Low-dimensional material systems possessing at least one of their dimensions in the nanometer scale offer intriguing physical properties and undiscovered pathways toward revolutionary new device concepts for flexible and transparent electronics, photonics, quantum computing, and other advanced applications. Fabrication of quantum dots, nanowires, ultra-thin films, and heterostructures result in building blocks that reveal a wealth of interesting physical properties including quantum phenomena. Control of synthesis and processing at the nanometer scale offers unprecedented opportunities to tailor microscopic and macroscopic physical properties of such material systems. To further pursue these tremendous opportunities, many fundamental questions need to be addressed and technological barriers need to be overcome. This conference provides a forum for the presentation and discussion of synthesis, processing, and characterization of low-dimensional materials tailored to their unique and peculiar physical properties. Design, fabrication, and characterization of novel device platforms that employ low-dimensional materials are also of interest, as well as interfacing and integration of such devices toward novel electronics, photonics, sensors, and energy conversion and storage.

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Conference 11800

Low-Dimensional Materials and Devices 2021

In person: 2 - 3 August 2021 | Conv. Ctr. Room 7B
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  • Nanoscience + Engineering Plenary Session
  • Nanoscience + Engineering Plenary Networking Event
  • 1: Fabrication of Advanced Nanostructured Materials from Quantum Dots to Thin Films
  • 2: Low-Dimensional Devices and Applications
  • 3: Silicon and III-V Semiconductor Nanowires
  • 4: Optical, Electronic and Thermal Properties of Low-Dimensional Materials
  • Tuesday Smoothies and Cool Jazz Scene
  • Poster Session
Nanoscience + Engineering Plenary Session
In person / Livestream: 2 August 2021 • 8:25 AM - 11:20 AM PDT | Conv. Ctr. Room 6A
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Mark Stockman Tribute (Plenary Presentation)
Author(s): Natalia M. Litchinitser, Duke Univ. (United States); Nikolay I. Zheludev, Optoelectronics Research Ctr. (United Kingdom)
On demand | Presented Live 2 August 2021
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Author(s): P. James Schuck, Columbia Univ. (United States)
On demand | Presented Live 2 August 2021
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Author(s): Teri W. Odom, Northwestern Univ. (United States)
On demand | Presented Live 2 August 2021
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This talk will discuss current advances and future prospects in manipulating light at the nanoscale by plasmonic nanoparticle lattices. These meta-materials support collective hybrid resonances with both light scattering and localization properties. First, we will describe the expanded scope of plasmonic lattices based on exquisite tuning of topological symmetries and nanoparticle materials. Next, we will highlight how the nanoscale cavities combined with quantum emitters show unprecedented nano-lasing properties. Finally, we will discuss how this platform is opening new opportunities in imaging, strong coupling, and photoelectrocatalysis.
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Author(s): Warwick P. Bowen, The Univ. of Queensland (Australia)
On demand | Presented Live 2 August 2021
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State-of-the-art microscopes use intense lasers that can severely disturb biological processes, function and viability. This introduces hard limits on performance that only quantum photon correlations can overcome. In this talk I will report recent work from my laboratory which demonstrates this absolute quantum advantage [1]. We show, specifically, that quantum correlations enable signal-to-noise beyond the photodamage-free capacity of conventional microscopy. Broadly, this represents the first demonstration that quantum correlations can allow sensing beyond the limits introduced by optical intrusion upon the measurement process. We achieve this in a coherent Raman microscope, which we use to image molecular bonds within a cell with both quantum-enhanced contrast and sub-wavelength resolution. This allows the observation of nanoscale biological structures that would otherwise not be resolved. Coherent Raman microscopes allow highly selective biomolecular finger-printing in unlabelled specimens, but photodamage is a major roadblock for many applications. By showing that this roadblock can be overcome, our work provides a path towards order-of-magnitude improvements in both sensitivity and imaging speed.
Nanoscience + Engineering Plenary Networking Event
In person: 2 August 2021 • 11:20 AM - 11:50 AM PDT | Conv. Ctr. Room 6A
Join your colleagues for 30 minutes of networking and discussion after the Nanoscience + Engineering plenary talks.
Session 1: Fabrication of Advanced Nanostructured Materials from Quantum Dots to Thin Films
In person / Livestream: 3 August 2021 • 8:00 AM - 10:10 AM PDT | Conv. Ctr. Room 7B
Session Chairs: Stephanie Law, Univ. of Delaware (United States), Lisa N. McPhillips, Univ. of California, Davis (United States)
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Author(s): Aurelian Marcu, Razvan Ungureanu, Bogdan Calin, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania); Raluca Ianchis, ICHECHIM (Romania); Sevinci Pop, Institutul National de Cercetare-Dezvoltare "Victor Babes" (Romania); Mihai Serbanescu, Gabriel Cojocaru, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania)
On demand | Presented Live 3 August 2021
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In-situ fabrication of (magnetic) iron based nanoparticles is demonstrated using ultrashort laser pulses ablation in liquid medium. Using this in-situ method, thermal effects associated with other similar methods are avoided because of pulse duration much beyond 1 ps, avoiding thermal processes as well as chemical contamination and clustering issues during particle fabrication or transfer steps. Size distribution proved to be dependent on laser beam pulse duration and energy, while their surface (zeta-)potential did not. Monitoring of the cellular viability in the presence of the produced nanoparticles showed an excellent bio-compatibility but with rather limited drug loading capabilities in the absence of any surface functionalization.
