Article
Materials Science, Multidisciplinary
H. Mekni, A. Pankratov, S. Ben Radhia, K. Boujdaria, M. Chamarro, C. Testelin
Summary: The exciton fine structure of asymmetric GaAs/AlGaAs quantum dots obtained through Al droplet epitaxy and nanoholes formation was calculated, showing LR and SR contributions to the EI. LR accounts for 5 to 68% of bright-dark splitting and 69 to 76% of bright-bright splitting in experimentally explored sizes.
Article
Physics, Applied
A. Tuktamyshev, A. Fedorov, S. Bietti, S. Vichi, K. D. Zeuner, K. D. Jons, D. Chrastina, S. Tsukamoto, V. Zwiller, M. Gurioli, S. Sanguinetti
Summary: In this study, self-assembly of InAs/InAlAs quantum dots was achieved using the droplet epitaxy technique on vicinal GaAs(111)A substrates. The small miscut angle, along with preferential nucleation sites at step edges, allowed for fast growth while maintaining quantum dot symmetry. These quantum dots emit in the 1.3 μm telecom O-band with low fine structure splitting, making them suitable for photon sources in quantum communication networks utilizing entangled photons.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Marco Abbarchi, Takaaki Mano, Takashi Kuroda, Akihiro Ohtake, Kazuaki Sakoda
Summary: The study found that quantum dots on (311)A and (111)A surfaces have larger carrier confinement due to the absence of a wetting layer, leading to a more pronounced dependence of the binding energies of s-shell excitons on quantum dot size, while for (001) surfaces, the presence of a wetting layer reduces the fine structure splitting by about one order of magnitude.
Article
Materials Science, Multidisciplinary
Elisa M. Sala, Max Godsland, Aristotelis Trapalis, Jon Heffernan
Summary: By utilizing capping layer engineering, the size and shape of InAs quantum dots can be controlled, allowing for tuning of the emission wavelength across a broad range. Experimental results were verified optically and morphologically through various detection methods.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Yeonhwa Kim, Rafael Jumar Chu, Geunhwan Ryu, Seungwan Woo, Quang Nhat Dang Lung, Dae-Hwan Ahn, Jae-Hoon Han, Won Jun Choi, Daehwan Jung
Summary: By reducing the thickness of the GaAs buffer and inserting an Al0.4Ga0.6As electron barrier layer, photoluminescence enhancement of QDs can be achieved, leading to the fabrication of efficient light-emitting diodes on a silicon substrate.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Nanoscience & Nanotechnology
Elisa M. Sala, Max Godsland, Young In Na, Aristotelis Trapalis, Jon Heffernan
Summary: InAs quantum dots were successfully fabricated on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix using droplet epitaxy. The presence of the In0.53Ga0.47As interlayer prevented the formation of non-stoichiometric 2D layers and affected the size of the resulting quantum dots.
Article
Nanoscience & Nanotechnology
Raja S. R. Gajjela, Niels R. S. van Venrooij, Adonai R. da Cruz, Joanna Skiba-Szymanska, R. Mark Stevenson, Andrew J. Shields, Craig E. Pryor, Paul M. Koenraad
Summary: We investigated the structural characteristics of InAs/InP quantum dots grown by metal-organic vapor phase epitaxy using droplet epitaxy (DE) and Stranski-Krastanov (SK) methods. Our atomic-scale comparison revealed that DE produces more uniform and shape-symmetric quantum dots. We also observed localized etch pits for the first time in InAs/InP DE quantum dots and discussed the etching mechanism. This study provides valuable feedback for optimizing quantum dot growth for applications in quantum technology.
Article
Physics, Applied
Im Sik Han, Yun-Ran Wang, Mark Hopkinson
Summary: Highly ordered arrays of GaAs/AlGaAs quantum dots (QDs) were fabricated by droplet epitaxy using in situ direct laser interference patterning. The size distribution and optical properties of the ordered GaAs QDs were optimized by carefully choosing parameters for nucleation and droplet formation.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Analytical
Yong Du, Wenqi Wei, Buqing Xu, Guilei Wang, Ben Li, Yuanhao Miao, Xuewei Zhao, Zhenzhen Kong, Hongxiao Lin, Jiahan Yu, Jiale Su, Yan Dong, Wenwu Wang, Tianchun Ye, Jianjun Zhang, Henry H. Radamson
Summary: The development of low dislocation density Si-based GaAs buffer is crucial for InAs/GaAs quantum dot lasers in photonic integrated circuits. Through the use of an engineered Ge-buffer on Si, thermal cycle annealing, and filtering layers, the dislocation density in the laser's active part was controlled. The study also investigated the optical properties of InAs quantum dots at different growth temperatures.
