JP3372077B2 - Nonlinear optical thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine particle dispersed composite thin film for a non-linear optical material, in a matrix of a ferroelectric material or a high dielectric material used in the field of optical information such as an optical switch and an optical wavelength conversion element. The present invention relates to a thin film of a nonlinear optical material in which metal fine particles are dispersed and deposited.

[0002]

2. Description of the Related Art It has been reported that glass or the like in which semiconductor ultrafine particles are dispersed, glass or colloidal solution in which metal fine particles are dispersed exhibit relatively large non-linear optical characteristics. Of these, quartz glass, multi-component glass, polymer materials, etc. are generally used as the matrix in which the fine particles are dispersed.

For example, glass containing fine gold particles is conventionally called “gold red glass” and is a well-known material as one of red glasses. This glass is made by containing about 0.01 wt% of gold, melting it once, and then heat treating it to develop a color.

The reported third-order nonlinear susceptibility χ ⁽³⁾ of gold-red glass is about 10 ^-11 esu, and this value is not necessarily large. It is considered that the reason for the low value is that the volume fraction of gold in the glass is a low concentration dispersion of about 10 ⁻⁵ . Therefore, increasing the concentration of fine gold particles is considered to be one way to increase the nonlinear susceptibility.
In the case of manufacturing by the melting method, there is a limit to increase the concentration due to the limitation of solubility.

In order to solve this problem, a proposal for a sputtering method or an ion implantation method, which makes it possible to increase the concentration and control the composition relatively easily, was made in the next generation industrial technology / second optoelectronic material symposium proceedings P139-. 147,199
1 and JP-A-3-294829.
The former is one in which Au fine particles are dispersed in a SiO ₂ glass matrix by sputtering or ion implantation.
The latter is made of Au and A grown in the shape of islands with a SiO ₂ glass thin film.
g and Cu metal fine particles are alternately laminated.
It is considered that such a glass with dispersed metal fine particles exhibits a large non-linearity due to the excitation of surface plasmons of the dispersed metal fine particles and the quantum size effect, and a high χ ⁽³⁾ value can be obtained.

It is known that the glass obtained by dispersing metal fine particles thus obtained generally undergoes a heat treatment at about 700 to 1000 ° C. so that the peak of the visible absorption spectrum, that is, the plasma resonance absorption peak position, slightly shifts to the long wavelength side. Has been. The extent to which the peak wavelength shifts and the waveform of the peak differ depending on the heat treatment temperature and heat treatment time,
It is believed that this is due to the difference in the generation and growth of the metal fine particles.

The inventors of the present invention have disclosed, in Japanese Patent Application No. 4-151588 and Japanese Patent Application No. 4-31132, nonlinear optics containing at least one kind of metal fine particles in a ferroelectric or high-dielectric matrix. We propose a thin film. In this proposal, the metal fine particle material and the matrix material are directly formed on the substrate by, for example, the simultaneous sputtering method. Then, by heat treatment after film formation, the grains of the matrix are formed, and the grains grow,
It is considered that the crystallinity of the metal fine particles in the matrix is improved, the three-dimensional dispersibility of the metal fine particles in the matrix is improved, and the crystal particle size distribution of the metal fine particles is made uniform. A high χ ⁽³⁾ value exceeding 10 ^-7 esu can be obtained by this and some interaction caused by the fact that the metal fine particles are dispersed in the matrix having a high dielectric constant ε.

Moreover, by selecting the heat treatment conditions, the plasma resonance absorption peak position can be greatly shifted. By controlling the plasma resonance absorption peak position, the range of selection of the laser used can be widened, and the effect is great.

However, the plasma resonance absorption peak position is adjusted by selecting the heat treatment temperature and the heat treatment time, and at present, it is difficult to finely finely adjust the peak position to a desired wavelength. Therefore, there is a demand for the development of a technique for fine adjustment.

[0010]

SUMMARY OF THE INVENTION The main object of the present invention relates to a nonlinear optical thin film in which metal fine particles are dispersed in a matrix, and the wavelength shift width of the plasma resonance absorption wavelength position can be further widened to achieve a desired excitation. It is to provide a non-linear optical thin film that can be finely adjusted to the wavelength.

