JPH01294246A - Optical memory element - Google Patents

Abstract

PURPOSE:To improve information reproducing characteristics, corrosion resistance and recording sensitivity by forming a reflecting film layer of a thin film of an aluminum-palladium alloy contg. a specific ratio of palladium. CONSTITUTION:The reflecting film layer 5 of the magneto-optical memory element having the recording part of a multilayered film structure contg. the reflecting film layer 5 and transparent dielectric film layers 2, 4 on a substrate 1 is formed of the thin film of the aluminum-palladium alloy contg. 1-10atm% palladium. The reflectivity substantially equal to the reflectivity of the thin film of aluminum alone is obtd. with the thin alloy film having the compsn. range of AlXPd1-X(0.9<=X) and the thermal conductivity of the palladium is extremely lower than the thermal conductivity of the aluminum; further, the corrosion resistance thereof is higher than the corrosion resistance of the thin film of the aluminum alone. The reproducing performance, corrosion resistance and recording sensitivity are thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical memory element that records, reproduces, erases, etc. information by irradiating it with light such as a laser.

(Prior Art) In recent years, optical memory elements have been actively developed as optical memory elements capable of recording, reproducing, and erasing information.

Among these, those using a rare earth transition metal amorphous alloy thin film as a recording medium have the following advantages: recording bits are not affected by grain boundaries, and it is relatively easy to fabricate a storage medium film over a large area. has attracted particular attention.

However, when an optical memory element is constructed using such a rare earth transition metal amorphous alloy thin film as a storage medium, a sufficient magneto-optical effect (Kerr effect, Faraday effect) cannot be obtained, and therefore the S of the reproduced signal is /N was insufficient. In order to solve these problems, a magneto-optical memory element employing an element structure called a reflective film structure has been proposed, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-12428.

FIG. 4 is a partial side sectional view of an optical memory element having a conventional reflective film structure.

In the figure, a is a transparent substrate, b is a transparent dielectric film having a higher refractive index than the transparent substrate a, C is an amorphous alloy thin film made of a rare earth transition metal, and d is a transparent dielectric film. , e is a metal reflective film.

By employing the above element structure, the Kerr rotation angle is significantly increased. The reason for this is that when the amorphous alloy thin film C is irradiated with laser light from the transparent substrate a, the incident laser light repeatedly reflects inside the transparent dielectric film and interferes, resulting in an apparent Kerr rotation angle. This is because it increases. At this time, the larger the refractive index of the transparent dielectric film, the greater the effect of increasing the Kerr rotation angle.

Here, a composite film of a transparent dielectric film d and a metal reflective film e is
When considered as two reflections Hr, the light enters from the side of the transparent substrate a, passes through the amorphous alloy thin film C, is reflected at the reflective layer f, and then passes through the amorphous alloy thin film C again. ,
The light incident from the transparent substrate a side and reflected on the surface of the amorphous alloy thin film C will be combined, but during this combination, the laser light will be reflected on the surface of the amorphous alloy thin film C. The apparent Kerr rotation angle is increased by the combination of the Kerr effect caused by this and the Faraday effect caused by the laser light passing through the inside of the amorphous alloy thin film C.

In optical recorder 4G elements with such a structure, it is extremely important how to add the Faraday effect to the Kerr effect, and for this purpose, it is necessary that the metal reflective film e has a high reflectance to the laser beam used. is the condition. Materials that meet these conditions include Au, Ag, Cu,
Examples include materials such as AI.

(Problem to be solved by the invention) By the way, the metal reflective film e is made of Au, Ag, or Cu.

In an optical memory element using a material such as Aj2, recording is performed by raising the temperature of the amorphous alloy thin film C using the heat of the laser beam, but since the thermal conductivity of the metal reflective film e is high, Heat escapes from the crystalline alloy thin film C through the metal reflective film e. For this reason, there was a problem in that the temperature of the amorphous alloy thin film C did not rise sufficiently, resulting in deterioration of recording sensitivity.

This problem can be solved by using a material with relatively low thermal conductivity, such as stainless steel or Ti, as the material for the metal reflective film e.
, Ag, Cu, Aj+, and other materials, the effect of increasing the Kerr rotation angle is reduced.
A new problem arises, such as deterioration of playback performance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical recording element having a reflective structure that includes a metal reflective film that has high reflectance and low thermal conductivity.

