Poisoning of Spindt-type molybdenum field emitter arrays by CO2

The effect of CO2 on the emission characteristics of Spindt-type molybdenum field emission cathode arrays is investigated. Exposure of active field emitters to CO2 results in emission degradation. The degradation ranges from (11.8 +/- 3.8)% for 10 L to (77.2 +/- 12.6)% for 5000 L CO2 exposures. The emission loss results from the formation of molybdenum oxide on tip surfaces, resulting in an increased work function. Work function changes of 0%-7.5% have been measured. The emission changes resulting from CO2 exposures are similar to the effects observed with O-2 exposures. The emission degradation mechanism is the interaction of oxygen with molybdenum forming surface molybdenum oxides, thus resulting in a higher surface work function and lower emission current. The emission degradation resulting from CO2 exposure is compared to the emission enhancement produced by exposure to CH4. (C) 1998 American Vacuum Society.