Article
Chemistry, Physical
Kim Lopez-Guell, Nicolas Forrer, Xavier Cartoixa, Ilaria Zardo, Riccardo Rurali
Summary: Crystal phase engineering can alter phonon transport, and twinning superlattices exhibit two transportation mechanisms depending on interface number and spacing.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Kim Lopez-Guell, Nicolas Forrer, Xavier Cartoixa, Ilaria Zardo, Riccardo Rurali
Summary: Crystal phase engineering allows for the manipulation of phonon transport in periodic nanostructures, such as twinning superlattices. This study focuses on GaAs and InAs twinning superlattices and identifies two distinct transport regimes, one where each interface behaves as an independent scatterer and another where a segment with closely spaced interfaces acts as a metamaterial with its own thermal properties.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Physics, Multidisciplinary
An-Tian Du, Ruo-Tao Liu, Chun-Fang Cao, Shi-Xian Han, Hai-Long Wang, Qian Gong
Summary: A 1.3-& mu;m InAs quantum dot laser has been fabricated on a GaAs(100) substrate by molecular beam epitaxy (MBE) technique using InAs/GaAs digital alloy superlattices instead of the conventional InGaAs layer. The samples grown by conventional growth method and the digital alloy superlattice growth method are characterized by atomic force microscope (AFM) and photoluminescence (PL) spectroscopy. The results show that the quality of the grown sample improves with the increase of InAs/GaAs period, and the InAs quantum dot lasers fabricated by the sample grown by digital alloy superlattice method have good performances.
ACTA PHYSICA SINICA
(2023)
Article
Chemistry, Multidisciplinary
Xiao Xu, Yi Huang, Xixi Liu, Baohai Jia, Juan Cui, Ran He, Jinghan Wang, Yiyuan Luo, Kornelius Nielsch, Jiaqing He
Summary: This work focuses on the characterization and controllability of gap-like structures in GeTe-rich Sb2Te3(GeTe)(n) samples, and demonstrates their significant impact on thermal transport and thermoelectric performance. By tailoring the microstructure, the researchers achieved a considerable reduction in lattice thermal conductivity, resulting in high ZT values and improved efficiency. Additionally, a thermoelectric module fabricated using the improved material achieved exceptional power density and efficiency, showcasing the potential of this strategy in improving thermoelectric performance.
ENERGY & ENVIRONMENTAL SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Saher Gul, Selin Arican, Murat Cansever, Bertan Beylergil, Mehmet Yildiz, Burcu Saner Okan
Summary: The development of highly thermally conductive polymeric composites with hexagonal boron nitride (h-BN) filler in poly(ether ether ketone) (PEEK) matrix is studied. The optimized twin-screw extrusion melt compounding technique is used to achieve high thermal conductivity in both in-plane and through-plane directions. The prepared composites show enhanced crystallinity, thermal stability, and shear-thinning behavior. Rheological analysis provides viscosity profiles for different composite compositions, which can be used for advanced manufacturing processes.
ACS APPLIED POLYMER MATERIALS
(2023)
Article
Physics, Applied
Anna Spindlberger, Dmytro Kysylychyn, Lukas Thumfart, Rajdeep Adhikari, Armando Rastelli, Alberta Bonanni
Summary: The thermal conductivity of GaN/AlN superlattices as a function of layer thickness was established using the 3 omega-method, taking into account interdiffusion at the interfaces. It was found that the thermal conductivity can be driven to values as low as 5.9W/(m.K), comparable to those reported for amorphous films, suggesting wide perspectives for optimized heat management in III-nitride-based epitaxial multilayers.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Ara Ghukasyan, Pedro Oliveira, Nebile Isik Goktas, Ray LaPierre
Summary: This study utilized the three omega method to measure the thermal conductivity of two GaAs nanowire arrays with different crystal structures. The results showed that the nanowires with a twinning superlattice structure had a thermal conductivity nearly an order of magnitude lower than that of the bulk material.
Article
Chemistry, Physical
Komal Chawla, Jizhe Cai, Dakotah Thompson, Ramathasan Thevamaran
Summary: Thermal transport properties are crucial for lightweight foams used as shock-absorbing layers. This study demonstrates tailored thermal properties achieved by introducing a hexagonally close-packed cylindrical architecture in vertically aligned carbon nanotube (VACNT) foams. The architected VACNTs exhibit higher intrinsic thermal conductivity and lower intrinsic thermal resistance compared to non-architected VACNTs. These superior thermal transport properties enable the development of lightweight protective materials for extreme engineering applications.
