JP3972096B2 - Nonvolatile optical memory, optical information storage method, and optical information read method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nonvolatile optical memory, an optical information storage method, and an optical information reading method.
[0002]
[Prior art]
Data recording is indispensable for today's advanced information society, and interest has shifted from the development of volatile DRAM (Dynamic Random Access Memory) to nonvolatile FRAM (Ferroelectric Random Access Memory) and MRAM (Magnetic Random Access Memory). Many companies have started development. In recent years, high-speed and high-density data processing has been required, and therefore, there is an increasing demand for recording predetermined optical information directly in a nonvolatile memory.
[0003]
In the 1960s, IBM succeeded in trial manufacture of an optical memory having a two-layer structure of an inorganic semiconductor / inorganic ferroelectric, but this optical memory has a problem that it cannot be electrically read. In addition, since an inorganic semiconductor is used as the light receiving layer, there is a problem that resistance during light irradiation is relatively small and sufficient efficiency cannot be obtained.
[0004]
The present invention provides a novel non-volatile memory that can directly capture and store optical information, and provide a method for directly storing the optical information and a method for reading the optical information. The purpose is to do.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a nonvolatile optical memory in which a semiconductor layer, a ferroelectric layer, and a photoconductor layer are sequentially laminated on a predetermined substrate.
[0006]
The present invention also provides:
An optical information storage method in the nonvolatile optical memory,
A step of detecting by irradiating a predetermined light information on the photo conductor layer,
By the optical information that has been propagated through the optical conductor layer, and a step of polarize the ferroelectric layer disposed below the photoconductor layer, for storing the optical information in the ferroelectric layer ,
It is related with the optical information storage method characterized by comprising.
[0007]
Furthermore, the present invention provides
Irradiating the photoconductor layer with predetermined optical information and detecting it;
Polarizing the ferroelectric layer provided below the photoconductor layer by the optical information propagated in the photoconductor layer, and storing the optical information in the ferroelectric layer;
Reading the optical information by measuring a resistance change due to an electric field effect with the ferroelectric layer in a semiconductor layer provided below the ferroelectric layer;
It is related with the optical information reading method characterized by comprising.
[0008]
According to the present invention, a non-volatile optical memory is configured by sequentially laminating a semiconductor layer, a ferroelectric layer, and a photoconductor layer on a predetermined substrate. A function as an optical information detection layer is added to the photoconductor layer to detect predetermined optical information. Further, a function as an optical information storage layer is added to the ferroelectric layer, polarization is caused in the ferroelectric layer by the optical information, and the optical information is stored as polarization information. Further, a function as an optical information readout layer is added to the semiconductor layer, and polarization information of the ferroelectric layer from a change in resistance of the semiconductor layer through an electric field effect between the semiconductor layer and the ferroelectric layer, that is, The stored optical information is read out.
[0009]
Thus, according to the present invention, optical information can be directly captured and stored in a memory, and the optical information can be electrically read from a change in resistance value of the semiconductor layer. Therefore, high-speed and high-density data processing can be performed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the invention.
FIG. 1 is a side view showing an example of the nonvolatile optical memory of the present invention, and FIG. 2 is a top plan view of the nonvolatile optical memory shown in FIG.
[0011]
In the nonvolatile optical memory 10 shown in FIGS. 1 and 2, a semiconductor layer 12, a ferroelectric layer 13, and a photoconductor layer 14 are sequentially stacked on a predetermined substrate 11. A source electrode 15 and a drain electrode 16 are formed on the semiconductor layer 12 so that the protruding central portion extends below the ferroelectric layer 13, and on the photoconductive layer 14. Is provided with a gate electrode 17. The ferroelectric layer 13 and the photoconductor layer 14 constitute a gate electrode part of the nonvolatile optical memory 10, and the semiconductor layer 12 constitutes a channel part of the nonvolatile optical memory 10.
[0012]
When the non-volatile optical memory 10 is irradiated with predetermined optical information as indicated by arrows in the figure, this optical information is detected by the photoconductor layer 14. Then, the optical information propagates through the photoconductor layer 14 and then reaches the ferroelectric layer 13 to cause polarization inside. As a result, the optical information is stored as polarization information in the ferroelectric layer 13.
