JPH07320310A - Recording medium, information processor and information recording/reproducing method - Google Patents

Abstract

PURPOSE:To obtain a recording medium excellent in mechanical strength by interposing an adhesion layer containing molecules of specified composition between an electrode layer and a recording layer. CONSTITUTION:The recording medium comprises an electrode layer 102, an adhesion layer 105, and a recording layer 103 formed sequentially on a substrate 101. The adhesion layer 105 is interposed between the electrode layer 102 and the recording layer 103 and has a composition of thiol group and a molecule having a siloxane bond. The thioi group, being adsorbed selectively by a base metal, is adsorbed chemically onto the electrode layer 102 to form a strong bond. When the recording layer 103 is formed thereon, the siloxane bond part located at the end of a molecule not pertaining to the adsorption is bonded to the recording layer 103 thus strengthening the bond between the adhesion layer 105 and the recording layer 103. Since a sufficiently high adhesion is achieved between the electrode layer 102 of base metal and the recording layer 103 of organic film, mechanical strength of recording medium can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium for recording and / or reproducing information and a recording and / or reproducing apparatus using the recording medium.

[0002]

2. Description of the Related Art In recent years, with the development of the information-oriented society, the development of large-capacity memory has been extremely actively carried out. The performance required for memory is generally 1) high density and large recording capacity 2) high recording / reproducing response speed 3) low power consumption 4) high productivity and low price, etc. The development of a memory system and a memory medium that achieves excellent performance is extremely active.

Conventionally, the center of the memory has been a magnetic substance, a magnetic memory using a semiconductor as a material, and a semiconductor memory, but in recent years, with the progress of laser technology, inexpensive using organic thin films such as organic dyes and photopolymers. And high-density optical memory has appeared.

At present, technological development is underway toward miniaturization of unit memory bits in order to further increase the density and the capacity of these memories, but the principle is completely different from those of the conventional memories. A memory-based proposal has also been made. For example, the concept of a molecular electronic device in which each organic molecule has a function of a logic element or a memory element is one of them. It can be seen that molecular electronic devices have advanced the miniaturization of unit memory bits to the limit, but until now, how to access individual molecules has been a problem.

On the other hand, recently, a scanning tunneling microscope (S
TM) was developed (G. Binninig et al., Phys. Rev.
Lett., 49 , 57 (1982)), high resolution measurement in real space is possible regardless of single crystal or amorphous. The STM utilizes the fact that a tunnel current flows when a voltage is applied between a metal probe (probe electrode) and a conductive substance to bring them closer to a distance of about 10Å. This current is very sensitive to changes in the distance between the two, and by scanning the probe so as to keep the tunnel current constant, the surface structure in real space can be drawn, and at the same time, the total electron cloud of surface atoms can be drawn. Various information about can also be read. The resolution in the in-plane direction at this time is about 1Å. Therefore, if the principle of STM is applied, high density recording / reproducing can be sufficiently performed in atomic order (several Å). As a recording / reproducing method at this time, recording is performed by changing an appropriate surface state of the recording layer by using high-energy electromagnetic waves such as particle beam (electron beam, ion beam) or X-ray and energy rays such as visible / ultraviolet light. Do ST
A method of reproducing by M, a method of recording and reproducing by using STM using a thin film layer of a material having a memory effect on the switching characteristics of voltage and current as a recording layer, for example, a π-electron organic compound or chalcogenide is proposed. Has been done.
In addition, there has been proposed a method and apparatus for capturing molecules on a substrate from a fluid by applying a voltage pulse, selectively writing a data bit, and reading and erasing the data bit (JP-A-1-196751). ).

[0006]

Since the information processing apparatus for recording or reproducing as described above applies the STM principle, a material that does not form an oxide film, that is, a noble metal is used for the electrode layer of the recording medium. It is desirable to use. on the other hand,
For the recording layer, as disclosed in JP-A-63-161552, it is desirable to use a material having a memory switching phenomenon (electric memory effect) in current-voltage characteristics, but most of them are organic materials. Is. Some organic materials do not have very good adhesion to precious metals, and recording media are no exception. For example, as a report that describes the strength of a thin film used for a recording medium on a substrate, a report by E. Mayer et al.
Mayer et al., Nature, 349 , 398-400 (1991)). In these, an organic film is formed on a Si substrate, and its surface is subjected to an experiment by applying a load using an atomic force microscope (AFM). However, damage occurs with a relatively strong load. It has been suggested.

Further, in order to remove the component due to the unevenness of the medium surface from the reproduced signal and to prevent the interval control at the time of recording from being influenced by the applied voltage, the distance between the medium surface and the probe electrode other than the current flowing through them is used. A method of controlling the distance to a constant value is conceivable. One of them is the atomic force microscope (AF) which controls the distance by the atomic force acting between the two.
The use of M) is disclosed in Japanese Patent Application Laid-Open No. 1-245445. In the AFM, the probe electrode is supported by an elastic body, the force acting between the tip of the probe electrode and the surface of the recording medium is balanced with the spring force due to the deformation of the elastic body, and feedback control is performed so as to keep this deformation amount constant. Be done.