Article
Multidisciplinary Sciences
Chanhee Kim, Dilip Bhoi, Yeahan Sur, Byung-Gu Jeon, Dirk Wulferding, Byeong Hun Min, Jeehoon Kim, Kee Hoon Kim
Summary: The study indicates that 2H-Pd0.08TaSe2 is a nodeless, multiband superconductor, with distinct characteristics under different temperatures and magnetic fields.
SCIENTIFIC REPORTS
(2021)
Article
Thermodynamics
Alessandro Ribezzo, Luca Bergamasco, Matteo Morciano, Matteo Fasano, Luigi Mongibello, Eliodoro Chiavazzo
Summary: The adoption of highly conductive nanofillers within a phase change material matrix is seen as a potential solution to improve the thermal conductivity and energy storage capacity. However, the performance enhancement is often limited due to high thermal resistances at the nanofiller-matrix interfaces. This study provides estimates of these resistances and demonstrates how numerical analysis can be used for the optimization of a storage system.
APPLIED THERMAL ENGINEERING
(2023)
Article
Chemistry, Physical
Aiyeshah Alhodaib
Summary: The electronic, mechanical, and transport properties of In-substituted GaAs were investigated using the TB-mBJ potential, BoltzTraP code, and Charpin tensor matrix analysis. The study showed that increasing the In concentration led to changes in directional symmetry, reduced bandgap, decreased electrical conductivity, and increased Seebeck coefficient. Additionally, the elastic moduli and thermal conductivity decreased as well.
Article
Chemistry, Physical
Adam J. Jackson, Benjamin J. Parrett, Joe Willis, Alex M. Ganose, W. W. Winnie Leung, Yuhan Liu, Benjamin A. D. Williamson, Timur K. Kim, Moritz Hoesch, Larissa S. I. Veiga, Raman Kalra, Jens Neu, Charles A. Schmuttenmaer, Tien-Lin Lee, Anna Regoutz, Tung-Chun Lee, Tim D. Veal, Robert G. Palgrave, Robin Perry, David O. Scanlon
Summary: This study demonstrates the ideal transparent conducting oxide ZnSb2O6 and identifies gallium as the optimal dopant for achieving high conductivity and transparency. Experimental validation of computational predictions shows that Ga-doped ZnSb2O6 exhibits behavior consistent with a degenerate transparent conducting oxide.
ACS ENERGY LETTERS
(2022)
Article
Thermodynamics
Akos Lakatos, Attila Csik, Istvan Csarnovics
Summary: This paper presents research results on the performance of aerogel materials in terms of thermal conductivity, specific heat, and combustion heat, providing important references for designers and researchers. The study found that temperature and external load significantly affect thermal conductivity, while thickness variations have minor impacts. Additionally, the combustion heat of aerogel was measured and investigated before and after combustion using advanced microscopy techniques.
CASE STUDIES IN THERMAL ENGINEERING
(2021)
Article
Physics, Multidisciplinary
Luyi Sun, Fangyuan Zhai, Zengqiang Cao, Xiaoyu Huang, Chunsheng Guo, Hongyan Wang, Yuxiang Ni
Summary: Anderson localization of phonons was observed in aperiodic boron nitride/carbon nanotube superlattices. The coexistence of aperiodicity and interfacial mixing was found to decrease thermal conductivity, while anharmonicity destroyed phonon localization at high temperatures. This work provides insights for designing thermoelectric materials with low thermal conductivity.
Article
Thermodynamics
Xiaojian Wang, Wenbo Gu, Hao Lu
Summary: In this study, a new relational expression is established to reveal the thermal conductivity performance of constructal fillers and the effect of filler shape. The thermal conductivity of the composite material goes through different stages with the increase of thermal contact resistance.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Chemistry, Physical
Sebastian Bichelmaier, Jesus Carrete, Georg K. H. Madsen
Summary: Given the high cost of ab-initio calculations, it is challenging to predict temperature-dependent phenomena in strongly anharmonic systems. A possible solution is to use a relatively inexpensive surrogate model for the potential energy surface to build temperature-dependent effective harmonic potentials. However, the results may only be valid in a narrow temperature range due to the limited flexibility of polynomials as approximants, leading to significant artifacts in derived quantities. A global interpolation strategy, such as a neural-network force field, is suggested as a better approach to cost-effective surrogate models.
INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
(2023)
Article
Chemistry, Inorganic & Nuclear
Elena Del Canale, Lorenzo Fornari, Chiara Coppi, Giulia Spaggiari, Francesco Mezzadri, Giovanna Trevisi, Patrizia Ferro, Edmondo Gilioli, Massimo Mazzer, Davide Delmonte
Summary: We have developed a new method to synthesize bulk indium nitride and bulk gallium nitride using a solid-state chemical reaction under high-pressure/high-temperature conditions. The reactions involve binary oxides and highly reactive nitrogen sources without the use of gases or solvents. The obtained materials are pure and can be produced in significant quantities for electronic and energy technologies.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Jesus Carrete, Hadrian Montes-Campos, Ralf Wanzenboeck, Esther Heid, Georg K. H. Madsen
Summary: A reliable uncertainty estimator is crucial for using machine-learning force fields effectively. This study proposes a generalized deep-ensemble design using multiheaded neural networks and a heteroscedastic loss to handle uncertainties in energy and forces and consider aleatoric uncertainty sources in training data. Uncertainty metrics are compared for deep ensembles, committees, and bootstrap-aggregation ensembles using data for an ionic liquid and a perovskite surface. An adversarial approach to active learning is demonstrated for progressively refining force fields, made possible by fast training with residual learning and a nonlinear learned optimizer.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Raveena Gupta, Sonali Kakkar, Bonny Dongre, Jesus Carrete, Chandan Bera
Summary: Nanostructuring is a well-known method to improve the thermoelectric figure of merit, but it has limitations in tuning the lattice thermal conductivity. The thermoelectric properties of the SnS monolayer are investigated under uniaxial compressive and tensile strains using first-principles calculations and the Boltzmann transport equation. It is found that applying uniaxial compressible and tensile strains along the armchair direction can significantly enhance the power factor and figure of merit of the material, making it a promising candidate for thermoelectric applications.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Michael Seidel, Yuhui Yang, Thorsten Schumacher, Yongheng Huo, Saimon Filipe Covre da Silva, Sven Rodt, Armando Rastelli, Stephan Reitzenstein, Markus Lippitz
Summary: Reliable single-photon sources, high coupling efficiency, and low propagation losses are key requirements for quantum plasmonic nanocircuits. The best overall performance of these nanocircuits is achieved by adding a spacer layer between the quantum dot and the plasmonic waveguide, resulting in an improved coupling efficiency through standing wave interference.
Review
Nanoscience & Nanotechnology
Gabriel Gomes, Marcos L. F. Gomes, Saimon F. Covre da Silva, Ailton Garcia Jr, Armando Rastelli, Odilon D. D. Couto Jr, Angelo Malachias, Christoph Deneke
Summary: This review discusses the influence of the inherently asymmetric strain state of rolled-up III-V heterostructure tubes on light emitters. Whispering gallery mode resonators built from rolled-up III-V heterostructures are briefly reviewed. The curvature and its influence on the diameter of the rolled-up micro- and nanotubes are discussed, as well as the possible strain states. Experimental techniques are essential to accurately determine the strain state for the emitters inside the tube wall.
Article
Nanoscience & Nanotechnology
Oleksandr I. Datsenko, Sergii Golovynskyi, Ana I. Perez-Jimenez, Marc Chaigneau, Andrii Golovynskyi, Iuliia Golovynska, Victoriya Shevchenko, Matteo Bosi, Luca Seravalli
Summary: The surface variation of the exciton and trion PL characteristics in a bilayer MoS2 flake grown on a SiO2/Si substrate by chemical vapor deposition was studied using Raman and photoluminescence hyperspectral mapping. The Raman modes and excitonic PL in the flake interior were found to be redshifted compared to those at the perimeter, which was attributed to the presence of tensile strain. The PL at the perimeter also experienced a blueshift, potentially due to a reduction in trion peak caused by electron outflow induced by weakening of tensile strain.
PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES
(2023)
Article
Chemistry, Physical
F. Esposito, M. Bosi, G. Attolini, F. Rossi, S. E. Panasci, P. Fiorenza, F. Giannazzo, F. Fabbri, L. Seravalli
Summary: The objective of this study was to compare MoS2 2-dimensional monolayer flakes grown by Chemical Vapour Deposition using different density gradients in the liquid precursors solution. The structures grown using glycerol showed a larger variability in the lateral size of the triangular structure with good crystalline quality, while structures grown using iodixanol exhibited poorer crystalline quality with nanometric pores and more homogeneous sizing of the triangular structures. The lower crystalline quality of iodixanol samples resulted in reduced light emission efficiency and lower mobility.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
L. Seravalli, F. Esposito, M. Bosi, L. Aversa, G. Trevisi, R. Verucchi, L. Lazzarini, F. Rossi, F. Fabbri
Summary: Strain engineering is an efficient tool for adjusting the electrical and optical properties of 2D materials. In this study, we found that the built-in strain in MoS2 monolayers grown on a SiO2/Si substrate is mainly dependent on the size of the monolayer. A critical size of 20 μm was identified, beyond which the built-in strain significantly increased. The maximum built-in strain was observed in a 60 μm sized monolayer, which resulted in 1.2% tensile strain with partial strain release near the triangular vertexes due to nanocrack formation. These findings suggest that the standard method for evaluating the number of layers based on Raman mode separation may be unreliable for highly strained monolayers with a lateral size above 20 μm.
