Schottky barrier diodes from semiconducting polymers

Schottky barrier diodes based on Al/poly(3-methylthiophene)/Au have been fabricated and their electrical behaviour investigated. I-V characteristics revealed a dependence on the fabrication conditions, specifically on the time under vacuum prior to evaporation of the rectifying contact and post-metal annealing at elevated temperature. The available evidence is consistent with the formation of a thin insulating layer between the metal and the polymer following these procedures. Long periods under vacuum prior to deposition of the aluminium electrode reduced the likelihood of such a layer forming. Capacitance-voltage plots of the devices were stable to voltage cycling, so long as the forward voltage did not exceed similar to 1 V. Above this a small degree of hysteresis was observed, which is attributed to the filling/emptying of interface states or traps in the polymer.

Trapping phenomena in AlGaN and InAlN barrier HEMTs with different geometries

PAPER Trapping phenomena in AlGaN and InAlN barrier HEMTs with different geometries S Martin-Horcajo1, A Wang1, A Bosca1, M F Romero1, M J Tadjer1,2, A D Koehler2, T J Anderson2 and F Calle1 Published 11 February 2015 • © 2015 IOP Publishing Ltd Semiconductor Science and Technology, Volume 30, Number 3 Article PDF Figures References Citations Metrics 350 Total downloads Cited by 1 articles Export citation and abstract BibTeX RIS Turn on MathJax Share this article Article information Abstract Trapping effects were evaluated by means of pulsed measurements under different quiescent biases for GaN/AlGaN/GaN and GaN/InAlN/GaN. It was found that devices with an AlGaN barrier underwent an increase in the on-resistance, and a drain current and transconductance reduction without measurable threshold voltage change, suggesting the location of the traps in the gate-drain access region. In contrast, devices with an InAlN barrier showed a transconductance and a decrease in drain associated with a significant positive shift of threshold voltage, indicating that the traps were likely located under the gate region; as well as an on-resistance degradation probably associated with the presence of surface traps in the gate-drain access region. Furthermore, measurements of drain current transients at different ambient temperatures revealed that the activation energy of electron traps was 0.43 eV and 0.38 eV for AlGaN and InAlN barrier devices, respectively. Experimental and simulation results demonstrated the influence of device geometry on the observed trapping effects, since devices with larger gate lengths and gate-to-drain distance values exhibited less noticeable charge trapping effects.

DLTS investigation of acceptor states in P3MeT Schottky barrier diodes

Deep Level Transient Spectroscopy (DLTS) has been used to investigate hole traps in the depletion region of Schottky barrier diodes formed from electropolymerised poly(3-methylthiophene). The capacitance transients appear to be composed of a fast and a slow component. Analysis of the slower component using the ''rate window'' technique yields isochronal differential capacitance curves that depend on temperature in the manner predicted by theory.

Charge transport in poly(3-methylthiophene) schottky barrier diodes

Schottky-barrier devices were formed from electropolymerised films of poly (3-methylthiophene) (PMeT). Thermal annealing of a partially undoped film led to diodes with rectification ratios as high as 5900 at 1 V and 50,000 at 2.5 V and ideality factors slightly above 2. The temperature dependence of ac loss tangent and forward currents are identical suggesting that bulk effects dominate device behaviour event at very low forward voltages. Below 250 K forward currents are essentially independent of temperature. Preliminary TSC measurements show the presence of at least two trapping levels in the devices. © 1993.

Photocurrents in P3MeT Schottky barrier diodes

The photocurrent action spectrum of a Schottky diode formed from electrodeposited poly(3-methylthiophene) is shown to follow closely the UV-visible absorption spectrum. At low forward bias, the peak photocurrent asymptotes to the expected square-root dependence on total potential, V-t, across the depletion region. At high reverse bias the superlinear dependence of the photocurrent on V-t suggests that internal photoemission from the rectifying aluminium electrode may be the dominant process.

Interface state mapping in a Schottky barrier of the organic semiconductor terrylene

In this work we quantitatively map interface states in energy in a Schottky barrier between aluminum and the vacuum sublimed organic semiconductor terrylene. The density map of these interface states was extracted from the, admittance spectroscopy data. They revealed an interface state density of 2 x 10(12). cm(-2)eV(-1) close to the valence band which decreases slightly towards midgap. Additional do measurements show that the semiconductor bulk activation energy is 0.33 eV which may correspond to an acceptor level. (C) 2002 Elsevier Science B.V. All rights reserved.

Schottky barrier diodes from semiconducting polymers

Schottky barrier diodes based on Al/poly(3-methylthiophene)/Au have been fabricated and their electrical behaviour investigated. I-V characteristics revealed a dependence on the fabrication conditions, specifically on the time under vacuum prior to evaporation of the rectifying contact and post-metal annealing at elevated temperature. The available evidence is consistent with the formation of a thin insulating layer between the metal and the polymer following these procedures. Long periods under vacuum prior to deposition of the aluminium electrode reduced the likelihood of such a layer forming. Capacitance-voltage plots of the devices were stable to voltage cycling, so long as the forward voltage did not exceed similar to 1 V. Above this a small degree of hysteresis was observed, which is attributed to the filling/emptying of interface states or traps in the polymer.

