Diamond-based electrodes for organic photovoltaic devices

The present paper demonstrates the possibility of replacing indium–tin oxide (ITO) with heavily boron-doped diamond (BDD). Plasma Enhanced Chemically Vapor Deposited BDDs layers of various thicknesses were prepared containing various boron concentrations in a gas phase. The dependence of the above-mentioned parameters on the optical and electrical properties of each BDD was studied in order to achieve optimal conditions for the effective application of diamond electrodes in organic electronics as a replacement for ITO. Bulk-heterojunction polymer–fullerene organic solar cells were fabricated to test the potency of BDD application in photovoltaic devices. The obtained results demonstrated the possibility of the aforementioned application. Even though the efficiency of BDD-based devices is lower compared to those using regular ITO-based architecture, the relevant issues were explained

Nanocrystalline diamond protects Zr cladding surface against oxygen and hydrogen uptake : Nuclear fuel durability enhancement

In this work, we demonstrate and describe an effective method of protecting zirconium fuel cladding against oxygen and hydrogen uptake at both accident and working temperatures in water-cooled nuclear reactor environments. Zr alloy samples were coated with nanocrystalline diamond (NCD) layers of different thicknesses, grown in a microwave plasma chemical vapor deposition apparatus. In addition to showing that such an NCD layer prevents the Zr alloy from directly interacting with water, we show that carbon released from the NCD film enters the underlying Zr material and changes its properties, such that uptake of oxygen and hydrogen is significantly decreased. After 100–170 days of exposure to hot water at 360 °C, the oxidation of the NCD-coated Zr plates was typically decreased by 40%. Protective NCD layers may prolong the lifetime of nuclear cladding and consequently enhance nuclear fuel burnup. NCD may also serve as a passive element for nuclear safety. NCD-coated ZIRLO claddings have been selected as a candidate for Accident Tolerant Fuel in commercially operated reactors in 2020

Physical Properties Investigation of Reduced Graphene Oxide Thin Films Prepared by Material Inkjet Printing

The article is focused on the study of the optical properties of inkjet-printed graphene oxide (GO) layers by spectroscopic ellipsometry. Due to its unique optical and electrical properties, GO can be used as, for example, a transparent and flexible electrode material in organic and printed electronics. Spectroscopic ellipsometry was used to characterize the optical response of the GO layer and its reduced form (rGO, obtainable, for example, by reduction of prepared layers by either annealing, UV radiation, or chemical reduction) in the visible range. The thicknesses of the layers were determined by a mechanical profilometer and used as an input parameter for optical modeling. Ellipsometric spectra were analyzed according to the dispersion model and the influence of the reduction of GO on optical constants is discussed. Thus, detailed analysis of the ellipsometric data provides a unique tool for qualitative and also quantitative description of the optical properties of GO thin films for electronic applications

Electroluminescence of thin film

Hydrogenated amorphous substoichiometric silicon carbon alloys (a-SiC:H) with and without embedded Ge nanoparticles (NPs) have been prepared by plasma enhanced chemical vapour deposition combined with in-situ Ge evaporation and annealing on semi-transparent boron doped nano-crystalline diamond coated Ti grids. The presence of Ge NPs embedded in the amorphous phase has been confirmed by transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses. Current-voltage (I–V) characteristics and near infrared electroluminescence (EL) spectra were measured to compare performance of diodes. The relatively strong EL appears in diodes with integrated Ge NPs near the direct band-gap transition of Ge at about 0.82 eV with an intensity strongly correlating with current density. However, it has also been found that Ge NPs integrated into a-SiC:H significantly deteriorates diode I–V characteristic

Effect of plasma composition on nanocrystalline diamond layers deposited by a microwave linear antenna plasma-enhanced chemical vapour deposition system

International audienceThe addition of CO2 into the process gas has a significant impact on the quality and the incorporation of boron in CVD diamond layers. In this report we study the effect of CO2 addition in the gas phase on the properties of boron doped nano‐crystalline diamond (BNCD) layers grown at low substrate temperatures (450–500 °C) using a microwave linear antenna plasma‐enhanced chemical vapour deposition apparatus (MW‐LA‐PECVD). Experimental results show an increase in the layers' conductivity with a reduction in CO2 concentration, which is consistent with the variation in the atomic boron emission line intensity measured by optical emission spectroscopy (OES). At CO2 concentrations close to zero, we observed the formation of a smooth, transparent and highly resistive layer on unseeded substrates. This layer has been identified as silicon carbide (SiC) by transmission electron microscopy and X‐ray photoelectron microscopy. The presence of silicon in the plasma is confirmed by OES and it is attributed to quartz tube etching. In this specific deposition condition, diamond growth is in competition with SiC growth

Large area heavily boron doped nano-crystalline diamond growth by MW-LA-PECVD [Póster]

Diamond is a unique semiconductor with a wide bandgap which usually is easily doped with boron and is acknowledged as one of the best materials for electrochemical applications. Heavily boron doped, high quality single crystal synthetic diamond can reach electrical conductivity as high as 103 S.cm, whereas polycrystalline material usually reaches c.a. 102 S.cm. However, many potential applications are restricted by the deposition temperature and limited coating area of conventional MW PECVD systems. Deposition of boron doped nano-crystalline diamond (BNCD) layers using a microwave PECVD system with linear antenna delivery (MW-LA-PECVD), enabling large area coating, was first reported in 2014 [1]. However, layers showed lower electrical conductivity in comparison to BNCD layers deposited using conventional PECVD systems. In addition, deposition of BNCD by MW-LA-PECVD is complicated by the necessity for the addition of oxygen species, which are known to limit boron incorporation and the competitive growth of silicon carbide at low CO2 concentrations [2, 3]. In this work, we further study the effect of deposition conditions on the synthesis of BNCD using the MW-LA-PECVD technique. In order to produce highly conductive BNCD with a low sp2 fraction, we have investigated in greater detail the effect of deposition temperature, from 250 °C up to 750 °C, using temperature controlled substrate stages and the effect of precursor gas compositions

