Publications

2023

• Reactive plasma sputtering deposition of polycrystalline GaN thin films on silicon substrates at room temperature
  
  • Srinivasan Lakshman
  • Jadaud Cyril
  • Silva François
  • Vanel Jean-Charles
  • Maurice Jean-Luc
  • Johnson Erik
  • Roca i Cabarrocas Pere
  • Ouaras Karim
  Journal of Vacuum Science & Technology A, American Vacuum Society, 2023, 41 (5). We report on the successful growth of polycrystalline GaN thin films on Si (100) substrates at room temperature (without intentional heating) using radiofrequency reactive magnetron sputtering. We use Ar and N2 as the main sputtering and N-atom precursor gas sources, respectively, and a gallium cathode as the Ga-atom source. We focus here on studying the effect of working pressure, as it is found to be the parameter that plays the most influential role on the crystalline quality of the thin films in the investigated range (20–95 mTorr). The morphology, microstructure, and composition profile of the GaN thin films are analyzed using a set of ex situ solid-state characterization techniques. This study reveals that for process pressures below 50 mTorr, the resulting films possess an amorphous nature, while for process pressures above that they become polycrystalline. Most of the crystalline films are found to be nanostructured with grain sizes typically ranging from 10 to 30 nm in size. The highest growth rate of ∼ 2.9 Å/s is obtained for the deposition carried out at 50 mTorr. At this pressure, the films exhibit the best crystallinity with a dominant wurtzite hexagonal structure. The elemental distribution of Ga and N throughout the growth profile is uniform with a sharp interface at the substrate, demonstrating one of the interests in working at low temperatures to avoid melt-back etching, a destructive reaction between gallium and silicon, that usually takes place at high temperatures. (10.1116/6.0002718)
  DOI : 10.1116/6.0002718
• Three-Terminal Monolithic Perovskite/Silicon Tandem Solar Cell Exceeding 29% Power Conversion Efficiency
  
  • Dai Letian
  • Li Shangjing
  • Hu Yong
  • Huang Junyi
  • Liu Zhirong
  • Shi Haodan
  • Guan Gaofei
  • Shen Yan
  • Hu Bin
  • I Cabarrocas Pere Roca
  • Wang Mingkui
  ACS Energy Letters, American Chemical Society, 2023, 8 (9), pp.3839-3842. (10.1021/acsenergylett.3c01347)
  DOI : 10.1021/acsenergylett.3c01347
• Synthesis of Few-Layered Transition-Metal Dichalcogenides by Ion Implantation of Chalcogen and Metal Species into Sapphire
  
  • Bude Romain
  • Verschueren Ivan
  • Florea Ileana
  • Maurice Jean-Luc
  • Legagneux Pierre
  • Pereira Lino
  • Bana Harsh
  • Villarreal Renan
  • Blume Raoul
  • Knop-Gericke Axel
  • Jones Travis
  • Pribat Didier
  ACS Omega, ACS Publications, 2023, 8 (32), pp.29475-29484. (10.1021/acsomega.3c03179)
  DOI : 10.1021/acsomega.3c03179
• Maskless patterned plasma fabrication of interdigitated back contact silicon heterojunction solar cells: Characterization and optimization
  
