JPH04168641A - Information reading and/or input device - Google Patents

Abstract

PURPOSE:To prevent collision between a probe electrode and an object and S/N ratio and environmental resistance to be improved by outputting a signal for controlling a probe-drive means of different input/output characteristics according to information obtained from an interval control means which is detected by a detection means. CONSTITUTION:This device is provided with a current amplifier circuit 101 which detects current flowing between a recording medium 112 and a probe electrode 111 and then converts it into voltage signal for output and a piezo element 113 for driving the probe electrode 111 to control distance between the recording medium 112 and the probe electrode 111. Also, a voltage signal which is output from the current amplifier circuit 101 and a specified threshold voltage are compared and an interval control circuit 100 for outputting signal to control drive of the piezo element 113 using different control variables according to the level relationship, thus preventing collision between the probe and an object and obtaining a recording/reproduction device which has an improved S/N ratio and has an improved environmental resistance which is not affected by smear etc. which is adhered on the surface of the object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning tunneling microscope, etc., and an information reading and/or input device to which the technology is applied.

[Conventional technology] In recent years, the horizontal resolution is 0.1 nanometer and the vertical resolution is 0.01 nanometer.
Scanning tunneling microscope with nanometers! l(Sca
nnning TunnelingMi crosco
pe; hereinafter abbreviated as STM) was invented. In STM, a voltage is applied between a conductive probe and a conductive material that are brought close to each other within a distance of about 1 nanometer, and the t flowing between the two is applied.
By detecting 'tL, it is possible to obtain various information regarding the surface shape of the conductive material and the state of electron distribution [G, Binning et al.

Phys, Rev. Lett, 49 (1982) 57
]. Therefore, by applying the principle of STM, it is possible to sufficiently perform high-density recording and reproduction on the atomic order (sub-nanometer).

For example, in the recording and reproducing apparatus disclosed in Japanese Patent Application Laid-Open No. 61-80536, writing is performed by removing atomic particles adsorbed to the surface of the medium using an electron beam or the like, and this data is reproduced using STM. Also, USP4,575
, 822, a tunnel current flowing between the recording medium surface and a probe electrode is used to inject charges into a dielectric layer formed on the medium surface and perform recording. Alternatively, a method has been proposed in which recording is performed by physically or magnetically collapsing the medium surface using a laser beam, an electron beam, a particle beam, or the like.

On the other hand, by using a thin film layer of a material that has a memory effect on the switching characteristics of voltage and current, such as a π-electron organic compound or a chalcogen compound, as the recording layer, recording and reproduction can be performed using S.
A method using TM has been proposed [Japanese Unexamined Patent Publication No. 63-16]
No. 1552, JP-A-63-161553.

According to the method of the publication, if the recording bit size is 10 nm, it is possible to record and reproduce a large capacity of 10"bit/am'.

Control of the distance between the probe electrode and the recording medium in such a recording/reproducing apparatus is disclosed in Japanese Patent Laid-Open Nos. 1-53363 and 1-133239.

In such conventional technology, a circuit as shown in the block diagram of FIG. 3411 is used to control the distance between the recording medium and the probe electrode. In this circuit, during probe electrode scanning, the probe electrode 1111 and the recording medium 1
! In order to keep the current flowing between 12 and 12 constant, the offset voltage is compared with the current flowing between the probe electrode and the recording medium, and the error is calculated using a piezo element, etc. It is input to the driving means 1113 for feedback control. During recording, a sample hold circuit 1107 is used to hold the probe voltage while the recording signal (pulse voltage, etc.) is being input.
The output signal to the driving means 1113 is controlled to be kept constant so that the distance between the recording medium 1112 and the recording medium 1112 does not change, and the surface shape and electronic state of the recording medium 1112 are controlled without holding the sample and hold circuit 1107 during playback. The probe electrode 1111 is controlled so as to always follow the fluctuation.

In addition, when using a recording medium whose surface unevenness is negligibly small compared to changes in the electronic state due to recording, or whose shape does not change due to recording operations, it is necessary to use a recording medium as shown in the block diagram of FIG. circuits are used to increase scanning speed. In this circuit, a current flowing between a recording medium 1212 and a probe 1ii 1211 is detected by a current amplifier 1201, and a high-pass circuit 1
202 and a low-pass circuit 1203, the detection signal is divided into a band component of the recording/reproduction signal and an average component of current value fluctuation, so that the average value of the current flowing between the probe electrode 1211 and the recording medium 1212 is constant. A drive signal is output to the distance control mechanism 1213 so that During recording, the drive means 1213 uses the sample hold circuit 1207 to prevent the distance between the probe electrode 1211 and the recording medium 1212 from changing while the recording signal (pulse voltage, etc.) is input to a voltage application circuit (not shown). The sample and hold circuit 1207 is controlled to keep the output signal constant during playback, and the probe electrode 1 is adjusted to the average value of the fluctuations in the surface shape and electronic state of the recording medium 1212.
211 always follows.