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Author(s): Maziar Ghazinejad, Univ. of California, San Diego (United States); Yujia Liu, Univ. of California, Irvine (United States); Edmund Lau, Univ. of California, San Diego (United States); Marc Madou, Univ. of California, Irvine (United States); Dario Mager, Karlsruher Institut für Technologie (Germany)
On demand | Presented Live 3 August 2021
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Understanding how inducing molecular alignment can influence pyrolytic carbon microstructure and functionality is consequential for carbon MEMS microfabrication and applicability. We present a comparative analysis on the effects of compressive stress versus standard tensile treatment of carbon precursors. Different characterization techniques reveal that while subjecting precursor molecules to both types of mechanical stresses will induce graphitization in the pyrolytic carbon, this effect is more pronounced in compressive stress. MEMS functionality of the two carbons was evaluated by characterizing the electrochemical performance of their electrodes. Both carbons exhibited enhanced electrochemical performances. However, the heterogeneous electron transfer rate derived from CV diagrams reveals compression-activated electrode to have remarkably faster kinetics. The results show the versatility of pyrolytic nanocarbons and a synthesis route to tailor functionality for MEMS and Sensors.
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Author(s): Marcell Pálmai, EunByoel Kim, Kyle Tomczak, Univ. of Illinois at Chicago (United States); Xiaoyi Zhang, Argonne National Lab. (United States); Preston T. Snee, Univ. of Illinois at Chicago (United States)
On demand | Presented Live 3 August 2021
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Semiconductor Quantum Dots (QDs) have great potential in applications for renewable energy generation due to their size-tunable redox potentials. QDs may also be doped to manipulate their electronic structure. Our group developed a method to dope each quantum dot with an exact number of guest ions by nucleating the QD around an organometallic seed cluster that contains guest ions. As a result, each QD has the same number of dopants, which eliminates problems due to inhomogeneity of the dot stoichiometry. These materials were studied using time-resolved X-ray absorption spectroscopy, which allows us to characterize the electronic and coordination structure in both the ground and excited states. It was found that, when dopants interact with charge carriers, they may alter their bonding to the underlying matrix. This phenomenon of charge carrier modulation of dopant bonding has a strong effect on the conductivity properties of doped semiconductors.
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Author(s): Cory D. Cress, Samuel W. LaGasse, U.S. Naval Research Lab. (United States)
On demand | Presented Live 3 August 2021
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In this work we will review two post-synthetic methods for controlling defects and doping, in 2D-materials, namely hyperthermal ion implantation (HyTII) and helium ion microscopy (HIM) based processing with a focused He-ion beam. HyTII processing ranges in energy between that of plasma processing and traditional ion implantation, however, it benefits from a monoenergetic beam energy, with precise control over energy, direction, and dose. We will discuss the use of HyTII for forming nitrogen doped graphene along with initial doping studies of transition metal dichalcogenides (TMDs). We have utilized HIM processing to create defects and to nano-machine features in a wide range of TMDs. HIM processing will be correlated with changes in the photoluminescence and Raman spectra of WS2 with dose. To conclude, we will review recent results on HIM processing formation of single photon emitters, particularly in MoS2, and summarize future opportunities in ion-beam processing of 2D materials.
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Author(s): Stephanie Law, Univ. of Delaware (United States)
On demand | Presented Live 3 August 2021
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I will show our results on improving the growth of topological insulator (TI) van der Waals (vdW) thin films using molecular beam epitaxy. First, lattice-matched trivially-insulating buffer layers can be used to reduce the unintentional doing in the films by improving the crystalline quality of the first few TI layers. Second, substrate pre-treatment can reduce twinning and improve TI morphology by satisfying dangling bonds and changing the surface energy. Finally, when TI films are grown on (001) GaAs, the TI film can be grown in an alternate orientation that has an epitaxial relationship to the substrate and that self-assembled TI nano-columns can be grown without the use of strain or catalysts. Despite the weak film-substrate interaction, the morphology and quality of vdW thin films can be strongly controlled by appropriate choice of growth parameters and substrate.
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Author(s): Haifeng Shi, Wenliang Wang, Jiangnan Univ. (China)
On demand
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Author(s): David M. Fryauf, Univ. of California, Santa Cruz (United States); Andrew C. Phillips, Univ. of California Observatories (United States); Nobuhiko P. Kobayashi, Univ. of California, Santa Cruz (United States)
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Various metallic and dielectric thin films are used in silver-based mirrors for astronomical telescopes. The topmost surface of such silver-based mirrors needs to be shielded by a protection coating. Conventionally, the protection coating is deposited at room temperature to minimize thermal stress to which the entire mirror is subjected. Nevertheless, various thin film deposition techniques offer protection coatings with improved characteristics when carried out at elevated temperatures. This paper describes a study of high-performance protected silver-based mirrors annealed at various temperatures in assessing the rationality of introducing post-fabrication annealing with the aim of improving overall optical performance and durability of protected silver-based mirrors.
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Author(s): Jacob H. Sands, Soren A. Tornoe, Sreyes P. Venkatesh, Greyson R. Shoop, Nobuhiko P. Kobayashi, Univ. of California, Santa Cruz (United States)
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Depositing thin films is often limited to a specific deposition process by which precursors are transported in a deposition environment. In other words, a deposition environment in which two deposition processes complementary to each other are unified may offer new insights in designing thin film structures. This view motivated us to combine atomic layer deposition (ALD) and magnetron sputtering (SPU) in a single chamber – sputtering atomic layer augmented deposition (SALAD). The SALAD system offers benefits of consistently delivering precursors in ALD and freely choosing chemical elements in SPU. In this paper, the SALAD system is employed to deposit nanocomposites consisting of multiple layers of aluminum oxide deposited by ALD and copper layers deposited by SPU. Distinctive dispersion features seen in optical properties of the nanocomposites are analyzed to reveal the interrelationship between structural properties and electronic properties of the nanocomposites.