  • Wang Junkang
  • Ghosh Monalisa
  • Ouaras Karim
  • Daineka Dmitri
  • Bulkin Pavel
  • Roca i Cabarrocas Pere
  • Filonovich Sergej
  • Alvarez José
  • Johnson Erik
  Solar Energy Materials and Solar Cells, Elsevier, 2023, 258, pp.112417. We demonstrate a novel method to fabricate passivated interdigitated back contact (IBC) crystalline silicon solar cells incorporating a maskless, patterned plasma etching step. After deposition in a plasma-enhanced chemical vapor deposition (PECVD) chamber, the intrinsic and doped hydrogenated amorphous silicon and microcrystalline silicon layers (necessary for the passivated interdigitated contacts in such heterojunction technology (HJT) devices) are patterned via a single, maskless etching step, also performed in a PECVD chamber. The patterning step relies on selectively lighting an etching plasma within slits in the patterned powered electrode when it is placed very close to the substrate. The process flow is characterized and optimized at each step using spectroscopic ellipsometry, photoluminescence, and surface photovoltage mapping. It is shown that a critical step is the removal of a damaged layer formed on the surface after the patterned etching. Without this step, the IBC-HJT solar cells systematically exhibit S-shaped curves in their current-voltage (I–V) characteristics (giving fill factors below 25%). Once this critical step is included, the solar cells display I–V curves with fill factors above 65%, demonstrating the advantage of the maskless plasma patterning process. (10.1016/j.solmat.2023.112417)
  DOI : 10.1016/j.solmat.2023.112417
• π-Conjugated Polymer Nanoparticles from Design, Synthesis to Biomedical Applications: Sensing, Imaging, and Therapy
  
  • Elgiddawy Nada
  • Elnagar Noha
  • Korri-Youssoufi Hafsa
  • Yassar Abderrahim
  Microorganisms, MDPI, 2023, 11 (8), pp.2006. In the past decade, π-conjugated polymer nanoparticles (CPNs) have been considered as promising nanomaterials for biomedical applications, and are widely used as probe materials for bioimaging and drug delivery. Due to their distinctive photophysical and physicochemical characteristics, good compatibility, and ease of functionalization, CPNs are gaining popularity and being used in more and more cuaing-edge biomedical sectors. Common synthetic techniques can be used to synthesize CPNs with adjustable particle size and dispersion. More importantly, the recent development of CPNs for sensing and imaging applications has rendered them as a promising device for use in healthcare. This review provides a synopsis of the preparation and functionalization of CPNs and summarizes the recent advancements of CPNs for biomedical applications. In particular, we discuss their major role in bioimaging, therapeutics, fluorescence, and electrochemical sensing. As a conclusion, we highlight the challenges and future perspectives of biomedical applications of CPNs. (10.3390/microorganisms11082006)
  DOI : 10.3390/microorganisms11082006
• Investigating the Effect of Cross-Conjugation Patterns on the Optoelectronic Properties of 7,7′Isoindigo-Based Materials
  
  • Ren Shiwei
  • Habibi Amirhossein
  • Wang Yujie
  • Yassar Abderrahim
  Electronics, MDPI, 2023, 12 (15), pp.3313. Isoindigo (IID) is widely used as a building block for the fabrication of organic semiconductor devices. Understanding the impact of cross-conjugation and linear conjugation on the optoelectronic properties of disubstituted IID is of great importance for the design of improved materials. In this study, phenyl and thienyl groups were substituted at the cross-conjugated 7,7′ position of IID to generate three novel organic semiconductor structures with a donor–acceptor architecture. The optoelectronic properties of this IID derivative were investigated and compared with those of the 6,6′ linearly conjugated IID analogs using UV–Vis spectroscopy and cyclic voltammetry. The experimental results were compared using density functional theory calculations to provide structure–property relationships based on substitution types and attachment sites for IID. The frontier orbital energy levels of the material did not vary dramatically with the position of the substituent, while the type of substituent showed a more significant influence on the HOMO’s energy level and oscillator strength. Phenyl-disubstituted 7,7′ IID (7Ph7′Ph) and thienyl-disubstituted 7,7′ IID (7Th7′Th) materials were used as electron transport layers in perovskite solar cells with a power conversion efficiency of 5.70% and 6.07%, respectively. These observations enhance our understanding of the electronic structure and optoelectronic properties of IID, guiding the design of the next generation of IID-based semiconductors. (10.3390/electronics12153313)
  DOI : 10.3390/electronics12153313
• Synergistic Use of All-Acceptor Strategies for the Preparation of an Organic Semiconductor and the Realization of High Electron Transport Properties in Organic Field-Effect Transistors
  