[Problem to be solved by the invention] However, the recording medium and probe t8 of the above-mentioned conventional example
In the control where the current flowing during the period i is constant, the response of the feedback system must be accelerated in order to avoid collision between the probe electrode and the recording medium during scanning of the probe electrode, but this increases the overshoot and the first
As shown in FIG. 3, the movement of the probe electrode 1311 becomes unstable and the S/N ratio deteriorates. If non-conductive substances such as dirt (organic matter) are attached or adsorbed onto the surface of the recording medium, the probe electrode collides with the recording medium because no current flows between the recording medium and the probe electrode.

In addition, when controlling the average value of the current change flowing between the recording medium and the probe electrode to be constant, when a medium whose surface is uneven due to recording is used, and when the surface of the recording medium is uneven due to recording, If there is a structural change due to scratches or uneven formation of the underlying electrode substrate that is not negligible compared to the change in the conductive ring that occurs, collision between the probe electrode and the recording medium is unavoidable.

As described above, in conventional recording and/or reproducing devices, damage to the probe electrode or unstable positional fluctuation of the probe electrode causes deterioration of the S/N ratio, deterioration of the recording/reproduction error rate,
In some cases, the life of the probe electrode may be shortened and the environment in which the device can be used may be limited.

An object of the present invention is to apply the above-mentioned prior art, and in view of such prior art, it is an object of the present invention to stably control the distance between a probe and an object in an information reading and/or input device, thereby improving the distance between the probe electrode and the object. Preventing collisions between objects,
The objective is to improve S/N and environmental resistance.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a probe disposed facing an object, a detection means for detecting information from the object via the probe, and a distance between the probe and the object. In an information reading and/or input device, the information reading and/or input device includes a probe drive means for driving the probe to adjust the probe, and an interval control means for outputting a signal for controlling the probe drive means based on information detected by the detection means, The interval control means outputs signals for controlling the probe driving means having different input/output characteristics depending on the information detected by the detection means.

The interval control means, for example, when the intensity of the signal according to the information detected by the detection means exceeds the intensity of the threshold signal,
A device that limits the output of the signal for controlling the probe drive means to a certain level, or a probe drive device that uses different amplification degrees and time constants depending on the comparison result between the signal corresponding to the information detected by the detection means and the threshold signal. It can be configured to output a signal for controlling. For example, a peak hold circuit can be used to output signals for controlling the probe driving means with different time constants.

[Operation] In this configuration, control signals are generated with different input/output characteristics (control variables) according to information obtained from the object via the probe, and the probe driving means is controlled thereby. With respect to the object-probe electrode distance, when the probe driving means is driven in the direction in which the probe and the object approach, and when it is driven in the direction in which the probe and the object move away,
Conventionally, control signals were generated with linear and constant output characteristics, but in the present invention, for example, the input and output characteristics are different between the two.

Therefore, by appropriately setting these input/output characteristics, it is possible to limit the amount of movement of the probe toward the object, speed up collision avoidance, and stabilize the control of the distance between the probe and the recording medium. Collision between the probe and the object is avoided even if there is dirt, scratches, or surface irregularities due to uneven manufacturing of the recording medium. As a result, the durability of the probe electrode and the environmental resistance of the device are improved, and stable information reading and/or input can be performed.

[Example code] Hereinafter, the present invention will be explained in detail using the drawings.

Figure 1 is a block diagram of a control system for controlling the distance between the probe electrode and the recording medium in the recording/reproducing apparatus according to the first embodiment of the present invention. This control system controls the recording medium 11
a current amplifier circuit 101 that detects a current flowing between the probe electrode 111 and the probe electrode 111, converts it into a voltage signal, and outputs the voltage signal;
To control the distance between the recording medium 112 and the probe electrode 11, the piezo element 113 that drives the probe electrode 111 compares the voltage signal output by the current amplifier circuit 101 with a predetermined threshold voltage, and determines its magnitude. The interval control circuit 100 outputs a signal for controlling the drive of the piezo element 113 using different control variables depending on the relationship.

