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Effect of mechanical loads on stability of nanodomains in ferroelectric ultrathin films: towards flexible erasing of the non-volatile memories.

Chen WJ, Zheng Y, Xiong WM, Feng X, Wang B, Wang Y - Sci Rep (2014)

Bottom Line: It is found that the stability of a cylindrical domain depends on its radius, temperature and film thickness.Based on the calculated phase diagrams, we successfully simulate several mechanical erasing processes on 4 × 4 bits memory devices.Our study sheds light on prospective device applications of ferroelectrics involving mechanical loads, such as flexible memory devices and other micro-electromechanical systems.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China [2] Micro&Nano Physics and Mechanics Research Laboratory, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China.

ABSTRACT
Intensive investigations have been drawn on nanoscale ferroelectrics for their prospective applications such as developing memory devices. In contrast with the commonly used electrical means to process (i.e., read, write or erase) the information carried by ferroelectric domains, at present, mechanisms of non-electrical processing ferroelectric domains are relatively lacking. Here we make a systematical investigation on the stability of 180° cylindrical domains in ferroelectric nanofilms subjected to macroscopic mechanical loads, and explore the possibility of mechanical erasing. Effects of domain size, film thickness, temperature and different mechanical loads, including uniform strain, cylindrical bending and wavy bending, have been revealed. It is found that the stability of a cylindrical domain depends on its radius, temperature and film thickness. More importantly, mechanical loads have great controllability on the stability of cylindrical domains, with the critical radius nonlinearly sensitive to both strain and strain gradient. This indicates that erasing cylindrical domain can be achieved by changing the strain state of nanofilm. Based on the calculated phase diagrams, we successfully simulate several mechanical erasing processes on 4 × 4 bits memory devices. Our study sheds light on prospective device applications of ferroelectrics involving mechanical loads, such as flexible memory devices and other micro-electromechanical systems.

No MeSH data available.


Related in: MedlinePlus

Control of domain stability by wavy bending.Control of domain stability by wavy bending on 128 nm × 128 nm × 8 nm simulation cells at room temperature. The cells are initially written with cylindrical domains with size r from 1 nm to 64 nm. (a) Schematics of a cell under wavy bending, i.e., , with λ = 128 nm. Distribution of (b)  and (c) flexoelectric field  as a function of Ab in the x-z plane of a cell under wavy bending. Phase diagrams of equilibrium domain pattern in cells under wavy bending with flexoelectric field (d) switched off and (e) on. (f) and (g) The average polarization of the equilibrium domain patterns in z-direction, i.e., <P3>, in the initial cylindrical domain region, for the two bending cases.
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f6: Control of domain stability by wavy bending.Control of domain stability by wavy bending on 128 nm × 128 nm × 8 nm simulation cells at room temperature. The cells are initially written with cylindrical domains with size r from 1 nm to 64 nm. (a) Schematics of a cell under wavy bending, i.e., , with λ = 128 nm. Distribution of (b) and (c) flexoelectric field as a function of Ab in the x-z plane of a cell under wavy bending. Phase diagrams of equilibrium domain pattern in cells under wavy bending with flexoelectric field (d) switched off and (e) on. (f) and (g) The average polarization of the equilibrium domain patterns in z-direction, i.e., <P3>, in the initial cylindrical domain region, for the two bending cases.

Mentions: The investigated mechanical loading conditions so far are with uniform strain or uniform strain gradient. It has been recently demonstrated that a wavy bending configuration of ferroelectric nanofilm can be achieved by integrating it on prestrained elastomeric supports, which is important for developing flexible ferroelectric devices1516 Considering the fact that the strain gradient of wavy bending is not uniform, an exploration on its effect is not trivial to the cases of uniform strain and uniform strain gradient. For a nanofilm with a wavy bending along x-direction (Figure 6a), its strain state can be approximately described by a cosine form strain, i.e., , where Ab is wave amplitude, characterizing the largest defection of the nanofilm from its neutral plane z = h/2, and λ is the wave length along the x-direction. Note that for simplicity we fix the neutral plane at middle plane of the film to only consider the case of zero membrane strain.


