bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) New Strategies to Produce Light Emitters with Si-based Nanostructures
Authors: Favre Luc , Bouabdellaoui Mohammed , Assaf Elie , Guelil Imene , David Thomas , Ronda Antoine , Abbarchi Marco , Abel Mathieu , Rowell Nelson L. , Lockwood David J. , Berbezier Isabelle 
Published: May 2020

Silicon-Germanium strain engineering has been used for more than two decades in silicon based devices and has contributed to the scaling down of a transistor’s size and to significant improvements in device performance. However, while conventional silicon-germanium based electronics has experienced rapid and steady growth, thanks to this continuous miniaturization of transistors, this trend cannot continue indefinitely. Industry has already moved to alternate methods such as FinFET devices, in which a thin silicon channel is placed vertically, and the FD-SOI (FD-SGOI) design consisting of a thin film Si(SiGe) channel placed horizontally. For nodes scaled down below 28 nm, low power operation will be inherently hindered by both the imperfect interface, non-uniformity of ultra-thin films and quantum confinement effects, which increase the effective bandgap. In these devices, despite the intense research activity on the strained SiGe ultra-thin body, which accounts for a large portion of such microelectronic devices (below the 45 nm node), we still fail to properly understand the mechanisms that limit hole and electron mobilities in SGOI layers. In addition, one of the main challenges for Si based devices remains the fabrication of efficient group-IV photon sources / photon detectors compatible with the microelectronic industry, which would usefully replace the integration of III-V heterostructures on Si. The major bottleneck is that group-IV semiconductor elements have indirect bandgaps, but with possibilities of being transformed to direct bandgaps using strain engineering strategies.
In this presentation, we will review the formation mechanism of Ge-rich layers on SOI by condensation at different temperatures. TEM cross-section and GPA analysis of the heterostructures will be presented. We will also report the physical and optical properties of these heterostructures. Special attention is devoted to the influence of the SiGe thickness reduction (up to few MLs), where quantum confinement is prominent in the optical properties of the layers. Raman and PL results will be presented to better explain such confinement behavior. We show that novel SGOI substrates could represent a key strategy for the fabrication of future photonic devices.
(Invited) Tuning the Optoelectronic Properties in Composite Systems for Sunlight Conversion
Authors: Vomiero Alberto 
Published: May 2020

The processes of light absorption, exciton generation, charge separation and collection are critical to a series of applications, in which Sun light is either directly converted into electric power, like in solar cells, or transformed into chemical energy, like in photoelectrochemical hydrogen generation. All these processes are regulated by the optoelectronic properties of complex systems, in which the electronic band structure can be finely tuned by proper adjustment of chemical composition, size and morphology of the single components. Key element for the control of the optoelectronic properties is the modulation of the final electronic band structure. We will illustrate different strategies to obtain the desired optical and electrical properties in different complexes.
One of the most interesting systems is composed of semiconducting nanocrystals exhibiting quantum confined effects (the so-called quantum dots, QDs), which act as light absorbing materials, and generate excitons as a consequence of photon absorption. [1] The QDs are typically coupled to a wide bandgap semiconductor (SnO2, ZnO, TiO2), which acts as electron transport material. In this case, the optoelectronic properties are determined by the dynamics of hole/electron dissociation and recombination, and the structure of the interface between the QD and the oxide semiconductor regulates such dynamics. Another option is to apply core-shell QDs, in which the relative band alignment between the core and the shell can be tuned by tailoring the interface between them. [2]
We will illustrate a series of examples, [3] in which exciton dynamics in composite systems influences the functionality of the final device, including solar cells, photoelectrochemical hydrogen production and luminescent solar concentrators.

