In recent years there has also been massive growth in interest in the development of other forms of thin-film emitter, both those based on other carbon forms (such as "carbon nanowalls ") and on various forms of wide-band-gap semiconductor. A particular aim is to develop "high- γ " nanostructures with a sufficiently high density of individual emission sites. Thin films of nanotubes in form of nanotube webs are also used for development of field emission electrodes. It is shown that by fine-tuning the fabrication parameters, these webs can achieve an optimum density of individual emission sites. Double-layered electrodes made by deposition of two layers of these webs with perpendicular alignment towards each other are shown to be able to lower the turn-on electric field (electric field required for achieving an emission current of 10 μA/cm) down to 0.3 V/μm and provide a stable field emission performance.