JP2577851B2 - Organic superlattice optoelectronic device and its manufacturing method. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic superlattice optoelectronic device, and more particularly to an organic superlattice optoelectronic device having nonlinear optical effects such as light mixing, optical parametric oscillation, optical harmonic generation, Pockels effect, and Kerr effect. .

[0002]

2. Description of the Related Art A superlattice is, for example, an MBE (Molecular).
The Beam Epitaxy) method or ALE (AtomicLayer Epitaxy) method or the like thin film formation technology, 10 ~ ⁹ Torr or less under a clean environment under ultrahigh vacuum, any atomic ratio of inorganic semiconductor such as GaAs on Si substrate Is defined as a material system in which the heterojunction of different structures is repeated by epitaxial growth and forms a non-natural atomic or molecular superstructure, thereby artificially changing the electronic state of the material or its wave function. (Supervised by Reona Ezaki, edited by Hiroyuki Sakaki, “Superlattice heterostructure device”).

The first idea for a semiconductor superlattice was 196
From 9 to 1970, IBM's then Esaki
And Tsu [L. Esaki and R. Tsu, "S
uperlattice and negative conductivity in semicondu
ctors ", IBM Research Note (1969), RC-2418 and the same title, IBM J. Res. Develop. 14 , 61 (1970)].

In the 1970s, MBE, MOCVD (Meta
lorganic Chemical VaporDeposition), MOMBE (M
etalorganic Molecular Beam Epitaxy, CBE: Chemica
Advances in thin film growth technologies such as l Beam Epitaxy) have made it possible to fabricate extremely high-quality heterojunctions, resulting in high electron mobility transistors (HEMTs).
ron Mobility Transistor), Hetero Bipolar Transistor (HBT), Resonant Tunneling Diode, Quantum Well Laser, Optical Bistable Device (SEED: Self-Electro-optic Effect Device, CS)
F-OB: Charge-induced Self Feedback Optical Bis
Many superlattice devices, such as table devices, have been proposed.

[0005] In recent years, research on superlattice devices made of such inorganic semiconductors has been conducted to reduce the dimensionality of a conventional two-dimensional quantum well structure using a planar heterojunction by using a high-definition lithography technique and a fine particle dispersion technique. The interest is shifting to the realization of quantum well wires (one-dimensional) and quantum well boxes (zero-dimensional).

On the other hand, research on the improvement of physical properties of heterojunction thin films made of organic molecules has been started mainly on organic semiconductor thin films since the 1960s [F. Gutmann and L. et al.
E. Lyons, "Organic Semiconductors", John Wiley & So
ns, Inc. (1967)].

[0007] In the case of an inorganic crystal such as silicon or germanium, the energy level of one semiconductor layer is represented by a band structure in which the atomic orbitals of each atom constituting the crystal are overlapped by the periodic structure of the crystal. In the ground state, the valence band filled with electrons and the conduction band thereabove are separated by a certain band gap. Junctions of different semiconductors cause band discontinuities at their boundaries, and such junctions are repeated to form band confinement structures (ie, quantum wells or tunnel barriers). The confined band shows a wave function like a single isolated atom.

In the case of a crystal composed of organic molecules, one complete molecular orbital is formed in one molecule, but the entire crystal is a weak molecular crystal composed of van der Waals force, and the interaction between molecules is weak. , The bandwidth is narrow and the energy gap is larger than that of the semiconductor. Therefore, ordinary organic crystals are insulators (electric conductivity is 10 to ¹⁰ Ω to ¹ c).
m ~ ¹ or less in many ^{10 ~ 20 ~10 ~ 14 Ω ~} 1 cm ~ 1), no reforming of electronic properties even heterojunction such organic molecules.

Therefore, in order to form a superlattice from organic molecules, it is necessary to enlarge the molecule and expand the molecular orbital to a size where one molecule can be regarded as one quantum box or quantum wire, or to perform some kind of intermolecular interaction. To create a band structure in the crystal.

As an example of the former, a one-dimensional conjugated polymer such as polyacetylene and polydiacetylene and a planar conjugated molecule such as porphyrin and phthalocyanine show the electrical characteristics of the semiconductor region (electric conductivity 10 to ⁹ to 10).
~ ⁵ Ω ~ ¹ cm ~ ¹ ), examples of the latter include semiconductors such as dopant-type hetero films such as poly-p-phenylene / iodine and charge transfer complex crystals such as tetrathiafulvalene / tetracyanoquinodimethane. It is known that the region exhibits electrical characteristics from the region to the conductor region (electric conductivity of 10 to ⁴ to 10 ⁴ Ω to ¹ cm to ¹ ).

However, in these early studies on organic semiconductors, the purity was lower than that of inorganic semiconductors, and process techniques such as single-crystal fabrication and thin-film fabrication by vacuum evaporation were inexperienced. The properties are poor, and there are problems such as a drastic change in electrical characteristics due to the influence of moisture and oxygen in the air, and significant deterioration of the sample.

As a method for controlling the molecular orientation of the organic molecular thin film more completely, in addition to a dry process such as the above-described vacuum deposition method, a solvent evaporation method, a spin coating method,
Wet processes such as the Langmuir-Blodgett film method are being studied. Among them, Langmuir-Blodgett method is the only method that can control the arrangement at the molecular level, because the thin film of molecular order can be formed and the arrangement control in the direction of the thin film layer can be performed. From the beginning of the same age [FL Carter, "Molecular Electronic Devi
ces ", Marcel (1982).

