Topological origin of fragility, network adaptation, and rigidity and stress transitions in especially homogenized nonstoichiometric binary Ge(x)S(100-x) glasses

Chalcogenide Ovonic Threshold Switching Selector

Today's explosion of data urgently requires memory technologies capable of storing large volumes of data in shorter time frames, a feat unattainable with Flash or DRAM. Intel Optane, commonly referred to as three-dimensional phase change memory, stands out as one of the most promising candidates. The Optane with cross-point architecture is constructed through layering a storage element and a selector known as the ovonic threshold switch (OTS). The OTS device, which employs chalcogenide film, has thereby gathered increased attention in recent years. In this paper, we begin by providing a brief introduction to the discovery process of the OTS phenomenon. Subsequently, we summarize the key electrical parameters of OTS devices and delve into recent explorations of OTS materials, which are categorized as Se-based, Te-based, and S-based material systems. Furthermore, we discuss various models for the OTS switching mechanism, including field-induced nucleation model, as well as several carrier injection models. Additionally, we review the progress and innovations in OTS mechanism research. Finally, we highlight the successful application of OTS devices in three-dimensional high-density memory and offer insights into their promising performance and extensive prospects in emerging applications, such as self-selecting memory and neuromorphic computing.

Evaluation of Nano-curcumin effects against Tartrazine-induced abnormalities in liver and kidney histology and other biochemical parameters

In the current study, 40 albino male rats were investigated to evaluate the impact of Nano-curcumin (Nano-CUR) administration against Tartrazine (TZ)-induced variations in kidney and liver histology and their related functions. The liver function biomarkers are (glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transaminase (GGT), alkaline phosphatase (ALP), total bilirubin (T. BiLL)), whereas the kidney biomarkers are (creatinine, uric acid, urea, globulin, total protein (TP)), as well as blood parameters of (serum glucose (sGlu), alpha-fetoprotein (AFP), protein Kinase-C (PKC)) and lipid profiles that include (total lipids (TL), triglyceride (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density L-C (HDL-C), and very-low-density L-C (VLDL-C)). The collected rats were randomly separated into four different groups (G1, G2, G3, and G4) of 10 rats each, where G1 stands for control, G2 for TZ-ingestion, G3 for Nano-CUR-ingestion, and G4 for (TZ + Nano-CUR mix.) ingestion. TZ-ingestion significantly (p < .05) increases the liver function enzymes' activity, total bilirubin and kidney biomarkers (creatinine, urea, uric acid, total protein (TP), globulin (Glu)). Also, TZ-ingestion significantly increased sGlu, PKC, AFP, as well as lipid profiles, while there were significant (p < .05) decreases in HDL-C and albumin (Alb) concentrations compared to control. Histopathological changes in liver, such as dilatation of blood sinusoids and central vein with hemorrhage and necrosis, were observed due to TZ-ingestion. Similarly, TZ-ingestion influenced kidney tissues in terms of tubular dilatation with tubular degeneration, thickened basement membrane, and dilatation of the glomerular capillaries. Markedly, the administration of Nano-CUR significantly decreased liver and kidney function enzymes as well as sGlu, AFP, and PKC, whereas it significantly increased serum Alb and HDL-C levels compared to control and TZ-ingested rats. All values arranged around normal control values. Also, the liver tissue of Nano-CUR-ingested rats showed a normal arrangement of normal blood sinusoids(s), hepatic cords, and hepatocytes as compared to controls. The same results were also found in the section of rat kidney ingested with 2.00 g of Nano-CUR/(kg B.W.) showing near-normal architecture as compared to control rats. The liver tissue of rats ingested by a mixture of (7.5 mg of TZ + 2.0 g of Nano-CUR/kg B.W.) showed little necrosis. Similarly, a section of rat kidney ingested a mixture of (7.5 mg of TZ + 2.00 g of Nano-CUR/kg B.W.) which revealed mild tubular degeneration and dilatation of the glomerular capillaries. These results support the protective and therapeutic effects of Nano-CUR on the histology of liver and kidneys and their related function biomarkers. Also, Nano-CUR corrects the imbalance in serum glucose (sGlu), AFP, PKC, and lipid profiles in TZ-ingested rats compared to control.

Regulatory Role of Nano-Curcumin against Tartrazine-Induced Oxidative Stress, Apoptosis-Related Genes Expression, and Genotoxicity in Rats

