Patent Application
20080205252
This application claims priority from Korean Patent Application No. 10-2007-0018521, filed on Feb. 23, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a ferroelectric information storage medium having a ferroelectric material for storing information and, more particularly, to a ferroelectric information storage medium having a ferroelectric nanodot layer which is an information storage unit and a method of manufacturing the ferroelectric information storage medium.
2. Description of the Related Art
Due to the rapid development of data storage devices such as conventional hard disks and optical disks, information storage media having a recording density of 180 Gbit/inch2 or above have been developed. However, the rapid development of digital techniques requires a further increased capacity of information storage media.
The recording density of a conventional hard disk is limited due to superparamagnetic limitations or diffraction limitations of a laser of an optical disk. Recently, research has been conducted to develop an information storage medium having a recording density of 100 Gbit/inch2 or above by overcoming the diffraction limitation of light using a near-field optic technique. Also, in the case of a hard disk drive (HDD), a recording density of 400 Gbit/inch2 has been demonstrated using discrete track media.
Meanwhile, research has been conducted to manufacture a high capacity information storage medium unlike a conventional information storage medium, using tip-shaped probes that may be viewed using an atomic force microscopy (AFM). Since the tip-shaped probes may be manufactured to a size of a few nm, an atomic level of a surface structure may be observed using the tip-shaped probes. When the tip-shaped probes having the above characteristics are used, information storage media with a tera bit level capacity per square inch may theoretically be manufactured. However, when a tip-shaped probe is used, the conventional ferroelectric thin film may have poor data retention characteristics in the information storage medium due to non-uniformity of the crystal size of polycrystals of the conventional ferroelectric thin film.
To address the above and/or other problems, the present invention provides a ferroelectric information storage medium having an information storage layer formed of uniform size ferroelectric nanodots.
The present invention also provides a method of manufacturing the ferroelectric information storage medium.
According to an aspect of the present invention, there is provided a ferroelectric information storage medium, comprising: a substrate; an electrode formed on the substrate; and ferroelectric nanodots formed on the electrode, wherein the ferroelectric nanodots are separated from each other, and a plurality of the ferroelectric nanodots form a single bit region.
The ferroelectric nanodots may have a diameter of 15 nm or less.
The ferroelectric nanodots may be formed in a monolayer on the electrode.
The ferroelectric nanodots may be formed of at least one selected from PbTiO3, KNbO3, and BiFeO3.
The substrate may be formed of at least one of silicon, glass and aluminium.
The ferroelectric information storage medium may further comprise a protective layer on the ferroelectric nanodots.
The ferroelectric information storage medium may further comprise a lubricating layer on the protective layer.
According to another aspect of the present invention, there is provided a method of manufacturing a ferroelectric information storage medium, comprising: a) forming an electrode on a substrate; b) forming a precursor nanodot layer that comprises a metal material for forming a ferroelectric material on the electrode; c) supplying a reaction gas to the precursor nanodot layer to cause a reaction with precursor nanodots of the precursor nanodot layer to form ferroelectric nanodots; and d) forming the ferroelectric nanodots by annealing the precursor nanodot layer.
The forming of the precursor nanodot layer may comprise coordinating an organic dispersion agent on a surface of each of the precursor nanodots of the precursor nanodot layer.
The precursor nanodot layer may be formed of a plurality of precursor nanodots separated from each other.
The precursor nanodots may have a diameter of 15 nm or less.
The forming of the precursor nanodot layer may comprise thin-filming a solution in which precursor nanodots are dispersed on the electrode.
The thin-filming may be performed using at least one selected from a group consisting of spin coating, dip coating, blade coating, screen printing, chemical self-assembling, Langmuir-Blodgett method, and spray coating.
The solution may comprise the precursor nanodots with a concentration of 0.05 to 1 wt %.
A solvent of the solution may be at least one organic solvent selected from chloroform, dichloromethane, hexane, toluene, ether, acetone, ethanol, pyridine, and tetrahydrofuran.
The precursor nanodot layer may be a monolayer of the precursor nanodots.
The forming of the precursor nanodot layer may further comprise removing the organic dispersion agent.
The removing of the organic dispersion agent may comprise annealing the precursor nanodot layer or O2 plasma processing the precursor nanodot layer.
The forming of the precursor nanodot layer may comprise forming precursor nanodots comprising at least one selected from Ti, Nb, and Fe.
The forming of the ferroelectric nanodots may comprise annealing at a temperature of 400 to 900° C.
The forming of the ferroelectric nanodots may comprise forming the nanodot layer of at least one selected from PbTiO3, KNbO3, and BiFeO3.
The above and other features and aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which:
A ferroelectric information storage medium having a ferroelectric nanodots and a method of manufacturing the ferroelectric information storage medium consistent with the present invention will now be described more fully with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
Referring to
The substrate 10 may be, for example, a silicon substrate which is widely used in the semiconductor industry, and also, may be a glass substrate or alumina substrate.
The electrode 20 may be formed of, for example, Pt, Ir, IrO2, or SrRuO3.
