Field emission cathode and cleaning method therefor

A method of cleaning a field emission cathode including a first electron-emitting structure having a first insulator layer, a first cathode electrode, a first gate electrode that is separated from said first cathode layer by said first insulator layer, and at least one first emitter tip in a hole formed through said first gate electrode and said first insulator layer to expose a portion of said first cathode electrode, a second electron-emitting structure surrounding said first electron-emitting structure and insulated therefrom, wherein said second electron-emitting structure includes a second cathode electrode and a second gate electrode, which are separated by a second insulator layer, and at least one second emitter tip in a hole formed through said second date electrode and said second insulator layer to expose a portion of said second cathode electrode, and an anode electrode extending over said first and second electron-emitting structures, said method comprising the steps of:

• biasing said second electron-emitting structure with negative potential to induce emission of electrons;
• biasing said anode electrode with a voltage that is higher than a gate voltage applied to said second electron-emitting structure thereby urging the electrons toward said anode electrode for bombarding said anode electrode;
• biasing said anode electrode with a voltage that is lower than said gate voltage applied to said second electron-emitting structure;
• and
• biasing, with said anode electrode biased with said voltage lower than said gate voltage, said first gate electrode and said at least one first emitter tip with a voltage that is higher than said gate voltage thereby urging the electrons toward said first gate electrode and said at least one first emitter tip for bombarding same.