Physical Sciences and Mathematics Commons^™

Formulation Of Causality-Preserving Quantum Time Of Arrival Theory, Denny Lane B. Sombillo, Neris I. Sombillo

Physics Faculty Publications

We revisit the quantum correction to the classical time of arrival to address the unphysical instantaneous arrival in the limit of zero initial momentum. In this study, we show that the vanishing of arrival time is due to the contamination of the causality-violating component of the initial wave packet. Motivated by this observation, we propose to update the temporal collapse mechanism in Galapon (2009) [18] to incorporate the removal of causality-violating spectra of the arrival time operator. We found that the quantum correction to the classical arrival time is still observed. Thus, our analysis validates that the correction is an …

Concept Connectivity: An Educational And Research Framework For Scientific Learning In Optics, Photonics, And Electronic Education, Benjamin Dingel, John Gabriel C. Rivera, Francesca De Guzman Palabrica, Clint Dominic Bennett

Physics Faculty Publications

We present a novel framework referred to as Concept Connectivity that aids in educating and engaging students by presenting the topic of the Special Theory of Relativity (STR) in a coherent and unified manner. It uses different analogue implementations of the STR coming from seemingly distinct fields of study such as (i) Optics, (ii) Photonics, and (iii) Electronics to connect not only to the concepts of the STR but to the various concepts from these different fields. In these analogue implementations, the fundamental characteristics of the different STR phenomena can be mimicked in many different ways. Concept Connectivity has two …

Microstructural Characterizations And Strength Development Of Self-Compacting Concrete Using Rice Husk Ash, Floyd Rey P. Plando, Joel T. Maquiling

Physics Faculty Publications

The conversion of waste and by-products into green building materials is gaining attention for a sustainable economy. Particularly, rice husk ash (RHA) is used as a precursor in self-compacting concrete due to its high pozzolanic activity. It also minimizes the use of conventional OPC as a primary binder during construction by exploiting its chemical features and characteristics as an alternative binding agent. Developing and mass-producing RHA as a cementitious material would lessen the carbon footprint that harms the environment. This study presents the compressive strength and microstructural characterizations of rice husk ash-based self-compacting concrete (RHA-SCC). The scanning electron microscope was …

Smartphone-Based Approach To Demonstrating Relativistic Aberration Of Light Using Electronic Circuit Analogues For Undergraduates In The Philippines, Samuel Martirez, June Capin, Shayne Venancio, Perine Bianzon, John Gabriel Rivera, Benjamin Dingel, Clint Dominic Bennett

Physics Faculty Publications

Previously, we demonstrated an electronic circuit analogue of one of Special Relativity's (SR) phenomena called the Relativistic Aberration of Light (RAL) (European Journal of Physics, 42, 015605, 2021), which describes the change in the angle an observer sees a light source relative to their direction of motion at relativistic speeds. It used typical bulky laboratory equipment such as (i) function generators, (ii) oscilloscopes, and (iii) power supplies together with our all-pass filter (APF)-based electronic circuit analogue to perform experiments. In this paper, we present a novel smartphone-based experimental set-up performing the same experiment, but we replace the bulky and expensive …

Research Priorities Of Applying Low-Cost Pm2.5 Sensors In Southeast Asian Countries, Shih-Chun Candice Lung, To Thi Hien, Maria Obiminda L. Cambaliza, Ohnmar May Tin Hlaing, Nguyen Thi Kim Oanh, Mohd Talib Latif, Puji Lestari, Abdus Salam, Shih-Yu Lee, Wen-Cheng Vincent Wang

Physics Faculty Publications

The low-cost and easy-to-use nature of rapidly developed PM2.5 sensors provide an opportunity to bring breakthroughs in PM2.5 research to resource-limited countries in Southeast Asia (SEA). This review provides an evaluation of the currently available literature and identifies research priorities in applying low-cost sensors (LCS) in PM2.5 environmental and health research in SEA. The research priority is an outcome of a series of participatory workshops under the umbrella of the International Global Atmospheric Chemistry Project–Monsoon Asia and Oceania Networking Group (IGAC–MANGO). A literature review and research prioritization are conducted with a transdisciplinary perspective of providing useful scientific evidence in assisting …

Application Of Image Processing Programs In Color Analysis Of Wood Photodegradation, Gabriel Joseph D. Plata, Ramon M. Delos Santos

