Among other things, piezoelectric materials and methods of their manufacture are described; particularly methods of forming regions of varying crystal structure within a relaxor piezoelectric substrate. Such methods may including heating the piezoelectric substrate above the transition temperature and below the Curie temperature such that a first phase transition occurs to a first crystal structure; rapidly cooling the piezoelectric substrate below the transition temperature at a cooling rate that is sufficiently high for the first crystal structure to persist; and applying an electric field through one or more selected regions of the piezoelectric substrate, such that within the one or more selected regions, a second phase transition occurs and results in a second crystal structure.

Among other things, piezoelectric materials and methods of their manufacture are described; particularly methods of forming regions of varying crystal structure within a relaxor piezoelectric substrate. Such methods may including heating the piezoelectric substrate above the transition temperature and below the Curie temperature such that a first phase transition occurs to a first crystal structure; rapidly cooling the piezoelectric substrate below the transition temperature at a cooling rate that is sufficiently high for the first crystal structure to persist; and applying an electric field through one or more selected regions of the piezoelectric substrate, such that within the one or more selected regions, a second phase transition occurs and results in a second crystal structure.

A piezoelectric monocrystalline substrate is composed of a material represented by LiAO.sub.3 (A represents at least one element selected from the group consisting of niobium and tantalum), a bonding layer is compose of a material of an oxide of at least one element selected from the group consisting of niobium and tantalum, and an interface layer is provided along an interface between the piezoelectric monocrystalline substrate 6 and bonding layer, and the interface layer has a composition of E.sub.xO.sub.(1-x) (E represents at least one element selected from the group consisting of niobium and tantalum and 0.29≤x≤0.89).

The present invention relates to a method for producing a group III compound substrate, including: a base substrate forming step for forming a group III nitride base substrate by a vapor phase synthesis method; a seed substrate forming step for forming a seed substrate on the base substrate; and a group III compound crystal forming step for forming a group III compound crystal on the seed substrate by a hydride vapor phase epitaxy method. The group III compound substrate of the present invention is produced by the method for producing a group III compound substrate of the present invention. According to the present invention, a large-sized and high-quality group III compound substrate can be obtained at a low cost while taking advantage of the high film formation rate characteristic of the hydride vapor phase epitaxy method.

A composite substrate includes a sapphire substrate and a layer of a nitride of a group 13 element provided on the sapphire substrate. The layer of the nitride of the group 13 element is composed of gallium nitride, aluminum nitride or gallium aluminum nitride. The composite substrate satisfies the following formulas (1), (2) and (3). A laser light is irradiated to the composite substrate from the side of the sapphire substrate to decompose crystal lattice structure at an interface between the sapphire substrate and the layer of the nitride of the group 13 element. 5.0≦(an average thickness (μm) of the layer of the nitride of the group 13 element/a diameter (mm) of the sapphire substrate)≦10.0 . . . (1); 0.1≦ a warpage (mm) of said composite substrate×(50/a diameter (mm) of said composite substrate).sup.20.6 . . . (2); 1.10≦a maximum value (μm) of a thickness of said layer of said nitride of said group 13 element/a minimum value (μm) of said thickness of said layer of said nitride of said group 13 element . . . (3)

A single crystal diamond material comprising: neutral nitrogen-vacancy defects (NV.sup.0); negatively charged nitrogen-vacancy defects (NV.sup.−); and single substitutional nitrogen defects (N.sub.s) which transfer their charge to the neutral nitrogen-vacancy defects (NV.sup.0) to convert them into the negatively charged nitrogen-vacancy defects (NV), characterized in that the single crystal diamond material has a magnetometry figure of merit (FOM) of at least 2, wherein the magnetometry figure of merit is defined by (I) where R is a ratio of concentrations of negatively charged nitrogen-vacancy defects to neutral nitrogen-vacancy defects ([NV.sup.−]/[NV.sup.0]), [NV.sup.−] is the concentration of negatively charged nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, [NV0] is a concentration of neutral nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, and T.sub.2′ is a decoherence time of the NV.sup.− defects, where T.sub.2′ is T.sub.2* for DC magnetometry or T.sub.2 for AC magnetometry.

A single crystal diamond material comprising: neutral nitrogen-vacancy defects (NV.sup.0); negatively charged nitrogen-vacancy defects (NV.sup.−); and single substitutional nitrogen defects (N.sub.s) which transfer their charge to the neutral nitrogen-vacancy defects (NV.sup.0) to convert them into the negatively charged nitrogen-vacancy defects (NV), characterized in that the single crystal diamond material has a magnetometry figure of merit (FOM) of at least 2, wherein the magnetometry figure of merit is defined by (I) where R is a ratio of concentrations of negatively charged nitrogen-vacancy defects to neutral nitrogen-vacancy defects ([NV.sup.−]/[NV.sup.0]), [NV.sup.−] is the concentration of negatively charged nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, [NV0] is a concentration of neutral nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, and T.sub.2′ is a decoherence time of the NV.sup.− defects, where T.sub.2′ is T.sub.2* for DC magnetometry or T.sub.2 for AC magnetometry.

The present invention provides a fluorescent diamond containing an MV center emitting fluorescence at a concentration of 1×10.sup.14/cm.sup.3 or higher, where M represents a metal or metalloid, and V represents a vacancy.

The present invention provides a fluorescent diamond containing an MV center emitting fluorescence at a concentration of 1×10.sup.14/cm.sup.3 or higher, where M represents a metal or metalloid, and V represents a vacancy.

Embodiments described herein relate generally to the large scale production of functionalized graphene. In some embodiments, a method for producing functionalized graphene includes combining a crystalline graphite with a first electrolyte solution that includes at least one of a metal hydroxide salt, an oxidizer, and a surfactant. The crystalline graphite is then milled in the presence of the first electrolyte solution for a first time period to produce a thinned intermediate material. The thinned intermediate material is combined with a second electrolyte solution that includes a strong oxidizer and at least one of a metal hydroxide salt, a weak oxidizer, and a surfactant. The thinned intermediate material is then milled in the presence of the second electrolyte solution for a second time period to produce functionalized graphene.