Oxide film growth on Fe(111) and scanning tunneling microscopy induced high electric field stress in Fe 2O 3/Fe(111)

Abstract

Oxidation of Fe(111) at 300 and 500 K was studied using Auger electron spectroscopy, low energy electron diffraction and scanning tunneling microscopy (STM) under UHV conditions. Oxidation of the Fe(111) surface at oxygen partial pressures of 1–5×10 −7 Torr resulted in the formation of Fe 2O 3 and Fe 3O 4 at 300 K. At 500 K, however, the predominant oxide phase was Fe 3O 4. STM images showed that the Fe(111) surface was uniformly covered with 5–15 nm wide oxide islands at room temperature oxidation, while oxidation at 500 K resulted in the formation of very large oxide islands (100–300 nm in width) interspersed with patches of uncovered substrate. High electric field stressing studies were carried out via STM under UHV conditions by increasing the bias voltage between the sample and the STM tip under constant current mode on iron oxide formed at both temperatures. Dielectric breakdown of the iron oxide formed at 300 K was induced after applying a high electric field. A critical bias voltage of 3.8±0.5 V was required to induce breakdown of iron oxide formed at 300 K at varying field strengths. No reproducible result was obtained from the high field stress studies of the iron oxide formed at 500 K.