Article
Materials Science, Multidisciplinary
T. Seidelmann, T. K. Bracht, B. U. Lehner, C. Schimpf, M. Cosacchi, M. Cygorek, A. Vagov, A. Rastelli, D. E. Reiter, V. M. Axt
Summary: Semiconductor quantum dots are a promising platform for generating polarization-entangled photon pairs, but current two-photon excitation schemes limit the achievable degree of entanglement due to introducing which-path information. This study investigates the combined impact of two-photon excitation and longitudinal acoustic phonons on photon pairs emitted by strongly-confining quantum dots. The findings show that phonons further reduce the achievable degree of entanglement, even at low temperature, due to phonon-induced pure dephasing and phonon-assisted one-photon processes.
Article
Materials Science, Multidisciplinary
Xueyong Yuan, Saimon F. Covre da Silva, Diana Csontosova, Huiying Huang, Christian Schimpf, Marcus Reindl, Junpeng Lu, Zhenhua Ni, Armando Rastelli, Petr Klenovsky
Summary: The optical properties of excitons in GaAs/AlGaAs quantum dots subjected to variable quasiuniaxial stress were examined. The quantum dot morphology and externally induced strain tensor at the quantum dot positions were determined to validate computational tools for describing nanostructure optical properties. The strain-dependent excitonic emission energy, degree of linear polarization, and fine-structure splitting were calculated using a combination of eight-band k • p formalism with multiparticle corrections using the configuration interaction method. The experimental observations were quantitatively well reproduced by the calculations and deviations were discussed.
Article
Materials Science, Multidisciplinary
Nahida Musayeva, Hadiya Khalilova, Bakhtiyar Izzatov, Giovanna Trevisi, Shahla Ahmadova, Muhammad Alizada
Summary: This work focuses on the preparation of nanocomposites based on multiwall carbon nanotubes (MWCNTs) and copper (Cu) nanoparticles using a chemical method, and investigates their sensing properties to hydrogen sulfide (H2S) gas. Different deposition methods were used to fabricate Cu decorated multiwall carbon nanotubes (MWCNTs/Cu), and their sensing properties were studied and compared. The impact of chemical functionalization of MWCNTs on the sensing properties of these nanocomposites was also examined. The obtained sensors demonstrated high sensitivity and selectivity to H2S gas at room temperature, and the chemical method showed higher sensitivity compared to the physical method.
C-JOURNAL OF CARBON RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Marco Girolami, Matteo Bosi, Valerio Serpente, Matteo Mastellone, Luca Seravalli, Sara Pettinato, Stefano Salvatori, Daniele M. M. Trucchi, Roberto Fornari
Summary: The photoelectronic properties of orthorhombic undoped kappa-Ga2O3 epitaxial thin films grown on sapphire substrates using metal-organic vapor phase epitaxy were evaluated for the first time. The films demonstrated linear photoresponse at low dose rates, excellent detection sensitivity, low dark current, and stability, making them promising for the fabrication of large-area X-ray detectors with minimum power consumption.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Nanoscience & Nanotechnology
Paola Frigeri, Enos Gombia, Matteo Bosi, Giovanna Trevisi, Luca Seravalli, Claudio Ferrari
Summary: In this study, we investigated the electrical and morphological properties of randomly arranged Ge nanowires on sapphire substrates. We fabricated nanowire-based devices to develop chemiresistive-type sensors for explosive vapor detection. We observed and discussed the critical role of nanowire-nanowire junctions on electrical conduction and sensing performances. Our proposed mechanism explains the high efficiency of annealed nanowire arrays in detecting 2,4,6-trinitrotoluene vapors. This study demonstrates the promising potential of Ge nanowire-based sensors in civil security.
Article
Materials Science, Multidisciplinary
Florian Kappe, Yusuf Karli, Thomas K. Bracht, Saimon Filipe Covre da Silva, Tim Seidelmann, Vollrath Martin Axt, Armando Rastelli, Gregor Weihs, Doris E. Reiter, Vikas Remesh
Summary: This study demonstrates that adiabatic rapid passage (ARP) can simultaneously excite biexciton states in multiple, spatially separated, and spectrally different quantum dots. Moreover, for positive chirps, the influence of phonons weakens the sensitivity to spectral detunings and reduces the required excitation power. This is a significant step towards implementing high photon rate, entanglement-based quantum key distribution protocols.
MATERIALS FOR QUANTUM TECHNOLOGY
(2023)