Physics Faculty Publications

In general, polymer photodegradation is an important aspect of polymer science that is of great interest to chemistry, materials science, biology, and physics students who engage in this field of research. Wood consists of three main polymers, which makes it a good candidate for such photodegradation studies. Aside from structural changes based on chemical analysis, color change assessment can also be employed to check any extent of degradation on wood without the need for sophisticated analytical equipment. This study presents the application of two image processing programs in color analysis of wood photodegradation: ImageJ and Colormath library, which are Java-based …

Influence Of Boreal Summer Intraseasonal Oscillation On Rainfall Extremes In The Philippines, Lyndon Mark P. Olaguera, John A. Manalo, Jun Matsumoto

Physics Faculty Publications

This study investigates the impact of the northward/northwestward propagating 30–60-day mode of the boreal summer intraseasonal oscillation (BSISO) on the extreme rainfall events in the Philippines during the June–September (JJAS) season from 1979 to 2018. The Philippines domain is divided into the three latitudinal regions: Luzon region (13°–22°N), Visayas region (10°–13°N), and Mindanao region (5°–10°N) to account for the regional differences in the timing of extreme rainfall events. The probability density functions of JJAS rainfall are skewed towards higher values relative to the non-BSISO days in BSISO Phases 6–8, Phases 5–7, and Phases 4–6 over the Luzon, Visayas, and Mindanao …

Improvised Centrifugal Spinning For The Production Of Polystyrene Microfibers From Waste Expanded Polystyrene Foam And Its Potential Application For Oil Adsorption, Marco Laurence M. Budlayan, Jonathan N. Patricio, Jeanne Phyre B. Lagare, Susan D. Arco, Arnold C. Alguno, Antonio M. Basilio, Felmer S. Latayada, Rey Y. Capangpangan

Physics Faculty Publications

A straightforward approach to recycle waste expanded polystyrene (EPS) foam to produce polystyrene (PS) microfibers using the improvised centrifugal spinning technique is demonstrated in this work. A typical benchtop centrifuge was improvised and used as a centrifugal spinning device. The obtained PS microfibers were characterized for their potential application for oil adsorption. Fourier transform infrared spectroscopy results revealed similarity on the transmission bands of EPS foam and PS microfibers suggesting the preservation of the EPS foam’s chemical composition after the centrifugal spinning process. Scanning electron microscopy displayed well-defined fibers with an average diameter of 3.14 ± 0.59 μm. At the …

Particulate Oxalate-To-Sulfate Ratio As An Aqueous Processing Marker: Similarity Across Field Campaigns And Limitations, Miguel Ricardo A. Hilario, Ewan Crosbie, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Maria Obiminda L. Cambaliza, Andrea F. Corral, Melliza Templonuevo Cruz, Jackie E. Dibb, Genevieve Rose Lorenzo, Alexander B. Macdonald, Claire E. Robinson, Michael Shook, James Bernard Simpas, Connor Stahl, Edward Winstead, Luke Ziemba, Armin Sorooshian

Physics Faculty Publications

Leveraging aerosol data from multiple airborne and surface-based field campaigns encompassing diverse environmental conditions, we calculate statistics of the oxalate-sulfate mass ratio (median: 0.0217; 95% confidence interval: 0.0154 – 0.0296; R = 0.76; N = 2948). Ground-based measurements of the oxalate-sulfate ratio fall within our 95% confidence interval, suggesting the range is robust within the mixed layer for the submicrometer particle size range. We demonstrate that dust and biomass burning emissions can separately bias this ratio towards higher values by at least one order of magnitude. In the absence of these confounding factors, the 95% confidence interval of the ratio …

Total Organic Carbon And The Contribution From Speciated Organics In Cloud Water: Airborne Data Analysis From The Camp2ex Field Campaign, Connor Stahl, Ewan Crosbie, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Zenn Marie Cainglet, Maria Obiminda L. Cambaliza, Melliza Templonuevo Cruz, Julie Mae Dado, Miguel Ricardo Hilario, Gabrielle Leung, Alexander B. Macdonald, Angela Monina T. Magnaye, Jeffrey S. Reid, Claire E. Robinson, Michael Shook, James Bernard Simpas, Shane Marie Visaga, Edward Winstead, Luke Ziemba, Armin Sorooshian