[0011]

The above objects are achieved by the present invention described in (1) to (9) below. (1) As a ferroelectric or high-dielectric matrix, at least one kind of metal fine particles is dispersed in a matrix of titanium oxide or a composite oxide containing titanium oxide, and the surface on the upper side and / or the lower side thereof. Non-linear optical thin film in which the content of the fine metal particles in the central part is lower than that in the central part. (2) As a ferroelectric or high-dielectric matrix, a central layer in which at least one kind of metal fine particles is dispersed in a matrix of titanium oxide or a composite oxide containing titanium oxide is formed, and the upper portion and / or A nonlinear optical thin film in which a surface layer of titanium oxide or a complex oxide containing titanium oxide is formed as a surface layer of a ferroelectric or high-dielectric material in contact with the lower part. (3) As a ferroelectric matrix, a perovskite-type compound matrix or a high-dielectric matrix is used to form a central layer in which at least one kind of metal fine particles is dispersed in a matrix of titanium oxide or a composite oxide containing titanium oxide. Membrane and its top and /
Or in contact with the lower part, as a surface layer of a ferroelectric material, a surface layer of a perovskite compound or a surface layer of a highly dielectric material, a surface layer of titanium oxide or a composite oxide containing titanium oxide is formed, The surface layer is a non-linear optical thin film containing the metal fine particles in a content ratio lower than that of the central layer. (4) The non-linear optical thin film according to (2), wherein the surface layer does not contain the metal fine particles. (5) The nonlinear optical thin film according to any one of (2) to (4), wherein the film formation is performed by a sputtering method. (6) The nonlinear optical thin film according to (3), wherein the ferroelectric matrix and / or the material is titanium oxide or a composite oxide containing titanium oxide. (7) The nonlinear optical thin film according to any one of the above (1) to (6), wherein the metal fine particles are contained in an amount of 1 to 80 vol% in the entire thin film. (8) The nonlinear optical thin film according to any one of (1) to (7), wherein the metal fine particles are Au, Ag, Cu or an alloy thereof. (9) The nonlinear optical thin film according to any one of (2) to (8), which is further heat-treated.

[0012]

Among thin films having nonlinear optical characteristics, those using a matrix of a material having a high dielectric constant proposed by the present inventors have three-dimensionally confined fine metal particles as the matrix grows. As a result, for example, the value of the third-order nonlinear susceptibility χ ⁽³⁾ that appears due to the excitation of the surface plasmons of the metal fine particles and the quantum size effect is 10 ⁻⁶ esu or more, which is a large value compared with the conventional one.

Further, by forming a thin film using a matrix of such a material having a high dielectric constant and then heat treating it,
The plasma resonance absorption peak position can be greatly shifted. At this time, since the crystallinity of the metal fine particles and the matrix is changed by controlling the heat treatment temperature and the heat treatment time, it is possible to adjust the plasma resonance absorption peak position.

Such an effect is due to some interaction between the matrix material having a high dielectric constant and the metal fine particles, so that the contact surface between the metal fine particles and the matrix material having a high dielectric constant is increased, and the metal fine particles are formed by the matrix material. It is considered that such an effect is enhanced when it is densely covered.

According to the present invention, even the fine metal particles present on the surface of the thin film and / or the contact surface of the substrate, which have been hard to contact with the matrix material having a high dielectric constant, can be effectively trapped in the matrix of the material having a high dielectric constant. Therefore, such an effect can be further enhanced. At this time, such effect can be finely adjusted by controlling the degree to which the metal fine particles are trapped in the matrix.

[0016]

Specific Structure The specific structure of the present invention will be described in detail below.

The non-linear optical thin film of the present invention is formed by depositing metal fine particles in a ferroelectric or high-dielectric matrix on a substrate, and using this as a central layer, its surface (upper part). ) And / or substrate interface (bottom)
On the side, a portion in which the content of the metal fine particles decreases continuously or continuously in a continuous manner, and further, a portion not containing the metal fine particles is provided on either or both of the surface and the substrate interface. . This may be achieved by coating one or both surfaces of the central layer, preferably with a matrix material. In this case, the term “stepwise” includes not only one step but also a step of changing the content rate of the metal fine particles in at least two steps or more.

In the above-mentioned Japanese Patent Laid-Open No. 3-294829,
It is proposed to alternately deposit island-grown metal particles and an optically transparent substance by a sputtering method, but it is not the one in which the metal particles are dispersed in a ferroelectric or high-dielectric matrix. Therefore, the χ ⁽³⁾ value is also 2 × 10 ^-9 esu at the maximum in the embodiment, which is far lower than about 10 ^-6 esu of the present invention, and a material having a low dielectric constant is used as the matrix. Even if the surface is covered with a matrix material, the effect of shifting the plasma resonance absorption peak position does not occur.

