A metal hexaboride nanowire such as LaB6 with the formed metal-terminated (100) plane at the tip has a small work function, and can emit a very narrow electron beam from the (100) plane. In such emitters, contamination occurs in a very short time period, and the output current greatly decreases when used under low temperature. The cold field emitter of the present invention overcomes this problem with a stabilization process that exposes the metal-terminated (100) plane of the tip to hydrogen at low temperature, and can stably operate over extended time periods.