Abstract: A ball end mill in which a ball end cutting edge (3) has a convex shape in a tool rotation direction with respect to a line connecting a rotation center (O) and a radially outer end (3o) of the ball end cutting edge (3), in a front view of the tool. In the ball end mill, a rake angle (?) of each portion of the ball end cutting edge (3) is set in a range from ?10° to 0°, and the negative value of the rake angle (?) is increased from a tip of the ball end cutting edge (3) and a radially outer end (3o) of the ball end cutting edge (3) toward a middle point in the radial direction, and is maximized at approximately the middle point in the radial direction.

Abstract: A bismuth-based glass composition according to the present invention contains Bi2O3, B2O3 and ZnO, wherein the bismuth-based glass composition has a Bi2O3 content of 55 to 80 mass % and further contains 0.1 to 5 mass % of at least one of SrO and BaO as an RO component. Preferably, the bismuth-based glass composition according to the present invention has a linear expansion coefficient of (65 to 95)×10?7/° C. at 30 to 300° C. and a softening point of 450 to 530° C. There is a problem that bismuth-based glasses are often structurally unstable, are crystalized during firing and lose their flowability due to such crystallization so that it is difficult for the bismuth-based glasses to secure good adhesion strength and airtightness. By contrast, the bismuth-based glass composition according to the present invention is transparent and is less likely to be crystallized during firing.

Abstract: A ball end mill in which a ball end cutting edge (3) has a convex shape in a tool rotation direction with respect to a line connecting a rotation center (O) and a radially outer end (3o) of the ball end cutting edge (3), in a front view of the tool. In the ball end mill, a rake angle (?) of each portion of the ball end cutting edge (3) is set in a range from ?10° to 0°, and the negative value of the rake angle (?) is increased from a tip of the ball end cutting edge (3) and a radially outer end (3o) of the ball end cutting edge (3) toward a middle point in the radial direction, and is maximized at approximately the middle point in the radial direction.

Abstract: A first buffer layer is formed on a substrate at a lower temperature than a single-crystal-growth-temperature, one or more of a layer composed of a nitride containing neither Ga nor In, a layer which has two or more thin films having different moduli of elasticity cyclically laminated therein, and a layer having an Al composition ratio which decreases and a Ga composition ratio which increases in a direction from the first buffer layer to a device-constituting layer are formed as a second buffer layer on the first buffer layer at the single-crystal-growth-temperature, and a device-constituting layer composed of a nitride semiconductor is formed on the second buffer layer.

Abstract: A first buffer layer is formed on a substrate at a lower temperature than a single-crystal-growth-temperature, one or more of a layer composed of a nitride containing neither Ga nor In, a layer which has two or more thin films having different moduli of elasticity cyclically laminated therein, and a layer having an Al composition ratio which decreases and a Ga composition ratio which increases in a direction from the first buffer layer to a device-constituting layer are formed as a second buffer layer on the first buffer layer at the single-crystal-growth-temperature, and a device-constituting layer composed of a nitride semiconductor is formed on the second buffer layer.

Abstract: This invention provides a light-emitting diode which is capable of extracting white light, manufactured readily and highly reliable. The light-emitting diode is fabricated by laminating a buffer layer 2, an Si (silicon)-doped GaN fluorescent layer 3, an n-GaN layer 4, an MQW emission layer 5 and a p-GaN layer 6 on a sapphire substrate 1 in this order. The Si-doped GaN fluorescent layer 3 is doped higher concentration of Si (silicon) than a conventional Si-doped GaN layer with sufficient good crystallinity. Such a Si-doped GaN fluorescent layer is excited by blue light generated in the MQW emission layer and emits yellow light. The yellow light is the complement for the blue light generated in the MQW emission layer. White light can be obtained by blending and extracting both of blue light and yellow light.

Abstract: This invention provides a light-emitting diode which is capable of extracting white light, manufactured readily and highly reliable. The light-emitting diode is fabricated by laminating a buffer layer 2, an Si (silicon)-doped GaN fluorescent layer 3, an n-GaN layer 4, an MQW emission layer 5 and a p-GaN layer 6 on a sapphire substrate 1 in this order. The Si-doped GaN fluorescent layer 3 is doped higher concentration of Si (silicon) than a conventional Si-doped GaN layer with sufficient good crystallinity. Such a Si-doped GaN fluorescent layer is excited by blue light generated in the MQW emission layer and emits yellow light. The yellow light is the complement for the blue light generated in the MQW emission layer. White light can be obtained by blending and extracting both of blue light and yellow light.

Abstract: A first buffer layer is formed on a substrate at a lower temperature than a single-crystal-growth-temperature, one or more of a layer composed of a nitride containing neither Ga nor In, a layer which has two or more thin films having different moduli of elasticity cyclically laminated therein, and a layer having an Al composition ratio which decreases and a Ga composition ratio which increases in a direction from the first buffer layer to a device-constituting layer are formed as a second buffer layer on the first buffer layer at the single-crystal-growth-temperature, and a device-constituting layer composed of a nitride semiconductor is formed on the second buffer layer.

Abstract: The present invention provides an electrode making good ohmic contact with an n-type nitride semiconductor without requiring heat treatment at high temperature, wherein an aluminum layer, a silicon layer, a nickel layer and a gold layer are laminated in this order on an n-type gallium nitride based semiconductor, to form an n-type electrode.