WO2002058060A1

WO2002058060A1 - Optical information recording medium

Info

Publication number: WO2002058060A1
Application number: PCT/JP2001/000305
Authority: WO
Inventors: Hiroki Yamamoto; Takashi Naito; Toshimichi Shintani; Motoyasu Terao; Tetsuo Nakazawa; Mitsutoshi Honda; Tatsumi Hirano
Original assignee: Hitachi, Ltd.
Priority date: 2001-01-18
Filing date: 2001-01-18
Publication date: 2002-07-25
Also published as: JPWO2002058060A1

Abstract

An optical information recording medium having excellent response and high recording density and not deteriorating even after repeated read/write. An super-resolution film (2) aligned with respect to the substrate surface and made of microcrystals of a compound semiconductor is provided on the upper surface of a substrate (1). An optical recording film (4) for recording information optically through a protective film (3) is provided on the upper surface thereof along with a reflective film (5).

Description

Description Optical information recording media Technical field

The present invention relates to an optical information recording medium, and particularly to an optical information recording medium capable of reading and writing at a high recording density, having high reliability for repeated recording and reproduction operations, and capable of coping with high-speed rotation. Regarding the medium. Background art

As optical information recording media, compact discs (CD), laser discs (LD), and recently, DVDs having a recording density seven times or more that of CDs have been put to practical use. DVD is used not only as a read-only ROM that records images and information for computers, but also as a rewritable RAM having a recording film. In order to use this RAM as a recording medium for video signals that record moving images, etc., and to use it as a medium for high-definition recording, it is necessary to increase the capacity even further. To do this, a recording capacity of 20 GB to 100 GB is required on one side. In order to achieve this, studies are being made on shortening the recording wavelength, developing an irradiation lens system with a high NA, multiplex recording, and mounting a photon-mode super-resolution film on the recording medium.

This super-resolution film is a thin film formed on the incident surface side of the recording medium. By reducing the beam spot of the incident light transmitted through the film, high recording density can be achieved. The super-resolution effect utilizes phenomena such as absorption saturation and refractive index change of this film due to laser single light irradiation. The absorption saturation phenomenon utilizes a nonlinear optical characteristic that a super-resolution film transmits light having an intensity higher than the absorption saturation amount and absorbs light having an intensity lower than the absorption saturation amount. The change in the refractive index utilizes a phenomenon in which the refractive index of the film changes due to heating or polarization of the film due to irradiation with a single laser beam. 8-9 6 4 1 2 Phthalocyanine-based organic film, transition metal oxide particle-based inorganic super-resolution film described in JP-A-10-320857, JP-A-111-27331488 Semiconductor film or semiconductor fine particle dispersed film.

In the organic material-based super-resolution film described in Japanese Patent Application Laid-Open No. H08-96412, recording / reproducing is performed because the energy density of a laser beam irradiated at the time of recording or reading becomes extremely high locally. There is a problem that the film is deteriorated by repeating the above. For this reason, it was difficult to guarantee a sufficient number of recording / reproducing operations under severe operating conditions such as a computer RAM. In addition, there was a concern that the solution of the problem would be difficult due to the recent shortening of the laser wavelength. In addition, the transition metal oxide particle-based super-resolution film described in Japanese Patent Application Laid-Open No. 10-32-857 has a sufficient super-resolution for a short-wavelength laser with a wavelength of about 400 nm. There was a problem that the effect could not be obtained. Furthermore, the semiconductor film described in Japanese Patent Application Laid-Open No. 11-27-314 or the semiconductor fine particle dispersion film has a problem that the nonlinear optical characteristics are not sufficient, and it is difficult to obtain sufficient super-resolution characteristics. was there. Therefore, an object of the present invention is to provide a read-only optical information recording medium (ROM disc) which has a large capacity, is less deteriorated by repeated reading, and has excellent responsiveness. Another object of the present invention is to provide a high-response, large-capacity rewritable optical information recording medium (RAM disk) with little deterioration in repeated reading and writing. Disclosure of the invention

In order to solve the above problems, an optical information recording medium according to the present invention comprises: a substrate; a super-resolution film made of an inorganic material formed directly on the substrate or via another thin film; Or, in an optical information recording medium including an information recording film formed through another thin film, the super-resolution film has an absorption edge wavelength within 10% of the earth of one laser wavelength used for recording or reproducing information. And crystalline particles with a grain boundary phase, and the crystalline particles have an orientation. This optical information recording medium can be used as a rewritable optical information recording medium.

Further, an optical information recording medium according to the present invention comprises a substrate on which pits having information are formed. And an optical information recording medium including a super-resolution film made of an inorganic material formed directly on the substrate or through another thin film, wherein the super-resolution film has an absorption edge wavelength used for recording or reproducing information. It is composed of crystalline particles or crystalline particles with a grain boundary phase existing within 10% of the soil of the laser wavelength, and the crystalline particles have an orientation. This optical information recording medium can be used as a read-only optical information recording medium.

In the above-mentioned optical information recording medium which can be used as a rewritable type or a read-only type, the super-resolution film has an absorption edge wavelength within 5% of soil of one wavelength of a laser used for recording or reproducing information. It is more preferable.

Further, the super-resolution film is a crystalline particle having an orientation of a group II-VI compound semiconductor having a wurtzite-type or zinc-blende-type crystal semiconductor or a crystalline particle having an orientation accompanied by a grain boundary phase. The grain boundary phase is composed of an oxide of one or more metals selected from silicon, aluminum, titanium, aluminum metal, and aluminum earth metal, or a component thereof and a component constituting a crystal particle. It is preferably a mixture.

