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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.


Piezoresponse images for the polarization reversal process in the nanocapacitor arrays.(a) Topological, and piezoresponse amplitude and phase images for the nanocapacitor array, in which in the middle square area was poled downwards (with a bias voltage of −6 V) while the rest part was upwards with a voltage of +6 V; (b) the piezoresponse phase images illustrating the polarization reversal for a selected nanocapacitor dot, which was poled upwards and then downwards using bias of ±6 V, respectively.
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f3: Piezoresponse images for the polarization reversal process in the nanocapacitor arrays.(a) Topological, and piezoresponse amplitude and phase images for the nanocapacitor array, in which in the middle square area was poled downwards (with a bias voltage of −6 V) while the rest part was upwards with a voltage of +6 V; (b) the piezoresponse phase images illustrating the polarization reversal for a selected nanocapacitor dot, which was poled upwards and then downwards using bias of ±6 V, respectively.

Mentions: To characterize the ferroelectric properties of the nanodots, vertical piezoresponse force microscopy (VPFM) measurements were performed and the results are highlighted in Fig. 3. Fig. 3(a) shows the AFM topography, piezoresponse amplitude- and phase-contrast micrographs for the nanodot arrays. The bright- and dark-contrasts in the phase micrographs correspond to the down-polarization (Pdown) and up-polarization (Pup) states, respectively, while the contrast in amplitude piezoresponse is related to the magnitude of the piezoelectric signal. To show the polarization reversal status, the BFO-SRO nanodot array was first electrically poled by applying an external scanning bias at a pre-designed area during the scan, in which the middle area was poled downwards by a reverse voltage of −6 V, and the rest area upwards with a positive voltage of +6 V. From the phase-contrast micrograph, we can observe completely different dark- and bright-contrast area for the dots of different polarization orientations, indicating that the polarizations of the nanodots are reversible under applied electric voltages. From the piezoresponse amplitude-contrast image, it was found that the amplitude for the downward polarization is slightly smaller than that of upward, exhibiting some extent of preferred polarization orientation. In between the two different polarization regions, there are some dots exhibit low piezoelectric amplitude, which may be correspondent to those in domain border region. It is known that for most reports, the domain wall width in BFO thin films is a few nanometers1519. However, for our BFO nanodots, the domain structure and configuration can be quite different. The free boundary of nanodots imposes additional mechanical and electric boundary conditions which make the domain structure of nanodots much more complicated than that for thin films. For example, one can observe upward, downward, bubble-like, vortex-like, and stripe-like domain patterns in nanodots. In these cases, the domain wall width, if definable, may be much wider than those in thin films. Therefore, we can only see a bounder region in our nanodot array, instead of a sharp boundary. To demonstrate the reversibility of an individual dot, we applied a pulsed voltage of ±6 V on a selected dot, which produces apparent different contrasts for the two different pulsed voltages, as shown in Fig. 3(b). This confirms that the isolated dot is switchable in polarization by applying a pulsed voltage.


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)

Piezoresponse images for the polarization reversal process in the nanocapacitor arrays.(a) Topological, and piezoresponse amplitude and phase images for the nanocapacitor array, in which in the middle square area was poled downwards (with a bias voltage of −6 V) while the rest part was upwards with a voltage of +6 V; (b) the piezoresponse phase images illustrating the polarization reversal for a selected nanocapacitor dot, which was poled upwards and then downwards using bias of ±6 V, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Piezoresponse images for the polarization reversal process in the nanocapacitor arrays.(a) Topological, and piezoresponse amplitude and phase images for the nanocapacitor array, in which in the middle square area was poled downwards (with a bias voltage of −6 V) while the rest part was upwards with a voltage of +6 V; (b) the piezoresponse phase images illustrating the polarization reversal for a selected nanocapacitor dot, which was poled upwards and then downwards using bias of ±6 V, respectively.
Mentions: To characterize the ferroelectric properties of the nanodots, vertical piezoresponse force microscopy (VPFM) measurements were performed and the results are highlighted in Fig. 3. Fig. 3(a) shows the AFM topography, piezoresponse amplitude- and phase-contrast micrographs for the nanodot arrays. The bright- and dark-contrasts in the phase micrographs correspond to the down-polarization (Pdown) and up-polarization (Pup) states, respectively, while the contrast in amplitude piezoresponse is related to the magnitude of the piezoelectric signal. To show the polarization reversal status, the BFO-SRO nanodot array was first electrically poled by applying an external scanning bias at a pre-designed area during the scan, in which the middle area was poled downwards by a reverse voltage of −6 V, and the rest area upwards with a positive voltage of +6 V. From the phase-contrast micrograph, we can observe completely different dark- and bright-contrast area for the dots of different polarization orientations, indicating that the polarizations of the nanodots are reversible under applied electric voltages. From the piezoresponse amplitude-contrast image, it was found that the amplitude for the downward polarization is slightly smaller than that of upward, exhibiting some extent of preferred polarization orientation. In between the two different polarization regions, there are some dots exhibit low piezoelectric amplitude, which may be correspondent to those in domain border region. It is known that for most reports, the domain wall width in BFO thin films is a few nanometers1519. However, for our BFO nanodots, the domain structure and configuration can be quite different. The free boundary of nanodots imposes additional mechanical and electric boundary conditions which make the domain structure of nanodots much more complicated than that for thin films. For example, one can observe upward, downward, bubble-like, vortex-like, and stripe-like domain patterns in nanodots. In these cases, the domain wall width, if definable, may be much wider than those in thin films. Therefore, we can only see a bounder region in our nanodot array, instead of a sharp boundary. To demonstrate the reversibility of an individual dot, we applied a pulsed voltage of ±6 V on a selected dot, which produces apparent different contrasts for the two different pulsed voltages, as shown in Fig. 3(b). This confirms that the isolated dot is switchable in polarization by applying a pulsed voltage.

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.