Day 2 :
National Institute of Advanced Science and Technology, Japan
Time : 09:35-10:20
Chao Nan Xu is the Principle Research Manager at National Institute of Advanced Science and Technology (AIST), Founder and Chair of Mechanoluminescence Technology Consortium, Fellow of the Ceramic Society of Japan. She has been concurrently serving as Full Professor of New Material Lab at Kyushu University since 2005. She discovered the intensive new type of elasticoluminescence, and established the hybrid concept of inorganic/organic composite coating (skins) and the principle for quantitative analysis of stress/strain and faults. She also made discovery of grain size effect for gas sensitivity. She pioneered the new repeatable mechanoluminescent materials and their novel applications particularly in lighting, health care, and stress/strain visualization.
Piezoluminescence, which is also called elasticoluminescence, is a form of mechanoluminescence (ML) during the elastic deformation, which has attracted considerable attention because it can be repeatedly used for mechano-optical conversion. Elastic ML offers the advantages of wireless detection and nondestructive analysis, making it a promising candidate for various applications, such as stress sensing and damage diagnosis, and in particular for immediate in situ dynamic visualization of stress distribution in industrial plants, buildings, and living organisms. In piezoelectric materials, mechanical stimuli generate electricity, a phenomenon that is widely utilized in industry and daily life. Recently, we have found the first well-known piezo multifunctional material that exhibits both piezoelectricity and efficient elastic ML. By precisely tuning the Li/Nb ratio in nonstoichiometric LiNbO3:Pr3+, a material that exhibits an unusually high piezoluminescence intensity, which far exceeds that of any well-known piezoelectric material, is produced. LiNbO3:Pr3+ shows excellent strain sensitivity at the lowest strain level, with no threshold for stress sensing. These multipiezo properties are useful for nano-micro sensing, damage diagnosis, electro-mechano-optical energy conversion, and multifunctional control in optoelectronics.
S. N. Bose National Centre for Basic Sciences, India
Time : 10:20-11:05
Samit K Ray is currently the Director of S N Bose National Centre for Basic Sciences, Kolkata on lien from Indian Institute of Technology, Kharagpur. His research interests are in the area of semiconductor nanostructures, quantum dots, photovoltaics, nanodevices and electronic materials. He has published more than 300 research papers in peer reviewed journals, seven book chapters and co-authored a book on “Strained Silicon Heterostructures: Materials and Devices” published by IEE, UK.
We shall review our recent work on 2D/3D heterostructures for several electronic and photonic devices. The device using GO/Si on illumination shows a broadband (300 nm-1100 nm) spectral response with a characteristic peak at ~700 nm, in agreement with the photoluminescence emission from GO. Very high photo-to-dark current ratio (˃105) is observed upon illumination of UV light. On the other hand, transition metal dichalcogenides (TMDC), an emerging class of two dimensional materials are interesting due to the presence of a finite and direct energy gap in low dimensions, with a wide range of electronic and optical attributes. We have demonstrated the ability to gradually tailoring the optical properties of MoS2 nanocrystals in terms of PL response and optical absorption, making them attractive for future photonic devices. Chemical doping and plasmonic enhanced photoresponsivity of two dimensional (2D) n-WS2/p-Si heterojunctions have also been demonstrated. A sharp band-edge absorption of the hybrid material indicates the presence of spin–orbit coupled direct band gap transitions in WS2 layers, in addition to a broader plasmonic peak attributed to Ag nanoparticles. Stabilized Ag-nanoparticle (∼4–6 nm) embedded electron rich n-WS2 has been used to fabricate plasmon enhanced, silicon compatible heterojunction photodetectors. The detectors exhibited superior properties, possessing a photo-to-dark current ratio of ∼103, a very high responsivity (8.0 A W−1) and an EQE of 2000% under 10 V bias. The results provide a new paradigm for intercalant impurity-free metal nanoparticle assisted exfoliation of n-type few-layer WS2., with the nanoparticles playing a dual role by inducing chemical doping as well as tunable plasmon enhanced absorption.
- Condensed Matter Physics | Soft Condensed Matter Physics | Superconductivity | Nanoscale Physics
National Institute of Advanced Science and Technology, Japan
Samit K Ray
S N Bose National Centre for Basic Sciences, India
Saga University, Japan
X G Zheng is received his Ph.D. in Electrical Engineering from School of Engineering, Kyushu University during 1991/03. He worked as Assistant Professor in Department of Physics, Saga University during 1996 - 2005 and at present he is a Professor in Department of Physics, Saga University.