The optical information recording medium according to the present invention also includes a substrate, a super-resolution film made of an inorganic material formed directly on the substrate or through another thin film, and a super-resolution film directly or through another thin film. In the optical information recording medium including the information recording film formed by the above method, the super-resolution film is a crystalline particle having the orientation of a group II-VI compound semiconductor having a plutoite-type or zinc-blende-type crystal structure. Or, it is composed of crystalline particles having an orientation accompanied by a grain boundary phase, and the grain boundary phase is one or more metals selected from silicon, aluminum, titanium, alkali metal and alkaline earth metal. Or a mixture of these with the components constituting the crystal particles. This optical information recording medium can be used as a rewritable optical information recording medium.

An optical information recording medium according to the present invention also includes an optical information recording medium including: a substrate on which pits having information are formed; and a super-resolution film made of an inorganic material formed directly or via another thin film on the substrate. In the above, the super-resolution film is made of crystalline particles or crystals having the orientation of a group II-VI compound semiconductor having a crystal structure of the Uruite or zinc blende type. Is composed of crystalline grains having an orientation accompanied by a grain boundary phase, and the grain boundary phase is an oxide of one or more metals selected from silicon, aluminum, titanium, alkali metals and alkaline earth metals. Alternatively, it is characterized in that it is a mixture of these and the components constituting the crystal particles. This optical information recording medium can be used as a read-only optical information recording medium.

In the optical information recording medium that can be used as the rewritable type or the read-only type, the II-VI compound semiconductor is cadmium and / or zinc, and one or more elements selected from sulfur, selenium, and tellurium. And a compound with The wurtzite compound has a (001) orientation with respect to the substrate surface, and the zinc blende compound has a (111) orientation with respect to the substrate surface.

The content of the group II-VI compound semiconductor contained in the super-resolution film is desirably at least 23% by mol%, more desirably at least 35% and at most 95%. Further, the crystal grains in the super-resolution film preferably have an average particle size of 3.2 nm or more and 17 nm or less, and an average particle size of 3.5 nm or more and 10.1 nm or less. Is even more preferred. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a partial cross section of a RAM disk manufactured in an example of the present invention. FIG. 2 is a diagram showing the spectral transmittance curves of the super-resolution films of Sample Nos. 2, 5, 6, and 7. FIG. 3 is a graph showing the change in the C / N ratio with respect to the mark length.

FIG. 4 is a diagram showing a change in CZN with respect to the CdZnS content.

FIG. 5 is a diagram showing an X-ray diffraction pattern of the super-resolution film of Sample No. 2.

FIG. 6 is a diagram showing an X-ray diffraction pattern of the super-resolution film of Sample No. 6.

FIG. 7 is a diagram showing an X-ray diffraction pattern of the super-resolution film of Sample No. 7.

FIG. 8 is a schematic diagram of a crystal structure of a wurtzite type compound.

FIG. 9 is a schematic diagram of the crystal structure of a sphalerite-type compound.

FIG. 10 is a schematic diagram of a cross-sectional transmission electron microscope image of the super-resolution film of Sample No. 2. FIG. 11 is a schematic diagram of a cross-sectional transmission electron microscope image of the super-resolution film of Sample No. 6. FIG. 12 is a schematic diagram of a cross-sectional transmission electron microscope image of the super-resolution film of Sample No. 7. FIG. 13 is a schematic diagram of a plane transmission electron microscope image of the super-resolution film of Sample No. 2. FIG. 14 is a schematic diagram of a plane transmission electron microscope image of the super-resolution film of Sample No. 6. FIG. 15 is a schematic diagram of a plane transmission electron microscope image of the super-resolution film of Sample No. 7. FIG. 16 is a diagram showing a change in CZN when changing one laser wavelength. FIG. 17 is a diagram showing a change in CZN when one laser wavelength is changed. FIG. 18 is a diagram showing a change in CZN when one laser wavelength is changed. FIG. 19 is a diagram showing a change in CZN when changing one laser wavelength. FIG. 20 is a diagram showing a change in average particle diameter with respect to sputter power.

FIG. 21 is a diagram showing a change in CZN with respect to the average particle diameter of the fine particles of the precipitated semiconductor compound.

FIG. 22 is a schematic diagram of a partial cross section of the ROM disk manufactured in the example of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail with reference to the accompanying drawings. (Example 1)

FIG. 1 shows a schematic diagram of a partial cross section of the RAM disk manufactured in this example. In FIG. 1, 1 is a substrate, 2 is a super-resolution film, 3 and 3 ′ are protective films, 4 is a recording film, and 5 is a reflective film. Also, 10 is a recorded portion (recorded pit). As the substrate 1, polycarbonate, polyolefin, glass, or the like is used according to the specification. In this embodiment, polycarbonate is used. As the protective films 3 and 3 ′, an SiO ₂ -based amorphous film was used. As the recording film 4, a Ge—Sb—Te phase change material was used. As the reflective film 5, an A1-Ti reflective film was used. The super-resolution film, II one VI group compound semiconductor single or their and _{S i O 2, T i 0} 2, S, i 0 2 - were studied mixture film with T i O ₂ such as glass material.

All of the above film formations were performed using a sputtering method. The high-frequency magnetron sputtering method (RF sputtering) was used to form the protective film 3, 3 'and super-resolution film. The DC magnetron sputtering method was used for forming the film 4 and the reflection film 5. The target size of each thin film was 6 mm, and Ar was used as the sputtering gas. The power during sputtering was 600 W to 1.5 kW, and the deposition time was adjusted to obtain the desired film thickness.

The RAM disk shown in FIG. 1 was manufactured by the following steps. A super-resolution film 2 having a thickness of 50 nm was formed on a disc-shaped polycarbonate substrate 1 having a thickness of 0.6 mni, an outer diameter of 120 mm, and an inner diameter of 10 mm. After forming a protective film 3 thereon of 90 nm, a recording film 4 was formed to a thickness of about 20 nm. After forming a protective film 3 'of about 40 to 100 nm, a reflective film of about 200 nm was formed thereon. A desired RAM disk was obtained by laminating two substrates with the film on the back of the reflective film 5 using an ultraviolet curing resin. The thickness of the protective film 3 'was adjusted to the thickness at which the intensity of the reflected light was highest in accordance with the optical characteristics of the super-resolution film to be used.