Article
Computer Science, Information Systems
Sergey Balakirev, Natalia Chernenko, Natalia Kryzhanovskaya, Nikita Shandyba, Danil Kirichenko, Anna Dragunova, Sergey Komarov, Alexey Zhukov, Maxim Solodovnik
Summary: We studied the influence of arsenic pressure on the low-temperature GaAs overgrowth of InAs quantum dots and their optical properties. High arsenic pressure led to a unimodal size distribution of quantum dots and lower photoluminescence intensity. Low arsenic pressure resulted in the formation of arrays of quantum dots with larger sizes.
Article
Crystallography
Sergey Balakirev, Danil Kirichenko, Natalia Chernenko, Nikita Shandyba, Sergey Komarov, Anna Dragunova, Natalia Kryzhanovskaya, Alexey Zhukov, Maxim Solodovnik
Summary: In this study, we demonstrate the significant influence of arsenic pressure used for high-rate GaAs capping on the optical properties of self-assembled InAs quantum dots. An increase in overgrowth arsenic pressure leads to a red shift in the photoluminescence peak position, which can be explained by the different intensities of quantum dot decomposition. High arsenic pressure results in a GaAs capping layer that has a low impact on the initial quantum dots, while low arsenic pressure leads to intensive intermixing. This study provides evidence for the strong effect of overgrowth arsenic pressure on the characteristics of InAs quantum dots.
Article
Chemistry, Physical
Sergey Balakirev, Danil Kirichenko, Natalia E. Chernenko, Nikita A. Shandyba, Mikhail M. Eremenko, Oleg A. Ageev, Maxim S. Solodovnik
Summary: This paper presents a novel droplet epitaxial technique for fabricating small-sized nanostructures, achieving low size dispersion and high reproducibility of quantum dots through a two-stage crystallization process in different arsenic fluxes.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Applied
Junjie Yang, Zizhuo Liu, Pamela Jurczak, Mingchu Tang, Keshuang Li, Shujie Pan, Ana Sanchez, Richard Beanland, Jin-Chuan Zhang, Huan Wang, Fengqi Liu, Zhibo Li, Samuel Shutts, Peter Smowton, Siming Chen, Alwyn Seeds, Huiyun Liu
Summary: This paper investigates the replacement of a thin Ge buffer layer for part of the GaAs buffer layer in a III-V quantum-dot laser grown on Si, resulting in improved laser performance. By using this approach, a very high operating temperature of 130 degrees Celsius has been demonstrated for the InAs/GaAs QD laser.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Abhiroop Chellu, Eero Koivusalo, Marianna Raappana, Sanna Ranta, Ville Polojarvi, Antti Tukiainen, Kimmo Lahtonen, Jesse Saari, Mika Valden, Heli Seppanen, Harri Lipsanen, Mircea Guina, Teemu Hakkarainen
Summary: Several passivation techniques for close-to-surface InAs/GaAs quantum dots were compared for their ability to preserve optical properties. It was found that AlNx passivation method significantly reduces surface recombination velocity and shows long-term stability.
Article
Nanoscience & Nanotechnology
Raja Sekhar Reddy Gajjela, Elisa Maddalena Sala, Jon Heffernan, Paul M. Koenraad
Summary: We present a detailed atomic-resolution study of morphology and substrate etching mechanism in InAs/InP droplet epitaxy quantum dots (QDs) grown by metal-organic vapor phase epitaxy via cross-sectional scanning tunneling microscopy (X-STM). We observed two different etching processes, local drilling and long-range etching, depending on the crystallization temperature. The study also revealed the formation of trenches and provided insights into the composition and fine structure splitting of the QDs.
ACS APPLIED NANO MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Yasemin Ozbek, Cooper Brooks, Xuanyi Zhang, Athby Al-Tawhid, Vladmir A. Stoica, Zhan Zhang, Divine P. Kumah
Summary: The complex relationship between the growth conditions and the structural and transport properties of TixOy thin films grown by molecular beam epitaxy is investigated. The O/Ti ratio is effectively tuned by the Ti flux rate and the O partial pressure P-Ox, leading to the stabilization of transport properties ranging from metallicity to superconductivity and insulating states. A cubic c-TiO1 +/-delta buffer layer or a corundum cr-Ti2O3 layer is formed depending on the O/Ti ratio. The insulator-superconducting transition is observed in 85 nm thick films at 4.5 K (T-C(onset)=6K) with the nucleation of the superconducting gamma-Ti3O5 Magneli phase on a c-TiO1-delta buffer.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Athby H. Al-Tawhid, Jesse Kanter, Mehdi Hatefipour, Divine P. Kumah, Javad Shabani, Kaveh Ahadi
Summary: We have observed two-dimensional superconductivity and weak anti-localization at the TiOx/KTaO3 (111) interfaces, indicating the coexistence of superconducting fluctuations and quantum coherent quasiparticle effects.