Keywords: Composite systems; quantum dots; exciton dynamics; solar cells; photoelectrochemical hydrogen generation; luminescent solar concentrators

References:

[1] Y. Zhou et al. Adv. En. Mater. 1501913 (2016): 6.
[2] G. Sirigu et al. Phys. Rev. B 155303 (2017): 96.
[3] X. Tong et al Nano Energy 441-449 (2017): 31.
(Invited) Surfactant-Directed Quantum Dot Self-Assembly on Unconventional GaAs Surfaces
Authors: Lewis Ryan B. 
Published: May 2020

The pursuit of integrated sources for quantum optics has motivated quantum dot research for decades. However, difficulties in controlling the geometry, symmetry and size-uniformity of self-assembled quantum dots has been a major roadblock in device development. While the Stranski–Krastanov (SK) growth of InAs three-dimensional (3D) islands has been extensively investigated on GaAs(001), the SK growth mode is not observed on GaAs (110) and {111}, the other low index surfaces of GaAs. This is unfortunate as these surfaces have symmetries (Cs and C3v, respectively) which differ from that of the (001) surface, and owing to their low energy they are often present in self-assembled nanostructures such as nanowires. Furthermore, the high symmetry of {111} surfaces is expected to yield quantum dots that are ideal for entangled photon emission.
Here we show that using a Bi surfactant to modify surface properties can profoundly influence epitaxial growth on GaAs (110) and (111)A surfaces. On GaAs(110), the Bi surfactant alters the fundamental growth mode of InAs from 2D layer growth to a 3D SK mode. Furthermore, a morphological phase transition can be induced “on-demand” in static strained 2D InAs(110) layers by exposing them to Bi, resulting in a rapid rearrangement of the InAs layer into 3D islands. Small (110) QDs are coherently strained to the substrate. These islands are optically active and exhibit emission that is linearly polarized, showing perspective for polarized single-photon emitters. On GaAs(111)A, GaAs buffer layer growth under a Bi flux results in ultra-smooth surfaces, which are free from the typically-observed morphological defects. Similar to the (110) case, exposing 2D InAs/GaAs(111)A layers to Bi induces the InAs 3D island self-assembly. These findings illustrate how surface-energy-modifying surfactants open the door to QDs synthesis on new substrates and with new materials.
(Invited) Oxide-Based Luminiscent and Active Nanophotonic Structures
Authors: Serna Rosalia , Toudert Johann , Gonzalo Jose , Mariscal Antonio , Soria Esther , Gomez-Rodriguez Pilar 
Published: May 2020

In this talk we will discuss the potential of oxides for novel plasmonic and photonic devices. For this purpose, we have designed and produced highly functional thin film oxide metamaterials by either embedding non-oxide nanoparticles which act as optical resonators, or by growing pure nanostructured oxides with a fine control of their composition. In the former case we build robust plasmonic and sensing platforms that profit from the coupling between plasmonic and photonic modes[1-3]. And in the latter case we control the band-gap and thus the optical response tuning of the nanostructured oxide, thus creating a platform for integrated photonics [4]. In this context we will show the light emission properties of Europium oxides that can range from wide white band to narrow red emission, and how the coupling with metallic nanostructures enhances and modifies their spectral response.
[1]. J. Toudert, R. Serna, I. Camps, J. Wojcik, P. Mascher, E. Rebollar, T. Ezquerra, J. Phys. Chem. C 121, 3511 ( 2017).
[2] G. Baraldi, M.García Pardo, J. Gonzalo, R. Serna and J. Toudert, Adv. Mater. Interfaces 5, 1870058 (2018).
[3] J. Toudert, R. Serna, M. Pardo, N. Ramos, R. Peláez, and B. Maté, Opt. Express 26, 34043 (2018).
[4] A. Mariscal, A. Quesada, A. Tarazaga Martín-Luengo, Miguel A. García, A. Bonanni, J.F. Fernández and R. Serna, Appl. Surf. Science 456,980 (2018).
Influence of Different Carbon Precursors on Optical and Electrical Properties of Silicon Carbonitride Thin Films
Authors: Abdelal Aysegul , Khatami Zahra , Mascher Peter 
Published: May 2020

