JPH02201753A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To enable the recording/reproducing of high density in order of 10nm by using a recording medium having a recording layer consisting of amorphous Si containing hydrogen and performing a recording by approaching a probe electrode to the recording medium. CONSTITUTION:The recording medium 2 having the recording layer consisting of amorphous Si containing hydrogen and capable of being locally changed in its surface form by impressing an electric field is used, and the probe electrode 1 is moved under the state of controlling a distance with the recording medium 2 by XY direction coarse moving and fine moving mechanisms 8 and 7 until a specified recording position, and on arrival in the recording position, the probe electrode 1 is given a pulse voltage for write by a pulse voltage circuit 11 for generating the pulse voltage corresponding to a recording signal 12. An excess current flows in the recording position by impressing this pulse voltage, and hence hydrogen is locally desorpted from the recording medium 2 so that the surface form is changed to perform the recording. By this method, the recording and reproducing are feasible on the recording medium 2 with a recording unit in order of 10nm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a large-capacity, high-density recording/reproducing device having a recording density on the order of nanometers.

[Prior Art] In recent years, the use of memory materials has become the core of the electronics industry, such as computers and related equipment, video disks, digital audio disks, etc., and the development of these materials has been extremely active. The performance required of memory materials varies depending on the application, but generally high density and large storage capacity are required.

Until now, semiconductor memory and magnetic memory were mainly made of magnetic materials and semiconductors, but in recent years, optical memory has been developed with the advancement of laser technology. , high-density recording and reproduction on the order of pm has become possible.

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 through evaporation or melting using the heat of laser light, or by changing the reflectance. There is.

Furthermore, as video information technology is rapidly progressing, there is an increasing need for smaller, larger-capacity, and higher-density memories.

[Problem to be solved by the invention] However, in conventional optical memory, since recording and reproducing are performed by converging laser light with an optical system, it is difficult to narrow down the beam diameter to less than the wavelength of light, so light with a wavelength as short as possible is used. Improvements such as these are being made, but there is a drawback that the recording unit is limited to the pm order.

[Means and effects for solving the problems] The present invention provides a recording medium having a recording layer made of hydrogen-containing amorphous Si and whose surface shape changes locally by application of an electric field, and at least one layer facing the recording medium. By providing one probe electrode, a means for applying a voltage to the probe electrode, and a means for controlling the distance between the probe electrode and the recording medium, recording and reproduction can be performed on the recording medium in recording units on the order of several tens to several nanometers. This makes it possible to provide an extremely high-density recording/reproducing device.

Recently, a scanning tunneling microscope (hereinafter abbreviated as STM) that can directly observe the electronic structure of surface atoms of conductors has been developed.
G, Binning et at, He1vet
icaPhysica Acta, 55.726(1
982)] 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 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 utilizes the fact that when a voltage is applied between a metal probe called a probe electrode and a conductive material and the probe is brought close to a distance of about 1r+m, a tunnel current flows. 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 depict 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. At this time, the resolution in the in-plane direction is about 0.1 nm. Therefore, by applying the principle of STH, it is possible to sufficiently perform high-density recording and reproduction on the order of nm meters.

The recording and reproducing method used in this case is electron beam.

A method of recording by changing the surface state of a recording medium using electromagnetic waves such as ion beams, X-rays, and light, and reproducing it with STM, and a method of recording with STM, and materials that have a memory effect in voltage and current switching characteristics, such as chalcogenide, as a recording medium. A method has been proposed in which recording and reproduction are performed using STM using a thin film layer of a similar type or a thin film layer of a π-electron organic compound.

Furthermore, an attempt has been made to apply a voltage that causes field emission to the probe electrode of the STH to locally melt the sample surface of the Rh-Zr alloy to form a cone-shaped protrusion. [0,5tafer et a+,.

Appl, Pbys, I, ett, 51(4),
27 July 2i987] By recording using STH probe electrodes as described above, recording units on the order of several tens to several nanometers can be obtained, and a recording/reproducing device with higher density than an optical memory can be realized.

Hereinafter, the present invention will be explained in more detail using the drawings.

FIG. 1(a) is a block configuration diagram showing a recording/reproducing apparatus of the present invention, and FIG. 1(b) is a configuration diagram of a recording medium.

