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Full-Text Articles in Physics

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 Aug 2019

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).


Voltage Controlled Magnetism In Cr2o3 Based All-Thin-Film Systems, Junlei Wang, Will Echtenkamp, Ather Mahmood, Christian Binek May 2019

Voltage Controlled Magnetism In Cr2o3 Based All-Thin-Film Systems, Junlei Wang, Will Echtenkamp, Ather Mahmood, Christian Binek

Christian Binek Publications

Voltage-control of exchange biases through active selection of distinct domain states of the magnetoelectric and antiferromagnetic pinning layer is demonstrated for Cr2O3/CoPd heterostructures. Progress and obstacles towards an isothermal switching of exchange bias are discussed. An alternative approach avoiding exchange bias for voltage-controlled memory exploits boundary magnetization at the surface of Cr2O3 as voltage-controlled state variable. We demonstrate readout and switching of boundary magnetization in ultra-thin Cr2O3/Pt Hall bar devices where reversal of boundary magnetization is achieved via magnetoelectric annealing with simultaneously applied ±0.5 V and 400 mT electric and magnetic fields.


Space-Charge Limited Conduction In Epitaxial Chromia Films Grown On Elemental And Oxide-Based Metallic Substrates, C.-P. Kwan, Mike Street, Ather Mahmood, Will Echtenkamp, M. Randle, K. He, J. Nathawat, N. Arabchigavkani, B. Barut, S. Yin, R. Dixit, Uttam Singisetti, Christian Binek, J. P. Bird May 2019

Space-Charge Limited Conduction In Epitaxial Chromia Films Grown On Elemental And Oxide-Based Metallic Substrates, C.-P. Kwan, Mike Street, Ather Mahmood, Will Echtenkamp, M. Randle, K. He, J. Nathawat, N. Arabchigavkani, B. Barut, S. Yin, R. Dixit, Uttam Singisetti, Christian Binek, J. P. Bird

Christian Binek Publications

We study temperature dependent (200 – 400 K) dielectric current leakage in high-quality, epitaxial chromia films, synthesized on various conductive substrates (Pd, Pt and V2O3). We find that trap-assisted space-charge limited conduction is the dominant source of electrical leakage in the films, and that the density and distribution of charge traps within them is strongly dependent upon the choice of the underlying substrate. Pd-based chromia is found to exhibit leakage consistent with the presence of deep, discrete traps, a characteristic that is related to the known properties of twinning defects in the material. The Pt- and V2O3-based films, in contrast, show ...


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 Jun 2018

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 May 2018

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 ...


Dielectric Properties Of Thin Cr2o3 Films Grown On Elemental And Oxide Metallic Substrates, Ather Mahmood, Mike Street, Will Echtenkamp, Chun Pui Kwan, Jonathan P. Bird, Christian Binek Apr 2018

Dielectric Properties Of Thin Cr2o3 Films Grown On Elemental And Oxide Metallic Substrates, Ather Mahmood, Mike Street, Will Echtenkamp, Chun Pui Kwan, Jonathan P. Bird, Christian Binek

Christian Binek Publications

In an attempt to optimize leakage characteristics of α-Cr2O3 thin films, its dielectric properties were investigated at local and macroscopic scale. The films were grown on Pd(111), Pt(111), and V2O3 (0001), supported on Al2O3 substrate. The local conductivity was measured by conductive atomic force microscopy mapping of Cr2O3 surfaces, which revealed the nature of defects that formed conducting paths with the bottom Pd or Pt layer. A strong correlation was found between these electrical defects and the grain boundaries revealed in the corresponding topographic scans ...


