Field Emission Properties of Diamondlike Carbon (DLC) Films Made by a Novel Laser Evaporation Technique

Abstract

Field emission properties of non-hydrogenated DLC films prepared by a novel laser evaporation technique has been studied. A key feature of the novel technique is using a scanning pulsed laser beam, irradiating a graphite target with a focused beam and constant laser power density. The technique has a main advantage of easy scale up for uniform and large area coating. The results show that the DLCfilms exhibit an electron emission thresholdfield as low as 10-20 V/pm and a current density of 100 mA/cm2 at 40 V/pm. In addition, a bright image of cathodoluminescence has been successfully obtained ?om afield emission display with the DLCfilm emitter. I. INTRODUCTION It has been reported that carbon-based material field emitters [l-71 have a high potential for the applications of a field emission display (FED). The carbon-based materials exhibit a low effective work function, extraordinary hardness, chemical inertness and high thermal conductivity which are apparently suitable for high performance electron emitters. Among these materials, non-hydrogenated diamondlike carbon (DLC) films are believed to be a primary candidate material for an FED due to its low temperature deposition process together with relatively high thermal stability which is compatible with a current state of the art of a vacuum packaging process using frit sealing [S, 91. In this contribution we present a novel laser evaporation technique for large area deposition of non-hydrogenated DLC films. Preliminary results for the field emission analysis of these films show an electron emission threshold value as low as 10-20 V/pm and thermal stability enough to endure the frit sealing process. 11. EXPERIMENTAL The novel technique uses a scanning pulsed laser beam with nominal power densities as high as 10'0-10'3 watts/cm2. The laser beam, with the beam spot size kept constant, sweeps a graphite target surface to produce a moving laser plasma, which is then solidified onto a moving substrate thereby forming a non-hydrogenated DLC film. The main advantage of this technique is that it can provide a uniform and large area DLC coating which has been very difficult to be met by a conventional pulsed laser deposition method [lo-121. Up to now a 11 inch DLC film was successfully deposited by this technique. The schematic illustration of the novel system was shown in Fig. 1. The DLC films were prepared on MO or Cr metal coated glass substrates to measure field emission characteristics. A finely polished glass plate embedded with stainless steel rods or a glass plate with patterned IT0 film was used as an anode. The anode plate was separated from the cathode by using a 20 pm thick metal film as a spacer. A phosphor coated IT0 glass substrate was used as an anode to observe a cathodoluminescent pattern. I-V characteristics of the samples were measured in UHV environment better than low lo-*