JPH02146128A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a high density recording and reproducing device with a memory property by generating a reversible change of state owing to an oxidation-reduction reaction in a recording medium disposed between a probe electrode and an opposite electrode under the presence of electrolyte. CONSTITUTION:The probe electrode 102 fitted with a fine moving control mechanism 107 and the opposite electrode 103 in opposition to this probe electrode are disposed in the electrolyte 115 which supplies moving ions, and a recording layer 101 is provided on the electrode 103. The reversible change of state between the oxidation state and reduction state is generated on the layer 101 by impressing a pulse voltage from a power source 108. Then, a probe current between the electrodes 103 and 102 is controlled to be constant by a servo circuit 106 for controlling the mechanism 107. At the same time, by controlling a distance between the electrode 102 and the recording medium 1, an area where the oxidation-reduction reaction takes place can be microminiaturized. By this method, the recording and reproducing device with higher density than an optical recording can be obtained.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a recording/reproducing device. More specifically, the present invention relates to a recording/reproducing device in which a recording medium disposed between at least a pair of electrodes, one of which is a probe electrode, undergoes a reversible state change through an electrochemical redox reaction in the presence of an electrolyte. [Prior Art] In recent years, the use of memory materials has become a core part of the electronics industry, such as computers and related equipment, video disks, digital audio disks, etc.
The development of materials for this purpose is also actively progressing. The performance required of memory materials varies depending on the application, but generally high density and large storage capacity are required. Until now, semiconductor memories and magnetic memories were mainly made of magnetic materials and semiconductors, but with the recent advances in laser technology, inexpensive and high-density optical memories using organic thin films such as organic dyes and photopolymers have been developed. Recording media have appeared. In optical memory, irregularities on the surface of the recording medium. High-density recording and reproduction on the order of μm has become possible by utilizing differences in reflection weight. Thin films of metals or metal compounds, thin films of organic dyes, etc. are used as such recording media, and information is recorded by making holes or changing reflectance through evaporation and melting using the heat of laser light. In this method, the recording density is determined by the spot diameter of the laser beam used. However, as video information technology is rapidly progressing, there is an increasing demand for the development of smaller, larger-capacity, and higher-density memories. On the other hand, recently, a scanning tunneling microscope (hereinafter abbreviated as STM) that can directly observe the electronic structure of surface atoms of a conductor has been developed.
tica Physica Acta. 55, 726 (1982)] Real space images can now be measured with high resolution regardless of whether they are single crystal or amorphous, and they also have the advantage of being able to be observed with low power without damaging the medium due to current. Furthermore, it is expected to have a wide range of applications because it can operate in the atmosphere and can be used with various materials. STM involves applying a voltage between a metal tip and a conductive material.
It takes advantage of the fact that a tunnel current flows when brought close to a distance of about nn. This current is very sensitive to changes in the distance between the two, and by scanning the probe while keeping the tunnel current constant, it is possible to draw the surface structure in real space, and at the same time, it is possible to draw the surface structure in real space. Various information can also be read. Analysis using STM is limited to conductive samples, but it is beginning to be applied to the structural analysis of extremely thin monomolecular films formed on the surface of conductive materials, using the differences in the states of individual organic molecules. Application as a reproduction technology for high-density recording is also considered. Applications of STM to recording and reproducing technology include methods for changing the surface condition of a recording medium using electromagnetic waves such as electron beams, ion beams, X-rays, and light, and then reproducing the information using STM. A method has been proposed in which recording and reproduction are performed using STM using a thin film layer of a material having a memory effect, such as a thin film layer of chalcogenides or a thin film layer of a π-electron based organic compound. In addition, an attempt has been made to apply a voltage that causes field emission to the STM probe electrode to locally melt the Rh-Zr alloy sample surface to form cone-shaped protrusions. [U,
5tafer et all, Appl, Phys
, Lett, 51(4)27 July 1987
] Conventionally, the method of forming a latent image by discharging or energizing using a needle-like electrode is known as an electrostatic recording method, and has been applied to many recording papers etc. (Japanese Patent Laid-Open No. 49-343
Publication No. 5). However, the film thickness used in this electrostatic recording medium is on the μ order, and there have been no reports of an example in which a latent image on the medium is electrically read and reproduced. On the other hand, a proposal for a molecular electronic device in which a single organic molecule has functions such as a logic element or a memory element was announced, and a Langmuir-Blodgett film (hereinafter referred to as LB), which is considered to be one of the construction technologies for molecular electronic devices, was announced. Research on membranes (abbreviated as membranes) is also becoming more active. The LB film is a homogeneous super-Fl) film in which organic molecules are laminated one molecular layer at a time, and the film thickness is controlled in units of molecular length. Many attempts have been made. [Problems to be Solved by the Invention] An object of the present invention is to provide a recording/reproducing device with memory properties and higher density than conventional ones by causing molecules or molecular groups to undergo a reversible state change through an oxidation-reduction reaction. It's about doing.

