Physics Commons^™

Surface Phenomena On The Tin-Dioxide Polycrystalline Layers, Andrei A. Fluerasu

Theses

Polycrystalline tin-dioxide is widely used in the detection of reducing gases (such as H₂, CO, CH₄, C₂H₅OH,...) in air by measuring its conductivity changes. The advantage of gas sensors based on such sensing devices is low cost and high sensitivity. In contrast to their widespread applications and to their successful empirical research and development work, the present understanding of the chemical sensing mechanisms is still immature.

In this thesis, for gas sensors based on thick and porous tin-dioxide layers, a study of the response function upon variation of the partial pressure of …

Degradation And Breakdown In Ultra-Thin Silicon Oxides, Christopher Franck

Theses

Emerging trends in the semiconductor device industry call for detailed knowledge of the properties of devices whose dimensions are small enough to exploit Quantum Mechanical effects. This thesis presents a complete picture of oxide degradation in MOS direct tunnel diodes (t0 <3.4 nm). It is demonstrated that for structures fabricated at different facilities and stressed with either gate or substrate injection, a universal degradation mode is revealed which is manifested as the build up of positive charge in the oxide. The data gathered demonstrates that the positive charging phenomena in sub-3.5 nm oxides is independent of oxide thickness, and is characterized by a voltage threshold and two-regime temperature dependence. Further, the catastrophic failure, or breakdown, of these oxides was studied and the strongest evidence to date is presented which links the positive charging phenomena to the oxide breakdown. This thesis concludes with the presentation of a novel device design which can exploit the properties of degradation and breakdown, in thin oxides, to achieve an EEPROM memory cell of superior endurance.

Design And Fabrication Of A Miniature Pressure Sensor Head Using Direct Bonded Ultra-Thin Silicon Wafers, Chad Eugene Statler

Theses

A miniature pressure sensor head is designed and fabricated using an ultra-thin silicon membrane directly bonded to an excimer laser micromachined substrate. The pressure sensor head has its intended implementation as part of an optically interrogated device with sensitivity to pressures ranging from 0.5 to 4.0 MPa. The pressure range design is shown to be easily adjusted by tailoring the thickness of the membrane wafer. The fabrication process features numerous advantages over existing pressure sensor construction technology including a maskless procedure and no chemical etching or mechanical thinning necessary to form the membrane after bonding. An optic lever is constructed …

Investigation Of Potential Oxygen Defect Mechanism Of Persistent Photoconductivity And Photoinduced Superconductivity In Yba2cu3ox, Denise Catherine Chew

Theses

In this thesis work, we conclude that oxygen vacancy defects play a fundamental role in the PPC/PISC mechanism and identify the oxygen defects as F centers (an oxygen vacancy which traps two electrons) or F⁺ centers. Also, the correlation between the peaks observed in the luminescence spectra and those observed in the wavelength dependence of PPC suggest that the photogeneration of charges and their annihilation via luminescent recombination occur in the same level (Cu-O chains) of the YBa₂Cu₃O_x crystal. Previous models had assigned the peaks in the PPC excitation spectrum to charge transfer in …