The obtained optical disk was irradiated with a semiconductor laser having a wavelength of 400 nm to perform writing. At this time, the laser output was adjusted according to the information to be recorded, and the optical disk was irradiated with pulses to form recording pits. In this embodiment, a recorded portion (recording pit) and a non-recorded portion are written at the same cycle. The length of one half of this period (the length of the recording pit) is called the mark length.

The laser output for writing was 15 mW. As a result, the recording film is heated, and the crystalline portion is melted and rapidly cooled to become amorphous, and information is written. Information can be read from the difference between the original reflectance of the crystalline portion and the reflectance of the amorphous portion after writing.

After the pits were formed, the laser output was set to 2 mW and the written pits were read. The difference between the reflectivity of the crystalline part and the amorphous part at this time is defined as the signal (carrier), and the ratio (C / N ratio) of the signal to the noise signal generated by other factors such as the electrical system is evaluated. It can be determined whether or not the re-recorded information is read. In this embodiment, the mark length of the recording pit is changed from 0.1 μπι to 0.6 m, and the CZN ratio for each pit is evaluated to determine whether finer information can be read. It was judged. In addition, as a comparative example, a case where no super-resolution film is formed investigated. At this time, the film configuration other than the super-resolution film of the comparative example was the same as that of the above example. In this example, the linear velocity of the disk rotation was constant at 7 m / sec.

Table 1 shows the composition of the super-resolution film of the fabricated RAM disk, the precipitated phase and the orientation obtained from the X-ray diffraction pattern of this film, and the peak intensity of the orientation plane for the oriented film. The C / N ratio when a pit is formed with a mark length of 0.2 μπι is also shown. In addition, the average particle size of precipitated particles observed from a transmission electron microscope (TEM) image of the film surface observed by the method described later is also shown. As for the particle diameter of each particle, a circle having the same area as the fine particles observed in the obtained TEM image was assumed, and the particle diameter of each particle was calculated based on the diameter. Then, for each sample, the particle size was calculated for 100 to 300 fine particles, and the average value was used as the average particle size.

table 1

Sample Nanba1～ 7 is, C d ₀ absorption edge at about 4 OO nm as the compound semiconductor components. 5Z n. . The ₅ S, also Example der Li when selecting S i O ₂ as the grain boundary phase-forming components, varying the mixing ratio. The sample vo · 7 is a _{_{_{C d 0. 5 Z n 0}}} . 5 S single super-resolution film.

Fig. 2 shows the spectral transmittance curves of the single-layer super-resolution films of samples Nos. 2, 5, 6, and 7 in Table 1. Each thin film has an absorption edge at the position of 400 nm indicated by an arrow and is transparent in a wavelength range longer than that, so that oscillation was observed with respect to wavelength due to interference with back surface reflection. On the other hand, on the shorter wavelength side than the absorption edge, the transmittance decreases to 0.3 or less. I was From this, it is expected that these materials have large absorption for light with a wavelength of 400 nm or less and have a large interaction with light.

Figure 3 shows the CZN ratio with respect to the mark length of Samples Nos. 2, 6, and 7 and a comparative example in which no super-resolution film was formed. In the comparative example, when the mark length was 0.35 or more, a relatively good C / N ratio of about 40 dB or more was shown.However, as the remark length was reduced, the CZN ratio decreased, and the CZN ratio decreased. At 2 μπι, it was about 20 dB. On the other hand, in sample No. 2, although the CZN ratio was slightly improved compared to the comparative example, the CN ratio was almost the same as the comparative example.

On the other hand, in Samples Nos. 6 and 7, the C / N ratio was as high as about 45 dB until the mark length was about 0.2 m. Even at 0.1 μπι, the C / N ratio was as high as 40 dB. Obtained. From this, the super-resolution effect can be obtained by forming a super-resolution film as in Sample Nos. 6 and 7, and recording / reproducing is possible with the same laser-light source even with a small mark length. I understood. Samples Nos. 6 and 7 both had a large super-resolution effect, but it was found that sample No. 6 had even greater super-resolution characteristics than sample No. 7. Was.

Figure 4 shows the CZN ratio at a mark length of 0.2 when a super-resolution film of each composition shown in Table 1 was formed. Comparing this _{_{value, C d 5 Z n 0. 5}} S content of 1 0 mol%, 1 9 mol. /. Sample Nos. 1 and 2 showed 10 dB and 15 dB, which was not much improved compared to 10 dB of the comparative example. On the other _{_{_{hand, C d 0 5 Z n 0}}} 5 S content 2 3~:.. L 00 mole ^_0/0 C / N ratio for the sample Nanba3～ 7 of becomes 30 dB~45 d B as high I was From this, it was concluded that the super-resolution effect can be obtained with thin films such as Sample Nos. 3 to 7. The sample No.5, the sample 6, C d ₀ of the sample No.7. ₅ Z n. . ₅ S content showed higher super-resolution characteristic than 1 100%. Determined from Figure 4 Then, when _{_{C d 0. 5 Z n 0. 5}} S content of 35 mol% or more 9 5 mol% or less, it was found that the C / N is equal to or greater than 40 d B.

When the linear velocity of rotation was increased for the optical disk on which the super-resolution film of Sample No. 6 was mounted, reading and writing were performed with almost no change in the C / N ratio until the high-speed rotation of 15 m / s. It was possible. In addition, write data on the same circuit One 1 5 mW, where having conducted the writing by irradiating a read power 2 mW laser one power, was hardly observed deterioration of C / N ratio is up to 1 0 ⁴ times. As described above, the optical disc on which the super-resolution film of this embodiment was mounted was compatible with high-speed rotation, and was also excellent in durability by laser irradiation.