Even when such feedback control is performed, if the adhesion between the electrode layer and the recording layer is insufficient, the problem that the recording layer becomes weak to the physical external force first occurs.
For example, when the probe electrode comes into strong contact with the recording layer for some reason such as an external shock during recording / reproduction of information, the probe electrode may easily peel off the recording layer.

[0009]

Therefore, the present invention is based on the first aspect of the present invention.
In a recording medium in which at least an electrode layer and a recording layer are laminated, the electrode layer and the recording layer are laminated via an adhesion layer containing a molecule having a thiol group and a siloxane bond. A recording medium is provided.
In this way, by forming an adhesion layer composed of molecules having a thiol group and a siloxane bond between the electrode layer and the recording layer, the adhesion between the electrode layer and the recording layer is improved, and external shock or load is applied to the probe electrode. It is possible to avoid the risk that the surface of the recording medium will be destroyed by the probe electrode when the pressure is applied. An outline of the layer structure of such a recording medium is shown in FIG.

Secondly, the present invention relates to the above-mentioned recording medium, means for applying a voltage between the recording medium and a probe electrode arranged facing the recording medium, and a current flowing between the recording medium and the probe electrode. There is provided an information processing device having a current detection means for detecting a distance, a distance setting means for setting a distance between the recording medium and the probe electrode, and a distance holding means for holding the set distance constant during scanning of the probe electrode. .

Thirdly, the present invention uses the above-described information processing apparatus, wherein the distance between the recording medium and the probe electrode is set to a distance at which a tunnel current can flow by the distance setting means, and the distance is held by the distance holding means. An information reproducing method for reproducing information by detecting a tunnel current flowing between the recording medium and the probe electrode and detecting an electric characteristic of the recording medium, and a device between the recording medium and the probe electrode. There is provided an information recording method for recording by applying a voltage to the recording medium to change the electric characteristics of the recording medium.

The adhesion layer used in the recording medium of the present invention is
A compound having a thiol group and a siloxane bond is preferable, and as the compound, a compound having a thiol group at one molecular end and a siloxane bond at the other molecular end is particularly preferable.

As a simple method for forming such an adhesive layer,
By exposing the electrode layer to saturated vapor of the above compound or by dissolving the compound in a solvent such as an organic solvent and then immersing the electrode layer in the solution, the molecules of the compound are chemically adsorbed on the surface of the electrode layer. There is a way to do it.

Thiol groups have the property of being selectively chemisorbed by precious metals, especially gold (WSV Kwan et al.,
Langmuir, 1419-25 (1991)), thiol groups are selectively chemisorbed on the electrode layer, and a strong bond is formed with the electrode layer.

When the recording layer is formed on the adhesion layer, the siloxane bond portion at the molecular end that does not participate in adsorption to the electrode layer forms a bond with the recording layer. Further, the siloxane bond may have a network structure on the adhesion layer, and the bond between the adhesion layer and the recording layer becomes strong.

By thus forming the above-mentioned adhesion layer between the electrode layer and the recording layer, a recording medium having excellent mechanical strength can be obtained.

On the other hand, the recording layer in the recording medium of the present invention uses a material having a memory switching phenomenon (electric memory effect) in current-voltage characteristics, as disclosed in JP-A-63-161552. However, in view of the strength of the recording layer itself, it is preferable to use a monomolecular film of polyimide or a monomolecular cumulative film in consideration of the strength of the recording layer itself.

Further, from the viewpoint of thinning, it is preferable to form the polyimide monomolecular film or monomolecular cumulative film from the polyamic acid monomolecular film or monomolecular cumulative film obtained by the Langmuir-Blodgett (LB) method. As a method thereof, for example, first, long-chain alkylamines for imparting an appropriate hydrophobicity to polyamic acid are mixed, a polyamic acid amine salt is formed into a film, and then a chemical treatment or heating and calcination is performed to perform dehydration ring closure. (Imidization) reaction and deamine are performed to form a polyimide film.

The polyamic acid used in the present invention is obtained by condensing a carboxylic acid anhydride and a diamine. Examples of the carboxylic acid anhydride include pyromellitic acid anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid anhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid anhydride, 2, Examples thereof include 2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane acid anhydride.

As the diamine, phenylenediamine,
4,4′-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, 4,4 ″ -diamino-p-terphenyl, 4,4′-diaminodiphenylthioether, 4,4′-diaminodiphenyl Sulfone, α- (4-aminophenyl) -p-toluidine,
2,2-bis (4-aminophenyl) -1,1,1,
Examples include 3,3,3-hexafluoropropane and 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane.

Further, such a polyamic acid can be used in the recording medium of the present invention even if the unit having an amic acid structure is partially contained in the polymer main chain.
It is also possible to utilize a copolymer polyamic acid using one or more carboxylic anhydrides and / or two or more diamines.

In the present invention, the above long-chain alkylamines are primary to tertiary alkylamines, those in which a part of the alkyl group is halogen-substituted, and those in which a part of the alkyl chain is substituted with a hydroxyl group. It is possible to use those having a cyclic structure such as a branched alkyl group and a benzene ring.