[0013]
In the above memory operation, it is preferable to apply a bias voltage to the ferroelectric layer 13. The polarization state in the ferroelectric layer 13 changes depending on the magnitude and direction of the voltage and draws a hysteresis loop. Therefore, by applying the bias voltage, the absolute polarization magnitude in the ferroelectric layer 13 can be controlled, and the optical information can be stored more reliably.
[0014]
When polarization occurs in the ferroelectric layer 13, the resistance value of the semiconductor layer 12 changes due to the electric field effect caused by the polarization. Since the degree of change in the resistance value depends on the polarization state inside the ferroelectric layer 13, the polarization information inside the ferroelectric layer 13, that is, the optical information can be read out by measuring the resistance value change. become able to.
[0015]
In the nonvolatile optical memory 10 shown in FIGS. 1 and 2, the change in the resistance value is known by measuring the current value flowing between the source electrode 15 and the drain electrode 16 when a constant voltage is loaded on the gate electrode 17. Can do.
[0016]
The photoconductor layer 14 preferably contains an organic conductor, and particularly preferably contains at least one of copper phthalocyanine and an aluminum quinolyl complex. The thickness of the photoconductor layer 14 is preferably 300 nm to 1000 nm.
[0017]
The ferroelectric layer 13 preferably contains at least one of barium titanate, barium strontium titanate, lead titanate, and lead titanium zirconate. The thickness of the ferroelectric layer 13 is preferably 100 nm to 700 nm.
[0018]
Although the semiconductor layer 12 can be comprised from a well-known semiconductor, it is preferable that an oxide semiconductor is included preferably, and it is preferable that it contains lanthanum manganate especially. Further, the thickness of the semiconductor layer 12 is preferably 5 nm to 10 nm.
[0019]
The semiconductor layer 12, the ferroelectric layer 13, and the photoconductor layer 14 can be produced by using a known film formation method. The substrate 11 can be a general-purpose semiconductor substrate, and the source electrode 15, the drain electrode 16, and the gate electrode 17 can be made of a highly conductive metal such as gold, silver, or copper.
[0020]
【Example】
(Production of non-volatile optical memory)
_On a substrate made of SrTiO ₃ , a La _0.87 Ba _0.13 MnO ₃ layer as a semiconductor layer was formed to a thickness of 7 nm at a temperature of 730 ° C. by a laser deposition method using an ArF excimer laser (wavelength 193 nm). Next, gold electrodes as a source electrode and a drain electrode were formed on the La _0.87 Ba _0.13 MnO ₃ layer at room temperature by a vacuum deposition method using a predetermined mask.
[0021]
Next, by the same laser deposition method, a PbZr _0.2 Ti _0.8 O ₃ layer as a ferroelectric layer is projected and extended on the La _0.87 Ba _0.13 MnO ₃ layer so as to protrude from the source electrode and the drain electrode at a temperature of 620 ° C. It was formed to a thickness of 250 nm so as to cover the existing central part. Next, a copper phthalocyanine layer as a photoconductor layer was formed to a thickness of 600 nm on the PbZr _0.2 Ti _0.8 O ₃ layer at a temperature of 100 ° C. by a vacuum deposition method. Next, a gold electrode as a gate electrode was formed on the copper phthalocyanine layer by a vacuum deposition method, and a nonvolatile optical memory as shown in FIGS. 1 and 2 was produced.
[0022]
(Evaluation of non-volatile optical memory)
The nonvolatile optical memory manufactured as described above was irradiated with white light from which ultraviolet light with a wavelength of 380 nm or less was removed from a Xe lamp with a filter, and the operational characteristics of the nonvolatile optical memory were evaluated.
[0023]
FIG. 3 is a graph showing the relationship between the dielectric polarization P and the applied voltage Vb of the PbZr _0.2 Ti _0.8 O ₃ layer constituting the nonvolatile optical memory. As shown in FIG. 3, in a state where white light is irradiated, a hysteresis curve is generated such that a relatively large dielectric polarization value P is generated as the applied voltage increases or decreases. It can be seen that only the polarization value P is exhibited. Therefore, by irradiating the white light, polarization having an appropriate magnitude can be generated in the PbZr _0.2 Ti _0.8 O ₃ layer. As a result, it is understood that if predetermined information is superimposed on the white light, this light information can be stored in the PbZr _0.2 Ti _0.8 O ₃ layer as polarization information.