Physics Faculty Publications

This work focuses on total organic carbon (TOC) and contributing species in cloud water over Southeast Asia using a rare airborne dataset collected during NASA’s Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex), in which a wide variety of maritime clouds were studied, including cumulus congestus, altocumulus, altostratus, and cumulus. Knowledge of TOC masses and their contributing species is needed for improved modeling of cloud processing of organics and to understand how aerosols and gases impact and are impacted by clouds. This work relies on 159 samples collected with an axial cyclone cloudwater collector at altitudes of 0.2–6.8 km that …

Publication-Driven Research Experience For Undergraduates (Reu) Program In Optics And Photonics In The Philippines Using Circuit Analogue-Based Research Experiments, Benjamin Dingel, Clint Dominic Bennett

Physics Faculty Publications

We summarize a unique publication-driven Research Experience for Undergraduates program in optics/photonics that uses electronic circuit analogue-based research to strengthen students’ engagement in research. At present, we have published 4 journal and conference papers.

Synoptic Conditions And Potential Causes Of The Extreme Heavy Rainfall Event Of January 2009 Over Mindanao Island, Philippines, Lyndon Mark P. Olaguera, Michelle Español Caballar, Joseph Cabacungan De Mata, Loida Ann Torres Dagami, Jun Matsumoto, Hisayuki Kubota

Physics Faculty Publications

This study investigates the synoptic conditions that led to the heavy rainfall/flood (HRF) event in Mindanao Island, Philippines (122 −127°E; 5 −10°N), on January 2009 (JAN2009 HRF) that are less emphasized in previous works. Extensive flooding was reported over Cagayan de Oro City in the northern part of Mindanao, where the rainfall on January 10, 11, and 13, 2009, exceeded the 99th percentile of daily rainfall records of all January of the city from 1979 to 2017 by almost two times. A similar exceedance was also felt in Hinatuan station over the eastern coast of Mindanao Island on January 15, …

The Effect Of Urbanization On Temperature Indices In The Philippines, John A. Manalo, Jun Matsumoto, Hiroshi G. Takahashi, Marcelino Q. Villafuerte Ii, Lyndon Mark P. Olaguera, Guoyu Ren, Thelma Cinco

Physics Faculty Publications

This paper presents a comprehensive analysis of the effect of urbanization on the surface air temperature (SAT) from 1951 to 2018 in the Philippines. The daily minimum temperature (T_min) and daily maximum temperature (T_max) records from 34 meteorological stations were used to derive extreme temperature indices. These stations were then classified as urban or rural based on satellite night-lights. The results showed a significant difference in the SAT trends between urban and rural stations, indicative of the effect of urbanization in the country. Larger and more significant warming trends were observed in indices related …

Measurement Report: Firework Impacts On Air Quality In Metro Manila, Philippines, During The 2019 New Year Revelry, Genevieve Rose Lorenzo, Paola Angela Bañaga, Maria Obiminda L. Cambaliza, Melliza Templonuevo Cruz, Mojtaba Azadi Aghdam, Avelino Arellano, Grace Betito, Rachel A. Braun, Andrea F. Corral, Hossein Dadashazar, Eva-Lou Edwards, Edwin Eloranta, Robert Holz, Gabrielle Leung, Lin Ma, Alexander B. Macdonald, Jeffrey S. Reid, James Bernard Simpas, Connor Stahl, Shane Marie Visaga, Armin Sorooshian

Physics Faculty Publications

Fireworks degrade air quality, reduce visibility, alter atmospheric chemistry, and cause short-term adverse health effects. However, there have not been any comprehensive physicochemical and optical measurements of fireworks and their associated impacts in a Southeast Asia megacity, where fireworks are a regular part of the culture. Size-resolved particulate matter (PM) measurements were made before, during, and after New Year 2019 at the Manila Observatory in Quezon City, Philippines, as part of the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). A high-spectral-resolution lidar (HSRL) recorded a substantial increase in backscattered signal associated with high aerosol loading ∼440 m above the …

Measurement Report: Long-Range Transport Patterns Into The Tropical Northwest Pacific During The Camp2ex Aircraft Campaign: Chemical Composition, Size Distributions, And The Impact Of Convection, Miguel Ricardo A. Hilario, Ewan Crosbie, Michael Shook, Jeffrey S. Reid, Maria Obiminda L. Cambaliza, James Bernard Simpas, Luke Ziemba, Joshua P. Digangi, Glenn S. Diskin, Phu Nguyen, F. Joseph Turk, Edward Winstead, Claire E. Robinson, Jian Wang, Jiaoshi Zhang, Yang Wang, Subin Yoon, James Flynn, Sergio L. Alvarez, Ali Behrangi, Armin Sorooshian