The mixing ratio of these molecules is preferably such that all of the carboxyl groups of the polyamic acid are amine salified. That is, there are usually two carboxyl groups per repeating unit of polyamic acid. In this case, the total number of repeating units of polyamic acid: the number of molecules of alkylamine is 1: 1 to 1: 3, more preferably 1: 2
~ 1: 2.5.

As the solvent at this time, any solvent such as N, N-dimethylacetamide (DMAC), in which polyamic acid and amine are sufficiently dissolved and which can develop the solution on the water surface, is used. May be used, or a mixed solvent may be used.

The concentration of the polyamic acid is not particularly limited, but in terms of developability, the monomer-converted concentration is 1 × 10 ⁻⁷ to
It is preferably in the range of 1 × 10 ⁻³ M.

The solution of the polyamic acid amine salt prepared as described above is gently spread on the water surface. At this time, pure water at 20 to 25 ° C. is generally used as the aqueous phase, but the pH may be adjusted by adding various metal ions or adding acid or alkali.

Next, the polyamic acid amine salt developed on the water surface is compressed to form a monomolecular film of the polyamic acid amine salt on the water surface.

By immersing such a monomolecular film in a direction across the monolayer on the surface of the water while keeping the surface pressure constant and then pulling it up, two layers of Y-type molecular film can be accumulated on the support. It will be possible.

In order to copy a monomolecular film of a polyamic acid amine salt on a substrate, in addition to the above-mentioned vertical dipping method, a horizontal adhesion method,
It is also possible to use a method such as a rotating cylinder method.

The monomolecular accumulating film of the polyamic acid amine salt formed by such a method is imidized to obtain a polyimide monomolecular accumulating film, which is used as the recording layer in the recording medium of the present invention. As the imidization method, there are a chemical method and a thermal method, but any method may be used without any limitation.

The MIM structure element (FIG. 10) in which the above monomolecular accumulated film is sandwiched between two metal electrodes exhibits current-voltage characteristics as shown in FIG. 11 and FIG.
-96695). Two states (ON state and O
The FF state) transits to each other by applying a voltage equal to or higher than the threshold value, and each state is held at the threshold voltage or lower.
These characteristics are exhibited in a film having a film thickness of several Å to several thousand Å.
-161552 and JP-A-63-161553.
As disclosed in Japanese Patent Publication, preferably a few Å to 500
The film thickness is in the range of Å, most preferably 10 Å to 200 Å.

The electrode layer in the recording medium of the present invention may be one having a high electrical conductivity, but in order to improve the smoothness of the recording medium surface, a metal is epitaxially grown on a smooth substrate. preferable. It is desirable that such a smooth substrate has a smooth surface in which the difference between the maximum value and the minimum value of the surface unevenness is 1 nm or less in a region wider than a square having at least one side of 1 μm, and such a smooth substrate has a metal epitaxially grown. Those that are suitable for are desirable. As a smooth substrate that satisfies these conditions,
Examples include mica, MgO, TiC, Si and graphite.

Next, the electrode layer is preferably formed by epitaxially growing a metal on a smooth substrate. Examples of such metals include Au, Ag, Pd, and Au-A.
Alloys such as g and Au-Pd may be used.

Further, it is possible to form a track pattern on such an electrode layer, and various conventionally known lithography techniques can be used for forming such a track pattern, but the process is simplified and steps are formed. Of the focused ion beam (F
It is preferred to use ion beam techniques such as IB).
Further, in order to distinguish irregularities of recorded data and prevent damage to the probe electrode during data tracking, it is preferable that the track step be 3 nm to 30 nm.

In the information processing apparatus of the present invention, the above-mentioned recording medium of the present invention is incorporated in an apparatus for recording and / or reproducing information via the probe electrodes arranged opposite to each other, and the gap between the probe electrode and the recording medium is set. Information is recorded by applying a voltage between the probe electrode and the recording medium while keeping the gap constant so that the force in the direction for correcting the fluctuation acts on the probe electrode and the recording medium, or The reproduction is performed by detecting the current between the probe electrode and the recording medium.

As means for controlling the distance between the probe electrode and the recording medium, the force in the direction of detecting the interatomic force between the tip of the probe electrode and the surface of the recording medium and performing the above-mentioned fluctuation correction based on the detected value. Means for applying between the probe electrode and the recording medium, or an elastic support that supports the probe electrode and bends according to the repulsive force between the probe electrode tip and the recording medium surface.

Examples of the latter elastic support include those having a probe electrode provided at the center of the both-end supported beam or on the free end side of the cantilever. The material of the beam is A
It is preferable to use a foil of u, Ni, SUS or the like, and for making a fine beam, a SiO ₂ thin film often used in micromechanics can be used.

Since the force acting between the probe electrode and the recording medium is very small, it is preferable to make the mass of the probe electrode and the elastic support as small as possible, and the elastic support is soft to increase the change. In addition, it is preferable that it is strong against external vibration.

