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.