Condensed Matter Physics Commons^™

Luminescence And Structural Properties Of Silicon-Germanium Quantum Structures Fabricated By Ion Implantation, Matheus Coelho Adam

Electronic Thesis and Dissertation Repository

The advancement of semiconductor materials has played a crucial role in driving positive technological breakthroughs that impact humanity in numerous ways. The presence of defects significantly alters the physical properties of semiconductors, making their analysis essential in the fabrication of semiconductor devices. I presented a new method to quantify surface and near-surface defects in single crystal semiconductors. Epitaxially-grown silicon was measured by low energy electron diffraction (LEED) to obtain the surface Debye temperature (θ_D). The results showed the surface θ_D of bulk Si (001), 1.0 μm, and 0.6 μm Si on sapphire of 333 K, 299 K, …

An Efficiently Excited Eu3+ Luminescent Site Formed In Eu,O-Codoped Gan, Takenori Iwaya, Shuhei Ichikawa, Volkmar Dierolf, Brandon Mitchell, Hayley Austin, Dolf Timmerman, Jun Tatebayashi, Yasufumi Fujiwara

Physics & Engineering Faculty Publications

For the development of III-nitride-semiconductor-based monolithic micro-light-emitting diode (LED) displays, Eu,O-codoped GaN (GaN:Eu,O) is a promising material candidate for the red LEDs. The luminescence efficiency of Eu-related emission strongly depends on the local atomic structure of Eu ions. Our previous research has revealed that post-growth thermal annealing is an effective method for reconfiguring luminescent sites, leading to a significant increase in light output. We observed the preferential formation of a site with a peak at similar to 2.004 eV by the annealing process. In this study, we demonstrate that it is a previously unidentified independent site (OMVPE-X) using combined excitation-emission …

Optical Studies Of Wide Bandgap Photonic Materials, Nikesh Maharjan

Dissertations, Theses, and Capstone Projects

In this dissertation work, optical properties of wide bandgap materials such as hexagonal Boron Nitride (h-BN) and Zinc Oxide (ZnO) have been studied. Deep UV photoluminescence spectroscopy was employed to study the optical properties of bulk h-BN and powder crystals using a laser of wavelength 200 nm, which is the fourth harmonic of Ti:Sapphire laser as excitation source. The properties and chemical compositions of annealed and unannealed bulk h-BN were investigated. The PL spectra from h-BN samples annealed at 900 ºC in ambient air, had strong phonon assisted band edge emissions along with a sharp atomic-like emission line at 4.09 …

Photoluminescence Spectra Of Silicon Doped With Cadmium, N A. Sultanov, E T. Rakhimov, Z Mirzajonov, F T. Yusupov

Scientific-technical journal

Cadmium and zinc, as transition metals, are deep-level impurities (DL) and have a significant effect on the electrical, photoelectric, recombination, and other properties of semiconductor crystals.This paper presents the results of experimental studies of the optical and electrical properties of silicon crystals containing impurity atoms of cadmium and zinc using DLTS and low-temperature photoluminescence (PL).

Fundamental Transport Properties In Silicon Quantum Structures, Nazban M. Darukhanawalla

Electronic Thesis and Dissertation Repository

In the field of silicon photonics, there is an effort to bridge the gap between electrical and optical signals on a single platform, creating a need for Si-based light sources. In this project, Si quantum structures – Si quantum wells and quantum dots in SiO2 were fabricated via solid state precipitation methods. Their properties were studied using X-ray photoelectron spectroscopy, photoluminescence and I-V measurements. Rutherford backscattering spectroscopy was used for depth analysis in monitoring the Si distribution. Different electrical transport mechanisms were explored to understand how an ensemble of silicon QD’s or a silicon quantum well behaves in an SiO2 …

Si Nanocrystal Synthesis Via Double Implantation And Variable Implantation, James M. Gaudet

Electronic Thesis and Dissertation Repository

Silicon (Si) nanocrystals (nc) precipitated from silicon-implanted silicon oxide (SiO₂) are of interest as a novel light source for illumination, biomedical applications, optical computing, etc. They have some advantages over conventional III-V compound semiconductor nanocrystals produced by colloidal synthesis. They are compatible with Si/SiO₂ based semiconductor processing, are stable, non-toxic at point of synthesis and consumption, and their luminescence falls with the infrared transmission window of biological materials. Unfortunately, synthesis of Si-nc embedded SiO₂ is uneconomical and is not as amenable to precise control of the size distribution of nanocrystals as is the case for III-V …

Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen

Doctoral Dissertations

Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …

Combined Spectroscopic And Scanning Probe Studies Of Electronic Interactions In Nanostructured 1d And 2d Semiconductors, Peijian Wang

Doctoral Dissertations

This dissertation includes the exploration about the following research questions: 1. What is the correlation between the work function and ground state interactions in organic semiconductor assemblies? 2. How do non-covalent chemical doping tune the work function in MoS₂? 3. Are there surface charges in the Aluminum doped ZnO nanocrystals (AZO) and what's the evolution of the surface charges and polarizabilities from undoped AZO to doped AZO? 4. How is the homogeneity like during doping in the organic thermoelectric materials? The techniques we employed in the research is the spatially registered Kelvin Probe Force Microscopy and Photoluminescence spectroscopy …

Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov

Theses and Dissertations

This thesis devoted to the experimental studies of yellow and blue luminescence (YL and BL relatively) bands in Gallium Nitride samples doped with C and Si. The band BL_C was at first observed in the steady-state photoluminescence spectrum under high excitation intensities and discerned from BL1 and BL2 bands appearing in the same region of the spectrum. Using the time-resolved photoluminescence spectrum, we were able to determine the shape of the BL_C and its position at 2.87 eV. Internal quantum efficiency of the YL band was estimated to be 90\%. The hole capture coefficient of the BL_{C …}