The interval control circuit 100 includes a bypass filter 102, a low-pass filter 103, and a signal processing circuit i04 connected to the current amplifier circuit 101, and a phase compensation circuit 105 and a phase compensation circuit 105 connected to the output side of the low-pass filter 103. an error amplifier 106 that provides a predetermined offset voltage to the output of the error amplifier 106;
an amplifier circuit 109 connected to the output side of the bypass filter 102, an output limiting circuit 110 connected to the output side of the bypass filter 102, and an amplifier circuit 108 connected to the output side of the output limiting circuit 110.
, an adder 11 that adds the outputs of the amplifier circuits 108 and 109.
4. A sample and hold circuit 107 connected to the pressure side of the adder 114 is provided. The output limiting circuit 110 has input/output characteristics as shown in FIG.

In this configuration, the voltage signal output from the current amplifier circuit 101 is input to the bypass filter 102, the low-pass filter 103, and the signal processing circuit 104, respectively. The output of the low-pass filter 103 is output from the phase compensation circuit 1.
05, an offset voltage is applied to the error amplifier 106, and after being amplified by the amplifier circuit 109, it is input to the adder 114. Bypass filter 10
The output of 1i!2 is input to the output limiting circuit 110, and the output is amplified by the amplifier circuit 108 and added 1i! 114. In adder 114, amplifier 108 and amplifier 1
09 are added, and the added output is sent to the piezo element 113 in the distance direction between the recording medium 112 and the probe electrode 111 (hereinafter referred to as
(referred to as the Z-axis direction).

As a result, the probe @8i111 linearly follows low-frequency signal components such as the tilt of the substrate of the recording medium 112 except during recording, and also detects scratches and scratches with frequency components of the same or higher frequency as the recorded signal. Due to the input/output characteristics of the output limiting circuit 110, the signal changes due to dust etc.
When the signal changes in the direction in which the probe electrode 111 moves away from the recording medium 112, the probe electrode 111 follows the signal change to avoid collision between the probe electrode 111 and the recording medium 112, and when the signal changes in the direction in which the probe electrode 111 approaches the recording medium 112, the probe electrode 111 follows the signal change within a certain limit.
movement is restricted and collisions are avoided. Of course, when the output of the output limiting circuit 110 has a positive sign, the probe electrode 111
is designed so that it approaches the recording medium 112.

As shown in FIG. 10, the output limiting circuit 110 can be constructed very easily by using an operational amplifier OP and two Zener diodes D and 2, and the amplification degree is determined by resistors R and R2. This can be achieved by simply selecting the characteristics of D1 and D2. This has the advantage that the cost increase due to adding this circuit is small.

Embodiment 2 FIG. 3 is a block diagram of a control system for controlling the distance between a probe electrode and a recording medium in a recording/reproducing apparatus according to a second embodiment of the present invention.

In this case, the recording medium 112 detected by the current amplifier circuit 101 and converted into a voltage signal and the probe voltage 8i11
The signal of the current flowing between the A/D conversion circuit 31 and
4 is converted into a digital signal and input to the digital signal processor 315. Then, for the recording signal and signal changes due to scratches, dirt, etc. having frequency components of the same order of magnitude or higher, the signal is calculated and output within the pass band so as to have input/output characteristics as shown in Fig. 4. The output is converted into an analog signal by a D/A conversion circuit 316. The signal is amplified by an amplifier 317 and output to an input that controls the Z-axis direction of the piezo element 113 that three-dimensionally controls the probe electrode 111. As a result, the probe electrode 111 has a high gain in the direction away from the recording medium 112, so it responds quickly, and in the direction where the probe electrode 111 approaches the recording medium +12, the gain is low, so the amount of movement is limited, and the probe electrode 111 can record. It does not collide with the medium 112.

Note that the circuit configuration shown in this embodiment itself does not limit the present invention in any way, and the characteristics shown in FIG. On the other hand, it is also possible to adopt a characteristic in which the amplification degree of the output signal changes nonlinearly.

If the input/output characteristics of the digital signal processor 315 in the pass band for the recording signal and signal changes due to scratches, dust, etc. having frequency components of the same order of magnitude or higher are as shown in FIG. There is no signal saturation point, and the inflection point of the amplification degree is moved to a place where the input signal is small to lower the rate of change of the amplification degree, so there is no residual vibration of the actuator at the inflection point, and the movement is smooth. /N
It has the advantage of being high.

Furthermore, when the characteristics shown in FIG. 5 are provided, there is an advantage that the system is stable and the S/N ratio is high because the response is small when the input signal is small.