However, in this method, since the molecular arrangement at the gas-liquid interface is used, solvent molecules are mixed in the film, the order within the thin film cannot be obtained, and a long distance due to the molecular arrangement is required. There is a problem that an intermolecular interaction in a layer direction cannot be achieved because an alkyl chain is required in the molecule.

On the other hand, as a technique for forming a multilayer of an organic thin film, there is a film forming technique by laminating a functional polymer film. However, with this method, it is difficult to control the arrangement at the molecular level, and it is not possible to form a multilayer film with a quantum size that exhibits superlattice properties.

[0015] Since the late 1980's, MBE (Molecula
r Beam Epitaxy) technology to make organic molecules extremely clean
Research on epitaxial growth under active conditions has been actively conducted,
Ultra-thin film made by MBE method is extremely uniform and high quality
[J. C. Buchholz and G. A. Som
orjai, J. Chem. Phys.66, 573 (1977): M. Komiyama,
 Y. Sakakibara, and H. Hirai, Thin Solid FilmsFifteen
1, L109 (1987): A. Yamada, K. Shigehara, and M.H.
ara, Synth. Met.18, 821 (1987): M. Hara, H. Sas
abe, A. Yamada, and A. F. Garito, Jpn. J. Appl. Ph
ys.28, L306 (1989)). Many are phthalocyanines
Of epitaxial compounds on various crystalline substrates
Related to the consideration of the matter.

In the 1990's, it has been confirmed that many other organic molecules are epitaxially grown on an alkali halide substrate or a MoS ₂ substrate [Hiroichi Tada,
Atsushi Koma, “Chemistry and Industry” 44 , 2109 (1991)
)], And remarkable improvements in various characteristics which have been inferior due to poor film quality are expected.

As a result of the progress of the vacuum deposition technique, the production of a hetero-epitaxial structure of organic molecules, which has been imperfect, has been increasingly active since 1991. For example, a report on the relationship between fluorescence lifetime and film thickness for perylene / naphthalene hetero films [FF So and SR For
rest, Phys. Rev. Lett. 66, 2649 (1991)] and confirmation of the artificial periodic structure of the pentacene / hexacene heteromembrane [Hiroshi Akimichi, Hiroyuki Sakaki, "Creative Science and Technology Promotion Project '91 Research Report No.2" , "Public Lecture Abstracts," p. 69, New Technology Agency (1991)]. With the advance of such a technique of forming a hetero thin film by a dry process of organic molecules, the concept of a superlattice composed of organic molecules is being studied.

[0018]

As described above, in the case of a conventional thin film optical device having a simple ultra-thin layered structure composed of organic molecules, the film quality of a single kind of thin film itself is imperfect, and Growth techniques such as control of the molecular orientation of GaN and control of epitaxial growth between a substrate and a thin film have also been incomplete. Further, the structure of the obtained thin film is equivalent to that of a bulk crystal and does not employ an artificial lattice structure, and the electronic state of the molecular assembly having such a structure cannot be modulated.

In order to realize the organic superlattice technology, it is necessary to examine issues such as a model of the material system, quantum mechanical considerations, superlattice structure fabrication technology and characterization, and evaluation of optical and electronic properties peculiar to the superlattice structure. Although there is
There was no study on organic ultrathin film devices that examined the superlattice properties of organic molecules.

Therefore, what will characterize the optical and electronic properties of the superlattice will be summarized based on a review article [Physics and Application of Semiconductor Superlattice, edited by The Physical Society of Japan, Baifukan (1984)].

The superlattice is realized by a heteroepitaxial junction of semiconductor compounds having different electronic states. The energy level of one semiconductor layer is represented by a band structure in which the atomic orbitals of each atom constituting the crystal are superimposed by the periodic structure of the crystal. Among them, the valence band filled with electrons in the ground state and the conduction band above it are
They are separated by a constant band gap.

Therefore, electrons are put into the conduction band, or
When holes are created by removing electrons from the valence band,
These electrons or holes have an effective mass m
With [electron (electron)] or m [hole (hole)], it moves around the crystal relatively freely. Junctions of different semiconductors cause band discontinuities at their boundaries, and such junctions are repeated to form band confinement structures (ie, quantum wells or tunnel barriers). The confined band shows a wave function like a single isolated atom.

The electronic state of such a superlattice has four parameters, ie, the discontinuity magnitudes ΔEc and ΔEv of the energy band in the conduction band and the valence band at the heterointerface of the two semiconductors, the quantum well and the tunnel barrier. Width Lw,
It is characterized by Lb.

First, the tunnel barrier width Lb is infinite and the height Vo is
Consider the case of a single quantum well (Vo = ΔEc or ΔEv). The electrons in the well behave as free electrons having wave vectors kx and ky in a plane (x, y) perpendicular to the well, but there is a potential barrier of Vo in the direction (z) along the well and the electrons are in the well. Localized near, the wave function decreases exponentially. Therefore, when the height Vo is sufficiently high, the energy eigenvalue En in this direction is

[0025]

(Equation 1)

## EQU2 ## Here, n is a quantum number (n =
, Π is the pi, h is the Plank constant, and m is the effective mass of electrons. Therefore, the total energy of the electron is

[0027]

(Equation 2)

## EQU1 ## This is because the total energy of electrons in a bulk crystal without quantum confinement is

[0029]

(Equation 3)

In comparison with the above, it can be seen that the electronic state that was continuous in the bulk becomes discrete in the quantum well.
Here, p is the momentum of the electron, and de Brol of the electron.
ie, the wavelength λ is related to λ = h / p. Therefore, in order for the energy level to be discrete and the quantum effect to be significant, the following equation must be satisfied.

