JP3918074B2 - Method for synthesizing diamond-like carbon film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for synthesizing a diamond-like carbon film, and more particularly to a method for synthesizing a diamond-like carbon film in an organic liquid.
[0002]
[Prior art]
Conventionally, diamond-like carbon films (DLC: Diamond Like Carbon) have shape flexibility due to their amorphous structure, hardness close to diamond, excellent thermal conductivity, high insulation, etc. Use as a protective film is expected.
For example, in electronic devices such as computers, the magnetic storage medium disk of the hard disk is covered with a diamond-like carbon film, and even if the magnetic storage head should come into contact, the protective film is to prevent mechanical damage to the magnetic storage medium disk As a diamond-like carbon film is used.
Further, it is expected to be used not only as a hard disk but also as an excellent protective film for preventing mechanical damage and wear of all mechanical parts such as gears, rotating shafts and bearings.
[0003]
However, a conventional method for synthesizing a diamond-like carbon film is based on a chemical vapor deposition method (see Phys. Rev. B46, 7169 (1992)). Further, there is a problem that an exhaust device and a highly accurate gas flow rate / temperature control device are required and the cost is high.
In addition, the coating of diamond-like carbon film by chemical vapor deposition grows by depositing and growing carbon produced by thermochemical reaction in the vicinity of the member to be coated. There is a problem that the growth rate differs depending on the material, and it is difficult to coat with a uniform thickness.
For this reason, conventionally, the coating of the diamond-like carbon film is limited to a flat plate-like member such as a hard disk, and it has been difficult to use it for a member having an arbitrary shape such as a gear, a rotating shaft, or a bearing.
[0004]
Further, as described above, the diamond-like carbon film has the same hardness and thermal conductivity insulating property as diamond, but is also a semiconductor like diamond. Therefore, if p-type and n-type diamond-like carbon films can be synthesized at low cost, an electronic device having high breakdown voltage, high temperature resistance, and high radiation resistance can be put into practical use.
However, at present, there is no known method for synthesizing p-type and n-type diamond-like carbon films at low cost.
[0005]
[Problems to be solved by the invention]
In view of the above problems, the present invention provides a method for synthesizing a diamond-like carbon film that can be synthesized at a low cost and can be applied to a member having a surface of an arbitrary shape with a uniform thickness, and p-type and n-type conductivity. An object of the present invention is to provide a method for synthesizing a diamond-like carbon film having:
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the method for synthesizing a diamond-like carbon film of the present invention is to heat a member in an organic liquid maintained at a temperature equal to or lower than the boiling point to bring the surface of the member to a high temperature of 600 ° C. or higher. A diamond-like carbon film is synthesized on the member by causing a rapid temperature gradient from the surface of the member toward the organic liquid.
In the above structure, the organic liquid is benzene (C ₆ H ₆ ), cyclohexane (C ₆ H ₁₂ ), n-hexane (C ₆ H ₁₄ ), methanol (CH ₃ OH), ethanol (C ₂ H ₅ OH), or Any one of acetone (CH ₃ COCH ₃ ) is preferable.
Further, organic liquids containing an element imparting conductivity include triethylborane ((C ₂ H ₅ ) ₃ B), n-butylamine (C ₄ H ₉ NH ₂ ), triphenylphosphine ((C ₆ H ₅ ) ₃ P) or methanethiol (CH ₃ SH) is preferable.
[0007]
According to the above method, the apparatus cost is extremely low. In addition, since the synthesis mechanism depends on the temperature gradient of the surface of the member and the organic liquid, it can be synthesized with a uniform film thickness regardless of the unevenness of the surface of the member. The organic liquid used as the raw material can be various organic liquids, and the raw material cost is extremely low. Furthermore, by adding an organic liquid containing a specific element as a constituent element, p-type and n-type diamond-like carbon films can be synthesized, and conductivity can be imparted or a pn junction can be formed. For example, when an organic liquid containing B such as triethylborane ((C ₂ H ₅ ) ₃ B) is added, it becomes p-type, and an organic liquid containing N such as n-butylamine (C ₄ H ₉ NH ₂ ), triphenyl, When an organic liquid containing P such as phosphine ((C ₆ H ₅ ) ₃ P) or an organic liquid containing S such as methanethiol (CH ₃ SH) is added, an n-type is obtained.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a view showing an apparatus for synthesizing a diamond-like carbon film using an organic liquid according to the present invention.