The present study evaluates the regulatory effect of Nano-Curcumin (Nano-CUR) against tartrazine (TZ)-induced injuries on apoptosis-related gene expression (i.e., p53, CASP-3 and CASP-9), antioxidant status, and DNA damages in bone marrow in treated rats. Male rats were arbitrarily separated into five groups, and each group was comprised of 10 rats each. The 1st group served as control (G1). The 2nd group ingested 7.5 mg TZ/kg. b.w. (body weight). The 3rd group ingested Nano-CUR 1 g/kg b.w. The 4th and 5th groups were respectively administered with (1 g Nano-CUR + 7.5 mg TZ/kg. b.w.) and (2 g Nano-CUR + 7.5 mg TZ/kg. b.w.). At the end of the experiment, blood samples, livers, and kidneys were collected. Livers and kidneys were homogenized and used for the analysis of reduced glutathione, malonaldhyde, total antioxidant capacity, lipid peroxide antioxidant enzyme activities, apoptosis-related gene expression, and genotoxicity by comit test. The ingestion of TZ for 50 days resulted in significant decreases in body, and kidney weights in rats and a relative increase in the liver weight compared to control. In contrast, the ingestion of Nano-CUR with TZ remarkably upgraded the body weight and relative liver weight compared to the normal range in the control. Aditionally, TZ ingestion in rats increased the oxidative stress biomarkers lipid peroxide (LPO) and malonaldehyde (MDA) significantly, whereas it decreased the reduced glutathione (GSH) levels and total antioxidant capacity (TAC). Similarly, the levels of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) significantly deteriorated in response to TZ ingestion. Moreover, the results revealed a remarkable up-regulation in the level of expression for the three examined genes, including p53, CASP-3, and CASP-9 in TZ-ingested rats compared to the control. On the other hand, the comet assay result indicates that the ingestion of TZ induced DNA damage in bone marrow. Notably, the administration of Nano-CUR protected the kidney and liver of TZ-ingested rats as evidenced by a significant elevation in all antioxidant activities of tested enzymes (i.e, SOD, GPx, and CAT), vital recovery in GSH and TAC levels, and a statistical decrease in LPO and MDA compared to TZ-ingested rats. Interestingly, the ingestion of rats with TZ modulates the observed up-regulation in the level of expression for the chosen genes, indicating the interfering role in the signaling transduction process of TZ-mediated poisoning. The results indicate that the administration of Nano-CUR may protect against TZ-induced DNA damage in bone marrow. According to the results, Nano-CUR exerted a potential protective effect against oxidative stress, DNA damage, and the up-regulation of apoptosis-related genes induced by TZ ingested to rats.

From elemental tellurium to Ge2Sb2Te5 melts: High temperature dynamic and relaxation properties in relationship with the possible fragile to strong transition

We investigate the dynamic properties of Ge-Sb-Te phase change melts using first principles molecular dynamics with a special emphasis on the effect of tellurium composition on melt dynamics. From structural models and trajectories established previously [H. Flores-Ruiz et al., Phys. Rev. B 92, 134205 (2015)], we calculate the diffusion coefficients for the different species, the activation energies for diffusion, the Van Hove correlation, and the intermediate scattering functions able to substantiate the dynamics and relaxation behavior of the liquids as a function of temperature and composition that is also compared to experiment whenever possible. We find that the diffusion is mostly Arrhenius-like and that the addition of Ge/Sb atoms leads to a global decrease of the jump probability and to an increase in activated dynamics for diffusion. Relaxation behavior is analyzed and used in order to evaluate the possibility of a fragile to strong transition that is evidenced from the calculated high fragility (M = 129) of Ge₂Sb₂Te₅ at high temperatures.

Relaxation and physical aging in network glasses: a review

Recent progress in the description of glassy relaxation and aging are reviewed for the wide class of network-forming materials such as GeO2, Ge x Se1-x , silicates (SiO2-Na2O) or borates (B2O3-Li2O), all of which have an important usefulness in domestic, geological or optoelectronic applications. A brief introduction of the glass transition phenomenology is given, together with the salient features that are revealed both from theory and experiments. Standard experimental methods used for the characterization of the slowing down of the dynamics are reviewed. We then discuss the important role played by aspects of network topology and rigidity for the understanding of the relaxation of the glass transition, while also permitting analytical predictions of glass properties from simple and insightful models based on the network structure. We also emphasize the great utility of computer simulations which probe the dynamics at the molecular level, and permit the calculation of various structure-related functions in connection with glassy relaxation and the physics of aging which reveal the non-equilibrium nature of glasses. We discuss the notion of spatial variations of structure which leads to the concept of 'dynamic heterogeneities', and recent results in relation to this important topic for network glasses are also reviewed.

Revealing the role of molecular rigidity on the fragility evolution of glass-forming liquids

If quenched fast enough, a liquid is able to avoid crystallization and will remain in a metastable supercooled state down to the glass transition, with an important increase in viscosity upon further cooling. There are important differences in the way liquids relax as they approach the glass transition, rapid or slow variation in dynamic quantities under moderate temperature changes, and a simple means to quantify such variations is provided by the concept of fragility. Here, we report molecular dynamics simulations of a typical network-forming glass, Ge-Se, and find that the relaxation behaviour of the supercooled liquid is strongly correlated to the variation of rigidity with temperature and the spatial distribution of the corresponding topological constraints, which ultimately connect to the fragility minima. This permits extending the fragility concept to aspects of topology/rigidity, and to the degree of homogeneity of the atomic-scale interactions for a variety of structural glasses.

Structural singularities in Ge(x)Te(100-x) films

Structural and calorimetric investigation of Ge(x)Te(100-x) films over wide range of concentration 10 < x < 50 led to evidence two structural singularities at x ∼ 22 at. % and x ∼ 33-35 at. %. Analysis of bond distribution, bond variability, and glass thermal stability led to conclude to the origin of the first singularity being the flexible/rigid transition proposed in the framework of rigidity model and the origin of the second one being the disappearance of the undercooled region resulting in amorphous materials with statistical distributions of bonds. While the first singularity signs the onset of the Ge-Ge homopolar bonds, the second is related to compositions where enhanced Ge-Ge correlations at intermediate lengthscales (7.7 Å) are observed. These two threshold compositions correspond to recently reported resistance drift threshold compositions, an important support for models pointing the breaking of homopolar Ge-Ge bonds as the main phenomenon behind the ageing of phase change materials.