Activation of Field Emitters with Fullerene Coatings by Potassium.

Abstract

Summary form only given. Methods of fullerene-coated tip field emitter creation were worked out and investigated by this report authors. Basic rules and mechanisms of the microstructure origin on the fullerene surface during coverage formation and treatment (thermal and field) were determined. The emitters with fullerene coatings were made that secure stable currents from the single submicron tip up to 150 muA at static regime and up to 1.5-2 mA at pulsed one. But, the operating voltages, that were necessary for such emitters exploitation, were too large because of high (more than 5 eV) value of fullerene coating work function. Activation of the fullerene-coated field emitters by potassium atom and ion flows was studied in this work. The experiments were performed in special high vacuum multifunctional chamber with field emitter microscope. The potassium atoms were sprayed onto fullerene coating from Knoudsen cell. The potassium ions flow for coatings treatment was formed by the new type of source that focused this flow onto the tip field emitter surface. Deposition of thin potassium atoms layer onto the fullerene coating allowed us to decrease the operating voltage value up to 3.5-4 times. But the rapid operating voltage increase immediately after the end of activation by potassium atoms was revealed. Residual operating voltage decrease didn't exceed 20%. This phenomenon was explained by the fast redistribution of potassium atoms in fullerene coating even at room temperature. Much better results were achieved when we treated the fullerene coverage by the ion flow. Lasting operating voltage decrease up to two times was possible to reach in this case. Obtained results attest that efficiency of the fullerene coating activation by the potassium ion flow may be caused by formation of endohedral (K@C60) and/or exohedral (C 60@K) molecules in the coverage. These complex molecules are stable enough. They are not so mobile on the field emitter surface as potassium atoms and these molecules evidently essentially decrease the work function of fullerene coating