Atomic point-contact imaging

In tunneling microscopy a potential barrier separates a pointed tip from the sample to be investigated. In this letter we show that atomic resolution can be achieved in special cases where the gap spacing has been reduced to the point where the potential barrier may have completely collapsed. In this example the tip may be said to be touching the sample. The forces between the tip and sample are then strongly repulsive and the possibility exists for studying tribology on an atomic scale.