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Electronic Conduction in Ti/Poly-TiO2/Ti Structures.

Hossein-Babaei F, Alaei-Sheini N - Sci Rep (2016)

Bottom Line: Containing no interface energy barrier, Ti/poly-TiO2/Ti devices demonstrate high resistance ohmic conduction at biasing fields below 5 × 10(6) V.m(-1); higher fields drive the samples to a distinctly nonlinear and hysteretic low resistance status.The observed threshold is two orders of magnitude smaller than the typical resistance switching fields reported for the nanosized single grain memristors.This is consistent with the smaller activation energies reported for the IOV motion on the rutile facets than its interior.

View Article: PubMed Central - PubMed

Affiliation: Electronic Materials Laboratory, Electrical Engineering Department, K. N. Toosi University of Technology, Tehran 16317-14191, Iran.

ABSTRACT
Recent intensive investigations on metal/metal oxide/metal structures have targeted nanometric single grain oxides at high electric fields. Similar research on thicker polycrystalline oxide layers can bridge the results to the prior literature on varistors and may uncover novel ionic/electronic features originating from the conduction mechanisms involving grain boundaries. Here, we investigate electronic conduction in Ti/poly-TiO2-x/Ti structures with different oxygen vacancy distributions and describe the observed features based on the motion and rearrangement of the ionized oxygen vacancies (IOVs) on the grain facets rather than the grain interiors. Containing no interface energy barrier, Ti/poly-TiO2/Ti devices demonstrate high resistance ohmic conduction at biasing fields below 5 × 10(6) V.m(-1); higher fields drive the samples to a distinctly nonlinear and hysteretic low resistance status. The observed threshold is two orders of magnitude smaller than the typical resistance switching fields reported for the nanosized single grain memristors. This is consistent with the smaller activation energies reported for the IOV motion on the rutile facets than its interior. The presented model describes the observed dependence of the threshold field on the relative humidity of the surrounding air based on the lower activation energies reported for the hydroxyl-assisted IOV motion on the rutile facets.

No MeSH data available.


Related in: MedlinePlus

The transient responses of the samples to the sudden changes in the biasing voltage.(a) The variations of current in an A-sample (green) and a B-sample (red) in response to a step function biasing voltage (blue), the inset magnifies the responses just after field application. The small AC voltage added to the step function and the recorded AC currents are utilized for dynamic resistance calculations. (b) The AC current decay in a B-sample (red) after the sudden removal of the DC bias (blue); although the AC bias has been kept intact, the AC current drops 30 times in less than 10−3 s after DC field removal; the inset depicts the gradual diminishing of the residue AC current as the device acquires its HRS. (c) The same as (b) carried out for an A-sample.
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f6: The transient responses of the samples to the sudden changes in the biasing voltage.(a) The variations of current in an A-sample (green) and a B-sample (red) in response to a step function biasing voltage (blue), the inset magnifies the responses just after field application. The small AC voltage added to the step function and the recorded AC currents are utilized for dynamic resistance calculations. (b) The AC current decay in a B-sample (red) after the sudden removal of the DC bias (blue); although the AC bias has been kept intact, the AC current drops 30 times in less than 10−3 s after DC field removal; the inset depicts the gradual diminishing of the residue AC current as the device acquires its HRS. (c) The same as (b) carried out for an A-sample.

Mentions: The formation and dissolution mechanisms of IOV filaments are probed by the application of a small AC voltage (Vrms = 0.1 V) to the device operating at different DC biasing conditions. The current variations when 2 V step voltages are applied to A- and B-samples are presented in Fig. 6. In A-samples, the current density rises in less than a second to a stable level at 1.5 × 10−5 A/mm2. In B-samples, however, after a similar fast rise (see the inset in Fig. 6a), the current density increases continuously with time for ~103 s to reach a saturation level at ~20 times above its primary fast rise. Both of these observations are consistent with the filament formation mechanism described above. In both samples, the conduction initiates based on the IOV population present in the grain boundary region, which acquire their minimum resistance format in a second. This is almost the end of the story for A-samples wherein the current increases slightly with time because of the current path enhancement by the IOVs joining the path from the neighboring areas. In B-samples, however, the field-assisted migration of IOVs from the vacancy-rich anode region broadens the filament and gradually enhances the conduction path.