To pursue the causes of the above phenomena, the microstructure of the super-resolution film of the sample shown in Table 1 was analyzed by X-ray diffraction. The analysis was performed by forming a single film of each super-resolution film on a polycarbonate substrate on which no land group was formed. Figures 5 to 7 show the X-ray diffraction patterns of samples # 2, # 6 and # 7. In the thin film of sample No. 2 shown in Fig. 5, only the halo pattern was observed. On the other hand, in the thin films of samples Nos. 6 and 7 shown in Figs. 6 and 7, a sharp peak was observed at 2Θ == 26.4 ° in addition to the halo pattern. This peak is a hexagonal wurtzite Cd. ₅ Z n. _The (002) plane was found to be perpendicular to the c-axis of 5S.

Here, you describe the crystal system of the C d S based material as described above for C d ₀₅ Z n _Q5 S. Two types of CdS systems are known: hexagonal perzite-type crystal systems such as these thin films, and cubic zinc-blende-type crystal systems. Figures 8 and 9 show schematic diagrams of the crystal structures of urite-type CdS and zinc-blende-type CdS, respectively. In each structure, sulfur (S) ions are closest packed, and the closest packed surface is shown in the vertical direction in the figure. On the surface forming the closest packing, ions are arranged in a hexagon, and the ion sphere forming the surface on the concave portion of the ion sphere is arranged to form the closest structure.

If each plane is defined as A, B, and C, in the wurtzite structure in Fig. 8, the ion sphere on the third layer is located at the same position as the A plane. Therefore, the period of A, B, A, B, ... is established. This results in a hexagonal columnar structure and a hexagonal system. This closest packing direction is defined as the (00 1) axis (c axis).

On the other hand, in the zinc-blende structure, the third layer is located at a different position from the ion sphere of A, and thus has a period of A, B, C, A, B, C .... In such a structure, the unit cell of the cube can be defined by setting the closest packing direction to the (1 1 1) direction. C d ₀ of ordinary random orientation. ₅ Z n. . ₅ In the X-ray diffraction obtained from S powder, since the crystal shown in FIG. 8 are oriented in random orientation, 2 Θ = 26. 4 ° ( (002) plane), 2.0 = 24 ° (( 1 00 ) Plane, 28 ° ((101) plane), 47 ° ((103) plane), etc.

Only the (002) plane was observed in the thin films of Samples Nos. 6 and 7 above. Therefore, in this thin film, most of the precipitated particles had the c-axis shown in Fig. 8 perpendicular to the substrate. It shows that it is growing. Such a state in which many crystal grains grow preferentially in a certain direction is called orientation. Therefore, it can be said that the thin films of Sample Nos. 6 and 7 are thin films oriented in the c-axis direction.

On the other hand, in the thin film of sample No. 2 shown in FIG. 5, such a peak indicating the orientation was not observed. This suggests that the thin film was oriented in a random orientation, or that no crystal grains had precipitated. In order to evaluate the structure of these thin films in more detail, transmission electron microscopy was performed. FIGS. 10 to 12 show schematic diagrams of transmission electron microscope images observed from the cross-sectional direction of the thin film. FIGS. 13 to 15 show schematic images of transmission electron microscope images of the inside of the film surface. From the obtained transmission electron microscope images, the average particle size of the particles found in each thin film was calculated. The particle diameter of each particle was assumed to be a circle having an area equivalent to the fine particles observed in the obtained TEM image, and the particle diameter of each particle was calculated based on the diameter. Then, for each sample, the particle size was calculated for 100 to 300 fine particles, and the average value was used as the average particle size.

A schematic diagram of an electron microscope image of the thin film of Sample No. 2 from the cross-sectional direction is shown in FIG. 10, and a schematic diagram of a transmission electron microscope image of the thin film in the in-plane direction is shown in FIG. These electron microscope image, C d ₀ of the average particle size of about 3 nm in an amorphous glass matrix 7 mainly composed of _{_{S i O 2. 5 Z n}} 0 5 S microparticles 6 are dispersed Was observed. When the electron diffraction pattern was evaluated, the orientation of these precipitated particles was random. Therefore, it is probable that the crystal peak could not be confirmed in the X-ray diffraction pattern shown in Fig. 5 because the amount of X-ray obtained from each particle was small.

Figure 11 shows a schematic diagram of an electron microscope image of the thin film of Sample No. 6 from the cross-sectional direction. FIG. 14 is a schematic diagram of a transmission electron microscope image in the in-plane direction. As shown in FIG. 1 1, in the thin film of the sample No.6, average particle size of about 5 nm of _{_{_{C d 0. 5 Z n 0}}} _ 5 S particles 8 had a very densely packed. Electron diffraction and lattice image observation using high-resolution images showed that these particles were oriented in the c-axis direction with respect to the substrate. This result was consistent with the result of X-ray diffraction shown in FIG. The in-plane transmission electron microscope image shown in Fig. 14 also revealed that the thin film had a structure in which fine particles of about 5 nm were aggregated.

A more detailed observation revealed that there was an amorphous-like grain boundary phase 9 of about 0.5 nm surrounding each crystal particle, as shown in Figs. 11 and 14. If the grain boundary phase composition is analyzed using an energy dispersive X-ray fluorescence analyzer, the grain boundary phase S i 0 ₂ added was Ritsuchi phase. Or I Li, in the thin film shown in this sample _{No.6, C d 5 Z n 0.} 5 S particles 8 side of the S i 0 ₂ Ritsuchi grain boundary phase 9 the surrounding us Li, more each particle c It was found that the structure was oriented so that the axis was perpendicular to the substrate surface.