In the present invention, the probe electrode is scanned on the surface of the recording medium with the distance between the probe electrode and the recording medium being close to each other until a force such as a repulsive force acts between them, and between the two. A desired voltage is applied by a voltage application circuit to perform recording, reproduction and erasing.

Therefore, the tip of the probe electrode is recorded,
It is desirable to make it as sharp as possible in order to improve the resolution of reproduction and deletion. For example, a probe electrode obtained by implanting Si on a SiO ₂ substrate with a focused ion beam, selectively crystallizing Si on the Si, vapor-depositing Au, and performing a conductive treatment can be used. The shape and processing method are not limited to this.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

Example 1 A recording medium was manufactured in the order shown in FIG.

First, a mica plate was cleaved in the atmosphere to prepare a smooth substrate 101 (FIG. 2 (a)).

Next, Au was vapor-deposited on the smooth substrate 101 by a vacuum vapor deposition method to form an electrode layer 102 (FIG. 2).
(B)). The vapor deposition is performed at a substrate temperature of 400 ° C. and a film formation rate of 0.5 n
m / sec, ultimate vacuum 5 × 10 ⁻⁷ Torr, film thickness 50
It was performed under the condition of 0 nm.

Then, with the focused ion beam, the width of 0.
Track 10 with 1 μm, pitch 1.0 μm and depth 5 nm
4 was formed on the smooth electrode layer 102 (FIG. 2C). Au ⁺ ions are used as the focused ion beam, and the acceleration voltage is 40 k.
V, ion current 14 pA, dose 1 × 10 ¹⁶ / cm ²
It was performed under the conditions of.

Next, the smooth electrode substrate formed by the above method was exposed to the vapor of 3-mercaptopropyltrimethoxysilane for about 12 hours to form the adhesion layer 105 (FIG. 2).
(D)).

Thereafter, the polyamic acid represented by the following formula (1) was dissolved in dimethylacetamide (DMAC) (concentration of monomer conversion: 1 × 10 ⁻³ M), and separately prepared 1 × 1.
0 ^-3 M of N, the N- dimethyl octadecylamine DMA
The polyamic acid amine salt solution was prepared by mixing the C solution with 1: 2 (v / v).

[0048]

[Chemical 1] The solution is spread on a water phase composed of pure water at a water temperature of 20 ° C.,
A monomolecular film was formed on the water surface. After increasing the surface pressure to 25 mN / m and keeping the surface pressure constant, the substrate was gently immersed in a direction across the water surface at a speed of 5 mm / min.
Then, the film was gently pulled up at 5 mm / min to prepare a two-layer Y-type monomolecular cumulative film. Repeating this operation, 6
A monomolecular cumulative film of the polyamic acid amine salt of the layer was formed.

Subsequently, the substrate is heated and baked at 300 ° C. for 10 minutes to form a polyimide film, and the recording layer 1 in the present invention is obtained.
03 (Fig. 2 (e)). The thickness of the polyimide film was determined to be 4Å per layer by the ellipsometry method.

The recording medium prepared as described above is shown in FIG.
Information was recorded, reproduced, and erased using the information processing device shown in FIG.

The recording / reproducing method will be described below. The probe electrode 2 was scanned with respect to the track pattern on the recording medium. FIG. 13 is a plan view of a part of the recording medium used.

At this time, a bias voltage of -0.5 V is applied to the probe electrode (Pt-Rh alloy) 2 with respect to the smoothing electrode substrate 101 of FIG. 3, and the driver 305 and the driver 305 are controlled so that the tunnel current becomes 0.1 nA. The actuator 204 is used as a space holding means to use the probe electrode 2 and the electrode layer 10.
The position of the track 104 in FIG. 13 is detected by scanning while keeping the distance (Z direction in the drawing) to 2 constant, and based on the detected position of the track 104, a scanning pattern such as 501 is followed. A change in tunnel current between the probe electrode 2 and the track 104 was detected.

Recording is performed for 10 nm from a part of the scanning pattern, that is, a position of 50 nm from the step of the track 104.
It was done on the pitch. Recording was performed using the electric memory effect of the recording layer 103. That is, the triangular wave pulse voltage having the waveform shown in FIG.
Was applied to the recording layer 103 to generate a low resistance state in the applied portion. At this time, the tunnel current became 2 nA.
In addition, in FIG. 6, the probe electrode 2 is positive (+).
The pole and electrode 10 are negative (-) poles. After recording,
Information was reproduced again according to the first scanning pattern 501. The reproduction bias voltage is 0.5 V so that new information is not recorded or recorded information is not erased.
Then, the change in tunnel current was measured and the information was reproduced.

In the above reproduction experiment, the bit error rate is 1 × 1 when the data transfer rate is 1 Mbps.
0 was ^-5. Subsequently, when the pulse voltage shown in FIG. 7 was applied to the information recording portion and the reproducing was performed again, the initial high resistance state (tunnel current = 0.1 nA) was returned, and the recorded information was erased. I was able to confirm that.