The method for synthesizing the diamond-like carbon film of the present invention will be described with reference to FIG.
This synthesizer holds a water cooling means 2 for cooling the liquid tank 1 outside the liquid tank 1 and a member 3 for adhering the diamond-like carbon film, and an electrode 4 for passing a current through the member 3. A member holder 5 having a condenser, a condensing means 7 comprising a water-cooled pipe 6 that cools and condenses the organic liquid vapor evaporated from the liquid tank 1 and returns it to the liquid tank 1, and introduces the member holder 5, the condensing means 7 and N ₂ gas. It has a lid 9 for holding the valve 8, and the organic liquid 10 is hermetically held by the liquid tank 1 and the lid 9.
[0009]
According to this apparatus, the temperature of the organic liquid 10 can be kept below the boiling point, the temperature of the member 3 can be kept high, and the diamond-like carbon film can be synthesized. Moreover, since the vapor phase of the organic liquid 10 is condensed, the raw organic liquid 10 is not wasted, and there is no danger of explosion and flame due to mixing of the organic vapor phase and air. Further, since the inert gas introduction means 8 is provided, there is no danger of explosion and flame due to mixing of the organic gas phase and air in the liquid tank 1.
[0010]
Next, a method for synthesizing a diamond-like carbon film using the organic liquid of the present invention when using the synthesis apparatus shown in FIG. 1 will be described.
First, the conductive member 3 is cleaned and placed in the member holder 5 of the synthesis apparatus shown in FIG. Next, the organic liquid 10 is filled and N ₂ gas is introduced through the valve 8 to replace the remaining air in the synthesizer with N ₂ gas. Then, the member 3 is heated by passing an electric current through the electrode 4. Bubbles made of the gas of the organic liquid 10 are generated from the surface of the member 3, and the surface of the member 3 is covered with the bubbles. At this time, it is necessary to keep the temperature of the organic liquid 10 below the boiling point of the organic liquid 10, and the water cooling means 2 is used for cooling. The vapor-phase organic liquid 10 is returned to the liquid 10 by the condensing means 7 and returned to the liquid tank 1. The diamond-like carbon film is synthesized on the member 3 by maintaining the synthesis apparatus in the above state for a certain period of time according to the desired thickness of the diamond-like carbon film.
[0011]
Examples of the organic liquid include liquefied hydrocarbons such as benzene (C ₆ H ₆ ), cyclohexane (C ₆ H ₁₂ ), n-hexane (C ₆ H ₁₄ ), methanol (CH ₃ OH), and ethanol (C ₂ H ₅ OH). ) Or liquid oxygen-containing organic compounds such as acetone (CH ₃ COCH ₃ ) are preferable.
When synthesizing a p-type or n-type diamond-like carbon film, an element that becomes a p-type impurity or an n-type impurity in the diamond crystal, for example, an element such as boron (B), sulfur (S), or nitrogen (N) is used. It is synthesized by adding an organic liquid as a constituent element. The temperature of the member is preferably 600 to 1300 ° C., and the higher the temperature, the faster the synthesis rate of the diamond-like carbon film.
[0012]
The growth mechanism of the diamond-like carbon film of the present invention is considered as follows. The surface of the member 3 is a high temperature of several hundred degrees Celsius or higher, while the temperature of the organic liquid 10 adjacent to the surface of the member 3 is as low as the boiling point. Further, the surface of the member 3 is covered with the gas of the organic liquid 10, and a steep temperature gradient exists in the gas of the organic liquid 10 from the surface of the member 3 toward the liquid 10. This rapid temperature gradient is considered to cause a unique thermal decomposition reaction in the gas of the organic liquid 10 and synthesize an amorphous diamond-like carbon film on the member 3.