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Author(s): William Bodeau, Univ. of California, Santa Cruz (United States); Kaisei Otoge, Wenchang Yeh, Shimane Univ. (Japan); Nobuhiko P. Kobayashi, Univ. of California, Santa Cruz (United States)
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Lasers are often used to process materials. For example, crystallization of amorphous semiconductor can be induced by having laser light interact with the semiconductor and having amorphous semiconductor undergo a liquid-solid phase transition – laser-induced crystallization. While laser-induced crystallization is predominantly utilized in preparing thin films made of such single chemical elements as silicon and germanium, extending its use for semiconductors that contain multiple chemical elements (e.g., metal oxides) unfolds applications that have yet to be envisioned. In this paper, a continuous-wave laser diode with a micrometer-scale chevron-shaped beam profile – micro-chevron laser beam (μ-CLB) – was exploited to convert amorphous CuO thin films prepared on fused silica substrates into single-crystal Cu2O stripes under various crystallization conditions. The dependence of the crystallization on laser power density and laser scan rate was investigated by Raman spectroscopy and ana
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Author(s): Ana Cros, Saül Garcia-Orrit, Núria Garro, Oleksii Klymov, María José Recio-Carretero, Univ. de València (Spain); Marion Gruart, Univ. Grenoble Alpes (France), CEA-DRF (France); Rémy Vermeersch, Univ. Grenoble Alpes (France); Fabrice Donatini, Univ. Grenoble Alpes (France), Institut NÉEL (France), CNRS (France); Catherine Bougerol, Bruno Gayral, Stéphanie Pouget, Edith Bellet-Amalric, Univ. Grenoble Alpes (France); Nicolas Mollard, Univ. Grenoble Alpes (France), CEA-DRF (France); Hanako Okuno, Jean-Luc Rouviere, Nathaniel Feldberg, Bruno Daudin, Univ. Grenoble Alpes (France)
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The use of van der Waals substrates, in which the epitaxial growth is achieved through weak dipolar interactions, can result in a significant relaxation of the epilayer strain, facilitating at the same time layer detachment. Here, we study the case of GaN layers grown on graphene and muscovite mica. Morphology, surface potential and strain relaxation of GaN are addressed. In the case of graphene, we show it experiences interesting transformations during the growth of GaN, resulting in the intercalation of metal atoms below the graphene layer. In the case of mica, we find that part of the strain accumulated in the GaN layer relaxes by the formation of three-dimensional structures in the shape of telephone cord buckles, straight blisters or by more complex arrangements. Their characteristics are studied in relation to the initial compressive strain and the elastic parameters of the materials.
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Author(s): Sivakumar Vishnuvardhan Mambakkam, Stephanie Law, Univ. of Delaware (United States)
On demand
Session 2: Low-Dimensional Devices and Applications
In person / Livestream: 3 August 2021 • 11:10 AM - 11:50 AM PDT | Conv. Ctr. Room 7B
Session Chairs: Souvik Biswas, Caltech (United States), Lisa N. McPhillips, Univ. of California, Davis (United States)
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Author(s): Judy Zhurun Ji, Wenjing Liu, Univ. of Pennsylvania (United States); Sergiy Krylyuk, National Institute of Standards and Technology (United States); Xiaopeng Fan, Zhifeng Zhang, Univ. of Pennsylvania (United States); Anlian Pan, Hunan Univ. (China); Liang Feng, Univ. of Pennsylvania (United States); Albert Davydov, National Institute of Standards and Technology (United States); Ritesh Agarwal, Univ. of Pennsylvania (United States)
On demand | Presented Live 3 August 2021
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A Weyl semimetal carries topological charges at the Weyl nodes; a light beam can also carry a topological charge, when it has an orbital angular momentum (OAM). Recently there has been a lot of interest in understanding how the spin angular momentum (SAM) of light interacts with materials to induce photocurrents (circular photogalvanic effect, CPGE), but not many studies have focused on photocurrents generated by the OAM of light. Here we report a unique orbital photogalvanic effect (OPGE) in a type-II Weyl semimetal WTe2, featured by a photocurrent winding around the axis of OAM-carrying beams, whose intensity is directly proportional to the topological winding number of the light field, and can be attributed to a discretized dynamical Hall effect. In addition to obtaining evidence of OAM induced electron excitations, our measurements show promise for on-chip detection of the phase of light.
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Author(s): Ahasan Ahamed, Cesar Bartolo-Perez, Ahmed Sulaiman Mayet, Soroush GhandiParsi, Xiangnan Zhou, Julien Bec, Univ. of California, Davis (United States); Nibir K. Dhar, US Army Night Vision and Electronic Sensors Directorate (United States); Ekaterina P. Devine, W&WSens Devices, Inc. (United States); Shih-Yuan Wang, W&Wsens Devices Inc. (United States); Gerard Ariño-Estrada, Laura Marcu, M. Saif Islam, Univ. of California, Davis (United States)
On demand | Presented Live 3 August 2021
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The gain in Avalanche Photodiodes (APDs) and Single Photon Avalanche Diodes (SPADs) is dependent on the probability of photo-generated carriers to trigger an avalanche, which relates to the absorption depth of photons in the photodiode. For silicon photodiodes, the visible wavelength photons are mostly absorbed near the surface where the recombination rate is high. Therefore, they do not contribute significantly to the avalanche multiplication process. By integrating photon-trapping nanoholes, we facilitate deeper penetration of photons into the devices, enhancing light absorption, while a perforated surface reduces device capacitance. This improves the gain-bandwidth of silicon APDs and SPADs significantly. Thus, the manipulation of light penetration depth using photon-trapping nanoholes leads to ultrafast high-gain photodetectors useful for low light applications such as Fluorescent Lifetime Imaging Microscopy (FLIM) and Time-of-Flight Positron Emission Tomography (TOF-PET).
