Titel Deelnemers "Korte inhoud" "Early Periods of Low-Temperature Linear Antenna CVD Nucleation and Growth Study of Nanocrystalline Diamond Films" "Awadesh MALLIK, Wen-Ching Shih, Paulius POBEDINSKAS, Ken HAENEN" "Low-temperature growth of diamond films using the chemical vapor deposition (CVD) method is not so widely reported and its initial periods of nucleation and growth phenomenon are of particular interest to the researchers. Four sets of substrates were selected for growing diamond films using linear antenna microwave plasma-enhanced CVD (LA-MPCVD). Among them, silicon and sapphire substrates were pre-treated with detonation nanodiamond (DND) seeds before diamond growth, for enhancement of its nucleation. Carbon nanotube (CNT) films on Si substrates were also used as another template for LA-MPCVD diamond growth. To enhance diamond nucleation during CVD growth, some of the CNT films were again pre-treated by the electrophoretic deposition (EPD) of diamond nanoparticles. All these substrates were then put inside the LA-MPCVD chamber to grow diamond films under variable processing conditions. Microwave input powers (1100-2800 W), input power modes (pulse or continuous), antenna-to-stage distances (5-6.5 cm), process gas recipes (with or without CO2), methane gas percentages (3%-5%), and deposition times (11-120 min) were altered to investigate their effect on the growth of diamond film on the pre-treated substrates. The substrate temperatures were found to vary from as low as 170 degrees C to a maximum of 307 degrees C during the alteration of the different processing parameters. Contrary to the conventional MPCVD, it was observed that during the first hour of LA-MPCVD diamond growth, DND seeds and the nucleating structures do not coalesce together to make a continuous film. Deposition time was the most critical factor in fully covering the substrate surfaces with diamond film, since the substrate temperature could not become stable during the first hour of LA-MPCVD. CNTs were found to be oxidized rapidly under LA-MPCVD plasma conditions; therefore, a CO2-free process gas recipe was used to reduce CNT burning. Moreover, EPD-coated CNTs were found to be less oxidized by the LACVD plasma during diamond growth." "A special issue preface: diamond for quantum applications" "Shannon NICLEY, Gavin W. Morley, Ken HAENEN" "This special issue discusses current progress in the utilization of defect centres in diamond as spin-photon interfaces for quantum applications. This issue is based on the discussions of the Theo Murphy meeting 'Diamond for quantum applications' which covered the recent progress of diamond growth and engineering for the creation and optimization of colour centres, toward the integration of diamond-based qubits in quantum systems.This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'." "First-principles investigation of hydrogen-related reactions on (100)–(2 × 1):H diamond surfaces" "Emerick GUILLAUME, Danny VANPOUCKE, Rozita ROUZBAHANI BAYATANI, Luna Pratali Maffei, Matteo Pelucchi, Yoann Olivier, Luc Henrard, Ken HAENEN" "Hydrogen radical attacks and subsequent hydrogen migrations are considered to play an important role in the atomic-scale mechanisms of diamond chemical vapour deposition growth. We perform a comprehensive analysis of the reactions involving H-radical and vacancies on H-passivated diamond surfaces exposed to hydrogen radical-rich atmosphere. By means of first principles calculations—density functional theory and climbing image nudged elastic band method—transition states related to these mechanisms are identified and characterised. In addition, accurate reaction rates are computed using variational transition state theory. Together, these methods provide—for a broad range of temperatures and hydrogen radical concentrations—a picture of the relative likelihood of the migration or radical attack processes, along with a statistical description of the hydrogen coverage fraction of the (100) H-passivated surface, refining earlier results via a more thorough analysis of the processes at stake. Additionally, the migration of H-vacancy is shown to be anisotropic, and occurring preferentially across the dimer rows of the reconstructed surface. The approach used in this work can be generalised to other crystallographic orientations of diamond surfaces or other semiconductors." "Photoluminescence of Germanium-Vacancy Centers in Nanocrystalline Diamond Films: Implications for Quantum Sensing Applications" "Rani MARY JOY, Johannes Goerlitz, Paulius POBEDINSKAS, Dennis Herrmann, Tanmoy CHAKRABORTY, Emilie