Ferroelectric–carbon nanotube memory devices

Kumar, Ashok; Shivareddy, Sai G; Correa, Margarita; Resto, O.; Choi, Young–Jin; Cole, Matthew T.; Katiyar, Ram S.; Scott, J. F.; Amaratunga, G.A.J.; Lu, Haidong; Gruverman, Alexei

doi:10.1088/0957-4484/23/16/165702

Cited by 22 publications

(15 citation statements)

References 32 publications

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“…It is of recent interest to fabricate functional ferroelectrics as end units onto both carbon nanotubes and graphene sheets [291][292][293][294][295]. The latter can serve as an FET gate, replacing the conventional Si/SiO 2 (see "carbon-ferroelectric gates") [296].…”

Section: Combinations With Graphene and With Carbon Nanotubesmentioning

confidence: 99%

Prospects for Ferroelectrics: 2012–2022

Scott

2013

ISRN Materials Science

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Section: Combinations With Graphene and With Carbon Nanotubesmentioning

confidence: 99%

Prospects for Ferroelectrics: 2012–2022

Scott

2013

ISRN Materials Science

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“…In addition, the other competitors for the next generation of computer memories all have their own problems: ferroelectric nanotubes [7][8][9][10][11][12][13][14][15][16] are mechanically not very robust nor easy to manufacture with high yields; phase-change memories 17 have a small operating temperature range unsuited for either military or automotive specifications and too large a thermal budget; however, Samsung has had a 512-Mb phase-change random access memory (PRAM) in production since 2006. MRAMs 18 have problems with cross-talk if not isolated bit-by-bit with space-demanding pass-gate transistors, which are undesirable with respect to cost and 'footprint' size on the chips; however, MRAMs are also good commercial memories with Everspin producing a 4-Mb part.…”

Section: Introductionmentioning

confidence: 99%

Room-temperature multiferroic magnetoelectrics

2013

Self Cite

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A short review is given of the recent work on single-phase crystals that are ferroelectric and ferromagnetic at or near room temperature. BiFeO 3 is mentioned only briefly, because it has been reviewed in detail elsewhere very recently; emphasis instead is on copper oxide, perovskite oxides with mixed B-site occupancy (such as Pb(Fe 1/2 Ta 1/2 ) x (Zr y Ti INTRODUCTIONMultiferroics are usually defined as single-phase crystals exhibiting at the same temperature and pressure both ferromagnetism (or antiferromagnetism) and ferroelectricity (or antiferroelectricity). As most ferroelectrics are also ferroelastic 1 (hysteretic stress-strain relationships), the 'multi-ferro' label often includes three coupled order parameters. (As a peripheral comment, we note that it is necessary and sufficient 2 for a ferroelectric to be ferroelastic if its phase transition changes the crystal class-for example, from orthorhombic to tetragonal-treating hexagonal and trigonal as a single super-class. Examples of nonferroelastic ferroelectrics include KTiOPO 4 and LiNbO 3 , whose ferroelectric transitions are, respectively, orhorhombic-orthorhombic and trigonal-trigonal.)The interest in multiferroics at present is growing rapidly, and the interest is twofold: from a fundamental point of view the coupling between spins and lattices in crystals-between magnetism and ferroelectricity and/or structural phase transitions-has been recognized as complex and fascinating for several decades, generally requiring low-symmetry materials that were carefully avoided in earlier days of solid state theory. A good reason why it is presented in the elegant work by Schmid and Trooster 3 on the boracites: These materials (for example, nickel-iodine boracite) are multiferroic only at cryogenic temperatures and grow in needle-like structures, making them impractical for commercial device applications; and theoretically they exhibit low symmetry (monoclinic or triclinic) and have as many as 96 atoms per unit cell, making them theoretically formidable. Despite these drawbacks, multiferroics present a possible avenue for the next generation of computer digital memories, combining at least in principle, the high-speed and low-power consumption 4,5 of a ferroelectric random access memory (FRAM) with the nondestructive READ operation of a magnetic RAM. We discuss below why these goals will not be easy to achieve in commercial products:The most serious problems are operational temperature (most multiferroics operate well below ambient) and magnitudes of magnetization (all multiferroics with reasonably high operating temperatures are weak ferromagnets-canted antiferromagnetswhereas a strong ferromagnet is desired), and the switched polarization is also extremely weak. The polarization in most multiferroics is so weak that authors measure it in nC m À2 rather than the older customary mC cm À2 . Keep in mind that equally good SI units would be C hectare À1 for these multiferroics, a value far lower than the roughly 1 mC cm À2 required by a computer memory sense ampl...

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“…[3][4][5][6][7] However, in the last years only a few reports on the investigation of multiwall carbon nanotubes (MWCNT) covered with ferroelectrics for 3D capacitors and related applications have been published. 4,5,[8][9][10] The use of MWCNT for this application is limited by the requirement to process ferroelectrics at high temperatures (> 600 ºC) in oxidizing atmospheres which results in an exothermic reaction. From our previous studies on the thermal stability of MWCNT in different atmospheres, we have demonstrated that MWCNTs are stable up to 420 o C in air but in higher P(O 2 ), they oxidise at ≥ 200 o C. However, in low P(O 2 ) (flowing Ar gas) MWCNTs can remain stable up to 1300 o C with minimum sublimation 11 .…”

Section: Introductionmentioning

confidence: 99%

Unveiling the Role of CNTs in the Phase Formation of One-Dimensional Ferroelectrics

Mahajan

Reaney

Costa³

et al. 2015

Langmuir

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Carbon nanotubes (CNTs) have the potential to act as templates or bottom electrodes for three-dimensional (3D) capacitor arrays, which utilize one-dimensional (1D) ferroelectric nanostructures to increase the memory size and density. However, growing a ferroelectric on the surface of CNTs is nontrivial. Here, we demonstrate that multiwalled (MW) CNTs decrease the time and temperature for the formation of lead zirconium titanate Pb(Zr1-xTix)O3 (PZT) by ∼100 °C commensurate with a decrease in activation energy from 68 ± 15 to 27 ± 2 kJ/mol. As a consequence, monophasic PZT was obtained at 575 °C for MWCNTs/PZT, but for pure PZT, traces of pyrochlore were still present at 650 °C, where the PZT phase formed due to homogeneous nucleation. The piezoelectric nature of MWCNTs/PZT synthesized at 500 °C for 1 h was proven. Although further work is required to prove the concept of 3D capacitor arrays, our result suggests that it is feasible to utilize MWCNTs as templates/electrodes for the formation of 1D PZT nanoferroelectrics.

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Ferroelectric–carbon nanotube memory devices

Cited by 22 publications

References 32 publications

Prospects for Ferroelectrics: 2012–2022

Prospects for Ferroelectrics: 2012–2022

Room-temperature multiferroic magnetoelectrics

Unveiling the Role of CNTs in the Phase Formation of One-Dimensional Ferroelectrics

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