Quantitative relationship between the work function and transfer ratio of a potassium-adsorbed MIM cathode

The emission currentIe, diode currentIdand work function Φ of a potassium adsorbed Al-Al2O3-Au MIM cathode were measured. When Φ was reduced to 2.5 eV by K adsorption, the transfer ratioα =I/eIdincreased to 0.32%. By evaporating K atoms gradually, the quantitative relationship between α and Φ was derived, and this was converted into the energy distribution of hot electrons in an energy range of 2.5 to 6 eV. By simulating the measured distribution and α, we found that the electron-electron inelastic scattering in the top metal determines the shape of the distribution, while the electron-phonon inelastic scattering in the insulator and the electron-phonon elastic scattering reduce α.