JPH0444330B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical information recording medium in which information is recorded using a light beam, and particularly to a recording thin film that can record information with small optical energy. It is.

(Prior Art and Problems) In an optical information recording medium, a recording thin film is irradiated with a light beam, and the material constituting the recording thin film is amorphous. A method of recording information by causing a change in reflectance due to crystalline transition is known. As recording film materials, tellurium lower oxide TeOx (0<x<2) and antimony triselenide Sb ₂ Se ₃ are known.
There are drawbacks such as a small amount of change in reflectance before and after irradiation with a light beam, and the need to laminate a light energy absorbing layer. The present applicant previously proposed a germanium telluride GeTe thin film in Japanese Patent Application No. 13745/1983 as a material to overcome the above-mentioned drawbacks. GeTe
has the advantage of having a large change in reflectance before and after light beam irradiation and being able to form a recording film with a single layer, but in order to produce an amorphous-crystal transition, the thin film must be
It was necessary to provide light energy to achieve this. Therefore, for high-sensitivity recording, for example, when recording video signals in real time, a high-output light beam device is required, which has the drawback of making the recording and reproducing device expensive.

(Means for Solving the Problems) An object of the present invention is to eliminate the above-mentioned drawbacks of the GeTe recording thin film and to provide an optical information recording medium that can record and reproduce information with small optical energy. The feature is that the recording thin film is made of Ge and Pb.
It is a metal thin film whose main components are Te and Ge, Pb.
and Te has a composition (atomic ratio) of Ge _1-x PbxTe (0<x≦0.5).

(Example) A detailed explanation will be given below based on examples.

The substrate used for optical information recording media has low thermal conductivity, and the surface of the substrate must be smooth and free from scratches. Must be transparent. For such a substrate, a synthetic resin transparent to recording and reproducing laser light, such as polymethyl methacrylate, polycarbonate, polyvinyl chloride, polysulfone, etc., or glass is used.

The information recording thin film can be provided in contact with the substrate, but it is also possible to provide a heat-blocking thin film made of a low thermal conductivity material on the substrate, a polymer coating film to remove scratches existing on the substrate, or a light beam reflective thin film. It can also be provided via. The metal recording film can be deposited on the substrate by known techniques such as vacuum deposition, sputtering, ion plating, etc.

In this example, the recording thin film was deposited on the substrate by vacuum deposition. By vacuum evaporation method
To produce a Ge _1-x PbxTe (hereinafter sometimes referred to as GePbTe) alloy thin film, it is possible to use a single evaporation method using a GePbTe alloy as an evaporation source or a binary simultaneous evaporation method using GeTe and PbTe as an evaporation source. All of these were effective for the present invention.

The alloys used in the one-source evaporation method were prepared as follows: Ge, Pb, and Te with a purity of 99.99% or higher were weighed to give the desired alloy composition, and placed in a quartz glass tube and vacuum-sealed. This quartz glass tube is 1000
℃ for 5 hours and then rapidly cooled to obtain a GePbTe alloy. GePbTe alloy can be evaporated by either resistance heating method or electron beam heating method. Note that a slight difference between the evaporation source alloy composition and the thin film alloy composition was observed in the resistance heating method, so by taking this into consideration and changing the alloy composition, a GePbTe thin film with the desired alloy composition can be obtained. . On the other hand, in the electron beam heating method, no difference was observed between the evaporation source alloy composition and the thin film alloy composition.

Next, FIG. 1 is a diagram showing a two-dimensional simultaneous evaporation method, in which a rotating substrate holder 12 is provided in a vacuum chamber 11, and a substrate 13 is attached below it. Below the substrate 13 are evaporation sources 14 and 15, each filled with GeTe and PbTe as indicated by diagonal lines. Evaporation sources 14 and 15 have independently controllable power supplies 16 and 17;
By changing the power supplied to the GePbTe thin film, the ratio of Ge to Pb in the produced GePbTe thin film was changed, and a GePbTe thin film with a desired alloy composition was obtained. The alloy composition was determined using a fluorescent X-ray spectrometer.