Electronic And Optical Properties Of La-Doped Sr3Ir2O7 Epitaxial Thin Films, Maryam Souri, Jsaminka Terzic, J. M. Johnson, John G. Connell, John H. Gruenewald, J. Thompson, Joseph W. Brill, J. Hwang, Gang Cao, Sung S. Ambrose Seo Feb 2018

Electronic And Optical Properties Of La-Doped Sr3Ir2O7 Epitaxial Thin Films, Maryam Souri, Jsaminka Terzic, J. M. Johnson, John G. Connell, John H. Gruenewald, J. Thompson, Joseph W. Brill, J. Hwang, Gang Cao, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

We have investigated structural, transport, and optical properties of tensile strained (Sr1−xLax)3Ir2O7 (x = 0, 0.025, 0.05) epitaxial thin films. While high-Tc superconductivity is predicted theoretically in the system, we have observed that all of the samples remain insulating with finite optical gap energies and Mott variable-range hopping characteristics in transport. Cross-sectional scanning transmission electron microscopy indicates that structural defects such as stacking faults appear in this system. The insulating behavior of the La-doped Sr3Ir2O7 thin films is presumably due to disorder-induced localization ...


Magnetic Domain Morphology In [Co(4a)/Pt(7a] Thin Film, Jeremy Metzner Aug 2017

Magnetic Domain Morphology In [Co(4a)/Pt(7a] Thin Film, Jeremy Metzner

Student Publications

A collection of results for multi-layered thin films and their magnetic domains.


Nanostructure Evolution Of Magnetron Sputtered Hydrogenated Silicon Thin Films, Dipendra Adhikari, Maxwell M. Junda, Sylvain X. Marsillac, Robert W. Collins, Nikolas J. Podraza Aug 2017

Nanostructure Evolution Of Magnetron Sputtered Hydrogenated Silicon Thin Films, Dipendra Adhikari, Maxwell M. Junda, Sylvain X. Marsillac, Robert W. Collins, Nikolas J. Podraza

Electrical & Computer Engineering Faculty Publications

Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure and ...


Optical Signatures Of Spin-Orbit Exciton In Bandwidth-Controlled Sr2Iro4 Epitaxial Films Via High-Concentration Ca And Ba Doping, Maryam Souri, B. H. Kim, John H. Gruenewald, John G. Connell, J. Thompson, J. Nichols, Jsaminka Terzic, B. I. Min, Gang Cao, Joseph W. Brill, Sung S. Ambrose Seo Jun 2017

Optical Signatures Of Spin-Orbit Exciton In Bandwidth-Controlled Sr2Iro4 Epitaxial Films Via High-Concentration Ca And Ba Doping, Maryam Souri, B. H. Kim, John H. Gruenewald, John G. Connell, J. Thompson, J. Nichols, Jsaminka Terzic, B. I. Min, Gang Cao, Joseph W. Brill, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

We have investigated the electronic and optical properties of (Sr1−xCax)2IrO4 (x = 0–0.375) and (Sr1−yBay)2IrO4 (y = 0–0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff = 1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1−xCax)2IrO4 to (Sr1−yBay ...


Direct Imaging Of Coexisting Ordered And Frustrated Sublattices In Artificial Ferromagnetic Quasicrystals, Barry Farmer, Vinayak Shantaram Bhat, Eric Teipel, J. Unguris, D. J. Keavney, Jeffrey Todd Hastings, Lance E. De Long Apr 2016

Direct Imaging Of Coexisting Ordered And Frustrated Sublattices In Artificial Ferromagnetic Quasicrystals, Barry Farmer, Vinayak Shantaram Bhat, Eric Teipel, J. Unguris, D. J. Keavney, Jeffrey Todd Hastings, Lance E. De Long

Physics and Astronomy Faculty Publications

We have used scanning electron microscopy with polarization analysis and photoemission electron microscopy to image the two-dimensional magnetization of permalloy films patterned into Penrose P2 tilings (P2T). The interplay of exchange interactions in asymmetrically coordinated vertices and short-range dipole interactions among connected film segments stabilize magnetically ordered, spatially distinct sublattices that coexist with frustrated sublattices at room temperature. Numerical simulations that include long-range dipole interactions between sublattices agree with images of as-grown P2T samples and predict a magnetically ordered ground state for a two-dimensional quasicrystal lattice of classical Ising spins.


