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Current rectifying and resistive switching in high density BiFeO3 nanocapacitor arrays on Nb-SrTiO3 substrates.

Zhao L, Lu Z, Zhang F, Tian G, Song X, Li Z, Huang K, Zhang Z, Qin M - Sci Rep (2015)

Bottom Line: These capacitors also show reversible polarization domain structures, and well-established piezoresponse hysteresis loops.Moreover, apparent current-rectification and resistive switching behaviors were identified in these nanocapacitor cells using conductive-AFM technique, which are attributed to the polarization modulated p-n junctions.These make it possible to utilize these nanocapacitors in high-density (>100 Gbit/inch(2)) nonvolatile memories and other oxide nanoelectronic devices.

View Article: PubMed Central - PubMed

Affiliation: Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China.

ABSTRACT
Ultrahigh density well-registered oxide nanocapacitors are very essential for large scale integrated microelectronic devices. We report the fabrication of well-ordered multiferroic BiFeO3 nanocapacitor arrays by a combination of pulsed laser deposition (PLD) method and anodic aluminum oxide (AAO) template method. The capacitor cells consist of BiFeO3/SrRuO3 (BFO/SRO) heterostructural nanodots on conductive Nb-doped SrTiO3 (Nb-STO) substrates with a lateral size of ~60 nm. These capacitors also show reversible polarization domain structures, and well-established piezoresponse hysteresis loops. Moreover, apparent current-rectification and resistive switching behaviors were identified in these nanocapacitor cells using conductive-AFM technique, which are attributed to the polarization modulated p-n junctions. These make it possible to utilize these nanocapacitors in high-density (>100 Gbit/inch(2)) nonvolatile memories and other oxide nanoelectronic devices.

No MeSH data available.


Schematic energy band for the conducting mechanism.(a) Energy band diagram for the whole SRO/BFO/Nb-STO heterojunction; (b, c) present the schematic band diagrams for a p-n junction at two different ferroelectric polarization directions, with downward polarization state (b) and upward polarization state (c), corresponding to the LRS and HRS, respectively.
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f6: Schematic energy band for the conducting mechanism.(a) Energy band diagram for the whole SRO/BFO/Nb-STO heterojunction; (b, c) present the schematic band diagrams for a p-n junction at two different ferroelectric polarization directions, with downward polarization state (b) and upward polarization state (c), corresponding to the LRS and HRS, respectively.

Mentions: Fig. 6(a) gives a schematic equilibrium band structure of the SRO/BFO/Nb-STO heterojunction, which is a typical staggered energy band diagram. Nb-STO has an energy band gap of 3.2 eV and an electron affinity of 4 eV25, while BFO has energy band gap of 2.8 eV and an electron affinity of 3.3 eV26. BFO forms a staggered energy band diagram with Nb-STO, while Nb-STO has high conductivity and its Fermi level is close to the bottom of the conduction band. For a non-degenerated semiconductor, the Fermi level is at least 3 kT above the energy level of valance band of (EV) or 3 kT below the energy level of conductive band (EC). Therefore the work-function of Nb-STO is deduced to be (4 + 3 kT + x) = (4.08 + x) eV, where x is a small value21. BFO has high resistivity, its Fermi level is close to or below the middle of the energy band gap, so the work-function of BFO is deduced to be (3.3 + 1.4 + y) eV, where y is another small value2126. The work-function of SRO is ~5.2 eV22. The built-in voltage Vbi can be deduced as the difference between the work-functions Vbi(SRO/BFO) = 5.2 − (4.7 + y) ~ 0.5 V, and Vbi(BFO/Nb-STO) = (4.7 + y) − (4.08 + x) ~ 0.62 V. The two built-in voltages are alighted along the same direction, leading to a big total built-in voltage of ~1.1 V, which can account for the apparent asymmetry and large imprint field of 0.84 V in piezoresponse loops shown in Fig. 4.


