A unique method for recording, reading and erasing data bits in a data storage device is described. Using extended scanning tunneling microscopy (STM) techniques, a tunneling electron current by resistive heating selectively melts discrete areas of a state-transformable film; then heat is dissipated rapidly, writing data bits by changing the film in said areas from a first state to a second state wherein an electronic property, such as conductance, work function or band gap, in said areas is changed.Again, using extended STM techniques, the effect of this changed electronic property of said film on the tunneling current is measured for reading the written data bits. Minimizing the effect of blemishes on the material is effected, during operation in STM constant current mode by measuring dI/dV or dI/ds, and during operation in STM variable current (constant gap) mode by measuring (dI/dV)/I or (dI/ds)/I.Also by using extended STM techniques, data bits can be selectively erased by resistance heating the film to a temperature higher than the crystallization temperature for a sufficient period of time, restoring selected discrete areas to said first state and each affected electronic property substantially to its original condition.