Trattamento plasma assistito di acqua con una sorgente Dielectric Barrier Discharge (DBD): analisi delle specie reattive prodotte e potere battericida

La proliferazione di batteri in liquido è una problematica che riguarda anche le acque di fiumi e mari. In questo progetto di tesi sperimentale si indagherà un trattamento plasma assistito diretto di acqua sintetica riprodotta in laboratorio con l’obiettivo di ottenere un effetto battericida sul liquido contaminato. L’acqua trattata verrà analizzata chimicamente, in particolare si andranno a misurare i TRO (Total Residual Oxidant, composti dell’ossigeno derivanti dalla parziale ozonizzazione dell’acqua) che dovranno essere presenti in quantità minori di 0,1 mg/l. Il dispositivo utilizzato per i test biologici è una sorgente di tipologia DBD (Dielectric Barrier Discharge) indiretto. Gli elettrodi della sorgente sono separati dal solo strato di materiale dielettrico e uno di questi è composto da una rete metallica in acciaio inossidabile. Il plasma si forma tra le maglie della rete e induce la formazione di specie reattive, radiazioni UV, particelle cariche, campi elettromagnetici e calore. Ciò che raggiunge la soluzione contaminata è l’afterglow del plasma, ovvero tutte le specie reattive a lunga vita prodotte dalla ionizzazione dell’aria e dalle radiazioni UV. La sorgente è stata dapprima caratterizzata elettricamente studiando le forme d’onda di tensione e corrente a determinate condizioni operative. Il liquido da trattare è contaminato con il batterio Escherichia coli. è emerso che in tutti i casi testati i livelli degli ossidanti sono entro il limite prestabilito di 0,1 mg/l. Il trattamento plasma in soli 10 secondi è responsabile di una decontaminazione parziale del batterio E. coli. Da ulteriori studi si potranno trovare delle condizioni tali da inattivare totalmente la carica batterica presente date le grandi potenzialità di questo trattamento.

Barrier Island Response to Sea Level Rise in North Carolina

The state of North Carolina is home to some of the most spectacular barrier islands in the world. These features are constantly shifting, impacted by waves, tides, and wind. Studies of the Outer Banks, North Carolina have resulted in varied results, but a detailed analysis of the barrier system as a whole is lacking. Using historic topographic surveys (T-sheets) from the 19th, the positions of various barrier segments were analyzed in relation to modern imagery. Changes in area, width, and center line locations were evaluated over the past 150 years. In total, 74 percent of modern transects have decreased in area. Total reductions in size were 130 km2 for the study period. Mean centerlines as a function of migration showed that 53 percent of segments were demonstrating directional movement away from the ocean. The average movement towards the bay between modern and historic centerlines was 8 meters. Thusly, barrier islands in North Carolina are demonstrating both decreases in total area and directional movement inland in response to sea level rise.

Phytochemical mediated-modulation of the expression and transporter function of breast cancer resistance protein at the blood-brain barrier:an in-vitro study

Clinical translation of BCRP inhibitors have failed due to neurotoxicity and novel approaches are required to identify suitable modulators of BCRP to enhance CNS drug delivery. In this study we examine 18 compounds, primarily phytochemicals, as potential novel modulators of AhR-mediated regulation of BCRP expression and function in immortalised and primary porcine brain microvascular endothelial cells as a mechanism to enhance CNS drug delivery. The majority of modulators possessed a cellular viability IC50 > 100 µM in both cell systems. BCRP activity, when exposed to modulators for 1 hour, was diminished for most modulators through significant increases in H33342 accumulation at < 10 µM with 2,6,4-trimethoflavone increasing H33342 intracellular accumulation by 3.7–6.6 fold over 1–100 µM. Western blotting and qPCR identified two inducers of BCRP (quercetin and naringin) and two down-regulators (17-β-estradiol and curcumin) with associated changes in BCRP efflux transport function further confirmed in both cell lines. siRNA downregulation of AhR resulted in a 1.75 ± 0.08 fold change in BCRP expression, confirming the role of AhR in the regulation of BCRP. These findings establish the regulatory role AhR of in controlling BCRP expression at the BBB and confirm quercetin, naringin, 17-β-estradiol, and curcumin as novel inducers and down-regulators of BCRP gene, protein expression and functional transporter activity and hence potential novel target sites and candidates for enhancing CNS drug delivery.

