A field ionization device can include a first insulator layer on a first side of a substrate, a conductive gate layer on the first insulator layer, a cavity in the substrate, a portion of first insulator over the cavity, an aperture in the portion of the first insulator layer and the conductive gate layer thereby forming an aperture and aperture sidewall. The device can include a second insulator layer on the aperture sidewall and surface of the cavity, a metallization layer over the second insulator layer, a catalyst layer on the metallization layer, and a carbon nanotube. The cavity can be made by etching a second side of the substrate to near the insulator layer, wherein the second side is opposite the first side. The carbon nanotube can be grown from the catalyst layer. The device can further include a collector located near the carbon nanotube. The conductive gate layer can be biased negative with respect to the carbon nanotube. An electric field can exist between the carbon nanotube and the conductive gate layer. Another embodiment can include an array of multiple devices as described herein wherein the multiple devices are in close proximity to each other. Also provided is a method of making the device.