  • Ren Shiwei
  • Zhang Wenqing
  • Wang Zhuoer
  • Yassar Abderrahim
  • Liao Zhiting
  • Yi Zhengran
  Polymers, MDPI, 2023, 15 (16), pp.3392. The development of n-type organic semiconductor materials for transporting electrons as part of logic circuits is equally important to the development of p-type materials for transporting holes. Currently, progress in research on n-type materials is relatively backward, and the number of polymers with high electron mobility is limited. As the core component of the organic field-effect transistor (OFET), the rational design and judicious selection of the structure of organic semiconductor materials are crucial to enhance the performance of devices. A novel conjugated copolymer with an all-acceptor structure was synthesized based on an effective chemical structure modification and design strategy. PDPPTT-2Tz was obtained by the Stille coupling of the DPPTT monomer with 2Tz-SnMe3, which features high molecular weight and thermal stability. The low-lying lowest unoccupied molecular orbital (LUMO) energy level of the copolymer was attributed to the introduction of electron-deficient bithiazole. DFT calculations revealed that this material is highly planar. The effect of modulation from a donor–acceptor to acceptor–acceptor structure on the improvement of electron mobility was significant, which showed a maximum value of 1.29 cm2 V−1 s−1 and an average value of 0.81 cm2 V−1 s−1 for electron mobility in BGBC-based OFET devices. Our results demonstrate that DPP-based polymers can be used not only as excellent p-type materials but also as promising n-type materials. (10.3390/polym15163392)
  DOI : 10.3390/polym15163392
• Machine Learning in Tissue Polarimetry
  
  • Makkithaya Kausalya Neelavara
  • Melanthota Sindhoora Kaniyala
  • Kistenev Yury
  • Bykov Alexander
  • Novikova Tatiana
  • Meglinski Igor
  • Mazumder Nirmal
  , 2023, pp.425-450. (10.1007/978-3-031-31852-8_14)
  DOI : 10.1007/978-3-031-31852-8_14
• Increasing signal-to-noise ratio in over-determined Mueller matrices
  
  • Philpott H.
  • Garcia-Caurel E.
  • Guaitella O.
  • Sobota A.
  Optics Express, Optical Society of America - OSA Publishing, 2023, 31 (16), pp.25585. This work investigates how the signal-to-noise ratio (SNR) of an over-determined Mueller matrix can be improved by changing the method of calculation. Specifically, our investigation focused on comparing SNRs achieved using the vector methodology from the field of partial Mueller polarimetry, and the matrix methodology. We use experimentally derived measurements from an investigation into the time-varying signal produced by the Mueller matrix of an electro-optic Bismuth Silicon Oxide (BSO) crystal undergoing cyclical impact of a Helium plasma ionisation wave. Our findings show that the vector methodology is superior to the matrix methodology, with a maximum SNR of 7.54 versus 4.97. We put forth that the superiority of the vector methodology is due to its greater flexibility, which results in the Mueller matrix being calculated with better condition matrices, and higher levels of SNR in the intensity measurements used for calculation. (10.1364/OE.493464)
  DOI : 10.1364/OE.493464
• Evolution of Cu-In Catalyst Nanoparticles under Hydrogen Plasma Treatment and Silicon Nanowire Growth Conditions
  
  • Wang Weixi
  • Ngo Éric
  • Bulkin Pavel
  • Zhang Zhengyu
  • Foldyna Martin
  • Roca I Cabarrocas Pere
  • Johnson Erik V
  • Maurice Jean-Luc
  Nanomaterials, MDPI, 2023, 13 (14), pp.2061. We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 • C and the SiNW growth itself in a hydrogen-silane plasma at 420 • C. We show that the H 2-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 • C induces a phase transformation of the catalyst cores to Cu 7 In 3 ; while a hydrogen plasma treatment at 420 • C without silane can lead to the formation of the Cu 11 In 9 phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid-solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs-below 10 nm-among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap. (10.3390/nano13142061)
  DOI : 10.3390/nano13142061
• Evolution of Cu-In Catalyst Nanoparticles under Hydrogen Plasma Treatment and Silicon Nanowire Growth Conditions
  
