JP7061765B2 - Thin film measuring method and measuring device - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law Satoshi Koizumi, Takashi Oka, Hiroko Ichiwa "Diagonal incident neutron scattering method for measuring microstructure and mass transfer in the film thickness direction" 24th Fuel Cell Symposium, May 2017 Announced on the 26th

The present invention relates to the measurement of a thin film, and particularly to the measurement of a thin film using a small-angle neutron scattering method.

Radiation such as X-rays, γ-rays, and neutrons is used for non-destructive inspection of substances. X-rays are scattered by the electrons of the atom, while neutrons are scattered by the atomic nucleus. The small-angle X-ray scattering method has higher sensitivity for atoms with a larger atomic number, but the scattering ability of each atom to neutrons is on the order of magnitude. On the other hand, structural analysis using neutrons is effective for observing light-mass elements such as hydrogen atoms. In addition, neutrons can be evaluated by distinguishing isotopes such as hydrogen and deuterium.

A method for diagnosing a disease caused by a change in protein morphology using a neutron scattering method has been proposed (see, for example, Patent Document 1). In this method, the test protein dissolved or dispersed in heavy water is irradiated with cold neutrons, and the morphology of the test protein is measured from the scattering of the cold neutrons.

Evaluation of the surface properties of biological thin films such as skin is useful in various fields. For example, by measuring the water content of the skin, the degree of moisture of the skin can be evaluated. The outermost layer of the skin, the stratum corneum, has barrier and moisturizing functions necessary for maintaining vital activity, and accurate measurement of the stratum corneum is important not only in the fields of beauty and cosmetics, but also in the fields of medicine and pharmaceuticals. Is a challenge.

Non-living organic or inorganic thin films are used in various fields such as regenerative medicine, fuel cells, and optical displays. The surface structure of these thin films affects the effectiveness of the treatment applied and the performance of the device. Similar to the biological thin film, the non-living thin film is also required to accurately measure and evaluate the surface state.

International Publication 2006/064819

It is useful in various fields if the state such as the composition of the thin film surface and the substance concentration can be quantified and accurately measured. In particular, a method capable of non-destructively and accurately measuring and evaluating the surface state of a thin film containing a light element such as hydrogen is desired.

An object of the present invention is to provide a method capable of accurately measuring and quantifying the state of the surface of a thin film.

In order to solve the above problems, the state of the surface of the thin film is measured by using small-angle scattering of neutron rays. Specifically, the thin film measurement method is
A thin film sample is placed between the first substrate of silicon and the second substrate with one or more through openings.
With the second substrate, the first surface of the thin film sample is pressed against the first substrate.
A neutron beam is supplied to the thin film sample through the first substrate while supplying a gas or liquid containing at least one substance to the second surface of the thin film sample opposite to the first surface through the through opening. Irradiate and
The reflected beam from the thin film sample is detected, and the state of the surface of the first surface of the thin film sample is measured.

By the above method, the state of the surface of the thin film can be accurately measured and quantified.

It is a figure explaining the oblique incident neutron small angle scattering measurement performed in 1st Embodiment. It is a side sectional view and the front view of the oblique incident neutron small angle scattering measuring apparatus. It is a schematic diagram of the thin film measurement kit used in the 1st Embodiment. It is a schematic diagram of the thin film measurement of Example 1. It is a figure which shows the result of the oblique incident neutron small angle scattering measurement of the stratum corneum. It is a figure which shows the time change of the reflection intensity of the stratum corneum. It is a figure which shows the time change of temperature and humidity at the time of humidifying from the surface of the stratum corneum. It is a figure which shows the time change of temperature and humidity at the time of humidifying from the back surface of the stratum corneum.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram illustrating a Grazing Incidence Small Angle Neutron Scattering (GSANS) measurement performed in the first embodiment. In the small-angle neutron scattering measurement, the sample 60 is set in the measuring device 10, the surface of the sample 60 is irradiated with a neutron beam, and the reflected light from the sample 60 is detected to measure the state (characteristic) of the surface of the sample 60. And evaluate. In addition to the reflected light from the sample 60, transmitted light may be detected.