The solid line 21 in Fig. 2 shows the results of forming Ge _1-x PbxTe alloy thin films with various values of x.
This is the result of measuring the transition point. The measurement was carried out by heating a sample with a GePbTe alloy thin film deposited on a glass substrate, and the transition point was defined as the point where the optical properties of the thin film's reflectance or transmittance changed significantly. In addition, the solid line 22 in Fig. 2 shows that the Ge _1-x PbxTe thin film deposited on the substrate is exposed to semiconductor laser light with a wavelength = 830 nm for 200 ns.
The graph shows the relative value of the recording energy (laser power) required to significantly change the reflectance of the laser beam irradiated area of the Ge _1-x PbTe thin film when irradiated for a period of time. As seen in Figure 2, the Ge _1-x PbxTe thin film is
Compared to a GeTe thin film, as the value of X in a Ge _1-x PbxTe thin film increases, the amorphous-crystal transition point decreases;
Therefore, the light energy required to record information is 75% when x = 0.2, and 40% when x = 0.4.
%, respectively 33% and 60% compared to GeTe thin film.
can save light energy.

In this example, the GePbTe alloy thin film was produced by a vacuum evaporation method, but the same results could be obtained not only by the vacuum evaporation method but also by the well-known sputter link method. Ta. however,
In this case, the amorphous-crystalline transition point of the GePbTe thin film is
Compared to the vacuum evaporation method, the value of x in the Ge _1-x PbxTe thin film was 20 to 40 times higher, regardless of the value of x. However, the transition point of the GeTe thin film fabricated by the sputtering method is 480〓
Therefore, the transition point of the Ge _1-x PbxTe thin film is lower than that of the GeTe thin film regardless of the value of x;
The effect of lowering the transition point with increasing value of is the same as in the previous example using the vacuum evaporation method. Further, although a semiconductor laser was used as the light beam in the above embodiment, the light beam is not limited to a semiconductor laser, and a laser beam such as a He-Ne laser or an Ar laser, a Canon lamp, or a tungsten lamp can be used. . Because GePbTe thin film
This is because, like the GeTe thin film, the wavelength dependence of the optical properties is gentle, and the thickness of the thin film can be optimized depending on the recording light beam wavelength.

The reason why the composition of the Ge _1-x PbxTe alloy thin film is set to 0<x≦0.5 in the present invention is as follows.
In a Ge _1-x PbxTe alloy thin film, as x increases, the amorphous-crystalline transition temperature of the thin film decreases.When x=0.5, the transition point is 310〓, which is slightly higher than room temperature, but when x>0.5, This is because the produced thin alloy film has already transformed into a crystalline state at room temperature, making it impossible to record information. Therefore, if the ambient temperature is likely to be higher than room temperature, the transition temperature should be set to 350, for example.
It is sufficient to set it to about 〓, and for this purpose, 0<x≦
It should be 0.35.

(Effects) As detailed above, in an optical information recording medium that has a base and a thin film formed on the base and records information by irradiating the thin film with a light beam, the thin film is
It is a thin film whose main components are Ge, Pb and Te.
The optical information recording medium, which is characterized by the composition of Ge, Pb, and Te as Ge _1-x PbxTe (0<x≦0.5), can record information with small optical energy and is inexpensive to record and reproduce. High-sensitivity recording can be achieved with the device.

[Brief explanation of drawings]

FIG. 1 shows an example of an apparatus for producing the optical information recording medium of the present invention, and FIG. 2 is a diagram showing the relationship between the composition of the recording medium according to the present invention, the amorphous-crystalline transition point, and the recording light energy. be. 11... Vacuum chamber, 13... Substrate, 14, 15...
...evaporation source.

Claims (1)

[Claims] 1. An optical information recording medium that has a substrate and a thin film formed on the substrate, and records information by irradiating the thin film with a light beam, wherein the thin film is made of germanium, lead,
Ge ₁ −xPbxTe (0<x≦0.5) with tellurium as the main component
An optical information recording medium characterized by having a composition.