Dynamic observation of oxygen vacancies in hafnia layer by in situ transmission electron microscopy

Direct Observations of Nanofilament Evolution in Switching Processes in HfO2‐Based Resistive Random Access Memory by In Situ TEM Studies

“…When bias is above 3 V, the potential of the AlO y layer changes to nearly zero and then to a negative value. [38,40] As indicated experimentally, the energy loss centers are situated at 24 eV for the filtered image and 4 eV for the energy window, respectively, therefore the 26 eV peak and the 16.4 eV peak are efficiently separated from each other. The retrieved potential maps still illustrate the relic of the charges left in the HfO x film under the preset bias, although they are acquired after the bias has been withdrawn.…”

“…In addition, there is no concrete evidence to prove the electrons flowing in the oxygen-vacancy channel due to the difficulty in directly observing the CF configuration despite of the hypothesis equivalence of the CFs and the oxygen-vacancy channels. [38] Here, the repeatable RS processes in HfO 2based RRAM are investigated by using TEM with electron Electrically induced resistive-switching (RS) phenomena are widely observed in a huge variety of dielectrics each with a metal-insulator-metal structure. [4,10,13,14,18,[33][34][35] Therefore, the direct characterizations of the oxygen vacancies and CF behaviors, including the generation, the evolution and the morphology, are urgently needed to clarify the discrepancy in the CF composition, the formation and disruption dynamics in OxRRAM.…”

“…[36] The charges accumulated in the biased sample can change the phase of the transmitted electron wave, and such a phase disturbance can be retrieved from the electron interference patterns. [38] Here, the repeatable RS processes in HfO 2based RRAM are investigated by using TEM with electron Electrically induced resistive-switching (RS) phenomena are widely observed in a huge variety of dielectrics each with a metal-insulator-metal structure. Moreover, in situ low-energy-filtered images can describe the oxygen concentration changes in the hafnia films.…”

Physical Mechanisms behind the Field‐Cycling Behavior of HfO2‐Based Ferroelectric Capacitors

“…[18] Furthermore, a recent transmission electron microscopy study confirmed the generation and movement of oxygen ions and vacancies within 10 nm thick HfO 2 film under similar operating conditions. [46] Starschich et al just recently proved resistive and ferroelectric switching operation in one and the same Y:HfO 2 -based device. [47] Moreover, not every defect has the energetic and spatial properties to be activated in electron transport or ferroelectric switching on other side.…”

“…[37] Diffusion rates are calculated by considering activation energy for ion and vacancy diffusion of 0.7 and 1.1 eV, respectively. [46,48,49] In the pristine state, we consider that the transitional regions at the dielectric interface have a much higher defect density. This is mainly due to the material intermixing that leads to the formation of a thin ≈1 nm thick substoichiometric TiO x regions, which represent oxidized TiN and does not significantly affect the overall k-value of the stack.…”