[0013]
According to the above method, the apparatus cost is extremely low as shown in FIG. In addition, since the synthesis mechanism depends on the temperature gradient of the surface of the member and the organic liquid, it can be synthesized with a uniform film thickness regardless of the unevenness of the surface of the member. The organic liquid used as the raw material can be various organic liquids, and the raw material cost is extremely low. Further, by adding an organic liquid having a specific element as a constituent element, p-type and n-type diamond-like carbon films can be synthesized, and can be provided with conductivity or a pn junction.
[0014]
Next, examples of the present invention will be described.
The following four types of organic liquids were used.
(A) methanol (CH ₃ OH)),
(B) ethanol (C ₂ H ₅ OH),
(C) acetone (CH ₃ COCH ₃ ),
(D) Benzene (C ₆ H ₆ ).
As a member for covering the diamond-like carbon film, a Si substrate having a mirror-polished surface was used. The diamond-like carbon film synthesizing apparatus was the same as that shown in FIG.
[0015]
FIG. 2 is a diagram comparing the relationship between the growth rate of the diamond-like carbon film and the member temperature for each type of organic liquid. In the figure, the horizontal axis shows the member temperature by current heating, and the vertical axis shows the growth rate of the diamond-like carbon film.
As can be seen from the figure, the higher the member temperature and the higher the growth rate of the organic liquid having a larger number of carbon atoms.
[0016]
FIG. 3 is an SEM photograph showing the shape of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as an organic liquid as a raw material, and FIG. 3 (a) shows the surface shape of the diamond-like carbon film, FIG. FIG. 3B is a diagram showing a cross-sectional shape, and FIG. 3C shows the surface and the cross-sectional shape. In the figure, 31 indicates a diamond-like carbon film, and 32 indicates a Si member. Member temperature is 880-900 degreeC.
As can be seen, the entire surface of the diamond-like carbon film is smooth and the film thickness is uniform.
[0017]
FIG. 4 is a diagram showing a Raman spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a raw material organic liquid. The horizontal axis indicates the Raman shift amount, and the vertical axis indicates the Raman intensity. The excitation light wavelength is 514.47 nm.
As can be seen from the figure, a so-called D band having a peak near 1340 to 1360 cm ^-1 and a so-called G band centering around 1560 to 1600 cm ^-1 are observed, indicating that this thin film is a diamond-like carbon film. ing.
[0018]
FIG. 5 is a diagram showing an X-ray photoelectron spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a raw material organic liquid. The horizontal axis indicates the photoelectron binding energy, and the vertical axis indicates the photoelectron intensity. AL-Kα ray was used as the excitation X-ray.
As can be seen from the figure, a peak is observed around 275 eV, indicating that the film is composed of only carbon. Note that an oxygen peak is observed in the vicinity of 534 eV, but the intensity is extremely small. This is probably because the film surface is slightly oxidized or oxygen is adsorbed on the surface.
[0019]
FIG. 6 is a diagram showing an electron beam energy loss spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a raw material organic liquid. In the figure, the horizontal axis represents the kinetic energy of the electron beam, and the vertical axis represents the electron beam intensity. The kinetic energy of the excitation electron beam is 495 eV.
In the figure, a minute peak of 490 eV (loss of 5 eV) is a peak based on a carbon-carbon π bond, and it can be seen that the graphite component is extremely minute. The peak of 480 to 475 eV (loss of 15 to 20 eV) is a plasmon loss typical of a diamond-like carbon film. This also shows that this film is a diamond-like carbon film.
[0020]
As is apparent from FIGS. 2 to 6, according to the method of the present invention, it is understood that an amorphous diamond film, that is, a diamond-like carbon film (Diamond Like Carbon) can be synthesized.