In the first embodiment, the sample 60 is set in the measuring device 10 while being held by the thin film measuring kit 50. Although details will be described later, the sample 60 is held flat between the two substrates of the thin film measurement kit 50. One or more through openings are formed on one of the substrates, and the neutron beam scattered on the surface of the sample 60 is detected while supplying a liquid or gas to the sample 60 from the through openings. The neutron beam is obliquely incident on the surface of the sample 60 at a shallow angle.

The neutron beam is output from a neutron source (not shown). As the neutron source, for example, a pulsed neutron source using spallation by an accelerator is used. The neutron beam NBin incident on the sample 60 is shaped by the slit 31 of the optical system 30, and is incident on the sample 60 at an incident angle of 0.1 ° to 1.0 ° at which specular reflection occurs, for example. The position and width of the slit 31 of the optical system 30 can be adjusted. The incident neutron beam NBin is scattered on the surface of the sample 60, and the scattered neutron beam NBout is detected by the detector.

Here, the scattering intensity is measured using the flight time method. In the flight time method, a neutron beam having a wide wavelength range is incident on the sample 60 at a fixed angle of incidence, and the scattering intensity is measured. The incident neutrons enter the sample 60 in white without being monochromatic and are scattered. Scattering intensity is measured as a function of wavenumber q. The wave number q is expressed by Eq. (1), is proportional to the incident angle θ, and is inversely proportional to the wavelength λ of the neutron.

q = 4π × sinθ / λ (1)
In the flight time method, the wavelength can be selected by the time detected by the detector, that is, the time when the neutron reaches the detector. By arranging a plurality of detectors over a wide scattering angle, it is possible to measure the scattering intensity in a wide range of wavenumber q.

During the GSANS measurement, the sample 60 held in the thin film measurement kit 50 is supplied with a gas or liquid containing deuterium or light hydrogen. To achieve this, the measuring device 10 has a supply port 15 and a discharge port 16. When the sample 60 or the thin film measurement kit 50 is set in the measuring device 10, an atmospheric environment chamber is formed inside the measuring device 10, and a desired substance (heavy hydrogen, light hydrogen, oxygen, etc.) is contained in the atmospheric environment chamber. It can supply liquid or gas.

2A and 2B are a side sectional view (A) and a front view (B) of the measuring device 10. A support portion 12 is provided on the front surface of the main body 17 of the measuring device 10, and the thin film measurement kit 50 can be set on the support portion 12. The support portion 12 may be configured such that slits are formed on both sides of the sample mounting portion 101 and the thin film measurement kit 50 is inserted in the vertical direction to support the sample in a fixed position, or slits are formed above and below the sample mounting portion 101. Alternatively, the thin film measurement kit 50 may be inserted and supported in a fixed position. Alternatively, the support portion 12 may be configured with fasteners that fasten the four corners of the thin film measurement kit 50.

When the thin film measurement kit 50 is set on the thin film measurement support portion 12, the chamber 11 is formed inside the measuring device 10. The chamber 11 communicates with the supply port 15 and the discharge port 16. With the thin film measuring kit 50 set in the measuring device 10, the back surface of the thin film measuring kit 50 faces the inside of the chamber 11. The height h of the sample setting portion 101 including the support portion 12 and the chamber 11 is, for example, 50 mm, and the width W is, for example, 50 mm.

At the time of use, as shown in FIG. 1, a tube 18 or the like is connected to the supply port 15 and the discharge port 16, and a desired liquid or gas is introduced into the chamber 11 from the outside and discharged. SANS measurement is performed while introducing a gas or liquid into the chamber 11. The neutron beam is applied to the irradiation region R of the sample setting portion 101 through the slit 31 of FIG. A rotating goniometer that controls the angle of the thin film measuring kit 50 may be arranged inside the measuring device 10.

FIG. 3 is a schematic diagram of the thin film measurement kit 50. As shown in FIG. 3A, the thin film measurement kit 50 has a first substrate 51 made of silicon (Si) and a second substrate 52 having one or more through holes 55. The first substrate 51 and the second substrate 52 are held by the holder 53 in a state where the sample 60 is sandwiched between the first substrate 51 and the second substrate 52. The holder 53 may be a latch holder as shown in FIG. 3, or a slit or fastener formed in the support portion 12 of the measuring device 10 may be used as the holder 53.

