An emitter with a diameter of 100 nm or less is used with a protective cap layer and a diffusion barrier between the emitter and the protective cap layer. The protective cap layer is disposed on the exterior surface of the emitter. The protective cap layer includes molybdenum or iridium. The emitter can generate an electron beam. The emitter can be pulsed.

An electron source capable of suppressing consumption of an electron emission material is provide. The present invention provides an electron source including: an electron emission material; and, an electron emission-suppressing material covering a side surface of the electron emission material, wherein a work function of the electron emission-suppressing material is higher than that of the electron emission material, and a thermal emissivity of the electron emission-suppressing material is lower than that of the electron emission material.

An electron source capable of suppressing consumption of an electron emission material is provide. The present invention provides an electron source including: an electron emission material; and, an electron emission-suppressing material covering a side surface of the electron emission material, wherein a work function of the electron emission-suppressing material is higher than that of the electron emission material, and a thermal emissivity of the electron emission-suppressing material is lower than that of the electron emission material.

A field-emission type electron source includes (i) a single-crystal tungsten rod having a sharpened terminus and (ii) a mass of ZrO formed only on a portion of the surface, or the entire surface, of the sharpened terminus. In preferred design, the single-crystal tungsten rod is placed in a gaseous medium that consists of oxygen and a non-oxygen gas. The molar ratio between oxygen and the non-oxygen gas is greater than 1:1.

An emitter with a diameter of 100 nm or less is used with a protective cap layer and a diffusion barrier between the emitter and the protective cap layer. The protective cap layer is disposed on the exterior surface of the emitter. The protective cap layer includes molybdenum or iridium. The emitter can generate an electron beam. The emitter can be pulsed.

The present invention provides an emitter made of a hafnium carbide (HfC) single crystal that stably emits electrons with high efficiency, a method for manufacturing the emitter, and an electron gun and an electronic device using the emitter. An emitter according to an embodiment of the present invention is an emitter including a nanowire, in which the nanowire is made of the hafnium carbide (HfC) single crystal, at least an end of the nanowire through which electrons are to be emitted is coated with hafnium oxycarbide (HfC.sub.1-xO.sub.x: 0<x?0.5), and a field electron emission pattern of the end obtained by a field emission microscope (FEM) is a single spot.

An electron source capable of suppressing consumption of an electron emission material is provide. The present invention provides an electron source including: an electron emission material; and, an electron emission-suppressing material covering a side surface of the electron emission material, wherein a work function of the electron emission-suppressing material is higher than that of the electron emission material, and a thermal emissivity of the electron emission-suppressing material is lower than that of the electron emission material.

Electron emitters and methods of fabricating the electron emitters are disclosed. According to certain embodiments, an electron emitter includes a tip with a planar region having a diameter in a range of approximately (0.05-10) micrometers. The electron emitter tip is configured to release field emission electrons. The electron emitter further includes a work-function-lowering material coated on the tip.

An emitter with a protective cap layer on an exterior surface of the emitter is disclosed. The emitter can have a diameter of 100 nm or less. The protective cap layer includes ruthenium. Ruthenium is resistant to oxidation and carbon growth. The protective cap layer also can have relatively low sputter yields to withstand erosion by ions. The emitter may be part of a system with an electron beam source. An electric field can be applied to the emitter and an electron beam can be generated from the emitter. The protective cap layer may be applied to the emitter by sputter deposition, atomic layer deposition (ALD), or ion sputtering.

The emitter of the present invention includes a nanowire. The nanowire is formed from a hafnium carbide (HfC) single crystal, and at least an end portion of the hafnium carbide single crystal, from which electrons are to be emitted, is covered with hafnium oxide (HfO.sub.2). In the emitter, the thickness of the hafnium oxide may be 1 nm to 20 nm.