A method for forming a lithium niobate- or lithium tantalum-based (LN/LT) layer includes providing a silicon-based substrate, forming nucleation layer on the substrate, and forming the LN/LT layer by epitaxy on the nucleation layer. The nucleation layer is chosen based upon a III-N material. The nucleation layer may be used in a surface acoustic wave device.

A method for forming a lithium niobate- or lithium tantalum-based (LN/LT) layer includes providing a silicon-based substrate, forming nucleation layer on the substrate, and forming the LN/LT layer by epitaxy on the nucleation layer. The nucleation layer is chosen based upon a III-N material. The nucleation layer may be used in a surface acoustic wave device.

A self-supporting substrate includes a first nitride layer grown by hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A self-supporting substrate includes a first nitride layer grown by hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A film structure comprises a substrate and a buffer film formed on the substrate. The substrate is a 36° to 48° rotated Y-cut Si substrate, or the substrate is a SOI substrate including a base substance made of the 36° to 48° rotated Y-cut Si substrate, an insulating layer on the base substance, and a SOI layer made of a Si film on the insulating layer, and a mirror index of a crystal plane of an upper surface of the SOI layer is equal to a mirror index of a crystal plane of an upper surface of the base substance. The buffer film includes ZrO.sub.2 epitaxially grown on the substrate.

A film structure comprises a substrate and a buffer film formed on the substrate. The substrate is a 36° to 48° rotated Y-cut Si substrate, or the substrate is a SOI substrate including a base substance made of the 36° to 48° rotated Y-cut Si substrate, an insulating layer on the base substance, and a SOI layer made of a Si film on the insulating layer, and a mirror index of a crystal plane of an upper surface of the SOI layer is equal to a mirror index of a crystal plane of an upper surface of the base substance. The buffer film includes ZrO.sub.2 epitaxially grown on the substrate.

A method of forming a plurality of diamonds provides a base, epitaxially forms a first sacrificial layer on the base, and then epitaxially forms a first diamond layer on the first sacrificial layer. The first sacrificial layer has a first material composition, and the first diamond layer is a material that is different from the first material composition. The method then epitaxially forms a second sacrificial layer on the first diamond layer, and epitaxially forms a second diamond layer on the second sacrificial layer. The second sacrificial layer has the first material composition. The base, first and second sacrificial layers, and first and second diamond layers form a heteroepitaxial super-lattice.

A method of forming a plurality of diamonds provides a base, epitaxially forms a first sacrificial layer on the base, and then epitaxially forms a first diamond layer on the first sacrificial layer. The first sacrificial layer has a first material composition, and the first diamond layer is a material that is different from the first material composition. The method then epitaxially forms a second sacrificial layer on the first diamond layer, and epitaxially forms a second diamond layer on the second sacrificial layer. The second sacrificial layer has the first material composition. The base, first and second sacrificial layers, and first and second diamond layers form a heteroepitaxial super-lattice.

According to various implementations of the invention, high quality a-axis XBCO may be grown with low surface roughness. According to various implementations of the invention, low surface roughness may be obtained by: 1) adequate substrate preparation; 2) calibration of flux rates for constituent atoms; and/or 3) appropriate control of temperature during crystal growth. According to various implementations of the invention, a wafer comprises a smoothing layer of c-axis XBCO; a first conducting layer of a-axis XBCO formed on the smoothing layer; an insulating layer formed on the first conducting layer; and a second conducting layer of a-axis XBCO formed on the insulating layer, where, for a same surface roughness, a thickness of the smoothing layer and the first conducting layer combined is greater than a thickness of the first conducting layer without the smoothing layer.

There is provided a semiconductor nanocrystal or quantum dot comprising a core made of a material and at least one shell made of another material. Also there is provided a composite comprising a plurality of such nanocrystals or quantum dots. Moreover, there is provided a method of measuring the temperature of an object or area, comprising using a temperature sensor comprising a semiconductor nanocrystal or quantum dot of the invention.