  • Wang Weixi
  • Ngo Éric
  • Bulkin Pavel
  • Zhang Zhengyu
  • Foldyna Martin
  • Roca i Cabarrocas Pere
  • Johnson Erik
  • Maurice Jean-Luc
  Nanomaterials, MDPI, 2023, 13 (14), pp.2061. We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 °C and the SiNW growth itself in a hydrogen-silane plasma at 420 °C. We show that the H2-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 °C induces a phase transformation of the catalyst cores to Cu7In3; while a hydrogen plasma treatment at 420 °C without silane can lead to the formation of the Cu11In9 phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid–solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs—below 10 nm—among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap. (10.3390/nano13142061)
  DOI : 10.3390/nano13142061
• In-Situ Direct Observation of Carbon Nanotube Synthesis Under Electric Field and Their Field Emission Performance
  
  • Vincent Pascal
  • Panciera Federico
  • Florea Ileana
  • Cojocaru Costel
  • Perisanu Sorin
  • Ayari Anthony
  • Chaste Julien
  • Legagneux Pierre
  • Purcell Stephen
  , 2023, pp.120-121. (10.1109/IVNC57695.2023.10188980)
  DOI : 10.1109/IVNC57695.2023.10188980
• Extraction of ECG features with spiking neurons for decreased power consumption in embedded devices
  
  • Li Zonglong
  • Calvet Laurie E
  , 2023. In recent years, the computational efficiency of spike-based biomimetic information processing has received increasing interest. Here we show by simulation how two spiking neurons with different thresholds can be used to extract ECG features. One high-threshold neuron detects the location of the heartbeat, and the other low-threshold neuron detects other small-magnitude features. These detected features alone can then be transmitted to a nearby computer to classify the heartbeat instead of the entire ECG signal. Reducing transferred data by about 50 times, minimizing energy consumption and thus potentially extending the continuous use time for health monitoring applications. We show that a KNN algorithm classifies the heartbeat based on the obtained features with an overall accuracy of 96%, proving our method’s feasibility. (10.1109/SMACD58065.2023.10192147)
  DOI : 10.1109/SMACD58065.2023.10192147
• Online spike-based recognition of digits with ultrafast microlaser neurons
  
  • Masominia Amir
  • Calvet Laurie
  • Thorpe Simon
  • Barbay Sylvain
  Frontiers in Computational Neuroscience, Frontiers, 2023, 17, pp.1164472. Classification and recognition tasks performed on photonic hardware-based neural networks often require at least one offline computational step, such as in the increasingly popular reservoir computing paradigm. Removing this offline step can significantly improve the response time and energy efficiency of such systems. We present numerical simulations of different algorithms that utilize ultrafast photonic spiking neurons as receptive fields to allow for image recognition without an offline computing step. In particular, we discuss the merits of event, spike-time and rank-order based algorithms adapted to this system. These techniques have the potential to significantly improve the efficiency and effectiveness of optical classification systems, minimizing the number of spiking nodes required for a given task and leveraging the parallelism offered by photonic hardware. (10.3389/fncom.2023.1164472)
  DOI : 10.3389/fncom.2023.1164472
• On the use of soft X-ray STXM for organic-inorganic halide perovskite photovoltaic materials
  
  • Jun Haeyeon
  • Dindault Chloé
  • Tondelier Denis
  • Geffroy Bernard
  • Florea Ileana
  • Bouree Jean-Eric
  • Schulz Philip
  • Bonnassieux Yvan
  • Swaraj Sufal
  Journal of Electron Spectroscopy and Related Phenomena, Elsevier, 2023, 266, pp.147358. (10.1016/j.elspec.2023.147358)
  DOI : 10.1016/j.elspec.2023.147358
• Self-formation of SiGe oxide, Ge, and void multilayers via thermal oxidation of hydrogenated epitaxial SiGe films
  