Interface‐Coupled Bifeo3/Bimno3 Superlattices With Magnetic Transition Temperature Up To 410 K, Eun-Mi Choi, Josée E. Kliebeuker, Thomas Fix, Jie Xiong, Christy J. Kinane, Dario Arena, Sean Langridge, Aiping Chen, Zhenxing Bi, Joon Hwan Lee, Quanix Jia, Mark G. Blamire, Judith L. Macmanus-Driscoll Mar 2016

Interface‐Coupled Bifeo3/Bimno3 Superlattices With Magnetic Transition Temperature Up To 410 K, Eun-Mi Choi, Josée E. Kliebeuker, Thomas Fix, Jie Xiong, Christy J. Kinane, Dario Arena, Sean Langridge, Aiping Chen, Zhenxing Bi, Joon Hwan Lee, Quanix Jia, Mark G. Blamire, Judith L. Macmanus-Driscoll

Physics Faculty Publications

Enhanced magnetic transition temperatures are demonstrated in 50 nm thick (001)‐oriented (BiFeO3)m/(BiMnO3)m (BFO/BMO) superlattices (SL). Highly strained ultra‐short SLs showed a magnetic transition, TC2, up to ≈410 K as a result of ferrimagnetic interaction between BFO/BMO. All SL showed a new ferromagnetic transtion, TC1, of ≈150 K coming from Fe4+‐Fe4+ interaction explained by electron transfer/leakage from Fe3+ to Mn3+.


Identification Of Photocurrents In Topological Insulators, Derek A. Bas, Rodrigo A. Muniz, Sercan Babakiray, David Lederman, J. E. Sipe, Alan D. Bristow Jan 2016

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

Faculty 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 ...


Influence Of Mn Concentration On Magnetic Topological Insulator Mnxbi2−Xte3 Thin-Film Hall-Effect Sensor, Ravi L. Hadimani, S. Gupta, S. M. Harstad, Vitalij K. Pecharsky, David C. Jiles Nov 2015

Influence Of Mn Concentration On Magnetic Topological Insulator Mnxbi2−Xte3 Thin-Film Hall-Effect Sensor, Ravi L. Hadimani, S. Gupta, S. M. Harstad, Vitalij K. Pecharsky, David C. Jiles

Ames Laboratory Publications

Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3 topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3. The sensors with low Mn concentrations, MnxBi2-xTe3, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as ...


Crystallization Engineering As A Route To Epitaxial Strain Control, Andrew R. Akbashev, Aleksandr V. Plokhikh, Dmitri Barbash, Samuel Lofland, Jonathan E. Spanier Oct 2015

Crystallization Engineering As A Route To Epitaxial Strain Control, Andrew R. Akbashev, Aleksandr V. Plokhikh, Dmitri Barbash, Samuel Lofland, Jonathan E. Spanier

Faculty Scholarship for the College of Science & Mathematics

The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001)SrTiO3 and (001)LaAlO3substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001)BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001)SrTiO3 results in a coherently strained film ...


Epitaxial Crn Thin Films With High Thermoelectric Figure Of Merit, Eric L. Thies, Daniel A. Hillsberry, Dmitri A. Tenne May 2015

Epitaxial Crn Thin Films With High Thermoelectric Figure Of Merit, Eric L. Thies, Daniel A. Hillsberry, Dmitri A. Tenne

Physics Faculty Publications and Presentations

A large enhancement of the thermoelectric figure of merit is reported in single crystalline films of CrN. The strong reduction of the lattice thermal conductivity in the rock-salt phase of this material is shown to be related to intrinsic lattice instabilities, which is similar to the resonant bonding effect proposed for cubic IV-VI compounds. These results demonstrate that useful ideas from classic thermoelectrics and phase change materials can be extended to transition metal nitrides and oxides.


Maximum Screening Fields Of Superconducting Multilayer Structures, Alex Gurevich Jan 2015

Maximum Screening Fields Of Superconducting Multilayer Structures, Alex Gurevich

Physics Faculty Publications

It is shown that a multilayer comprised of alternating thin superconducting and insulating layers on a thick substrate can fully screen the applied magnetic field exceeding the superheating fields Hsof both the superconducting layers and the substrate, the maximum Meissner field is achieved at an optimum multilayer thickness. For instance, a dirty layer of thickness ~0.1μm at the Nb surface could increase Hs similar or equal to 240 mT of a clean Nb up to Hs similar or equal to 290 mT. Optimized multilayers of Nb3Sn, NbN, some of the iron pnictides, or ...