Study Of The Photoluminescence Spectra Of Mg-Doped Gan, Puranjan Ghimire

Theses and Dissertations

We have studied luminescence properties of Mg-doped GaN grown by hydride vapor phase epitaxy. Steady state photoluminescence (PL) spectra have been analyzed. Exciton, ultraviolet luminescence (UVL) and blue luminescence (BL) bands are the dominant PL bands in the spectra. At low temperature, Exciton and UVL bands show almost no shift with excitation intensity, whereas the BL band blueshifts by almost 0.4 ���� with increasing excitation intensity by seven orders of magnitude. Such shifting nature of bands with excitation intensity is explained by assuming that the BL band is detected from the region of the sample where potential fluctuations are very …

Light Soaking Phenomena In Organic-Inorganic Mixed Halide Perovskite Single Crystals, Hye Ryung Byun, Dae Young Park, Hye Min Oh, Gon Namkoong, Mun Seok Jeong

Electrical & Computer Engineering Faculty Publications

Recently, organic inorganic mixed halide perovskite (MAPbX₃; MA = CH₃NH₃^+, X = Cl^-, Br^-, or I^-) single crystals with low defect densities have been highlighted as candidate materials for high-efficiency photovoltaics and optoelectronics. Here we report the optical and structural investigations of mixed halide perovskite (MAPbBr_3-xI_x) single crystals. Mixed halide perovskite single crystals showed strong light soaking phenomena with light illumination conditions that were correlated to the trapping and detrapping events from defect sites. By systematic investigation with optical analysis, we found that the …

Time-Resolved Photoluminescence Studies Of Point Defects In Gan, Joy Dorene Mcnamara

Theses and Dissertations

Time-resolved photoluminescence (TRPL) measurements paired with steady-state photoluminescence (SSPL) measurements can help to determine the PL lifetime, shape and position of unresolved bands, capture coefficients, and concentrations of free electrons and defects.PL bands that are obscured in the SSPL spectra can be accurately revealed by TRPL measurements. TRPL measurements are able to show if the PL band originates from an internal transition between different states of the same defect. The main defect-related PL bands in high-purity GaN grown by hydride vapor phase epitaxy (HVPE) which have been investigated are the ultraviolet, blue, green, yellow and red luminescence bands (UVL, BL, …

Investigating The Influence Of Interface And Vacancy Defects On The Growth Of Silicon Quantum Dots In Sio2, John Phelan

Electronic Thesis and Dissertation Repository

The effects of interface and vacancy defects on silicon quantum dot (Si-QD) growth are investigated using measurements of Time Resolved Photoluminescence (TRPL), Photoluminescence (PL) Spectroscopy and Electron Paramagnetic Resonance (EPR). Thermally grown SiO₂ thin films (280nm) were irradiated with high energy (400keV – 1MeV) silicon ions in order to introduce defects into the Si-QD growth layer of SiO₂. A noticeable increase in PL emission intensity is seen with the highest energy pre-implanted sample over a single implant sample. TRPL results show increased radiative lifetimes for the lower energy (400keV) pre-implant while little or no difference is seen …

The Study Of Optoelectronics In Semiconductor And Metallic Nanoparticle Hybrid Systems, Daniel G. Schindel

Electronic Thesis and Dissertation Repository

This thesis examines optoelectronics of photonic crystals and photonic nanofibers, especially with quantum dots and metallic nanoparticles doped into them. The simulations produced focus on the quantum dots, which are presented in an ensemble of 3-level systems.

In order to consider a photonic nanofiber in isolation, a model was developed for the density of photonic states. We studied two profiles, a square cross-section and a circular cross-section. In addition, we consider two architectures, one where a photonic crystal surrounds a dielectric fiber, and one where the fiber is another photonic crystal. We found several photonic nanofibers with a single bound …

Electron-Phonon Interactions And Quantum Confinement Effects On Optical Transitions In Nanoscale Silicon Films, Vimal Kumar Kamineni

Legacy Theses & Dissertations (2009 - 2024)

Theoretical studies have attributed the temperature dependence of the linear optical response (dielectric function) of bulk semiconductors to electron-phonon interactions and thermal expansion of the lattice. However, the role of phonons in the optical properties of nanoscale structures is often overlooked. This thesis systematically investigates the impact of both carrier confinement and electron-phonon interactions using nanoscale films of silicon in crystalline silicon quantum wells (c-Si QW). Spectroscopic ellipsometry (SE) is a linear optical technique used to of extract the dielectric function and thickness of very thin films. X-ray reflectivity (XRR) was used as the complementary thickness metrology method. The dielectric …

Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Nanometer-scale crystal silicon films surrounded by SiO₂ were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. When sufficiently thin (<2 >nm), all layers emitted red photoluminescence under blue and UV cw excitation, with a spectrum that did not depend on the mean layer thickness. The spectrum was roughly Gaussian with a peak energy of 1.65 eV, which is lower than for most porous silicon spectra. The time scale for the luminescence decay was ~35 μs at room temperature and …

Visible Luminescence From Single Crystal‐Silicon Quantum Wells, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Single crystal‐silicon quantum wells with SiO₂ barriers have been grown from SIMOX silicon‐on‐insulator substrates. Photoluminescence in the red and near‐infrared is observed for average well width <8 >nm, with peak signal for 2‐nm average width. The luminescence spectrum is independent of well width for SiO₂ barriers, but shifts 0.3 eV to higher energy upon removal of the upper oxide layer with HF. Both results suggest the importance of radiation from surface states.