BOURGEOIS, Celine Noel, Julia Heupel, Daen Jannis, Nicolas Gauquelin, Cyril Popov, Laurent Houssiau, Christoph Becher, Jan D'HAEN, Johan VERBEECK, Milos NESLADEK, Ken HAENEN" "Point defects in diamond, promising candidates for nanoscale pressure-and temperature-sensing applications, are potentially scalable in polycrystalline diamond fabricated using the microwave plasma-enhanced chemical vapor deposition (MW PE CVD) technique. However, this approach introduces residual stress in the diamond films, leading to variations in the characteristic zero phonon line (ZPL) of the point defect in diamond. Here, we report the effect of residual stress on germanium-vacancy (GeV) centers in MW PE CVD nanocrystal-line diamond (NCD) films fabricated using single crystal Ge as the substrate and solid dopant source. GeV ensemble formation indicated by the zero phonon line (ZPL) at ∼602 nm is confirmed by room temperature (RT) photoluminescence (PL) measurements. PL mapping results show spatial nonuniformity in GeV formation along with other defects, including silicon-vacancy centers in the diamond films. The residual stress in NCD results in shifts in the PL peak positions. By estimating a stress shift coefficient of (2.9 ± 0.9) nm/GPa, the GeV PL peak position in the NCD film is determined to be between 598.7 and 603.2 nm. A larger ground state splitting due to the strain on a GeV-incorporated NCD pillar at a low temperature (10 K) is also reported. We also report the observation of intense ZPLs at RT that in some cases could be related to low Ge concentration and the surrounding crystalline environment. In addition, we also observe thicker microcrystalline diamond (MCD) films delaminate from the Ge substrate due to film residual stress and graphitic phase at the diamond/Ge substrate interface (confirmed by electron energy loss spectroscopy). Using this approach, a free-standing color center incorporated MCD film with dimensions up to 1 × 1 cm 2 is fabricated. Qualitative analysis using time-of-flight secondary ion mass spectroscopy reveals the presence of impurities, including Ge and silicon, in the MCD film. Our experimental results will provide insights into the scalability of GeV fabrication using the MW PE CVD technique and effectively implement NCD-based nanoscale-sensing applications." "Functionalization of Carbon Surfaces Using the Copper-Catalyzed Diels-Alder Reaction" "Denis Ari, Jean-Francois Bergamini, Teresa Rodrigues, Wolfgang Knoll, Charles Cougnon, Essraa AHMED, Paulius POBEDINSKAS, Ken HAENEN, Nicolas Nuns, Rabah Boukherroub, Sabine Szunerits, Yann R. Leroux" "We propose here a new method to functionalize carbonmaterials via a catalyzed Diels-Alder reaction.In a Diels-Alderreaction, carbon materials can be used as a diene or a dienophile.Here, carbon materials are used as dienes and alkyne-terminated derivativesas dienophiles. Different carbon materials, i.e., glassy carbon, carbonpowder (carbon black), pyrolytic graphite carbon materials, and graphene,were functionalized by alkyne ferrocene derivatives or perfluoro-taggedalkyne molecules and characterized by electrochemical means, atomicforce microscopy, and X-ray photoelectron spectroscopy experiments.This method allows for the rapid functionalization of carbon materialsin mild conditions with high surface coverage." "Standardizing OER Electrocatalyst Benchmarking in Aqueous Electrolytes: Comprehensive Guidelines for Accelerated Stress Tests and Backing Electrodes" "M Zlatar, D Escalera-López, MG Rodríguez, T Hrbek, C Götz, Rani MARY JOY, A Savan, HP Tran, HN Nong, Paulius POBEDINSKAS, V Briega-Martos, A Hutzler, T Böhm, Ken HAENEN, A Ludwig, I Khalakhan, P Strasser, S Cherevko" "The scarcity of iridium, needed to catalyze the sluggish oxygen evolution reaction (OER), hinders large-scale hydrogen production with proton exchange membrane water electrolyzers (PEMWEs). Crucial steps require reducing its loading while improving its overall activity and stability. Despite knowledge transfer challenges, cost and time constraints still favor aqueous model systems (AMSs) over real devices for the OER electrocatalyst testing. During AMS testing, benchmarking strategies such as accelerated stress tests (ASTs) aim at improving catalyst lifetime estimation compared to constant current loads. This study systematically evaluates a commercial Ir catalyst by modifying both AST parameters and the employed backing electrodes to examine their impact on activity−stability relationships. A comprehensive set of spectroscopy and microscopy techniques, including in situ inductively coupled