The first substrate 51 can have an arbitrary thickness as long as a smooth surface can be formed on the surface of the thin film sample 60 in contact with the first substrate 51. As the first substrate, for example, a silicon substrate having a thickness of 5 mm is used. The second substrate 52 is made of a material having a small mass attenuation coefficient with respect to the neutron beam, such as silicon, aluminum (Al), and germanium (Ge). The thickness of the second substrate 52 is arbitrary as long as the sample 60 can be pressed against the first substrate 51 to form a smooth surface on the surface of the sample 60 and a through opening can be formed. Can be thickness. As an example, the thickness of the second substrate 52 is 2 to 5 mm.

When a silicon substrate is used as the second substrate 52, the through hole 55 is formed by laser processing using a YAG laser, femtosecond laser, etc., Fukahori RIE (Reactive Ion Etching), optical assist electrolytic etching, or the like. be able to. When an aluminum substrate is used as the second substrate, the through hole 55 can be formed by laser processing using a YAG laser or the like.

The sample 60 is a thin film sample such as a skin, an artificial biological membrane, a polymer membrane, and an electrolyte membrane. As shown in FIG. 3B, the sample 60 is sandwiched between the first substrate 51 and the second substrate 52, held by the holder 53, and irradiated with a neutron beam. The incident neutron beam NBin is incident on the surface of the sample 60 at a shallow angle via the first substrate 51. When the incident angle of the neutron beam is set to about 0.1 to 1.0 °, the neutron beam may be incident on the surface of the sample 60 from the edge of the first substrate 51.

The incident neutron beam NBin is reflected on the surface of the sample 60 at an angle substantially the same as the incident angle. The data measured by irradiating neutrons of different wavelengths (λ) include information such as the composition, structure, and state of the surface or interface of the sample 60. In the embodiment, the method of observing the equilibrium state of the microstructure on the surface of the sample 60 from the measurement result is called "static observation". On the other hand, the case of observing the movement of water molecules and protons in the thickness direction of the thin film of the sample 60 is called "dynamic observation". These two types of measurements can be carried out by the measuring device 10 only by controlling the incident angle of the neutron beam.

FIG. 4 is a schematic diagram of the thin film measurement of Example 1. In Example 1, as the thin film sample 60A, for example, a stratum corneum having a size of 50 mm × 50 mm is used. The horny layer is the outermost layer of the skin, and its thickness is about 20 μm. On the surface of the stratum corneum, fine irregularities are formed by the skin grooves and the skin hills. The surface side of the stratum corneum is brought into contact with the first substrate 51 of silicon and pressed by the second substrate 52 to form a smooth surface on the surface of the stratum corneum. As a result, the uneven surface of the stratum corneum is reconstructed on the smooth substrate surface.
(A) Supply of heavy water vapor to the back surface of the sample When the front surface side of the stratum corneum used as the sample 60A is arranged on the side of the first substrate 51, gas or liquid is discharged from the through hole 55 of the second substrate 52 to the back surface of the stratum corneum. Will be supplied. In this example, the steam of heavy water ₍ D2O) is introduced into the chamber 11 from the supply port 15 of the measuring device 10, and the steam of heavy water is applied to the back surface of the stratum corneum from the through hole 55 of the second substrate 52. Heavy water vapor migrates or diffuses from the back side to the front side of the stratum corneum. By GSANS measurement using the measuring device 10, the composition of the surface of the stratum corneum (static observation) and the wetting process (dynamic observation) can be measured.

FIG. 5 is a diagram showing a GSANS measurement result. A neutron beam is irradiated to the stratum corneum (sample 60A) at an incident angle of 0.5 °, and the reflected neutron beam NBref is detected by a detector to obtain a scattering profile in the reflection direction. The horizontal axis of FIG. 5 is the wave number q (Å ^-1 ) per 0.1 nm, and the vertical axis is the scattering intensity (arbitrary unit).

In the scattering intensity profile, the wave number at the point where the intensity change (gradient) starts from a certain level is the critical reflected wave number q _c . In FIG. 5, the critical reflected wavenumber q _c is 0.016 (Å ^-1 ). In Example 1, the incident angle of the neutron beam is constant and the wavelength λ is changed (using a white beam), but the same scattering intensity profile is obtained even when the wavelength λ is constant and the incident angle is changed. be able to. In this case, the angle at which the change in the scattering intensity starts becomes the critical reflection angle θ _c . The critical reflected wavenumber q _c or the critical reflection angle θ _c correlates with the composition of the surface of the sample 60A, and the surface state of the sample 60A can be evaluated.

