Improvement of Field-Emission Characteristics of Carbon Nanotubes by Post Electrical Treatment

The field-emission characteristics of carbon nanotubes (CNTs), such as uniformity and brightness, were improved by electrical treatment using nonstationary electric fields between the cathode of screen-printed CNT emitters and the anode of a phosphor-coated indium-tin-oxide glass substrate in diode configuration. Dead or weak emission spots, where almost no emission of electrons was observed, started to emit electrons by applying an alternating-current voltage to the cathode electrode and a constant voltage to the anode electrode. The nonstationary electrical treatment was more effective than the direct-current (dc) and the square-pulsed electrical treatments for the emission uniformity and brightness. It was found that the nonstationary electrical treatment not only activated CNT emitters but also suppressed abnormally high emission spots without the drawbacks of electrical breakdown. Consequently, more than 1.8 and 1.3 times improvements of emission uniformity and brightness, respectively, were obtained after the treatment, when compared with the dc electrical treatment for the same amount of emission currents and the same duration of the treatments. Therefore, the method can be effectively applied to field-emission devices based on CNTs for the enhancement of emission properties.