[Thin Film Composition] (Metallic Fine Particles) The metallic fine particles used in the present invention are Au (resonance absorption peak position about 520 nm) and Ag (about 370 n).
m), Cu (about 630 nm) and the like are preferable, but various single metals and alloys can be used and are not particularly limited.
Further, in some cases, two or more kinds of these metals or alloys can be used. These are all according to the present invention,
The plasma resonance absorption peak position shifts by applying heat treatment or forming a surface layer.

= Particle size etc. = The average particle size of such particles is 1 to 100 nm, preferably 2 to 30 nm. The quantum size effect is realized with such an average particle size. The content of fine particles is 1 to 80 vo
It is preferably 1%, particularly 5 to 60 vol%. If the content is too small, the usefulness as a nonlinear optical material is weakened, and if the content is too large, the bulky properties are increased and the optical nonlinearity is reduced. In addition, the average particle size of the fine particle crystals is obtained from a transmission electron microscope (TEM) image,
Alternatively, it can be obtained from the X-ray diffraction spectrum by Scherrer's formula. The content may be determined by chemical analysis, ESCA or the like.

[Distribution of Fine Metal Particles] In the present invention, a portion having a low content of fine metal particles is provided at the surface layer interface (upper part) and / or the substrate interface (lower part) of the film. Such a decrease in the content rate can be realized by changing the film formation speed of the metal fine particle material and the matrix material during film formation stepwise or continuously, for example, when the two-dimensional sputtering is performed. By doing so, the area where the metal fine particles come into contact with a material other than a material having a high dielectric constant is effectively reduced. Therefore, it is considered that the effects of the present invention will appear by controlling this contact area.

= Formation of Underlayer = As a method for forming such a portion where the content of the metal fine particles decreases, the following method can be used. That is, for example, a material having a high dielectric constant is previously sputtered to form a base layer as a surface layer (at this time, the base layer may or may not be subjected to a heat treatment described later), and then the metal fine particles The central layer of the fine particle dispersed matrix is formed simultaneously with the material and the matrix material by multi-source sputtering or the like. At this time, in the vicinity of the interface between the underlayer and the matrix, metal fine particles partially diffuse into the underlayer due to the unevenness of the surface of the underlayer, but a portion having a low metal fine particle content rate is formed. Then, if necessary,
When the heat treatment described later is performed, the interface between the matrix and the underlayer becomes more unclear due to the crystal grain growth of the metal fine particles in the vicinity of the interface with the underlayer formed in advance. By such a method, the metal fine particles that were in contact with the substrate can be covered with the material having a high dielectric constant for the underlayer. After this, heat treatment may be performed. Further, since the amount of change in the plasma resonance absorption peak position is different before and after heat treatment of the central layer of the matrix containing metal fine particles on the underlayer, the heat treatment of the underlayer is It can also be used for fine adjustment of the position.

= Formation of Top Layer = As still another method, for example, a central layer of a fine particle dispersed matrix is formed simultaneously with a metal fine particle material and a matrix material or by a multi-source sputtering method (at this time, the underlayer is May or may not be formed). Then, if necessary, a heat treatment described below can be performed. When the heat treatment is performed, the crystal grain growth of the metal fine particles in the matrix becomes remarkable. Then, a material having a high dielectric constant is laminated by a sputtering method or the like to form a portion where the content of the metal fine particles is reduced near the interface due to the unevenness of the surface of the central layer. By such a method, the metal fine particles exposed on the surface of the central layer can be coated with a material having a high dielectric constant. Such changes in the surface of the central layer can be confirmed by observing the images with an atomic force microscope (AFM). Further, the change in the metal fine particle content of the film in the thickness direction can be confirmed by observing from a transmission electron microscope (TEM) image.

The upper layer thin film of the high dielectric constant material covering the surface of the central layer thus obtained may or may not be subjected to the heat treatment described later. Since the amount of change in the plasma resonance absorption peak position differs depending on whether the heat treatment is performed or not, it can be used for fine adjustment of the wavelength position.

The surface layer of the present invention is realized by stepwise or continuously changing the film formation speed of the metal fine particle material and the matrix material during the film formation, for example, when the two-dimensional sputtering is performed. Alternatively, it may be realized by forming the underlayer or the upper layer as a surface layer, and these may be used in combination. In addition, if the surface layer on the interface of the upper layer is provided as an essential layer, the central layer and, if necessary, the underlayer are formed under appropriate conditions and within the wavelength range of the plasma resonance absorption peak position that can be adjusted in the upper layer. It is preferable that the thin layer whose peak position is controlled can be precisely finely adjusted by the upper layer based on the wavelength measurement result.

