JPS63222347A - Method and device for reproduction - Google Patents

Abstract

PURPOSE:To increase the capacity of reproduction and to reduce the cost thereof by using a semiconductor having an electric memory effect as one electrode and impressing the voltage which does not exceed the threshold voltage between said electrode and a probe electrode making a pair therewith thereby executing the reproduction of memory. CONSTITUTION:A recording medium 1 having a recording layer 101 consisting of chalcogenide glass is placed on an X-Y stage 114 and the voltage is impressed between the substrate electrode 103 and the probe electrode 102. Current is then monitored and the fine adjustment by fine adjustment control mechanism 107 is executed by adjusting the distance between the electrode 102 and the surface of the layer 101. The stage 114 is then moved at specified interval and the writing recording is executed by impressing the square pulse voltage above the threshold voltage between the electrodes. The reproduction of the recording is executed by impressing the voltage which does not exceed the threshold voltage between the electrode 102 and the electrode 103 and reading the change in the quantity of the current flowing in the electrode 102. the capacity of the reproduction is thereby increased and the cost thereof is reduced.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a playback device.

More specifically, the present invention relates to a reproducing device for reproducing information recorded on a semiconductor having a memory effect on the switching characteristics of voltage and current between a pair of electrodes, one of which is a probe electrode.

[Background technology]

In recent years, the use of memory materials has become a core part of the electronics industry, including computers and related equipment, video disks, digital audio disks, etc.
The development of these materials is also progressing very actively. The performance required of memory materials varies depending on the application, but in general, they are: ■High density and large recording capacity; ■Fast response speed for recording and playback; ■Low power consumption; ■High productivity and low price. Cheap, etc.

Up 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.

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)) It has become possible to measure real space images with high resolution regardless of whether they are single crystal or amorphous, and it also has the advantage of being able to observe with low power without damaging the medium by electric current. Among them, it is expected to have a wide range of applications because it works well 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 nm. This current is very sensitive to changes in the distance between the two, and by scanning the probe while keeping the tunneling current constant, it is possible to draw the surface structure in real space and at the same time draw various information about the total electron cloud of surface atoms. 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.

On the other hand, the conventional method of forming a latent image by discharging or energizing using needle-shaped electrodes is known as an electrostatic recording method, and has been applied to recording paper in many ways. 3
Publication No. 435).

The film thickness used in this electrostatic recording medium is on the μ order, and there have been no reports yet of an example in which a latent image on the medium is electrically read and reproduced.

[Purpose of the invention]

That is, an object of the present invention is to provide a novel, inexpensive and large-capacity reproducing device that reproduces recorded data by controlling the minute distance between a probe electrode and a conductive material and reading changes in the amount of current flowing through the probe electrode. The goal is to provide a method of regeneration.

[Summary of the invention]

The present invention uses an amorphous semiconductor deposited on an electrode and having an electric memory effect as a recording medium, and provides a voltage applying means for applying a voltage from the probe electrode to the semiconductor that does not exceed a threshold voltage that causes the electric memory effect, and to the semiconductor. The present invention is characterized by a reproducing device having a reading means for reading changes in the amount of current flowing through the semiconductor, and a reproducing method that reads changes in the amount of current flowing through the semiconductor by applying a voltage that does not exceed a threshold voltage that causes an electric memory effect.

[Detailed description of aspects of the invention]

The present invention utilizes the fact that a tunnel current flows when a voltage is applied between a metal probe and a conductive substance and the probe is brought close to a distance of about 1 nm. Since tunneling current depends on the work function at the surface, information about various surface electronic states can be read.

The method using tunnel current does not require vacuum conditions,
It can be applied to both single crystal and amorphous materials, and has many advantages such as high resolution and low power regeneration without damage caused by current.

Furthermore, since the tunnel current is on the order of nA, as a recording medium, it is necessary to
Preferably, any material having a conductivity of to″(Ωcm)−′ or more may be used.

As the recording medium used in the present invention, a material having a memory switching phenomenon in current/voltage characteristics can be used. For example, (1) Se, Te combined with oxide glass, borate glass, or elements of the (7) lit, IV, V, and Vl groups of the periodic table.