Physics Faculty Publications

The tropical Northwest Pacific (TNWP) is a receptor for pollution sources throughout Asia and is highly susceptible to climate change, making it imperative to understand long-range transport in this complex aerosol-meteorological environment. Measurements from the NASA Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex; 24 August to 5 October 2019) and back trajectories from the National Oceanic and Atmospheric Administration Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) were used to examine transport into the TNWP from the Maritime Continent (MC), peninsular Southeast Asia (PSEA), East Asia (EA), and the West Pacific (WP). A mid-campaign monsoon shift on 20 September …

A Climatological Analysis Of The Monsoon Break Following The Summer Monsoon Onset Over Luzon Island, Philippines, Lyndon Mark P. Olaguera, Jun Matsumoto, Hisayuki Kubota, Esperanza O. Cayanan, Flaviana D. Hilario

Physics Faculty Publications

This study investigates the climatology of the monsoon break following the onset of the summer rainy season over Luzon Island (120–122.5°E, 13–22°N) in the Philippines from 1979–2017. The first post-onset monsoon break is remarkable in stations located over the north and central Luzon Island and occurs climatologically in early June. Composite analysis of the large-scale circulation features during the monsoon break period shows that this break is associated with the westward extension of the western North Pacific Subtropical High (WNPSH), which weakened the monsoon southwesterlies and induced enhanced low-level divergence over Luzon Island. The westward extension of the WNPSH may …

Non-Tropical Cyclone Related Winter Heavy Rainfall Events Over The Philippines: Climatology And Mechanisms, Lyndon Mark Olaguera, Jun Matsumoto, Julie Mae Dado, Gemma T. Narisma

Physics Faculty Publications

This study investigates non-tropical cyclone (TC) related boreal winter heavy rainfall events that lead to extensive flooding (HRF) over the Philippines through a case study and composite analysis. The HRF event examined occurred during January 16–22, 2017 over Cagayan de Oro City (CDO) in Mindanao Island (122–127°E, 5–10°N). The accumulated rainfall over CDO reached by about 180 mm from 00 UTC January 16 to 00 UTC January 17, 2017, exceeding the climatological maximum daily rainfall in January over this area. The interaction of a westward propagating cyclonic circulation over Mindanao Island (MCC) and a shearline that is associated with an …

Sources And Characteristics Of Size-Resolved Particulate Organic Acids And Methanesulfonate In A Coastal Megacity: Manila, Philippines, Connor Stahl, Melliza Templonuevo Cruz, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Mojtaba Azadi Aghdam, Maria Obiminda L. Cambaliza, Genevieve Rose Lorenzo, Alexander B. Macdonald, Miguel Ricardo A. Hilario, Preciosa Corazon Pabroa, John Robin Yee, James Bernard Simpas, Armin Sorooshian

Physics Faculty Publications

A 16-month (July 2018–October 2019) dataset of size-resolved aerosol composition is used to examine the sources and characteristics of five organic acids (oxalate, succinate, adipate, maleate, phthalate) and methanesulfonate (MSA) in Metro Manila, Philippines. As one of the most polluted megacities globally, Metro Manila offers a view of how diverse sources and meteorology impact the relative amounts and size distributions of these species. A total of 66 sample sets were collected with a Micro-Orifice Uniform Deposit Impactor (MOUDI), of which 54 sets were analyzed for composition. Organic acids and MSA surprisingly were less abundant than in other global regions that …

Long-Range Aerosol Transport And Impacts On Size-Resolved Aerosol Composition In Metro Manila, Philippines, Rachel A. Braun, Mojtaba Azadi Aghdam, Paola Angela Bañaga, Grace Betito, Maria Obiminda L. Cambaliza, Melliza Templonuevo Cruz, Genevieve Rose Lorenzo, Alexander B. Macdonald, James Bernard Simpas, Connor Stahl, Armin Sorooshian

