CN103325410A - Method for reading polarization storage state of ferroelectric memory by light - Google Patents
Method for reading polarization storage state of ferroelectric memory by light Download PDFInfo
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- CN103325410A CN103325410A CN2013102455488A CN201310245548A CN103325410A CN 103325410 A CN103325410 A CN 103325410A CN 2013102455488 A CN2013102455488 A CN 2013102455488A CN 201310245548 A CN201310245548 A CN 201310245548A CN 103325410 A CN103325410 A CN 103325410A
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Abstract
The invention discloses a method for reading a storage state of a ferroelectric memory. The method comprises the following steps of: selecting a light source with wave length corresponding to a forbidden bandwidth of a ferroelectric memory unit material; reading electric current by the light source under optical power density of 5-500 micro w/cm<2>, and determining the direction of the electric current; and determining the polarized state of the ferroelectric memory based on that the polarization direction is opposite to the direction of the read electric current. The method provided by the invention can be used for reading the ferroelectric polarization direction according to the direction of the electric current generated by irradiation of light with the wavelength of 200nm to 950nm to the ferroelectric storing unit, adopts a non-voltage non-destructive reading manner, can be used for manufacturing a novel non-volatilisation ferroelectric memory with higher reading speed, smaller size, lower energy consumption and higher reliability, and is particularly suitable for production of memories with a requirement on frequent reading operation.
Description
Technical field
The invention belongs to the microelectronics area information storage, relate to a kind of method of utilizing light to read the iron electric polarization state.
Background technology
The storage unit of traditional ferroelectric memory mainly is made of electric capacity and field effect transistor, is one deck ferroelectric crystal film in the middle of two battery lead plates of this electric capacity.It is to utilize the both direction of iron electric polarization to represent binary data, and the speed of polarization reversal is very fast.It is not by the electric charge on the electric capacity that ferroelectric memory is preserved data, but carry out record by the central atom position of ferroelectric crystal in the memory cell capacitor, and the direct position of central atom is detected is irrealizable, actual read operation process is: apply a known electric field (namely to the electric capacity charging) at memory cell capacitor, if originally the position of the central atom of crystal is identical with the position that the direction of an electric field that applies will reach central atom, then central atom can not move; If it is opposite, then central atom will be crossed the arrival another location, high energy rank in crystal middle layer, a spike then will appear on charge waveforms, produce namely that atom moves than not producing the mobile spike that manyed, the charge waveforms of the same reference bit of this charge waveforms (determine and known) is compared, can judge that just the content in the storage unit of detection is " 1 " or " 0 ".Must be higher than coercive voltage owing to read the voltage of polarization charge, be that destructiveness is read, and needs corresponding restoring circuit.
On the ferroelectrics of light irradiation with specific wavelength corresponding with energy gap after the polarization, ferroelectrics absorbs photon and produces charge carrier, and charge carrier is mobile under the driving of the reverse built in field that polarization causes, produces the steady-state short-circuit photogenerated current.
Light reads the method for iron electric polarization state, has broken away from the dependence to voltage, is that non-destructive is read, and is particularly useful for making the storer that read operation is very frequently carried out in requirement, has more wide application space.
Summary of the invention
The purpose of this invention is to provide the method that a kind of light reads the iron electric polarization state.
The principle of method provided by the invention is as shown in Figure 1: when the illumination of certain wavelength is mapped to ferroelectric storage cell, can produce electric current, with galvanometer probe current signal, can judge the iron electric polarization direction by direction of current, thereby determine the iron electric polarization store status.
The technical scheme that realizes the object of the invention is: a kind of light reads the method for iron electric polarization state, may further comprise the steps:
(1) choosing of light source: choose corresponding optical source wavelength according to the energy gap of ferroelectric storage cell material;
(2) reading of electric current: adopt above-mentioned light source at 5-500 μ W/cm
2Read electric current under the optical power density, determine direction of current;
(3) conversion of iron electric polarization state: polarised direction and the current opposite in direction that reads, thus determine its polarized state.
Optical source wavelength described in the step (1) is determined by following formula:
E
g=hc/λ
max，
E wherein
gBe the band gap width of ferroelectric material, h is Planck constant: 6.63 * 10
-34Js, c=3.0 * 10
8M/s is the aerial speed of light, λ
MaxMaximum wavelength for selected light source.
The preferred 200-950nm of optical source wavelength described in the step (1).