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Author(s): A. Alec Talin, David Ashby, Diana Garland, Sandia National Labs. (United States); Madeline Esposito, Amazon Project Kuiper (United States); Zoey Warecki, Institute for Systems Research, Univ. of Maryland, College Park (United States); George Vizkelethy, Matthew J. Marinella, Sandia National Labs. (United States)
On demand
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Understanding and mitigating the adverse effects of radiation on semiconductor devices remains an active area of research motivated by increased use of electronics in high radiation environments. When a device is exposed to energetic particles, a variety of structural defects are created and then redistributed through diffusion, cluster formation, and recombination. How the defects are distributed in the device can profoundly affect its electrical characteristics, yet methods which can reliably image this distribution are lacking. In the first part of my presentation, I will describe how EBIC in the scanning electron microscope can spatially identify defects produced by a 300 keV He+ beam in model n-MOSFET devices. By analyzing the EBIC signal through the bulk pn-junction and through the gate, radiation damage in the bulk Si or the SiO2 gate can be identified, respectively. Correlation of the defect distribution maps with device electrical characteristics analyzed using Silavaco softwa
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Author(s): Michele Cito, Razvan Baba, David Childs, Univ. of Glasgow (United Kingdom); Brett A. Harrison, National Epitaxy Facility (United Kingdom); A. Watt, Univ. of Sheffield (United Kingdom); Toshikazu Mukai, ROHM Co., Ltd. (Japan); Richard A. Hogg, Univ. of Glasgow (United Kingdom)
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We investigated the difference between a macro scale PL and μPL (excitation and detection area ≤ 5µm2). Low-temperature micro-photoluminescence (μPL) is used to evaluate structural perfection of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTD) structure on different length scales. The thin and highly strained quantum wells (QWs) is subject to monolayer fluctuations in well and barrier thickness that can lead to random fluctuations in their band profile. μPL is performed reducing the laser spot size using a common photolithography mask to reach typical RTD mesa size (a few square microns). We observed that for spot size around 1μm2 the PL line shape present strong differences on multiple points on the wafer. These variations in the PL are investigated by line-shape fitting and discussed regarding variations in long-range disorder brought about by strain relaxation processes.
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Author(s): Foroozan Koushan, Nobuhiko P. Kobayashi, Univ. of California, Santa Cruz (United States)
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There exist a myriad of experimental studies on resistive switching devices that consist of a dielectric film inserted between a pair of electrodes. These resistive switching devices display reversible multi-state switching behaviors pertinent to a range of applications including neuromorphic computing. However, coherent understanding of physical and chemical origins of their distinctive electrical properties has yet to be completed and needs to be further investigated to improve overall performance and endurance of resistive switching devices. In this paper, phase-field methodology was used to study the formation and annihilation of electrically conducting channels in a dielectric film of a resistive switching device. The study focuses on the progressive evolution of domains made of electrical charges – charge clusters – under the influence of spatially varying electric-field and temperature. The study also sheds light on the retention loss – a degradation by which resistive switching
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Author(s): J.P. Hadden, Sam Bishop, Reza Hekmati, Daryl Beggs, Cardiff Univ. (United Kingdom); Robert Taylor, Univ. of Oxford (United Kingdom); Wolfgang W. Langbein, Anthony J. Bennett, Cardiff Univ. (United Kingdom)
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We present our recent research on color centers in Aluminum Gallium Nitride which emit single photons up to room temperature. The mature processing technology which is available for group-III-nitrides and the host material’s optical transparency in the visible and infra-red opens up the possibility of novel applications in nanophotonics and quantum devices. We are working to create suspended photonic devices, including waveguides and photonic crystal cavities, which we will show can guide and enhance the color center emission.
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Author(s): Maria Losurdo, Yael Gutierrez Vela, Istituto di Nanotecnologia (Italy); Fernando Moreno, Univ. de Cantabria (Spain); Mircea Modreanu, Tyndall National Institute (Ireland); Marin Gheorghe, NANOM MEMS SRL (Romania); Guy Garry, OLGA ishchenko, TE-OX (France); Jordi Soler, TIGERS JONUZI, VLC Photonics S.L. (Spain); Christoph Cobet, Johannes Kepler Univ. Linz (Austria); Wolfram Pernice, Westfälische Wilhelms-Univ. Münster (Germany)
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Realizing optically and/or electrically tunable plasmonic resonances in the visible to ultraviolet (UV) spectral region is particularly important for reconfigurable photonic device applications. Ultrathin layered group-III chalcogenides, such as GaS, GaSe, GaTe, Sb2S3, are particularly intriguing 2D materials that are revealing exotic phase-change properties with great promise for application in next generation reconfigurable electronics and optoelectronic devices. In this contribution, we present experimental and calculated results obtained on low-loss layered phase-change semiconducting materials of GaS, GaSe, GaTe, Sb2S3, which shows in addition to the conventional amorphous to crystalline phase transition (like the GST family), order-order (polytypes), metal-to-insulator transitions that can be triggered electrically, optically and via plasmonic coupling with alternative phase-change plasmonic metals.
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Author(s): Shawana Tabassum, The Univ. of Texas at Tyler (United States)
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We are developing a wearable sensing platform that provides rapid and quantitative measurements of a panel of inflammatory biomarkers. The sensor detects interleukin-6 (IL-6) and C-reactive protein (CRP) levels, which are found to be associated with adverse clinical outcomes and death in critically ill SARS-CoV-2 patients. Although wearable technology has entered the fight against COVID-19, the devices are limited to monitoring physical attributes and rely on syndromic case finding. Hence, asymptomatic but contagious individuals with no early symptoms remain undetected and transmit the virus/bacteria. In this regard, our sensor would result in a powerful public health weapon that will monitor biochemical attributes in real-time and diagnose an infection before symptoms appear.