[Means for Solving the Problems] The present invention has at least one probe electrode and a counter electrode disposed opposite to the probe electrode, and in the presence of an electrolyte that supplies mobile ions and the electrolyte, an external voltage is applied. A recording medium capable of easily controlling a reversible state change between an oxidized state and a reduced state by application is disposed between the probe electrode and the counter electrode, and further includes a recording medium between the probe electrode and the counter electrode. The recording and reproducing apparatus is provided with means for applying a voltage and means for controlling the distance between the probe electrode and the recording medium. The present invention provides means for disposing a recording medium and an electrolyte exhibiting a reversible state change through a redox reaction between at least one probe electrode and a counter electrode, further comprising means for applying a voltage between the two electrodes, and a means for applying a voltage between the probe electrode and the counter electrode. It is characterized in that it is provided with means for controlling the distance between the recording medium and the recording medium. Electrochromism is a typical phenomenon based on reversible state changes caused by redox reactions. Electrochromism refers to the phenomenon in which one or both electron transfer bodies become colored by an electrochemical redox reaction, and has been applied to display elements. Among organic substances, it is used in viologen derivatives, styryl-like compounds, and rare earth sifthalodianines. Zero coloration, which is known as It is understood that it is based on doing. In the present invention, at least one probe electrode is used for one electrode, and the probe electrode is brought very close to the recording medium using STM, to about 1 mm, thereby limiting the area where the redox reaction occurs. High-density recording is achieved by creating molecules or molecular groups with different electronic states in minute regions. Discrimination of such regions with different electronic states is impossible with the reading methods conventionally used for optical recording, and is only possible using STM, which is extremely sensitive to the spread of electron clouds in the vicinity of molecules. That is, another feature of the present invention is that the difference in the states of molecules or molecular groups in the recorded area and the unrecorded area is electrically detected. Specifically, detection is performed by changes in the tunnel current value flowing between the probe electrode and the counter electrode, but the distance between the probe electrode and the recording medium is controlled to keep the tunnel current value constant, and the detection is performed using the control signal at that time. You can. When analyzing a sample with low conductivity using STM, a very thin film of several tens of angstroms or less must be formed on the surface of a conductive material. It is also possible to apply a vapor deposition method, a cluster ion beam method, etc., but the LB method is extremely suitable among known conventional techniques due to its controllability, ease, and reproducibility. The LB method is a molecule with a structure that has a hydrophilic site and a hydrophobic site, and when the balance between the two (amphiphilic balance) is maintained appropriately, the molecule lowers the hydrophilic group on the water surface. This is a method of creating a monomolecular film or a cumulative film thereof by utilizing the fact that monomolecular layers form toward According to this LB method, a monomolecular film of an organic compound having a hydrophobic site and a hydrophilic site in one molecule or a cumulative film thereof can be easily formed on a substrate, and has a thickness on the order of a molecule. , and can stably supply a uniform and homogeneous ultra-thin organic film over a large area. Therefore, an ultra-thin film required for STM analysis can be easily formed. Furthermore, regarding the response speed, which is a weak point of electrochromism, the rate-limiting factor is the drift speed of free charges, which is not a problem in such an ultra-thin film state. In the present invention, the substrate for supporting the thin film in which inorganic and organic materials are laminated may be any metal, glass, ceramic, plastic material, or the like. The above-mentioned substrate may have any shape and is preferably flat, but is not limited to a flat plate. In other words, in the film forming method, the film can be formed in any shape regardless of the shape of the surface of the substrate. This is because it has certain advantages. On the other hand, the electrode material used in the present invention may be any material as long as it has high conductivity and does not cause unnecessary reactions with the electrolyte, such as Au, Pt, and Ag. Pd, AI2. There are many materials including metals such as In, Sn, Pb, and W, alloys thereof, graphite, silicide, and even conductive oxides such as ITO, and their application to the present invention is considered. It will be done. As a method for forming