Exponential ionic drift: fast switching and low volatility of thin-film memristors

Intrinsic constrains on thermally-assisted memristive switching

“…2 can be used to estimate the radius of the conducting channel in a memristive device given Joule heating information deduced from the experimentally measured resistance increase [2,18] and/or information about the mobile species and reset transition dynamics (i.e. the activation energy for mobile ions and the reset switching time) [25]. This analysis also provides insight into the reset and voltage scaling in unipolar switching devices.…”

“…For example, the internal temperature during the reset operation of various unipolar devices has been estimated by the increase in resistance of the high conductance (metallic) state to be over 1000 K in the case of NiO films [18]. Significantly less heating was observed during switching of bipolar TiO 2−x [2] and SrTiO 3 [11] devices, which may be due to a lower activation energy for the drift of mobile dopants (vacancies or ions) [24,25] that cause the resistance changes. (Note that elevated temperatures during switching are related to state retention and switching speed characteristics of the device since they provide significant nonlinearity of the ionic drift with applied voltage [25,28].)…”

“…Significantly less heating was observed during switching of bipolar TiO 2−x [2] and SrTiO 3 [11] devices, which may be due to a lower activation energy for the drift of mobile dopants (vacancies or ions) [24,25] that cause the resistance changes. (Note that elevated temperatures during switching are related to state retention and switching speed characteristics of the device since they provide significant nonlinearity of the ionic drift with applied voltage [25,28].) Another well-studied class of memristive systems, the phase-change materials, is based on chalcogenide films in which heating by several hundred degrees is required to induce a transition between crystalline and amorphous phases [27].…”

Anomalous effect due to oxygen vacancy accumulation below the electrode in bipolar resistance switching Pt/Nb:SrTiO3 cells

“…5 For the BRS phenomenon in oxides, the same principle is used commonly to explain the relationship between the density variation of V o¨a nd the electronic resistance. 1-4 Using the V o¨m odel, researchers have explained many intriguing BRS phenomena successfully, 6,7 including the resistance state retention time, the switching speed, and the capability to withstand degradation. However, the V o¨m odel also leaves many questions unanswered, because the real spatial distribution of V o¨i nside BRS oxides has rarely been investigated at the nanoscale.…”

Phenomenological modeling of memristive devices

“…Measured changes in the device state upon application of long-duration voltage pulses can be normalized with respect to Dt duration and used reliably for the proposed fitting approach. Additionally, subthreshold behavior might be modeled in ad hoc fashion by introducing an additional term in dynamic equation, e.g., based on activation energy of switching [41]. For example, the model predicts that the switching rate for set transition changes by as little as a factor of 900 when applied voltage is reduced from 1 to 0.5 V, which is not appropriate for true nonvolatile memory.…”