Examples include amorphous semiconductors such as chalcogenide glass containing As. They have an optical bandgap Eg of 0.6 to 1.4 eV or an electrical activation energy △
It is an intrinsic semiconductor with an E of about 0.7 to 1.6 eV. As a specific example of chalcogenide glass, As-5e-Te
system, Ge-As-5e system, 5i-Ge-As-Te system,
For example, 5i16 Ge14 As6 Teas (subscripts are atomic %), or Ge-Te-X system, Si-T
e −X system (X=low fi+7) V Vl group element), for example, Ge1B're8+5b2s2.

Furthermore, Ge-5b-3e-based chalcogenide glass can also be used.

In an amorphous semiconductor layer in which the above compound is deposited on an electrode, an electric memory effect of the medium can be expressed by applying a voltage using a probe electrode in a direction perpendicular to the film surface.

As a method for depositing such a material, conventionally known thin film forming techniques are sufficient to achieve the object of the present invention.

For example, suitable film-forming methods include a vacuum evaporation method, a cluster ion beam method, and the like. In general,
The electrical memory effect of such materials has been observed at film thicknesses of several μm or less, but in terms of recording resolution as a recording medium, thinner layers are preferable, but from the standpoint of uniformity and recording performance, thinner films with thicknesses of 100 Å or more and 1 μm or less are preferable. It is preferable that the film has a thickness of 1000 Å or less.

(2) Nihatetrakinoshita > (TCNQ), TC
NQ derivatives, such as tetrafluorotetracyanoquinodimenine (TCNQF4), tetracyanoethylene (
TcNE) and tetracyanonaphthoquinodimethane (TcNE) and tetracyanonaphthoquinodimethane (TcNE)
An organic semiconductor layer in which a salt of an electron-accepting compound such as NAP) and a metal having a relatively low reduction potential such as copper or silver is deposited on an electrode may also be mentioned.

As a method for forming such an organic semiconductor layer, a method is used in which the electron-accepting compound is vacuum-deposited on a copper or silver electrode.

hX4%S right car; Airplane/FN borrow as J < +1
-611 mIJ Tsuru
A film having a thickness of m is preferable.

(3) Another example is a recording medium made of amorphous silicon. For example, metal/a-3i (
p+ layer/n layer/i layer) or metal/a-S i(
The recording medium has a layer structure of (n+ layer/p layer/i layer), and each layer of a-Si can be deposited by a conventionally known method. In the present invention, glow discharge method (GD) is preferably used. The preferred thickness of a-8i is 2,000 to 8,000 for the n layer, about 1,000 for the i and p+ layers, and the total thickness is 0.5 μm.
A thickness of about 1 μm is preferable.

On the other hand, the electrode material used in the present invention may be any material as long as it has high conductivity, such as Au or Pt.

Ag, I'd, A1. In, Sn,
There are many materials including metals such as I'b and W, alloys thereof, graphite, silicide, and even conductive oxides such as ITO, and these materials are applicable to the present invention. A woman Ah Su Choussu 廿7ru R'11
．． x←As for the method of forming a monk pole, a conventionally known thin film technique is sufficient.

Further, the tip of the probe electrode needs to be as sharp as possible in order to improve the recording/reproducing/erasing resolution. In the present invention, a platinum tip with a thickness of 1φ is mechanically polished to a 90' cone, and an electric field is applied in an ultra-high vacuum to evaporate the surface atoms. The shape and processing method are not limited to these.

FIG. 1 is a block diagram showing a recording apparatus of the present invention. In FIG. 1(A), 105 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 recorded between the probe electrode 102 and the electrode 103/
This is a power supply for applying a pulse voltage for erasing.

Since the probe current changes rapidly when the pulse voltage is applied, the servo circuit 106 controls the II OLD circuit to be turned on so that the output voltage remains constant during that time.

109 is an XY scanning drive circuit for controlling the movement of the XY force direction probe electrode 102; Reference numerals 110 and 111 are for coarsely controlling the distance between the probe electrode 102 and the recording medium l so that a probe current of about IO-'A can be obtained in advance. All of these devices 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: 0. lnm-1μm Z-direction coarse movement control range: l On m-10m mXY-direction scanning range: 0. lnm-1μm measurement, control tolerance: <
0.1 nm Hereinafter, the present invention will be explained according to Examples.