Effect of mechanical loads on stability of nanodomains in ferroelectric ultrathin films: towards flexible erasing of the non-volatile memories.

Chen WJ, Zheng Y, Xiong WM, Feng X, Wang B, Wang Y - Sci Rep (2014)

Control of domain stability by wavy bending.Control of domain stability by wavy bending on 128 nm × 128 nm × 8 nm simulation cells at room temperature. The cells are initially written with cylindrical domains with size r from 1 nm to 64 nm. (a) Schematics of a cell under wavy bending, i.e., , with λ = 128 nm. Distribution of (b)  and (c) flexoelectric field  as a function of Ab in the x-z plane of a cell under wavy bending. Phase diagrams of equilibrium domain pattern in cells under wavy bending with flexoelectric field (d) switched off and (e) on. (f) and (g) The average polarization of the equilibrium domain patterns in z-direction, i.e., <P3>, in the initial cylindrical domain region, for the two bending cases.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061556&req=5

f6: Control of domain stability by wavy bending.Control of domain stability by wavy bending on 128 nm × 128 nm × 8 nm simulation cells at room temperature. The cells are initially written with cylindrical domains with size r from 1 nm to 64 nm. (a) Schematics of a cell under wavy bending, i.e., , with λ = 128 nm. Distribution of (b) and (c) flexoelectric field as a function of Ab in the x-z plane of a cell under wavy bending. Phase diagrams of equilibrium domain pattern in cells under wavy bending with flexoelectric field (d) switched off and (e) on. (f) and (g) The average polarization of the equilibrium domain patterns in z-direction, i.e., <P3>, in the initial cylindrical domain region, for the two bending cases.
Mentions: The investigated mechanical loading conditions so far are with uniform strain or uniform strain gradient. It has been recently demonstrated that a wavy bending configuration of ferroelectric nanofilm can be achieved by integrating it on prestrained elastomeric supports, which is important for developing flexible ferroelectric devices1516 Considering the fact that the strain gradient of wavy bending is not uniform, an exploration on its effect is not trivial to the cases of uniform strain and uniform strain gradient. For a nanofilm with a wavy bending along x-direction (Figure 6a), its strain state can be approximately described by a cosine form strain, i.e., , where Ab is wave amplitude, characterizing the largest defection of the nanofilm from its neutral plane z = h/2, and λ is the wave length along the x-direction. Note that for simplicity we fix the neutral plane at middle plane of the film to only consider the case of zero membrane strain.

Bottom Line: It is found that the stability of a cylindrical domain depends on its radius, temperature and film thickness.Based on the calculated phase diagrams, we successfully simulate several mechanical erasing processes on 4 × 4 bits memory devices.Our study sheds light on prospective device applications of ferroelectrics involving mechanical loads, such as flexible memory devices and other micro-electromechanical systems.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China [2] Micro&Nano Physics and Mechanics Research Laboratory, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China.

ABSTRACT
Intensive investigations have been drawn on nanoscale ferroelectrics for their prospective applications such as developing memory devices. In contrast with the commonly used electrical means to process (i.e., read, write or erase) the information carried by ferroelectric domains, at present, mechanisms of non-electrical processing ferroelectric domains are relatively lacking. Here we make a systematical investigation on the stability of 180° cylindrical domains in ferroelectric nanofilms subjected to macroscopic mechanical loads, and explore the possibility of mechanical erasing. Effects of domain size, film thickness, temperature and different mechanical loads, including uniform strain, cylindrical bending and wavy bending, have been revealed. It is found that the stability of a cylindrical domain depends on its radius, temperature and film thickness. More importantly, mechanical loads have great controllability on the stability of cylindrical domains, with the critical radius nonlinearly sensitive to both strain and strain gradient. This indicates that erasing cylindrical domain can be achieved by changing the strain state of nanofilm. Based on the calculated phase diagrams, we successfully simulate several mechanical erasing processes on 4 × 4 bits memory devices. Our study sheds light on prospective device applications of ferroelectrics involving mechanical loads, such as flexible memory devices and other micro-electromechanical systems.

No MeSH data available.


Related in: MedlinePlus