[0031]

Lw ≦ λ Next, consider the case where the tunnel barrier width Lb is reduced. At this time, the wave functions in adjacent quantum wells overlap,
When the well-type potential exists alone, the degenerated quantum level splits by a tunnel effect to form a mini-band (or sub-band). In a superlattice composed of semiconductor GaAs and AlGaAs, a GaAs layer and an AlG
Since the unit lattice is formed in the aAs layer, the length of the periodicity in the real space is repeated as Lb + Lw, and the first Brill is repeated.
The size of the ouan area is 2π / (Lb + Lw).

In the case of a bulk crystal, the unit lattice size a is about the lattice interval. If this semiconductor superlattice is composed of 10 layers of GaAs and 10 layers of AlGaAs, Lb + Lw is 2
0a, and the size of the first Brillouin region of the superlattice is 1/20 of the size 2π / a of the bulk crystal.
About. Therefore, the band structure of the bulk crystal is 2π
In response to the energy band being folded at a period of / a, the energy band is folded at smaller intervals of 1/20 to form a mini band.

From the above, it can be seen that changing the quantum well width Lw and the tunnel barrier width Lb can greatly change the electronic state of the superlattice system. In particular, when Lw is set to be equal to or less than the deBroli wavelength, the quantum effect becomes remarkable (about 300 ° in the case of GaAs).

When Lw is made sufficiently thicker than Lb, electrons can be confined, and when Lb is made sufficiently thin, a mini band is formed (several hundred degrees or less). If Lw is less than a few atomic layer thickness of 10 ° or less, the Kronig-Penny model using the electronic structure of the bulk crystal cannot be used, and band calculation with a large unit cell is required.

In the case of a crystal composed of organic molecules, one complete molecular orbital is formed in one molecule, but the entire crystal is a weak molecular crystal composed of van der Waals force, and the interaction between molecules is weak. , The bandwidth is narrow and the energy gap is larger than that of the semiconductor. Further, when the above-described model of the semiconductor superlattice is applied, one molecule is a quantum well and each quantum well is in an isolated state due to poor intermolecular interaction.

Therefore, in order to form a superlattice from organic molecules, it is necessary to enlarge the molecule and expand the molecular orbital to a size where one molecule can be regarded as one quantum box or quantum wire, or to perform some kind of intermolecular interaction. To create a band structure in the crystal. Furthermore, in an organic molecule, a molecule is formed by a combination of a plurality of atoms, and the electron distribution of the entire molecule forms a molecular orbital unique to the molecule and has anisotropy. For this reason, the arrangement of the molecular aggregate together with the molecular orbital of one molecule greatly affects the physical properties of the whole substance. That is, the design of the organic superlattice involves selection of molecular species, control of the electronic state of each molecule,
A molecular aggregate called a superlattice cannot be formed without taking into account control of molecular orientation, optimization of molecular layer thickness, and the like.

In order to solve the above-mentioned problems, the present invention provides a molecular orientation and a superlattice structure design guideline which have been overlooked in a thin film optical element having a laminated structure of an organic thin film, and a specific production method thereof. It intended to provide a technique, and an object thereof is to provide an organic superlattice optoelectronic device comprising a stacked structure of an organic thin film.

Another object of the present invention is to provide a method for producing the above-mentioned organic superlattice optoelectronic device.

[0039]

The gist of the present invention for solving the above problems is as follows.

(1) An organic superlattice optoelectronic device comprising a medium which can be modulated by light in / out, charge injection or electric and magnetic fields, wherein the device is composed of two or more kinds of organic ultrathin films on a single crystal substrate. Haitai that the layer periodically epitaxial multilayer
An organic superlattice optoelectronic device having a roepitaxial structure.

[0041] (2) said organic ultra-thin layer comprises two or more organic film, and, even more of the thickness of the thin film 1-1000
A Å, phase repetition number lamination of different thin film layer is formed on at least three layers organic superlattice optoelectronic device.

[0042] (3) the organic ultra-thin layer comprises two or more organic film, and a layer of the thickness of the thin film is 1 to 100 molecular layers, repetition number of layers of different thin film layers are at least 3 organic superlattice optoelectronic device that is configured in the layer.

[0043]

[0044] (4) the effect before Kieu machine ultra-thin film layer is outside of
The electronic state when not receiving, single binding forming the ultra-thin
An organic superlattice optoelectronic device modulated by a crystal substrate or another ultrathin film layer on the substrate .

[0045] (5) before Kieu ultrafine thin layer of some or organic superlattice optoelectronic element provided with an electrode that moves the electric field applied or charges in the vicinity thereof.

The molecular orientation aggregate structure in which the orientation state or electronic state of the organic molecules constituting the thin film layer is modulated by the above-mentioned electric field application or charge transfer.

[0047] The modulation of the electron state of the molecules referred to herein, by laminating the lamination and different molecules each other molecules on the substrate surface, formation of the new bond in the hetero interface vicinity, charge transfer, electrostatic potential, etc. intermolecular interactions, and stereospecific structure of a molecule or substrate surface, hindered by geometrical factors such as optically active, crystalline state, or that electronic state molecules Yusuke glass state when consisting only of the same molecule Is subject to change.

To produce the organic superlattice optoelectronic device of the present invention, various thin film forming techniques by a dry process capable of epitaxial growth, for example, MBE (Molecular Beam E)
pitaxy) method, ALE (Atomic Layer Epitaxy) method, ML
E (Molecular Layer Epitaxy) method, MO-ALE (Met
alorganic Atomic Layer Epitaxy), MOCVD (Me
(talorganic Chemical Vapor Deposition) method.