(Example 1) A recording/reproducing apparatus shown in Fig. 1 was used.Probe electrode 1
As 02, a platinum probe electrode was used. This probe electrode 102 is used to control the distance (Z) from the surface of the recording layer 101, and the distance (Z) is finely controlled by a piezoelectric element so as to keep the current constant. Furthermore, the fine movement control mechanism 107 maintains the distance 2 constant and moves the in-plane (
It is designed to allow fine movement control in the x, y) directions as well. 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 l is placed on a high-precision XY stage 114 and can be moved to any position.

Next, Si is formed on the electrode 103 formed of Au.
, 1. Details of recording/reproducing/erasing experiments using chalcogenide glass (film thickness: 2000 mm) represented by the composition formula Ge 14 As y, Te 65 (subscripts are atomic %) will be described below.

A recording medium 1 having the recording layer 101 of chalcogenide glass having a thickness of 2000 μm was placed on the XY stage 114 between the Au electrode (ground side) 103 and the probe electrode 102 . 1. Applying a voltage of OV and monitoring the current, the probe electrode 102 and the recording layer InIaL; 7
iiQ/7'lVEIII (7) je-Ilml, f-
The fine movement mechanism 107 was controlled at 21 of -jF- by controlling the 1'41Wb control mechanism 107 so that the probe current Ip became 10-''A.

The probe current 1p for controlling the distance 2 between the probe electrode 102 and the surface of the recording layer 101 is IO-' A≧Ip
≧10-”A, suitable NiHA lO'-aA≧Ip≧l0-1
It is necessary to adjust the probe voltage accordingly.

While moving the XY stage 114 at fixed intervals (1 μ), a rectangular pulse voltage (
20V max , 0, 1 μs) was applied to create a low resistance state (ON state). After that, a probe voltage of t, OV for reading is applied between the probe electrode 102 and the counter electrode 103 to read the change in the amount of current flowing in the low resistance state region and the high resistance state region directly, or through the servo circuit 106. Can be read.

In this example, the probe current flowing through the ON state region before recording (
It was confirmed that there was a change of more than two orders of magnitude compared to the OFF state area).

Furthermore, as a result of tracing the recording position again while applying a rectangular pulse voltage (50V max l OμS) higher than the threshold voltage Vth OFF to the probe electrode, it was confirmed that all recorded states were erased and the state transitioned to the OFF state.

Furthermore, erasing of records is also possible using an optical method.

Next, using the fine movement control mechanism 107, 0. O1μ to 1μ
When the writing resolution of stripes with a length of 1 .mu.m was measured using the above method at various pitches between the two, it was found to be less than 0.1 .mu.m.

The chalcogenide glasses used in the above experiments were prepared as follows.

After cleaning the optically polished glass substrate (substrate 104) using a neutral detergent and Triclean, Cr was deposited as an undercoat layer to a thickness of 50 mm using the vacuum evaporation method, and Au was further deposited using the same method to a thickness of 400 mm. Base electrode (Au electrode 103)
was formed.

Next, an amorphous semiconductor having an atomic composition of Si 16 Ge 14 As 5 T ess was deposited to a thickness of 2000 nm by a conventionally known vacuum deposition method and used as a recording medium.

[Example 2] Si 16 Ge 14As 5Te used in Example 1
Instead of a6 recording medium, Ge, Tea+Sb
An experiment was conducted in exactly the same manner as in Example 1, except that 2 S2 was used. It was found that recording could be written and read with a sufficient S/N ratio as in Example 1.

[Example 3] A recording and reproducing experiment similar to that in Example 1 was conducted using CuTCNQF4 instead of the chalcogenide glass recording medium used in Example 1.2. The applied voltage for recording was 2 V.
A rectangular pulse of n+ax, l Ons was used, and the applied voltage for reproduction and probe current control was 0. It is set to lV. As a result, as in Example 1, recording and reproduction could be performed with a sufficient S/N ratio. Note that the resolution is 0.1μ
m or less. Next, a method for producing the Cu T CN Q F 4 recording medium will be described.

After cleaning the optically polished glass substrate, 2000 pieces of Cu were deposited by vacuum evaporation to form electrodes. Furthermore, Cu and TC
Co-depositing NQF4 by vacuum evaporation method to form Cu+TCNQ
2000 F4 layers were deposited (substrate temperature; room temperature). At this time, the deposition rate was set to Cu; 5A/5TCNQF4; 20 people/
A preset current value was applied so that the temperature was about S and heated. As a result, it was confirmed that a blue film was deposited due to the production of CuTCNQF4.

