Gunver Nielsen

Electron emission from ultralarge area metal-oxide-semiconductor electron emitters

Ultralarge metal-oxide-semiconductor (MOS) devices with an active oxide area of 1cm2 have been fabricated for use as electron emitters. The MOS structures consist of a Si substrate, a SiO2 tunnel barrier (∼5nm), a Ti wetting layer (3–10A), and a Au top layer (5–60nm). Electron emission from the Au metal layer to vacuum is realized from these devices by applying bias voltages larger than the work function of the Au layer. The emission is characterized for Au layers with thicknesses ranging from 5to60nm nominally. The emission efficiency changes from close to 10−6 to 10−10. The Ti wetting layer is varied from 3to10A which changes the emission efficiency by more than one order of magnitude. The apparent mean free path of ∼5eV electrons in Au is found to be 52A. Deposition of Cs on the Au film increased the electron emission efficiency to 4.3% at 4V by lowering the work function. Electron emission under high pressures (up to 2bars) of Ar was observed.