An electron emission device having a narrow electron energy range and excellent electron emitting efficiency, and an electron microscope using the electron emission device. An electron emission device having a laminated structure in which a first electrode, an electron accelerating layer made of an insulating film, and a second electrode are laminated in this order, in which the second electrode through which electrons transmit and from whose surface electrons emit, and the energy width of the emitted electrons is 100 meV or more and 600 meV or less. For example, graphene having one or more layers and 20 layers or less can be used as the second electrode, and hexagonal boron nitride can be used as the insulating film.

An electron emission source is provided. The electron emission source includes a first electrode, an insulating layer, and a second electrode. The first electrode, the insulating layer, and the second electrode are successively stacked with each other. the second electrode is a graphene layer, and the graphene layer is an electron emission end to emit electron. A thickness of the graphene layer ranges from about 0.1 nanometers to about 50 nanometers.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

An electron emission source is provided. The electron emission source comprises a first electrode, an insulating layer, and a second electrode, The first electrode, the insulating layer, and the second electrode are successively stacked with each other. the second electrode is a graphene layer, and the graphene layer is an electron emission end to emit electron. A thickness of the graphene layer ranges from about 0.1 nanometers to about 50 nanometers.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.

A composite including: at least one selected from a silicon oxide of the formula SiO.sub.2 and a silicon oxide of the formula SiO.sub.x wherein 0<x<2; and graphene, wherein the silicon oxide is disposed in a graphene matrix.