Physics Commons^™

Novel As-S-Se Compositions Of Solution-Processed Chalcogenide Thin Films For Infrared Optics, Annabella Orsini

Physics and Astronomy Honors Papers

Chalcogenide glasses (ChGs) have a wide range of interdisciplinary applications. In industry, ChGs are used to vastly improve infrared sight abilities. There are, however, improvements that can be made to the films’ stability, cost, and flexibility. Our project seeks to produce thin films that have these improvements, with capabilities comparable or better than what is widely used in the field. Thin films created through solution-based processes have proven to be much more flexible in comparison to bulk glass versions. Other elements in Group 16, such as Sulfur and Selenium have shown across literature to be a cost-effective alternative to Tellurium …

Erratum: "Imaging The Three‐Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri‐Spot Point Spread Function", Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

In the original paper, a calibration error exists in the image-formation model used to analyze experimental images taken by our microscope, causing a bias in the orientation measurements in Figs. 2 and 3. The updated measurements are shown in Fig. E1. We have also updated the supplementary material for the original article to discuss the revised PSF model and estimation algorithms (supplementary material 2) and show the revised model and measurements (Figs. S1, S3, S7, S8, and S10–S13).

Imaging The Three-Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri-Spot Point Spread Function, Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

Fluorescence photons emitted by single molecules contain rich information regarding their rotational motions, but adapting single-molecule localization microscopy (SMLM) to measure their orientations and rotational mobilities with high precision remains a challenge. Inspired by dipole radiation patterns, we design and implement a Tri-spot point spread function (PSF) that simultaneously measures the three-dimensional orientation and the rotational mobility of dipole-like emitters across a large field of view. We show that the orientation measurements done using the Tri-spot PSF are sufficiently accurate to correct the anisotropy-based localization bias, from 30 nm to 7 nm, in SMLM. We further characterize the emission anisotropy …

Characterization And Analysis Of Ultrathin Cigs Films And Solar Cells Deposited By 3-Stage Process, Grace Rajan, Krishna Aryal, Shankar Karki, Puruswottam Aryal, Robert W. Collins, Sylvain Marsillac

Electrical & Computer Engineering Faculty Publications

In view of the large-scale utilization of Cu(In,Ga)Se₂ (CIGS) solar cells for photovoltaic application, it is of interest not only to enhance the conversion efficiency but also to reduce the thickness of the CIGS absorber layer in order to reduce the cost and improve the solar cell manufacturing throughput. In situ and real-time spectroscopic ellipsometry (RTSE) has been used conjointly with ex situ characterizations to understand the properties of ultrathin CIGS films. This enables monitoring the growth process, analyzing the optical properties of the CIGS films during deposition, and extracting composition, film thickness, grain size, and surface roughness which …

Identification Of Photocurrents In Topological Insulators, Derek A. Bas, Rodrigo A. Muniz, Sercan Babakiray, David Lederman, J. E. Sipe, Alan D. Bristow

Faculty & Staff Scholarship

Optical injection and detection of charge currents is an alternative to conventional transport and photoemission measurements, avoiding the necessity of invasive contact that may disturb the system being examined. This is a particular concern for analyzing the surface states of topological insulators. In this work one- and two-color sources of photocurrents are isolated and examined in epitaxial thin films of Bi2Se3. We demonstrate that optical excitation and terahertz detection simultaneously captures one- and two-color photocurrent contributions, which has not been required for other material systems. A method is devised to extract the two components, and in doing so each can …

An Infrared Imaging Method For High-Throughput Combinatorial Investigation Of Hydrogenation-Dehydrogenation And New Phase Formation Of Thin Films, H. Oguchi, Jason Hattrick-Simpers, I. Takeuchi, E. Heilweil, L. Bendersky

Jason R. Hattrick-Simpers

We have developed an infrared imaging setup enabling in situ infrared images to be acquired, and expanded on capabilities of an infrared imaging as a high-throughput screening technique, determination of a critical thickness of a Pd capping layer which significantly blocks infrared emission from below, enhancement of sensitivity to hydrogenation and dehydrogenation by normalizing raw infrared intensity of a Mg thin film to an inert reference, rapid and systematic screening of hydrogenation and dehydrogenation properties of a Mg–Ni composition spread covered by a thickness gradient Pd capping layer, and detection of formation of a Mg2Si phase in a Mg thin …

The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell

Electronic Theses and Dissertations

Cubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated. Plasma-Enhanced Molecular Beam Epitaxy was used to grow Zn1-xMgxO thin films and formation conditions were explored by varying the growth temperature, Mg source flux, oxygen flow rate, and radio-frequency (RF) power coupled into …

Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu

Open Access Theses & Dissertations

Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ∼5.60 eV for monoclinic while it is ∼6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (ρac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while ρac∼1Ω-m at low frequencies (100 Hz), it decreased to ∼ 104 Ω-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.