Silicon carbonitride (SiCN) thin films are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another scope of study of SiCN thin films is as the low dielectric constant (LKC) materials, which are desired for replacing silicon oxide (SiO2) in integrated circuits (IC). SiCN owes the interest shown to being an intermediate compound between silicon nitride (Si3N4) which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with excellent mechanical performance.
In this study we present the optical and electrical properties of SiCN:H thin films fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) by using a mixture of acetylene (C2H2) or methane (CH4), silane (SiH4), argon (Ar), and nitrogen (N2) gas precursors. Samples fabricated with two different carbon sources were analyzed and compared regarding their chemical composition as well as their electrical and optical properties. The atomic composition of Si, C, N, O, and H were determined by Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analysis and the chemical bonds formed in SiCN:H were analyzed through Fourier transform infrared spectroscopy (FTIR). Optical bandgap, index of refraction and extinction coefficient were analyzed by variable angle spectroscopic ellipsometry (VASE) and will be presented for different deposition conditions. The dielectric constants and dielectric breakdown voltages of the thin films were determined through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Lastly, the hardness properties are explained due to varying C and H concentrations.
Porous Silica as a Nanotemplate for the Solid State and Liquid Phase Synthesis of Luminescent Carbon Dots
Authors: Vasin A. V. , Kysil D. V. , Sevostianov S. V. , Isaieva O. , Rudko G. Yu. , Yatskiv Roman , El Hamzaoui H. , Capoen B. , Bouazaoui M. , Tertykh V. , Nazarov A. N. 
Published: May 2020

Samples of nanoporous silicon oxide (pore size of 40 nm and 6 nm with specific are of 90 m2/g and 233 m2/g respectively) were synthesised by sol-gel method and used as nanotemplate for solid stated and liquid phase synthesis of lluminescent carbon nanodots (nanoagregates). Solid state method was two step process of chemical treatment of porous silicas by toluene solution of phenylstrimethoxisilane followed by pyrolysis at temperature in range of 400-600 0C for 60-180 minutes. Three characteristic emission bands in UV and VIS spectral range (360-380 nm, 410-420 nm, 440-450 nm) and their combinations were found in annealed por-SiO2:C depending on annealing time and temperature. The nature of light emission of pyrolytic carbon moieties in SiO2:C nanopowder was analysed and discussed in frame of the concepts of polycyclic carbon clusters and their aggregates based on the analogy with polycyclic organic molecules and luminescent carbon nanodots. It is suggested to assign the characteristic emission bands at about 380 nm and 420 nm to polycyclic carbon fluorophores with 2- and 3-ring structure respectively. The other low energy characteristic emission bands at wavelength 440-450 nm and higher are assigned to amorphous nanoaggregates. It is found that PL intensity of por-SiO2:C nanocomposite is sensitive to the absorption of the air. Response of the PL on absorption/desorption of air moieties was studied and discussed.
Hydrophylic carbon nanodots were synthesized by liquid phase thermolysis of sucrose in dimethyl sulfoxide solution at 200 0C that resulted in formation of luminescent colloid. Porous silica were infiltrated by this colloid and then dried. Luminescent moieties absorbed in porous silicas were then extracted in water resulting in aqueous solution that exhibited intense visible photoluminescence with maximum intensity at 430-440 nm and well pronounced excitation band at 360-400 nm. This emission is suggested to be assigned to hydrophilic amorphous carbon nanodots (nanoagregates). Examination of Z-parameter of the colloids gave a value of the size of carbonnanodots below 1 nm. Spectral parameters (maximum position and spectral width) of the emission and excitation of photoluminescence were found to be dependent on the size of the pores in porous silica template that can be assigned to the effect of the size and size distribution of carbon nanodots (nanoagregates).
As a summary, it was shown that nanoporous silica with high specific surface area can be used as solid state “container” for both solid state and liquid phase synthesis of carbon nanoemitters with emission spectrum variable from the near UV to the visible.
Surface Engineering of Cesium Lead Halide Perovskite Nanocrystals for Enhanced Air Stability
Authors: Lim Sung Nam , Kim Kiyoung , Song Shin Ae , Woo Ju Young 
Published: May 2020