Embodiment 3 FIG. 6 is a block diagram showing the configuration of a recording/reproducing apparatus according to a third embodiment of the present invention. 8 and 9 show examples of waveforms of each signal line of the recording/reproducing apparatus of FIG. 6 during reproduction and recording, respectively.

In the wooden example, the probe electrode 111 and the recording medium surface 6
In the circuit that controls the gap between
For this purpose, it is characterized by the use of a peak hold circuit. As a result, as shown by the locus 723 of the tip of the probe electrode 111 in FIG. Speed increases. Therefore, even if there is a steep convex part on the surface of the recording medium 112, the probe electrode 111 can be avoided with a fast time constant, and when the probe electrode 111 is off the convex part of the data hit, it can be moved onto the surface of the recording medium 112 with a slow time constant. approach. Further, since the probe electrode 111 can be suppressed from following the recording medium 112 between recording bits, there is no unnecessary movement of the probe electrode 111.

In FIG. 6, 619 is a substrate of a recording medium, 620 is a lower electrode layer provided on the substrate 619, 621 is a recording layer formed on the lower electrode layer 620, and 111 is a probe electrode. A cylindrical PZT actuator 113 is used to scan the probe electrode 111 along a data row on the recording layer 621, and can move up to 2 μm in each of the X, Y, and Z directions. The data string on the recording layer 621 is composed of recording bits 722 as shown in FIG.

Probe electrode 111 is connected to current amplifier 6o1.

The output of the current amplifier 601 is sent to the sample hold circuit 607
is input. The output signal a of the sample hold circuit is input to a peak hold circuit 614 and a high pass filter 602, respectively. The output of peak hold circuit 614 is connected to error amplifier 606 and low pass filter 603. The output of the error amplifier 606 is a cylindrical PZT113
is connected to the ΔZ (Z direction) drive electrode of.

On the other hand, the output of the low-pass filter 603 is the attenuator V Rr
The signal is input to the frequency parator 615 through the filter. The output d of high-pass filter 602 is connected to the other input of comparator 615. Further, the output e of the comparator 615 is input to a data demodulator of a data modulation/demodulation section 617. The data modulation output of the data modulation/demodulation section 617 is connected to a pulse generator 616, and the output of the pulse generator 616 is combined with the DC bias voltage VBI and connected to the recording medium electrode (lower electrode layer 620).

The distance between the probe electrode 111 and the surface of the recording medium 112 is controlled by using an error amplifier 606 to generate a reference voltage VB2 using a signal that peak-holds the value of the tunnel current flowing between them.
This is done by driving the cylindrical PZT by Δ2.

By this control, the probe electrode 111 scans so as to envelop the convex part of the data string or the part with the highest electronic state.

Next, the operation during playback is shown in the eighth section, which represents the state of each signal.
This will be explained using the timing chart shown in the figure.

The tunnel current flowing through the probe electrode 111 is detected by a current amplifier 601, converted to a voltage value, amplified, and then sampled and held by a sample and hold circuit 607. The sample hold circuit 607 is in a through state during reproduction.

The sample-and-hold output a is passed through a high-pass filter 60
2, a high frequency component, that is, a data information component d is extracted, and compared with an appropriately attenuated envelope signal C of the data string in a comparator 615, thereby obtaining binarized data e. Here, the envelope signal C is passed through a low-pass filter 60 with a peak hold output.
3. The obtained binarized data e is
The data is demodulated in a data modulation/demodulation section 617 to obtain reproduction information.

Next, the operation during recording will be explained using the timing chart of FIG.

Writing is performed by holding the sample hold control signal f from the probe electrode control unit 618 in synchronization with the data write clock, and generating a write pulse g from the pulse generator 616.

Note that the circuit system of this embodiment does not limit the present invention in any way;
Various methods can be used, such as using a logarithmic conversion amplifier in between, configuring a circuit system with a digital signal processor, and a connector.

According to this embodiment, the movement of the probe electrode is stably controlled even when the scanning speed is increased, so that the transfer speed of recording and reproduction can be improved.

[Type 1] Any material can be used as the recording layer used in the recording medium as long as information written in the recording layer can be detected by a tunnel current flowing between the probe and the recording layer. An example is HOPG (H4ghly-Oriente), which records by forming unevenness on the surface.
d-Pyrolytic-Graphite) 1 Open substrate, Si wafer, vacuum-deposited or epitaxially grown metal thin film such as Au, Ag, Pt, Mo, Cu, Rh
Examples include glass metals such as 25Zr7s and CO2STbas. Examples of those that record based on the electronic state of the surface include amorphous Si, a thin film layer of a π-electron organic compound, and a chalcogen compound.