  • An Junyang
  • Gong Ruiling
  • Li Xinyu
  • Florea Ileana
  • Watrin Lise
  • Roca i Cabarrocas Pere
  • Chen Wanghua
  Vacuum, Elsevier, 2023, 213, pp.112072. (10.1016/j.vacuum.2023.112072)
  DOI : 10.1016/j.vacuum.2023.112072
• Mueller Matrix Analysis, Decompositions, and Novel Quantitative Approaches to Processing Complex Polarimetric Data
  
  • Arteaga Oriol
  • Ossikovski Razvigor
  , 2023, 124 (17), pp.25-60. One of the most challenging goals of flooded chalk analyses used in Enhanced Oil Recovery (EOR) is to reach high-resolution mineralogical data, in order to detect the composition of new crystals grown after brine injections, with ≤1 μm grain size. Understanding how flooding affects chemical induced compaction, mechanical strength permeability, and porosity is paramount in EOR related investigations. Magnesite formation is the most pervasive process when MgCl2 is injected into chalk, and the submicrometric grain size of the new minerals requires a high performing imaging technique and a new methodological approach: in our study, we present the first attempt of applying Tip-Enhanced Raman Spectroscopy (TERS) to rock and mineral samples. It is a new frontier technique that couples Raman Spectroscopy with Atomic Force Microscopy, allowing impressively high-resolution topography and mineralogical maps. Two long term experiments have been analyzed, where chalk cores were flooded for 718 days and 1072 days, at reservoir conditions comparable to hydrocarbon reservoirs in chalk at the Norwegian continental shelf. Few microns squared areas have been imaged by Atomic Force Microscopy using ultra-polished thin sections. First analyses identified a less pervasive secondary growth of magnesite in the 718 days test and an almost pure magnesite composition in the 1072 days test. Transmission Electron Microscopy (TEM) has been employed to confirm the results of TERS and add dark and bright field grain imaging to the investigations. This confirms the need for high-resolution methodologies such as TERS and TEM to fully understand the EOR effects at submicron-scale. (10.1007/978-3-031-04741-1_2)
  DOI : 10.1007/978-3-031-04741-1_2
• Mueller Polarimetry of Brain Tissues
  
  • Novikova Tatiana
  • Pierangelo Angelo
  • Schucht Philippe
  • Meglinski Igor
  • Rodríguez-Núñez Omar
  • Lee Hee Ryung
  , 2023, pp.205-229. (10.1007/978-3-031-04741-1_8)
  DOI : 10.1007/978-3-031-04741-1_8
• Advanced Characterization and Degradation Analysis of Perovskite Solar Cells using Machine Learning and Bayesian Optimization
  
  • Chakar Joseph
  • Julien Arthur
  • Medjoubi Karim
  • Posada Jorge
  • Guillemoles Jean-François
  • Puel Jean Baptiste
  • Bonnassieux Yvan
  , 2023. Context & Scale • Poor stability is a major barrier to the commercialization of perovskite solar cells. • With so many factors to consider, it often takes years to understand performance bottlenecks and optimize the design process. • We combine physics modeling, machine learning, and experimentation to better understand the complex relationship between device performance and underlying properties. → Gain insights into performance and degradation → Reduce the need for time-consuming and laborious characterization techniques → Flexible & scalable approach
• Shear-aligned large-area organic semiconductor crystals through extended π- π interaction
  