In the region where the critical reflection angle θ _c (or the critical reflected wavenumber q _c ) is smaller than θ <θ _c (or q <q _c ), the reflectance becomes 1 (total reflection). The relationship between the critical reflection angle θ _c and the composition is given by Eq. (2).

θ _c = λ (ρb _av / π) ^1/2 (2)
Here, ρ is the density and _bav is the interference scattering length averaged by the composition of the film surface at the Fresnel interface.

In the above example, deuterium diffuses from the back surface of the stratum corneum used as sample 60A and reaches the Fresnel interface. Then, the composition of the surface of the stratum corneum changes, the coherent scattering length b _av changes, and θ _c changes. By specifying the critical reflection angle θ _c or the critical reflected wave number q _c , the composition of the film surface at that time can be identified.

The coherent scattering length _bav averaged by the composition of the Fresnel interface is defined by Eq. (3).

b _av (t) = (1-Φ) b _M + Φ [φ (t) b _D + (1-φ (t)) b _H ] (3)
here,
b _M : Average scattering length of the film b _H : Average scattering length of hydrogen (proton) b _D : Average scattering length of deuterium (duteron) Φ: Water content on the film surface φ (t): Time-dependent heavy water replacement rate ..

By obtaining φ (t) of the thin film, it is possible to quantitatively evaluate the diffusion coefficient (cm ² / sec) by performing model analysis according to Fick's law.

Returning to FIG. 5, the peak position of the scattering intensity profile can also be used to evaluate the surface condition of the sample 60A. In FIG. 5, peaks are observed at wavenumbers q = 0.05 and q = 0.1. The wave number q can be converted into the real space position d by the equation (4).

d = 2π / q (4)
0.05 (Å ^-1 ) corresponds to a real space position of 12.5 nm and 0.1 (Å ^-1 ) corresponds to a real space position of 6.2 nm.

These peaks are considered to be peaks derived from heavy water pooled in a 13 nm long-period lamellar structure and a 6 nm short-period lamellar structure in the lamellar structure (layered structure) of the intercellular qualities of the stratum corneum. That is, it is considered that the hydrogen (H) of the water (light water) contained in the lamellar structure is replaced with the deuterium (D) contained in the heavy water supplied from the back surface of the stratum corneum (sample 60A). Be done.

The reason why the peak in the short-period lamellar is larger is that the amount of water contained in the short-period lamellar is larger than the amount of water contained in the long-period lamellar, and the water molecules preferentially enter the short-period lamellar structure. Suggests. This phenomenon is consistent with the previous report.
(B) Supply of heavy water vapor to the surface of the sample In the thin film measurement kit 50 of FIG. 4, the back surface of the stratum corneum is brought into contact with the first substrate 51, and heavy water is applied to the front surface side of the stratum corneum from the through hole 55 of the second substrate 52. It is also possible to supply the steam of the above and measure the GSANS. The neutron beam is scattered on the back surface of the stratum corneum via the first substrate 51 of silicon. By detecting the reflection intensity of the neutrons reflected on the back surface of the stratum corneum, information such as the composition and structure of the back surface of the stratum corneum can be obtained.

By specifying the critical reflected wave number q _c or the critical reflection angle θ _c from the reflection intensity profile, the composition of the back surface of the stratum corneum can be evaluated based on the equations (2) and (3). In addition, the amount of water present in the short-period lamella and long-period lamella is estimated from the peak position and peak size of the scattering intensity profile, and the penetration of water into the stratum corneum when humidified from the surface of the skin is evaluated. be able to.
(C) Utilization of transmitted beam As shown in Fig. 3 (B), the angle of incidence of the neutron beam on the sample 60 is set larger than the critical reflection angle, and detectors are placed at the reflection and transmission positions. The reflected neutron beam NBref and the transmitted neutron beam NBtr may be detected at the same time. Neutrons pass through the second substrate 52 such as silicon and aluminum. The reflected neutron beam NBref carries information such as the composition and structure of the surface of the sample 60. The transmitted neutron beam NBtr carries information on the internal structure of the sample 60. By detecting the neutrons reflected by the sample 60 and the neutrons transmitted through the sample 60 with individual detectors, both the surface information and the internal information of the sample 60 can be detected by one measurement.
(D) Time change of critical reflection FIG. 6 is a diagram showing a time change of reflection intensity in the critical reflection region q <qc. It was fully humidified (100%) at room temperature, and the reflection intensity of the critical reflected wave number q _c = 0.016 (Å ^-1 ) in FIG. 5 was measured over a certain period of time. The upper curve of the figure is the measurement result when humidified from the front surface of the cornea with heavy water, and the lower curve is the measurement result of the reflection intensity when humidified from the back surface of the cornea.

