Honeycomb arrays of carbon nanotubes in alumina templates for field emission based devices and electron sources

Field Emission (FE) properties of vertically aligned Carbon Nanotubes (CNTs) grown in a nanoporous anodic aluminium oxide (AAO) template have been investigated. A 50-μm-thick AAO template was fabricated by electrochemical techniques. The nanotubes were synthesized in a CVD quartz hot wall furnace using C2H2/N2 mixtures as feeding gas. I–V measurements have been performed on samples after the nanotubes growth (type I samples) and after a partial Al2O3 removal (type II samples) in order to obtain segments of nanotubes protruding from the nanopores. The effects of the conditioning process and adsorbates release have been investigated. The emission curves have been analysed in the framework of the Fowler–Nordheim model. For the β factor enhancement, a different dependence on time has been evidenced for two types of investigated samples and has been tentatively correlated with materials modifications occurring under the HV polarisation (in case of type I samples) and with the damage induced by chemical etching (in case of type II samples). The values of emitted current density (up to 40 mA/cm2) and the emission properties indicate that the proposed preparation methodology is suitable for the realization of robust and efficient CNT-based field emission devices and electron sources.