Tunneling in a double-barrier system and its practical implications for field ionization and field emission

The relationship between the chemical bond formation and tunneling phenomena in general, and the relationship between the field ionization of inert gases and the chemical reactivity of metallic surfaces in particular, are discussed in terms of a double-barrier model of the field ionization. Within the framework of this model, resonance enhanced tunneling is used to elucidate (i) the visibility of only those atoms which are located at the edges of densely populated atomic layers (in contrast to the STM images, where no such effect occurs); (ii) the visibility of outer metallic clusters deposited onto an oxide layer in MOM systems. It is also demonstrated that some results of FIM and STM studies cannot be understood on the basis of one-dimensional models, in spite of the wide and successful use of essentially one-dimensional approaches in the theoretical treatment of tunneling phenomena.