The ferroelectric nanodots 32 are formed of a ferroelectric material, for example, PbTiO3, and are separated from each other as shown in
The ferroelectric nanodots 32 are not limited to PbTiO3 nanodots. That is, a ferroelectric material such as BiFeO3 or KNbO3 may also be used to form the ferroelectric nanodots 32.
The ferroelectric nanodot layer 30 is formed in a monolayer. A protective layer (not shown) may further be formed on the ferroelectric nanodot layer 30. The protective layer may be, for example, a diamond-like carbon (DLC) layer, or another material layer formed of various materials. A lubricating layer (not shown) may further be formed on the protective layer.
A write/read head 40 in
The structure of the information storage medium consistent with the present embodiment may be clearly understood from the following method of manufacturing thereof.
Referring to
Referring to
The thin-filming process may be performed using, for example, one of spin coating, dip coating, blade coating, screen printing, chemical self-assembling, Langmuir-Blodgett method, and spray coating.
The organic dispersion agent 38 is coordinated on surfaces of the precursor nanodots 36, and the precursor nanodots 36 are separated from each other by the organic dispersion agent 38. The precursor nanodots 36 may be formed to a diameter of 15 nm or less, and formed in a monolayer.
Next, a method of forming TiO2 nanodots on the electrode 20 will now be described.
The TiO2 nanodots are synthesized in a solution as follows. 0.4 g of oleic acid, 20 ml of trioctylamine, 1 ml of oleylamine, and 0.1 g of titanium chloride are simultaneously mixed in a flask in which a reflux condenser is installed by slowly increasing a reaction temperature to 320° C., and the reaction of the reaction mixture is maintained at the reaction temperature of 320° C. for 2 hours. After the reaction is completed, the reaction mixture is cooled as rapidly as possible, and is centrifugally separated by adding acetone which is a non-solvent. Liquid on an upper part of the reaction mixture except the centrifugally separated precipitate is discarded, and the precipitate is dispersed in hexane to obtain a solution of approximately 1 wt %. One organic solvent of, for example, chloroform, dichloromethane, hexane, toluene, ether, acetone, ethanol, pyridine, and tetrahydrofuran may be used instead of the hexane, a solvent of the solution.
The concentration of the TiO2 nanodots may be 0.05 to 1 wt %. If the concentration of the TiO2 nanodots is lower than 0.05 wt %, gaps between the TiO2 nanodots may be large, and thus the density of the TiO2 nanodots may be reduced. If the concentration of the TiO2 nanodots is higher than 1 wt %, the TiO2 nanodot layer may be formed to be thick, and thus it is difficult to form a TiO2 nanodot monolayer.
Next, the organic dispersion agent 38 coordinated on the surfaces of the precursor nanodots 36 is removed. The organic dispersion agent 38 may be removed by processing with O2 plasma for 1 to 5 minutes or in an annealing process in a subsequent process.
Referring to
The PbO reaction gas may be supplied by a thermal evaporation process or a sputtering process. For example, vapour state PbO may be obtained by annealing and evaporating PbO powder. Also, the vapour state PbO may be readily obtained by sputtering Pb target or PbO target installed on a sputter under a plasma atmosphere which includes oxygen O2.
The reaction between the precursor nanodots 36 and the reaction gas may be performed in a temperature range of 400 to 900° C. If the reaction temperature is lower than 400° C., the reaction between the precursor nanodots 36 and the reaction gas may not be smoothly achieved. If the reaction temperature exceeds 900° C., the reaction gas may be vaporized from the ferroelectric nanodots 32 that are already formed.
Referring to
In the method of manufacturing an information storage medium having the ferroelectric nanodots 32 consistent with the present embodiment, re-growing of the precursor nanodots 36 by contacting each other is prevented even at a high temperature of 800 to 900° C. due to the precursor nanodots 36 that are already separated when the ferroelectric nanodots 32 are formed. Therefore, the size of the ferroelectric nanodots 32 is uniform due to high temperature growing which results in a favourable crystalline structure, thereby increasing information storing characteristics.
Also, since there are nearly no gaps between the ferroelectric nanodots 32 and a write/read head portion 40 that contacts the ferroelectric nanodots 32 is relatively larger than the gaps between the ferroelectric nanodots 32, a roughness of the ferroelectric nanodots 32 is recognized to be smooth in view point of the write/read head portion.
Consistent with the present invention, since the diameter of the ferroelectric nanodots may be uniformly controlled to less than 15 nm and the ferroelectric nanodots are separated from each other, re-growing of the ferroelectric nanodots in an annealing process is prevented. Also, the ferroelectric nanodots are uniformly and spontaneously self-assembled on an electrode and a plurality of nanodots form one bit regions. Thus, the ferroelectric nanodots do not need to be precisely assembled. Accordingly, a precise patterning process is unnecessary.
Also, the ferroelectric nanodot layer consistent with the present invention is not a thin film type ferroelectric layer, but a nanodot layer in which nanodots are separated from each other. Therefore, the nanodot crystals have reduced stress, thereby improving magnetic information storing characteristics of the ferroelectric information storage medium.
The method of manufacturing a ferroelectric information storage medium consistent with the present invention is a simple and easy process, and facilitates the manufacture of a ferroelectric recording medium having improved writing characteristics.
While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0018521 | Feb 2007 | KR | national |
