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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 experimental current density vs. voltage diagrams of different samples.The diagrams are plotted at the stated voltage sweeping frequencies for an A-sample (a,b) and for a B-sample (c,d); both samples are made of 400 nm thick oxide layers; the respective semi-logarithmic plots of the diagrams are presented as insets. The diagrams obtained for four B-samples with the stated thicknesses (e) match when presented in the current density vs. electric field form (f). All measurements are carried out in clean air with 23% relative humidity at room temperature.
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f2: The experimental current density vs. voltage diagrams of different samples.The diagrams are plotted at the stated voltage sweeping frequencies for an A-sample (a,b) and for a B-sample (c,d); both samples are made of 400 nm thick oxide layers; the respective semi-logarithmic plots of the diagrams are presented as insets. The diagrams obtained for four B-samples with the stated thicknesses (e) match when presented in the current density vs. electric field form (f). All measurements are carried out in clean air with 23% relative humidity at room temperature.

Mentions: The I–V characteristics obtained for an A-sample in the biasing voltage range of +/− 4 V and voltage sweeping frequencies of 1 and 10 Hz are shown in Fig. 2a in both linear and logarithmic scales. The applied voltage is considered positive when the thin film Ti electrode is positively biased with respect to the Ti substrate. The applied electric field, E, is calculated by dividing the applied voltage by the oxide thickness. The characteristics presented in Fig. 2a are consistent with the symmetric structure of the device and zero junction energy barriers at both Ti/TiO2 interfaces383940. A minor departure from symmetry occurs at due to the slightly higher IOV concentration in the oxide layer adjacent to the substrate (Fig. 1b). The dynamic resistivity of the oxide layer, determined from the slope of the linear scale I–V in Fig. 2a, is almost independent from the applied field in the +/−2.0 MV/m range; this resistivity, 1.0 GΩ.cm, defines the high resistance state (HRS) of the A-samples at ca. 2.2 MΩ. The I–V diagrams produced for the same sample at lower voltage sweeping frequencies are presented in Fig. 2b. These diagrams lead to the same HRS values at low applied field levels, but indicate hysteretic behavior and higher conduction levels at defining the low resistance state (LRS) of the device. The LRS measured at 10 MV/m and 0.01 Hz, is 0.5 MΩ. The device current almost doubles at slow voltage sweeping rates (compare a and b in Fig. 2), indicating the appearance of a different conduction route related to mobile ions.


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

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

The experimental current density vs. voltage diagrams of different samples.The diagrams are plotted at the stated voltage sweeping frequencies for an A-sample (a,b) and for a B-sample (c,d); both samples are made of 400 nm thick oxide layers; the respective semi-logarithmic plots of the diagrams are presented as insets. The diagrams obtained for four B-samples with the stated thicknesses (e) match when presented in the current density vs. electric field form (f). All measurements are carried out in clean air with 23% relative humidity at room temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: The experimental current density vs. voltage diagrams of different samples.The diagrams are plotted at the stated voltage sweeping frequencies for an A-sample (a,b) and for a B-sample (c,d); both samples are made of 400 nm thick oxide layers; the respective semi-logarithmic plots of the diagrams are presented as insets. The diagrams obtained for four B-samples with the stated thicknesses (e) match when presented in the current density vs. electric field form (f). All measurements are carried out in clean air with 23% relative humidity at room temperature.
Mentions: The I–V characteristics obtained for an A-sample in the biasing voltage range of +/− 4 V and voltage sweeping frequencies of 1 and 10 Hz are shown in Fig. 2a in both linear and logarithmic scales. The applied voltage is considered positive when the thin film Ti electrode is positively biased with respect to the Ti substrate. The applied electric field, E, is calculated by dividing the applied voltage by the oxide thickness. The characteristics presented in Fig. 2a are consistent with the symmetric structure of the device and zero junction energy barriers at both Ti/TiO2 interfaces383940. A minor departure from symmetry occurs at due to the slightly higher IOV concentration in the oxide layer adjacent to the substrate (Fig. 1b). The dynamic resistivity of the oxide layer, determined from the slope of the linear scale I–V in Fig. 2a, is almost independent from the applied field in the +/−2.0 MV/m range; this resistivity, 1.0 GΩ.cm, defines the high resistance state (HRS) of the A-samples at ca. 2.2 MΩ. The I–V diagrams produced for the same sample at lower voltage sweeping frequencies are presented in Fig. 2b. These diagrams lead to the same HRS values at low applied field levels, but indicate hysteretic behavior and higher conduction levels at defining the low resistance state (LRS) of the device. The LRS measured at 10 MV/m and 0.01 Hz, is 0.5 MΩ. The device current almost doubles at slow voltage sweeping rates (compare a and b in Fig. 2), indicating the appearance of a different conduction route related to mobile ions.

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