The organic substances include polycarbonate, polysulfone, polyarylate, polyester, polyamide, polyimide, polysiloxane, polyethylene terephthalate, polyvinyl acetate, polyethylene, polypropylene, acrylic resin, polybutadiene, polyvinyl chloride, polyvinylidene chloride, petroleum resin, Melamine resin, epoxy resin, phenol resin, isoprene rubber, ethylene-propylene rubber, norbornene resin, cyanoacrylate resin, styrene resin and their copolymers, cellulose, starch, chitin, agar, silk, cotton, nylon,
Albumin, globulin and other proteins, wood, bone meal and the like, and low molecular organic substances include condensed aromatic compounds such as naphthalene and anthracene, dyes, pigments, urea, tartaric acid, optically active amino acids and the like.

The organic thin filmToInorganic substances, such as glass,
Quartz, diamond, silicon dioxide, mica, marble, calcite
Stone, single crystal silicon, amorphous silicon, GaAs, Cd
S, KDP, KTP, lithium niobate, potassium bromideC
, Rochelle salt, copper sulfate, calcium fluoride, graph
Aite, tin dioxide, barium titanate, red blood salt, ceramic
Vessel, ceramics, benite, cement, metal or
An alloy or the like can coexist or be mixed.

The organic superlattice optoelectronic device of the present invention can be used as it is or after adding a suitable dopant after forming the superlattice structure to form a block, plate, fiber, powder, or thin film. . Further, in the above-mentioned shape, it can be used together with another material having a different structure of the present invention or a different material.

Further, the organic superlattice optoelectronic device of the present invention comprises:
Post-treatments such as thermal annealing, radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic field line irradiation, and ultrasonic irradiation may be performed to improve the characteristics and extend the life.

The organic superlattice optoelectronic device of the present invention includes, for example, an optical waveguide, an optical mixer, an optical phase discriminator, an optical modulator, an optical deflector, an optical selective wave plate, a phase conjugate mirror, an optical switch, and an optical light emitting device. It can be applied to a laser emitting element, a photoelectric conversion element, a light-sound conversion element, a piezoelectric element, an optical logic element, a memory element, a display element, and the like.

[0054]

The organic superlattice optoelectronic device of the present invention comprising a highly crystalline heteroultra-thin film having a thickness of about several nm, which has been difficult with conventional film-forming techniques, is characterized by a high quality organic ultra-thin film. By having a lattice (heteroepitaxial) structure, a new superlattice electronic state can be realized by the quantum confinement and tunnel effect of organic molecules. Also, excitons stabilized in the superlattice structure of such organic molecules,
A novel organic superlattice optoelectronic device is provided by elementary exciton characteristics such as polaron.

[0055]

EXAMPLES The organic superlattice optoelectronic device of the present invention will be described based on examples.

[Example 1] A molecular beam deposition apparatus [MBE for organic substance] which is an example of an apparatus for producing an organic superlattice structure of the present invention
(Molecular Beam Epitaxy) apparatus, hereinafter referred to as MBE apparatus] is shown in FIG.

The MBE apparatus includes an exchange chamber 1 for introducing a substrate into the apparatus, a pretreatment chamber 2 for cleaning the substrate by heating and irradiation with ultraviolet rays, a growth chamber 4 for depositing and forming an organic superlattice structure, It has a preliminary deposition chamber 3 for depositing a gold electrode or the like on the lattice structure, a structural analysis chamber 5 for analyzing the superlattice structure, and an optical evaluation chamber 6 for measuring and evaluating the optical characteristics. Are linked. Each of the chambers is individually connected to an ultra-high vacuum pump (not shown). Note that the arrangement of each chamber is not limited to FIG.
Further, other chambers may be provided as needed.

FIG. 2 shows an example of the structure of the growth chamber 4 for forming the above-mentioned organic superlattice structure.

The growth chamber 4 is constantly evacuated to the main exhaust system by an ultra-high vacuum pump (not shown) via a gate valve 7. The substrate 11 forming the organic superlattice structure is held by a substrate holding unit 9, and the substrate holding unit 9 includes a unit for changing the direction of the substrate surface (not shown) and a substrate heating unit 10. The substrate heating means 10 can arbitrarily control the temperature of the substrate 11 in the range of + 1000 ° C. to −271 ° C. by using both the heater and the coolant.

During the vapor deposition, liquid nitrogen is conducted through the growth chamber 4 to maintain the degree of vacuum in the chamber and capture excess molecular beams. In this embodiment, there are three molecular beam sources, each of which is Kn.
An evaporation sample is held in an udsen cell (hereinafter referred to as a K-cell) 15. The K-cell is moved in and out of the growth chamber 4 by a K-cell moving means 18, and its entrance and exit are separated by a gate valve 7 '. The K-cell 15 held by the K-cell moving means 18 is first degassed by a sub-exhaust system connected via a valve 17 and then transferred into the growth chamber 4.

The K transported by the K-cell moving means 18
The cell 15 is heated by the K-cell heating means 16 to or above the evaporation temperature of the sample, and emits the molecular beam of the sample toward the substrate 11 at a constant evaporation rate. The vapor deposition time of the sample molecular beam is controlled by opening and closing the shutter 13. In addition,
A molecular beam controller 14 is provided on the way to improve the directivity of the emitted sample molecular beam. Further, the growth chamber 4 is provided with means for sequentially monitoring molecular beam injection speed, residual gas concentration, thin film crystallinity, and the like (not shown).

