Low-cost amorphous diamond films for efficient field emission displays

In this paper, we describe the novel use of amorphous diamond (diamond-like carbon) films for electron field emission. These films have the potential of exhibiting superior electrical, mechanical, manufacturing, and integration characteristics over other candidate materials such as carbon nanotubes (CNTs) for use as field emission display (FED) substrates. Amorphous diamond films exhibit very efficient electron emission characteristics based on the nano-scale combination of crystalline diamond (sp ³) and graphitic (sp ²) bonding to form a highly-entropic, nano-composite. Thus, amorphous diamond represents a unique class of material, combining the properties of an electrically conducting material (graphite) and insulator (diamond) to form a material that exhibits various intermediate atomic energy states between the forbidden band gap. These intermediate energy states allow electrons to climb the energy ladder and emit into free space with the application of a small bias voltage. Furthermore, the natural formation of nano-scale, high-aspect ratio asperities also significantly enhances field emission characteristics. It is possible to deposit high-densities (4 × 10 ¹⁰ emitters/cm ²) of these nano-sized emitters using well-characterized physical vapor deposition (PVD) techniques such as cathodic arc. This type of manufacturing process is very low cost and allows the substrate to be deposited over large areas. In addition, the manufacturing process is highly amenable for the integration of these field-emitting films with underlying electronics/semi-conductor substrates. Various studies have shown that these films are very mechanically robust and exhibit high emission reproducibility across wide operating conditions. Given all these advantages, amorphous diamond films may represent an answer to many of the problems associated with CNT-based FED technologies that are current being investigated.