plasma mass spectrometry, is employed to monitor Ir and backing electrode modifications. Our findings demonstrate that the choice of both lower potential limit (LPL) in ASTs and backing electrode significantly influences the estimation of Ir-based electrocatalysts' activity and stability. Unique degradation mechanisms, such as passivation, redeposition on active sites, and contribution to the OER, were observed for different backing electrodes at varying LPLs. These results emphasize the importance of optimizing parameters and electrode selection in ASTs to accurately assess the electrocatalyst performance. Furthermore, they establish the foundation for developing relevant standardized test protocols, enabling the cost-effective development of high-performance catalysts for PEMWE applications." "Inkjet Printing-Manufactured Boron-Doped Diamond Chip Electrodes for Electrochemical Sensing Purposes" "Zhichao Liu, Simona Baluchova, Bob Brocken, Essraa AHMED, Josephus G. Buijnsters, Paulius POBEDINSKAS, Ken HAENEN" "Fabrication of patternedboron-doped diamond (BDD) inan inexpensiveand straightforward way is required for a variety of practical applications,including the development of BDD-based electrochemical sensors. Thiswork describes a simplified and novel bottom-up fabrication approachfor BDD-based three-electrode sensor chips utilizing direct inkjetprinting of diamond nanoparticles on silicon-based substrates. Thewhole seeding process, accomplished by a commercial research inkjetprinter with piezo-driven drop-on-demand printheads, was systematicallyexamined. Optimized and continuous inkjet-printed features were obtainedwith glycerol-based diamond ink (0.4% vol/wt), silicon substratespretreated by exposure to oxygen plasma and subsequently to air, andapplying a dot density of 750 drops (volume 9 pL) per inch. Next,the dried micropatterned substrate was subjected to a chemical vapordeposition step to grow uniform thin-film BDD, which satisfied thefunction of both working and counter electrodes. Silver was inkjet-printedto complete the sensor chip with a reference electrode. Scanning electronmicrographs showed a closed BDD layer with a typical polycrystallinestructure and sharp and well-defined edges. Very good homogeneityin diamond layer composition and a high boron content (& SIM;2 x10(21) atoms cm(-3)) was confirmed by Ramanspectroscopy. Important electrochemical characteristics, includingthe width of the potential window (2.5 V) and double-layer capacitance(27 & mu;F cm(-2)), were evaluated by cyclic voltammetry.Fast electron transfer kinetics was recognized for the [Ru(NH3)(6)](3+/2+) redox marker due to the highdoping level, while somewhat hindered kinetics was observed for thesurface-sensitive [Fe(CN)(6)](3-/4-) probe. Furthermore, the ability to electrochemically detect organiccompounds of different structural motifs, such as glucose, ascorbicacid, uric acid, tyrosine, and dopamine, was successfully verifiedand compared with commercially available screen-printed BDD electrodes.The newly developed chip-based manufacture method enables the rapidprototyping of different small-scale electrode designs and BDD microstructures,which can lead to enhanced sensor performance with capability of repeateduse." "The Influence of UV–Ozone, O2 Plasma, and CF4 Plasma Treatment on the Droplet-Based Deposition of Diamond Nanoparticles" "Pieter VERDING, Rani MARY JOY, Dieter REENAERS, Rachith SHANIVARASANTHE NITHYANANDA KUMAR, Rozita ROUZBAHANI BAYATANI, Ewoud Jeunen, Seppe Thomas, Derese DESTA, Hans-Gerd BOYEN, Paulius POBEDINSKAS, Ken HAENEN, Wim DEFERME" "Surface treatment is critical for homogeneous coating over a large area and high-resolution patterning of nanodiamond (ND) particles. To optimize the interaction between the surface of a substrate and the colloid of ND particles, it is essential to remove hydrocarbon contamination by surface treatment and to increase the surface energy of the substrate, hence improving the diamond film homogeneity upon its deposition. However, the impact of substrate surface treatment on the properties of coatings and patterns is not fully understood. This study explores the impact of UV−ozone, O 2 plasma, and CF 4 plasma treatments on the wetting properties of the fused silica glass substrate surface. We identify the optimal time interval between the treatment and subsequent ND coating/patterning processes, which were conducted using inkjet printing and ultrasonic spray coating techniques. Our results showed that UV−ozone and O 2 plasma resulted in hydrophilic surfaces, while CF 4 plasma treatment