Engineering Commons^™

Ultrafast Electron Diffraction Study Of The Dynamics Of Antimony Thin Films And Nanoparticles, Mahmoud Abdel-Fattah

Electrical & Computer Engineering Theses & Dissertations

The ultrafast fast phenomena that take place following the application of a 120 fs laser pulse on 20 nm antimony thin films and 40 nm nanoparticles were studied using time-resolved electron diffraction. Samples are prepared by thermal evaporation, at small thickness (< 10 nm) antimony nanoparticles form while at larger thicknesses we get continuous thin films.

The samples are annealed and studied by static heating to determine their Debye temperatures, which were considerably less than the standard value. The thermal expansion under static heating also yielded the expansion coefficient of the sample material. Nanoparticle samples gave a very accurate thermal expansion coefficient (11 × 10^-6 K^-1).

Ultrafast time resolved electron diffraction …

Contact Resistance Study Of Noble Metals And Alloy Films Using A Scanning Probe Microscope Test Station, Lei Chen, H. Lee, Z. J. Guo, Nicol E. Mcgruer, K. W. Gilbert, S. Mall, Kevin D. Leedy, George G. Adams

George G. Adams

The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system (MEMS) switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient (less than 1 mN) to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum (Pt), rhodium (Rh), ruthenium (Ru), and their alloys with gold (Au) were deposited as thin films on …

Contact Resistance Study Of Noble Metals And Alloy Films Using A Scanning Probe Microscope Test Station, Lei Chen, H. Lee, Z. J. Guo, Nicol E. Mcgruer, K. W. Gilbert, S. Mall, Kevin D. Leedy, George G. Adams

Nicol E. McGruer

The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system (MEMS) switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient (less than 1 mN) to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum (Pt), rhodium (Rh), ruthenium (Ru), and their alloys with gold (Au) were deposited as thin films on …

Influence Of Reactive Atmosphere On Properties Of Cobalt Ferrite Thin Films Prepared Using Pulsed-Laser Deposition, A. Raghunathan, David C. Jiles, J. E. Snyder

David C. Jiles

A series of cobaltferrite (CFO) thin films were grown on SiO2/Si(100) substrates using pulsed-laser deposition (PLD) at substrate temperature (T DEP) of 250 °C and oxygen pressures (P O2) from 0.67 to 6.7 Pa. The influence of PO2 on crystal structure, phase mixture, deposition rate, and magnetic properties was investigated. It is shown in this study that there is a window of PO2 for optimized growth of nanograined CFO films at low T DEP and that either higher or lower values of PO2 produce undesirable multiphase mixtures. CFO filmsgrown at such low substrate temperature and optimized oxygen pressure on thermal …

Investigation Of Reactively Sputtered Boron Carbon Nitride Thin Films, Vinit O. Todi

Electronic Theses and Dissertations

Research efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For this purpose, B-C-N ternary system which is based on carbon, boron and nitrogen which exhibit exceptional properties and attract much attention from mechanical, optical and electronic …

Universality Of Non-Ohmic Shunt Leakage In Thin-Film Solar Cells, Sourabh Dongaonkar, Jonathan D. Servaites, Grayson M. Ford, Stephen Loser, James E. Moore, Ryan M. Gelfand, Hooman Mohseni, Hugh W. Hillhouse, Rakesh Agrawal, Mark A. Ratner, Tobin J. Marks, Mark Lundstrom, Muhammad A. Alam

Birck and NCN Publications

We compare the dark current-voltage (IV) characteristics of three different thin-film solar cell types: hydrogenated amorphous silicon (a-Si:H) p-i-n cells, organic bulk heterojunction (BHJ) cells, and Cu(In,Ga)Se₂ (CIGS) cells. All three device types exhibit a significant shunt leakage current at low forward bias (V< ∼ 0.4) and reverse bias, which cannot be explained by the classical solar cell diode model. This parasitic shunt current exhibits non-Ohmic behavior, as opposed to the traditional constant shunt resistance model for photovoltaics. We show here that this shunt leakage (I_sh), across all three solar cell types considered, is characterized by the following common phenomenological features: (a) voltage symmetry about V = 0, (b) nonlinear (power law) voltage dependence, and (c) extremely weak temperature dependence. Based on this analysis, we provide a simple method of subtracting this shunt current component from …

Analysis Of The Detection Of Organophosphate Pesticides In Aqueous Solutions Using Polymer-Coated Sh-Saw Devices, Arnold Kweku Mensah-Brown