Reference numeral 1 in FIG. 1(a) is a probe electrode, which is used for recording and reproduction, and its tip is made sharp by mechanical grinding, electrolytic polishing, etc. in order to improve the resolution of recording and reproduction. In the present invention, a tungsten needle whose tip has been electrolytically polished is used, and the material of the probe electrode is Pt-1r, Pt
etc., and the processing method is not limited to this in any way.

A recording medium 2 is formed on a substrate 3 and includes a recording layer made of hydrogen-containing amorphous Si and a conductive underlayer.

In the recording layer made of hydrogen-containing amorphous Si, the hydrogen content of the amorphous Si is preferably in the range of 5 atomic % to 50 atomic %, particularly in the range of 10 atomic % to 30 atomic %.

In the present invention, atomic % indicates the ratio of the number of atoms of contained elements. This is because recording sensitivity deteriorates when the hydrogen content is 5 at% without grooves, and when the hydrogen content exceeds 50 at%, a recording layer of hydrogen-containing amorphous Si is stably formed. This is because it becomes difficult to do so. Also,
Any conductive layer is preferable for the base layer, for example, metals such as Au, Cu, Al, etc. are selected, and the formation method is a vacuum evaporation method.

Any method that can uniformly form the base layer, such as sputtering, may be used.

4 is a probe current amplifier that detects the tunnel current flowing between the probe electrode 1 and the recording medium 2; 5 is the Z direction in the figure, that is, the Z direction that controls the movement of the probe electrode 1 in a direction perpendicular to the surface of the recording medium 2; In the servo circuit, 6 is a Z-direction fine movement mechanism comprised of a piezoelectric element or the like that drives the probe electrode 1 in the Z-direction.

The Z-direction servo circuit 5 drives the Z-direction fine movement mechanism 6 so as to keep the probe current detected by the probe current amplifier 4 constant, and controls the distance between the probe electrode 1 and the recording medium 2. 7 is an XY direction fine movement mechanism composed of a piezoelectric element etc. that controls the movement of the probe electrode l in the X and Y directions in the figure, that is, in a direction parallel to the surface of the recording medium 2, and 8 is an XY direction coarse movement mechanism. Driven by piezoelectric elements or electromagnetic means. These fine and coarse movement mechanisms 7 and 8 can be controlled by a control circuit (not shown) to move the probe electrode 1 to any position in the recording area of the recording medium 2.

Next, the recording/playback method will be explained. First, regarding the recording method, in FIG. 1(a), the recording signal 1 to be recorded is
2 and the recording position on the recording medium 2 are sent from a control circuit (not shown). At that time, the probe electrode l moves to the designated recording position with the distance from the recording medium 2 controlled by the XY direction coarse movement and fine movement mechanisms 7 and 8, and when it reaches the recording position, it corresponds to the recording signal 12. A pulse voltage circuit 11 that generates a pulse voltage applies a pulse voltage for writing to the probe electrode l. By applying this pulse voltage, an excessive current flows to the recording position, hydrogen is locally desorbed from the recording medium, the surface shape changes, and recording is performed.

When a pulse voltage is applied at this time, the probe current changes rapidly, so the Z-direction servo circuit 5 controls the hold circuit to be turned on so that the output voltage remains constant during that time. Therefore, even during recording, the distance between the probe electrode 1 and the recording medium 2 does not change significantly, allowing stable recording.

Next, regarding the reproducing method, the recording position to be reproduced is instructed from a control circuit (not shown), and the probe electrode 1 is instructed as in the case of recording.
is moved to a designated position by the XY direction coarse movement and fine movement mechanisms 7 and 8, and starts playback. At this time, the probe electrode 1 traces the uneven surface caused by recording on the recording medium 2 by the Z-direction servo circuit 5 so that the tunnel current is constant, so that the control given from the Z-direction servo circuit 5 to the Z-direction fine movement mechanism 6 is controlled. The signal corresponds to the irregularities on the surface of the recording medium 2, and a reproduced signal 10 is obtained by processing the control signal by waveform shaping etc. in a reproduced signal demodulation circuit 9.

FIG. 2 shows the recorded shape produced on the recording medium 2 of the present invention, and the recorded shape depends on the magnitude of the pulse voltage applied to the probe electrode l during recording, the application time, and the material of the recording medium 2. It will be different.