(Matrix / Underlayer / Upper Layer Material) The material used for the central layer and surface layer of the present invention is a ferroelectric or high-dielectric material. A ferroelectric material is a bulk polycrystal having a dielectric constant of about 150 or more at room temperature, and a high-dielectric material is a bulk polycrystal having a dielectric constant of 10 or more and less than 150 at room temperature. It is of a degree. It is considered that the dielectric constant of these changes due to the heat treatment after the film formation described later, and as a result, the resonance absorption position shifts significantly.

= Ferroelectric or High-Dielectric Material = Such a ferroelectric material is a perovskite type compound. As the perovskite type compound, A ¹⁺ B
_{^{5+ O 3, A 2+ B 4+}} O 3, A 3+ B 3+ O 3, A X BO 3, A
(B ′ _0.67 B ″ _0.33 ) O ₃ , A (B ′ _0.33 B ″ _0.67 ) O
₃ , A (B _0.5 ⁺³ B _0.5 ⁺⁵ ) O ₃ , A (B _0.5 ²⁺ B _0.5
⁶⁺ ) O ₃ , A (B _0.5 ¹⁺ B _0.5 ⁷⁺ ) O ₃ , A ³⁺ (B _0.5
²⁺ B _0.5 ⁴⁺ ) O ₃ , A (B _0.25 ¹⁺ B _0.75 ⁵⁺ ) O ₃ , A
(B _0.5 ³⁺ B _0.5 ⁴⁺ ) O _2.75 , A (B _0.5 ²⁺ B _0.5 ⁵⁺ )
It may be O _2.75 or the like. For example, BaTiO
₃ , PbTiO ₃ , KTaO ₃ , NaTaO ₃ , SrT
iO ₃ , CdTiO ₃ , KNbO ₃ , LiNbO ₃ , L
iTaO ₃ , PZT (PbZrO ₃ -PbTiO ₃ ),
_{PLZT (PbZrO 3 -PbTiO 3: La} 2 O 3)
Etc.

Further, as the high dielectric material, TiO ₂ , 2
MgO / TiO ₂ , MgO / TiO ₂ , MgO / 2Ti
_{O 2, ZnO-TiO 2,} CaTiO 3 or the like are preferable. The high dielectric material is titanium oxide or a composite oxide containing titanium oxide (titanate), and the ferroelectric material is titanium oxide or a composite oxide containing titanium oxide (titanate). Suitable as these ferroelectric or high-dielectric materials are, in particular, titanate perovskite type compounds having a dielectric constant of about 100 to 300 at room temperature for bulk polycrystals, such as BaTiO ₃ and Sr.
TiO ₃ , CaTiO ₃ , PbTiO _{3 and the} like are preferable.

As the material used for the central layer and the surface layer of the present invention, two or more kinds of such materials can be used if necessary. Further, different materials may be used for the central layer and the base layer, and for the central layer and the upper ground layer. At this time,
The amount of change in the plasma resonance absorption peak position can be changed by using materials having different permittivities as the materials used for the underlayer or the upper layer.

= Microstructure = No clear peak is observed in the X-ray diffraction spectrum (XRD) of the central layer, the underlayer and the upper layer of these ferroelectric or high-dielectric materials immediately after film formation and after heat treatment. , Substantially in an amorphous state. However, in observation with a transmission electron microscope (TEM), grains are usually observed after heat treatment. At this time, the average grain diameter is 40 to
1000 nm, especially 100-500 nm.

= Thickness = The thickness of the central layer thin film in which fine particles are dispersed in such a matrix is generally about 0.01 to 10 μm, more preferably about 0.01 to 0.1 μm. If the central layer thin film is too thick, the transmittance of the film is reduced and the non-linear optical characteristics are deteriorated. On the other hand, if it is too thin, the fine metal particles do not grow normally in the matrix, and the nonlinear optical characteristics cannot be obtained normally.

Further, the film thickness of the upper layer and the underlayer thin film is
0.2 μm or less, preferably 0.005 to 0.1 μ
It is about m. These thin films are expected to enhance the interaction between the metal fine particles and the material having a high dielectric constant by coating the exposed portions of the metal fine particles above the central layer. That is, for example, by controlling the film thickness of the upper layer or the underlayer, the shift amount of the plasma resonance absorption peak position can be controlled. Therefore, even if the film thickness required to cover the exposed metal fine particles is greatly exceeded, the wavelength shift effect is small. In this way, when providing a portion in which the content of the metal fine particles is lowered as the upper layer or the underlayer, the content of the metal fine particles in these surface layers is about ½ or less of the central layer, and further 0 to 1/10 or less. It is preferable to set the degree. However, the surface layer thus formed may not be clearly discriminated.

