The synthesis of carbon nanotubes on silicon nanowires by thermal chemical vapor deposition

In this work, carbon nanotubes (CNTs) were grown on the silicon nanowires substrate with different thickness of Ni catalyst layer at temperatures 900°C using thermal chemical vapor deposition (CVD) to study their effects on surface morphology and field emission characteristics. Scanning electron microscopy (SEM) image was used to observe the surface morphology and structural properties, and Raman spectroscopy was employed to investigate the structural changes caused by different catalyst thickness. Our experimental results clearly demonstrate that catalyst thickness can effectively vary the field emission current of CNTs. Obvious changes in the surface density and morphology of CNTs caused by the variation of catalyst thickness can be clearly seen, which attributed to the grain size effect and thus an increase in emission current. The emission characteristics of CNTs were found to be dependent on the diameter of carbon nanotubes. Compared with CNTs grown on the different thickness of catalyst, CNTs grown on silicon nano wires with Ni catalyst of 7.5nm exhibit the largest field emission current.

Background

In recent years, carbon nanotubes has attracted widespread attention to the researchers due to their unique physical and chemical properties. [1] Besides CNTs have been identified as the promising materials for flat-panel display and cold cathode application. [2] The excellent field emission characteristics of CNTs can be attributed to their high aspect ration and their outstanding chemical stability. [3] Chemical vapor deposition (CVD) has been intensively studied to synthesize CNTs on plain substrates to simplify the fabrication processes of CNT-based devices. [4] In the CVD growth, the catalyst control is one of the most important factors that determine the CNT properties such as length, diameters, and number density. Howerver systematic studies on the surface morphology and field emission characteristics of CNTs on silicon nanowires with different thickness of Ni catalyst layers by thermal CVD are still very rare. It seems to be crucial to the field emission characteristics of CNTs as their diameters. [5] In this study we grew CNTs on silicon nanowires with different thickness of Ni catalyst films and studied on the role of their effects on suface morphology and field emission characteristics.