Session 3: Silicon and III-V Semiconductor Nanowires
In person / Livestream: 3 August 2021 • 11:50 AM - 12:10 PM PDT | Conv. Ctr. Room 7B
Session Chairs: Souvik Biswas, Caltech (United States), Lisa N. McPhillips, Univ. of California, Davis (United States)
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Author(s): Hieu Pham Trung Nguyen, Barsha Jain, Ravi Teja Velpula, Moulik Patel, New Jersey Institute of Technology (United States)
On demand | Presented Live 3 August 2021
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We report on the achievement of a new type of ultraviolet light-emitting diodes (LEDs) using AlInN nanowire heterostructures. The molecular beam epitaxial grown AlInN nanowires have relatively high internal quantum efficiency of > 52% at 295nm. The peak emission wavelength is in the range of 280 - 355nm. Moreover, we show that the light extraction efficiency of AlInN nanowire LEDs could reach ~ 63% for hexagonal photonic crystal nanowire structures which is significantly higher compared to the random nanowire arrays. This study provides significant insights into the design and fabrication of new type of high performance AlInN nanowire ultraviolet light-emitters.
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Author(s): Vladislav Khayrudinov, Aalto Univ. (Finland); Kacper Grodecki, Institute of Applied Physics, Wojskowa Akademia Techniczna im. Jaroslawa Dabrowskiego (Poland); Tomi Koskinen, Aalto Univ. (Finland); Malgorzata Kopytko, Krzysztof Murawski, Institute of Applied Physics, Wojskowa Akademia Techniczna im. Jaroslawa Dabrowskiego (Poland); Lide Yao, Aalto Univ. (Finland); Hua Jiang, Ilkka Tittonen, Aalto University (Finland); Harri Lipsanen, Aalto Univ. (Finland); Tuomas Haggren, The Australian National Univ. (Australia)
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Semiconductor nanowires are routinely grown on high-priced crystalline substrates as it is extremely challenging to grow directly on plastics and flexible substrates due to high temperature requirements and substrate preparation. At the same time, plastic substrates can offer many advantages such as extremely low price, light weight, mechanical flexibility, shock and thermal resistance, and biocompatibility. We explore the direct growth of InSb nanowires on flexible plastic substrates by metal-organic vapor phase epitaxy (MOVPE). We synthesize InSb nanowires on polyimide and show that the fabricated NWs are optically active with strong light emission even at RT. Overall, we demonstrate that InSb nanowires can be synthesized directly on flexible plastic substrates inside a MOVPE reactor, and we believe that our results will further advance the development of the nanowire-based flexible electronic devices.
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Author(s): Paola Prete, Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche (Italy); Daniel Wolf, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden (Germany); Nico Lovergine, Univ. del Salento (Italy)
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III–V semiconductor nanowires (NWs) offer significant applications as novel photonic/photovoltaic nanodevices. Nano-spectroscopic/structural studies of MOVPE-grown GaAs-AlGaAs core-shell and core-multishell NWs forming quantum well tubes (QWTs) are here reviewed. Cathodoluminescence (CL) spectroscopic imaging combined with scanning transmission electron microscopy (STEM) tomography allowed robust correlation between QWT emission and nanoscale inner structure. GaAs QWT thickness were determined from NW diameters by a multishell growth model upon validation against experimental data (core diameter and shell thickness) obtained from 3D reconstructed STEM tomograms of QWT NWs. CL mapping evidenced nanoscale localization of QWT exciton emissions along NW axis demonstrating that their emission is affected by carrier localization at QWT inhomogeneity. In-depth understanding of luminescence-structure relationships thus achieved will foster future applications of such NWs as efficient nanolaser
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Author(s): Antonio Alessio Leonardi, Maria Josè Lo Faro, Dario Morganti, Univ. degli Studi di Catania (Italy); Barbara Fazio, Istituto per i Processi Chimico Fisici, Consiglio Nazionale delle Ricerche (Italy); Paolo Musumeci, Univ. degli Studi di Catania (Italy); Maria Miritello, Istituto per la Microelettronica e Microsistemi (Italy); Giorgia Franzò, Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche (Italy); Francesco Nastasi, Fausto Puntoriero, University of Messina (Italy); Cinzia Di Pietro, Francesco Priolo, Univ. degli Studi di Catania (Italy); Alessia Irrera, Istituto per i Processi Chimico Fisici, Consiglio Nazionale delle Ricerche (Italy)
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A fractal array of room-temperature (RT) luminescent Si NWs is realized by metal-assisted chemical etching a cheap, fast, and maskless Si technology compatible approach. Several photonics and sensing application will be shown. For what concern photonics, the fabrication of artificial fractal based on the Er:Y2O3 decoration of Si NWs is reported, as well as first antenna based on the energy transfer between Si NWs and dye with efficiency in the 86-93% range. An innovative sensor class based on the PL at RT of Si NWs is presented showing a platform for ultralow quantification and further analysis of small extracellular vesicles(sEVs).
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Author(s): Ruqaiya Al-Abri, The Univ. of Manchester (United Kingdom); Sudhakar Sivakumar, Martin Magnusson, Lund Univ. (Sweden); Patrick Parkinson, The Univ. of Manchester (United Kingdom)
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Controllable doping in semiconductor nanowires is essential for development of optoelectronic devices. Despite great progress, a fundamental challenge remains in controlling the uniformity of doping, particularly in the presence of relatively high levels of geometrical inhomogeneity in bottom-up growth. A relatively high doping level of 1E18 cm-3 corresponds to just ~1000 activated dopants in a 2µm long, 50nm diameter nanowire. High-throughput photoluminescence spectroscopy enables the collection of doping distributions across many (>10k) nanowires, but geometric variation adds additional uncertainty to the modelling. We present an approach that uses large datasets of doping and emission intensity to infer both doping and diameter across a growth, and apply Bayesian methods to study the underlying distributions in Zn-doped aerotaxy-grown GaAs nanowires. This new big-data enabled approach provides a route to exploit inherent inhomogeneity to reveal fundamental recombination mechanisms.
