Synthesis and characterization of Si/Cs/O nanocluster thin films with negative electron affinity

Abstract

Patterned and unpatterned thin films of Si/Cs/O nanoclusters have been synthesized by the technique of supersaturated thermal vaporization of Si and Cs in an oxygen background gas. These films, which were deposited onto conducting or semiconducting substrates, exhibit negative electron affinity (NEA) as evidenced by ultraviolet photoemission spectroscopy. Photo, secondary, and field electron emission properties of these nanocluster films were investigated with photoelectron emission microscopy, field electron emission microscopy, secondary electron microscopy, and current-voltage measurements. Flat cathodes covered with thin films of Si/Cs/O nanoclusters exhibited high current outputs and lower turn-on fields ({lt}8.7 V/{mu}m) than most NEA diamond surfaces and gated Si or Mo tip arrays. The films{close_quote} NEA is unaffected by air exposure and is stable to high-temperature annealing (550h{degree}C). The electron emission property of the NEA nanocluster films can be best explained by a subband gap abundant surface-state nanocluster model. A field-emission display unit with a simple diode structure containing a flat cathode coated with a thin film of Si/Cs/O nanoclusters has also been built to demonstrate the potential application of this material in cold cathode electron emitting devices, particularly field-emission flat panel displays. {copyright} {ital 1999} {ital The American Physical Society}