Next, FIGS. 12 and 15 show transmission electron microscope images of the cross section and plane of the thin film of Sample No. 7. C d also in this thin film. ₅ Z n. . ₅ has a structure in which S particles 8 are densely packed, and c-axis were it was observed growing perpendicular to the substrate. From the cross-sectional image and the plane image shown in Fig. 15, it was confirmed that the average particle size of the particles was about 6 nm, which was slightly larger than that of Sample No. 6. In Sample No. 7, since no SiO ₂ component was added, the amorphous-like grain boundary phase seen in Sample No. 6 was not formed, and the particles were densely present. Was.

As described above, it is difficult to obtain a super-resolution effect in a thin film with a structure in which fine particles are dispersed in a glass matrix and not oriented, as seen in Sample No. 2, and So, C d. . _₅ Z n 0 ₅ S particles are present densely and c-axis was able to obtain a large super-resolution effect as long as a thin film oriented with respect to the base plate. If still more _{_{C d 0. 5 Z n 0. 5}} S grain boundary portions surrounding the glass component of S i O ₂ structure of the particles as in Sample No.6, and the average particle size of the fine particles is small, more A large super-resolution effect was obtained. In the wurtzite-type crystal shown in Fig. 8, C d and S can be regarded as a pair of atoms arranged parallel to the c-axis. When a laser beam is irradiated parallel to this c-axis, the Fermi surface obtained from the band structure generated by the combination of Cd and S is formed perpendicular to this c-axis. In other words, the valence and conduction bands filled with electrons are formed perpendicular to the c-axis. When one laser beam is irradiated here, electrons existing in the valence band are excited into the conduction band by the energy of one laser beam, and an electron-hole pair is formed.

Polarization is generated by the pair of the electron and the hole, and the polarization induces an optical nonlinearity such as a change in refractive index. If the direction of this polarization is parallel to the laser beam, all the polarization components contribute to the nonlinearity, so that high nonlinear optical characteristics can be obtained. If the direction of this polarization is inclined with respect to one laser beam, the nonlinearity decreases. From this fact, it is considered that in the case of the wurtzite type compound, if the film is oriented in the hexagonal c-axis, the polarization component is very large, so that large nonlinearity can be obtained. On the other hand, in the aggregate of fine particles such as sample No. 2, the number of particles that can contribute to large nonlinearity is insufficient because the orientation is random even if the above-mentioned polarization occurs. Therefore, it can be considered that no large non-linearity occurred and it was difficult to obtain the super-resolution effect. The S i 0 ₂ super-resolution effect towards the sample No.6 added with components from the sample No.7 was good. In the case of sample No. 6, this is due to the addition of S i 〇 ₂ as shown in Figs. 11 and 14. . ₅ Z n. . ₅ grain growth of S crystals is inhibited, the crystal grain size has remained below 8. 5 nm, C d to the grain boundary phase of S i O ₂ is present between the further particles. . _₅ Z n 0. ₅ S for binding between the particles is eliminated, there is no movement between the electron particle child generated in the conduction band, polarization is considered to become more likely to be retained. In the case of sample No. 7, the average particle size is as large as 10 nm, and the adjacent particles are in contact with each other without passing through the grain boundary phase. Sample No.3, 4, for five sample No.6, 7 similar super-resolution effect is obtained and, further Urutsuai preparative C d _{_0.} ₅ Z n ₀ of ₅ S (00 1) oriented in the direction Was. However, different peak _{_{_{intensities, C d 0. 5 Zn 0}}} . The more ₅ S content _{_{_{C d 0. 5 Z n 0}}} . 5 peak intensity of S (002) has been increased. Also this C d. ₅ Z n. Contained Increased and C d ₀ of the _{_{_{amount. 5 Z n 0. 5 S}}} (002) C Bruno N ratio with increasing peak intensity tended to have increased. From this, C d is polarized. . Considered nonlinearity also increased by increasing the _₅ Z n 0. ₅ S amount.

As described above, as in sample Nos. 1 and 2, C d. . ₅ Z n. _{When the} 5S content is small, the structure becomes a dispersion type of fine crystal particles, and Cd. . ₅ Z n. . ₅ S microcrystal grains were the small nonlinearity to face the random orientation. Also, as shown in Sample Nos. 3 to 7, C d. . ₅ Z n. . ₅ When S content is high became Oriented structure in the c-axis of the hexagonal _{_{_{C d 0. 5 Z n 0}}} 5 S. In this case, a large nonlinearity was obtained, and a super-resolution effect was obtained.

Furthermore, if the S i O ₂ component is appropriate, C d. . _₅ Z n ₀ _ ₅ shrinking crystal grain size while maintaining the orientation of S, to further grains is isolated, large Juna super-resolution effect due to optical nonlinearity is obtained.

C d as shown in Table 1 and FIG. ₅ Z n. _If the content of 5S is 23% or more in molar ratio, oriented Cd. . ₅ Z n. . ₅ S crystal particles were obtained, CZN exceeds 30 d B, it was possible to obtain a super-resolution effect. In order to obtain an even higher super-resolution effect where CZN exceeds 40 dB, C d is required. . ₅ Z n. . It may be the ₅ S content in a molar ratio of 35% or more 95% or less and.

If _{_{C d 0. 5 Z n 0 _}} 5 S content is less than _{_{23%, C d 0. 5}} Z n 0 5 Oriented of S particles becomes random, high super-resolution effect is difficult to obtain. The _{_{_{C d 0. 5 Z n 0}}} 5 and S content is less than 35% of that super-resolution effect is obtained, sufficiently high CZN ratio is hardly obtained. Furthermore _{_{_{C d 0. 5 Z n 0}}} . 5 S content exceeds 95% when the S i O ₂ content is not sufficient, the grain boundary phase component less of Li, cause coarsening of the particles, characteristics Decrease slightly.