JOURNAL OF ELECTRONIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Ni Yang, Xuanyi Zhang, Lewis Reynolds, Divine Kumah, Chengying Xu
Summary: A facile and novel processable method using polymer-derived ceramics (PDCs) is reported for synthesizing Ni nanoparticles (Ni NPs) in the silicon oxycarbide (SiOC) ceramic system, allowing control over their size. The specific structural characteristics and magnetic properties of Ni NPs/SiOC composites with varying carbon content were systematically investigated. It was found that the size of the Ni NPs determines their superparamagnetic behavior, with the magnetic properties changing with NP size and measurement temperature.
ADVANCED ENGINEERING MATERIALS
(2023)
Review
Chemistry, Multidisciplinary
Shira Yochelis, Yossi Paltiel
Summary: Chirality is a fundamental chemical property that exists in various aspects of life. Detecting and quantifying chirality are important in multiple fields, including analytical chemistry, biological chemistry, and pharmacology. Traditional methods for chiral detection have limitations, and recent research has proposed new approaches using spin currents. This review summarizes different methods for electrical measurements of chirality using spin currents.
ISRAEL JOURNAL OF CHEMISTRY
(2022)
Article
Nanoscience & Nanotechnology
Thi Ngoc Ha Nguyen, Yossi Paltiel, Lech T. Baczewski, Christoph Tegenkamp
Summary: Propagation of electrons along helical molecules on surfaces exhibits a spin polarization effect called chirality induced spin selectivity. In this study, we investigated the structure of self-assembled chiral molecules and their electronic transmission and spin polarization using scanning tunneling microscopy and spectroscopy. We found phase separation of the molecules into well-ordered 2D hexagonal phases and quasi-1D heterochiral-dimer structures, which allowed for precise analysis of spin polarization. Our results demonstrate the importance of intermolecular interaction and coupling to the substrate in achieving high chirality induced spin selectivity.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Ankit Negi, Hwang Pill Kim, Zilong Hua, Anastasia Timofeeva, Xuanyi Zhang, Yong Zhu, Kara Peters, Divine Kumah, Xiaoning Jiang, Jun Liu
Summary: This paper demonstrates the room-temperature thermal modulation in 2.5 mm-thick Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-xPT) single crystals. Through the use of advanced poling conditions and a systematic study on composition and orientation dependence, a range of thermal conductivity switching ratios, with a maximum of approximately 1.27, is observed. The simultaneous measurements of piezoelectric coefficient (d(33)), domain wall density using polarized light microscopy (PLM), and birefringence change using quantitative PLM reveal an increase in domain wall density at intermediate poling states (0< d(33)< d(33(max)) compared to the unpoled state.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Meital Ozeri, Jiahui Xu, Gilad Bauer, Linde A. B. Olde Olthof, Graham Kimbell, Angela Wittmann, Shira Yochelis, Jonas Fransson, Jason W. A. Robinson, Yossi Paltiel, Oded Millo
Summary: We investigate the phase-coherent transport properties of Cu and Au thin films with adsorbed chiral molecules through low-temperature magneto-conductance measurements. The adsorption of chiral molecules reduces the spin-orbit coupling strength in Cu and induces ferromagnetism in the Au films. Our theoretical model suggests that anisotropy in the molecular tilt angles, acting as magnetic moments, leads to a nonvanishing magnetic exchange interaction, resulting in changes in the spin-orbit coupling strength in Cu and Au. Our work provides a new perspective on the unique phenomena arising from the adsorption of chiral molecules on materials.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Ankit Negi, Alejandro Rodriguez, Xuanyi Zhang, Andrew H. H. Comstock, Cong Yang, Dali Sun, Xiaoning Jiang, Divine Kumah, Ming Hu, Jun Liu
Summary: In this study, the thermal conductivity and phonon mean free path (MFP) distribution of barium titanate (BTO) were determined through experimental measurements and first-principles modeling. The results show that phonons with sub-100 nm MFP dominate the thermal transport in BTO, and phonons with MFP exceeding 10 nm contribute approximately 35% to the total thermal conductivity. These findings are consistent with the theoretical predictions of other crystals with strong anharmonicity.