Electronic Conduction in Ti/Poly-TiO2/Ti Structures.

Hossein-Babaei F, Alaei-Sheini N - Sci Rep (2016)

The transient responses of the samples to the sudden changes in the biasing voltage.(a) The variations of current in an A-sample (green) and a B-sample (red) in response to a step function biasing voltage (blue), the inset magnifies the responses just after field application. The small AC voltage added to the step function and the recorded AC currents are utilized for dynamic resistance calculations. (b) The AC current decay in a B-sample (red) after the sudden removal of the DC bias (blue); although the AC bias has been kept intact, the AC current drops 30 times in less than 10−3 s after DC field removal; the inset depicts the gradual diminishing of the residue AC current as the device acquires its HRS. (c) The same as (b) carried out for an A-sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940738&req=5

f6: The transient responses of the samples to the sudden changes in the biasing voltage.(a) The variations of current in an A-sample (green) and a B-sample (red) in response to a step function biasing voltage (blue), the inset magnifies the responses just after field application. The small AC voltage added to the step function and the recorded AC currents are utilized for dynamic resistance calculations. (b) The AC current decay in a B-sample (red) after the sudden removal of the DC bias (blue); although the AC bias has been kept intact, the AC current drops 30 times in less than 10−3 s after DC field removal; the inset depicts the gradual diminishing of the residue AC current as the device acquires its HRS. (c) The same as (b) carried out for an A-sample.
Mentions: The formation and dissolution mechanisms of IOV filaments are probed by the application of a small AC voltage (Vrms = 0.1 V) to the device operating at different DC biasing conditions. The current variations when 2 V step voltages are applied to A- and B-samples are presented in Fig. 6. In A-samples, the current density rises in less than a second to a stable level at 1.5 × 10−5 A/mm2. In B-samples, however, after a similar fast rise (see the inset in Fig. 6a), the current density increases continuously with time for ~103 s to reach a saturation level at ~20 times above its primary fast rise. Both of these observations are consistent with the filament formation mechanism described above. In both samples, the conduction initiates based on the IOV population present in the grain boundary region, which acquire their minimum resistance format in a second. This is almost the end of the story for A-samples wherein the current increases slightly with time because of the current path enhancement by the IOVs joining the path from the neighboring areas. In B-samples, however, the field-assisted migration of IOVs from the vacancy-rich anode region broadens the filament and gradually enhances the conduction path.

Bottom Line: Containing no interface energy barrier, Ti/poly-TiO2/Ti devices demonstrate high resistance ohmic conduction at biasing fields below 5 × 10(6) V.m(-1); higher fields drive the samples to a distinctly nonlinear and hysteretic low resistance status.The observed threshold is two orders of magnitude smaller than the typical resistance switching fields reported for the nanosized single grain memristors.This is consistent with the smaller activation energies reported for the IOV motion on the rutile facets than its interior.

View Article: PubMed Central - PubMed

Affiliation: Electronic Materials Laboratory, Electrical Engineering Department, K. N. Toosi University of Technology, Tehran 16317-14191, Iran.

ABSTRACT
Recent intensive investigations on metal/metal oxide/metal structures have targeted nanometric single grain oxides at high electric fields. Similar research on thicker polycrystalline oxide layers can bridge the results to the prior literature on varistors and may uncover novel ionic/electronic features originating from the conduction mechanisms involving grain boundaries. Here, we investigate electronic conduction in Ti/poly-TiO2-x/Ti structures with different oxygen vacancy distributions and describe the observed features based on the motion and rearrangement of the ionized oxygen vacancies (IOVs) on the grain facets rather than the grain interiors. Containing no interface energy barrier, Ti/poly-TiO2/Ti devices demonstrate high resistance ohmic conduction at biasing fields below 5 × 10(6) V.m(-1); higher fields drive the samples to a distinctly nonlinear and hysteretic low resistance status. The observed threshold is two orders of magnitude smaller than the typical resistance switching fields reported for the nanosized single grain memristors. This is consistent with the smaller activation energies reported for the IOV motion on the rutile facets than its interior. The presented model describes the observed dependence of the threshold field on the relative humidity of the surrounding air based on the lower activation energies reported for the hydroxyl-assisted IOV motion on the rutile facets.

No MeSH data available.


Related in: MedlinePlus