A method of producing graphene or other two-dimensional material such as graphene including heating the substrate held within a reaction chamber to a temperature that is within a decomposition range of a precursor, and that allows two-dimensional crystalline material formation from a species released from the decomposed precursor; establishing a steep temperature gradient (preferably >1000 C. per meter) that extends away from the substrate surface towards an inlet for the precursor; and introducing precursor through the relatively cool inlet and across the temperature gradient towards the substrate surface. The steep temperature gradient ensures that the precursor remains substantially cool until it is proximate the substrate surface thus minimizing decomposition or other reaction of the precursor before it is proximate the substrate surface. The separation between the precursor inlet and the substrate is less than 100 mm.

A method of forming a gallium oxide film is provided, and the method may include supplying mist of a material solution comprising gallium atoms and chlorine atoms to a surface of a substrate while heating the substrate so as to form the gallium oxide film on the surface of the substrate, in which a molar concentration of chlorine in the material solution is equal to or more than 3.0 times and equal to or less than 4.5 times a molar concentration of gallium in the material solution.

A template-assisted method for the synthesis of 2D nanosheets comprises growing a 2D material on the surface of a nanoparticle substrate that acts as a template for nanosheet growth. The 2D nanosheets may then be released from the template surface, e.g. via chemical intercalation and exfoliation, purified, and the templates may be reused.

A method of producing graphene or other two-dimensional material such as graphene including heating the substrate held within a reaction chamber to a temperature that is within a decomposition range of a precursor, and that allows two-dimensional crystalline material formation from a species released from the decomposed precursor; establishing a steep temperature gradient (preferably >1000 C. per meter) that extends away from the substrate surface towards an inlet for the precursor; and introducing precursor through the relatively cool inlet and across the temperature gradient towards the substrate surface. The steep temperature gradient ensures that the precursor remains substantially cool until it is proximate the substrate surface thus minimizing decomposition or other reaction of the precursor before it is proximate the substrate surface. The separation between the precursor inlet and the substrate is less than 100 mm.

A method of forming an aluminum nitride film includes: preparing a substrate that comprises, in a surface thereof, a plurality of concave portions that are separated from each other; forming an aluminum nitride film on said surface of the substrate and on an inner surface of each of the concave portions such that open holes are formed in a portion of the aluminum nitride film corresponding to each of the concave portions, each of the holes being smaller than each of openings of the concave portions; and applying heat treatment to the substrate with the aluminum nitride film formed thereon in a nitrogen gas containing a carbon monoxide gas to close the holes formed in the aluminum nitride film.

To suppress a change in electrical characteristics and to improve reliability in a semiconductor device using a transistor including an oxide semiconductor. The semiconductor device includes a gate electrode over an insulating surface, an oxide semiconductor film overlapping with the gate electrode, a gate insulating film which is between the gate electrode and the oxide semiconductor film and is in contact with a surface of the oxide semiconductor film, a protective film in contact with an opposite surface of the surface of the oxide semiconductor film, and a pair of electrodes in contact with the oxide semiconductor film. In the gate insulating film or the protective film, the amount of gas having a mass-to-charge ratio m/z of 17 released by heat treatment is greater than the amount of nitrogen oxide released by heat treatment.

A transistor includes a multilayer film in which an oxide semiconductor film and an oxide film are stacked, a gate electrode, and a gate insulating film. The multilayer film overlaps with the gate electrode with the gate insulating film interposed therebetween. The multilayer film has a shape having a first angle between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film and a second angle between a bottom surface of the oxide film and a side surface of the oxide film. The first angle is acute and smaller than the second angle. Further, a semiconductor device including such a transistor is manufactured.

A template-assisted method for the synthesis of 2D nanosheets comprises growing a 2D material on the surface of a nanoparticle substrate that acts as a template for nanosheet growth. The 2D nanosheets may then be released from the template surface, e.g. via chemical intercalation and exfoliation, purified, and the templates may be reused.

A process for fabricating a heterostructure made of semiconductor materials having a crystalline structure of wurtzite type, includes the following steps: structuring a surface of a zinc oxide monocrystalline substrate into mesas; depositing by epitaxy at least one layer of semiconductor materials having a crystalline structure of wurtzite type, forming the heterostructure, on top of the structured surface. Heterostructure obtained by such a process. A process for fabricating at least one electronic or optoelectronic device from such a heterostructure is also provided.

A transistor includes a multilayer film in which an oxide semiconductor film and an oxide film are stacked, a gate electrode, and a gate insulating film. The multilayer film overlaps with the gate electrode with the gate insulating film interposed therebetween. The multilayer film has a shape having a first angle between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film and a second angle between a bottom surface of the oxide film and a side surface of the oxide film. The first angle is acute and smaller than the second angle. Further, a semiconductor device including such a transistor is manufactured.