Next, the produced recording medium was subjected to load scanning using an AFM device to measure the adhesiveness of the recording layer. The cantilevers and tips used in the AFM device were made of silicon nitride. The measurement was performed by scanning the tip 20 times in a 500 nm square with a load of 2 × 10 ⁻⁷ N. As a result, no damage such as film peeling was observed on the surface of the recording layer after scanning, and it was revealed that the recording medium has sufficient strength.

(Second Embodiment) FIG. 4 is a block diagram showing another example of the information processing apparatus of the present invention. Reference numeral 1 is a recording medium, 2 is a probe electrode provided facing the recording medium 1, 3 is a cantilever to which the probe electrode 2 is attached, and 4 is a support for the cantilever 3. The cantilever 3 allows the probe electrode 2 to be displaced in the z-axis direction. The medium 1 can be moved by a small amount in the x-, y-, and z-axis directions by the xyz fine movement device 5.
It can be moved by the coarse movement device 6. The cantilever support 4 and the xyz coarse movement device 6 are fixed to a base 7. Although not shown, the base 7 is installed on the seismic isolation table.

The cantilever 3 was manufactured by using the silicon etching technique. Anisotropic etching method that uses the properties of silicon crystal to a length of 100 μm and a width of 20 μm
A SiO ₂ cantilever having a thickness of 1 m and a thickness of 1 μm was formed. This method is known (KE Petersen Proc. IEEE., 70, 42.
0 (1982)). In the probe electrode 2, Si ions are implanted into one end of the SiO ₂ cantilever 3 produced by the anisotropic etching, and Si is selectively crystal-grown on the Si to form a pyramidal crystal with a sharp tip. After forming 201, Au was vapor-deposited to a thickness of 300 Å by a vacuum vapor deposition method to form a conductive layer 202, which was manufactured. The xyz fine movement device 5 uses a cylindrical piezoelectric element and can finely move the recording medium 1 in the x-, y-, and z-axis directions by applying an arbitrary voltage.
The xyz coarse movement device 6 uses an xyz stage.

Probe electrode 2 and base electrode 1 of recording medium 1
Reference numeral 02 is connected to a voltage application circuit for applying a recording / erasing voltage and a voltage application and current detection circuit 10 including a current detection circuit for detecting a current flowing between the probe electrode 2 and the recording medium 1.

Xyz fine movement device 5 and xyz coarse movement device 6
Are driven by control circuits 8 and 9, respectively. These circuits and the voltage application / current detection circuit 10 are connected to and controlled by the microcomputer 12.

A recording medium was formed in the same manner as in Example 1,
Information was recorded, reproduced, and erased by the information processing apparatus shown in FIG.

After fixing the recording medium 1 on the xyz fine movement device 5, a bias voltage of 100 mV is applied between the probe electrode 2 and the Au electrode 102, and the xyz coarse movement device 6 and x are moved.
The yz fine movement device 5 is driven to bring the medium 1 close to the probe electrode 2. When the distance between the probe electrode 2 and the recording medium 1 was monitored while monitoring the current flowing between them, a current characteristic as shown in FIG. 8 (curve indicated by I in the figure) was obtained.

On the other hand, when the probe electrode 2 and the recording medium 1 approach each other, a force acts between them and the cantilever 3 is deformed by the force. Using the optical lever method that detects the deviation of the reflected beam of the laser beam on the cantilever, the amount of deformation was measured at the same time as the current characteristics, and the results are also shown in FIG. 8 (F in the figure). Curve indicated by.

In the region a in FIG. 8 where a repulsive force acts between the probe electrode 2 and the recording medium 1, the current flowing between them is almost constant with respect to the distance between them. Therefore, in the subsequent scanning, first, the current is monitored by the circuit 10,
The repulsive force (specifically, 10) between the probe electrode 2 and the recording medium 1 is controlled by the microcomputer 11.
^-8 [N] or so) close to the working distance.

In this state, the xyz fine movement device 5 moves the medium 1
By fixing the position of z in the z-axis direction and moving the medium 1 in the x-axis and y-axis directions, the medium 1 is moved by the probe electrode 2.
To scan. During information recording, the circuit 10 applies a voltage equal to or lower than a threshold voltage for turning on the medium at a predetermined position according to the recording information during the scanning. As a result, information is recorded on the medium 1 (recording of all 0 signal).

At the time of erasing, while applying a voltage equal to or lower than a threshold value for returning the medium to the OFF state, the probe electrode 2 in the circuit 10 is applied.
The current flowing between the medium and the medium 1 is detected. The change state of the detected current at this time indicates the information recorded on the medium.

As described above, the tip of the probe electrode and the surface of the recording medium are brought close to each other up to a distance at which the repulsive force works, and the probe electrode 2 is placed on the surface of the recording medium 1 in a state in which the support of the probe electrode is elastically deformed by the repulsive force. The recording medium is scanned with the recording medium 1, and at the same time, a medium change voltage is applied between the probe electrode 2 and the recording medium 1 for recording and erasing, and a minute voltage is applied to detect a current flowing through the recording medium. , Ie, detect the recorded bit.