The present invention successfully utilizes light to read the iron electric polarization state, this kind read method, can realize reading of polarised direction by the identification direction of current, be that non-voltage-type non-destructive is read, do not need restoring circuit, can cut down the consumption of energy, and keep the high density characteristic of resistive memory and the high speed reads write attribute of ferroelectric storage.It can be used for making the novel nonvolatile memory that read or write speed is faster, volume is littler, energy consumption is lower, reliability is stronger, has great application potential.
Description of drawings
Fig. 1 reads the schematic diagram of iron electric polarization direction for light.
Fig. 2 is the thick Pb (Zr of tin-doped indium oxide (ITO) top electrode/120nm for structure
0.52Ti
0.48) O
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode, illumination when polarization makes progress, measured electric current.
Fig. 3 is the thick Pb (Zr of ITO top electrode/120nm for structure
0.2Ti
0.8) O
3/ Nb-SrTiO
3The ferroelectric storage cell of bottom electrode, illumination when polarization makes progress, measured electric current.
Fig. 4 is the thick SrBi of ITO top electrode/120nm for structure
2Ta
2O
9Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode, illumination when polarization makes progress, measured electric current.
Fig. 5 is the thick BiFeO of ITO top electrode/120nm for structure
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode, illumination when polarization is downward, measured electric current.
Fig. 6 is the thick doping 5%(molar percentage of ITO top electrode/120nm for structure) Ag
2The BaTiO of O
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode, illumination when polarization is downward, measured electric current.
Embodiment
Example 1:
Choosing structure is the thick Pb (Zr of ITO top electrode/120nm
0.52Ti
0.48) O
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode polarizes ferroelectric storage cell with voltage source in advance, determines that its polarised direction makes progress, and implements the method that light provided by the invention reads polarized state:
(1) choosing of light source: Pb (Zr
0.52Ti
0.48) O
3Energy gap be 3.5eV, according to formula: E
g=hc/ λ
Max, can choose the light source that wavelength is not more than 354nm, so locate to choose the light source of wavelength 200nm.
(2) read electric current: the light source of 200nm and optical power density 5 μ W/cm
2Under read electric current, the electric current that reads is illustrated in figure 2 as downwards.
(3) checking of iron electric polarization state: the direction of current that reads is opposite with the polarised direction of ferroelectric storage cell to be that polarised direction makes progress, and the polarised direction of determining with voltage source is consistent.
Example 2:
Choosing structure is the thick Pb (Zr of ITO top electrode/120nm
0.52Ti
0.48) O
3/ Nb-SrTiO
3The ferroelectric storage cell of bottom electrode polarizes ferroelectric storage cell with voltage source in advance, determines that its polarised direction makes progress, and implements the method that light provided by the invention reads polarized state:
(1) choosing of light source: Pb (Zr
0.52Ti
0.48) O
3Energy gap be 3.5eV, according to formula: E
g=hc/ λ
Max, can choose the light source that wavelength is not more than 354nm, so locate to choose the light source of wavelength 350nm.
(2) read electric current: the light source of 350nm and optical power density 50 μ W/cm
2Under read electric current, the electric current that reads is illustrated in figure 3 as downwards.
(3) checking of iron electric polarization state: the direction of current that reads is opposite with the polarised direction of ferroelectric storage cell, and the polarised direction of determining with voltage source is consistent.
Example 3:
Choosing structure is the thick SrBi of ITO top electrode/120nm
2Ta
2O
9Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode polarizes ferroelectric storage cell with voltage source in advance, determines that its polarised direction makes progress, and implements the method that light provided by the invention reads polarized state:
(1) choosing of light source: SrBi
2Ta
2O
9Energy gap be 3.25eV, according to formula: E
g=hc/ λ
Max, can choose the light source that wavelength is not more than 381nm, so choose the light source that wavelength is 380nm.
(2) read electric current; The light source of 380nm and optical power density 200 μ W/cm
2Under read electric current, the electric current that reads is illustrated in figure 4 as downwards.
(3) checking of iron electric polarization state: the direction of current that reads is opposite with the polarised direction of ferroelectric storage cell, and the polarised direction of determining with voltage source is consistent.
Example 4:
Choosing structure is the thick BiFeO of ITO top electrode/120nm
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode polarizes ferroelectric storage cell with voltage source in advance, determines that its polarised direction is downward, implements the method that light provided by the invention reads polarized state:
(1) choosing of light source: BiFeO
3Energy gap be 2.7eV, according to formula: E
g=hc/ λ
Max, can choose the light source that wavelength is not more than 459nm, so choose the light source that wavelength is 458nm.