[0021]
In the above embodiment, an example in which a diamond-like carbon film is grown on a Si member has been described. However, it is possible to grow not only Si but also a conductive material, for example, tungsten (W), molybdenum (Mo ) And other high melting point metals. Further, an n-type diamond-like carbon film can be grown by adding an organic liquid containing nitrogen (N), phosphorus (P), or sulfur (S) to the raw organic liquid. For example, n-butylamine (C ₄ H ₉ NH ₂ ), triphenylphosphine ((C ₆ H ₅ ) ₃ P), or methanethiol (CH ₃ SH) is used to form an n-type diamond-like carbon film. be able to.
[0022]
FIG. 7 is a diagram showing physical property values of the diamond-like carbon film synthesized by the method of the present invention. As is apparent from the figure, it has a density, altitude and resistivity close to those of diamond.
[0023]
In the above description, an example in which a member is heated by current heating has been described, but it is obvious that the member may be heated not only by current heating but also by using a heating device such as resistance heating, infrared heating, or laser heating. It is. In this case, it is possible to synthesize on a member having no conductivity.
[0024]
【The invention's effect】
As understood from the above description, according to the present invention, a diamond-like carbon film can be synthesized at a low cost, and a member having a surface of an arbitrary shape can be coated with a uniform thickness. In addition, p-type and n-type diamond-like carbon films can be synthesized.
Therefore, it is extremely useful if the present invention is used as a protective film having high mechanical strength or as a semiconductor material.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an apparatus for synthesizing a diamond-like carbon film with an organic liquid of the present invention.
FIG. 2 is a diagram comparing the relationship between the growth rate of a diamond-like carbon film and the member temperature for each type of organic liquid.
FIG. 3 is an SEM photograph showing the shape of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as an organic liquid, and (a) shows the surface shape of the diamond-like carbon film, and (b) shows a cross section. It is a figure which shows a shape, (c) shows the surface and a cross-sectional shape.
FIG. 4 is a diagram showing a Raman spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a starting organic liquid.
FIG. 5 is a view showing an X-ray photoelectron spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a raw organic liquid.
FIG. 6 is a diagram showing an electron energy loss spectrum of a diamond-like carbon film grown using benzene (C ₆ H ₆ ) as a raw organic liquid.
FIG. 7 is a diagram showing physical property values of a diamond-like carbon film synthesized by the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid tank 2 Water cooling means 3 Member 4 Electrode 5 Member holder 6 Water cooling pipe 7 Condensing means 8 Valve 9 Lid 10 Organic liquid 31 Diamond-like carbon film 32 Si substrate

Claims (4)

By heating the member in an organic liquid maintained at a temperature equal to or lower than the boiling point, the surface of the member is heated to a high temperature of 600 ° C. or higher, and a rapid temperature gradient exists from the surface of the member toward the organic liquid. A method for synthesizing a diamond-like carbon film, comprising synthesizing a diamond-like carbon film on the member. The organic liquid is benzene (C ₆ H ₆ ), cyclohexane (C ₆ H ₁₂ ), n-hexane (C ₆ H ₁₄ ), methanol (CH ₃ OH), ethanol (C ₂ H ₅ OH), or acetone ( The method for synthesizing a diamond-like carbon film according to claim 1 , wherein the method is any one of CH ₃ COCH ₃ ). The method for synthesizing a diamond-like carbon film according to claim 1 or 2 , wherein an organic liquid containing an element imparting conductivity is added to the organic liquid. The organic liquid containing the element imparting conductivity is triethylborane ((C ₂ H ₅ ) ₃ B), n-butylamine (C ₄ H ₉ NH ₂ ), triphenylphosphine ((C ₆ H ₅ ) ₃ P 4) The method for synthesizing a diamond-like carbon film according to claim 3 , wherein the method is methanethiol (CH ₃ SH).

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