[Manufacturing Method] Various methods can be used for forming the central layer of the present invention, such as alternate sputtering of a matrix material and metal fine particles, multi-source sputtering of a matrix material and metal fine particle materials, and the like. Although possible, it is preferable to perform co-sputtering with the matrix material and the metal fine particle material as targets, from the viewpoint of productivity.
It is also preferable to use the sputtering method for forming the upper layer and the underlayer. Although any method may be used as the sputtering method, the RF magnetron sputtering method is preferable from the viewpoint of film forming speed and the like. At this time, the operating pressure is 1
The substrate temperature is about 0 ⁻³ to 10 ⁻² Torr and the substrate temperature is about room temperature to 300 ° C. Then, the content of the metal fine particles can be changed by changing the amount of the metal chips, and a surface layer in which the content rate of the metal fine particles is controlled in the thickness direction of the film can be obtained.

Further, as the film forming substrate used in the present invention,
For example, a synthetic quartz glass substrate or the like usually used for such purpose can be used. At this time, in particular, when a substrate having a uniaxially oriented surface is used on the surface, the heat treatment described later causes the grains of the matrix material to grow grains, improving the crystallinity of the metal fine particles in the matrix, and further increasing the crystal grain size. A large and uniform particle size can be obtained. As such a substrate material, α-Al ₂ O ₃ ,
Si, Ge, GaAs, MgO, MgO-Al ₂ O _{3 and the} like can be mentioned.

(Heat Treatment) In the present invention, the plasma resonance absorption peak position can be largely changed by performing heat treatment in order to adjust the crystallinity and the crystal grain size of the metal fine particles dispersed in the matrix. . This heat treatment is generally performed at 100% in the atmosphere or an inert gas atmosphere.
2 ° C or higher, particularly 300 ° C or higher, further 500 ° C or higher, generally 1100 ° C or lower, particularly 1000 ° C or lower
It may be carried out by holding for about 0 hour or less, generally for 1 minute or more, and particularly for 10 minutes or more.

In addition to the heat treatment method under the above conditions,
The heat treatment immediately after film formation includes a step of rapidly raising the temperature by irradiating an active energy ray with a laser or the like and then rapidly cooling, and the quenching rate at the time of quenching is 10 ³ ° C / sec or more, generally 10 ⁷ ° C / second. It can also be performed by performing flash annealing for about a second or less.

Also, for the upper layer or the underlayer, such heat treatment can be carried out simultaneously with the central layer or separately, if necessary.

In the central layer of the present invention, a nonlinear optical thin film having a peak wavelength close to a desired plasma resonance absorption peak position can be obtained by selecting such conditions as heat treatment temperature and heat treatment time. Furthermore, for example, Sr
As in the case where TiO ₃ is used as a matrix material, a material having a plasma resonance absorption peak does not have to be heat-treated as necessary even without the heat treatment as described above. However, it is difficult to precisely set the plasma resonance absorption peak position only by selecting such heat treatment conditions, and variations in the peak positions occur due to subtle differences in conditions during manufacturing.

[Characteristics] (Plasma resonance absorption peak position adjusting function) As described above, in the present invention, in order to obtain a nonlinear optical thin film in which the plasma resonance absorption peak position is set to a desired wavelength, the wavelength is first largely shifted. If necessary, a heat treatment that has the effect of, but is not precisely controlled is used. By appropriately setting the heat treatment conditions, it is possible to obtain a wavelength approximate to a desired peak position.

At this time, the amount of change in peak position is further increased by previously providing a portion having a low content of metal fine particles, preferably a layer containing no metal fine particles, on the upper or lower part of the central layer as the surface layer. By providing such a portion in both the upper and lower portions, this change amount is further increased.

Further, by providing such a portion in which the content of the metal fine particles is lower than that in the central portion, particularly at the upper portion, it is possible to further finely adjust the peak position after the heat treatment.
That is, when the peak position of the nonlinear optical thin film obtained as a result of heat treatment or the like before providing the upper layer requires further fine adjustment, a material having a high dielectric constant is selected on this thin layer to form the upper layer. May be laminated. At this time, by selecting the film thickness of the thin film to be laminated and the heat treatment conditions, including those without heat treatment, it is possible to set finer conditions.

The relationship between such several factors for adjusting the plasma resonance absorption peak position and the amount of change in the peak position may be experimentally obtained in each case.