That is, at the tip of the probe electrode l, when a recording pulse voltage is applied, a much larger current flows due to field emission than a normal tunnel current, several pA to several nA, and locally heats the surface of the recording medium 2. do. Therefore, the surface of the recording medium 2 locally melts or desorbs hydrogen as shown in FIG. , as shown in FIG. 2(b), there are cases where the four parts 21 are formed by local evaporation, and the control of the shape can be optimized by changing the recording conditions. The size of the uneven shape can be formed to have a diameter of several tens of nanometers to several rams, making it possible to perform extremely high-density recording and reproduction.

Hereinafter, it will be explained in more detail using Examples.

[Example] Example 1 A recording medium 2 was formed in which a base layer made of Au and a recording layer made of amorphous Si containing 30 atomic % of hydrogen were laminated on a glass substrate 3 according to the procedure shown below.

(Fig. 1(b)) First, the glass substrate 3 is heated using a vacuum evaporation method (resistance heating method).
An Au underlayer with a thickness of 1000 Å was formed thereon.

Next, an amorphous Si recording layer containing 30% hydrogen and having a thickness of 300 A was laminated on the Au underlayer by plasma GVD. The formation of this recording layer requires a substrate temperature of 200°C.
Keep SiH4,! 1-H2 mixed gas 209CG
While flowing into the M film forming equipment, the pressure inside the equipment is 0.1 torr.
, under the condition of power 50W.

The recording medium created in the manner described above is shown in Figure 1 (a).
) When we conducted a recording/playback experiment using the recording/playback device shown in Figure 1, we found that the peak value was 5 ports and the pulse width was 1 pse.
By applying a pulse voltage of
It turns out that playback is possible. Furthermore, when recording was performed under the same conditions while irradiating the recording medium with light, the stability of recording and reproduction was further improved.

Examples 2 to 4 and Comparative Examples Completely the same as Example 1 except that the hydrogen-containing amorphous Si recording layer had a different hydrogen content of 5 at%, 10 at%, and 50 at%, respectively. Created a recording medium. The hydrogen content was varied mainly by changing the substrate temperature, and also by changing the power, gas flow rate, etc. In addition, as a comparative example, amorphous Si having a hydrogen content of 3 at % was also formed. Note that an amorphous Si layer having a hydrogen content of more than 50 atomic % could not be stably obtained even when various film forming conditions were changed.

When the recording medium prepared as described above was subjected to recording/reproducing experiments under the same conditions as in Example 1, the results shown in Table 1 were obtained. rOJ in the table indicates that stable recording/reproduction was possible under the same recording conditions as in Example 1, "Δ" indicates that recording/reproduction was possible, and "x" indicates that recording/reproduction was extremely unstable. represents something.

As is clear from Table 1, very high density recording and reproduction is possible when the hydrogen content of the hydrogen-containing amorphous Si recording layer is in the range of 5 at% to 50 at%. It has been found that more stable recording and reproduction can be achieved when the content is in the range of 10 at % to 30 at %.

By tracing the surface and controlling the recording/reproduction, very high density recording/reproduction on the order of 10 nm can be achieved.
Playback is now possible.

[Brief explanation of the drawing]

FIG. 1(a) is a block configuration diagram showing a recording/reproducing apparatus of the present invention, and FIG. 1(b) is a configuration diagram of a recording medium. FIG. 2 shows the recorded shape produced on the recording medium of the present invention.

Claims (4)

[Claims] (1) A recording medium having a recording layer made of amorphous Si containing hydrogen; at least one probe electrode facing the recording medium; means for applying a voltage to the probe electrode; providing means for controlling the distance of the medium, applying an electric field between the recording medium and the probe electrode;
A recording/reproducing device characterized in that recording is performed by locally changing the surface shape. (2) The recording/reproducing apparatus according to claim (1), wherein the recording medium comprises a recording layer whose surface shape locally changes upon application of an electric field and a conductive underlayer. (3) The recording/reproducing device according to claim (1), wherein the hydrogen content of the amorphous Si is 5 atomic % or more and 50 atomic % or less. (4) The recording/reproducing device according to claim (1), wherein the hydrogen content of the amorphous Si is 10 atomic % or more and 30 atomic % or less.