Time-tuned ZnO(x)/MWCNTs hybrid cold cathodes for next-generation electron emission

In this study, diverse thicknesses of zinc oxide (ZnO)-decorated multi-walled carbon nanotubes (MWCNTs) were prepared. The surface of MWCNTs was coated with ZnO nanoparticles during deposition times of 0, 2, 4, and 6 min at 100 Watts (W) power by using the RF-Sputtering technique, with the aim of enhancing both field emission and gas-sensing properties. Comprehensive characterization techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, were employed to MWCNT growth and the attachment of ZnO nanoparticles to MWCNTs. Field emission studies of ZnO(x)/MWCNTs (where x = 0, 2, 4, and 6 min) indicated a significant increase in current density. Notably, the ZnO(4)/MWCNTs field emitter exhibited superior performance, featuring a lower turn-on voltage (0.83 V/µm), a higher current density (80.03 mA/cm²), and a larger field enhancement factor (27,101). Moreover, this field emitter demonstrated exceptional stability over a 30-h period, outperforming its counterparts, ZnO (0, 2, and 6)/MWCNTs.In addition to the field emission properties, the gas-sensing capabilities of the as-prepared ZnO(x)/MWCNTs were evaluated, particularly focusing on sensitivity towards NH₃ gas. The ZnO(4)/MWCNTs sample exhibited remarkable resistance variation, resulting in an outstanding sensor response (1.9 s), rapid response time (4 s), swift recovery time (5 s), and excellent repeatability when compared to other samples. Overall, this study not only elucidates the synthesis and characterization of ZnO-decorated MWCNTs but also highlights the superior field emission and gas-sensing performances of the ZnO(4)/MWCNTs composite, establishing it as a promising candidate for various applications.