Atomistic Structural Dynamics and Current Density Variations during the Transformation from Crystalline to Amorphous States in Tantalum Nanocontacts

摘要

Pulsed voltages were applied to crystalline tantalum (Ta) nanocontacts (NCs) having a width of approximately 1 nm in a transmission electron microscope and the structural dynamics during their transformation to amorphous states was observed in situ at atomic resolution with simultaneous conductance measurements. Amorphization was caused when a Ta NC was the grain boundary, i.e., the orientations of the two regions adjacent to the contact boundary were different. The amorphous states transformed into crystalline states when the two regions were oriented along the same direction upon the application of the same pulsed voltage. Thus, it was found that the structural transformation of Ta NCs by pulsed voltages depends on the orientational relationship at the contact boundaries. The current density at the minimum cross-sectional area of the amorphized states decreased to 0.71–0.91 relative to that of the crystalline states.