FIG. 3 shows an example of the film thickness distribution of the organic molecular ultra-thin film produced using the MBE apparatus. Figure 3 is a copper phthalocyanine on a silicon substrate, vacuum degree 10 ~ ¹⁰ the To
An SEM (Scanning Electron Micr) obtained by observing a film formed on an rr stage (substrate temperature 200 ° C.) with an acceleration voltage of 5 kV and a horizontal inclination angle of the sample of 60 ° while emphasizing irregularities in the thickness direction of the thin film.
oscope: Hitachi S-800 type field emission scanning electron microscope)
Observed by FIG. 3A shows the film thickness distribution in a plane, and FIG. 3B shows the film thickness distribution on the line AA ′ in FIG.

In the case of a normal vacuum deposition film, about 10 to 20 n
Although the unevenness of m is observed, the molecular beam deposited film of the present example has a very smooth and uniform film thickness, and has an unevenness of only about 3 to 4 molecular layers in an extremely wide range of 3 cm × 4 cm. It can be seen that the film was not uniform. This means
This indicates that the molecular beam is formed with extremely uniform intensity distribution. As described above, according to the MBE method, it cannot be obtained by ordinary vacuum deposition.
It can be seen that a film having unevenness in molecular order with irregularities can be produced.

Embodiment 2 Next, an example in which two different kinds of raw material organic compounds are used to control the molecular orientation thereof and form alternately stacked films of a few molecular layers will be described.

As raw material organic compounds for the organic superlattice,
From the viewpoint of the increase in intermolecular interaction due to the d-orbit of the central metal and the ease of epitaxial growth control due to the similarity of the molecular skeleton, copper phthalocyanine (CuPc) and zinc phthalocyanine (ZnPc), which are a kind of metal phthalocyanine, are used.
Select organic compounds of different types and prepare CuPc / ZnPc / Si and ZnPc / CuPc / S on a single crystal silicon (Si) substrate.
The two types of combinations i were alternately stacked, and the ultrathin film forming conditions of the organic superlattice were examined.

The above-mentioned copper phthalocyanine and zinc phthalocyanine were subjected to heat degassing at a temperature of about 250 ° C. in a glass tube oven (manufactured by Shibata Scientific Instruments) at a reduced aspirator pressure at about 250 ° C. to obtain adsorbed moisture and volatile impurities. (Unreacted raw materials such as phthalonitrile) were removed as much as possible.

The substrate was a silicon single crystal substrate (Shin-Etsu Chemical,
35mm × 35 with a diamond pen
mm, and the document [S. Hattori, et al., JA
ppl.Phys. 67 , 237 (1990)] (UV / HF method)
After cleaning the surface, the sample was subjected to molecular beam evaporation. That is, the silicon substrate was set on a hot plate set at 200 ° C. in air and covered with aluminum foil, and the
Ultraviolet rays were applied to the front and back of the substrate for 10 to 20 minutes using a high-pressure mercury lamp (440 W) from a distance of 1 cm to remove the organic contaminant layer on the surface. Then, sodium persulfate (Na
₂ S ₂ O ₈ , boiled with a saturated solution of pure water in Wako Pure Chemical Industries, Ltd., and carefully washed with pure water to remove adhering organic contaminants. Made,
After removing the natural oxide film on the surface by etching with a semiconductor grade product), immediately wash it with pure water and do not drain it. Attached to.

This was quickly set in the exchange chamber 1 of the MBE apparatus, evacuated with a turbo molecular pump until the pressure became 1 × 10 to ⁸ Torr or less, and the structure analysis chamber 5 and the growth chamber 4 were maintained in an ultra-high vacuum. Introduced within.

Next, conditions for molecular beam deposition of metal phthalocyanine will be described. Growth chamber base pressure 3.8 × 10 ~ ¹¹
Torr, the deposition time pressure (7~11) × ¹⁰ ~ 10 Torr
(Value by the nude ion gauge attached to the device) K- made of fused quartz glass loaded with about 0.2 to 0.3 g of sample
After the cell was previously degassed on the order of 10 to ⁹ Torr, differential evacuation (pressure 7 to 9 × 10
~ ⁹ Torr) and 400 ℃ with tantalum heater
Heated. The substrate temperature was determined by X-rays in the literature [Shintaro Hattori, "Structural Control of Organic Ultrathin Film", New Technology Agency, Creative Science Promotion Project, 1989 Research Report, 2nd Abstract, p. 22, p. 22 (1989)]. The temperature was set to 200 ° C., where it was estimated that the crystallinity of the ultra-thin film was the highest with reference to the results of diffraction (XRD) and RHEED analysis. Under these conditions, an ultrathin film was grown for about 2 hours. During the growth of the ultra-thin film, the molecular beam intensity was monitored using a quartz crystal film thickness meter attached to the apparatus, and the following analytical evaluation was performed as necessary.

Before and after molecular beam deposition, AES (Auger Electron Spectroscopy) was used to confirm and evaluate the cleanliness and thin film formation of the substrate.
scopy) and XPS (X-ray Photoelectronspectrosco)
py) Measurements were taken. These measurements were performed in the structural analysis chamber 5 connected to the MBE growth chamber and maintained in an ultra-high vacuum of the order of 10 to ¹⁰ Torr.

AES measurement was performed using ESCA / AE manufactured by PHI.
The S255 system (equipped with a coaxial electron gun and a cylindrical double-pass energy analyzer) was set in the AES measurement mode, and the measurement was performed at a primary electron acceleration voltage of 3 kV.