resulted in hydrophobic surfaces. We demonstrate the use of CF 4 plasma treatment before inkjet printing to generate high-resolution patterns with dots as small as 30 μm in diameter. Ultrasonic spray coating showed homogeneous coatings after using UV−ozone and O 2 plasma treatment. The findings of this study provide valuable insights into the hydrocarbon airborne contamination on cleaned surfaces over time even in clean-room environments and have a notable impact on the performance of liquid coatings and patterns. We highlight the importance of timing between the surface treatment and printing in achieving high resolution or homogeneity." "Deposition and Characterisation of a Diamond/Ti/Diamond Multilayer Structure" "Awadesh MALLIK, Fernando LLORET, Marina Gutierrez, Rozita ROUZBAHANI BAYATANI, Paulius POBEDINSKAS, Wen-Ching Shih, Ken HAENEN" "In this work, a diamond/Ti/diamond multilayer structure has been fabricated by successively following thin-film CVD and PVD routes. It has been found that a combined pre-treatment of the silicon base substrate, via argon plasma etching for creating surface roughness and, thereafter, detonation nanodiamond (DND) seeding, helps in the nucleation and growth of well-adherent CVD diamond films with a well-defined Raman signal at 1332 cm-1, showing the crystalline nature of the film. Ti sputtering on such a CVD-grown diamond surface leads to an imprinted bead-like microstructure of the titanium film, generated from the underlying diamond layer. The cross-sectional thickness of the titanium layer can be found to vary by as much as 0.5 mu m across the length of the surface, which was caused by a subsequent hydrogen plasma etching process step of the composite film conducted after Ti sputtering. The hydrogen plasma etching of the Ti-diamond composite film was found to be essential for smoothening the uneven as-grown texture of the films, which was developed due to the unequal growth of the microcrystalline diamond columns. Such hydrogen plasma surface treatment helped further the nucleation and growth of a nanocrystalline diamond film as the top layer, which was deposited following a similar CVD route to that used in depositing the bottom diamond layer, albeit with different process parameters. For the latter, a hydrogen gas diluted with PH3 precursor recipe produced smaller nanocrystalline diamond crystals for the top layer. The titanium layer in between the two diamond layers possesses a very-fine-grained microstructure. Transmission electron microscopy (TEM) results show evidence of intermixing between the titanium and diamond layers at their respective interfaces. The thin films in the composite multilayer follow the contour of the plasma-etched silicon substrate and are thus useful in producing continuous protective coatings on 3D objects-a requirement for many engineering applications." "Lithium nitrate mediated dynamic formation of solid electrolyte interphase revealed by in situ Fourier transform infrared spectroscopy" "Longsheng Wu, Jingping Hu, Sijing Chen, Xiaorong Yang, Lu Liu, John S. Foord, Paulius POBEDINSKAS, Ken HAENEN, Huijie Hou, Jiakuan Yang" "A stable solid electrolyte interphase (SEI) plays a vital role in the cyclic stability and Coulombic efficiency (CE) of high-performance lithium-sulfur (Li-S) batteries. It is recognized that the LiNO3 additive can stabilize the SEI of the lithium electrode. However, the exact mechanism of the LiNO3 additive on the SEI of the lithium electrode remains unclear. In this work, we first revealed the mediation mechanism of LiNO3 additive on the dynamic evolution of the SEI on a lithium anode surface through in situ Fourier transform infrared (FTIR) spectroscopy and ab initio molecular dynamics (AIMD) methods. The FTIR and AIMD results directly proved that LiNO3 can accelerate the reduction of lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) into small molecules rich in Li2O on lithium anode, thus forming a compact and stable SEI after immersing in the LiNO3-containing electrolyte. Moreover, the decomposition of LiTFSI and the solvent is hindered in the subsequent lithium deposition stripping process due to the stable SEI, thus leading to higher Coulombic efficiency and long-term cyclic stability. In addition, an ROSO2Li-like intermediate is also observed during the lithium deposition process while decomposing or diffusing away during the lithium stripping process, maintaining a dynamic formation/dissolution equilibrium of the SEI. This research provides a new insight into understanding the role of LiNO3 in stabilizing lithium electrode."