Session 4: Optical, Electronic and Thermal Properties of Low-Dimensional Materials
In person / Livestream: 3 August 2021 • 1:40 PM - 3:00 PM PDT | Conv. Ctr. Room 7B
Session Chairs: Maziar Ghazinejad, Univ. of California, San Diego (United States), Ahasan Ahamed, Univ. of California, Davis (United States)
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Author(s): Alexander A. Balandin, Univ of California Riverside (United States)
On demand | Presented Live 3 August 2021
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In this keynote talk, I will describe the properties and device applications of quasi-2D and quasi- 1D quantum van der Waals (vdW) materials. The 2D vdW materials include TMDs, which exfoliate into quasi-2D atomic layers. The focus will be on 1T-TaS2, a unique material with charge-density-wave (CDW) phases observed above room temperature. The 1D vdW materials include members of the TMT family, which exfoliate into quasi-1D atomic threads. I will discuss switching among various CDW phases and possibilities of their device applications; the use of the current fluctuations for observing phase transitions; and current carrying capacity of TaSe3 atomic bundles.
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Author(s): Souvik Biswas, Caltech (United States); Zakaria Y. Al Balushi, Univ. of California, Berkeley (United States); Joeson Wong, Caltech (United States); Eoin Caffrey, Trinity College Dublin (Ireland); Sergiy Krylyuk, National Institute of Standards and Technology (United States); Pin Chieh Wu, National Cheng Kung Univ. (Taiwan); Hamidreza Akbari, Caltech (United States); Takashi Taniguchi, Kenji Watanabe, National Institute for Materials Science (Japan); Albert Davydov, National Institute of Standards and Technology (United States); Harry A. Atwater, Caltech (United States)
On demand | Presented Live 3 August 2021
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Non-hydrogenic Rydberg series associated with excitons have been identified in ultraclean monolayer TMDCs. Here, we investigated the radiative properties of the excitonic Rydberg series in monolayer MoTe2 based devices and the influence of Fermi level position on the same. Using low temperature (4K) photoluminescence measurements, we observed bright emission from the first three states of the excitonic Rydberg series, namely A1s, 2s and 3s. Upon doping on either electron or hole side, oscillator strengths are rapidly transferred to the corresponding trion (charged exciton/attractive polaron) states associated with the aforementioned neutral excitonic resonances. Energy shifts between different states are observed as a function of gate voltage, indicating strong band-structure renormalization. Our work identifies MoTe2 as a novel platform to realize highly tunable bright light sources or electro-optic modulators in the NIR.
11800-36
Author(s): Brenden A. Magill, Giti Khodaparast, Virginia Polytechnic Institute and State Univ. (United States); Kai Wang, Tao Ye, The Pennsylvania State Univ. (United States); Carlos G. Garcia, National High Magnetic Field Lab. (United States), Florida State Univ. (United States); Stephen A. McGill, National High Magnetic Field Lab. (United States), Florida State Univ. (United States); Shashank Priya, The Pennsylvania State Univ. (United States)
On demand | Presented Live 3 August 2021
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In this work we present PL and time resolved PL (TRPL) measurements of three of these materials: BA2PbI4, BA2MA1Pb2I7, and BA2CuCI4 where BA2 represents (CH3(CH2)3NH3)2, and MA: CH3NH3. Both BA2PbI4 and BA2CuCI4 have a single layer of perovskite material separated by an organic cation layer while BA2MA1Pb2I7 has two atomic layers of perovskite. Our observations indicate the existence of both free and trapped excitons in these systems. Additionally, BA2PbI4 displays two sets of peaks for both trapped and free excitons that evolve with temperature, indicating that as the temperature is reduced the system begins, but does not complete, a phase change from a tetragonal to an orthorhombic crystal lattice. Our result provides new insights on the low temperature behavior of this phase transition, as well as exploring the exciton spectra as a function of both temperature and magnetic field. This material is based upon work supported by the Air Force Office of Scientific Research under awar
11800-29
Author(s): Ryan Wilmington, Hossein Ardekani, North Carolina State Univ. (United States); Avinash Rustagi, Purdue Univ. (United States); Alexander Bataller, Alexander F. Kemper, North Carolina State Univ. (United States); Robert A. Younts, NIWC Atlantic (United States); Kenan Gundogdu, North Carolina State Univ. (United States)
On demand
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Recent theoretical and experimental work on monolayer transition-metal dichalcogenides show that optical excitation and strain leads to a transition from an excitonic to electron-hole liquid (EHL) phase. This phase transition is accompanied by a huge (23-fold) increase in photoluminescence (PL) but so far a mechanism has not been confirmed. Here, authors investigate how dark excitons beyond the light cone may influence the PL response of 1L-MoS2 in the excitonic vs EHL regime. They predict that in the excitonic to plasma transition, intraband collisions redefine the effective light cone of optically accessible carriers. Also, sample strain is shown to impact the spectral positions of bright and dark exciton transitions by way of altering the momentum space band positions of 1L-MoS2, increasing the ratio of bright carriers within the light cone.