electrodes using such materials, conventionally known thin film techniques are sufficient. However, as for the electrode material on which the LB film is directly formed, it is preferable to use a conductive material whose surface does not form an insulating oxide film when forming the LB film, such as a noble metal or an oxide conductor such as ITO. In addition, the tip of the probe electrode needs to be as sharp as possible in order to increase the resolution of recording/reproducing/erasing.In the present invention, the tip of platinum with a thickness of 1 mm is mechanically polished into a 90" cone. Although a probe in which surface atoms are evaporated by applying an electric field in an ultra-high vacuum is used, the shape of the probe and the processing method are not limited to this in any way. Figure 1 shows the block configuration of the recording device of the present invention. In Fig. 1(A), ]05 is a probe current amplifier;
06 is a servo circuit that controls the fine movement mechanism 107 using a piezoelectric element so that the probe current is constant. 108
is a pulse power source for applying a pulse voltage for recording/erasing between the probe electrode 102 and the counter electrode 103. Since the probe current changes rapidly when the pulse voltage is applied, the servo circuit 106 controls the HOLD circuit to be turned on so that the output voltage remains constant during that time. +09 is an XY scanning drive circuit for controlling the movement of the XY force direction probe electrode 102. The coarse movement mechanism 110 and the coarse movement drive circuit 111 control the coarse movement of the distance between the probe electrode 102 and the recording medium 1 so that a probe current of about 10-'A can be obtained in advance. All of these functions are centrally controlled by a microcomputer 112. Further, 113 represents a display device. In addition, the mechanical performance in movement control using piezoelectric elements is shown below. Z-direction fine movement control range: O, lnm - 2-direction coarse movement control range + 1 Or + n + -10 mm XY direction scanning range: O, lnm - lpml side m measurement. Tolerance error: <O, Inm The present invention will be described below with reference to Examples. [Example 1] A recording/reproducing apparatus shown in FIG. 1 was used. Probe electrode 10
As No. 2, a platinum probe electrode was used. This probe electrode 1102 is used to control the distance (Z) from the surface of the recording layer 101, and the distance (Z) is controlled by a piezoelectric element to keep the current constant. Furthermore, the fine movement control mechanism 107 is designed to be able to perform fine movement control also in the in-plane (x, y) directions while keeping the distance 2 constant. However, these are all conventionally known techniques. Further, the probe electrode 102 can be used for direct recording, reproduction, and erasing. Further, the recording medium is placed on a high-precision XY stage 1!4 and can be moved to any position. Next, lutetium siphthalodianine [Lu)I (Pc) 2 was formed on the counter electrode 103 formed of ITO.
The details of recording, reproducing, and erasing experiments using a t-butyl-derived monolayer are described below. A recording medium 1 having a recording layer +01 made of a monomolecular film of a [Lutl (Pc) 2 ] butyl derivative is fixed on an XY stage, and then the recording layer and the tip of the probe are immersed in a potassium chloride aqueous solution as an electrolyte 115. I added up to. 0.3V with the counter electrode formed of ITO as a cathode
The distance (Z) between the probe electrode 102 and the surface of the recording layer 101 was adjusted while applying the voltage and monitoring the current. After that, by controlling the fine movement control mechanism 107, the probe electrode 1
02 and the surface of the recording layer 101 was further adjusted within a minute range. At this time, the applied voltage was kept within a range that did not cause a change in the state of the recording layer. Next, with the opposing electrode as an anode, a voltage of 0.2V is applied so that the probe current from the servo circuit 106 is constant.
The XY scanning drive circuit does not give a control signal to the Z direction fine movement mechanism +07! I started operating 09. The control signal from the servo circuit 106 corresponds to the unevenness on the surface of the recording layer 101, but as a result, no unevenness with a period of 2 nm or more was observed on the surface of the recording layer 101. After that, after holding the output of the xY scan drive circuit +09 and fixing the position of the probe, the pulse power supply 10 is turned on.
8, a rectangular pulse of 1.5 V was applied using the counter electrode as an anode. When the XY scan drive circuit 109 was operated again and the area around the held position was scanned and the surface was observed, depressions with a diameter of 10-odd nm were seen superimposed on the previously observed irregularities with a period of 2 layers or less. Ta. After further moving the position of the probe, while operating the XY scan drive circuit +09, set the counter electrode as an anode and apply 1.2V.