Dissertations (1934 -)

Organophosphate pesticides (OPs) have been found as contaminants in surface and ground waters, soil, and agricultural products. Because OPs are toxic compounds, rapid detection/monitoring of OPs in groundwater is necessary to allow for real-time remediation. Detection of OPs in water has already been demonstrated using poly(epichlorohydrin) [PECH] and polyurethane as the sensing layers. However, the response times were relatively long, hindering real-time monitoring. In this work, a hybrid organic/inorganic chemically sensitive layer [bisphenol A-hexamethyltrisiloxane (BPA-HMTS)] that shows a high degree of partial selectivity for OPs is synthesized, characterized (in terms of the glass transition temperature, T_g, water stability, …

Optimization Of Process Parameters For Reduced Thickness Cigses Thin Film Solar Cells, Shirish A. Pethe

Electronic Theses and Dissertations

With the advent of the 21st century, one of the serious problems facing mankind is harmful effects of global warming. Add to that the ever increasing cost of fuel and the importance of development of clean energy resources as alternative to fossil fuel has becomes one of the prime and pressing challenges for modern science and technology in the 21st century. Recent studies have shown that energy related sources account for 50% of the total emission of carbon dioxide in the atmosphere. All research activities are focused on developing various technologies that are capable of converting sunlight into electricity with …

Growth Of Crystalline Cobalt Ferrite Thin Films At Lower Temperatures Using Pulsed-Laser Deposition Technique, A. Raghunathan, David C. Jiles, Ikenna C. Nlebedim

David C. Jiles

Cobaltferritethin films were grown on SiO2/Si(100) substrates using pulsed-laser deposition technique at substrate temperatures ranging from 250 to 600 °C. Thermal expansion mismatch between the film and substrate appears to have a substantial effect on the magnetic properties of the cobaltferritefilms, due to the large magnetoelastic coupling of cobaltferrite. It was shown in this study, that polycrystalline films with (111)-preferred orientation could be prepared at substrate temperatures as low as 250 °C. The growth of crystalline cobaltferritefilms at such low temperatures indicates the potential to use cobaltferrite for microelectromechanical systemsdevices and sensor applications including integration with a wider range of …

Rf And Structural Characterization Of Srf Thin Films, A.M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J. Spradlin, X. Zhao, D. Gu, H. Baumgart, D. Beringer, R.A. Lukaszew, B. Xiao, K. Seo

Electrical & Computer Engineering Faculty Publications

In the past years, energetic vacuum deposition methods have been developed in different laboratories to improve Nb/Cu technology for superconducting cavities. JLab is pursuing energetic condensation deposition via Electron Cyclotron Resonance. As part of this study, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated. The film surface and structure analyses are conducted with various techniques like X-ray diffraction, Transmission Electron Microscopy, Auger Electron Spectroscopy and RHEED. The microwave properties of the films are characterized on 50 mm disk samples with a 7.5 GHz surface impedance characterization system. This paper …

Microstructure And Electrical Performance Of Sputter-Deposited Hafnium Oxide (Hfo2) Thin Films, Brandon Adrian Aguirre

Open Access Theses & Dissertations

Hafnium oxide (HfO2) based dielectrics have been currently considered as the possible replacements for the traditional gate-oxide (SiO2) of the complementary metal-oxide semiconductor (CMOS) devices. The high dielectric constant, wide band gap, and thermal stability in contact with Si make HfO2 a potential material for application in CMOS devices. The performance of HfO2 as a gate oxide material, however, depends on its quality and interface structure with Si. In this work, HfO2 thin films have been deposited by rf sputtering onto Si(100) substrates under varying growth temperatures (Ts). The objective of the work is to understand the growth and microstructure …

Synthesis And Characterization Of Nanocrystalline (Zr₀.₈₄Y₀.₁₆)O₁.₉₂-(Ce₀.₈₅Sm₀.₁₅)O₁.₉₂₅ Heterophase Thin Films, Aniruddha Kulkarni, Alexander Bourandas, Junhang Dong, Paul A. Fuierer, Hai Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