Monitoring and modelling the morphodynamic evolution of a breached barrier beach system

Predicting the evolution of a coastal cell requires the identification of the key drivers of morphology. Soft coastlines are naturally dynamic but severe storm events and even human intervention can accelerate any changes that are occurring. However, when erosive events such as barrier breaching occur with no obvious contributory factors, a deeper understanding of the underlying coastal processes is required. Ideally conclusions on morphological drivers should be drawn from field data collection and remote sensing over a long period of time. Unfortunately, when the Rossbeigh barrier beach in Dingle Bay, County Kerry, began to erode rapidly in the early 2000’s, eventually leading to it breaching in 2008, no such baseline data existed. This thesis presents a study of the morphodynamic evolution of the Inner Dingle Bay coastal system. The study combines existing coastal zone analysis approaches with experimental field data collection techniques and a novel approach to long term morphodynamic modelling to predict the evolution of the barrier beach inlet system. A conceptual model describing the long term evolution of Inner Dingle Bay in 5 stages post breaching was developed. The dominant coastal processes driving the evolution of the coastal system were identified and quantified. A new methodology of long term process based numerical modelling approach to coastal evolution was developed. This method was used to predict over 20 years of coastal evolution in Inner Dingle Bay. On a broader context this thesis utilised several experimental coastal zone data collection and analysis methods such as ocean radar and grain size trend analysis. These were applied during the study and their suitability to a dynamic coastal system was assessed.

Effects of plasticizing and crosslinking on the mechanical and barrier properties of coatings based on blends of starch and poly(vinyl alcohol)

In the last decades, intensive research has been carried out in order to replace oil-based polymers with bio-based polymers due to growing environmental concerns. So far, most of the barrier materials used in food packaging are petroleum-based materials. The purpose of the barrier is to protect the packaged food from oxygen, water vapour, water and fat. The mechanical and barrier properties of coatings based on starch-plasticizer and starch-poly(vinyl alcohol) (PVOH)-plasticizer blends have been studied in the work described in this thesis. The plasticizers used were glycerol, polyethylene glycol and citric acid. In a second step, polyethylene coatings were extruded onto paperboard pre-coated with a starch-PVOH-plasticizer blend. The addition of PVOH to the starch increased the flexibility of the film. Curing of the film led to a decrease in flexibility and an increase in tensile strength. The flexibility of the starch-PVOH films was increased more when glycerol or polyethylene glycol was added than citric acid. The storage modulus of the starch-PVOH films containing citric acid increased substantially at high temperature. It was seen that the addition of polyethylene glycol or citric acid to the starch-PVOH blend resulted in an enrichment of PVOH at the surface of the films. Tensile tests on the films indicated that citric acid acted as a compatibilizer and increased the compatibility of the starch and PVOH in the blend. The addition of citric acid to the coating recipe substantially decreased the water vapour transmission rate through the starch-PVOH coated paperboard, which indicated that citric acid acts as a cross-linker for starch and/or PVOH. The starch-PVOH coatings containing citric acid showed oxygen-barrier properties similar to those of pure PVOH or of a starch-PVOH blend without plasticizer when four coating layers were applied on a paperboard. The oxygen-barrier properties of coatings based on a starch-PVOH blend containing citric acid indicated a cross-linking and increase in compatibility of the starch-PVOH blends. Polyethylene extrusion coating on a pre-coated paperboard resulted in a clear reduction in the oxygen transmission rate for all the pre-coating formulations containing plasticizers. The addition of a plasticizer to the pre-coating reduced the adhesion of polyethylene to pre-coated board. Polyethylene extrusion coating gave a board with a lower oxygen transmission rate when the paperboard was pre-coated with a polyethylene-glycol-containing formulation than with a citric-acid-containing formulation. The addition of polyethylene glycol to pre-coatings indicated an increase in wetting of the pre-coated paperboard by the polyethylene melt, and this may have sealed the small defects in the pre-coating leading to low oxygen transmission rate. The increase in brittleness of starch-PVOH films containing citric acid at a high temperature seemed to have a dominating effect on the barrier properties developed by the extrusion coating process. 

SCDOT Qualified Product List 49 - Permanent Traffic Barrier Components

The South Carolina Department of Transportation publishes Qualified Products Listings which include pre-qualified materials that may be used on construction and maintenance projects as specified in the project proposal. This document deals with permanent traffic barrier components.

Natural Wax-Based Water Vapour Barrier Coatings on PLA for MAP Food Packaging

PLA is a bio-based polymer that is obtained from renewable resources and it is very promising for a sustainable packaging manufacturing. However, its gas and vapour barrier properties are not enough to comply with the requirements of MAP packaging of fresh foods, which need specific concentration of water and oxygen to avoid spoilage and to keep the organoleptic properties unaltered throughout their shelf-life. The use of waxes from natural renewable sources such as plants (e.g., candelilla wax, carnauba wax, rice bran wax, sunflower wax) or animals (e.g., beeswax) could tackle down the permeation of water vapour through the packaging without affecting its bio-based content. The core of this work is developing wax-based coatings with enhanced thermo-mechanical properties so that they can undergo thermoforming and a proper adhesion to the PLA substrate can be ensured. Chemical modifications and crosslinking of waxes are performed to produce wax-based alkyd resins. The synthesised materials are characterised both by DSC and FTIR. Films of the wax-based alkyds are produced in order to assess their water vapour permeability.