Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Utility Patent
1998-05-29
2001-01-02
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C257S741000, C257S750000, C257S761000, C257S762000, C257S763000, C257S764000, C257S765000, C257S766000, C257S768000, C257S769000, C257S770000, C360S131000, C428S630000, C428S651000, C428S660000, C428S669000, C428S672000, C428S674000, C428S686000, C428S687000, C428S692100, C428S690000, C428S900000
Utility Patent
active
06168873
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrode substrate and a recording medium. It also relates to a method of manufacturing such an electrode substrate and a recording medium.
2. Related Background Art
In recent years, massive efforts have been devoted to developing new materials to be used for memories because such materials are deemed to play a vital role in the electronic industry in the area of manufacturing computers, computer-related devices and audio-visual devices such as video discs.
While properties that memory materials are required to have may vary depending on the application, they normally include
(1) a highly dense and large memory capacity,
(2) a high response speed for data recording/reproduction,
(3) a low power consumption rate and
(4) a high productivity at low cost.
While semiconductor memories and magnetic memories made of a magnetic or semiconductor materials have been in the main stream, low cost and high density recording media such as optical memories using organic thin film made of an organic pigment or a photopolymer are currently on the scene as a result of the remarkable development in the field of laser technologies.
Meanwhile, thanks to the recent development of scanning tunneling microscopes (hereinafter referred to as STM) that allow a direct observation of the electronic structure of surface atoms of a conductor material [G. Binnig et al., Phys. Rev. Lett., 49, 57 (1982)], it is now possible to observe a real spatial image of a specimen with an enhanced level of resolution regardless if the specimen is crystalline or non-crystalline. An STM provides an advantage of low power consumption rate that makes the specimen free from power-related damages in addition to the fact that it can be operated in the atmosphere to observe various specimens and hence provides a wide variety of applications.
The STM utilizes the fact that a tunneling current flows between the metal probe of the STM and the electroconductive specimen when they are brought close to each other until they are separated only by about lnm, while applying a voltage to them.
The tunneling current is highly sensitive to changes in the distance separating them. Therefore, various information can be obtained on the real spatial arrangement of the entire electron cloud by operating the scanning probe so as to maintain the tunneling current at a constant level. The intraplanar resolution of an STM is typically about 0.1 nm.
Thus, an ultra-high density data recording/reproduction on the order of the size of an atom (on the order of sub-nanometer) will be possible on the basis of the principle of STM.
For instance, a data recording/reproducing apparatus disclosed in Japanese Patent Application Laid-Open No. 61-80536 utilizes an electron beam to remove particles of atoms adsorbed on the surface of a recording medium in order to write data onto and read data from it by means of an STM.
Methods have been proposed for recording/reproducing data on a material exhibiting memory effects for voltage-current switching characteristics such as a thin film of a &pgr; electron type organic compound or a chalcogen compound by means of an STM (see, inter alia, Japanese Patent Applications Laid-Open Nos. 63-161552 and 63-161553).
With any of such methods, it is possible to record data as densely as 10
12
bits/cm
2
when the recording bit size is 10 nm.
FIG. 1
of the accompanying drawings schematically illustrates the configuration of a known information processing apparatus utilizing the STM technology. This apparatus will be described briefly below.
Referring to
FIG. 1
, there are shown a substrate
11
, a metal electrode layer
12
and a recording layer
13
. There are also shown an XY stage
201
, a probe
202
, a probe support member
203
, a linear actuator
204
for driving the probe in the direction of the Z-axis and a pulse voltage circuit
207
.
Reference numeral
301
denotes an amplifier for detecting the tunneling current flowing from the probe
202
to the electrode layer
12
by way of the recording layer
13
. Reference numeral
302
denotes a logarithmic compressor for converting the change in the tunneling current into a value proportional to the gap between the probe
202
and the recording layer
13
. Reference numeral
303
denotes a low-pass filter for extracting any surface unevenness components of the recording layer
13
.
Otherwise, there are shown an error amplifier
304
for detecting the difference between the reference voltage Vref and the output of the low-pass filter
303
, a driver
305
for driving the Z-axis linear actuator
204
and a drive circuit
306
for positionally controlling the XY stage
201
by means of X- and Y-axis linear actuators
205
and
206
. Reference numeral
307
denotes a high-pass filter for separating data components.
FIG. 2
of the accompanying drawings schematically illustrates a probe
202
to be used with a known recording medium.
Referring now to
FIG. 2
, there are shown data bits
401
stored in the recording layer
13
and crystal grains
402
produced when the electrode layer
12
is formed on the substrate
11
. The crystal grains have a size of about 30 to 50 nm if the electrode layer
12
is formed by means of commonly used techniques such as vacuum evaporation or sputtering.
The gap between the probe
202
and the recording layer
13
can be held constant by the circuit shown in FIG.
1
. More specifically, the tunneling current flowing between the probe
202
and the recording layer
13
is detected and, after passing through the logarithmic compressor
302
and the low-pass filter
303
, compared with a reference voltage. Then, the Z-axis linear actuator
204
supporting the probe
202
is driven to reduce the difference between the detected value and the reference value to zero and thereby maintain the distance between the probe
202
and the recording layer
13
to a constant value.
Then, the XY stage
201
is driven to make the probe
202
move along the surface of the recording medium so that the data stored in the recording layer
13
can be detected at point b by separating the high frequency component of the signal obtained at point a in FIG.
1
.
FIG. 3
of the accompanying drawings is a graph showing the signal intensity spectrum relative to the frequency of the signal obtained at point a in FIG.
1
. Note that the signal portion below f
0
represents the mild undulations of the surface of the recording medium due to warps and distortions of the substrate
11
and the part of the signal at and around f
1
represents the surface roughness of the recording layer
13
mainly due to crystal grains
402
produced at the time of forming the electrode material and the signal portion at f
2
represents the carrier wave component of the recorded data. Reference numeral
403
denotes the data signal band.
Reference symbol f
3
denotes the part of the signal for which the atomic and molecular arrangement of the recording layer
13
is responsible.
However, a known recording medium having a configuration as described above is typically accompanied by the following problems.
For a high density recording to be done by exploiting the high resolution of an STM, the data signal band
403
should be found between f
1
and f
3
.
Then, a high-pass filter
307
relevant to cut-off frequency fc is used to separate the data component of the signal.
However, the data signal band
403
lies on the outskirt of the signal component represented by f
1
mainly due to the fact that crystal grains
402
of the electrode layer
12
are responsible for the signal component f
1
and the size of the crystal grains
402
that is about 30 to 50 nm is close to the recorded data size and the bit interval which are about 1 to 10 nm.
A net consequence of this is a low S/N ratio for data reproduction and a high error rate for data reading.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an electrode substrate and a recording medium showing a high S/N ratio and adapted
Ikeda Tsutomu
Kawasaki Takehiko
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Koehler Robert R.
Zimmerman John J.
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