In addition, any shape of the recording medium and material of the substrate can be used. For example, the shape of the substrate may be a card shape, a tape shape, a disk shape, or the like. Materials include HOPG, interfold crystal substrates such as mica, and Si.

Examples include surface-polished crystal substrates such as sapphire and MgO, substrates such as fused silica, and Corning No. 7059 glass. Materials that can also be used as substrate materials for tape-shaped media include polycarbonate, acrylic, PEEK, PET, and nylon.

In addition to the recording/reproducing apparatus, the present invention is also applicable to STM. Furthermore, it goes without saying that each of the above-mentioned devices may be a device that only performs recording or reproduction.

[Effects of the Invention] As explained above, according to the present invention, the collision between the probe and the object is prevented, and the probe electrode and the object are not damaged, so the S/N is good and dirt etc. attached to the object surface is prevented. Therefore, it is possible to provide a recording and/or reproducing device that is not affected by the environment and has excellent environmental resistance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control system for controlling the distance between a probe electrode and a recording medium in a recording/reproducing apparatus according to a first embodiment of the present invention, and FIG. 2 is an output of the apparatus shown in FIG. 1. FIG. 3 is an input/output characteristic diagram of the limiting circuit, and FIG. 5 is an input/output characteristic diagram of the signal f acid component in the apparatus shown in FIG. 3, and FIG. 6 is a block diagram showing the configuration of a recording/reproducing apparatus according to a third embodiment of the present invention. 6 is a schematic diagram showing the movement of the probe electrode on the recording medium in the device shown in FIG. 6, FIG. 8 is a timing chart of each signal line during reproduction in the device shown in FIG. 6, and FIG. 10 is a circuit diagram showing a configuration example of the output limiting circuit in the device shown in FIG. 1. FIG. 11 is a probe electrode and recording medium according to the conventional example. FIG. 12 is a block diagram of the circuit system used to control the probe electrode and recording medium according to another conventional example, and FIG. FIG. 2 is a schematic diagram showing the movement of a probe electrode on a recording medium. 101.601: Current amplifier, 102: Bypass filter, 103: Low pass filter, 104: Signal processing circuit, 1o5: Phase compensation circuit, 106.606 + error amplifier, 107,607・Sample hold circuit, 108,
109.317: Amplifier, 2,110: Output limiting circuit,
111 nib lobe electrode, 112: recording medium, 113, 6
13: piezo element, 314 two A/D converters, 315: digital signal processor, 316: D/A converter, 614: peak hold circuit, 603: low pass filter, 615: comparator, 602; high pass Type filter, 616: Data writing pulse generator, 618
Nibrob electrode control section, 417: Data modulation/demodulation section, 71
9: Substrate of medium, 720: Lower electrode layer, 721: Recording layer, 722. Recording bit, 723 nib lobe electrode trajectory. Fig. 7 Fig. 8 = Fu・O-fu-shu-betsukainichi 1st ○

Claims (6)

[Claims] (1) A probe placed opposite the object, a detection means for detecting information from the object via the probe, a probe drive means for driving the probe to adjust the distance between the probe and the object, and a detection means In the information reading and/or input device, the interval control means outputs a signal for controlling the probe driving means based on the information detected by the detection means, and the interval control means has different values depending on the information detected by the detection means. An information reading and/or input device characterized in that it has input/output characteristics and outputs a signal for controlling probe driving means. (2) The interval control means limits the output of the signal for controlling the probe drive means to a certain level when the intensity of the signal corresponding to the information detected by the detection means exceeds the intensity of the threshold signal. Information reading and/or input device according to claim 1, characterized in that: (3) The interval control means outputs a signal for controlling the probe driving means with different amplification degrees depending on the comparison result between the signal corresponding to the information detected by the detection means and the threshold signal. The information reading and/or input device according to claim 1. (4) The interval control means outputs a signal for controlling the probe driving means with a different time constant depending on the comparison result between the signal corresponding to the information detected by the detection means and the threshold signal. The information reading and/or input device according to claim 1. (5) The information reading and/or input device according to claim 4, wherein the interval control means has a peak hold circuit for outputting signals for controlling the probe driving means with different time constants. (6) A probe disposed facing the object, a detection means for detecting information from the object via the probe, a probe drive means for driving the probe to adjust the distance between the probe and the object, and a detection means. In the information reading and/or input device, the distance control means controls the movement of the probe in the direction in which the probe approaches the object and the movement in the direction in which the probe moves away from the object. An information reading and/or input device characterized in that the probe driving means is controlled to slow down or to further restrict the movement of the probe.