(Example 2)

Table 2, compound semiconductor component similar to C d as in Example _{_{_{1 0. 5 Z n 0.}}} 5 and _{S, S i O 2 'T} i 0 2 components of the grain boundary phase, A l ₂ O _3, T _{_{i O 2, S i 0 2}} - Na 2 O- C a O _{_{glass, S i O 2 - K 2}} O- C a O _{glass, S i O 2 - N a} 2 0- MgO glass, S i 0 ₂ - shows a sample No.8~ l 4 in the case of the B ₂ 0 ₃ glass. Evaluation items, medium structure The construction was the same as in Example 1.

Table 2

C d ₀ of the compound semiconductor component. ₅ Z n _0. ₅ S content was fixed at 90 mol ^_0/0 obtained good results in Example 1. _{_{C d 0. 5 Z n n 5}} S (OO l) orientation can be obtained even when using any of the grain boundary phase component and could be obtained at a high super-resolution effect. However, it occurs and _{_{_{C d 0. 5 Z n 0}}} . Particle size of ₅ S crystal grains are slightly different, CZN ratio obtained therefore had slightly changed by changing the grain boundary phase component .

When Sio ₂ · TiO ₂ was used as the grain boundary phase component, the average particle size was as small as about 6.2 nm, and the CZN ratio was as large as 46. When Al ₂ O ₃ Ti O ₂ was used, the average particle size was about 7 nm, and both the average particle size and the CZN ratio were almost the same as those of the Sample No. 1 Sio ₂ system. there were.

S i O ₂ —Na ₂ O—C aO S i 〇 ₂ —K ₂ O—C a OS i

試料, — N a ₂ O— MgO S i O ₂ — B ₂ O ₃ Sample No.l using each glass:! 1

In the case of 4, on the contrary, the average particle size increased to about 9.5 nm, and as a result, the C / N ratio decreased slightly. However, in each case, a super-resolution effect equivalent to that of sample No. 6 in Table 1 was obtained, and it was good as a grain boundary phase component.

As described above, the grain boundary phase component _{_{S i O 2 T i 0 2}} A 1 2 0 3 or N a _The glass preferably contains an alkali metal such as ₂ O and K ₂₀ and an alkaline earth metal such as CaO and MgO.

(Example 3)

Next, we investigated in detail compound semiconductor materials that have the optimum composition as a super-resolution film for various laser wavelengths. In compound semiconductors, it is possible to arbitrarily change the absorption wavelength by making a compound (mixed crystal) of two or more semiconductor substances. C d shown in Examples 1 and 2. ₅ Z n. _Since the absorption edge of 5S is 403 nm, it is considered that the 5S has a stronger interaction with a laser beam with a wavelength of 400 nm. Therefore, in order to have a super-resolution effect at one laser wavelength to be used, it is necessary to use a compound semiconductor having a composition edge having an absorption edge close to the laser wavelength to be used.

In this example, the composition of the mixed crystal of CdS and ZnS having an absorption at 320 nm (3.83 eV) was changed, and the super-resolution effect for lasers of various wavelengths was changed. investigated. We also examined the super-resolution characteristics with these films to a thin film to prepare a mixture thin film of S i 0 _2.

The longer the wavelength of the laser used, the longer the mark length that can be read with a high CZN. Therefore, in order to properly evaluate the super-resolution effect at each wavelength, the super-resolution characteristics were evaluated by the following method.

The C / N ratio to the mark length described in Example 1 was measured for the optical disk of the comparative example in which no super-resolution film was formed at each wavelength, and the C / N when the mark length was reduced was 8 d. The mark length when it decreased to B was measured. Then, the CZN at the mark length at which the CZN of the comparative example was 8 dB was evaluated in the example sample in which the super-resolution film was formed.

Composition of the prepared mixed crystal, absorption wavelength measured by the same method as in Example 1, precipitated phase, orientation evaluated by X-ray diffraction, peak intensity of X-ray diffraction of oriented surface when oriented, each laser wavelength Table 3 shows the C / N ratio with respect to. Table 3

As shown in Table 3, Nos. 15 to 19, when ZnS was added to CdS and the content was changed, the absorption wavelength decreased from 481 nm to 320 nm, almost the Zn content. It decreased in proportion. The same tendency was obtained even when 1% O ₂ O was added as in Nos. 20 to 24. In each of the thin films, the precipitated phase was perzite-type crystal, and it was found that the thin film was oriented in (00 1). Sample No. 25 uses a single phase of ZnSe, which has an absorption edge at 443 nm.

Figures 16 and 17 show the CZN when using the super-resolution film of each composition for each laser wavelength. FIG. 16 shows the case where the SiO ₂ content is 0 m 0 1%, and FIG. 17 shows the case where the SiO ₂ content is 10 m 0 1%. From this figure, it can be seen that there is a wavelength range corresponding to the absorption wavelength of each semiconductor compound component and in which a high CZN can be obtained. For example, when CdS of sample No. 15 is used, the absorption edge is 480 nm, and at this time, the wavelength of the laser is 42 5 ηπ! High CZN of 30 dB between ~ 550 nm Was. Furthermore, one wavelength of laser 450 ηπ! At ~ 500 nm, a very high C-N value of 40 dB or more was obtained. Sample No. 17 has an absorption edge of 403 nm and a laser wavelength of 3 55 ηπ! The CZN was more than 30 dB in the range of 520520 nm and more than 40 dB in the range of 380-420 ηm. Sample No. 25 of ZnSe single phase has an absorption edge wavelength of 443 nm and a laser wavelength of 37 0 ηπ! ~ 30 dB or more at 30 nm, 420 ηπ! At ~ 450 nm, high CZN of 40 dB or more was obtained.