A detailed mechanism of degradation behaviour of biodegradable as-ECAPed Zn-0.8Mg-0.2Sr with emphasis on localized corrosion attack

In this study, advanced techniques such as atom probe tomography, atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy were used to determine the corrosion mechanism of the as-ECAPed Zn-0.8Mg-0.2Sr alloy. The influence of microstructural and surface features on the corrosion mechanism was investigated. Despite its significance, the surface composition before exposure is often neglected by the scientific community. The analyses revealed the formation of thin ZnO, MgO, and MgCO3 layers on the surface of the material before exposure. These layers participated in the formation of corrosion products, leading to the predominant occurrence of hydrozincite. In addition, the layers possessed different resistance to the environment, resulting in localized corrosion attacks. The segregation of Mg on the Zn grain boundaries with lower potential compared with the Zn-matrix was revealed by atom probe tomography and atomic force microscopy. The degradation process was initiated by the activity of micro-galvanic cells, specifically Zn – Mg2Zn11/SrZn13. This process led to the activity of the crevice corrosion mechanism and subsequent attack to a depth of 250 μm. The corrosion rate of the alloy determined by the weight loss method was 0.36 mm·a−1. Based on this detailed study, the degradation mechanism of the Zn-0.8Mg-0.2Sr alloy is proposed

Heavily boron doped nano-crystalline diamond growth by MW-LA-PECVD [Póster]

Diamond is a unique semiconductor with a wide bandgap which is easily doped with boron and is acknowledged as one of the best materials for electrochemical applications. Heavily boron doped, high quality single crystal synthetic diamond can reach electrical conductivity of c.a. 103 S.cm, whereas polycrystalline material can reach c.a. 102 S.cm. However, many potential applications are restricted by the deposition temperature and limited coating area of conventional MW PECVD systems. Deposition of boron doped nano-crystalline diamond (BNCD) layers using a microwave PECVD system with linear antenna delivery (MW-LA-PECVD), enabling large area coating, was first reported in 2014. However, layers showed lower electrical conductivity in comparison to layers deposited using conventional PECVD systems. In addition, deposition of BNCD by MW-LA-PECVD is complicated by the necessity for the addition of oxygen species, which are known to limit boron incorporation and the competitive growth of silicon carbide at low CO2 concentrations. In this work, we further investigate the effect of deposition conditions on the synthesis of BNCD using the MW-LA-PECVD technique. In order to produce highly conductive BNCD, we have investigated the effect of CO2 concentration, boron to oxygen ratio and boron to carbon ratio (to well above standard values). The effect of deposition temperature was also studied (from 250 °C up to 750 °C) using temperature controlled substrate stages

Optical Contrast and Raman Spectroscopy Techniques Applied to Few-Layer 2D Hexagonal Boron Nitride

The successful integration of few-layer thick hexagonal boron nitride (hBN) into devices based on two-dimensional materials requires fast and non-destructive techniques to quantify their thickness. Optical contrast methods and Raman spectroscopy have been widely used to estimate the thickness of two-dimensional semiconductors and semi-metals. However, they have so far not been applied to two-dimensional insulators. In this work, we demonstrate the ability of optical contrast techniques to estimate the thickness of few-layer hBN on SiO2/Si substrates, which was also measured by atomic force microscopy. Optical contrast of hBN on SiO2/Si substrates exhibits a linear trend with the number of hBN monolayers in the few-layer thickness range. We also used bandpass filters (500–650 nm) to improve the effectiveness of the optical contrast methods for thickness estimations. We also investigated the thickness dependence of the high frequency in-plane E2g phonon mode of atomically thin hBN on SiO2/Si substrates by micro-Raman spectroscopy, which exhibits a weak thickness-dependence attributable to the in-plane vibration character of this mode. Ab initio calculations of the Raman active phonon modes of atomically thin free-standing crystals support these results, even if the substrate can reduce the frequency shift of the E2g phonon mode by reducing the hBN thickness. Therefore, the optical contrast method arises as the most suitable and fast technique to estimate the thickness of hBN nanosheets

Nanocrystalline Boron-Doped Diamond as a Corrosion-Resistant Anode for Water Oxidation via Si Photoelectrodes

Due to its high sensitivity to corrosion, the use of Si in direct photoelectrochemical (PEC) water-splitting systems that convert solar energy into chemical fuels has been greatly limited. Therefore, the development of low-cost materials resistant to corrosion under oxidizing conditions is an important goal toward a suitable protection of otherwise unstable semiconductors used in PEC cells. Here, we report on the development of a protective coating based on thin and electrically conductive nanocrystalline boron-doped diamond (BDD) layers. We found that BDD layers protect the underlying Si photoelectrodes over a wide pH range (1-14) in aqueous electrolyte solutions. A BDD layer maintains an efficient charge carrier transfer from the underlying silicon to the electrolyte solution. SiIBDD photo electrodes show no sign of performance degradation after a continuous PEC treatment in neutral, acidic, and basic electrolytes. The deposition of a cobalt phosphate (CoPi) oxygen evolution catalyst onto the BDD layer significantly reduces the overpotential for water oxidation, demonstrating the ability of BDD layers to substitute the transparent conductive oxide coatings, such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO), frequently used as protective layers in Si photoelectrodes