An in-situ process for the growth of carbon nanotubes on the graphene flakes for enhancing the electron field emission properties

Carbon nanostructures represent cutting-edge nanomaterials poised to replace thermionic emitters in electron emission devices, offering a pathway to miniaturization. Carbon nanotubes (CNTs) and graphene (Gr) stand out for their exceptional electronic and structural properties, making them superior candidates for such applications. This study introduces an in-situ synthesis method for synthesizing a nanostructured composite of Gr-CNT by precisely controlling ammonia (NH₃) gas flow. The nanocomposite samples, prepared at varying NH₃ gas flow rates, were characterized using FESEM and Raman spectroscopy, revealing the formation of flower-like Gr nanoflakes and spiral-threaded CNT profiles. The presence of D and G bands, along with the D′, 2D and D + G bands in the Raman spectra, confirms the successful growth of the Gr-CNT field emitters. The electron field emission properties were significantly improved, leading to reduced turn-on E_to2.48→1.95V/μm and threshold E_th2.9→2.32V/μm fields, respectively. Notably, increasing NH₃ gas flow rates enhanced the macroscopic emission current density J_M174→797μA/cm² become maximum at 40 sccm (standard cubic centimeters per minute) due to increased CNT protrusions. Repeatability tests and analyses of emission current stability demonstrated superior performance compared to pristine Gr field emitters. Increased protrusions density, reduced contact resistance, and a lesser screening effect are responsible for this enhanced stability. Additionally, the prepared field emitters were considered suitable for practical applications based on the scaled barrier field values extracted from the emission experiments, which satisfied the necessary criteria.