Emission properties of carbon nanowalls on porous silicon

For the past two decades various methods of carbon nanostructures growth have been proposed. Special substrate pretreatment methods are generally used to grow carbon nanowalls on silicon substrates and among them are mechanical and catalytic methods and ion bombardment in an rf discharge with bias. This work describes the possibility of growing carbon structures on porous silicon in a dc discharge without any additional pretreatment of the substrate surface. Carbon structures were grown on n- and p-type (100) porous silicon substrates produced by using standard photoelectrochemical etching. The analysis of these carbon structures revealed nanocrystalline carbon with multilayer carbon nanotubes and fibers. All samples demonstrated low field emission thresholds (E-tr < 3 V/mu m) and high current densities, showing an achieved current density of more than 6 A/cm(2) for an electric field of E similar to 15 V/mu m. The authors investigated various modifications of porous silicon samples and carbon structures and demonstrated a practicable technique to create a reproducible uniform spot that varies in size from several millimeters to tens of millimeters. The authors propose a simplified and less expensive alternative to existing methods. (C) 2012 American Vacuum Society. [DOI: 10.1116/1.3681287]