(Dielectric constant) The nonlinear optical thin film of the present invention using a ferroelectric or high dielectric material generally exhibits a dielectric constant ε of 10 or more, and particularly 100 or more, further 150 or more,
Further, it can be 200 or more. To measure the dielectric constant of such a thin film, a synthetic quartz glass substrate,
A platinum thin film lower electrode is formed by a sputtering method, a thin film to be measured is formed on the lower electrode, and a platinum film 1 is formed on the lower electrode.
A pad upper electrode of mmφ is formed, and then heat treatment is performed if necessary. Then, C and Q are measured using an LF impedance analyzer, and from this, ε can be calculated.

(Χ ⁽³⁾ value) Further, the χ ⁽³⁾ value of the element using such a ferroelectric material or high dielectric material is
By controlling the grain growth of the contained metal fine particles, maximum 1
It is possible to obtain 0 ^-7 esu or more, particularly 10 ^-6 esu or more. Such a high χ ⁽³⁾ value can be obtained because the concentration of the metal fine particles dispersed in the matrix is high, the dielectric constant of the matrix material used is high, and the dispersed metal fine particles are This is probably because the area in contact with the matrix material having a high dielectric constant is large. Note that χ
^The value ⁽³⁾ can be measured according to the phase-conjugated degenerate four-wave mixing method (DFWM) described in the above-mentioned Proceedings of the Symposium on Optoelectronic Materials. The above χ ⁽³⁾ value is Nd:
Second harmonic (532n) of YAG laser (1.06μm)
m) is used, not the value at the plasma resonance absorption peak position, so χ ⁽³⁾ at this plasma resonance absorption peak wavelength is in the range of 10 ^-7 esu or more, especially 10 ^-6 esu or more. It will be even higher.

[0045]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 Using an RF magnetron sputtering apparatus, an Au chip was placed on a SrTiO ₃ target, and a central layer was formed by co-sputtering. A synthetic quartz glass was used as the substrate. The RF power was 100 W and the degree of vacuum was 5 mTorr. Au
The concentration was controlled by the amount of chips. The film thickness was controlled to 150 A by controlling the sputtering time. In addition, A of the obtained central layer thin film
The u-containing concentration was 14 vol%.

The obtained central layer thin film was subjected to 9
Heat treatment was performed at 00 ° C. for 1 hour. In the heat treatment method, the temperature rising speed was set to 900 ° C./1 hour, the temperature was kept at 900 ° C. for 1 hour, and then allowed to cool.

After the heat treatment, an upper layer was formed on the SrTiO ₃ target using an RF magnetron sputtering device under the same conditions as the formation of the central layer. The film thickness is 150
A.

Regarding the obtained thin film (Sample No. 11),
Using a spectrophotometer, the respective plasma resonance absorption peak positions were measured after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed. The values obtained are summarized in Table 1.

[0050]

[Table 1]

Furthermore, the spectrum of the absorption peak obtained by the spectrophotometer is shown in FIG. 1, and the spectrum obtained by the X-ray diffraction method is shown in FIG. 1 and 2
In the figure, 1 indicates the spectrum after the central layer is formed, 2 indicates the spectrum after the central layer is heat-treated, and 3 indicates the spectrum after the upper layer is formed.

Example 2 The same process as in Example 1 was carried out except that the thickness of the central layer was 300A. About the obtained thin film (Sample No. 12),
Using a spectrophotometer, the respective plasma resonance absorption peak positions were measured after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed. The values obtained are summarized in Table 1.

Example 3 The same treatment as in Example 2 was carried out except that the heat treatment was not applied to the central layer. With respect to the obtained thin film (Sample No. 13), the plasma resonance absorption peak positions after the center layer formation and after the upper layer formation were measured using a spectrophotometer. The values obtained are summarized in Table 1.

Example 4 The same process as in Example 2 was carried out except that the SrTiO ₃ target was changed to the BaTiO ₃ target. With respect to the obtained thin film (Sample No. 21), the plasma resonance absorption peak positions after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed were measured using a spectrophotometer. The values obtained are summarized in Table 1. However, in this sample, a clear plasma resonance absorption peak was not obtained after the central layer was formed (before the heat treatment).

Further, the spectrum of the absorption peak obtained by the spectrophotometer is shown in FIG. 3, and the spectrum obtained by the X-ray diffraction method is shown in FIG. 3 and 4
In the figure, 1 indicates the spectrum after the central layer is formed, 2 indicates the spectrum after the central layer is heat-treated, and 3 indicates the spectrum after the upper layer is formed.