[0024]
At this time, if a bias voltage of a predetermined magnitude is applied to the PbZr _0.2 Ti _0.8 O ₃ layer, the dielectric polarization value P can be changed. Therefore, the optical information can be accurately used as polarization information. It can be memorized.
[0025]
FIG. 4 is a graph showing a change in resistance value of the La _0.87 Ba _0.13 MnO ₃ layer constituting the nonvolatile optical memory. As is clear from FIG. 4, in the state of irradiation with white light, the resistance value in the La _0.87 Ba _0.13 MnO ₃ layer varies with the gate voltage due to the electric field effect from the PbZr _0.2 Ti _0.8 O ₃ layer. However, in the state where the white light is not irradiated, the resistance value in the La _0.87 Ba _0.13 MnO ₃ layer hardly changes even when the gate voltage changes.
[0026]
FIG. 5 is a graph showing the change over time of the resistance value in the La _0.87 Ba _0.13 MnO ₃ layer when the recording operation of the nonvolatile optical memory is executed. This recording operation is performed by applying a bias voltage of −5 V to the PbZr _0.2 Ti _0.8 O ₃ layer. When the above-described white light is irradiated onto the nonvolatile optical memory (point a in the figure), a predetermined amount of polarization is generated in the PbZr _0.2 Ti _0.8 O ₃ layer, and thus the PbZr _0.2 Ti _0.8 Due to the electric field effect from the O ₃ layer, the resistance value of the La _0.87 Ba _0.13 MnO ₃ layer changes (decreases) from point a to point b in the figure.
[0027]
Thereafter, by removing the bias voltage, the resistance value of the La _0.87 Ba _0.13 MnO ₃ layer slightly changes (increases) from the point b to the point c in the figure, and thereafter exhibits a constant value. Thereafter, when the polarization in the PbZr _0.2 Ti _0.8 O ₃ layer is extinguished by applying a gate voltage of +5 V, the resistance value in the La _0.87 Ba _0.13 MnO ₃ layer changes from point d to point e in the figure. (Increased) to exhibit a resistance value equivalent to the resistance value at point a.
[0028]
Thus, when PbZr _0.2 Ti _0.8 O ₃ layer is polarized, the resistance value of the La _0.87 Ba _0.13 MnO ₃ layer during changes accordingly, by measuring the change in resistance, the PbZr _0.2 The polarization state of the Ti _0.8 O ₃ layer, that is, the polarization information can be read, and thereby the optical information converted into the polarization information can be read.
[0029]
FIG. 6 is a graph showing the change over time of the resistance value in the La _0.87 Ba _0.13 MnO ₃ layer when the recording operation shown in FIG. 5 is continuously performed a plurality of times. As is apparent from FIG. 6, even when the recording operation is performed a plurality of times, the La _0.87 Ba _0.13 MnO ₃ layer repeats the same resistance value change over time, and the reading operation can be sufficiently performed even in a plurality of recording operations. I understand.
As a result, the nonvolatile optical memory obtained in this example can directly capture and store optical information, and can electrically read the optical information from the resistance value change of the semiconductor layer. High-speed and high-density data processing can be performed.
[0030]
As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes can be made without departing from the scope of the present invention. It can be changed.
[0031]
【The invention's effect】
As described above, according to the present invention, a novel nonvolatile memory capable of directly capturing and storing and reading optical information is provided, and a method for directly storing the optical information and A method for reading the optical information can be provided.
[Brief description of the drawings]
FIG. 1 is a side view showing an example of a nonvolatile optical memory of the present invention.
2 is a top plan view of the nonvolatile optical memory shown in FIG. 1. FIG.
FIG. 3 is a graph showing the relationship between dielectric polarization P and applied voltage Vb of a PbZr _0.2 Ti _0.8 O ₃ layer constituting a nonvolatile optical memory.
FIG. 4 is a graph showing a change in resistance value of a La _0.87 Ba _0.13 MnO ₃ semiconductor layer constituting a nonvolatile optical memory.