Since the support of the probe electrode is used in an elastically deformed state due to the repulsive force acting between the probe electrode tip and the recording medium surface, the probe electrode tip approaches the medium surface due to the irregularity of the medium surface, and the repulsive force becomes large. For example, if the support deforms and the probe electrode tip moves away from the medium surface, and if the probe electrode tip moves away from the medium surface and the repulsive force decreases, the support deforms in the opposite direction and the probe electrode tip moves toward the medium. If the amount of deformation of the probe electrode support due to the surface unevenness during scanning approaches the surface and is within the elastic deformation range, the distance between the probe electrode 2 and the surface of the medium 1 is determined by attaching an actuator to the support and changing the amount of support deformation Therefore, it will be kept almost constant without feedback control.

Furthermore, in this state, the current signal detected by applying a minute voltage between the recording media of the probe electrodes does not include the current signal due to the unevenness of the surface of the recording medium. Playback is possible.

Further, in the present invention, the recording medium used for recording, reproducing and erasing described above has improved mechanical strength on the surface of the recording medium due to the method of forming the recording medium described above. Even if a load is applied when the probe electrode is scanned, the risk of deforming the recording medium surface at the probe electrode tip is reduced, and it is possible to reduce recording, reproduction, and erasing errors due to trouble during scanning. It was

Next, the recording, reproducing and erasing experiments carried out in this apparatus will be described.

While the detection current is being monitored, the distance between the probe electrode 2 and the recording medium 1 is brought close to the state shown in area a of FIG. 8, and in this state the control circuit 8 of the xyz fine movement device 5 and the xyz coarse movement device 6 is moved. , 9 are held and a triangular wave pulse voltage having a waveform shown in FIG. 6, which is a voltage equal to or higher than the threshold voltage VthON for generating the ON state, is applied between the probe electrode 2 and the Au electrode 102, and then 100 mV is applied again. When a bias was applied and measurement was performed, a current of about 8 μA flowed, indicating that the device was in the ON state.

Next, after applying the triangular wave pulse voltage having the waveform shown in FIG. 7 at a voltage equal to or higher than the threshold voltage VthOFF which changes from the ON state to the OFF state, when a bias of 100 mV is applied again, the current value is about 1 nA. And OF
It was confirmed to return to the F state.

Next, in the same manner as described above, the y and z axes of the xyz fine movement device 5 are fixed with the distance between the probe electrode 2 and the recording medium 1 approached to the distance shown by the area a in FIG.
When it was driven only in the axial direction and the current was monitored, the current value showed a constant value of approximately 1 nA. Next, while driving only in the x-axis direction, a triangular wave pulse voltage equal to or higher than the threshold voltage VthON having the waveform of FIG. 6 is applied at intervals of 10 nm between the probe electrode 2 and the Au electrode 102, and then the bias 1 is applied.
When the current flowing between the probe electrode 2 and the Au electrode 102 was measured again by repeatedly driving only in the x-axis direction at a constant value of 00 mV, a current that changed by about 4 digits in a 10 nm cycle was observed, and the ON state was It was confirmed that the data was written periodically. Further, the ratio of the current in the ON state and the current in the OFF state also kept a substantially constant value.

Further, the area in which the ON state is periodically written is scanned again only by the x-axis drive, and an arbitrary O
In the state in which the xyz fine movement device 5 is stopped on the N state region and this position is held, the threshold voltage Vth having the waveform of FIG.
A triangular wave pulse voltage of OFF or more was applied. When the current was measured by repeating scanning only in the x-axis direction, it was confirmed that the ON state of the region to which the pulse was applied was erased and the state returned to the OFF state showing a current of about 1 nA. Similar to this arbitrary bit erasing, the voltage between the probe electrode 2 and the Au electrode is set to the threshold value VthOFF or more, the recording area is scanned, and then the current is measured.
It was confirmed that the value was almost constant at about A and all the ON states recorded in the 10 nm cycle were erased and turned to the OFF state.

Subsequently, the xyz fine movement device 5 is controlled to 1n.
When a stripe having a length of 1 μm was written at various pitches between m and 1 μm by the above method and the resolution was measured, a current change of about 4 digits was always confirmed at the same pitch as the write pitch at a pitch of 3 nm or more. However, when the pitch was less than 3 nm, the change in the amount of current gradually decreased.

Further, during the above experiment, there was no deformation of the surface of the recording medium by the probe electrode and no error during scanning of the probe electrode.

(Embodiment 3) Next, according to the method of forming the cantilever and the method of forming the probe electrode used in Embodiment 2, SiO ₂ having a length of 100 μm, a width of 20 μm and a thickness of 1 μm is formed on the Si substrate of one side. A plurality of cantilevers were formed, and a probe electrode was provided at the tip of each cantilever.

As shown in FIG. 5, the Si substrate 4 on which the cantilever was formed was fixed to the support base 13. The support 13 is attached to the base 7 via at least three piezoelectric elements 14. These piezoelectric elements 14 are individually driven by the piezoelectric element control circuit 12 controlled by the microcomputer 11. Further, the voltage application and current detection circuit 10 applies a voltage to each probe electrode 2 and individually detects the current flowing between each probe electrode 2 and the recording medium 1.