Example 5 After the same treatment as in Example 4, a heat treatment was further performed under the conditions described in Example 1. For the obtained thin film (Sample No. 22), the plasma resonance absorption peak positions were measured using a spectrophotometer after the central layer was formed, after the central layer was heat-treated, after the upper layer was formed and after the upper layer was heat-treated. . The values obtained are summarized in Table 1.

Example 6 The same process as in Example 1 was carried out except that the target for forming the central layer was SrTiO ₃ and the target for forming the upper layer was BaTiO ₃ . With respect to the obtained thin film (Sample No. 31), the positions of the plasma resonance absorption peaks after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed were measured using a spectrophotometer. The values obtained are summarized in Table 1.

Example 7 The same process as in Example 1 was carried out except that BaTiO ₃ was used as the target for forming the central layer and SrTiO ₃ was used as the target for forming the upper layer. With respect to the obtained thin film (Sample No. 41), the plasma resonance absorption peak positions after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed, were measured using a spectrophotometer. The values obtained are summarized in Table 1.

Comparative Example 1 A central layer was formed in the same manner as in Example 1, and after heat treatment, the target was changed from SrTiO ₃ to SiO ₂ and an upper layer having a film thickness of 300 A was formed. With respect to the obtained thin film (Sample No. 51), the plasma resonance absorption peak positions after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed, were measured using a spectrophotometer. The values obtained are summarized in Table 1.

Comparative Example 2 The same process as in Comparative Example 1 was performed except that the target at the time of forming the central layer was BaTiO ₃ . Obtained thin film (Sample No. 5
Regarding 2), using a spectrophotometer, the respective plasma resonance absorption peak positions were measured after the central layer was formed, after the central layer was heat-treated, and after the upper layer was formed. The values obtained are summarized in Table 1.

Example 8 An underlayer having a film thickness of 300 A was formed on a synthetic quartz glass substrate under the same sputtering conditions as in Example 1 except that the target was SrTiO ₃ . Then, an Au chip was placed on a SrTiO ₃ target and a central layer was formed by co-sputtering on the obtained underlayer in the same manner as in Example 1.

The obtained thin film was heat-treated under the conditions described in Example 1. Obtained thin film after heat treatment (Sample No. 6
Regarding 1), the plasma resonance absorption peak positions after the central layer was formed and after the central layer was heat-treated were measured using a spectrophotometer. The values obtained are summarized in Table 2.

[0063]

[Table 2]

Example 9 An underlayer having a thickness of 300 A was formed on a synthetic quartz glass substrate under the same sputtering conditions as in Example 1 except that the target was SrTiO ₃ . This underlayer was heat treated under the conditions described in Example 1. Then, on the underlayer after the heat treatment, Au was formed on the SrTiO ₃ target as in Example 1.
A chip was placed and a central layer was formed by co-sputtering.

The thin film obtained here was further heat-treated under the conditions described in Example 1. With respect to the obtained heat-treated thin film (Sample No. 62), the plasma resonance absorption peak positions after the center layer was formed and after the center layer was heat-treated were measured using a spectrophotometer. The values obtained are summarized in Table 2.

Example 10 Among the targets for forming the underlayer and the central layer, SrT
In addition to changing the iO ₃ to BaTiO ₃ was deposited under the same conditions as in Example 8. Obtained thin film after heat treatment (Sample No. 7
Regarding 1), the plasma resonance absorption peak positions after the central layer was formed and after the central layer was heat-treated were measured using a spectrophotometer. The values obtained are summarized in Table 2.

Example 11 Of the targets for forming the underlayer and the central layer, SrT
In addition to changing the iO ₃ to BaTiO ₃ was deposited under the same conditions as in Example 9. Obtained thin film after heat treatment (Sample No. 7
Regarding 2), the positions of the plasma resonance absorption peaks after the formation of the central layer and after the heat treatment of the central layer were measured using a spectrophotometer. The values obtained are summarized in Table 2.

Example 12 SrTiO ₃ was used as the target for forming the underlayer, and SrTiO ₃ was BaTiO ₃ among the targets for forming the central layer.
_A film was formed under the same conditions as in Example 9 except that the number was changed to ₃ . With respect to the obtained heat-treated thin film (Sample No. 81), the respective plasma resonance absorption peak positions after the center layer was formed and after the center layer was heat-treated were measured using a spectrophotometer. The values obtained are summarized in Table 2.