Physical Analysis Of Vo2 Films Grown By Atomic Layer Deposition And Rf Magnetron Sputtering, Madhavi Tangirala, Kai Zhang, David Nminibapiel, Venkateswara Pallem, Christian Dussarrat, Wei Cao, Thomas N. Adam, Corbet S. Johnson, Hani E. Elsayed-Ali, Helmut Baumgart Jan 2014

Physical Analysis Of Vo2 Films Grown By Atomic Layer Deposition And Rf Magnetron Sputtering, Madhavi Tangirala, Kai Zhang, David Nminibapiel, Venkateswara Pallem, Christian Dussarrat, Wei Cao, Thomas N. Adam, Corbet S. Johnson, Hani E. Elsayed-Ali, Helmut Baumgart

Electrical & Computer Engineering Faculty Publications

Among the many vanadium suboxides and different stoichiometries, VO2 has received considerable attention due to its remarkable metal-insulator transition (MIT) behavior, which causes a significant reversible change in its electrical and optical properties occurring across the phase transition at 67°C. The initially amorphous VO2 thin films were fabricated by the emerging, Atomic Layer Deposition (ALD) technique with (tetrakis[ethylmethylamino]vanadium) {V(NEtMe)4} as precursor and H2O vapor as oxidation agent. For benchmarking we have also used the RF Magnetron Sputtering technique to deposit metallic vanadium thin films, which were later oxidized during furnace annealing ...


Polarization Of Bi2te3 Thin Film In A Floating-Gate Capacitor Structure, Hui Yuan, Kai Zhang, Haitao Li, Hao Zhu, John E. Bonevich, Helmut Baumgart, Curt A. Richter, Qiliang Li Jan 2014

Polarization Of Bi2te3 Thin Film In A Floating-Gate Capacitor Structure, Hui Yuan, Kai Zhang, Haitao Li, Hao Zhu, John E. Bonevich, Helmut Baumgart, Curt A. Richter, Qiliang Li

Electrical & Computer Engineering Faculty Publications

Metal-Oxide-Semiconductor (MOS) capacitors with Bi2Te3 thin film sandwiched and embedded inside the oxide layer have been fabricated and studied. The capacitors exhibit ferroelectric-like hysteresis which is a result of the robust, reversible polarization of the Bi2Te3 thin film while the gate voltage sweeps. The temperature-dependent capacitance measurement indicates that the activation energy is about 0.33 eV for separating the electron and hole pairs in the bulk of Bi2Te3, and driving them to either the top or bottom surface of the thin film. Because of the fast polarization speed, potentially excellent ...


Growth And Characterization Of Pt-Protected Gd5si4 Thin Films, Ravi L. Hadimani, Yaroslav Mudryk, Timothy E. Prost, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., David C. Jiles Jan 2014

Growth And Characterization Of Pt-Protected Gd5si4 Thin Films, Ravi L. Hadimani, Yaroslav Mudryk, Timothy E. Prost, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., David C. Jiles

Electrical and Computer Engineering Publications

Successful growth and characterization of thin films of giant magnetocaloric Gd5(SixGe1−x)4were reported in the literature with limited success. The inherent difficulty in producing this complex material makes it difficult to characterize all the phases present in the thin films of this material. Therefore, thin film of binary compound of Gd5Si4 was deposited by pulsed laser deposition. It was then covered with platinum on the top of the film to protect against any oxidation when the film was exposed to ambient conditions. The average film thickness wasmeasured to be approximately 350 nm using a scanning electron microscopy, and ...


Adsorption-Controlled Growth Of Bivo4 By Molecular-Beam Epitaxy, D. A. Hillsberry, D. A. Tenne Oct 2013

Adsorption-Controlled Growth Of Bivo4 By Molecular-Beam Epitaxy, D. A. Hillsberry, D. A. Tenne

Physics Faculty Publications and Presentations

Single-phase epitaxial films of the monoclinic polymorph of BiVO4 were synthesized by reactive molecular-beam epitaxy under adsorption-controlled conditions. The BiVO4 films were grown on (001) yttria-stabilized cubic zirconia (YSZ) substrates. Four-circle x-ray diffraction, scanning transmission electron microscopy (STEM), and Raman spectroscopy confirm the epitaxial growth of monoclinic BiVO4 with an atomically abrupt interface and orientation relationship (001)BiVO4 ∥ (001)YSZ with [100]BiVO4 ∥ [100]YSZ. Spectroscopic ellipsometry, STEM electron energy loss spectroscopy (STEM-EELS), and x-ray absorption spectroscopy indicate that the films have a direct band gap of 2.5 ± 0.1 eV.