The other structure is similar to that of the first embodiment.

The recording medium was the same as in Example 1 except that the recording layer was as follows.

That is, a smooth electrode substrate and an adhesion layer were formed in the same manner as in Example 1.

Next, the polyamic acid represented by the formula (2) and N, N-dimethyloctadecylamine were each added to dimethylacetamide (DMA) at a monomer conversion concentration of 1 × 10 ⁻³ M.
The solution dissolved in C) was mixed 1: 2 (v / v) to prepare a polyamic acid amine salt solution.

[0083]

[Chemical 2] Using this solution, a monolayer cumulative film of a polyamic acid amine salt of 6 layers was formed in the same manner as in Example 1.

Next, the substrate was heated and baked at 300 ° C. for 10 minutes to form a recording layer of a polyimide film.

The recording medium formed in this way was recorded with AF
When M was used for scanning with a load of 1 × 10 ⁻⁷ N, no deformation of the surface of the recording medium was observed.

Then, the recording medium 1 was driven by the xyz fine movement device 5 to bring them close to each other while applying a bias of 100 mV between the probe electrode 2 and the Au electrode 102.
At this time, the piezoelectric element 14 was controlled to adjust all the probe electrodes so as to uniformly approach the recording medium 1, and all the probes were brought close to each other until the state of the area a in FIG. 8 was reached. Under this condition, while the medium 1 was moved in the x direction by the xyz fine movement device 5, the same recording, reproducing, and erasing operations as in Example 1 were performed for each probe electrode 2.

Next, an experiment in this apparatus will be described. In the approaching state described above, controlling the xyz fine movement device,
When the current flowing between each probe electrode 2 and the Au electrode 102 was measured while driving in the xy plane of the recording medium, all showed a current value of about 1 nA, and the current flowing through each probe electrode was being scanned. The change was extremely small.

Next, the recording operation will be described with reference to FIG. While driving the recording medium in the xy plane as described above,
Individual bit information for each probe electrode (Fig. 9 (a))
Based on the above, a write pulse train as shown in FIG. 9B was generated and added. Here, the first bit of the bit information is set as a bit corresponding to the ON state for all individual bit information (a-1 in the figure). After applying the pulse, the recording medium was driven again in the xy plane by the same method as that for writing, and the current flowing between the probe electrode 2 and the Au electrode 102 was measured under the condition of applying a bias of 100 mV. The change is obtained for each probe electrode, and the pulse train obtained by binarizing these current measurement values is used to obtain individual bit information (FIG. 9) applied to each probe electrode 2.
It coincided with (a)).

Next, an erase pulse train as shown in FIG. 9C is generated based on the individual bit information written above. Here, it is assumed that the first bit remains ON for all bit information and is not erased. Drive the recording medium in the xy plane in the same way as when writing,
The current value was measured, and the driving of the medium was temporarily stopped at the first bit, that is, at the position where the current value first changed by about 4 digits. At this time, a change of about 4 digits was observed for all probe electrodes 2 according to the condition of the bit information defined at the beginning. Subsequently, the drive of the medium was restarted, and the individual erase pulse trains previously generated were applied to the individual probes 2 in synchronization with this. Again, the recording medium 1 is recorded in the same manner as when writing.
Was driven in the xy plane to measure the current, and all except the first bit were in the OFF state, that is, the current value was about 1 nA, and it was confirmed that the erasing was completed.

Instead of the erase pulse used here, of the bit information used for writing, any bit except the first bit is selected to generate the erase pulse train ((d) in FIG. 9), and When an erase experiment was performed in the same manner as the method, it was confirmed that only selected bits were erased.

Further, also in this embodiment, there was no deformation of the surface of the recording medium by the probe electrode or sudden change of the position of the probe electrode, and there was no error during scanning of the probe electrode.

Example 4 In this example, the substrate was immersed in an ethanol solution of 3-mercaptopropyltriethoxysilane (concentration 1 mM) to form a monomolecular adsorption layer. A recording medium was formed in the same manner as in Example 1 except that a monomolecular accumulating film of a polyamic acid amine salt of the layer was formed and heated and baked at 300 ° C. for 10 minutes to form an adhesion layer. When the same recording, reproduction and erasing were performed, the same good result was obtained.

Also in this embodiment, there was no deformation of the surface of the recording medium due to the probe electrode and no error during scanning of the probe electrode.

Comparative Example 1 After forming a smooth substrate in the same manner as in Example 1, a recording layer of polyimide LB film was formed on the smooth substrate in the same manner as in Example 1 without performing the adhesion layer forming operation. The adhesion of this recording medium was measured in the same manner as in Example 1. As a result, 500 nm under a load of 2 × 10 ^-7 N
In the tip scanning within the corner, damage started to be observed in the recording layer in the third scanning, and film peeling occurred in the sixth scanning.