  • Zhang Songyi
  • Talnack Felix
  • Jousselin-Oba Tanguy
  • Bhat Vinayak
  • Wu Yilei
  • Lei Yusheng
  • Tomo Yoko
  • Gong Huaxin
  • Michalek Lukas
  • Zhong Donglai
  • Wu Can
  • Yassar Abderrahim
  • Mannsfeld Stefan
  • Risko Chad
  • Frigoli Michel
  • Bao Zhenan
  Journal of Materials Chemistry C, Royal Society of Chemistry, 2023, 11 (26), pp.7717-7723. Small molecule-based organic semiconductors are of broadly interest in organic field-effect transistors (OFETs) due to their potential for high crystallinity and electrical performance. The 2D molecule, TIPS-peri-pentacenopentacene (TIPS-PPP), which is the vertical extension of the 1D TIPS-pentacene (TIPS-PEN) molecule, offers a lower bandgap, higher aromaticity, and an enhanced π-π interaction with neighboring molecules in the solid state when compared to TIPS-PEN. However, an in-depth understanding of the relationship between the molecule structure, solid-state molecular packing, and the electronic properties has not been reported due to poor control over the TIPS-PPP crystallite size. In this work, we successfully engineered highly oriented large-area TIPS-PPP crystals through the solution shear coating technique. Compared with narrow ribbon-like TIPS-PEN crystals, TIPS-PPP crystals can grow centimeters long and over 500 µm wide. TIPS-PPP molecules are less susceptible to forming metastable polymorphs than TIPS-PEN molecules upon fast evaporation. The crystal structure of TIPS-PPP is also thermally stable at 250 °C. Notably, the anisotropic charge carrier mobility of TIPS-PPP crystals is resolved through fabricating bottom-gate top-contact devices, with a hole mobility of 3.1 cm2V-1s-1 along the preferred packing direction. Further device optimization using top-gate bottom-contact devices improved the mobility up to 6.5 cm2V-1s-1, which is among the highest for pentacene-derivative-based organic semiconductors (10.1039/D3TC01311A)
  DOI : 10.1039/D3TC01311A
• Band Bending and Surface Composition Analysis by p-ARXPS and Their Impact on Minority Carrier Lifetime After Germanium Wet Etching
  
  • Chapotot A.
  • Chretien J.
  • Fesiienko O.
  • Pargon E.
  • Ilahi B.
  • Cho J.
  • Courtois G.
  • Dessein K.
  • Boucherif A.
  • Hamon G.
  • Darnon M.
  , 2023.
• In situ Transmission Electron Microscopy (TEM) study of the reduction of TiO2 to TinO2n-1 magnéli phase
  
  • Schmidt Léon
  • Sharna Sharmin
  • Florea Ileana
  • Sanchez Clément
  • Ersen Ovidiu
  , 2023.
• Liquid phase exfoliated MoS2 nanosheets for NO2 sensing
  
  • Yassar Abderrahim
  • Ni Pingping
  , 2023.
• Ultrahigh Incorporation of Tin in SiSn Nanowires Grown via In-Plane Solid-Liquid-Solid Mechanism
  
  • Azrak Edy
  • Xue Zhaoguo
  • Liu Shuai
  • Chen Wanghua
  • Castro Celia
  • Duguay Sébastien
  • Pareige Philippe
  • Yu Linwei
  • Roca i Cabarrocas Pere
  Applied Surface Science, Elsevier, 2023, 618, pp.156637. (10.1016/j.apsusc.2023.156637)
  DOI : 10.1016/j.apsusc.2023.156637
• Synthesis and characterization of solution-processed indophenine derivatives for function as a hole transport layer for perovskite solar cells
  
  • Ren Shiwei
  • Habibi Amirhossein
  • Ni Pingping
  • Nahdi Hindia
  • Bouanis Fatima Zahra
  • Bourcier Sophie
  • Clavier Gilles
  • Frigoli Michel
  • Yassar Abderrahim
  Dyes and Pigments, Elsevier, 2023, 213, pp.111136. (10.1016/j.dyepig.2023.111136)
  DOI : 10.1016/j.dyepig.2023.111136