In this study, the Bragg reflectors deposited by DC and RF magnetron sputtering are composed of alternating layers of high and low acoustic impedance materials which have a thickness of one quarter wavelength at the desired resonance frequency, while the piezoelectric layer, aluminum nitride thin film, was deposited by RF reactive magnetron sputtering. The deposition parameters of Mo and SiO2 thin films are tuned according to the AFM measurement. With the optimal deposition parameters, the cross-sectional SEM images of multilayer Bragg reflector show smooth and clear interfaces which are important criterias for the SMR devices. The frequency responses of SMR show distinct resonant phenomenon near 1.4GHz and 2.5GHz with an excellent noise restraint. It indicates that the Bragg reflector made of Mo/SiO2 is suitable for the fabrication of SMR devices. Furthermore, the two resonant frequencies show that the bulk acoustic wave transmit in two different way, the longitudinal mode and the shear mode. The cause of the shear mode vibration is the tilt of the c-axis of AlN thin films. For c-axis inclined AlN thin films, the longitudinal and the shear mode vibration both exist, and the acoustic wave propagates with different acoustic velocities along the c-axis inclined AlN.

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20 periods AlN/GaN distributed Bragg reflector (DBR) nanorod structure has been grown on Si (111) substrates at 780¢J by plasma-assisted molecular beam epitaxy (PAMBE) under highly N-rich conditions. The AlN/GaN DRB nanorod structure started with 637 nm high GaN nanorod directly grown on Si (111). Diameter of nanorod is around 80 nm. The height of nanorod is around 3.3 £gm, the density of nanorods is around 2¡Ñ1010 cm-2, and the thickness of each layer are around 44 nm and 58 nm for AlN and GaN, respectively. The nanorod had been analyzed by temperature dependent cathodoluminescence (CL), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), X-ray diffraction (XRD) measurement.

The main purpose of this study is focused on the defects within the layers of GaN over AlN thin films which were grown on the substrates of silicon (111) and LiAlO2 (100), respectively. The growth of three sapphire crystals is also addressed. During the epitaxial growth period, the Al pre-deposition time is very important for the defect on AlN/Si, and due to the high stacking fault energy, the partial dislocations in the AlN layers can not be observed. Cracks were found in the GaN films because of the great thermal mismatch between GaN itself and AlN which is up to 25%. Although the lattice mismatch between GaN and LiAlO2 is low, the thermal stress effect still could not be avoided. Cracks also occurred in the GaN films which were grown on LiAlO2 substrates. For the sapphire pulled along [100] direction, the crystal has fewer amounts of bubbles at the lower rotation rate. For the sapphire pulled along [001] direction, the crystal with 4.5 mm/hr pulling rate has cracks along [001] direction, but the crystal with 4.0 mm/hr pulling rate has no cracks inside.

Le résonateur étudié s'insère dans un projet industriel porté par NXP Semiconductors. L'objectif est la réalisation d'un résonateur MEMS RF intégrable en vue de remplacer le quartz dans certaines applications. La compatibilité du procédé de fabrication avec les technologies utilisées par la société et le faible coût de production représentent les principaux enjeux du projet. Le résonateur TFEAR (Thin Film Elongation Acoustic Resonator) est un barreau, constitué d'une superposition de couches minces de type Métal/AlN/Métal. Les propriétés piézoélectriques du nitrure d'aluminium (AlN) sont ainsi exploitées : l'application d'un champ électrique alternatif, parallèle à l'épaisseur du barreau, entraîne une propagation d'ondes acoustiques suivant sa longueur. Les dimensions des résonateurs fabriqués correspondent à des fréquences de résonance comprises entre 10MHz et 50MHz. Cette thèse s'intéresse la modélisation et à la caractérisation électrique du résonateur TFEAR. Les modèles théoriques sont développés par simulations numériques 3D et par calculs analytiques 1D. Le comportement électrique du TFEAR est décrit par un schéma équivalent, dont les éléments sont exprimés en fonction des paramètres physiques et des pertes des matériaux le constituant. Un facteur de qualité de 2250 sur un TFEAR résonant à 25,79MHz et dont la résistance motionnelle est de 2,1 kOhms a été relevé. Ces mesures ont été complétées par la caractérisation des paramètres physiques de la couche piézoélectrique. Par exemple, des valeurs de coefficient piézoélectrique d33f atteignant 2,6 pm/V ont été relevées (pour un maximum théorique de 3,93 pm/V) / The studied resonator is part of an industrial project carried by NXP Semiconductors. The objective is the realization of a integrable RF MEMS resonator in order to replace quartz in some applications. The compatibility of the manufacturing process with the technologies used by the company and low cost production represent the main challenges of the project. The resonator TFEAR (Thin Film Elongation Acoustic Resonator) is a bar, consisting of a superposition of thin film type Metal/AlN/metal. The piezoelectric properties of aluminum nitride (AlN) are exploited : the application of an alternating electric field, parallel to the thickness of the bar, resulting in propagation of acoustic waves along its length. The sizes of the manufactured resonators correspond to resonant frequencies between 10MHz to 50 MHz. This thesis focuses on modeling and electrical characterization of the TFEAR resonator. The models are developed by 3D numerical simulations and by 1D analytical calculations. The electrical behavior of TFEAR is described by an equivalent circuit which elements are expressed in terms of physical parameters and losses of the constituent materials. A quality factor of 2250 on a 25.79MHz resonant TFEAR which motional resistance is 2.1 kOhms has been noticed. These measurements were completed by the characterization of the physical parameters of the piezoelectric layer. For example, piezoelectric coefficient d33;f values were recorded up to 2.6 pm/V (for a theoretical maximum of 3.93pm/V)