[0095]

According to the present invention, an adhesive layer made of molecules having an SH group and a siloxane bond is provided between an electrode layer made of a noble metal and a recording layer made of an organic film, so that the adhesiveness of both layers can be sufficiently improved. Can be increased.

Due to the improved adhesion, (1) even when the probe comes into strong contact with the recording layer for some reason such as an external shock during recording / reproducing of information, the mechanical strength is much higher than that of the conventional one. It is possible to provide a recording medium exhibiting the following: (2) In an information processing device in which the recording medium and the probe electrode are in close proximity,
It is possible to avoid the risk of deformation or destruction of the surface of the recording medium.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a layer structure of a recording medium of the present invention.

FIG. 2 is a cross-sectional view showing an example of a manufacturing process of the recording medium of the present invention.

FIG. 3 is a schematic diagram showing a configuration of an information processing apparatus to which the STM of Example 1 is applied.

FIG. 4 is a schematic diagram illustrating a configuration of an information processing device according to a second exemplary embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of an information recording processing device according to a third embodiment.

FIG. 6 is a waveform diagram showing a pulse voltage waveform for recording.

FIG. 7 is a waveform diagram showing a pulse voltage waveform for erasing.

FIG. 8 is a graph showing the relationship between the distance between the probe electrode and the recording medium, the current flowing between them, and the force acting between them.

FIG. 9 is a waveform diagram showing bit information, a recording layer pulse train, and an erase pulse train given to one probe electrode in the experiment of Example 3.

FIG. 10: MI in which the recording medium of the present invention is sandwiched between metal electrodes
It is a schematic perspective view of an M element.

11 is a graph showing current-voltage characteristics obtained with the device of FIG.

12 is a graph showing current-voltage characteristics showing the memory effect obtained by the device of FIG.

FIG. 13 is a schematic diagram showing an example of the positional relationship between the probe electrode scanning pattern and the tracks and recording bits on the surface of the recording medium of the present invention.

[Explanation of symbols]

 1 recording medium 2 probe electrode 3 cantilever 4 cantilever support 5 xyz fine movement device 6 xyz coarse movement device 7 base 8 xyz fine movement device control circuit 9 xyz coarse movement device control circuit 10 voltage application and current detection circuit 11 Microcomputer 12 Control Circuit of Piezoelectric Element 13 Support 14 Piezoelectric Element 72 Monomolecular Accumulation Film 73, 74 Metal Electrode 101 Substrate 102 Electrode Layer 103 Recording Layer 104 Track 105 Adhesion Layer 201 Si Crystal 202 Conductive Layer 203 Support 204 Z Axis Linear actuator 205 X-axis linear actuator 206 Y-axis linear actuator 207 XY stage 301 Amplifier 302 Logarithmic compressor 303 Low pass filter 304 Error amplifier 305 Driver 306 Stage drive circuit 307 High pass filter 308 Scan power supply 309 servo circuit 501 scan pattern 502 data bits

Claims (12)

[Claims] 1. A recording medium in which at least an electrode layer and a recording layer are laminated, wherein the electrode layer and the recording layer are laminated via an adhesion layer containing a molecule having a thiol group and a siloxane bond. A recording medium characterized by the above. 2. The recording medium according to claim 1, wherein the electrode layer is made of gold. 3. The recording medium according to claim 1, wherein the recording layer has a thickness of 100 Å or less. 4. The recording medium according to claim 1, wherein the recording layer is a polyimide film. 5. The recording medium according to claim 4, wherein the polyimide film is formed by imidizing a monomolecular film of a polyamic acid amine salt obtained by the Langmuir-Blodgett method. 6. The polyimide film is formed by imidizing a monomolecular accumulating film of a polyamic acid amine salt obtained by the Langmuir-Blodgett method.
The recording medium described. 7. The recording medium according to claim 1, means for applying a voltage between the recording medium and a probe electrode arranged to face the recording medium, the recording medium and the probe. Current detection means for detecting a current flowing between the electrodes, interval setting means for setting the distance between the recording medium and the probe electrode, and interval holding means for holding the set interval constant during scanning of the probe electrodes Information processing equipment. 8. The information processing apparatus according to claim 7, wherein there are a plurality of probe electrodes, and each of the probe electrodes has a space holding means. 9. The information processing apparatus according to claim 7, wherein the space maintaining means is means for detecting an atomic force between the recording medium and the probe electrode and moving the probe electrode based on the detected value. . 10. The information processing apparatus according to claim 7, wherein the space holding means is an elastic support body that supports the probe electrode that is bent by the repulsive force between the recording medium and the probe electrode. 11. The information processing apparatus according to claim 7, wherein the distance between the recording medium and the probe electrode is set to a distance at which a tunnel current can flow by the distance setting means, and the distance maintaining means is used. An information reproducing method for performing reproduction by detecting a tunnel current flowing between the recording medium and the probe electrode while maintaining the distance, and detecting an electric characteristic of the recording medium. 12. The information processing apparatus according to claim 7, wherein a voltage is applied between the recording medium and the probe electrode to change the electric characteristics of the recording medium. The method of recording information.