As described above, there is a laser wavelength range where a C / N of 30 dB or more, more preferably 40 dB or more, is obtained around each absorption wavelength. In the examination of Samples Nos. 15 to 25 shown below, a high CZN of 30 dB or more could be obtained using a wavelength laser within 10% of the soil at the absorption edge. Using a laser with a wavelength within ± 5%, a higher CZN of 40 dB or more could be obtained.

In the examination of sample Nos. 15 to 24 in Table 3, the absorption edge of CdS was 480 nm and the absorption edge of ZnS was 320 nm. Although it was possible, by using a compound semiconductor such as CdSe, ZnTe, CdTe, etc. having an absorption edge on the longer wavelength side, a laser with a longer wavelength could be used. The same effect can be obtained.

Table 4 shows the absorption wavelength, precipitated phase, orientation, and C / N ratio when using a CdSSe-based semiconductor material in which CdSe is added to CdS. Each measurement method was the same as the method shown in Table 3.

Table 4

In Sample Nos. 26 to 35 using this CdSSe-based semiconductor material, the absorption wavelength became longer as CdSe was added to CdS. In the case of sample No. 28 with a molar ratio of C d S: C d Se of 1: 1, the absorption wavelength is 577 nm, and in the case of sample No. 30 of C d Se alone, the absorption is long. Was 675 nm.

Further, when C d S gradually added C d S e, the addition of Urutsu Ait type compound seen at C d S alone, C d S of the sample No.2 9 0. a S e 0. ₇ At that time, a cubic sphalerite compound was precipitated. In this case, only the (11 1) peak of the cubic system was observed, and it also had the orientation. Further, the (111) direction of the cubic system was equivalent to the (001) direction of the hexagonal system, and was oriented in a direction in which polarization easily occurred. In addition, TEM observation showed that the sample In the samples of Nos. 26 to 30, fine particles with a grain size of about 10 nm without a grain boundary phase were precipitated. In the case of sample Nos. 31 to 38, the particles were aggregates of fine particles less than 10 nm in diameter with an amorphous grain boundary phase.

Fig. 18 and Fig. 19 show the change in C / N ratio when the laser wavelength is changed. As with the samples in Table 3, each sample in Table 4 differs in the laser one wavelength range where high CZN is obtained depending on the absorption edge wavelength, and is 40 d if within ± 5% of the absorption edge wavelength. It can be seen that a high C / N higher than B can be obtained. In addition, as shown in Sample Nos. 35 to 37 in Table 4, even if a single-phase film such as CdSe, ZnTe, A super-resolution effect was obtained in the region. Further, as shown in sample No. 38, CdSe which is a mixed crystal of CdSe and CdTe. ₅ Te. _{For 5,} there was an absorption edge near the wavelength of 730 nm, and a high super-resolution effect was obtained at a laser wavelength near that wavelength. From the above examinations, when the compound semiconductor is a mixed crystal single phase, or when these are combined with a glass material such as SiO _{2, the} wavelength of the laser used is within ± 10% of each absorption edge wavelength, more preferably. Could achieve a high super-resolution effect within 5% of soil. If the compound semiconductor used at this time is a compound semiconductor composed of a group VI element such as cadmium and zinc and a group II element such as sulfur, selenium, and tellurium, visible light from near ultraviolet to near infrared , A high super-resolution effect was obtained in the wavelength range up to. In addition, a high super-resolution effect was obtained not only for the wurtzite-type compound but also for the cubic zinc-blende-type compound. In the case where a wurtzite type compound is precipitated, it is preferable that the compound is (00 1) oriented, and in the case of a zinc blende type compound, it is preferable that the compound is (11 1) oriented.

(Example 4)

Next, the particle size of the super-resolution film deposited by changing the sputtering conditions was changed, and the change in super-resolution characteristics with respect to the particle size was examined. Using the thin film of No. 6 in Table 1 as the super-resolution film, a DVD-RAM disk having the same structure as that shown in Fig. 1 was prepared. The CZN at a mark length of 0.2 μπι The ratio was evaluated.

Table 5 shows the average particle size of the super-resolution film when the sputtering rate was changed and the C / N ratio of the DVD-RAM disk equipped with the super-resolution film. See Table 5 FIG. 20 shows the change in the average particle size with respect to the obtained sputtered powder, and FIG. 21 shows the C / N ratio with respect to the average particle size. Evaluation of the average particle size was calculated from the plane image of the transmission electron microscope in the same manner as in Example 1. Table 5

As shown in Table 5 and FIG. 20, the average particle size tended to decrease as the sputter power increased. As shown in Fig. 21, C increased with increasing average particle size up to an average particle size of about 6.0 nm, but C / N decreased with increasing average particle size. There was a tendency to move. Judging from Fig. 21, when the average particle size was 3.2 nm or more and 17 nm or less, the CZN ratio was 30 dB or more, and a super-resolution effect was obtained. When the average particle size was 3.5 nm or more and 10 0.1 nm or less, the C / N ratio was 40 dB or more, and more favorable results were obtained. If the average particle size is less than 3.2 nm or more than 17 nm, the C ratio is less than 30 dB, which is not preferable.

As described above, in order to obtain the super-resolution effect, the average It was preferred that the particle size was between 3.2 nm and 17 nm. In order to obtain a higher C / N ratio, it is preferable that the average particle diameter of the fine particles of the semiconductor compound to be deposited is not less than 3.5 nm and not more than 10.1 nm.

(Example 5)

Next, an optical disk having a ROM structure shown in Fig. 22 was manufactured and its super-resolution characteristics were evaluated. In FIG. 22, 1 is a polycarbonate substrate, 10 is a recording pit recorded with information, 2 is a super-resolution film, 3 is a protective film, and 5 is a reflective film. In this example, the CdS-based thin film shown in Sample No. 6 in Table 1 was used as the super-resolution film of No. 3. In addition, a SiO ₂ protective film was used as the protective film 3. The reflective film of No. 5 was made of A1-Ti alloy.

