Physics Commons^™

Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey

Theses and Dissertations

A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.

Plasmonic And Photonic Designs For Light Trapping In Thin Film Solar Cells, Liming Ji

Graduate Theses and Dissertations

Thin film solar cells are promising to realize cheap solar energy. Compared to conventional wafer cells, they can reduce the use of semiconductor material by 90%. The efficiency of thin film solar cells, however, is limited due to insufficient light absorption. Sufficient light absorption at the bandgap of semiconductor requires a light path more than 10x the thickness of the semiconductor. Advanced designs for light trapping are necessary for solar cells to absorb sufficient light within a limited volume of semiconductor. The goal is to convert the incident light into a trapped mode in the semiconductor layer.

In this dissertation, …

Pulse Sharpening Effects Of Thin Film Ferroelectric Transmission Lines, Robert J. Sleezer

Graduate Theses and Dissertations

Advances in material science have resulted in the development of electrically nonlinear high dielectric thin film ferroelectrics, which have led to new opportunities for the creation of novel devices. This dissertation investigated one such device: a low voltage nonlinear transmission line (NLTL). A finite element simulation of ferroelectric transmission lines showed that NLTLs are capable of creating shockwaves. Additionally, if the losses are kept sufficiently low, it was shown that voltage gain should be possible. Furthermore, a method of accounting for material dispersion was developed. Results from simulations including material dispersion showed that temporal solitons might be possible from a …

Piezomagnetism In Epitaxial Cr2o3 Thin Films And Spintronic Applications, Sarbeswar Sahoo, Christian Binek

Christian Binek

Stress-induced perturbation of the antiferromagnetic long-range order in epitaxially grown Cr2O3 thin films gives rise to pronounced piezomagnetism and a significant reduction of the antiferromagnetic ordering temperature. The temperature dependence of the piezomagnetic moment measured by superconducting quantum interference device magnetometry reveals a power law behaviour with a critical exponent 2B=0.66 in accordance with the Ising anisotropy of a three-dimensional system. The observed shift of the Neel temperature allows estimating the internal lateral stress which is in excellent agreement with an independent estimate based on the elastic properties of Cr2O3 and the lattice mismatch at the interface between the sapphire …

Electron Microscopy Characterization Of Vanadium Dioxide Thin Films And Nanoparticles, Felipe Rivera

Theses and Dissertations

Vanadium dioxide (VO_2) is a material of particular interest due to its exhibited metal to insulator phase transition at 68°C that is accompanied by an abrupt and significant change in its electronic and optical properties. Since this material can exhibit a reversible drop in resistivity of up to five orders of magnitude and a reversible drop in infrared optical transmission of up to 80%, this material holds promise in several technological applications. Solid phase crystallization of VO_2 thin films was obtained by a post-deposition annealing process of a VO_{x,x approx 2} amorphous film sputtered on an amorphous silicon dioxide (SiO_2) …

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 …

The Composition Dependence Of The Optical Band Gap In Ge Doped Se-Te Glassy Alloy, Mainika Kapoor, Nagesh Thakur

Turkish Journal of Physics

Bulk glasses with the chemical composition (Se_{80}Te_{20})_{100-x}Ge_x (x = 0, 2, 4, 6) have been prepared from high purity constituent elements. Fragments of the bulk glasses are used to deposit thin films by vacuum thermal evaporation and compositional dependence of the optical and physical properties have been studied. It has been found that optical absorption is due to indirect transition and the optical band gap E_g increases with increasing Ge content in Se-Te glassy alloy. The relationship between the E_g and chemical composition is discussed in terms of cohesive energy and co-ordination number.

Effect Of Zinc Incorporation On The Density Of Defect States In A-Se_{85}Te_{15} Glassy Alloy, Shikha Shukla, Santosh Kumar

Turkish Journal of Physics

Present work incorporates the study of d.c. conductivity measurements at high electric fields in vacuum evaporated thin films of Se_{85-x}Te_{15}Zn_x (x = 0, 2, 4, 6 and 10) glassy alloys. Current-Voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behavior is observed. However, at high electric fields (E \sim 10^4 V/cm), non ohmic behavior is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, …

Hydrogen Implantation Effects On The Electrical And Optical Properties Of Inse Thin Films, Atef Fayez Qasrawi, Khaled Faisal Ilaiwi, Antonio Polimeni

Turkish Journal of Physics

The effects of hydrogen ion implantation on the structural, electrical and optical properties of amorphous InSe thin films have been investigated. X-ray diffraction analysis revealed no change in the structure of the films. An implantation of 7.3 x 10^{18} ions/cm^2 decreased the electrical conductivity by three orders of magnitude at 300 K. Similarly, the conductivity activation energy, which was calculated in the temperature range of 300-420 K, decreased from 210 to 78 meV by H-ion implantation. The optical measurements showed that the direct allowed transitions energy band gap of amorphous InSe films has decreased from 1.50 to 0.97 eV by …

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.

Synthesis Of Barium Oxide Nanorod By Chemical Bath Deposition, Gopalakrishnan Suresh, Putta Narasimhan Nirmala

Turkish Journal of Physics

We report on the control of nanocrystal sizes in barium oxide nanorods prepared by chemical bath deposition technique. Barium chloride and potassium hydroxide are used as source materials to obtain barium oxide films. Different chemical baths are used to study changes in the structures of the BaO films The effect of hydrazine hydrate on growth of these films has been studied. The results reveal that the additive played a very important role on crystalline size and shape.