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Resonant field emission from two-dimensional density of state on hydrogen-terminated intrinsic diamond
Field emission properties from hydrogen-terminated intrinsic diamond covered by adsorbate films are characterized as a function of surface adsorbate coverage and bulk doping with n- and p-type. The threshold of field emission from the undoped intrinsic diamond is lower than from p-type doped diamond, which is attributed to electrons arising from a two-dimensional density of state (2D-DOS) at the surface of diamond. The emission current saturates toward higher fields ("plateau"), which indicates a depletion of the 2D states. For even higher fields, the emission current rises again due to electron tunneling from the valence band. After thermal treatment of the adsorbate film to vanish surface conduction, the emission current is completely quenched since the 2D-DOS has been removed and diamond becomes fully insulating. These data are compared with p- and n-type diamonds, which show a continuous rise of emission current as a function of electric filed. Calculations based on theFowler-Nordheim equation reveal a 2D-quantized energy level in the surface conductive layer.