Controlled assembly of layer-by-layer stacking continuous graphene oxide films and their application for actively modulated field electron emission cathodes

A featured "vapor transportation" assembly technique was developed to attain layer-by-layer stacking continuous graphene oxide (GO) films on both flat and concavo-concave surfaces. Few-layer (layer number < 10) GO sheets were "evaporated" (carried by water vapor) from the water-dispersed GO suspension and smoothly/uniformly tiled on the substrate surface. We have found evidence of the influence of the deposition time and substrate-liquid separation on the film thickness. A model was proposed for interpreting the assembly process. It was found that a current conditioning would induce a reduction of the GO surface and form an Ohmic contact between the GO-metal interfaces. Accordingly, an actively modulated GO cold cathode was fabricated by locally depositing continuous GO sheets on the drain electrode of a metal-oxide-semiconductor field effect transistor (MOSFET). The field emission current of the GO cathode can be precisely controlled by the MOSFET gate voltage (VGS). A current modulation range from 1 × 10(-10) A to 6.9 × 10(-6) A (4 orders of magnitude) was achieved by tuning the VGS from 0.812 V to 1.728 V. Due to the self-acting positive feedback of the MOSFET, the emission current fluctuation was dramatically reduced from 57.4% (non-control) to 3.4% (controlled). Furthermore, the integrated GO cathode was employed for a lab-prototype display pixel application demonstrating the active modulation of the phosphor luminance, i.e. from 0.01 cd m(-2) to 34.18 cd m(-2).