The XPS measurement was performed using the same apparatus in the XPS measurement mode and using MgKα radiation (1253.6 eV) as the X-ray source. The measurement was performed at room temperature, and temperature control such as heating and cooling for protecting the sample was not particularly performed.

The spectrum thus obtained is described in the literature [C.
D. Wagner et al., "Handbook of X-ray Photoelectron
Spectroscopy ", Perkin-Elmer Co. (1979), and L.
E. Davis et al., "Handbook of Auger Electron Spectr
oscopy ", Physicalelectronics industries, Inc. (197
6 years)] and identified by referring to the standard spectrum described above.

The thickness of the prepared thin film was determined by ellipsometry in the air. Since the phthalocyanine compound vapor-deposited film shows a non-negligible absorption in the ordinary film thickness calculation at the He-Ne laser wavelength (632.8 nm) of the light source, the incident angles to the sample are set to 70 degrees and 58 degrees, respectively. The phase difference Δ and the arc tangent 反射 of the reflection coefficient ratio were measured at the incident angle, and the film thickness was calculated from these.

FIG. 4 shows ZnPc / CuPc / Si and CuP
5 is a graph showing a change over time in XPS intensity in the process of forming an alternately laminated film (two layers) of c / ZnPc / Si.

In the case of the ZnPc / CuPc / Si film shown in FIG. 4A, during the growth process of the first layer of CuPc, the signal from the Si atoms on the substrate is sharply reduced in the first two hours, and the C and N of the CuPc layer are reduced. , Signals from Cu atoms increase. The ratio does not change even after 4 hours. Even if the second layer ZnPc is deposited thereon for 4 hours, the signals of Si, C and N do not change much. The signal of the central metal is C
u decreases slightly and Zn increases. From this, the first layer of CuPc is deposited on a clean portion of the Si substrate surface in the first 2 layers.
It was found that the ZnPc of the second layer grew uniformly on the first layer of CuPc, with almost no growth on the other portions.

On the other hand, CuPc / Z shown in FIG.
In the case of the nPc / Si film, the signal of Si gradually decreases and the signal of C, N, and Zn continues to increase during the growth process of the first layer of ZnPc. On top of this, the second layer C
When uPc is grown, the signal of Si decreases significantly, and the signals of C and N further increase. The central metal signal showed a significant increase in Cu whereas a significant decrease in Zn. For this reason, the first layer of ZnPc was only slightly sparsely grown on the substrate surface even after the deposition for 4 hours, and the second layer of CuPc was deposited on the undeposited substrate surface other than on the ZnPc. Was also growing.

It is considered that such a difference in the growth state of the first layer reflects the average stay time of the organic molecules under the experimental substrate temperature condition, that is, a difference in the adhesion coefficient. When the thickness of these ultrathin films was determined by ellipsometry, CuP
c / Si (2 hours) about 46 °, ZnPc / Si (2 hours) about 15 °, ZnPc / CuPc / Si (4 hours /
4 hours) and about 70 ° for CuPc / ZnPc / Si (4 hours / 4 hours).

Next, the molecular orientation of the ultra-thin film having several molecular layers was determined from the dependence of the XPS signal intensity on the escape angle (θ).

FIG. 5 shows an XPS chart of the CuPc / ZnPc / Si film with the escape angles of 90 ° and 30 ° with respect to the substrate surface.

As the escape angle becomes smaller, the signal of the atom closer to the surface of the thin film is enhanced, and the signal of the atom deeper than the surface is attenuated. It can be seen that the signals of Si on the substrate and Zn of the first layer are considerably attenuated.

[0082]

[Table 1]

Table 1 shows that CuPc / Si and ZnPc / S
i, CuPc / ZnPc / Si, ZnPc / CuPc /
The escape angle dependence of the XPS signal of Si is shown as a relative value to the signal of the C atom. Looking at the molecular orientation of the monolayer,
The signals of C, N, and Cu constituting CuPc have almost no escape angle dependence, and have the same depth from the surface, that is, the molecular plane is oriented almost horizontally with respect to the substrate.

On the other hand, in ZnPc, as the escape angle is smaller, the signals of N and Zn are weaker than that of C atom,
Since the N and Zn atoms are located below the C atoms, it is understood that the molecular plane stands on the substrate.

When the second layer is laminated, CuPc / ZnP
In the c / Si film, the signal of Zn was significantly reduced.
u shows almost the same dependency as a single-layer CuPc film, and many CuPc have a different orientation from the first layer. On the other hand, in the ZnPc / CuPc / Si film, the escape angle dependence was observed in the signal of Cu to some extent, but the signal of Zn did not, and the orientation was almost the same as the horizontal orientation of CuPc in the first layer. It was found that ZnPc of the second layer was obtained.

FIG. 6 shows a model of the molecular orientation of this alternately laminated film predicted from these findings.

When the first layer is made of CuPc as shown in FIG. 6B, the molecular plane is oriented horizontally with respect to the substrate surface, and ZnPc on this is oriented in the same horizontal manner as CuPc. On the other hand, when the first layer is made of ZnPc as shown in FIG. 6A, the molecular plane is oriented almost perpendicular to the substrate plane. In particular, insufficient coverage of the current growth time, CuPc grown thereon, on the Si substrate which is not covered with ZnPc
Is also growing.

From the above results, a heteroepitaxial ultrathin film of about several tens of phthalocyanines having different center metals can be produced.

[Embodiment 3] Next, an example in which three or more organic ultra-thin films are multilayered to form a superlattice structure will be described.