Hydroxyl salts exist in nature. The most familiar might be the hydroxyl chloride Cu2(OH)3Cl (atacamite), which forms naturally on copper and bronze as a green patina and is widely recognized as imparting characteristics to the Statue of Liberty. But only in recent years, their intriguing magnetism, with prominent geometric frustration, have been uncovered by us. Geometrically frustrated magnets, in which localized magnetic moments on triangular, kagome or pyrochlore lattices interact through competing exchange interactions, have been of intense recent interest due to the diversity in the exotic ground states that they display and potential applications that they may bring out. The diverse experimental reports of unconventional magnetic properties also provide challenge and testing ground for theoretical models. Till now, we have discovered that the hydroxyl salts of the type M2(OH)3Cl or M(OH)Cl, where M is a magnetic ion of Cu2+, Ni2+, Co2+, Fe2+, or Mn2+, are geometrically frustrated magnets resulting from their crystal structures as illustrated in figure I. Furthermore, in some of these compounds we found the occurrence of ferroelectricity with multiferroic features. In this talk, I will review our experimental results on hydroxyl salts, together with a brief introduction to a less-known experimental technique mSR.
University of Belgrade, Serbia
Zoran Borjan is an Associate Professor in Faculty of Physics, University of Belgrade and his works in the theory of phase transitions and critical phenomena. He uses continuum formulations in analysis of surface critical phenomena. Special emphasis is on the derivation of accurate results for systems of the Ising universality class in the experimentally most relevant spatial dimension d=3.
Critical adsorption of Ising systems in the presence of normal surface universality class is considered along the critical isochore, near coexistence and along the critical isotherm in cases of energy density and order-parameter and energy density, respectively. The problem is treated theoretically and by Monte-Carlo simulation method in spatial dimensions d=2, d=3 and theoretically in the mean-field limit. Excellent agreement between theory and the Monte-Carlo method is achieved within the study in d=3. Primary scaling densities such as order parameter and energy density manifest monotone behaviors with the relevant exception of non-monotone behaviors of energy density whenever an interface is present in systems. Two-dimensional analysis along the critical isotherm points to a new characteristic of low-dimensional Ising systems consisting of the interface de-localization. Above results are relevant to binary liquid mixtures, liquid-gas systems, ferromagnets, binary alloys and other physical systems of the Ising universality class near their corresponding critical points.
Xi’an Jiaotong University, P R China
Yong Zhang obtained his Bachelor’s in Department of Electron, Master’s in Department of Electron and Doctor Degree in Department of Measurement and Control Technology and Instrument from Xi’an Jiaotong University, respectively. She is a Professor in the School of Electrical Engineering of Xi’an Jiaotong University, a fixed Member of the State Key Lab of Electrical Institute and Power Equipment, a Senior Member of IEEE, and an expert Committee Member of Energy Equipment of China Energy Society. She has published 43 papers in international well-known publications (Scientific Reports of the Nature Publishing Group, Sensors and Actuators B: Chemical and so on). Twenty six of her patents have been authorized and 7 patents have been accepted by the Patent Office of China.
Nitric oxide NO is one of the major targets for environmental monitoring and causes environmental and human health problems. Hence, it is of significant importance to measure NO concentrations in the air. However, the existing NO sensors are limited by their low sensitivity and narrow test range. Here, a weakly ionized NO gas sensor employing multiwalled carbon nanotubes (MWCNTs) was fabricated, and its properties in NO-N2 mixture were investigated from both emission and ionization. The current Ie passing through the nanotubes cathode was found to decrease with increasing NO concentration and increase linearly in different slopes with the extracting voltage Ue. It is shown that the Schottky barrier of the MWCNTs calculated by Ie increased with NO concentration due to the adsorption of NO gas, which restrained the electron emission and consequently weakened the ionization. The positive ion currents Ic passing through the collecting electrode at different voltages of Ue were found to be monotonically decrease with increasing NO concentration which was induced by both of the reduced electron emission and the consumption of the two excited metastable states N2(A3Σu+) and N2(a′1Σu-) by NO. The sensor exhibited high sensitivity at the low temperature of 30℃. The calculated conductivity was found to be able to take place of Ic for NO detection in a wide voltage range of 80-150V Ue.
Pushan Ayyub is a Senior Professor and Chair in the Department of Condensed Matter Physics at the Tata Institute of Fundamental Research, Mumbai, India. He has over 160 publications in the general area of nanoscience. He was a Member of the International Committee on Nanostructured Materials (1998-2008) and is currently a Member of the Nano Mission Council of the Government of India. He is a Fellow of the Indian National Science Academy. His research interests include the size dependence of superconductivity and ferroelectricity. He is particularly interested in size-induced structural phase transitions and stabilization of novel crystal structures.
With a decrease in the particle size, the lattice parameters in a large class of metallic nanoparticles (Ag, Al, Au, Cu, Ni, Pd, Pt, Bi, Sn, etc.) show a contraction as compared to their corresponding bulk values. Interestingly, among the metal nanoparticles listed above that exhibit a lattice contraction, all except Bi and Sn have a face centered cubic (fcc) crystal structure. The size dependence of the lattice parameter in fcc metals can be generally fitted to a Laplace-Young type equation, which suggests that they can be represented by a simple liquid-droplet model in which surface-tension-like forces are the most dominant. On the other hand, the few metals known to exhibit a systematic lattice expansion in the nanoparticle form include Cr, Fe, Nb, V and Ta, each of which happens to have a body centered cubic (bcc) structure. To understand the physical basis for this striking empirical correlation, we have carried out a detailed microscopic study based on ab-initio density functional theory (DFT). Our simulations on representative bcc (Nb) and fcc (Cu) nanoclusters elucidate the importance of a capping layer on the metal nanoparticles and succeed in provide a consistent understanding of this apparently puzzling observation. It is important to appreciate that size-driven changes in the lattice parameters is a non-trivial effect with significant consequences, in some cases dominating over quantum size effects and other types of surface effects. Thus, size-induced lattice expansion has been invoked to understand the (a) persistence of superconductivity down to unexpectedly small sizes, (b) appearance of a magnetic moment in isolated Fe atoms embedded in a nanocrystalline metals, and (c) destruction of ferroelectricity in nanocrystalline oxides.