[Example 4] Electrodes were formed by vacuum evaporating Cr to a thickness of 500 mm on an optically polished glass substrate, and then Cr was vacuum deposited to a thickness of 100 mm using a glow discharge method.
A p+ type amorphous silicon film was formed. The creation conditions at that time are introduced gas; B2 II 6 / 5ilI4 (NB
H/N5iH=I O") (0.
(diluted to 0.025 mol%) r "power; 0.OIW/crr
r Pressure: 0.5 torr Substrate temperature: 300°C Deposition rate: 30 people/min. Next, after exhausting the excess raw material gas, new raw material gas is supplied to form 500% n-type amorphous silicon.
0 people were deposited. The preparation conditions are as follows.

Introduced gas; PH3/SIH4 (NPH/N5i
H = 5 X 10-3') (diluted to 0.05 mol% with 112 gas) RF power: O, QIW/csd pressure: 0.5 torr Substrate temperature: 300°C Deposition rate: 40 people/min Also, raw materials After exhausting the gas, SiH4 diluted to 0.05 mol% with H2 gas was introduced into the chamber, and with other conditions constant, i-phase amorphous silicon was
People piled up.

Recording and reproducing experiments similar to those in Example 1 were conducted on the recording medium produced as described above. As a result, recording and reproduction could be performed with a sufficient S/N ratio. Note that the following voltages were applied for recording, reproduction, and erasing.

For recording 20V For playback 0.5V For erasing -5V In the examples described above, various methods for producing recording media have been described, but any film formation method that can produce an extremely uniform film will suffice. It is not limited to this method. Note that the present invention does not limit the substrate material, its shape, or surface structure in any way.

〔Effect of the invention〕

■We have disclosed a completely new recording and reproducing method that allows for much higher density recording than optical recording.

■A new recording medium that can use the above-mentioned new recording and reproducing method has been disclosed.

■The energy required for reproduction is small and the power consumption is low.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically showing a recording/reproducing apparatus of the present invention.

Claims (15)

[Claims] (1) Probe electrode, semiconductor with electric memory effect,
A playback device comprising: voltage application means for applying a voltage that does not exceed a threshold voltage that causes an electric memory effect; and reading means for reading changes in the amount of current flowing through the semiconductor. (2) The reproducing device according to claim 1, wherein the semiconductor is arranged between the probe electrode and a counter electrode arranged opposite to the probe electrode. (3) The reproducing device according to claim 1, wherein the semiconductor is an amorphous semiconductor formed of a chalcogenide. (4) the chalcogenide contains at least one element selected from the group III, IV, V and VI elements of the periodic table; Se;
The regeneration device according to claim 3, which contains at least one element selected from Te and As. (5) The reproducing device according to claim 1, wherein the semiconductor is a silicon film. (6) The reproducing device according to claim 5, wherein the silicon film is an amorphous silicon film. (7) Claim 6, wherein the amorphous silicon is a p^+/n/i laminate or an n^+/p/i laminate.
Reproduction device as described in section. (8) The reproducing device according to claim 1, wherein the semiconductor is an organic semiconductor. (9) The reproducing device according to claim 8, wherein the organic semiconductor is a compound containing an electroreceptor and a metal. (10) the electron acceptor is tetracyanoquinodimethane;
The regeneration device according to claim 9, which is tetracyanoethylene, tetrafluorotetracyanoquinodimethane, or tetracyanonaphthoquinodimethane. (11) The reproduction device according to claim 1, further comprising an XY scanning drive device for the probe electrode. (12) Claim 1 comprising means for finely controlling the relative position of the probe electrode and the semiconductor in three dimensions.
Reproduction device as described in section. (13) The reproducing device according to claim 1, wherein the reading means has a servo circuit. (14) A regeneration method characterized by applying a voltage that does not exceed a threshold voltage that causes an electric memory effect from a probe electrode to a semiconductor having an electric memory effect, and reading changes in the amount of current flowing through the semiconductor. (15) The regeneration method according to claim 14, wherein a voltage not exceeding a threshold voltage that causes an electric memory effect is applied to the semiconductor from a probe electrode and a counter electrode.