ENHANCED FIELD EMISSION FROM NANOSTRUCTURED CARBON FILMS

Igor Pavlovsky, R.L. Fink, L.F. Thuesen, Zvi Yaniv

Field Emission Picture Element Technology, Inc.

Robert Espinosa

Microwave Power Technology

Abstract

Nanostructured carbon thin films with enhanced field emission characteristics have been grown on a variety of substrate materials. The crystalline structure, sp²/sp³ ratio, and morphology of carbon films depended on the method and parameters of the deposition. Good adhesion properties for the films on glass, ceramics, silicon and metals have been achieved. Average distance between the emitters is on the order of their height, significantly improving the field enhancement conditions over the emission area of the films.

Typical threshold electric field is 1.5 to 2 V, emission current densities reach 10 mA/cm² at a field of 3 V/mm, and over 1 A/cm² at a field of 7 V/mm (see Fig. 1). Such low fields can be attributed to high aspect ratios of the emitters, or low electron affinity of emission areas, depending on the type of carbon material. The long-term stability graph for the cathodes tested in DC mode in a sealed device is shown in Fig. 2. An emission current degradation of less than 10% after 2000 hrs operation at constant voltage was observed.

Fig.1. I-V curves for a Si-backed cathode

Fig.2. Lifetime test of a cathode in a sealed device

We demonstrated the selective growth of carbon films by patterning a layer of catalytic material or by a surface passivation technique. Low-cost carbon deposition processes developed at FEPET can be scaled up to larger substrates (currently the substrate size is ca. 6”). The patterned emitters can find applications in gated electron sources, field emission displays, and microwave electronics.

Keywords: field emission, carbon cold cathodes, electron guns.

Igor Pavlovsky

FEPET, Inc.

3006 Longhorn Blvd. #107,

Austin, TX 78758 USA

Fax: (512) 339-5021

Tel: (512) 339–5020x131

E-mail: ipavlovs@carbontech.net