Dielectric breakdown of ultrathin aluminum oxide films induced by scanning tunneling microscopy

Abstract

Dielectric breakdown of 7-Å-thick Al2O3 (111) films grown on Ni3Al(111) under ultrahigh vacuum conditions is induced by increasing the bias voltage on the scanning tunneling microscopy tip under constant current feedback. Breakdown is marked by the precipitous retreat of the tip from the surface, and the formation of an elevated feature in the scanning tunneling microscopy image, typically greater than 5 nm high and ∼100 nm in diameter. Constant height measurements performed at tip/sample distances of 1 nm or less yield no tip/substrate physical interaction, indicating that such features do not result from mass transport. Consistent with this, current/voltage measurements within the affected regions indicate linear behavior, in contrast to a band gap of 1.5 eV observed at unaffected regions of the oxide surface. A threshold electric field value of 11±1 MV cm−1 is required to induce breakdown, in good agreement with extrapolated values from capacitance measurements on thicker oxides.

Atomically Thin Al2O3 Films for Tunnel Junctions

“…[32]. In great contrast, the thermal AlO x tunnel barriers broke-down in a soft-breakdown manner due to defect migration within the barrier [24,25,[32][33][34][35]. We should note that the 75 min heated samples displayed both types of breakdown, which is consistent with the thin IL found in Fig.…”

“…3(b). [32]. In great contrast, the thermal AlO x tunnel barriers broke-down in a soft-breakdown manner due to defect migration within the barrier [24,25,[32][33][34][35].…”

STM-induced reversible switching of local conductivity in thinAl2O3films

“…14,15 Within this approach we can explain the switching behavior without requiring a metalliclike I-V behavior after inducing a leakage site. Such a metallic behavior was observed by Da Costa et al 4 and Magtoto et al 5 and was attributed to dielectric ͑hard͒ breakdown. Our experiments show a nonlinear ͑nonmetallic͒ conductance at the leakage site, similar to observations by Watanaba et al on silicon oxide films.…”

Nanoscale surface electrical properties of indium–tin–oxide films for organic light emitting diodes investigated by conducting atomic force microscopy

“…The hillock formation is possibly related to field evaporation of the tip material, 13 local oxidation, 14 breakdown. 15 Details of the mechanisms for the structural change, however, are beyond the scope of the present work.…”