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This paper reviews the analytical strategy employed in conventional p-n junction. Then it goes through the analysis of magnetic p-n junction in the same strategy, which makes the review of magnetic p-n junction succinct. I-V equation of magnetic diode is the result of the p-n junction analysis. However, of great importance is to form an acceptable ohmic contact on magnetic diode, which is assumed to be ideal during the magnetic p-n junction analysis. The paper moves on to ohmic contact for magnetic diode, with the example of GaN based magnetic material. With the calculation of the shift of Fermi level in n-GaN with band splitting, conventional ohmic contact structure for n-GaN can be employed to magnetic n-GaN. Experiments from one group prove it. Ohmic contact optimization experiment on n-GaN is present. Ni/Au deposition on n-GaN shows an acceptable ohmic contact. The outlook part points out that the way for research on Schottky diode on magnetic material is partially paved by contents included in this paper.

Microstructure plays a fundamental role in thin film technology, especially regarding the phase stability of a multi-layer ohmic contact stack. Preventing the solid-state reaction between layers is possible if a suitable diffusion barrier material can be inserted between them that is compatible with the manufacturing process, typically involving deposition by magnetron sputtering and patterning by selective chemical etching. However, the microstructural characteristics of sputtered films facilitate interdiffusion at temperatures far below the scale at which bulk materials begin to react. Diffusivities along grain boundaries and other extended defects dominate at lower temperatures, and in thin films, such defects are typically abundant. A polycrystalline barrier layer fails to prevent grain boundary diffusion and the onset of unwanted reactions because the barrier layer's microstructure, as well as its thermodynamic compatibility with the stack, determines its effectiveness. This dissertation discusses the development and implementation of a sputter deposition process for improving high temperature phase stability in a platinum electrode contact metallization to p-doped silicon. Experiments on stacks with a polycrystalline Ti diffusion barrier scheme yield proof that this barrier fails in non-oxidizing ambient when inhomogeneous eruptions of PtSi form at pinhole centers of rapid interdiffusion at 525 ◦C. Fabrication and testing of stacks with two new barrier schemes follows under competing microstructural engineering strategies: (1) Addition of a small layer of C adjacent to the Ti barrier could clog its grain boundaries and suppress diffusion along them, and (2) exchanging Ti with amorphous Ta-Si-N might curb interdiffusion by removing the presence of grain boundaries from the fundamental structure of the barrier material. The addition of C was not found to improve the phase stability of the stack, but the Ta-Si-N barrier inhibits interdiffusion of the electrode and substrate up to 700 ◦C in Ar-H2 ambient. However, when interdiffusion is suppressed in the stack, additional phenomena limit phase stability. Morphological degradation in both the Pt and PtSi layers occurs. More critically, catastrophic delamination of the Pt electrode ensues in oxidizing ambient. An adhesion layer of Ti mitigates the delamination problem, but bubbles form between the barrier and electrode layers. The delamination problem associated with Ta-Si-N cannot be suppressed due to the inherently strong oxidative kinetics of the material.

Dissertation (Ph.D.)--Auburn University, 2009. / Abstract. Includes bibliographic references (p.139-151).

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xii, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 85-92).

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 66-72).

Ce travail consiste en l’étude de la faisabilité de l’application du chauffage ohmique aux opérations de fermentation et de cuisson de la pâte à pain, dans l’objectif d’une production de pain de mie sans croûte. Les caractéristiques de la pâte ont été étudiées, et principalement l’évolution de sa conductivité électrique – moteur de la génération de chaleur en chauffage ohmique. La conductivité électrique est très fortement dépendante des teneurs en sel et en eau de la pâte. Elle augmente également avec la température, mais diminue avec la porosité de la pâte et lors de la gélatinisation de l’amidon. Des équations simples ont pu être déterminées pour son calcul. Un premier modèle thermique a été développé afin de mieux comprendre la formation de gradients de température au sein du produit.Un prototype de four ohmique a été construit, permettant de réaliser à la fois la fermentation et la cuisson de pain de mie sans croûte. L’utilisation du chauffage ohmique permet une réduction significative de la phase de latence et donc du temps de fermentation. Une analyse d’images par tomographie rayons X a montré une porosité plusdéveloppée dans le produit fini, de même qu’une croissance des pores plus importante dans la partie supérieure du pain, contrairement à une cuisson conventionnelle.L’utilisation du chauffage ohmique en panification peut mener à des gains énergétiques potentiels d’un facteur 10. Les rendements énergétiques du procédé ont été évaluéssur gel de tylose, et sont comparables aux valeurs observées par de précédents auteurs. Enfin, un modèle numérique simplifié de transfert de chaleur et de matière a été développé, dans le but d’être employé comme outil prédictif lors d’une cuisson de pain par chauffage ohmique. / This work aims at studying the feasibility of applying ohmic heating to the proofing and baking steps of bread dough, for an objective of crustless bread production. The characteristics of the dough were studied, and mainly the evolution of its electrical conductivity – keyvariable of the heat generation in ohmic heating. The electrical conductivity is highly dependent on the salt and water contents of the dough. It also increases with the temperature, but decreases with the porosity of the dough and during the starch gelatinization step. Simple equations were used to calculate its evolution. A first thermal model was developed to understand better the formation of temperature gradients in the product.An ohmic oven prototype was built in order to realize proofing and baking of crustless bread in the same apparatus. The use of ohmic heating leads to a significant decrease of the lag time and therefore of the proofing time. An X-ray tomography image analysis showed a higher development of the porosity in the final product when using ohmic heating, as well as a more developed network in the upper part of the bread, contrary to a conventional baking.The use of ohmic heating may lead to potential energy savings of a factor of 10. The energy rates of the process were calculated using a gel of tylose, and were in the range of what could be observed by previous authors. Finally, a simplified numerical model of heat and mass transfer was developed, to be used as a predictive tool during the baking of bread by ohmic heating

Master of Science / Food Science Institute / Fadi M. Aramouni / Ohmic heating for the food industry consists of using electrical energy to heat foods as a method of preservation, which can in turn be used for microbial inactivation or several other processes such as pasteurization, extraction, dehydration, blanching or thawing. Few studies have been conducted on the usefulness of this environmentally friendly processing technique. Due to the lack of sufficient information on research into ohmic heating for the food industry, a few of the published studies are discussed here in detail. This report also focuses on self-conducted research using ohmic heating to determine its effect on Lactobacillus acidophilus inactivation versus conventional heating. Lactobacillus acidophilus was inoculated into MRS broth and incubated for 24 hours. The sample was then inoculated into sterile buffer at a dilution rate of 1:100. Samples of the diluted culture were subjected to either low voltage (18 V) or conventional heating (300°C) over a hotplate stirrer. Temperature was monitored on test and control samples to achieve an endpoint of 90°C. Samples were taken at regular intervals, plated onto MRS agar and incubated for 72 hours at 35°C to compare plate count expressed as colony forming units per milliliter (cfu/mL). Temperature was uniform throughout the ohmically heated sample and reached the endpoint more quickly than the conventionally heated sample, which also had cold spots. The total plate count at the end of the experiment was less for the ohmically heated sample versus the conventionally heated sample. Ohmic heating was more effective in inactivation of Lactobacillus acidophilus than conventional heating, most likely due to the more rapid and uniform heating of the sample, and possible electroporation of the cells.

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