Methods of forming a nano-structure for electron extraction are disclosed. One method of forming a nano-structure comprises irradiating an area on a first surface of a thermal conductive film to melt the area across the film. The film is insulated on a second surface to provide two-dimensional heat transfer across the film. The liquid density of the film is greater than the solid density thereof. The method further comprises cooling the area inwardly from the periphery thereof to form a nano-structure having an apical nano-tip for electron extraction.