As described in Example 2, by providing copper phthalocyanine for the first layer on the cleaned silicon single crystal plate, the molecular orientation as expected and the zinc phthalocyanine of the second layer were oriented. I found that I could grow. Therefore, a novel organic superlattice structure in which a plurality of layers are alternately stacked was produced by repeating the same film forming conditions, that is, repeating the combination of CuPc for the first layer and ZnPc for the second layer.

FIG. 7 shows a film obtained by alternately stacking copper phthalocyanine and zinc phthalocyanine three times, for a total of six layers [hereinafter referred to as (Zn).
Pc / CuPc) x / Si (x = 3)]
It is an S chart. Total thickness by ellipsometry is about 2
The thickness per layer is 30 to 40 °.
It is. The metal phthalocyanine in the third and subsequent layers, since the signals of copper and zinc are not lost and the signal derived from the oxide film of the substrate does not disappear, without re-evaporating the metal phthalocyanine once deposited, It can be seen that they are stacked on top.

In the same manner as above, 50 times with the same combination,
Organic superlattice thin film [hereinafter referred to as (ZnPc / CuPc) x / S, respectively] in which a total of 100 layers are laminated on a silicon substrate [Si (100)] and a potassium chloride substrate [KCl (100)].
i (x = 50) and (ZnPc / CuPc) x / KCl
(X = 50)]. The total film thickness by the ellipsometry method was about 4000 to 5000 ° in all cases.

As shown in this embodiment, it is possible to form a superlattice structure composed of organic molecules by the above method.

Example 4 Next, a third-order nonlinear optical characteristic, which is one of the indexes of performance when the organic superlattice structure is used as an optical third harmonic generation device, which is one of the optoelectronic devices, was evaluated. .

The above-mentioned optical third harmonic generation element provides a coherent micro light source used for optical communications, optical computers, and the like. When a laser beam having a specific wavelength is incident on the element, it is transferred to the element medium. Since nonlinear polarization occurs and light having a wavelength of 1/3 of the wavelength of the incident light is generated, it can be used as an optical wavelength conversion element.

FIG. 8 is a configuration diagram showing an optical system for evaluating the same. Q-switch YAG laser system (Quanta-
Ray 106, generated by DCR-3) 22
Laser light of two wavelengths of 4 nm and 532 nm is a dye laser system (PDL-2, manufactured by Quanta-Ray) 23
And a 532 nm laser beam is used as an excitation light source for a dye laser (LDS69, manufactured by Quanta-Ray Co., Ltd.).
8) is used to generate 681 nm light. This 6
The light of 81 nm and the light of 1064 nm are a difference frequency generator (Q
Infrared Wavelength Extens manufactured by anta-Ray
ion system) 24 and converted into 1900 nm infrared light.

This 1900 nm infrared light is reflected by two mirrors.
The sample 28 is irradiated to the sample 28 through 25, 25 ', a filter 26 for intensity adjustment, and a lens 27 for light collection.

Sample 28 was prepared in Example 3.
(ZnPc / CuPc) x / Si (x = 50) and (ZnPc
/ CuPc) x / KCl (x = 50), and the comparative samples are CuPc / Si
And ZnPc / Si. Further, a fused quartz substrate was used as a standard sample.

The angle of incidence of infrared light of 1900 nm on the sample 28 is controlled by the rotating stage 29. Sample 28
The light of 1900 nm out of the light transmitted through the
Then, only the third harmonic (633 nm) generated in the sample is separated by the monochromator 30 and detected by the photomultiplier tube 31.

Table 2 shows the measured intensity of the third harmonic. As can be seen from Table 2, the generation of the third harmonic was observed 4 to 5 times higher than that of a normal vacuum deposited film by forming a super lattice structure.

[0101]

[Table 2]

[Embodiment 5] Next, characteristics when an organic ultrathin film is used as an optical-optical switching element which is one of optoelectronic elements will be described.

The light-optical switching element used here is used for optical communication, optical computers, and the like. When the probe light for transmitting information passes through the switching medium, the transmittance is controlled by the gate light to control the transmittance. , High-speed optical calculation and the like are realized. The magnitude of the effect is evaluated based on the physical properties of the switching medium used, such as the third-order nonlinear optical characteristics and the change over time in the absorption spectrum.

In this embodiment, an example in which the produced organic ultrathin film is used as a switching medium and the probe light transmittance is controlled by gate light will be described.

FIG. 9 is a block diagram of an optical system for evaluating the characteristics of the light-light switching element. A semiconductor laser (900 nm peak wavelength) is used as the probe light source 37, and the gate light source 3 is used.
For No. 8, a nanosecond pulse dye laser (wavelength 700 nm) was used.

The probe light is first split by the polarizer 39 into only a specific polarization component, passes through the half mirror 40 without loss, is condensed by the lens 41, and is irradiated on the sample 28. The gate light is reflected by the half mirror 40, is coaxially matched with the probe light, is similarly condensed by the lens 41, and irradiates the sample 28. Sample 28 includes the organic superlattice (ZnPc / CuPc) x / KCl (x = 5) prepared in Example 3.
0) was used.

When there is no gate light from the gate light source 38, the probe light from the probe light source 37 is transmitted without changing the polarization direction by the polarizer 39. A polarization component orthogonal to the incident probe light appears.

The probe light and the gate light that have passed through the sample 28 are returned to parallel light by the lens 41 ′, and the half mirror 40 ′
, The gate light is reflected and reaches the damper 44, and the probe light is transmitted through the half mirror 40 ′ as it is to the analyzer 43.
To reach. In the analyzer 43, only a component orthogonal to the incident probe light generated in the sample portion is transmitted and detected by the light meter 45.

