Limits...
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 cylindrical bending.Control of domain stability by cylindrical 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 cylindrical bending, i.e., . Distribution of  as a function of εtop in the x-z plane of a cell under (b) pure bending (εtop = −εbot) and (c) mixed bending-strain (εtop ≠ 0, εbot = 0). Phase diagrams of equilibrium domain pattern in cells under (d) pure bending and (e) mixed bending strain conditions. (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
getmorefigures.php?uid=PMC4061556&req=5

f5: Control of domain stability by cylindrical bending.Control of domain stability by cylindrical 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 cylindrical bending, i.e., . Distribution of as a function of εtop in the x-z plane of a cell under (b) pure bending (εtop = −εbot) and (c) mixed bending-strain (εtop ≠ 0, εbot = 0). Phase diagrams of equilibrium domain pattern in cells under (d) pure bending and (e) mixed bending strain conditions. (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: For the cylindrical bending condition, we mean that the nanofilm is under an external bending strain in form of , where εtop and εbot are the magnitudes of at the top and bottom surfaces of the film, respectively, and coordinate z is measured with respect to the bottom surface of the film. This bending strain would cause a cylindrical-shape bending of the nanofilm along the x-direction as shown in Figure 5a. Typically, we consider two loading cases, i.e., the pure bending case with zero membrane strain, i.e., , and mixed bending-strain case with nonzero membrane strain, i.e., εtop ≠ 0 and εbot = 0. The distribution of as a function of εtop in the x-z plane of an 8 nm-thick nanofilm for the two loading cases is depicted in Figure 5b and 5c, respectively.


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 cylindrical bending.Control of domain stability by cylindrical 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 cylindrical bending, i.e., . Distribution of  as a function of εtop in the x-z plane of a cell under (b) pure bending (εtop = −εbot) and (c) mixed bending-strain (εtop ≠ 0, εbot = 0). Phase diagrams of equilibrium domain pattern in cells under (d) pure bending and (e) mixed bending strain conditions. (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

f5: Control of domain stability by cylindrical bending.Control of domain stability by cylindrical 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 cylindrical bending, i.e., . Distribution of as a function of εtop in the x-z plane of a cell under (b) pure bending (εtop = −εbot) and (c) mixed bending-strain (εtop ≠ 0, εbot = 0). Phase diagrams of equilibrium domain pattern in cells under (d) pure bending and (e) mixed bending strain conditions. (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: For the cylindrical bending condition, we mean that the nanofilm is under an external bending strain in form of , where εtop and εbot are the magnitudes of at the top and bottom surfaces of the film, respectively, and coordinate z is measured with respect to the bottom surface of the film. This bending strain would cause a cylindrical-shape bending of the nanofilm along the x-direction as shown in Figure 5a. Typically, we consider two loading cases, i.e., the pure bending case with zero membrane strain, i.e., , and mixed bending-strain case with nonzero membrane strain, i.e., εtop ≠ 0 and εbot = 0. The distribution of as a function of εtop in the x-z plane of an 8 nm-thick nanofilm for the two loading cases is depicted in Figure 5b and 5c, respectively.

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