(2) read electric current: the light source of 458nm and optical power density 300 μ W/cm
2Under read electric current, the current value that reads is illustrated in figure 5 as upwards.
(3) checking of iron electric polarization state: the direction of current that reads is opposite with the polarised direction of ferroelectric storage cell, and the polarised direction of determining with voltage source is consistent.
Example 5:
Choosing structure is the thick doping molar percentage 5%Ag of ITO top electrode/120nm
2The BaTiO of O
3Film/Nb-SrTiO
3The ferroelectric storage cell of bottom electrode polarizes ferroelectric storage cell with voltage source in advance, determines that its polarised direction is downward, implements the method that light provided by the invention reads polarized state:
(1) choosing of light source: Ag
2The energy gap of O is 1.3eV, according to formula: E
g=hc/ λ
Max, can choose the light source that wavelength is not more than 954nm, so choose the light source that wavelength is 950nm.
(2) read electric current: the light source of 950nm and optical power density 500 μ W/cm
2Under read electric current, the current value that reads is illustrated in figure 6 as upwards.
(3) checking of iron electric polarization state: the direction of current that reads is opposite with the polarised direction of ferroelectric storage cell, and the polarised direction of determining with voltage source is consistent.
Read polarised direction by above-described embodiment identification direction of current.Since polarised direction up and down respectively the content in the representative memory cell be " 1 " or " 0 ", therefore the method for invention just can be judged content in the storage unit of detection thus, is that non-voltage-type non-destructive is read.
Claims (3)
1. a light reads the method for iron electric polarization state, it is characterized in that may further comprise the steps:
(1) choosing of light source: choose corresponding optical source wavelength according to the energy gap of ferroelectric storage cell material;
(2) reading of electric current: adopt above-mentioned light source at 5-500 μ W/cm
2Read electric current under the optical power density, determine direction of current;
(3) conversion of iron electric polarization state: polarised direction and the current opposite in direction that reads, thus determine its polarized state.
2. light according to claim 1 reads the method for iron electric polarization state, it is characterized in that the optical source wavelength described in the step (1) is by formula E
g=hc/ λ
MaxDetermine, wherein E
gBe the band gap width of ferroelectric material, h is Planck constant, and c is the aerial speed of light, λ
MaxMaximum wavelength for selected light source.
3. light according to claim 1 reads the method for iron electric polarization state, it is characterized in that the optical source wavelength described in the step (1) is 200-950nm.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109037218A (en) * | 2018-06-13 | 2018-12-18 | 湘潭大学 | Light erasing and the ferroelectric tunnel junction storage unit and its erasing and read method read |
| CN112309440A (en) * | 2020-10-21 | 2021-02-02 | 西北工业大学 | Optical storage device based on platinum-two-dimensional indium selenide-few-layer graphite Schottky diode and storage method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6617629B1 (en) * | 2002-06-26 | 2003-09-09 | The United States Of America As Represented By The Secretary Of The Navy | Optically readable ferroelectric memory cell |
| CN102122105A (en) * | 2011-03-15 | 2011-07-13 | 中国科学院半导体研究所 | Polarization method for ferroelectric crystal material |
-
2013
- 2013-06-19 CN CN2013102455488A patent/CN103325410A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6617629B1 (en) * | 2002-06-26 | 2003-09-09 | The United States Of America As Represented By The Secretary Of The Navy | Optically readable ferroelectric memory cell |
| CN102122105A (en) * | 2011-03-15 | 2011-07-13 | 中国科学院半导体研究所 | Polarization method for ferroelectric crystal material |
Non-Patent Citations (1)
| Title |
|---|
| RUI GUO等: "Non-volatile memory based on the ferroelectric photovoltaic effect", 《NATURE COMMUNICATIONS》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109037218A (en) * | 2018-06-13 | 2018-12-18 | 湘潭大学 | Light erasing and the ferroelectric tunnel junction storage unit and its erasing and read method read |
| CN109037218B (en) * | 2018-06-13 | 2020-07-17 | 湘潭大学 | Optically erased and read ferroelectric tunnel junction memory cell and erasing and reading method thereof |
| CN112309440A (en) * | 2020-10-21 | 2021-02-02 | 西北工业大学 | Optical storage device based on platinum-two-dimensional indium selenide-few-layer graphite Schottky diode and storage method |
| CN112309440B (en) * | 2020-10-21 | 2022-04-26 | 西北工业大学 | Optical storage device based on platinum-two-dimensional indium selenide-few-layer graphite Schottky diode and storage method |
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Application publication date: 20130925 |