °C is demonstrated in Sb-rich equichalcogenides (containing S, Se and Te in equal proportions). The nanoscale mechanism is associated with interchange between tetrahedral and octahedral coordination of Ge and Sb atoms, substitution of Te in the nearest Ge environment by S or Se, and Sb-Ge/Sb bonds formation upon further annealing. The material can be integrated into chalcogenide-based multifunctional platforms, neuromorphic computational systems, photonic devices and sensors

Outcomes in Newly Diagnosed Atrial Fibrillation and History of Acute Coronary Syndromes: Insights from GARFIELD-AF

BACKGROUND: Many patients with atrial fibrillation have concomitant coronary artery disease with or without acute coronary syndromes and are in need of additional antithrombotic therapy. There are few data on the long-term clinical outcome of atrial fibrillation patients with a history of acute coronary syndrome. This is a 2-year study of atrial fibrillation patients with or without a history of acute coronary syndromes