A composite substrate of the present disclosure is a composite substrate comprising a piezoelectric substrate and a sapphire substrate which are directly bonded, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the bonding surface region including the bonding surface of the sapphire substrate bonded to the piezoelectric substrate is less than 1.5. The piezoelectric device of the present disclosure comprises the composite substrate. A method for manufacturing the composite substrate of the present disclosure comprises a step of preparing a piezoelectric substrate and a sapphire substrate, a step of heat-treating the sapphire substrate in a reducing atmosphere or in a vacuum, and a step of directly bonding the piezoelectric substrate to the sapphire substrate.

The purpose of quartz homeotypes grown epitaxially on beta quartz for use in pressure sensors or accelerometers is to be able to drastically cut down production costs on otherwise expensive or time-consuming to grow crystals that are necessary in various industrial applications. This is done via epitaxial growth of quartz homeotypes across the whole surface of a sample of beta quartz, an easily accessible and high temperature capable crystal. This invention also applies to the epitaxial application of piezoelectric material atop a piezoelectric crystal for the purpose of altering its piezoelectric coefficient and the epitaxial application of a piezoelectric crystal atop a host crystal for the purpose of increasing its insulation resistance.

The purpose of quartz homeotypes grown epitaxially on beta quartz for use in pressure sensors or accelerometers is to be able to drastically cut down production costs on otherwise expensive or time-consuming to grow crystals that are necessary in various industrial applications. This is done via epitaxial growth of quartz homeotypes across the whole surface of a sample of beta quartz, an easily accessible and high temperature capable crystal. This invention also applies to the epitaxial application of piezoelectric material atop a piezoelectric crystal for the purpose of altering its piezoelectric coefficient and the epitaxial application of a piezoelectric crystal atop a host crystal for the purpose of increasing its insulation resistance.

Crystals having a modified regular tetrahedron shape are provided. Crystals preferably have four substantially identical triangular faces that define four truncated vertices and six chamfered edges. The six chamfered edges can have an average length of l, and an average width of w, and 8?l/w?9.5.

Crystals having a modified regular tetrahedron shape are provided. Crystals preferably have four substantially identical triangular faces that define four truncated vertices and six chamfered edges. The six chamfered edges can have an average length of l, and an average width of w, and 8?l/w?9.5.

The purpose of diffusion assisted crystal hydrothermal growth is to facilitate a greatly increased crystal growth rate that would save time that is precious in such a material and manpower costly process. The assisted crystal growth itself requires the utilization of a piezoelectric shaker connected to the autoclave in which most industrial hydrothermal crystals are grown. The waveform can be modulated to induce transport of nutrient in a singular direction, customized to the topology of the apparatus. As it stands currently, the growth of most crystals that require autoclaves for their production can take anywhere from 3 months to up to 2 years, and accordingly carries many costs, particularly electricity and supervision of the autoclave(s), and other issues that may arise during the growth. While the product of this labor results in high-quality crystals, in reality, these are not at all what is needed outside of the laboratory environment. Using the assisted crystal hydrothermal growth process, average crystal growth can be cut in half, with the resulting crystals consequently being of a slightly lower quality, though still sufficient for most engineering purposes. Another advantage of using a piezoelectric shaker is that an additional sensor can be added to the autoclave to monitor the health of the autoclave using trending data obtained during the growth.

The purpose of diffusion assisted crystal hydrothermal growth is to facilitate a greatly increased crystal growth rate that would save time that is precious in such a material and manpower costly process. The assisted crystal growth itself requires the utilization of a piezoelectric shaker connected to the autoclave in which most industrial hydrothermal crystals are grown. The waveform can be modulated to induce transport of nutrient in a singular direction, customized to the topology of the apparatus. As it stands currently, the growth of most crystals that require autoclaves for their production can take anywhere from 3 months to up to 2 years, and accordingly carries many costs, particularly electricity and supervision of the autoclave(s), and other issues that may arise during the growth. While the product of this labor results in high-quality crystals, in reality, these are not at all what is needed outside of the laboratory environment. Using the assisted crystal hydrothermal growth process, average crystal growth can be cut in half, with the resulting crystals consequently being of a slightly lower quality, though still sufficient for most engineering purposes. Another advantage of using a piezoelectric shaker is that an additional sensor can be added to the autoclave to monitor the health of the autoclave using trending data obtained during the growth.

Vacuum ultraviolet light with a wavelength of 200 nm or less is applied on the joining surfaces of first and second workpieces made from a crystal substrate and a glass substrate, or a glass substrate and a glass substrate from a light irradiation unit. The workpieces are conveyed to a workpiece cleaning and laminating mechanism by a conveyance mechanism, the joining surfaces are subjected to mega-sonic cleaning as needed, and the workpieces are aligned with the joining surfaces thereof facing each other, and laminated such that the joining surfaces are in contact with each other. After being laminated, the laminated workpieces are conveyed to a workpiece heating mechanism and heated to increase the workpiece temperature to a predetermined temperature, and this temperature is maintained until joining is completed. The laminated workpieces are brought into a thermally expanded state upon heating, and are joined in this state.

Vacuum ultraviolet light with a wavelength of 200 nm or less is applied on the joining surfaces of first and second workpieces made from a crystal substrate and a glass substrate, or a glass substrate and a glass substrate from a light irradiation unit. The workpieces are conveyed to a workpiece cleaning and laminating mechanism by a conveyance mechanism, the joining surfaces are subjected to mega-sonic cleaning as needed, and the workpieces are aligned with the joining surfaces thereof facing each other, and laminated such that the joining surfaces are in contact with each other. After being laminated, the laminated workpieces are conveyed to a workpiece heating mechanism and heated to increase the workpiece temperature to a predetermined temperature, and this temperature is maintained until joining is completed. The laminated workpieces are brought into a thermally expanded state upon heating, and are joined in this state.

Crystals having a modified regular tetrahedron shape are provided. Crystals preferably have four substantially identical triangular faces that define four truncated vertices and six chamfered edges. The six chamfered edges can have an average length of l, and an average width of w, and 8?l/w?9.5.