Current status and challenges of ferroelectric memory devices

Kohlstedt, H.; Mustafa, Yacoub; Gerber, Andreas; Petraru, A.; Fitsilis, M.; Meyer, René; Böttger, U.; Waser, Rainer

doi:10.1016/j.mee.2005.04.084

Cited by 156 publications

(76 citation statements)

References 36 publications

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“…Unfortunately up to now nothing is known about superparaelectric phase in ferroelectric nanoparticles, also the term "superparaelectric" was used for description of bulk ferroelectric relaxors. 5 , 6 There were the attempts to apply the term to ferroelectric film 7 and to the ferroelectric nanoparticles. 8 However the observed properties were characteristic mainly to paraelectric phase rather than to superparaelectric one.…”

Section: Introductionmentioning

confidence: 99%

Superparaelectric phase in the ensemble of noninteracting ferroelectric nanoparticles

2008

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For the first time we predict the conditions of superparaelectric phase appearance in the ensemble of non-interacting spherical ferroelectric nanoparticles. The superparaelectricity in nanoparticle was defined by analogy with superparamagnetism, obtained earlier in small nanoparticles made of paramagnetic material.Calculations of correlation radius, energetic barriers of polarization reorientation and polarization response to external electric field, performed within Landau-Ginzburg phenomenological approach for perovskites Pb(Zr,Ti)O 3 , BiFeO 3 and uniaxial ferroelectrics rochelle salt and triglycine sulfate, proved that under the favorable conditions ensemble of their noninteracting nanoparticles possesses the following characteristic features. Namely:(1) When the particle radius R is less than the correlation radius R c , but higher than the critical radius R cr of size-driven ferroelectric-paraelectric phase transition, all dipole moments inside the particle are aligned due to the correlation effects.(2) Potential barrier ∆F(T,R) of polarization reorientation can be smaller than thermal activation energy at temperatures T higher than the freezing temperature T f (R) depending the particle radius R. Freezing temperature T f (R) can be estimated from the condition ∆F(T,R) = γk B T. Such determination is somehow voluntary, since the rigorous value of T f (R) depends on numerical factor γ before k B T, which depends on the system characteristics.(3) Langevin-like law for polarization dependence on external field is obtained at temperatures higher than the freezing temperature T f (R), but lower than the temperature T cr (R) of size-driven ferroelectric-paraelectric phase transition.(4) Ferroelectric hysteresis loop and remnant polarization appear at temperatures T lower than the freezing temperature T f (R). This behaviour can be named as frozen superparaelectric phase.The conditions (1)-(4) determine the superparaelectric phase appearance in the ensemble of ferroelectric nanoparticles of radius R cr < R < R c at temperatures T f (R) < T < T cr (R). The favorable conditions for the superparaelectricity observation in small ferroelectric nanoparticles * Corresponding author: morozo@i.com.ua; permanent address: V. Lashkarev Institute of Semiconductor Physics, NAS of Ukraine, 41, pr. Nauki, 03028 Kiev, Ukraine 1 at room temperatures are small Curie-Weiss constants and high nonlinear coefficients as follows from the condition (2). The theoretical forecast is waiting for experimental revealing.

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Section: Introductionmentioning

confidence: 99%

Superparaelectric phase in the ensemble of noninteracting ferroelectric nanoparticles

2008

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“…The figure 1 shows a schematic drawing of the FeRAM structure [14]. The unit cell was formed by one transistor and one ferroelectric capacitor which were connected in parallel, during the operation, one capacitor was selected randomly by cutting off it's pare transistor.…”

Section: Feram 'S Structurementioning

confidence: 99%

Effect of Phase Transition Temperature of Bati0.9Sn0.1o3 on the Operating Mode of Ferroelectricrandom Access Memories (FeRAM)

Ourrad¹

2013

IJMSA

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Abstract:The outstanding dielectric, ferroelectric and piezoelectric properties of BaTiO 3 make it the desirable primary material for a variety of applications such as nonvolatile memories (RAM). At the Curie's temperature the dielectric properties of BaTiO 3 undergo phase transition. The Landau-Devonshire's phenomenological theory has been investigated in this paper to present the relation between the temperature and the electric induction. The effect of the variation of electric induction versus temperature of BaTi 0.9 Sn 0.1 O 3 investigated in the fabrication of nonvolatile ferroelectric random access memories (FeRAM) which may lead us to discover a strange phenomenon called «determinist chaos », now the FeRAM lose its reliability.

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“…A further increase of the reliability and a decrease of the necessary processing temperatures, which are of particular importance for the integration of functional ferroelectrics into the Si-CMOS technology are superior aims [4,24]. Thus a detailed understanding of the microscopic chemical processes on the pathway from the initial precursor solution to the crystalline film is mandatory.…”

Section: While Metal-organic Chemical Vapor Deposition (Mocvd) Is a Kmentioning

confidence: 99%

Investigation of the amorphous to crystalline phase transition of chemical solution deposited Pb(Zr0.3Ti0.7)O3 thin films by soft X-ray absorption and soft X-ray emission spectroscopy

Schneller

Kohlstedt

Petraru

et al. 2008

J Sol-Gel Sci Technol

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Abstract:Chemical solution deposited (CSD) complex oxide thin films attract considerable interest in various emerging fields as for example, fuel cells, ferroelectric random access memories or coated conductors. In the present paper the results of soft-x-ray spectroscopy between 100 eV and 500 eV on the amorphous to crystalline phase transition of ferroelectric PbZr 0.3 Ti 0.7 O 3 (PZT) thin films are presented. Five CSD samples derived from the same wafer coated with a PZT film pyrolyzed at 350 °C were heat treated at different temperatures between 400 °C and 700 °C. At first the sample were morphologically and electrically characterized. Subsequently the soft-x-ray absorption and emission experiments were performed at the undulator beamline 8.0 of the Advanced Light Source of the Lawrence Berkeley National Laboratory. Soft-x-ray absorption spectra were acquired for the Ti L 2,3 -, O K-, and C K-edge thresholds by using simultaneously the total electron yield (TEY) and total fluorescence yield (TFY) detection methods. For two samples, annealed at 400 °C and 700 °C, respectively, the resonant inelastic soft-x-ray 2 spectroscopy (RIXS) was applied for various excitation energies near the Ti L-, O K-edges. We observed clear evidence of a rutile phase at untypically low temperatures. This rutile phase transforms into the perovskite phase upon increasing annealing temperature. These results are discussed in the framework of current microscopic models of the PZT (111) texture selection.

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Current status and challenges of ferroelectric memory devices

Cited by 156 publications

References 36 publications

Superparaelectric phase in the ensemble of noninteracting ferroelectric nanoparticles

Superparaelectric phase in the ensemble of noninteracting ferroelectric nanoparticles

Effect of Phase Transition Temperature of Bati0.9Sn0.1o3 on the Operating Mode of Ferroelectricrandom Access Memories (FeRAM)

Investigation of the amorphous to crystalline phase transition of chemical solution deposited Pb(Zr0.3Ti0.7)O3 thin films by soft X-ray absorption and soft X-ray emission spectroscopy

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