ABSTRACT
Initiation of the modern era of surface science, generally acknowledged as starting in the late 1960s, was made possible by two distinct qualitative leaps forward. One was the Sputnik-inspired development of ultra-high vacuum and electron-optical technologies. The other was the recognition and development of theoretical and measurement techniques for studying surface properties and processes on the atomic level. When a single atom, molecule, or cluster is adsorbed onto that portion of the surface emitting through the probe hole, if the adsorbate has an electron quasibound state near the Fermi level of the tip, then a substantial increase in the probe-hole current can occur as a result of resonance-tunneling enhancement through the adsorbate. The theory of resonance tunneling developed during this period is applicable in many areas of current interest and activity, for instance resonance tunneling in nanostructures such as quantum wells, quantum dots, and in the scanning tunneling microscopy (STM), as discussed in the 1993 Physical Review paper by Gadzuk.