Origin Of The Low Frequency Radiation Emitted By Radiative Polaritons Excited By Infrared Radiation In Planar La2o3 Films, Anita J. Vincent-Johnson, Yosep Schwab, Harkirat S. Mann, Mathieu Francoeur, James S. Hammonds Jr., Giovanna Scarel Jan 2013

Origin Of The Low Frequency Radiation Emitted By Radiative Polaritons Excited By Infrared Radiation In Planar La2o3 Films, Anita J. Vincent-Johnson, Yosep Schwab, Harkirat S. Mann, Mathieu Francoeur, James S. Hammonds Jr., Giovanna Scarel

Department of Physics and Astronomy - Faculty Scholarship

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ω, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ωi to the space surrounding the oxide film. The frequency ωi is the imaginary part of ω. The effects of the presence of the radiation leaked out at frequency ωi are observed experimentally and numerically in the infrared spectra of La2O3 films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ωi is found ...


Applications Of High Throughput (Combinatorial) Methodologies To Electronic, Magnetic, Optical, And Energy-Related Materials, Martin L. Green, Ichiro Takeuchi, Jason R. Hattrick-Simpers Jan 2013

Applications Of High Throughput (Combinatorial) Methodologies To Electronic, Magnetic, Optical, And Energy-Related Materials, Martin L. Green, Ichiro Takeuchi, Jason R. Hattrick-Simpers

Faculty Publications

High throughput (combinatorial) materials science methodology is a relatively new research paradigm that offers the promise of rapid and efficient materials screening, optimization, and discovery. The paradigm started in the pharmaceutical industry but was rapidly adopted to accelerate materials research in a wide variety of areas. High throughput experiments are characterized by synthesis of a “library” sample that contains the materials variation of interest (typically composition), and rapid and localized measurement schemes that result in massive data sets. Because the data are collected at the same time on the same “library” sample, they can be highly uniform with respect to ...


Nano-Cr-Film-Based Solar Selective Absorber With High Photo-Thermal Conversion Efficiency And Good Thermal Stability, Wei-Xi Zhou, Yan Shen, Er-Tao Hu, Yuan Zhao, Ming-Yu Sheng, Yu-Xiang Zheng, Song-You Wang, Young-Pak Lee, Cai-Zhuang Wang, David W. Lynch, Liang-Yao Chen Dec 2012

Nano-Cr-Film-Based Solar Selective Absorber With High Photo-Thermal Conversion Efficiency And Good Thermal Stability, Wei-Xi Zhou, Yan Shen, Er-Tao Hu, Yuan Zhao, Ming-Yu Sheng, Yu-Xiang Zheng, Song-You Wang, Young-Pak Lee, Cai-Zhuang Wang, David W. Lynch, Liang-Yao Chen

Physics and Astronomy Publications

Optical properties and thermal stability of the solar selective absorber based on the metal/dielectric four-layer film structure were investigated in the variable temperature region. Numerical calculations were performed to simulate the spectral properties of multilayer stacks with different metal materials and film thickness. The typical four-layer film structure using the transition metal Cr as the thin solar absorbing layer [SiO2(90nm)/Cr(10nm)/SiO2(80nm)/Al (≥100nm)] was fabricated on the Si or K9 glass substrate by using the magnetron sputtering method. The results indicate that the metal/dielectric film structure has a good spectral selective property ...


Growth Analysis Of (Ag,Cu)Inse2 Thin Films Via Real Time Spectroscopic Ellipsometry, S. A. Little, V. Ranjan, R. W. Collins, S. Marsillac Jan 2012

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.