As shown in FIG. 22, the optical disc has lands (hills) and groups (valleys) for tracking, and recording pits having information are formed on both lands.

The ROM disk was manufactured by the following steps. First, a pit pattern having a mark length of 0.1 to 0.6 μm was formed on a photoresist using a laser. Thereafter, the pit pattern was copied into a Ni mold, and a polycarbonate was injected into the mold to form a substrate. On this substrate, a super-resolution film having a thickness of 50 nm was formed by sputtering, a 90-nm SiO ₂ protective film was formed, and then a 100-nm-thick A1-Ti reflective film was formed. The thickness of the substrate 1 is 0.6 mm, and in this embodiment, the two substrates formed are bonded together with the reflective film as the back using an ultraviolet curing resin to obtain a ROM disk having a thickness of 1.2 mm. Was.

When the reproduction wavelength was set to 400 nm and the C / N ratio to the mark length was evaluated using this ROM disk, it was 42 dB for the mark length of 0.2 μπι. It turned out to have high super-resolution characteristics. As described above, by mounting the super-resolution film of the present invention on an optical disc such as a ROM or a RAM, the super-resolution film can be applied to a large-capacity recording medium compatible with high-speed rotation. Industrial Applicability · According to the present invention, by using an oriented II-VI compound semiconductor, an optical disk having a high super-resolution effect in all wavelength ranges from near ultraviolet to visible light and near infrared region can be obtained. In addition, by mounting this super-resolution film on an optical disk, a highly responsive, large-capacity rewritable optical disk (RAM disk) with little deterioration due to repeated reading and writing can be obtained. In addition, a read-only light (ROM disk) with a large capacity, less deterioration with repeated reading and writing, and excellent responsiveness can be obtained.

Claims

The scope of the claims

1. A substrate, a super-resolution film made of an inorganic material formed directly on the substrate or through another thin film, and an information recording film formed directly on the super-resolution film or through another thin film. In an optical information recording medium containing

The super-resolution film is composed of crystalline particles or crystalline particles accompanied by a grain boundary phase, whose absorption edge wavelength is within 10% of soil of one laser wavelength used for recording or reproducing information. The optical information recording medium, wherein the crystalline particles have an orientation.

2. An optical information recording medium including a substrate having information-formed pits formed thereon and a super-resolution film made of an inorganic material formed directly on the substrate or through another thin film, wherein the super-resolution film is Is composed of crystalline particles or crystalline particles with an intergranular phase whose absorption edge wavelength is within 10% of the soil of one laser wavelength used for recording or reproducing information. An optical information recording medium, wherein the particles have orientation.

3. The optical information recording medium according to claim 1, wherein the super-resolution film has an absorption edge wavelength within 5% of a laser wavelength used for recording or reproducing information. Optical information recording medium.

4. The optical information recording medium according to any one of claims 1 to 3, wherein the super-resolution film has an orientation of a group II-VI compound semiconductor having a wurtzite type or zinc blende type crystal structure. And crystalline particles having an orientation accompanied by a grain boundary phase, wherein the grain boundary phase is selected from silicon, aluminum, titanium, an alkali metal, and an alkaline earth metal. An optical information recording medium, which is an oxide of a plurality of metals or a mixture of them with components constituting crystal grains.

5. A substrate, a super-resolution film made of an inorganic material formed directly on the substrate or through another thin film, and an information recording film formed directly on the super-resolution film or through another thin film. In an optical information recording medium containing

The super-resolution film has a wurtzite-type or zinc-blende-type crystal structure. It is composed of crystalline particles having an orientation of a group VI compound semiconductor or crystalline particles having an orientation accompanied by a grain boundary phase, wherein the grain boundary phase is silicon, aluminum, titanium, aluminum alloy, and aluminum alloy. An optical information recording medium characterized by being an oxide of one or more metals selected from the earth metal or a mixture of them with a component constituting a crystal particle.

6. An optical information recording medium including a substrate on which pits having information are formed, and a super-resolution film made of an inorganic material formed directly or through another thin film on the substrate, wherein the super-resolution film is Is composed of crystalline particles having an orientation of a II-VI compound semiconductor having a wurtzite type or zinc blende type crystal structure or crystalline particles having an orientation accompanied by a grain boundary phase. The field phase is an oxide of one or more metals selected from silicon, aluminum, titanium, an alkali metal, and an alkaline earth metal, or a mixture thereof with a component constituting a crystal particle. Information recording medium.

7. The optical information recording medium according to claim 5, wherein the II-VI compound semiconductor is a compound of cadmium and / or zinc and one or more elements selected from sulfur, selenium, and tellurium. An optical information recording medium characterized by the above-mentioned.

8. The optical information recording medium according to claim 5, 6 or 7, wherein the wurtzite compound has a (01) orientation with respect to the substrate surface, and the zinc blende compound has a (01) orientation with respect to the substrate surface. 1 1 1) An optical information recording medium having an orientation.

9. The optical information recording medium according to any one of claims 5 to 8, wherein the content of the group II-VI compound semiconductor contained in the super-resolution film is at least 23% by mol%. An optical information recording medium characterized by the above-mentioned.

10. The optical information recording medium according to any one of claims 5 to 9, wherein the content of the group II-VI compound semiconductor contained in the super-resolution film is at least 35% by mole and at least 95%. % Or less.

11. The optical information recording medium according to any one of claims 1 to 10, wherein the crystal grains in the super-resolution film have an average particle size of 3.2 nm or more and 17 nm or less. An optical information recording medium characterized by the above-mentioned.

1 2. The optical information recording medium according to any one of claims 1 to 10, wherein the crystal grains in the super-resolution ^ have an average particle size of 3.5 nm or more and 10 0.1 nm or less. An optical information recording medium characterized by the following.