11800-7
Author(s): Peter R. Stevenson, Robert T. Busch, Ali Jawaid, Richard A. Vaia, W. Joshua Kennedy, Jonathan P. Vernon, Air Force Research Lab. (United States)
On demand
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Two-Dimensional (2D) monolayer transition metal dichalcogenides (TMDs) enable distinct quantum optical properties compared to bulk analogs. The pervasive appeal of 2D TMDs is underpinned by the nascent ability to scalably isolate mono to few layer TMDs from bulk constituents via exfoliation strategies. To-date, the optical characterization of films from exfoliated TMDs has been scarce, especially in relation to the quality of the optical response (i.e., refractive index, n, and extinction coefficient, k) and associated physical material tolerances. In this work, we report the optical properties of representative liquid phase exfoliated MoS2 films and identify important considerations toward maximizing associated low-dimensional optical performance. Understanding processing impact on material quality post-exfoliation and on the resulting optical performance of such films is expected to further enable application-ready quantum nanophotonic technologies.
11800-12
Author(s): Sonia Conesa-Boj, Technische Univ. Delft (Netherlands)
On demand
11800-16
Author(s): Abel Brokkelkamp, Isabel Postmes, Technische Univ. Delft (Netherlands); Sergiy Krylyuk, National Institute of Standards and Technology (United States); Jaco ter Hoeven, VU Amsterdam (Netherlands); Laurien Roest, Technische Univ. Delft (Netherlands); Juan Rojo, VU Amsterdam (Netherlands); Albert Davydov, National Institute of Standards and Technology (United States); Sonia Conesa-Boj, Technische Univ. Delft (Netherlands)
On demand
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Indium Selenide (InSe) is a remarkable two-dimensional quantum material whose characteristic properties include a bandgap in the near infrared region that increases with fewer layers. InSe is known to crystallize in either the β-, γ- or the ε-phase. Of these three crystalline phases, only the β and γ exhibit a direct bandgap, which makes them suitable for optoelectronic applications. The β-phase is easily distinguished from the others by means of Transmission Electron Microscopy (TEM), whereas the γ- and ε-phases appear very similar. We determine the crystalline phase present in these InSe specimens by systematic investigation with High Resolution TEM. We further assess the local electronic properties using Electron Energy-Loss Spectroscopy (EELS) by mapping relevant features in the spectra. Finally, we deploy Machine Learning techniques for a model-independent subtraction of the Zero Loss Peak, making it possible to identify features in the ultra-low-loss region of the EELS spectra.
11800-33
Author(s): Juan P. Martinez-Pastor, Hamid Pashaei Adl, Setatira Gorji, Juan Navarro-Arenas, Guillermo Muñoz-Matutano, Isaac Suárez, Vladimir S. Chirvony, Univ. de Valencia (Spain); Andrés F. Gualdrón-Reyes, Iván Mora-Seró, University Jaume I (Spain)
On demand
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Metal halide perovskites in the form of nanocrystals are excellent light emitters at visible wavelengths. In this talk, the optical properties of single nanocrystals and ensembles will be discussed, as also several applications in nanophotonics as Mie resonators and hyperbolic metamaterials. For these applications, specially at room temperature, it is important to know the limitations derived from the exciton recombination dynamics, in which shallow non-quenching traps has an important role. At low temperatures, single nanocrystals can behave as single photon emitters if blinking and spectral diffusion is conveniently reduced. Furthermore, the coupling of excitons to the optical modes of hyperbolic metal-dielectric metamaterials (HMMs) will induce an important increase of their radiative emission rate up to four times by Purcell effect.
11800-40
Author(s): Diego C. Lopez, Douglas A. A. Ohlberg, Univ. Federal de Minas Gerais (Brazil); Brian Giraldo, Univ. of California, Santa Cruz (United States); Jhonattan C. Ramirez, Univ. Federal de Minas Gerais (Brazil); Nobuhiko P. Kobayashi, Univ. of California, Santa Cruz (United States); Cássio G. Rego, Gilberto Medeiros-Ribeiro, Univ. Federal de Minas Gerais (Brazil)
On demand
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Utilizing microwaves in the near field regime has been an exciting topic in the field of high-resolution microscopy. Recently, we were able to demonstrate 1 nm resolution using scanning Microwave Impedance Microscopy (sMIM) where a spontaneously forming water meniscus concentrated the microwave fields in small regions. Here we combine sMIM with Finite Element modeling (FEM) to investigate structures comprised of alternate layers of metals and dielectrics. sMIM measurements provide information on both real and imaginary parts of the reflected microwave signal, which can be associated with the local conductivity and permittivity. Yet, these quantities can be influenced by the local topography, so extraction of the electronic contribution is a challenge. Here we perform tip-surface distance scans in order to gain a better understanding of the substrate response and compare with the FEM results.
Tuesday Smoothies and Cool Jazz Scene
In person: 3 August 2021 • 3:00 PM - 4:00 PM PDT | Conv. Ctr. Sails Pavilion, Exhibition Hall Coffee Area
Cool off with a smoothie while you network with other conference goers and chill with a smooth Jazz trio.
Poster Session
In person: 3 August 2021 • 5:30 PM - 7:00 PM PDT | Conv. Ctr. Sails Pavilion, City Trellis Entrance
11800-32
Author(s): Mirsaeid Sarollahi, Rohith Allaparthi, Reem Alhelais, Manal Aldawsari, Malak A. Refaei, Md Helal Uddin Maruf, Morgan E. Ware, Univ. of Arkansas (United States)
On demand | Presented Live 3 August 2021
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The optical properties of periodic graded GaN/InGaN are studied. We have designed graded InGaN quantum well (QW) structures with the indium composition increasing then decreasing in a zigzag pattern. Through polarization doping, this naturally creates alternating p-type and n-type regions. Separate structures are designed by varying the number of repeating periods (1 to 3), while maintaining constant overall structure thicknesses. Calculation of the transition probabilities and the electron and hole wave-functions between the conduction band and the valence band reveals a complex energy structure which predicts the photoluminescence peaks for band to band transitions.