Article
Multidisciplinary Sciences
Ethan G. Arnault, Athby H. Al-Tawhid, Salva Salmani-Rezaie, David A. Muller, Divine P. Kumah, Mohammad S. Bahramy, Gleb Finkelstein, Kaveh Ahadi
Summary: A two-dimensional, anisotropic superconductivity was found at the KTaO3(111) interfaces, which violates the Pauli limit and is robust against in-plane magnetic field. The study shows that the Cooper pairs are more resilient when the bias is along [112] and the magnetic field is along [110]. The anisotropic nature of superconductivity is discussed in the context of electronic structure, orbital character, and spin texture at the KTaO3(111) interfaces.
Article
Chemistry, Physical
Christina M. Niman, Nir Sukenik, Tram Dang, Justus Nwachukwu, Miyuki A. Thirumurthy, Anne K. Jones, Ron Naaman, Kakali Santra, Tapan K. Das, Yossi Paltiel, Lech Tomasz Baczewski, Mohamed Y. El-Naggar
Summary: Metal-reducing bacteria have adapted the ability to respire extracellular solid surfaces using multiheme cytochromes. Recent studies show that some of these proteins exhibit a chiral induced spin selectivity (CISS) effect, which facilitates efficient electron transport by reducing backscattering probability. This study extends the investigation of CISS to membrane-associated and periplasmic proteins, and confirms spin selectivity in MtrA and STC.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Yael Kapon, Fabian Kammerbauer, Shira Yochelis, Mathias Klaeui, Yossi Paltiel
Summary: Chiral molecules have the potential to create new magnetic devices by locally manipulating the magnetic properties of metallic surfaces. By chemisorbing onto ferromagnets, chiral polypeptides can induce magnetization locally through spin exchange interactions. In this study, magneto-optical Kerr microscopy was used to directly image surface magnetization changes induced by chiral molecules, demonstrating their ability to control and manipulate magnetization.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Anu Gupta, Anil Kumar, Deb Kumar Bhowmick, Claudio Fontanesi, Yossi Paltiel, Jonas Fransson, Ron Naaman
Summary: This study explores the impact of electron interactions on the oxygen reduction reaction (ORR), revealing that electron transfer is controlled by a hidden property related to coherent phase relations. Experimental results confirm the special relation between electrons and the importance of coherence, while multiple scattering events disrupt this relation and reduce reaction efficiency.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Athby H. H. Al-Tawhid, Samuel J. J. Poage, Salva Salmani-Rezaie, Antonio Gonzalez, Shalinee Chikara, David A. A. Muller, DivineP. P. Kumah, Maria N. N. Gastiasoro, Josei Lorenzana, Kaveh Ahadi
Summary: In this study, epitaxial LaMnO3/KTaO3(111) heterostructures were grown to investigate the nature of superconductivity under in-plane magnetic fields. It was found that superconductivity remains robust in optimally doped heterostructures, with a critical field of approximately 25 T. The superconducting order parameter is highly sensitive to carrier density. The formation of anomalous quasiparticles with vanishing magnetic moment, driven by spin-orbit coupling, provides significant immunity against magnetic fields beyond the Pauli paramagnetic limit. These findings present opportunities for designing superconductors with extreme resilience against applied magnetic fields.
Article
Physics, Applied
G. Bauer, M. Ozeri, M. S. Anwar, H. Matsuki, N. Stelmashenko, S. Yochelis, M. Cuoco, J. W. A. Robinson, Y. Paltiel, O. Millo
Summary: We studied the voltage-current characteristics of a superconductor-insulator-ferromagnet heterostructure, with pinhole-defects in the insulating layer. The superconducting layer exhibited multiple voltage jumps that were hysteric with the current sweep direction. This behavior was attributed to pinholes inducing local, distinct, coupling regions between the superconducting and ferromagnetic layers, which could potentially be used in the design of a magnetically driven superconductor memristor. Additionally, the junctions displayed absolute and differential negative resistances below the superconducting critical temperature and current, which was analyzed using a circuit approach and attributed to current passing through pinholes within the insulating layer. These unique effects stemming from the pinhole-governed interface topology could have applications in superconductor-based switches and memory devices.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2023)
Article
Multidisciplinary Sciences
S. Furkan Ozturk, Deb Kumar Bhowmick, Yael Kapon, Yutao Sang, Anil Kumar, Yossi Paltiel, Ron Naaman, Dimitar D. Sasselov
Summary: Homochirality is a key characteristic of life on Earth, but its origins are unknown. Magnetic mineral surfaces can act as chiral agents, but are typically weakly magnetized. In this study, the authors report a method to achieve uniform magnetization of magnetic surfaces by using an RNA precursor, which spreads like an avalanche on the surface.
NATURE COMMUNICATIONS
(2023)