Table 3 shows the relationship between the gate light intensity and the probe light transmittance of the analyzer. As described above, the transmittance of the probe light in the sample portion changes according to the gate light, and it can be seen that the sample portion has switching characteristics.

[0110]

[Table 3]

[0111]

According to the present invention, it is possible to obtain a novel organic superlattice optoelectronic device using the characteristics of elementary excitons such as excitons and polarons stabilized in the superlattice structure of organic molecules.
By using this, an optical third harmonic generation element and an optical-optical switching element can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a molecular beam evaporation apparatus for producing an organic superlattice structure.

FIG. 2 is a configuration diagram of a growth chamber of a molecular beam deposition apparatus.

FIG. 3 is a thickness distribution diagram of a molecular beam deposited film of copper phthalocyanine.

FIG. 4 is a graph showing the change over time of the XPS signal of an alternate bilayer film of copper phthalocyanine and zinc phthalocyanine.

FIG. 5 shows X at an escape angle of 90 ° and 30 ° with respect to the substrate surface of an alternate bilayer film of copper phthalocyanine and zinc phthalocyanine.
It is a PS chart figure.

FIG. 6 is a model diagram of the molecular orientation of an alternating bilayer film of copper phthalocyanine and zinc phthalocyanine.

FIG. 7 is an XPS chart of a copper phthalocyanine and zinc phthalocyanine alternate six-layer film.

FIG. 8 is a configuration diagram of an optical system for evaluating an organic superlattice optical third harmonic generation element.

FIG. 9 is a configuration diagram of an optical system for evaluating light-light switching characteristics.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exchange room, 2 ... Pre-processing room, 3 ... Preliminary vapor deposition room, 4 ... Growth room, 5 ... Structural analysis room, 6 ... Optical evaluation room, 7, 7 '... Gate valve, 9 ... Substrate holding means, 10 ... Substrate heating means, 1
DESCRIPTION OF SYMBOLS 1 ... Substrate, 13 ... Shutter, 14 ... Molecular beam control means, 1
5 ... K-cell, 16 ... K-cell heating means, 17 ... Valve, 18 ... K-cell moving means, 19,19 '... Copper phthalocyanine molecule, 20,20' ... Zinc phthalocyanine molecule, 21,21 '... Silicon Substrate, 22 ... Q switch Y
AG laser system, 23: dye laser system, 24: difference frequency generator, 25, 25 ': filter, 26, 26': mirror, 2
7 ... Lens, 28 ... Sample, 29 ... Rotating stage, 30 ...
Monochromator, 31 Photomultiplier tube, 32 High voltage power supply, 33 Delay circuit device, 34 Boxcar integrator, 3
5 GB-IB, 36 personal computer, 37
... probe light source, 38 ... gate light source, 39 ... polarizer, 4
0, 40 ': half mirror, 41, 41': lens, 43
... analyzer, 44 ... damper, 45 ... light meter.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H01S 3/109 H01L 29/28 // H01L 31/10 31/10 A (72) Inventor Shintaro Hattori 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Atsushi Kakuda 4026 Kuji-machi, Hitachi City, Ibaraki Prefecture, Hitachi Research Laboratory, Hitachi, Ltd. (56) References , A) PHYS. REV. LETT. 66-20! (1991) (USA) 2649−2652

Claims (7)

(57) [Claims] 1. An organic superlattice optoelectronic device comprising a medium that can be modulated by light incident / injection, charge injection or electric and magnetic fields, wherein the device comprises two or more organic ultrathin layers on a single crystal substrate. Hetero-epita with periodic epitaxial lamination of
An organic superlattice optoelectronic device, having an axial structure. Wherein said organic ultra-thin layer comprises two or more organic film, and, even more of the thickness of the thin film 1~100000Å
, And the organic superlattice optoelectronic device according to claim 1, repetition number lamination of different thin film layer is formed in at least three layers. Wherein the organic ultra-thin layer comprises two or more organic film, and a layer of the thickness of the thin film is 1 to 100 molecular layers, repetition number of layers of different thin film layers are at least 3
Organic superlattice optoelectronic device according to claim 1, which consists in the layer. 4. Before Kieu machine ultrathin layer Do subjected to external influences
4. The organic superlattice optoelectronic device according to claim 1 , wherein the electronic state at the time is modulated by a single crystal substrate forming the ultrathin film or another ultrathin film layer on the substrate . 5. Before Kieu machine organic superlattice optoelectronic device according to any one of claims 1 to 4 provided some or electrodes for moving the electric field applied or charges in the vicinity of the ultra-thin layer. 6. Before Kieu machine organic superlattice optoelectronic device according to any one of claims 1 to 6 ultrathin film layer comprises inorganic molecules. 7. A single-crystal silicon substrate having surface impurities removed in a container maintained at an ultra-high vacuum of 10 to ⁶ Torr or less.
A plate or a single crystal substrate of potassium chloride is held, the substrate is heated to 200 ° C. or higher, and each cell containing at least two kinds of organic ultra-thin film materials is a cell provided with a heating means, a molecular beam control means, and a shutter. By loading the moving means, heating the organic ultra-thin film material to an evaporating temperature or higher, and opening and closing the shutter for a predetermined time to alternately irradiate the molecular surface of the organic ultra-thin material onto the substrate surface, thereby dissimilar materials are used. A method for manufacturing an organic superlattice optoelectronic device, comprising forming a heteroepitaxial structure by laminating organic ultrathin films.