Physics Faculty Publications

This study analyzes long-range transport of aerosol and aerosol chemical characteristics based on instances of high- and low-aerosol-loading events determined via ground-based size-resolved aerosol measurements collected at the Manila Observatory in Metro Manila, Philippines, from July to October 2018. Multiple data sources, including models, remote sensing, and in situ measurements, are used to analyze the impacts of long-range aerosol transport on Metro Manila and the conditions at the local and synoptic scales facilitating this transport. Through the use of case studies, evidence of long-range transport of biomass burning aerosol and continental emissions is identified in Metro Manila. Long-range transport of …

Investigating Size-Segregated Sources Of Elemental Composition Of Particulate Matter In The South China Sea During The 2011 Vasco Cruise, Miguel Ricardo Hilario, Melliza Templonuevo Cruz, Maria Obiminda L. Cambaliza, Jeffrey S. Reid, Peng Xian, James Bernard Simpas, Nofel Lagrosas, Sherdon Niño Uy, Steve Cliff, Yongjing Zhao

Physics Faculty Publications

The South China Sea (SCS) is a receptor of numerous natural and anthropogenic aerosol species from throughout greater Asia. A combination of several developing countries, archipelagic and peninsular terrain, a strong Asian monsoon climate, and a host of multi-scale meteorological phenomena make the SCS one of the most complex aerosol–meteorological systems in the world. However, aside from the well-known biomass burning emissions from Indonesia and Borneo, the current understanding of aerosol sources is limited, especially in remote marine environments. In September 2011, a 2-week research cruise was conducted near Palawan, Philippines, to sample the remote SCS environment. Size-segregated aerosol data …

Aerosol Particle And Black Carbon Emission Factors Of Vehicular Fleet In Manila, Philippines, Leizel Madueño, Simonas Kecorius, Wolfram Birmili, Thomas Müller, James Bernard Simpas, Edgar Vallar, Maria Cecilia Galvez, Mylene Cayetano, Alfred Wiedensohler

Physics Faculty Publications

Poor air quality has been identified as one of the main risks to human health, especially in developing regions, where the information on physical chemical properties of air pollutants is lacking. To bridge this gap, we conducted an intensive measurement campaign in Manila, Philippines to determine the emission factors (EFs) of particle number (PN) and equivalent black carbon (BC). The focus was on public utility jeepneys (PUJ), equipped with old technology diesel engines, widely used for public transportation. The EFs were determined by aerosol physical measurements, fleet information, and modeled dilution using the Operational Street Pollution Model (OSPM). The results …

Laser Irradiation Of Mung Bean (Vigna Radiata L.) At Two Wavelengths For Enhanced Seedling Development, Rayno Vic B. Janayon, Raphael A. Guerrero

Physics Faculty Publications

Two laser sources operating at wavelengths of 632.8 nm (He-Ne) and 488 nm (Ar+

) are used in examining the effects of coherent, low-power, continuous wave exposure on the development of Vigna radiata L. Presowing laser irradiation of seeds leads to an improvement of mung bean seedling characteristics, with increased values of hypocotyl length (an increase of up to 22.5%), root length (an increase of up to 28.8%), and seedling mass (a maximum increase of 29.2%). Measured parameters between seedlings from laser-irradiated seeds and from control samples are statistically different at a level of significance equal to 0.05. For both …

Activity Pattern Of School/University Tenants And Their Family Members In Metro Manila – Philippines, Simonas Kecorius, Everlyn Gale Tamayo, Maria Cecilia Galvez, Leizel Madueño, Grace Betito, Mylene Gonzaga-Cayetano, Edgar Vallar, Alfred Wiedensohler

Physics Faculty Publications

Existing studies that focus on personal exposure to or the deposition dose of particulate pollution in developing regions are limited. Hence, in this study, as a first step, we present results on how people spend their daily time in Metro Manila, Philippines. This information is critical to assessing personal exposure to and the deposition dose of particulate pollutants. We found that people spend less time at home on workdays than weekends (52% versus 70%), the fraction of time spent at work/school increases with age until retirement, adult males spend less time at home than females (18% versus 28%), and people …

Electrowetting Actuation Of Polydisperse Nanofluid Droplets, Crismar Patacsil, Jan Patrick Calupitan, Erwin Enriquez, Raphael A. Guerrero