A Study Of Wo3 And W0.95ti0.05o3 Thin Films Using Comparative Spectroscopy, James Heyward Howard

Open Access Theses & Dissertations

Tungsten oxide (WO3) is important and well-studied in materials science, particularly for sensor applications. In this research work, we consider the innovation of adding Ti to thin films of this material. Since the characteristics of any such material are strongly dependent on the conditions and methods used in its deposition, the main objective of this project is to provide a detailed spectroscopic characterization by Raman scattering, infrared absorption, and X-ray photoelectron spectroscopy (XPS) of WO3 and of W0.95Ti0.05O3. This characterization will be based on comparison of the morphology and composition of WO3-based thin films, grown by radio frequency magnetron reactive …

Growth Analysis Of (Ag,Cu)Inse2 Thin Films Via Real Time Spectroscopic Ellipsometry, S. A. Little, V. Ranjan, R. W. Collins, S. Marsillac

Electrical & Computer Engineering Faculty Publications

In situ and ex situ characterization methods have been applied to investigate the properties of (Ag,Cu)InSe₂ (ACIS) thin films. Data acquired from real time spectroscopic ellipsometry (RTSE) experiments were analyzed to extract the evolution of the nucleating, bulk, and surface roughness layer thicknesses. The evolution of these layer thicknesses suggests a transition from Volmer-Weber to Stranski-Krastanov type behavior when Cu is replaced by Ag. The complex dielectric functions of ACIS at both deposition and room temperature as a function of film composition were also extracted from the RTSE data, enabling parameterization of the alloy optical properties.

Spectroscopic Analysis Of Tungsten Oxide Thin Films For Sensor Applications, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

The objective of this study is targeted toward improving the quality of pure tungsten oxide (WO3) for application to the detection of poisoning gases, especially of H2S. While pure WO3 is a recognized candidate for gas sensing, its characteristics are strongly dependent on the conditions and methods used in its deposition.

Samples of WO3 thin films analyzed in this work were grown on silicon and sapphire substrates using RF magnetron sputtering at a number of different substrate temperatures and Ar:O2 pressure ratios. The properties of the samples were investigated spectroscopically with the goal of determining how variations in the above …

Electronic And Structural Properties Of Molybdenum Thin Films As Determined By Real Time Spectroscopic Ellipsometry, J. D. Walker, H. Khatri, V. Ranjan, Jian Li, R. W. Collins, S. Marsillac

Electrical & Computer Engineering Faculty Publications

Walker, J.D., Khatri, H., Ranjan, V., Li, J., Collins, R.W., & Marsillac, S. (2009). Electronic and structural properties of molybdenum thin films as determined by real-time spectroscopic ellipsometry. Applied Physics Letters, 94(14). doi: 10.1063/1.3117222

An Infrared Imaging Method For High-Throughput Combinatorial Investigation Of Hydrogenation-Dehydrogenation And New Phase Formation Of Thin Films, H. Oguchi, Jason R. Hattrick-Simpers, I. Takeuchi, E. J. Heilweil, L. A. Bendersky

Faculty Publications

We have developed an infrared imaging setup enabling in situ infrared images to be acquired, and expanded on capabilities of an infrared imaging as a high-throughput screening technique, determination of a critical thickness of a Pd capping layer which significantly blocks infrared emission from below, enhancement of sensitivity to hydrogenation and dehydrogenation by normalizing raw infrared intensity of a Mg thin film to an inert reference, rapid and systematic screening of hydrogenation and dehydrogenation properties of a Mg–Ni composition spread covered by a thickness gradient Pd capping layer, and detection of formation of a Mg₂Si phase in a …

Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal

Conference Papers

A study of the light induced surface relief modulation in thin photopolymer layers is reported. Due to the nature of the photopolymer used no additional post-processing is required after holographic recording. An investigation of the dependence of the amplitude of the photoinduced relief modulation on different parameters of recording such as spatial frequency, intensity of the beams and times of exposure has been carried out. The surface relief modulation is characterized by white light interferometry. Photopolymer layer thickness ranges from 1-5m. A model of the mechanism of surface relief formation is proposed on the basis of the measured dependencies. A …

Femtosecond Spectrotemporal Magneto-Optics, J.-Y. Bigot, L. Guidoni, E. Beaurepaire, Peter N. Saeta

All HMC Faculty Publications and Research

A new method to measure and analyze the time and spectrally resolved polarimetric response of magnetic materials is presented. It allows us to study the ultrafast magnetization dynamics of a CoPt₃ ferromagnetic film. The analysis of the pump-induced rotation and ellipticity detected by a broad spectrum probe beam shows that magneto-optical signals predominantly reflect the spin dynamics in ferromagnets.

Design Of Gradient Index Optical Thin Films, Jeffrey J. Druessel

Theses and Dissertations

Gradient index thin films provide greater flexibility for the design of optical coatings than the more conventional 'layer' films. In addition, gradient index films have higher damage thresholds and better adhesion properties. This dissertation presents an enhancement to the existing inverse Fourier transform gradient index design method, and develops a new optimal design method for gradient index films using a generalized Fourier series approach. The inverse Fourier transform method is modified to include use of the phase of the index profile as a variable in rugate filter design. Use of an optimal phase function in Fourier-based filter designs reduces the …

Optical Rectification At Semiconductor Surfaces, Shun Lien Chuang, Stefan Schmitt-Rink, Benjamin I. Greene, Peter N. Saeta, Anthony F. J. Levi

All HMC Faculty Publications and Research

We show that far-infrared radiation can be generated in the depletion field near semiconductor surfaces via the inverse Franz-Keldysh effect or electric-field-induced optical rectification. This mechanism is conceptually different from those previously proposed and accounts for many recent experimental observations.