Wetting Properties Induced In Nano-Composite Poss-Ma Polymer Films By Atomic Layer Deposited Oxides, Kyle A. Vasquez, Anita J. Vincent-Johnson, W. Chris Hughes, Brian H. Augustine, Kyoungmi Lee, Gregory N. Parsons, Giovanna Scarel Sep 2011

Wetting Properties Induced In Nano-Composite Poss-Ma Polymer Films By Atomic Layer Deposited Oxides, Kyle A. Vasquez, Anita J. Vincent-Johnson, W. Chris Hughes, Brian H. Augustine, Kyoungmi Lee, Gregory N. Parsons, Giovanna Scarel

Department of Physics and Astronomy - Faculty Scholarship

Due to their unique properties, nano-composite polyhedral oligomeric silsequioxane (POSS) copolymer films are attractive for various applications. Here we show that their natural hydrophobic character can become hydrophilic when the films are modified by a thin oxide layer, up to 8 nm thick, prepared using atomic layer deposition. A proper choice of the deposition temperature and thickness of the oxide layer are required to achieve this goal. Unlike other polymeric systems, a marked transition to a hydrophilic state is observed with oxide layers deposited at increasing temperatures up to the glass transition temperature (∼110 °C) of the POSS copolymer film ...


Measurement Of The Elastic Tensor Of Smsco3 And Ndsco3 Using Resonant Ultrasound Spectroscopy With Ab Initio Calculations, Kenneth A. Pestka, Eric S. Scott, Y Lepage Jan 2011

Measurement Of The Elastic Tensor Of Smsco3 And Ndsco3 Using Resonant Ultrasound Spectroscopy With Ab Initio Calculations, Kenneth A. Pestka, Eric S. Scott, Y Lepage

Student-Faculty Collaborative Research Publications

The complete elastic tensors of SmScO3 and NdScO3 were measured using resonant ultrasound spectroscopy (RUS) in combination with ab-initio calculations. Measurement of the elastic tensor of these recently synthesized single crystal RE scandates is essential for understanding dynamic lattice applications including phonon confinement, strain induced thin film growth and superlattice construction. On average, the experimental elastic constants differed by less than 5% of the theoretical values, further validating the accuracy of modern ab-initio calculations as a means of estimating the initial elastic constants used in RUS measurements.


From Initial To Late Stages Of Epitaxial Thin Film Growth: Stm Analysis And Atomistic Or Coarsegrained Modeling, James W. Evans, Yong Han, Barış Ünal, Maozhi Li, K. J. Caspersen, Dapeng Jing, Anthony R. Layson, C. R. Stoldt, T. Duguet, Patricia A. Thiel Aug 2010

From Initial To Late Stages Of Epitaxial Thin Film Growth: Stm Analysis And Atomistic Or Coarsegrained Modeling, James W. Evans, Yong Han, Barış Ünal, Maozhi Li, K. J. Caspersen, Dapeng Jing, Anthony R. Layson, C. R. Stoldt, T. Duguet, Patricia A. Thiel

Chemistry Conference Papers, Posters and Presentations

Epitaxial thin film growth by vapor deposition or molecular beam epitaxy under ultra‐high vacuum conditions generally occurs in two stages: (i) nucleation and growth of well‐separated islands on the substrate; (ii) subsequent formation of a thicker continuous film with possible kinetic roughening. For homoepitaxial growth, two‐dimensional (2D) monolayer islands are formed during submonolayer deposition. Typically, the presence of a step‐edge barrier inhibits downward transport and leads to the formation of mounds (multilayer stacks of 2D islands) during multilayer growth. For heteroepitaxial growth, islands formed in the initial stages of deposition sometimes have a 2D monolayer structure ...


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 Jan 2009

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


Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa Jan 2009

Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa

Physics Faculty Publications and Presentations

We report the creation of nano-structures via Dip Pen Nanolithography by locally exploiting the mechanical response of polymer thin films to an acidic environment. Protonation of cross linked poly(4-vinylpyridine) (P4VP) leads to a swelling of the polymer. We studied this process by using an AFM tip coated with a pH 4 buffer. Protons migrate through a water meniscus between tip and sample into the polymer matrix and interact with the nitrogen of the pyridyl group forming a pyridinium cation. The increase in film thickness, which is due to Coulomb repulsion between the charged centers, was investigated using Atomic Force ...