An improved planar-gate triode with CNTs field emitters by electrophoretic deposition

An improved planar-gate triode with carbon nanotubes (CNTs) field emitters has been successfully fabricated by conventional photolithography, screen printing and electrophoretic deposition (EPD). In this structure, cathode electrodes and ITO arrays linked with gate electrodes were interdigitated and paralleled on the same plane although the gate electrodes and cathode electrodes were isolated by dielectric layer, a so-called improved planar-gate triode structure. An electrophoretic process was developed to selectively deposit CNTs field emitters onto cathode electrodes in the CNTs suspension by an applied voltage between the gate electrodes and cathode electrodes. The optical microscopy and FESEM image showed that the CNTs emitters with the uniform packing density were selectively defined onto the cathode electrodes. In addition, field emission characteristics of an improved planar-gate triode with CNTs field emitters were investigated. The experiment results indicated that the turn-on voltage of this triode structure at current density of 1 μA/cm2 was approximately 55 V. The anode current and gate current came to 396 μA and 325 μA, at gate voltage and anode voltage of 100 V and 4000 V, respectively and at the anode-cathode spacing of 2000 μm. The emission image became brighter and the luminous image with dot matrix on the anode plate obviously increased with the increase of the gate voltage. Moreover, the emission current fluctuation was smaller than 5% for 11 h, which indicated that the improved planar-gate triode has a good field emission performance and long lifetime.

Research highlights▶ We have developed an electrophoretic process to selectively deposit CNTs emitters onto the surface of cathode electrodes and an improved planar-gate triode with CNTs field emitters has been successfully fabricated by conventional photolithography, screen printing and electrophoretic deposition and investigated its field emission characteristics. ▶ The experiment result showed that the CNTs emitters were selectively deposited cathode electrodes and each cathode electrodes had the uniform packing density. ▶ The field emission characteristics indicated that turn-on voltage of an improved planar-gate triode at current density of 1 μA/cm2 was around 55 V. ▶ When gate voltage was higher than turn-on voltage, the anode and gate current continually increased under the role of gate voltage. ▶ However, the increase ratio of gate current seemed to be higher than that of anode current as gate voltage was higher than 90 V. ▶ Although the emission efficiency was modified from 94.8% to 54.9%, the emission image became brighter and the luminous image with dot matrix on the anode plate obviously increased with the increases of gate voltage from 0 V to 100 V with anode bias of 4000 V and the anode-cathode spacing was about 2000 μm. ▶ Moreover, the emission current fluctuation was smaller than 5% for 11 h, which indicated that the fabricated device had a good field emission performance and long lifetime. ▶ In a word, this improved planar-gate triode with CNTs field emitters easily realizes the scan between gate and cathode electrodes in the drive circuit and presents the field emission image with dot matrix, which may lead to practical applications for dynamic back light unit and field emission displays.