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Articles 1 - 11 of 11

Full-Text Articles in Physics

Photonic Bandgap Materials: Design, Fabrication, And Characterization , Ganapathi S. Subramania Jan 2000

Photonic Bandgap Materials: Design, Fabrication, And Characterization , Ganapathi S. Subramania

Retrospective Theses and Dissertations

The last few decades have seen a tremendous explosion in the area of new synthetic materials. As we begin to better understand the nature of the atomic and molecular bonds it has been possible to systematically search for materials with specific properties thanks to the availability of powerful supercomputers. Due to significant advances in materials synthesis a rich variety of artificial materials whose mechanical, chemical, electronic and optical properties can be suitably tailored can now be produced. Some of the materials (plastics, synthetic fibers, ceramics, alloys etc.) can replace or substitute traditional materials; some others have managed to create new ...


Metallic Photonic Band Gap Structures On Flexible Substrates , Sandhya Gupta Jan 1998

Metallic Photonic Band Gap Structures On Flexible Substrates , Sandhya Gupta

Retrospective Theses and Dissertations

Periodic dielectric and metallic structures have recently generated great interest because they can exhibit a forbidden range of frequency, or a photonic band gap (PBG) where the electromagnetic waves cannot propagate. Since their theoretical prediction in 1987, several applications at frequencies ranging from microwave to optical region have been proposed using these novel structures. This presentation demonstrates the first successful fabrication of flexible metallic PBG structures that show frequency filtering properties at far-infrared frequencies;The metallic PBG filters described here are multi-layered metallic meshes imbedded in a flexible polyimide dielectric. They have a simple, microfabrication-based construction that use alternating dielectric ...


Stability And Electronic Properties Of Amorphous Silicon P-I-N Devices Fabricated Using Ecr Plasma Enhanced Chemical Deposition , Sanjeev Kumar Kaushal Jan 1997

Stability And Electronic Properties Of Amorphous Silicon P-I-N Devices Fabricated Using Ecr Plasma Enhanced Chemical Deposition , Sanjeev Kumar Kaushal

Retrospective Theses and Dissertations

The prime objective of the research was to investigate the fabrication, stability and electronic properties of a-Si:H devices deposited using electron cyclotron resonance (ECR) plasma deposition technique. Both reactive (hydrogen) and non-reactive (helium) gases were used as the primary plasma gas. The reactants generated by the ECR plasma from these gases were allowed to flow towards the substrate, where they reacted with silane to give rise to growth of a-Si:H. In general, we used a high dilution ratio of plasma gas (H2 or He) to silane, about 15:1 to 20:1; for growing a-Si:H. Very high ...


Modeling, Characterization And Integration Of Thin Film Resonator Microsensors , Jie Xia Jan 1996

Modeling, Characterization And Integration Of Thin Film Resonator Microsensors , Jie Xia

Retrospective Theses and Dissertations

There is an increasing demand by using smart and miniaturized microsensors and microtransducers in the areas of automobile, environment Science and analytical chemistry. Thin film microresonators (TFRs), meriting from their small size, higher sensitivity and compatibility with VLSI process, have being investigated as microsensors. Gas or vapor absorbed species, or contacted liquids may perturb resonator mechanical, electrical and piezoelectric properties. In this dissertation, a coupled wave theory is presented and applied to analyze acoustic wave propagation phenomena both in TFR-solid and TFR-liquid phases. A two-dimensional analysis is implemented to compare with a one-dimensional model and experimental results. The analysis and ...


Increasing The Efficiency Of A Piezoelectric Aluminum Nitride Microstrip Resonator By Utilizing High Temperature Superconductors , Edward David Goff Jan 1995

Increasing The Efficiency Of A Piezoelectric Aluminum Nitride Microstrip Resonator By Utilizing High Temperature Superconductors , Edward David Goff

Retrospective Theses and Dissertations

High temperature superconductors have potential applications in the field of microwave devices and circuits. To utilize these materials in such a way as to increase the efficiency of these microwave devices would be beneficial for high efficiency/low noise applications. This dissertation accomplishes the following goals: (1) The design and fabrication of an initial device that increases the quality factor, Q, and therefore the efficiency of a high frequency thin film resonator which uses superconducting metal as the device's electrode, (2) the measurement and characterization of this device, (3) the theoretical calculation and predicted performance of this device, and ...


Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping Jan 1995

Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping

Retrospective Theses and Dissertations

This thesis consists of two different parts: (I) experimental investigations of hydrogenated amorphous silicon substrate n[superscript]+/i/p[superscript]+ solar cells and, (II) fundamental properties of quantum wells with cylindrical geometry and applications to electronics and photonics;Part I. The substrate structural n[superscript]+/i/p[superscript]+ solar cells based on a-Si:H materials are fabricated by a radio frequency (RF) triode geometric plasma enhanced chemical vapor deposition (PECVD) system. The solar cells have been electrically and optically tested. Two different substrates, tin-oxide coated glass and stainless steel foil, are used. An RF magnetron sputtering system is used to ...


A Closed-Form Integration Method For State-Space Time-Domain Analysis Of Electronic Circuits And Systems , Bruce Alan Alspaugh Jan 1994

A Closed-Form Integration Method For State-Space Time-Domain Analysis Of Electronic Circuits And Systems , Bruce Alan Alspaugh

Retrospective Theses and Dissertations

While most traditional circuit simulation programs such as SPICE rely upon numerical integration techniques to perform transient analysis, this dissertation presents an alternative approach that relies on closed-form integration. Traditional numerical approaches offer no hope of finding an analytical solution, even if it is known that the solutions will be in a simple functional form. By using closed-form methods, the computer can find the exact analytical solution to the network and completely avoid problems associated with numerical approximations, determining appropriate integration step sizes, stiff systems of differential equations, or accumulated global error. Computer run time is independent of the amount ...


Characterization And Analysis Of Viscoelastically Loaded Thin Film Piezoelectric Resonators Incorporated In An Oscillator Microsensing System , Ronald Patrick O'Toole Jan 1994

Characterization And Analysis Of Viscoelastically Loaded Thin Film Piezoelectric Resonators Incorporated In An Oscillator Microsensing System , Ronald Patrick O'Toole

Retrospective Theses and Dissertations

In the recent advancement of piezoelectric resonator technology, there has been a large growth in the application of these devices for chemical sensing. These sensors operate by detecting changes in their environment which perturb the electrical - acoustic operation and in turn can be harnessed by means of supporting electronics and signal processing to monitor various processes. Examples include remote environmental monitoring, chemical process control, and commercial gas phase detectors. In this dissertation, the chemical sensing theory and properties of piezoelectric resonators such as the bulk-acoustic wave thin-film resonator (TFR) and the quartz crystal microbalance (QCM) are developed. This analysis concentrates ...


Growth And Characterization Of Polysilicon Films Deposited By Reactive Plasma Beam Epitaxy , Behnam Moradi Jan 1993

Growth And Characterization Of Polysilicon Films Deposited By Reactive Plasma Beam Epitaxy , Behnam Moradi

Retrospective Theses and Dissertations

Polycrystalline silicon was deposited at low temperatures (400-550°C) by using a new technique, reactive plasma beam epitaxy. The technique consists of using an intense flux of hydrogen radicals, generated by an electron cyclotron resonance (ECR) source to promote nucleation and crystallinity at low temperatures. The film structure could be smoothly changed from polysilicon to amorphous by changing the flux of incoming H radicals on the surface of the sample. The flux of hydrogen radicals can be controlled by changing the deposition pressure, with lower pressures leading to a higher H radical flux and greater degree of crystallinity. The effect ...


Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell Jan 1993

Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell

Retrospective Theses and Dissertations

For a receiver system to be considered integrated, the antenna and electronics need to be fabricated on a single semiconductor wafer. To avoid EMI problems, the circuitry must somehow be shielded from the environment where the antenna resides. The required shielding may be accomplished by separating the antenna on one side of the wafer from the electronics on the other side with a conducting ground plane. Energy may be acoustically coupled from the antenna to the circuitry through the ground plane via thin film piezoelectric transducers on either side of the wafer. The radiating side of the wafer would then ...


Frequency Conversion Analysis Of Noise In Heterojunction Bipolar Transistor Oscillators Including Periodically Modulated Noise Sources , Bradley Allen Kramer Jan 1993

Frequency Conversion Analysis Of Noise In Heterojunction Bipolar Transistor Oscillators Including Periodically Modulated Noise Sources , Bradley Allen Kramer

Retrospective Theses and Dissertations

A procedure which may be used to analyze the noise characteristics of HBT oscillators is presented. A large signal model of a HBT is developed based largely on the Gummel-Poon transistor model. A new base-emitter diffusion capacitance model is also generated which shows improved accuracy over conventional bipolar transistor models in characterizing HBTs. The large signal characteristics of the oscillator are then established using a time domain simulator. Conversion matrix theory is applied to the large signal model to generate an equivalent linear oscillator model which accounts for all of the frequency conversion effects which occur due to circuit nonlinearities ...