FIG. 5 is a graph showing a change with time of a resistance value in a La _0.87 Ba _0.13 MnO ₃ semiconductor layer when a recording operation of a nonvolatile optical memory is executed.
6 is a graph showing a change with time of a resistance value in a La _0.87 Ba _0.13 MnO ₃ semiconductor layer when the recording operation shown in FIG. 5 is continuously performed a plurality of times. FIG.
[Explanation of symbols]
11 Substrate 12 Semiconductor layer 13 Ferroelectric layer 14 Photoconductor layer 15 Source electrode 16 Drain electrode 17 Gate electrode

Claims (21)

In a predetermined substrate, a semiconductor layer serving as an optical information reading layer, a ferroelectric layer which functions as an optical information storage layer, and a photoconductor layer serving as an optical information detection layer is forward-order products layer, wherein ferroelectric layer and the photoconductive layer constitutes a gate electrode portion, the semiconductor layer that make up the channel section nonvolatile optical memory. The nonvolatile optical memory according to claim 1 , wherein the photoconductor layer includes an organic conductor. The nonvolatile optical memory according to claim 2 , wherein the photoconductor layer includes at least one of copper phthalocyanine and an aluminum quinolyl complex. The nonvolatile layer according to any one of claims 1 to 3 , wherein the ferroelectric layer includes at least one of barium titanate, barium strontium titanate, lead titanate, and lead titanium zirconate. Sex memory. The semiconductor layer is characterized by comprising an oxide semiconductor, nonvolatile optical memory according to any one of claims 1-4. The nonvolatile optical memory according to claim 5 , wherein the semiconductor layer includes lanthanum barium manganate. Wherein the thickness of the photoconductive layer is 300 nm to 1000 nm, nonvolatile optical memory according to any one of claims 1-6. Wherein the thickness of the ferroelectric layer is 100Nm～700nm, nonvolatile optical memory according to any one of claims 1-7. Wherein the thickness of the semiconductor layer is 5 nm to 10 nm, nonvolatile optical memory according to any one of claims 1-8. An optical information storage method in the nonvolatile optical memory according to claim 1,
A step of detecting by irradiating a predetermined light information on the photo conductor layer,
By the optical information that has been propagated through the optical conductor layer, and a step of polarize the ferroelectric layer disposed below the photoconductor layer, for storing the optical information in the ferroelectric layer ,
An optical information storage method comprising the steps of: 11. The optical information storage method according to claim 10 , wherein polarization of the ferroelectric layer by the optical information is performed in a state where a predetermined bias voltage is applied to the ferroelectric layer. Irradiating the photoconductor layer with predetermined optical information and detecting it;
Polarizing the ferroelectric layer provided below the photoconductor layer by the optical information propagated in the photoconductor layer, and storing the optical information in the ferroelectric layer;
Reading the optical information by measuring a resistance change due to an electric field effect with the ferroelectric layer in a semiconductor layer provided below the ferroelectric layer;
An optical information reading method comprising the steps of: 13. The optical information reading method according to claim 12 , wherein the polarization of the ferroelectric layer by the optical information is performed in a state where a predetermined bias voltage is applied to the ferroelectric layer. The photoconductive layer is characterized by containing an organic conductor, an optical information reading method according to claim 12 or 13. The optical information reading method according to claim 14 , wherein the photoconductor layer includes at least one of copper phthalocyanine and an aluminum quinolyl complex. The light according to any one of claims 12 to 15 , wherein the ferroelectric layer includes at least one of barium titanate, barium strontium titanate, lead titanate, and lead titanium zirconate. Information reading method. The semiconductor layer is characterized by comprising an oxide semiconductor, the optical information reading method according to any one of claims 12 to 16. The optical information reading method according to claim 17 , wherein the semiconductor layer contains lanthanum manganate. The optical information reading method according to any one of claims 12 to 18 , wherein the photoconductor layer has a thickness of 300 nm to 1000 nm. Wherein the thickness of the ferroelectric layer is 100Nm～700nm, optical information reading method according to any one of claims 12-19. Wherein the thickness of the semiconductor layer is 5 nm to 10 nm, the optical information reading method according to any one of claims 12-20.

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