A new type of nanocrystalline samarium-doped-ceria/yttrium-stabilized-zirconia (SDC/YSZ) heterophase thin film electrolytes was synthesized on MgO and Si substrates by spin coating and thermal treatment of SDC-nanoparticle-incorporated polymeric precursors. In the heterophase films, SDC nanoparticles were uniformly dispersed in a nanocrystalline YSZ matrix. The heterophase structure was stable when fired in air at temperatures up to 850 °C. The nanocrystalline heterophase thin films exhibited electrical conductivities significantly higher than that of the phase-pure YSZ and SDC nanocrystalline thin films at reduced temperatures. The effects of SDC grain size and volume fraction on the electrical conductivity of the heterophase films were also …

Self-Assembly Of Ge Quantum Dots On Si(100)- 2×1 By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Self-assembled Ge quantum dots are grown on Si(100)- 2×1 by pulsed laser deposition. The growth is studied by in situ reflection high-energy electron diffraction and postdeposition atomic force microscopy. After the completion of the wetting layer, transient hut clusters, faceted by different planes, are observed. When the height of these clusters exceeded a certain value, the facets developed into {305} planes. Some of these huts become {305}-faceted pyramids as the film mean thickness was increased. With further thickness increase, dome clusters developed on the expense of these pyramids. © 2005 American Institute of Physics. [DOI: 10.1063/1.1949285]

Investigation Of Nanoporous Thin-Film Alumina Templates, Biswajit Das

Electrical & Computer Engineering Faculty Research

This paper presents the results of a systematic study of the fabrication of thin-film alumina templates on silicon and other substrates. Such templates are of significant interest for the low-cost implementation of semiconductor and metal nanostructure arrays. In addition, thin-film alumina templates on silicon have the potential for nanostructure integration with silicon electronics. Formation of thin-film alumina templates on silicon substrates was investigated under different fabrication conditions, and the dependence of pore morphology and pore formation rate on process parameters was evaluated. In addition, process conditions for improved pore size distribution and periodicity were determined. The template/silicon interface, important for …

Cuin1-Xalxse2 Thin Films And Solar Cells, P. D. Paulson, M. W. Haimbodi, S. Marsillac, R. W. Birkmire, W. N. Shafarman

Electrical & Computer Engineering Faculty Publications

CuIn[sub 1-x]Al[sub x]Se[sub 2] thin films are investigated for their application as the absorber layer material for high efficiency solar cells. Single-phase CuIn[sub 1-x]Al[sub x]Se[sub 2] films were deposited by four source elemental evaporation with a composition range of 0≤x≤0.6. All these films demonstrate a normalized subband gap transmission >85% with 2 µm film thickness. Band gaps obtained from spectroscopic ellipsometry show an increase with the Al content in the CuIn[sub 1-x]Al[sub x]Se[sub 2] film with a bowing parameter of 0.62. The structural properties investigated using x-ray diffraction measurements show a decrease in lattice spacing as the Al content increases. …

Réalisation De Couches Minces De Cualse² Par Recuit De Feuilllets Superposés Cu/Al/Se/Al…, Étude De Conditions De Dépôt, C.O. El Moctar, S. Marsillac, J. C. Bernede, A. Conan, K. Benchouk, A. Khelil

Electrical & Computer Engineering Faculty Publications

Thin layers of Cu/Al/Se/Al/Cu/Al/Se/…/Al/Se sequentially deposited have been annealed half an hour at 855 K. CuAlSe₂ thin films crystallized in the chalcopyrite structure are obtained. The films being contaminated by oxygen, the experimental deposition conditions of the aluminum layer have been improved in order to decrease the atomic concentration of oxygen below 5 at%. Such results can be obtained in vacuum of 10^-4 Pa, when the aluminum deposition rate is 1 nm/s and when the layer is immediately covered after deposition. Films obtained in such a way are nearly stoichiometric with lattice parameters in accordance with the expected …

Cualse² Thin Films Obtained By Chalcogenization, S. Marsillac, K. Benchouk, C. El Moctar, J. C. Bernède, J. Pouzet, A Khellil, M. Jamali

Electrical & Computer Engineering Faculty Publications

CuAlSe₂ thin films have been synthesized by chalcogenization of thin Cu and Al layers sequentially deposited by evaporation under vacuum. It is shown that CuAlSe₂ films are obtained with some Cu₂-_δSe and Se phases present at the surface. These surface phases are suppressed by annealing under vacuum and by chemical etching in a KCN solution. At the end of the process, the XRD spectrum demonstrates that textured CuAlSe₂ films have been obtained with preferential orientation of the crystallites along the (112) direction. The gap of the films is 2.7 eV as expected. The …

Reflection High-Energy Electron-Diffraction Study Of Melting And Solidification Of Pb On Graphite, Z. H. Zhang, P. Kulatunga, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The melting and solidification of Pb thin films on pyrolytic graphite are investigated in situ by reflection high-energy electron diffraction. Thin films with thicknesses of 4-150 monolayers are investigated. The surface morphology of the thin films were studied by scanning electron microscopy. Superheating of the Pb thin films by 4±2 to 12±2 K is observed from diffraction intensity measurements. Upon cooling the substrate, the Pb on graphite is seen to supercool by ∼69±4 K.