Hassan II University of Casablanca, Morocco
Mohamed El Hafidi is Professor of Quantum Physics and Magnetism at Hassan University II of Casablanca (Morocco) since 1985. He prepared a part of his PhD at the High Magnetic Field Laboratory (Grenoble, France) and he stayed as a visiting professor as a visiting professor at Joseph Fourier University of Grenoble. He currently supervises research on topological structures and low dimensionality magnetic systems.
Over the last few years, magnetic nanoparticles (nanotubes and nanowires) have attracted the interest of experimental and theoretical researches owing to their quantum importance, surface boundary effects and their promising technological applications such as drug delivery, biomedicine, magnetic resonance (MRI), permanent magnets, long-lasting memories and recording media. In this work, we study a single-walled hexagonal spin-S (S=½ or 1) Ising nanotube on the basis of the effective-field theory (EFT) with correlations and the differential operator technique (DOT). In the six-leg spin nanotube, each spin is connected to its nearest-neighbors through exchange couplings both along the chains (J//) and adjacent chains (J⊥). Exact expressions for of magnetization, initial susceptibility, critical temperature are obtained as well as the ground phase diagram that is established for different exchange couplings. Some interesting phenomena are revealed, especially for opposite exchange interactions, magnetization plateaus and frustration are found.
Institute of Solid State Physics - RAS, Russia
Golikova T E obtained her PhD Degree in Physics in 2014 and she is working on experimental investigation of the interplay of superconductivity and magnetism at low temperatures involving structure fabrication with the nanotechnology tools. Her research interest include: superconductivity and magnetism, spintronics, Josephson junctions.
A nonlocal supercurrent was observed in mesoscopic planar SNS Josephson junctions (Al-Cu-Al) with additional normal metal electrodes (Cu). Nonequilibrium quasiparticles were injected from a normal-metal electrode into the left superconducting bank of the Josephson junction in the absence of a net transport current through the junction. The value of nonlocal supercurrent slightly exceeds the local value Ic and depends on the distance between Josephson junction and the injector. The detected voltage in the resistive state in nonlocal configuration has opposite sign. We claim that the observed effect is due to a supercurrent counterflow, appearing to compensate for the quasiparticle flow in the SNS weak link. We have measured the responses of SNS junctions for different distances between the quasiparticle injector and the SNS junction at temperatures far below the superconducting transition temperature. Such a choice of the distance scale between injectors and Josephson junction allows us to exclude coherent CAR and EC effects. The charge-imbalance relaxation length was estimated by using a modified Kadin, Smith, and Skocpol scheme in the case of a planar geometry. The model developed allows us to describe the interplay of charge imbalance and Josephson effects in the nanoscale proximity system in detail at low temperatures (far below the superconducting transition temperature Tc).
National Tsing Hua University, Taiwan
Title: Synthesis of a stable HCP-FCC mixture phase of the high-entropy superalloys Al0.15Co0.18Cr0.12Fe0.11Ni0.36Ti0.08 at high pressure
Time : 14:55-15:20
Chih Ming Lin has his expertise in evaluation and passion in improving the health and wellbeing. Her open and contextual evaluation model based on responsive constructivists creates new pathways for improving healthcare. His research interest include: the physical properties of high-entropy alloys (HEAs) and Topological insulators (TIs) materials under high pressure and the process of synthesis of high-entropy alloys (HEAs) and Topological insulators (TIs) materials.
High-entropy superalloys (HESA), Al0.15Co0.18Cr0.12Fe0.11Ni0.36Ti0.08, non-equimolar solid solutions of six elements, represent a new strategy for the design of materials with properties superior to those of conventional alloys. However, their phase space remains constrained, with transition metal high-entropy alloys containing FCC γ matrix with localized dispersion of L12 γ' particles. Here, we report the high-pressure synthesis of a stable HCP-FCC mixture phase of the prototypical high-entropy superalloys Al0.15Co0.18Cr0.12Fe0.11Ni0.36Ti0.08. This martensitic transformation begins at 0.55 GPa and is attributed to suppression of the local magnetic moments, destabilizing the initial FCC γ structure. However, the behavior of Al0.15Co0.18Cr0.12Fe0.11Ni0.36Ti0.08 is unique in that the HCP phase is retained following decompression to ambient pressure, yielding a stable HCP-FCC mixture phase. This demonstrates a means of tuning the structures and properties of high-entropy superalloys in a manner not achievable by conventional processing techniques.