Current rectifying and resistive switching in high density BiFeO3 nanocapacitor arrays on Nb-SrTiO3 substrates.

Zhao L, Lu Z, Zhang F, Tian G, Song X, Li Z, Huang K, Zhang Z, Qin M - Sci Rep (2015)

Schematic energy band for the conducting mechanism.(a) Energy band diagram for the whole SRO/BFO/Nb-STO heterojunction; (b, c) present the schematic band diagrams for a p-n junction at two different ferroelectric polarization directions, with downward polarization state (b) and upward polarization state (c), corresponding to the LRS and HRS, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389717&req=5

f6: Schematic energy band for the conducting mechanism.(a) Energy band diagram for the whole SRO/BFO/Nb-STO heterojunction; (b, c) present the schematic band diagrams for a p-n junction at two different ferroelectric polarization directions, with downward polarization state (b) and upward polarization state (c), corresponding to the LRS and HRS, respectively.
Mentions: Fig. 6(a) gives a schematic equilibrium band structure of the SRO/BFO/Nb-STO heterojunction, which is a typical staggered energy band diagram. Nb-STO has an energy band gap of 3.2 eV and an electron affinity of 4 eV25, while BFO has energy band gap of 2.8 eV and an electron affinity of 3.3 eV26. BFO forms a staggered energy band diagram with Nb-STO, while Nb-STO has high conductivity and its Fermi level is close to the bottom of the conduction band. For a non-degenerated semiconductor, the Fermi level is at least 3 kT above the energy level of valance band of (EV) or 3 kT below the energy level of conductive band (EC). Therefore the work-function of Nb-STO is deduced to be (4 + 3 kT + x) = (4.08 + x) eV, where x is a small value21. BFO has high resistivity, its Fermi level is close to or below the middle of the energy band gap, so the work-function of BFO is deduced to be (3.3 + 1.4 + y) eV, where y is another small value2126. The work-function of SRO is ~5.2 eV22. The built-in voltage Vbi can be deduced as the difference between the work-functions Vbi(SRO/BFO) = 5.2 − (4.7 + y) ~ 0.5 V, and Vbi(BFO/Nb-STO) = (4.7 + y) − (4.08 + x) ~ 0.62 V. The two built-in voltages are alighted along the same direction, leading to a big total built-in voltage of ~1.1 V, which can account for the apparent asymmetry and large imprint field of 0.84 V in piezoresponse loops shown in Fig. 4.

Bottom Line: These capacitors also show reversible polarization domain structures, and well-established piezoresponse hysteresis loops.Moreover, apparent current-rectification and resistive switching behaviors were identified in these nanocapacitor cells using conductive-AFM technique, which are attributed to the polarization modulated p-n junctions.These make it possible to utilize these nanocapacitors in high-density (>100 Gbit/inch(2)) nonvolatile memories and other oxide nanoelectronic devices.

View Article: PubMed Central - PubMed

Affiliation: Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China.

ABSTRACT
Ultrahigh density well-registered oxide nanocapacitors are very essential for large scale integrated microelectronic devices. We report the fabrication of well-ordered multiferroic BiFeO3 nanocapacitor arrays by a combination of pulsed laser deposition (PLD) method and anodic aluminum oxide (AAO) template method. The capacitor cells consist of BiFeO3/SrRuO3 (BFO/SRO) heterostructural nanodots on conductive Nb-doped SrTiO3 (Nb-STO) substrates with a lateral size of ~60 nm. These capacitors also show reversible polarization domain structures, and well-established piezoresponse hysteresis loops. Moreover, apparent current-rectification and resistive switching behaviors were identified in these nanocapacitor cells using conductive-AFM technique, which are attributed to the polarization modulated p-n junctions. These make it possible to utilize these nanocapacitors in high-density (>100 Gbit/inch(2)) nonvolatile memories and other oxide nanoelectronic devices.

No MeSH data available.