Emitter, electron gun in which same is used, electronic device in which same is used, and method for manufacturing same

An emitter comprising a nanoneedle made of a single crystal material,

• wherein the nanoneedle has an inevitable oxide layer at a surface layer portion,
• wherein a portion of the nanoneedle underlying the inevitable oxide layer at the surface layer portion has no change in a stoichiometric composition from the single crystal material, and
• a field electron emission pattern, obtained by a field emission microscope (FEM), at an end of the nanoneedle, through which electrons are to be emitted, is a single spot.

A method for manufacturing an emitter, the method comprising:

• processing a single crystal material in a vacuum using a focused ion beam to form an end of the single crystal material, through which electrons are to be emitted, into a tapered shape, the processing being performed in an environment in which a periphery of the single crystal material fixed to a support is opened,
• wherein the single crystal material is a single crystal nanowire, and
• wherein the processing the single crystal material comprises setting a radius of curvature rw of a tip of the end to a value of 50% or less of a length dw of the single crystal nanowire in a lateral direction.