Provided is a method for producing a crystal fiber which can suppress the occurrence of stress birefringence even while distributing a light emission center so as to concentrate on a cross-sectional middle portion. The method for producing a crystal fiber comprises the steps of: using, as a preform, the crystal fiber comprising a light emission center that volatilizes from a melted portion upon the melting of a crystal, and heating a portion or a plurality of portions of the side of the preform, whereby the portion or the plurality of portions of the preform are melted such that only a given amount of the inside of the portion or the plurality of portions of the preform is not melted, to form the melted portion; and sequentially transferring the melted portion in the longitudinal direction of the preform, and cooling the melted portion, whereby the melted portion is continuously recrystallized to form a recrystallized region.

Provided is a method for producing a crystal fiber which can suppress the occurrence of stress birefringence even while distributing a light emission center so as to concentrate on a cross-sectional middle portion. The method for producing a crystal fiber comprises the steps of: using, as a preform, the crystal fiber comprising a light emission center that volatilizes from a melted portion upon the melting of a crystal, and heating a portion or a plurality of portions of the side of the preform, whereby the portion or the plurality of portions of the preform are melted such that only a given amount of the inside of the portion or the plurality of portions of the preform is not melted, to form the melted portion; and sequentially transferring the melted portion in the longitudinal direction of the preform, and cooling the melted portion, whereby the melted portion is continuously recrystallized to form a recrystallized region.

Provided herein are methods for forming one or more silicon nanostructures, such as silicon nanotubes, and a silica-containing glass substrate. As a result of the process used to prepare the silicon nanostructures, the silica-containing glass substrate comprises one or more nanopillars and the one or more silicon nanostructures extend from the nanopillars of the silica-containing glass substrate. The silicon nanostructures include nanotubes and optionally nanowires. A further aspect is a method for preparing silicon nanostructures on a silica-containing glass substrate. The method includes providing one or more metal nanoparticles on a silica-containing glass substrate and then performing reactive ion etching of the silica-containing glass substrate under conditions that are suitable for the formation of one or more silicon nanostructures.

Provided herein are methods for forming one or more silicon nanostructures, such as silicon nanotubes, and a silica-containing glass substrate. As a result of the process used to prepare the silicon nanostructures, the silica-containing glass substrate comprises one or more nanopillars and the one or more silicon nanostructures extend from the nanopillars of the silica-containing glass substrate. The silicon nanostructures include nanotubes and optionally nanowires. A further aspect is a method for preparing silicon nanostructures on a silica-containing glass substrate. The method includes providing one or more metal nanoparticles on a silica-containing glass substrate and then performing reactive ion etching of the silica-containing glass substrate under conditions that are suitable for the formation of one or more silicon nanostructures.

A diamond powder comprising diamond particles having an average particle size of no more than 20 μm and a vacancy or impurity-vacancy point defect concentration of at least 1 ppm. At least 70% of the volume of diamond in the powder is formed from a single crystal growth sector. This leads to a substantially uniform concentration of vacancies or impurity-vacancy point defects in the diamond particles because the rate of impurity take-up during growth is heavily dependent on the growth sector, which in turn leads to a more uniform fluorescent response. There is also described a method for making such a powder.

A diamond powder comprising diamond particles having an average particle size of no more than 20 μm and a vacancy or impurity-vacancy point defect concentration of at least 1 ppm. At least 70% of the volume of diamond in the powder is formed from a single crystal growth sector. This leads to a substantially uniform concentration of vacancies or impurity-vacancy point defects in the diamond particles because the rate of impurity take-up during growth is heavily dependent on the growth sector, which in turn leads to a more uniform fluorescent response. There is also described a method for making such a powder.

Doped nanoparticles, methods of making such nanoparticles, and uses of such nanoparticles. The nanoparticles exhibit a metal-insulator phase transition at a temperature of −200° C. to 350° C. The nanoparticles have a broad range of sizes and various morphologies. The nanoparticles can be used in coatings and in device structures.

Doped nanoparticles, methods of making such nanoparticles, and uses of such nanoparticles. The nanoparticles exhibit a metal-insulator phase transition at a temperature of −200° C. to 350° C. The nanoparticles have a broad range of sizes and various morphologies. The nanoparticles can be used in coatings and in device structures.

Provided are a semiconductor material based on metal nanowires and a porous nitride, and a preparation method thereof. The semiconductor material includes: a substrate; a buffer layer formed on the substrate; and a composite material layer formed on the buffer layer the composite material layer includes: a transverse porous nitride template layer; and a plurality of metal nanowires filled in pores of the transverse porous nitride template layer.

There is a method for forming a semiconductor nanostructure on a substrate. The method includes placing a substrate and a semiconductor material in a pulsed laser deposition chamber; selecting parameters including a fluence of a laser beam, a pressure P inside the chamber, a temperature T of the substrate, a distance d between the semiconductor material and the substrate, and a gas molecule diameter a.sub.0 of a gas to be placed inside the chamber so that conditions for a Stranski-Krastanov nucleation are created; and applying the laser beam with the selected fluence to the semiconductor material to form a plume of the semiconductor material. The selected parameters determine the formation, from the plume, of (1) a nanolayer that covers the substrate, (2) a polycrystalline wetting layer over the nanolayer, and (3) a single-crystal nanofeature over the polycrystalline wetting layer, and the single-crystal nanofeature is grown free of any catalyst or seeding layer.