Pretreatment effects by aqua-regia solution on field emission of diamond film

Field emission of diamond film was enhanced after surface treatment using boiling aqua-regia solution. The current generated by the emission of electrons was distinctly increased and the threshold field was reduced from 18.1 to 13.8 V/mu m by the treatment. The amount of C-C bonds was decreased, but the O-C one was increased by the treatment. The Fermi level at the treated surface was increased by 2.2 eV. This provides evidence that the enhancement of electron emission originated from the reduction of the work function, caused by the chemisorption of oxygen atoms at the surface of diamond during the aqua regia treatment. Thus, the effective electron affinity changed from positive to negative, leading to the reduction of the potential barrier height and width for electron emission at the surface of diamond. (C) 2000 American Institute of Physics. [S0003-6951(00)02725-X].