chemical etching process a physical grinding process or a combination thereof the protrusion 11 may be formed in a shape selected from the group consisting of a circular cone a polygonal cone a circular truncated cone a polygonal truncated cone and a polygonal pillar for example the prior art silicon tip manufacturing technology may be used after the protrusion 11 is formed the carbon nanotube 20 is vertically arranged on the apex of the protrusion 11 the carbon nanotube 20 has a diameter of approximately 5 nm in order to vertically arrange the carbon nanotube 20 on the substrate 10 a variety of methods can be used for example the substrate 10 on which the protrusion 11 is formed can be loaded in a reaction furnace and a plasma enhanced chemical vapor deposition pecvd performed to allow the carbon nanotube 20 to be adhered to the protrusion 11 and grown alternatively a catalytic point formed of transition metal can be formed on the apex of the protrusion 11 so that the carbon nanotube 20 is grown from the catalytic metal point alternatively the carbon nanotube 20 can be separately prepared and the bottom of the carbon nanotube 20 adhered to the apex of the protrusion 11 by for example welding next the ruthenium coating layer 30 can be formed on the carbon nanotube 20 and at least a portion of.