Preparation of BaF2 thin films for the application to MIS tunnel emitter

Ultrathin BaF2 films of less than 20nm thickness on the Si(100) substrates were deposited by ion beam sputtering technique. The crystallographic quality and surface morphology of the films were investigated by X-ray diffractometer and scanning electron microscope, respectively. The MIS diode type tunnel emitter was fabricated on the n-type Si substrate using this film as a tunnel barrier insulator. The electrical properties of the tunnel emitter such as I-V characteristics and electron emission current into the vacuum were measured. Pico-ampere/mm2 order electron emission current density was obtained for typical samples. These results were systematically investigated in relation to the BaF2 deposition conditions.