Cesium lead halide perovskite nanocrystals (CsPbX3 NCs where X is Cl, Br, and I) have become of great interest to numerous researchers because CsPbX3 NCs exhibit highly bright photoluminescence (PL), very narrow full width at half maxima (FWHM) of PL spectra. Also, recently demonstrated soft and dynamic nature of crystal domain in CsPbX3 NCs triggered fundamental interests. However, very unfortunately, it has been known that CsPbX3 NCs are too much unstable under air environment. For instance, PL quantum yield shows drastic drop when the NCs are stored in air conditions. Also, NCs fuse together along [110] crystal direction which finally results in degradation of their initial properties. Therefore, preventing degradation of CsPbX3 NCs in air is the most crucial issue for wider deployment of CsPbX3 NCs.
Here, we report surface ligand transition from anionic oleate ligands to cationic oleylammonium ligand on the surface of CsPbX3 NCs. Addition of ZnX2 enables such surface ligand transition of NCs. Furthermore, exposure of fusion-vulnerable (110) facets is markedly inhibited when the surface is terminated with cationic oleylammonium ligands, possibly due to significant difference in formation energy of (100) and (110) facets.
Synthesis of Alkyl-Substituted Viologen Cation/Indanyl Anion Organic Charge Transfer Salts
Authors: Saito Erika , Yasuhara Taichi , Okada Shuji , Yamakado Ryohei , Matsui Jun , Katagiri Hiroshi , Fujiwara Wataru , Masuhara Akito , White Matthew , Headrick Randall , Yoshida Tsukasa 
Published: May 2020

Combination of ionic organic donor and acceptor to form crystalline salt can be an interesting strategy to obtain new types of organic semiconductors, since charge transfer (CT) excitonic properties are anticipated. We have previously achieved a novel CT salt from deprotonated 1,3-(bisdicyanomethylidene)indan anion (TCNIH-) and methyl viologen cation (MV2+) in a 2:1 composition. In this study, the n-alkyl chain length in viologen was systematically changed to find out the border for the evolution of CT character of the mixed salts. [1]
Propyl to hexyl viologens (PrV to HxV) were synthesized by quaternization of 4,4’-bipyridine using the corresponding 1-haloalkanes in the yields of 60-62%, whereas methyl, ethyl, heptyl and octyl viologens (MV, EV, HpV, OV) were commercially available. Co-crystals with TCNIH- were precipitated by mixing with viologens at 2 : 1 ratio in water, filtrated and recrystallized from ethanolic solutions. While their crystal structures were examined on powder samples and single crystals, their optical properties were studied by measuring UV-vis and photoluminescence (PL) spectra for CT excitation.
Co-crystals with TCNIH- were obtained for all viologens in a 2:1 ratio in the yields of 39-44%. While Na+ salt with TCNIH- preserves the character of the deprotonated TCNIH- in solution, showing a peak at around 590 nm and its absorption extending up to around 850 nm, those with RV2+ having short alkyl chains exhibit absorption towards NIR range and concomitant decrease of visible absorption, due to CT from TCNIH- to RV2+ (Fig. 1). A clear border can be found between PnV and HxV, as the CT absorption is significantly decreased when R is longer than Hx.
Crystal structures of the mixed salts were identified as monoclinic for MV, BV, HxV salts, while triclinic for the others. The powder XRD data as well as melting points determined by differential scanning calorimetry indicated significant enlargement of donor-acceptor distances, decrease of melting point, and thereby weakened interaction to account for the observed CT characters. Coulombic interaction between donor and acceptor result in close packing of these co-crystals for their CT characters, whereas it is hindered when alkyl chains longer than Hx is introduced. However, PL from CT states was observed for all the compounds, as the salts with HxV, HpV and OV also showed clearly longer emission than that of Na salt, indicating primary excitation confined in TCNIH-, followed by its relaxation down to the CT states in such salts.
Reference
[1] E. Saito, et al., ECS Trans., 2018, 88, 301-311

Figure 1
(Invited) Biodegradable Light-Emitting Organic Materials
Authors: Santato Clara 
Published: May 2020

(Opto)electronics is one of our most developed and pervasive technologies.
The enduring high demand for (opto)electronics and their energy powering components has led to massive amounts of Waste of Electrical & Electronic Equipment (WEEE).
We will discuss our research efforts on the integration of solution-processable electro- and photo-active organic electronic nanomaterials available from biomass feedstock into (opto)electronic and energy technologies, such as light-emitting transistors and batteries, to minimize their environmental footprint.
We will include in our discussion preliminary results on the biodegradability of such photo-active nanomaterials.
Investigation of Li+ Insertion in NMC622 Cathode Material upon Deep Lithiation Via Electrochemistry and x-Ray Absorption Spectroscopy
Authors: Usubelli Camille , Besli Muenir Mustafa , Kuppan Saravanan , Metzger Michael , Christensen Jake , Gorlin Yelena 
Published: May 2020

