Investigation of the Temperature Effect on Electrical Characteristics of Al/SiO2/n++-Si RRAM Devices.

In this work, we investigate the effect of temperature on the electrical characteristics of Al/SiO2/n++-Si RRAM devices. We study the electroforming process and show that forming voltage and time-to-breakdown are well described by Weibull distribution. Experimental current-voltage characteristics of Al-SiO2-(n++Si) structures are presented and discussed at different temperatures. We show that some intermediate resistance states can be observed at higher temperatures. In our analysis, we identify Space Charge Limited Conduction (SCLC) as the dominating transport mechanism regardless of the operating temperature.

Investigation of Electrical Properties of the Al/SiO2/n++-Si Resistive Switching Structures by Means of Static, Admittance, and Impedance Spectroscopy Measurements.

In this study, the resistive switching phenomenon in Al/SiO2/n++-Si structures is observed and studied by means of DC, small-signal admittance, and complex impedance spectroscopy measurements. Possible transport mechanisms in the high and low resistance states are identified. Based on the results of the applied measurement techniques, an electrical equivalent circuit of the structure is proposed. We discuss the effect of parasitic elements influencing the measurement results and show that a proper model can give useful information about the electrical properties of the device. A good agreement between the characteristics of the proposed equivalent circuit and the experimental data, based on different measurement procedures, confirms the validity of the used methodology and its applicability to the electrical characterization of RRAMs.

Optical Properties of Site-Selectively Grown InAs/InP Quantum Dots with Predefined Positioning by Block Copolymer Lithography.

The InAs/InP quantum dots (QDs) are investigated by time-integrated (PL) and time-resolved photoluminescence (TRPL) experiments. The QDs are fabricated site-selectively by droplet epitaxy technique using block copolymer lithography. The estimated QDs surface density is ∼1.5 × 1010 cm-2. The PL emission at T=300 K is centered at 1.5 µm. Below T=250 K, the PL spectrum shows a fine structure consisting of emission modes attributed to the multimodal QDs size distribution. Temperature-dependent PL reveals negligible carrier transfer among QDs, suggesting good carrier confinement confirmed by theoretical calculations and the TRPL experiment. The PL intensity quench and related energies imply the presence of carrier losses among InP barrier states before carrier capture by QD states. The TRPL experiment highlighted the role of the carrier reservoir in InP. The elongation of PL rise time with temperature imply inefficient carrier capture from the reservoir to QDs. The TRPL experiment at T=15 K reveals the existence of two PL decay components with strong dispersion across the emission spectrum. The decay times dispersion is attributed to different electron-hole confinement regimes for the studied QDs within their broad distribution affected by the size and chemical content inhomogeneities.

Bicuspid aortic valve repair: outcomes after 17 years of experience.

OBJECTIVES: This study presents the results of 17 years of experience with bicuspid aortic valve (BAV) repair and the analysis of factors associated with repair failure and early echocardiographic outcome. METHODS: Between 2003 and 2020, a total of 206 patients [mean age: 44.5 ± 15.2 years; 152 males (74%)] with BAV insufficiency with or without aortic dilatation underwent elective aortic valve repair performed by a single surgeon with a mean follow-up of 5 ± 3.5 years. The transthoracic echocardiography examinations were reported. RESULTS: There were no deaths during the hospital stay, and all but 1 patient survived the follow-up period (99.5%). Overall, 10 patients (5%) developed severe insufficiency and 2 (1%) developed aortic dilatation requiring reoperation. Freedom from reoperation at 7 years reached 91.8%. Type 2 BAV configuration [hazard ratio (HR) 3.9; 95% confidence interval (CI): 1.01-60; P = 0.049], no sinotubular junction remodelling (HR 7; 95% CI: 1.7-23; P = 0.005), no circumferential annuloplasty (HR 3.9; 95% CI: 1.01-64; P = 0.047) and leaflet resection (HR 5.7; 95% CI 1.2-13. P = 0.017) have been identified as a risk factor of redo operation. Parameters of the postoperative left ventricle reverse remodelling improved significantly early after the operation and later at 2 years evaluation. CONCLUSIONS: The repair of BAV offers good short- and mid-term results providing a significant reverse left ventricular remodelling. Type 0 BAV preoperative configuration, circumferential annuloplasty and sinotubular junction remodelling are associated with better repair durability.

Deep snow immersion suffocation--the deadly threat.

This report presents the case of non-avalanche-related snow immersion death in the Tatra Mountains, which meets all the criteria of this rare phenomenon. The causes and mechanism of deep snow immersion suffocation as well as prevention strategies are discussed.