Example 13 A film was formed in the same manner as in Example 9 except that BaTiO ₃ was used as the target for forming the underlayer. With respect to the obtained heat-treated thin film (Sample No. 91), the plasma resonance absorption peak positions after the center layer was formed and after the center layer was heat-treated were measured using a spectrophotometer. The values obtained are summarized in Table 2.

Among the samples thus obtained, the thin film of which the central layer was subjected to heat treatment had a χ ⁽³⁾ value of 10 ^-7 to 10 ^-6 esu as a result of measurement by the above-mentioned measuring method.

[0071] As shown in Table 1, by providing the formation on the ferroelectric or high-dielectric material in the middle layer, plasma resonance absorption peak position further shifted, but those having a formation on the SiO ₂ is Do not shift. Further, the effect of providing the underlayer shown in Table 2 was compared between the plasma absorption peak positions of Sample Nos. 61 and 62 and the plasma absorption peak positions of the central layer of Sample No. 11 before and after heat treatment. At this time, the film thickness of the central layer is the same, but it is further shifted by providing the base layer (regardless of the heat treatment).
This tendency is due to Sample Nos. 71 and 72 with different compositions and Sample N.
The same is true for o. 21 or 22. That is, it is understood that the shift width is further changed by providing the base layer.

[0072]

The present invention relates to a nonlinear optical thin film in which metal fine particles are dispersed in a matrix, and the wavelength shift width of the plasma resonance absorption peak position can be further widened, and fine adjustment to a desired excitation wavelength can be achieved. A non-linear optical thin film that can be provided can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of heat treatment and an upper layer on the transmission absorption spectrum of a SrTiO ₃ —Au thin film (Sample No. 11).

FIG. 2 is a graph showing the effects of heat treatment and an upper layer on the X-ray diffraction spectrum of a SrTiO ₃ —Au thin film (Sample No. 11).

FIG. 3 is a graph showing the influence of heat treatment and upper layer on the transmission absorption spectrum of a BaTiO ₃ —Au thin film (Sample No. 21).

FIG. 4 is a graph showing the effects of heat treatment and an upper layer on the X-ray diffraction spectrum of a BaTiO ₃ —Au thin film (Sample No. 21).

Continuation of the front page (56) Reference JP-A-3-296026 (JP, A) JP-A-3-69512 (JP, A) JP-A-5-323398 (JP, A) K. FUKUMI, Au + -Ion- Implanted Silica G glass with non-Linear Optical Property, JAPANESE JOURNAL OF APPLIED PHYSICS, Vol. 30, No. 4B, L742-L744 (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/35-1/39 JISST file (JOIS)

Claims (9)

(57) [Claims] 1. As a ferroelectric or high-dielectric matrix, at least one kind of metal fine particles is dispersed in a matrix of titanium oxide or a composite oxide containing titanium oxide, and its upper side and / or lower side. A non-linear optical thin film in which the content of the metal fine particles in the surface portion of the is lower than that in the central portion. 2. As a ferroelectric or high-dielectric matrix, a central layer in which at least one kind of metal fine particles is dispersed in a matrix of titanium oxide or a composite oxide containing titanium oxide is formed, and the upper portion and A non-linear optical thin film in which a surface layer of titanium oxide or a complex oxide containing titanium oxide is formed as a surface layer of a ferroelectric or high-dielectric material in contact with the lower part. 3. A central layer in which at least one kind of metal fine particles is dispersed in a matrix of a perovskite type compound as a ferroelectric matrix or a matrix of a high dielectric constant titanium oxide or a composite oxide containing titanium oxide. And a titanium oxide or a composite containing titanium oxide as a surface layer of a ferroelectric material, a surface layer of a perovskite-type compound or a surface layer of a high dielectric material in contact with the upper and / or lower portions of A non-linear optical thin film formed by forming a surface layer of an oxide, wherein the surface layer contains the metal fine particles in a content ratio lower than that of the central layer. 4. The nonlinear optical thin film according to claim 2, wherein the surface layer does not contain the metal fine particles. 5. The nonlinear optical thin film according to claim 2, wherein the film formation is performed by a sputtering method. 6. The nonlinear optical thin film according to claim 3, wherein the ferroelectric matrix and / or material is titanium oxide or a composite oxide containing titanium oxide. 7. The metal fine particles are contained in an amount of 1 to 80 vo over the entire thin film.
The nonlinear optical thin film according to claim 1, wherein the nonlinear optical thin film is contained in an amount of 1%. 8. The nonlinear optical thin film according to claim 1, wherein the fine metal particles are Au, Ag, Cu or an alloy thereof. 9. The nonlinear optical thin film according to claim 2, which is further heat-treated.