Nickel-based cathode materials have become an exciting alternative to the widely used LixCoO2 (LCO) for consumer electronics. The main advantages of this type of cathode materials over the LCO electrodes are a higher practical capacity and excellent safety characteristics.[1] Additionally, the tendency to increase the nickel content of these electrodes proves to be cost effective due to their lower cobalt content.[2] One known drawback of nickel-containing layered cathodes is their poor first cycle efficiency of 87-88.6% when cycled in the standard potential window of 2.8 V to 4.4V, whereas LCO cathodes reach a first cycle efficiency of 98%.[3]
In this study, we focus on the electrochemical properties of LixNi0.6Mn0.2Co0.2O2 (NMC622) cathode materials. We start by demonstrating that it is possible to recover the capacity “lost” by the NMC622 electrode in the first cycle by increasing the applied overpotential, as was previously shown for other nickel-based cathodes, including LiNiO2, LiNi1/3Mn1/3Co1/3O2, and LiNi0.8Co0.10Al0.05O2.[3-4] We then establish through electrochemical measurements that it is possible to overlithiate the NMC622 cathode material by as much as 300 mAh/g relative to the pristine electrode. Finally, we complement our electrochemical characterization with ex-situ X-ray diffraction as well as soft and hard X-ray absorption spectroscopy experiments, to elucidate how the structure of the material and the oxidation states of the transition metals (nickel, cobalt, manganese) change throughout the overlithiation process.
[1] Andre, D. et al. Future generations of cathode materials: An automotive industry perspective. J. Mater. Chem. A
3, 6709–6732 (2015).
[2] Xu, J., Lin, F., Doeff, M. M. & Tong, W. A review of Ni-based layered oxides for rechargeable Li-ion batteries. J. Mater. Chem. A
5, 874–901 (2017).
[3] Kang, S. H., Yoon, W. S., Nam, K. W., Yang, X. Q. & Abraham, D. P. Investigating the first-cycle irreversibility of lithium metal oxide cathodes for Li batteries. J. Mater. Sci.
43, 4701–4706 (2008).
[4] Dahn, J. R., von Sacken, U. & Michal, C. A. Structure and electrochemistry of Li1+/-xNiOz and a new Li2Ni02 phase with the Ni (OH) 2 structure. Solid State Ionics
44, 87–97 (1990).
Synthesis of Colloidal Nitrogen-Doped Graphene Quantum Dots with Tunable Bandgaps Using Atmospheric Pressure Microplasmas
Authors: Kurniawan Darwin , Chiang Wei-Hung 
Published: May 2020

Graphene quantum dots (GQDs) have obtained a great of research interest owing to their unique material properties including tunable bandgaps, biocompatibility, chemical and photo-stability, controlled functionalization, and low toxicity, making then promising candidate for applications including bioimaging, chemical and biological sensing, drug delivery, energy conversion and storage, catalysis, and optoelectronics. However, the low quantum yield (QY) and difficulty to synthesize have hampered the commercialization of GQDs. Nitrogen (N) doping of GQDs has been shown as an effective approach to enhance the QY and further change the materials properties. It is needed to develop a scalable, controlled and environmental-friendly method to synthesize N-doping GQDs (NGQDs).
Here we demonstrate a simple microplasma-based approach for NGQD synthesis. Recently, microplasma has attracted a lot of attentions due to its advantages for nanomaterials synthesis. Chitosan was used as the raw carbon and nitrogen sources for producing NGQDs. Three different acids including HCl, HNO3, and CH3COOH were used to mix with the precursors. Generation of energetic species including radicals and electrons were found to initiate electrochemical reactions and simultaneously nucleate nano-size graphene and growth of NGQDs. Microscopic and spectroscopic studies suggest NGQD with controlled particle size, N dopant concentrations and bandgaps can be achieved by adjusting the process conditions. Our work provides a simple, scalable and green method for synthesis of GQD with well-defined structures.