Search results for "layer"

Electrochemically prepared oxides for resistive switching memories

2018

Redox-based resistive switching memories (ReRAMs) are the strongest candidates for next generation nonvolatile memories. These devices are commonly composed of metal/solid electrolyte/metal junctions, where the solid electrolyte is usually an oxide layer. A key aspect in the ReRAMs development is the solid electrolyte engineering, since it is crucial to tailor the material properties for obtaining excellent switching properties (e.g. retention, endurance, etc.). Here we present an anodizing process as a non vacuum and low temperature electrochemical technique for growing oxides with tailored structural and electronic properties. The effect of the anodizing conditions on the solid state prop…

Low Temperature, Vacuum-Processed Bismuth Triiodide Solar Cells with Organic Small-Molecule Hole Transport Bilayer

2021

Herein, the preparation of fully vacuum-processed bismuth triiodide solar cells with low annealing temperature is reported. Planar n-i-p devices are prepared using a thin compact SnO2 layer as the electron extraction layer and an electron blocking/hole extraction bilayer consisting of an intrinsic and doped organic hole-transport molecule. Using this configuration, herein, higher fill-factors and overall power conversion efficiencies than with conventional solution-processed hole transport materials are achieved.

Tenfold increase in efficiency from a reference blue OLED

2018

Abstract Starting from a reference single-layer light-emitting diode based on the blue phosphorescent bis-cyclometallated iridium complex FIrpic as guest, hosted in a PVK (non-conjugated poly(vynilcarbazole)) matrix, different strategies are followed to improve the efficiency of the devices through the combination of solution processed and evaporated layers. Injection of charges from the electrodes has been varied by using different conductive PEDOT: PSS as hole injection layer and a nanoscale Cs2CO3 interlayer as electron injection and hole-blocking film. Furthermore, a separated electron injection/hole blocking evaporated layer, TPBi or 3TPYMB, is introduced in double-layer devices to enh…

Seedless assembly of colloidal crystals by inverted micro-fluidic pumping

2018

We propose a simple seedless approach to assemble millimeter sized monolayer single colloidal crystals with desired orientations at predetermined locations on an unstructured charged substrate. This approach utilizes the millimeter-ranged fluid flow on the bottom glass substrate induced by an ion exchange resin (IEX) fixed on top of the closed sample cell. This fluid flow increases with decreasing height of the sample cell and increasing radius R of the IEX. For a single inverted pump, millimeter sized monolayer single crystals of hexagonal close packing can be obtained. For two closely spaced (D ~ 4R) pumps, the formed crystals have a predefined orientation along the line connecting the tw…

Continuous‐Flow Synthesis of High‐Quality Few‐Layer Antimonene Hexagons

2021

2D materials show outstanding properties that can bring many applications in different technological fields. However, their uses are still limited by production methods. In this context, antimonene is recently suggested as a new 2D material to fabricate different (opto)electronic devices, among other potential applications. This work focuses on optimizing the synthetic parameters to produce high-quality antimonene hexagons and their implementation in a large-scale manufacturing procedure. By means of a continuous-flow synthesis, few-layer antimonene hexagons with ultra-large lateral dimensions (up to several microns) and a few nanometers thick are isolated. The suitable chemical post-treatm…

In vivo morphological and clinical effects of a desensitizing agent

2010

Objectives: This study evaluated the in vivo effectiveness of Universal Dentin Sealant (UDS), a new resin-based material, as dentinal desensitizing agent on dentin morphology and clinical symptoms. Materials and methods: Thirty premolars, exhibiting non-carious cervical lesions, and scheduled for extraction for periodontal reasons, were selected for the ultrastructural study. These samples were randomly divided into three groups ( n = 10): group 1, brushing with UDS; group 2, brushing with Flor-Opal ® Varnish (FOV); and group 3, untreated control. After 7 days, teeth were extracted and samples processed for SEM and TEM comparative observations. The in vivo study was carried out on 90 teeth …

Comparison of two portable solid state detectors with an improved collimation and alignment device for mammographic x-ray spectroscopy

2006

We describe a portable system for mammographic x-ray spectroscopy, based on a 2 X 2 X 1 mm3 cadmium telluride (CdTe) solid state detector, that is greatly improved over a similar system based on a 3 X 3 X 2 mm3 cadmium zinc telluride (CZT) solid state detector evaluated in an earlier work. The CdTe system utilized new pinhole collimators and an alignment device that facilitated measurement of mammographic x-ray spectra. Mammographic x-ray spectra acquired by each system were comparable. Half value layer measurements obtained using an ion chamber agreed closely with those derived from the x-ray spectra measured by either detector. The faster electronics and other features of the CdTe detecto…

2021

Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS2 exfoliated on ultraflat Au films (0.16-0.21 nm roughness) and finally transferred to an i…

Deformation-Free Topography from Combined Scanning Force and Tunnelling Experiments

1993

We show that by measuring force and stiffness on a constant-current scanning tunnelling microscopy (STM) contour a deformation-free topography can be extracted. With reference to mono- and bicomponent self-assembled monolayers, we find that the characteristic depression pattern and the protrusions on a multicomponent film found in STM are to a great extent due to electronic effects.

Effect of humidity on the hysteresis of single walled carbon nanotube field-effect transistors

2008

Single walled carbon nanotube field-effedt transistores (SWCNT FETs) are attributed as possible building blocks for future molecular electronics. But often these transistors seem to randomly display hysteresis in their transfer characteristics. One reason for this is suggested to be water molecules adsorbed to the surface of the gate dielectric in this study we investigate the thysteresis of SWCNT FETs at different relative humidities. We find that SWCNT FETs having atomic layer deposited (ALD) Hf0 2 -Ti0 2 .- Hf0 2 as a gate dielectric retain their. ambient condition hysteresis better in dry N2 environment than the more commonly used SiO 2 gate oxide.