Physics Faculty Publications

We present results of electrowetting experiments employing droplets formed from aqueous suspensions of Au nanoparticles. A planar electrowetting system, consisting of a Pt wire electrode and a bottom Cu electrode with an insulating silicone layer, is used to observe changes in droplet contact angle when an external electric field is applied. The equilibrium contact angle at 0 V decreases with increasing nanoparticle concentration, dropping from 100.4° for pure deionized water to 94.7° for a 0.5 μM nanofluid. Increasing the nanoparticle content also lowers the required voltage for effective actuation. With actuation at 15 V, contact angle decreases by 9% …

Cherenkov-Phase-Matched Nonlinear Optical Detection And Generation Of Terahertz Radiation Via Gaas With Metal-Coating, Ramon M. Delos Santos, Shinpei Ozawa, Valynn Magusara, Syougo Azuma, Anthony Tuico, Vernalyn Copa, Arnel Salvador, Kohji Yamamoto, Armando Somintac, Kazuyoshi Kurihara, Hideaki Kitahara, Masahiko Tani, Elmer Estacio

Physics Faculty Publications

Terahertz (THz) wave detection and emission via Cherenkov-phase-matched nonlinear optical effects at 1.55-μm optical wavelength were demonstrated using a GaAs with metal-coating (M-G-M) and bare GaAs as a reference sample in conjunction with a metallic tapered parallel-plate waveguide (TPPWG). The metal-coated GaAs is superior to the bare wafer both as a THz electro-optic detector and as an emitter. Significant improvements in the detection and emission efficiency were obtained by utilizing a metal-coating due to better confinement and lower loss of the THz waves propagating in the M-G-M compared with bare GaAs.

Fabrication Of A Capacitive Relative Humidity Sensor Using Aluminum Thin Films Deposited On Etched Printed Circuit Board, Jacqueline Ann L. Lee, Ivan B. Culaba

Physics Faculty Publications

A capacitive humidity-sensing device was created by thermal evaporation of 99.999% aluminum. The substrate used for the coating was etched double-sided printed circuit board. The etched printed circuit board serves as the dielectric of the capacitor while the aluminum thin films deposited on either side serve as the plates of the capacitor. The capacitance was measured before and after exposure to humidity. The device was then calibrated by comparing the readings of capacitance with that of the relative humidity sensor of the Vernier LabQuest2. It was found that there is a linear relationship between the capacitance and relative humidity given …

Assessing The Sensitivity Of The Non-Hydrostatic Regional Climate Model To Boundary Conditions And Convective Schemes Over The Philippines, Gemma T. Narisma, Faye T. Cruz, Hidetaka Sasaki

Physics Faculty Publications

Regional climate models have been useful in climate studies and in downscaling climate projections from global climate models, especially for areas characterized by complex topography and coastline features, such as the Philippines. However, several factors may affect model skill, such as uncertainties related to the boundary conditions and model configuration. This study evaluates the performance of the non-hydrostatic regional climate model (NHRCM) over the Philippines. Present-day climate simulations at 50 km resolution are conducted using two sets of boundary conditions (ECMWF ERA-Interim and the NCEP/NCAR Reanalysis Project NNRP1), as well as two convective parameterization schemes in the model (Grell and …

Dynamics Of Optically-Generated Carriers In Si (100) And Si (111) Substrate-Grown Gaas/Algaas Core-Shell Nanowires, Ramon M. Delos Santos, Jasher John Ibañes, Maria Herminia Balgos, Rafael Jaculbia, Jessica Pauline Afalla, Michelle Bailon-Somintac, Elmer Estacio, Arnel Salvador, Armando Somintac, Christopher Que, Satoshi Tsuzuki, Kohji Yamamoto, Masahiko Tani

Physics Faculty Publications

GaAs/Al0.1Ga0.9As core-shell nanowires (CSNWs), with average lateral size of 125 nm, were grown on gold nanoparticle-activated Si (100) and Si (111) substrates via molecular beam epitaxy. Room temperature-photoluminescence (RT-PL) from the samples showed bulk-like GaAs and Al0.1Ga0.9As bandgap emission peaks at 1.43 and 1.56 eV, respectively. Higher PL emission intensity of the sample on Si (111) compared to that on Si (100) is attributed to uniform Al0.1Ga0.9As shell passivation of surface states on Si (111)-grown CSNWs. Carrier dynamics in two different temporal regimes were studied. In the sub-nanosecond time scale (300–500 ps), time-resolved radiative recombination efficiency of carriers was examined. …