11800-5
Author(s): Sanghyeok Park, Dongha Kim, Yun-Seok Choi, Min-Kyo Seo, KAIST (Korea, Republic of)
On demand
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Owing to the Purcell effect, optical micro-structures can control the radiative decay of the quantum emitters in transition metal dichalcogenide (TMDC) media. However, conventional optical micro-structures change the local density of optical states (LDOS) not only at the photoluminescence (PL) wavelength of the TMDC quantum emitters and but also at the pump wavelength simultaneously and thus cause an inevitable influence on the excitation conditions. We propose and experimentally demonstrate a reflective metallic metasurface for independently engineering the excitation and radiation of quantum emitters in the TMDC monolayer.
11800-9
Author(s): Raveesh Gourishetty, Subhananda Chakrabarti, Indian Institute of Technology Bombay (India)
On demand
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The usage of the capping layer on InAs/GaAs quantum dots (QDs) to improve the optical and the structural characteristics has been a common practice from decades. GaAsN capping layer with varying nitride composition is used to analyze its effects on the emission wavelength, band structure and the strain build up in a ten-layer InAs/GaAs SK QDs that are electronically coupled to six stack SML QDs. A redshift in the PL emission wavelength from ~1072 nm to ~1184 nm has been witnessed with increase in the nitride composition. We conclude that the redshift in the PL emission wavelength is due to the reduction in the conduction band energy level in the GaAsN capping layer with respect to GaAs layer that reduces the electron confinement in QDs. The GaAsN capping offering a strong red shift of ~1184 nm with minimum strain for coupled QD system can further be used in the optoelectronic device studies.
11800-11
Author(s): Samishta Choudhary, Ravindra Kumar, Subhananda Chakrabarti, Indian Institute of Technology Bombay (India)
On demand
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A theoretical investigation of optical and structural properties of heterogeneously coupled SK on SML QDs heterostructure with In0.18Ga0.82AsYSb1-Y capping on InAs SK QD has been done. Variation of Sb composition was taken as 10, 15, 20 and 25%. Higher Sb composition contributes in transition from type I to type II which, can be discovered in positions of probability density function for electron and holes and from energy band illustrations. The biaxial strain distribution in SK QD increases with increasing Sb composition while, the hydrostatic strain decreases with increasing Sb composition. PL emission wavelength have been observed from ground state energy levels.
11800-17
Author(s): Madhuri Mishra, Sushama Sushama, Indian Institute of Technology Bombay (India); Sushil K. Pandey, National Institute of Technology, Karnataka, Surathkal (India); Subhananda Chakrabarti, Indian Institute of Technology Bombay (India)
On demand
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We report the phosphorus doping in ZnO lattice using Spin-on Dopant technique. The study of optical, elemental and structure properties has been carried out on different samples in order to see doping effect. The PL peaks around 3.31eV and 3.35eV correspond to FA and AX° were found in photoluminescence spectra of doped and annealed ZnO samples. XPS spectra of samples show the shifting of 2p peak at higher energy values after annealing indicates strengthening of P-O bond. This study shows the SOD process is a low cost, less destructive and an efficient way to dope ZnO thin film.
11800-23
Author(s): Madhuri Mishra, Sushama Sushama, Indian Institute of Technology Bombay (India); Sushil K. Pandey, National Institute of Technology, Karnataka, Surathkal (India); Subhananda Chakrabarti, Indian Institute of Technology Bombay (India)
On demand
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We report the effect of phosphorus doping on structural, elemental and optical properties of ZnMgO film using Spin-on Dopant technique. The samples A, B, and C has been prepared as undoped, doped and annealed at 700°C respectively. In XRD (002) plane appeared around 34.173° for sample A and at higher angle for other samples corresponds to doping in film. The XPS and photoluminescence measurement confirmed the presence of phosphorus atoms as p-type dopant in ZnMgO lattice.
11800-28
Author(s): Saranya Reddy Shriram, Subhananda Chakrabarti, Indian Institute of Technology Bombay (India)
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Our findings on the incorporation of small amounts of nitrogen (N) on the effect of strain and electron confinement in a 6-stack InAs SML QDs have been studied. We did 8-band k.p model simulations on 2 ML thick GaAs1-xNx capping layer (CL) with varying nitride (N) contents (x:1.5, 1.8, 2.2, 2.5%). We have observed a reduction in electron carrier confinement and hence PL redshift (0.96 eV) with the addition of such dil. nitride (<2.2%). The tensile nature of GaAsN CL produced strain relief in the system pertaining to improved structural properties such as dot size uniformity, suitable for laser device applications.
Conference Chair
Univ. of California, Santa Cruz (United States)
Conference Chair
A. Alec Talin
Sandia National Labs. (United States)
Conference Chair
National Institute of Standards and Technology (United States)
Conference Co-Chair
Univ. of California, Davis (United States)
Program Committee
Deji Akinwande
The Univ. of Texas at Austin (United States)
Program Committee
Kristine A. Bertness
National Institute of Standards and Technology (United States)
Program Committee
Sonia Conesa-Boj
Technische Univ. Delft (Netherlands)
Program Committee
Institute for Energy Technology (Norway)
Program Committee
HORIBA Scientific (United States)
Program Committee
Univ. of Maryland, College Park (United States)
Program Committee
Istituto per la Microelettronica e Microsistemi (Italy)
Program Committee
The George Washington Univ. (United States)
Program Committee
Sandia National Labs. (United States)
Program Committee
Technical Univ. of Denmark (Denmark)