Session Chair: Guo-En Chang, National Chung-Cheng University
10:30am - 11:00am Invited
Photonic and Plasmonic Semiconductor/Carbon Nanostructure Heterojunction Optoelectronics: Towards Flexible, Low-cost and High Performance
Judy Z. WU
The University of Kansas, United States
Heterojunction nanohybrids of semiconductor and carbon nanostructures (graphene and carbon nanotubes) provide a fascinating platform for exploration of novel photonic and optoelectronic devices. By integrating the advantages of their contituents including superior light-solid interaction and charge mobility, these devices can exhibit high performance surpassing the limit in conventional semiconductors. A key design parameter in these nanohybrid devices is in atomic-scale design and engineering the heterojunction interfaces that play a critical role in controlling the optoelectronic process including photon absorption, exciton dissociation, and charge transfer. In this talk, several examples of nanohybrids with such atomically-engineered heterojunction interfaces will be presented. They include: 1) CNT/biomolecule heterojunctions; 2) photonic quantum dots/graphene and 2D-TMDC/graphene; and 3) plasmonic metal nanoparticle/graphene nanohybrids for photodetection and bio/chemical sensing. We show controlling the interfaces in these photonic and plasmonic nanohybrids is the key to high-performance optoelectronics, which enables a variety of low-cost, flexible dvice applications in photovoltaics, photodetectors, bio/chemical sensors.
The authors acknowledge support in part by NASA contract NNX13AD42A, ARO contract No. W911NF-16-1-0029, and NSF contracts Nos. NSF-DMR-1337737, and NSF-DMR-1508494.
11:00am - 11:30am Invited
Quantum Dots and Quantum Rods for High Quality Displays
Xiao Wei SUN
Southern University of Science and Technology, China
Quantum dots (QDs), quantum rods (QRs), the larger perovskite QDs, and other luminescent nanocrystals (LNCs) have been rapidly developed in both academia and industry due to their outstanding luminescence. Their performance is especially strong in color, and includes highly saturated and pure color (narrow emission), precisely tunable emission wavelengths based on quantum size effects, and high quantum yields, which are beneficial for wide color-gamut display and high-quality (meaning a high color rendering index) lighting. There are two types of QD/QR displays, photoluminescent (PL), in which QDs/QRs are used as backlights for LCDs, and electroluminescent (EL), in which the QDs/QRs are self-emissive through electrical excitation. For PL, the next challenges concerning LNCs for display and lighting industries will probably be around new materials that are more environmentally friendly, with higher quantum yield and even better color saturation (narrower emission) as well as new LNC composites with better long-term operational stabilities. Moreover, some rod-shaped LNCs with strong polarized emissions also have a huge potential to decrease the power consumption of LCD panels. For EL, there are many issues that need to be resolved, such as QD surface modification for EL applications, QD ink for printed displays, balance of carriers’ injection, appropriate hole transport materials, etc. In this talk, we will present our recent researches on extending the lifetime of QDs for on-chip LED packaging and large area assemblying of QRs for polarized emissions.
11:30am - 11:45am Oral
Self-organized Synthesis of Metal-semiconductor Hybrid Nanodot on Insulator Surface
1National Institute of Science Education and Research (NISER) Bhubaneswar, India; 2Inter-University Accelerator Centre, India
Metal and semiconductor nanostructures exhibit multitude of physiochemical properties suitable for a wide variety of novel applications in sensors, catalysis, electronics, photonics, plasmonics, photovoltaics or bioscience. The combination of metal and semiconductor in nanoscale form can be ideal for coupling of their properties towards multifunctional materials. The promising possibilities motivates a quest for large scale single-step synthesis of composite nanostructures. Dewetting of a metal films by ion irradiation is such a self-organized process where a continuous film gradually transform into an array of nanodots on the substrates. This process couples the nanostructure evolution due to dewetting with ion induced mixing and sputtering, opening up a promising route towards self-organized synthesis of composite nanodots on materials surface. Here we show self-organized evolution of Au-Ge composite nanodot array on SiO2 surface under 200-500 keV Xe ion irradiation on Au-Ge bilayer film. The morphology progress through different stages from nucleating patches to extended islands and finally Au-Ge composite nanodot array develops of the insulator surface. While ion energy and fluence determine dimensionality of the nanostructures, existence of a characteristic lateral length scale is also detected at every stage of evolution. Through morphological and compositional analysis, the observed evolution is understood as an effect of ion beam induced dewetting of Au top layer as a result of instantaneous melting along the ion track due to nuclear energy deposition, which combines with sputter erosion of the bilayer film. The generality of the ion induced processes provides a possible route towards metal-semiconductor hybrid nanostructure synthesis on insulator surface.
11:45am - 12:00pm Oral
Self-powered Sensitive and Stable UV-visible Photodetector Based on GdNiO3/Nb-doped SrTiO3 Heterojunctions
Lei CHANG, Le WANG, Junling WANG
Nanyang Technological University, Singapore
Properties of perovskite nickelates are very sensitive to their oxygen content, which allows us to tune their electronic structures by varying the oxygen partial pressure during film deposition. Under the optimized condition, we have obtained GdNiO3 films that are sensitive to a wide spectrum of light. By combining the GdNiO3 film with Nb-doped SrTiO3 to form a heterojunction, we design a self-powered photodetector with high sensitivity toward light with a wavelength between 650 nm and 365 nm. Under 365 nm illumination (50 μW/cm2), the device shows a responsivity of 0.23 A/W at 0 V bias, comparable to or even better than the ultraviolet photodetectors made of semiconductor materials such as GaN or ZnO. The photo-dark ratio can be close to 103 when the power light density reaches 0.6 mW/cm2. Moreover, the device performance is very stable without any decay after 6 months.