A ribbon is formed such that the ribbon floats on a melt using a cold initializer facing an exposed surface of the melt. The ribbon is single crystal silicon. The ribbon is pulled from the silicon melt at a low angle off the melt surface. The ribbon is formed at a same rate as the pulling. The ribbon is separated from the melt at a wall of the crucible where a stable meniscus forms. The ribbon has a thickness between a first surface and an opposite second surface from 50 μm to 5 mm. The ribbon includes a first region extending a first depth from the first surface. The first region has a reduced oxygen concentration relative to a bulk of the ribbon.

By widening a terrace on a crystal surface on a bottom face of a recess by step flow caused by heating, a flat face is formed on the bottom face of the recess, a two-dimensional material layer made of a two-dimensional material is formed on the formed flat face, and then a device made of the two-dimensional material layer is produced.

A method for producing a crystal substrate includes preparing, measuring, holding, and machining. The preparing prepares a crystal substrate body including a curved crystal lattice plane. The measuring measures a shape feature of the crystal lattice plane. The holding holds the crystal substrate body in a warped state in accordance with the shape feature measured by the measuring, to more flatten the crystal lattice plane than the crystal lattice plane at the preparing. The machining machines a surface of the crystal substrate body held in the warped state, to flatten the surface.

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Ga.sub.x1Al.sub.y1In.sub.1-x1-y1N (0≦x1≦1, 0≦x1+y1≦1) and the seed crystal is expressed as Ga.sub.x2Al.sub.y2In.sub.1-x2-y2N (0≦x2≦1, 0≦x2+y2≦1). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Ga.sub.x1Al.sub.y1In.sub.1-x1-y1N (0≦x1≦1, 0≦x1+y1≦1) and the seed crystal is expressed as Ga.sub.x2Al.sub.y2In.sub.1-x2-y2N (0≦x2≦1, 0≦x2+y2≦1). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.

A sheet-forming apparatus including a crucible for holding a melt of material and a solid sheet of the material disposed within the melt, a crystallizer disposed above the crucible and configured to form the sheet from the melt, and an ultrasonic measurement system disposed adjacent the crystallizer, the ultrasonic measurement system comprising at least one ultrasonic measurement device including a waveguide coupled to an ultrasonic transducer for directing an ultrasonic pulse through the melt.

A sheet-forming apparatus including a crucible for holding a melt of material and a solid sheet of the material disposed within the melt, a crystallizer disposed above the crucible and configured to form the sheet from the melt, and an ultrasonic measurement system disposed adjacent the crystallizer, the ultrasonic measurement system comprising at least one ultrasonic measurement device including a waveguide coupled to an ultrasonic transducer for directing an ultrasonic pulse through the melt.

The present embodiments relate to a method for manufacturing a two-dimensional material using a top-down method, the method includes the steps of preparing a bulk crystal, forming a metal layer on the bulk crystal, and then attaching a thermal release tape on the metal layer, exfoliating a two-dimensional material to which the metal layer and the thermal release tape have been attached from the bulk crystal, transferring the two-dimensional material to which the metal layer and the thermal release tape have been attached onto a substrate, and removing the thermal release tape and the metal layer from the substrate onto which the two-dimensional material has been transferred.

The present embodiments relate to a method for manufacturing a two-dimensional material using a top-down method, the method includes the steps of preparing a bulk crystal, forming a metal layer on the bulk crystal, and then attaching a thermal release tape on the metal layer, exfoliating a two-dimensional material to which the metal layer and the thermal release tape have been attached from the bulk crystal, transferring the two-dimensional material to which the metal layer and the thermal release tape have been attached onto a substrate, and removing the thermal release tape and the metal layer from the substrate onto which the two-dimensional material has been transferred.

A sapphire ribbon of the present disclosure has a width, a thickness, and a length that are orthogonal to one another, a length direction is a growth direction, and the sapphire ribbon further has two main surfaces separate from each other in a thickness direction, and the width is at least 40 cm. Further, a monocrystalline ribbon manufacturing apparatus using EFG method according to the present disclosure includes a crucible having a width greater than a depth thereof, a die pair installed in the crucible and facing each other across a slit in the depth direction, a first heater and a second heater disposed around the crucible and facing each other in the depth direction, and a third heater and a fourth heater disposed around the crucible and facing each other in the width direction.