All van der Waals Semiconducting PtSe2 Field Effect Transistors with Low Contact Resistance Graphite Electrodes.

Contact resistance is a multifaceted challenge faced by the 2D materials community. Large Schottky barrier heights and gap-state pinning are active obstacles that require an integrated approach to achieve the development of high-performance electronic devices based on 2D materials. In this work, we present semiconducting PtSe2 field effect transistors with all-van-der-Waals electrode and dielectric interfaces. We use graphite contacts, which enable high ION/IOFF ratios up to 109 with currents above 100 µA µm-1 and mobilities of 50 cm2 V-1 s-1 at room temperature and over 400 cm2 V-1 s-1 at 10 K. The devices exhibit high stability with a maximum hysteresis width below 36 mV nm-1. The contact resistance at the graphite-PtSe2 interface is found to be below 700 Ω µm. Our results present PtSe2 as a promising candidate for the realization of high-performance 2D circuits built solely with 2D materials.

Acute kidney injury after arterial switch operation: incidence, risk factors, clinical impact - a retrospective single-center study.

BACKGROUND: This retrospective study aimed to determine the incidence, risk factors, and outcomes of acute kidney injury (AKI) in neonates following the arterial switch operation (ASO) for transposition of great arteries (TGA). METHODS: Retrospective review of medical data of children who underwent ASO in 2019-2020 in the Ukrainian Children's Cardiac Center. RESULTS: 76 consecutive neonatal patients were included, 48 developed AKI after ASO (51.7%), and 24 - had severe AKI (25.8%). Severe AKI development was associated with longer cross-clamp time: 82 (61-127) versus 73.5 (53-136) in the non-severe AKI group (p = 0.02). 76 min of cross-clamp time were defined as a threshold value for increased severe AKI risk, OR 4.4 (95% CI: 1.5 - 13, p = 0.01). Higher lactate levels during cardiopulmonary bypass (CPB) increased severe AKI development risk, OR 1.5 (95% CI: 1.0 - 2.0, p = 0.03). Children with severe AKI had prolonged mechanical ventilation, longer time to negative fluid balance, and higher postoperative day 3 (POD3) Inotropic Score (IS). Only one patient required peritoneal dialysis. CONCLUSIONS: In our study, 51.7% of patients developed AKI after ASO, 25.8%-severe AKI. Prolonged cross-clamp time and higher lactate levels during cardiopulmonary bypass increased the risk for severe AKI development. The development of AKI was associated with prolonged mechanical ventilation, longer time to negative fluid balance, higher POD 3 Inotropic Score.

Multi-Layer Palladium Diselenide as a Contact Material for Two-Dimensional Tungsten Diselenide Field-Effect Transistors.

Tungsten diselenide (WSe2) has emerged as a promising ambipolar semiconductor material for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band gap, high carrier mobility, and remarkable on-off ratio. However, engineering the contacts to WSe2 remains an issue, and high contact barriers prevent the utilization of the full performance in electronic applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or hole injection and consequently pin the threshold voltage to either conduction or valence band. This would be the way to achieve complementary metal-oxide-semiconductor devices without doping of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material. This consequently yields high-performance p-type WSe2 devices with PdSe2 van der Waals contacts. Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2 under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding pure p-type operation of the devices.

Enhancement of Charge Transport in Polythiophene Semiconducting Polymer by Blending with Graphene Nanoparticles.

This paper describes a study on the charge transport in a composite of liquid-exfoliated graphene nanoparticles (GNPs) and a polythiophene semiconducting polymer. While the former component is highly conducting, although it consists of isolated nanostructures, the latter offers an efficient charge transport path between the individual GNPs within the film, overall yielding enhanced charge transport properties of the resulting bi-component system. The electrical characteristics of the composite layers were investigated by means of measurements of time-of-flight photoconductivity and transconductance in field-effect transistors. In order to analyze both phenomena separately, charge density and charge mobility contributions to the conductivity were singled out. With the increasing GNP concentration, the charge mobility was found to increase, thereby reducing the time spent by the carriers on the polymer chains. In addition, for GNP loading above 0.2 % (wt.), an increase of free charge density was observed that highlights an additional key role played by doping. Variable-range hopping model of a mixed two- and three-dimensional transport is explained using temperature dependence of mobility and free charge density. The temperature variation of free charge density was related to the electron transfer from polythiophene to GNP, with an energy barrier of 24 meV.