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14627号 / 工博第3095号 / 新制||工||1460(附属図書館) / 26979 / UT51-2009-D339 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 川上 養一, 教授 髙岡 義寛, 准教授 須田 淳 / 学位規則第4条第1項該当

This study is to develop the manufacturing processes of thin film bulk acoustic device by MEMS technology, including lithography, wet etching, dry etching and rf Magnetron sputtering.LPCVD is used to deposit SiNx as the membranes and mask for etching of silicon wafer. The electrodes of molybdenum metal (Mo) and piezoelectric layer of aluminum nitride (AlN) on top side are prepared by dc and rf sputtering,respectively. The acoustic cavity on back side is achieved by 30%wt 100¢J KOH solution and reactive ion etching (RIE). In this study, the crystallography of the coated films was analyzed by X-ray diffraction. The surface and cross-sectional morphologies of AlN films were investigated by electron microscope. The piezoelectric layer of AlN thin film prepared by rf magnetron sputtering shows the highly c-axis preferred orientation and fine morphology under the optimal sputtering parameters of rf power of 200W, sputtering pressure of 3 mTorr, substrate temperature of 400¢J and nitrogen concentration of 25%. The frequency responses of fabricated FBAR devices are evaluated using the Hewlett-Packard 8720-ET network analyzer. Moreover, the optimal thickness of 1500Å SiNx film prepared by LPCVD revealed the excellent masking effect and non-stress for membrane. The yield for the fabrication of acoustic cavity is maximum of 85% can be achieved by using the combined etching steps of wet and dry etching.

AlN thin films grown on GaN/Sapphire substrate by RF magnetron sputtering technique with AlN target has been studied. Simple MIS capacitor was fabricated in order to evaluate the electrical properties of AlN films that played as a insulator. Various microstructures of AlN thin films can be obtained by controlling the growth parameters, such as sputtering powers, sputtering distances and working pressure. The microstructures of the AlN films were examined by X-ray diffraction. The observation of the surface morphology ,the distribution of defects and the interface of AlN/GaN were performed by transmission electron microscopy. The results showed that the amorphous AlN thin films were obtained with a 21cm long sputtering working distance and under the 100W sputtering power and 8mtorr working pressure conditions. The results of the C-V measurement indicated that the MIS device demonstrated a capacitor behavior, however a large leak current showed up in the end. The quality of the AlN films and the process procedures of MIS device still need be improved further.

Abstract AlN thin films grown on Si¡BGlass¡BSiO2 and Si3N4 substrate by RF magnetron sputtering technique with AlN target has been studied.Room temperature growth was applied to this study.During thin film growing, sputtering work pressure, sputtering power, sputtering working distance and sputtering time are those key parameters to be adjusted in order to highly C-axis prefer orientation AlN thin films. The microstructures of the AlN films were examined by x-ray diffraction. TEM was adopted to observe grain growth of the AlN films. The results was compared with the results of reactive RF magnetron sputtering. The results of the X-ray patterns showed that the strong C-axis prefer orientation of the AlN films were obtained with AlN target. in a 17¢Q long sputtering working distance condition, chemical composition of substrate can help to growth of AlN films. The column structures of AlN films can be observed by TEM.

Arcanobacterium haemolyticum, a Gram-positive bacterium, is an under-reportedagent of disease, causing pharyngitis, wound infections and a variety of invasive diseases.This work characterized a known A. haemolyticum toxin, phospholipase D (PLD), anddetermined its possible role in bacterial virulence. In addition, a novel toxin, arcanolysin(ALN), was identified and characterized. A draft genome sequence was determined andseveral additional virulence factors that may aid in disease pathogenesis were identified.PLD was present in all strains of A. haemolyticum tested, and was expressedmaximally during logarithmic growth. Recombinant PLD caused lipid raftrearrangement on the surface of HeLa cells in a dose-dependent manner. Thisrearrangement allowed maximal bacterial adhesion to the host, with a pld knockoutadhering only 39.7% to HeLa cells as compared to wildtype. Loss of production of PLDdid not affect bacterial invasion. However, PLD expressed by intracellular bacteria wascytotoxic to host cells, as determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium/phenazine methosulfate(MTS/PMS) viability assays. PLD caused host cell death via necrosis as determined bytransmission electron microscopy. PLD did not induce apoptosis, as caspases 3/7 and 9were not elevated in HeLa cells infected with wildtype A. haemolyticum.A. haemolyticum also expresses a Cholesterol-Dependent Cytolysin (CDC), ALN.Like pld, aln was present in all strains tested. ALN displays a variant undecapeptide andan unusual N-terminal extension not found in most other CDCs. Recombinant ALN11shows significantly increased activity against cultured cells and erythrocytes of humanorigin, compared with intermediate activity on rabbit and hamster cells, and low to noactivity on bovine and ovine cells as measured by hemolysis, cytotoxicity and membranebinding assays. ALN was less inhibited by free cholesterol when compared with otherCDCs, indicating the possibility of alternative receptor binding.The A. haemolyticum genome was sequenced to >20X coverage, and assembled to50 contigs covering ~95% of the genome. The genome is ~1.95Mb with a mol %G+C of53.1% and contained no plasmids. pld and aln have a reduced mol %G+C of 47.2% and46.5%, respectively, indicating the possibility of gene acquisition by horizontal transfer.Initial bioinformatics analysis identified genes encoding a protease, an extracellularDNase, two neuraminidases and three fimbrial biosynthetic operons were also identifiedwithin the genome.