(Means for Solving the Problems) The optical memory element of the present invention is a magneto-optical memory element having a recording section with a multilayer structure including a reflective film layer and a transparent dielectric film layer on a substrate, in which the reflective film layer is latm%~10at
It is made of an aluminum-palladium alloy thin film containing m% palladium.

(Function) FIG. 3 shows the relationship between the amount of palladium added and the reflectance of the aluminum-palladium alloy thin film when palladium is added to aluminum. As is clear from the figure, it can be seen that the alloy thin film having a composition range of AN*Pd+-x (0,9≦X) has a reflectance that is almost the same as that of a single aluminum thin film. Therefore, in an optical memory element having a reflective film layer having such a composition ratio, the reproduction performance hardly deteriorates compared to when the reflective film layer is formed of aluminum.

Also, since the thermal conductivity of palladium is very low compared to aluminum, A ixp d, -, (0,99≧X)
The recording sensitivity of an optical memory element having a reflective film layer having a composition within this range is significantly improved.

Furthermore, A l , P d I−X (0,99≧X≧0
．． The aluminum-palladium alloy thin film with a composition ratio of 90) has excellent corrosion resistance compared to a thin film made of pure aluminum,
This makes it possible to form an optical memory element with excellent corrosion resistance.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a transparent substrate made of glass, polycarbonate, acrylic, etc., and a first transparent dielectric film of aluminum nitride (A7!N) is formed on the transparent substrate 1.
) A film 2 is formed to have a film thickness of, for example, 80 nm, and on this AIN film 2 terbium, iron, which is an upper earth transition metal alloy thin film, is formed.
For example, the cobalt (TbFeCo) alloy thin film 3 has a film thickness of 20 mm.
nm, and a second layer is formed on this TbFeCo alloy thin film 3.
The transparent AIN film 4, which is a dielectric film, has a thickness of 30 nm, for example.
Further, on this AIN film 4, an aluminum-palladium alloy film 5 (A1qbPd4) is formed as a reflective film.
is formed to have a thickness of 50 nm, for example.

Each of these layers is formed by a sputtering method, but the film forming method may be a vacuum evaporation method, an ion blating method, or the like in addition to the sputtering method.

When an optical memory element having the above configuration was manufactured, the apparent Kerr rotation angle was 1.7 degrees, which was almost the same as when the reflective film was made of Al alone.

In addition, the optical memory element having the above structure and the reflective film may be used in A.
Table 1 shows the relationship between the signal-to-noise ratio and the optimum laser output when an IMHz signal is recorded and reproduced in each optical storage element.

Table 1 Table 1 shows that although the signal-to-noise ratio (S/N) is almost the same, the optical memory element using the aluminum-palladium alloy thin film according to the present invention as a reflective film has higher recording sensitivity.

Furthermore, FIG. 2 shows the relationship between the amount of palladium added and the amount of pinholes generated after immersion in the NaCl solution when palladium was added to aluminum. As is clear from the figure, the aluminum-palladium alloy thin film according to the invention is less likely to generate pinholes than a single aluminum thin film, and therefore an optical memory element with excellent corrosion resistance can be formed.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide a reflective film with high reflectance, low thermal conductivity, and excellent corrosion resistance. and excellent corrosion resistance,
Moreover, an optical memory element with high recording sensitivity can be formed.

[Brief explanation of the drawing]

1 to 3 show drawings of the present invention, FIG. 1 is a partial side sectional view showing the structure of an embodiment of an optical memory element, and FIG. 2 shows the amount of palladium added in an aluminum-palladium alloy thin film. A curve diagram showing the relationship between the amount of pinholes generated,
FIG. 3 is a curve diagram showing the relationship between the amount of palladium added and the reflectance in an aluminum-palladium alloy thin film, and FIG. 4 is a partial side sectional view showing the structure of a conventional optical memory element. 1...Transparent law plate 2.4...AAN film 3...TbFeCo alloy thin film 5...AlPd alloy film Fig. 7

Claims (1)

[Claims] 1) In a magneto-optical memory element having a recording section with a multilayer structure including a reflective film layer and a transparent dielectric film layer on a substrate, the reflective film layer is an aluminum-palladium alloy thin film containing 1 atm % to 10 atm % of palladium. An optical memory element characterized in that it is formed of.