A rectangular pulse train of an appropriate period with an amplitude of . Thereafter, a voltage of 0.2 V was applied using the counter electrode as an anode, and the surface of the scanning recording area was observed. As a result, long-period irregularities in which irregularities with a period of 2 layers or less were superimposed were observed. This period matched the period found from the XY scanning speed of the probe and the period of the pulse train. Next, the same scanning recording area was scanned in an XY manner using the opposite electrode as a cathode while applying a voltage of 0.4V, and then surface observation was performed using the opposite electrode as an anode and applying a voltage of 0.2V. When I did it,
Only irregularities of 2 layers m or less were observed, and longer period irregularities were not observed. t- of [Lu)I (Pc) z] used in the above experiments
A monomolecular film of a butyl derivative was prepared as follows. After cleaning the optically polished glass substrate (substrate 104) using a neutral detergent and Triclean, it is coated with I by sputtering.
TO was vacuum-deposited to form an electrode (103). next[
The t-butyl derivative of LuH(Pc) 2] was dissolved in a mixed solvent of chloroform/trimethylbenzene/acetone (1/l/2) to obtain a solution with a concentration of 0.5 mg/mβ. The above-mentioned substrate was submerged in a pure water phase at 20° C. and then developed on the above-mentioned solution water phase to form a monomolecular film on the water surface. Waiting for the solvent to evaporate, the surface pressure of the monomolecular film was increased to 20 mN/m, and while keeping this pressure constant, the substrate was gently pulled across the water surface at a speed of 3 mm/min to deposit the monomolecular film on the substrate. Formed. [Example 2] An experiment was conducted in the same manner as in Example 1, except that lithium phthalocyanine (Li, Pc) was used instead of the t-butyl derivative of LuH(PC) 2 used in Example 1. Furthermore, in this example, a Z-shaped monomolecular film cumulative film was obtained by repeatedly dipping the substrate across the water surface and pulling it up. Through this operation, five types of cumulative films of 1.3, 5° and 7.9 layers were obtained. Formed. The same results as in Example 1 were obtained when the write voltage was set to 2 V with the counter electrode as the anode, the read voltage was 0.2 V with the counter electrode as the anode, and the erase voltage was set with the counter electrode as the cathode. In the samples with 1 and 3.5 layers, the contrast between the recorded and unrecorded areas was good, and the change in layer thickness was extremely small, but with 7 or more layers, the contrast decreased as the cumulative number of layers increased. Ta. In the examples described above, the LB method has been used to form the recording layer, but any method that can create an extremely thin and uniform film can be used other than the LB method. For example, a vacuum deposition method such as a CVD method or the like can be mentioned. The materials that can be used include not only other organic compounds that exhibit reversible state changes through redox reactions, but also inorganic materials such as tungsten oxide. Note that the present invention does not limit the substrate material, its shape, or surface structure in any way. [Effects of the Invention] ■A completely new recording and reproducing method that enables much higher density recording than optical recording has been disclosed. ■Since the recording layer is formed by the accumulation of monomolecular films, film thickness control on the order of molecules (several to dozens of people) can be easily achieved. Furthermore, since the controllability is excellent, the reproducibility is high when forming the recording layer. ■Since the recording layer can be thin, it is possible to provide a highly productive and inexpensive recording medium. ■The energy required for reproduction is small and the power consumption is low.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing a recording/reproducing apparatus of the present invention. 1: Recording medium 101: Recording layer 102 Niprobe electrode 03: 04: 05: 06: 07: 08: 09: 11O: l l: 12: l 3: l 4: l 5: Opposing bridge substrate probe current amplifier Servo circuit Fine movement control mechanism Pulse power supply XY scanning drive circuit Coarse movement mechanism Coarse movement drive circuit Microcomputer Display device XY stage Electrolyte

Claims (4)

[Claims] (1) An electrolyte having at least one probe electrode and a counter electrode disposed opposite to the probe electrode and supplying mobile ions, and in the presence of the electrolyte, an oxidized state and a reduced state are changed by external voltage application. A recording medium capable of easily controlling a reversible change in is disposed between the probe electrode and the counter electrode, and further comprises means for applying a voltage between the probe electrode and the counter electrode, and a recording medium capable of easily controlling a reversible change in the probe electrode. A recording/reproducing device comprising means for controlling a distance from the recording medium. (2) The recording/reproducing apparatus according to claim 1, wherein the recording medium has a monomolecular film of an organic compound or a cumulative film formed by accumulating the monomolecular film. (3) The recording/reproducing device according to claim 2, wherein the monomolecular film or the cumulative film is a film formed by a Langmuir-Blodgett method. (4) The recording/reproducing apparatus according to claim 1, further comprising an XY scanning drive device for the probe electrode.