Optical And Electrical Properties Of Cualse² Thin Films Obtained By Selenization Of Cu/Al/Cu... Al/Cu Layers Sequentially Deposited, J. C. Bernède, S. Marsillac, C. El Moctar, A. Conan

Electrical & Computer Engineering Faculty Publications

Optical and electrical properties of CuAlSe₂ thin films obtained by selenization of Cu/Al/Cu...Al/Cu layers sequentially deposited have been investigated. It is shown that the expected energy gap (2.67 eV) is measured for well crystallized films, whereas a slightly higher value is measured for films not so well crystallized. Raman diffusion also shows differences between well and poorly crystallized films with peaks corresponding to the reference powder for the former samples. A p-type conductivity is found whatever the crystalline quality of the samples. The conductivity of the films depends also strongly on their crystalline properties. When the films are badly …

Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

Design Of Mask For Striped Filters And Thin-Film Multi-Layer Emissivity Modeling For Multi-Wavelength Imaging Pyrometer, Jitesh Navinchandra Shah

Theses

Multi-Wavelength Imaging Pyrometry (M-WIP) measures thermal radiation of any target (color or gray) in multiple narrow-spectral-regions and can simultaneously determine target temperature and emissivity. One approach for measuring radiation at multiple wavelengths using a 320X244 element Pt-Si SBD infrared camera is to use narrow-band striped filters deposited on a transparent substrate with proper alignment. The major focus of this thesis was the design of a four layer mask for investigating the feasibility of defining three-wavelength striped filters compatible with focal plane array. This mask design allows twelve distinct narrow band striped filter geometries and four test-patterns on a 4-inch silicon …

Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

Synthesis And Characterization Of Lpcvd Silicon Carbide Thin Films For X-Ray Lithography, Mahalingam Bhaskaran

Theses

Amorphous silicon carbide thin films were fabricated using low pressure chemical deposition method with a single liquid precursor, di tertiary butyl silane. The films were deposited for a temperature range of 500-850°C and at different pressures ranging from 0.05 to 1 torr. The growth rate of the films deposited at constant pressure of 0.2 torr with a flow rate of 60 sccm, was found to follow an Arrehenius Behavior in the temperature range of 600 - 675°C, yielding an activation energy of 32.5 k cal mol^-1 . IR spectroscopic study showed an absorption peak centered at 780 cm^{-1 …}

Novel Chemical Preparative Route For Semiconducting Mose2 Thin Films, K. C. Mandal, O. Savadogo

Faculty Publications

No abstract provided.

Electrical Properties Of Hydrogenated Diamond, Sacharia Albin, Linwood Watkins

Electrical & Computer Engineering Faculty Publications

Hydrogen passivation of deep traps in diamond is demonstrated. Current‐voltage (I‐V) characteristics of polycrystalline thin film and bulk diamond were studied before and after hydrogenation. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I‐V characteristics of the samples. The concentration of uncompensated traps was varied systematically by hydrogenation. The concentration of electrically active hydrogen was determined from the I‐V data. It is shown that hydrogenation is an alternative to deep‐level transient spectroscopy, suitable for …

Raman Scattering Characterization Of The Microscopic Structure Of Semi-Insulating Polycrystalline Si Thin Films, D.J. Olego, H. Baumgart

Electrical & Computer Engineering Faculty Publications

Raman scattering experiments were carried out to study the microscopic structure of semi-insulating polycrystalline Si (SIPOS) thin films prepared by low-pressure chemical vapor deposition. The samples contain 18, 25, and 30 at. % of oxygen and after growth they were annealed at 900 and 1000°C for 30 min. The Raman spectra show in the vibrational region of the optical frequencies of Si two bands, which arise from scattering in crystalline grains and disordered forms of Si. The behavior of these bands as a function of oxygen content and annealing temperatures was established in detail. The crystallinelike band peaks below the …