When humidified from the front surface, the change in reflection intensity is gradual, but when humidified from the back surface, the change to the saturated state is steep. From this measurement result, it is considered that the water permeation rate in the stratum corneum is faster from the back surface to the front surface as compared with the front surface to the back surface. That is, it is suggested that the rate of water evaporation from the inside to the surface of the stratum corneum is faster than the rate of water supply from the surface to the inside.

FIG. 7 is a diagram showing the time change of temperature and humidity when humidified from the front surface of the stratum corneum, and FIG. 8 is a diagram showing the time change of temperature and humidity when humidifying from the back surface of the stratum corneum. In both FIGS. 7 and 8, the humidity is almost full humidification (100%) in the range of a few percent. The temperature is also constant within an error range of 2 ° C. From the temperature and humidity, we cannot find the difference between the front and back of the stratum corneum.

On the other hand, in FIG. 6, the difference in the time change of the reflection intensity depending on whether the humidification is performed from the front side or the back side of the stratum corneum is due to the difference in the composition or structure between the back surface and the front surface of the stratum corneum. .. The difference between the front and back of the stratum corneum structure can be grasped by the diffusion behavior of water shown by the time change in FIG.

By supplying deuterium from the back surface of the thin film sample 60A and observing the time change of the scattering intensity of neutrons on the surface, the infiltration state of deuterium on the surface can be traced (tracer method using isotopes). ).
(E) Modification example of measurement of the stratum corneum In Example 1, a normal (dried) stratum corneum was used as the sample 60A, and deuterium vapor was supplied to the stratum corneum to supply light hydrogen existing in the stratum corneum (e). The neutron reflectance was measured by substituting deuterium (proton) with deuterium. Instead of supplying the steam of heavy water to the back surface of the sample 60A, the GSANS measurement may be performed while supplying the steam of light water. In this case, the surface composition changes by substituting deuterium (duuteron) contained in sample 60A with light hydrogen (proton). By observing the time change of the reflectance at the critical reflection angle (or the critical reflected wave number), the infiltration state of light water into the sample 60A can be evaluated.

As yet another modification, a sample 60A in which the stratum corneum is previously immersed in heavy water or light water is sandwiched between the first substrate 51 and the second substrate 52 of the thin film measurement kit 50, and the sample is obtained from the through hole 55 of the second substrate 52. A dry air stream may be supplied to the back surface, and the composition of the surface of the sample 60 and the behavior of water molecules in the film thickness direction may be evaluated based on the isotope substitution of deuterium and light hydrogen.

Although the present invention has been described above based on the specific examples, the present invention is not limited to the above-mentioned examples. For example, as a thin film sample, an electrolyte membrane is sandwiched between a first substrate 51 and a second substrate 52, and the electrolyte membrane is obliquely irradiated with the neutron beam while supplying an electrolytic solution from a through hole 55 of the second substrate 52 to obliquely irradiate the electrolyte membrane. The infiltration behavior of the electrolytic solution into the water may be measured.

10 Measuring device 11 Chamber 12 Support 15 Supply port 16 Discharge port 17 Main body 50 Thin film measurement kit 51 First board 52 Second board 53 Holder 55 Through hole (through opening)
60, 60A Sample 101 Sample setting part

Claims (10)

A thin film sample is placed between the first substrate of silicon and the second substrate with one or more through openings.
With the second substrate, the first surface of the thin film sample is pressed against the first substrate, and at least one kind is applied to the second surface of the thin film sample opposite to the first surface from the through opening. While supplying a gas or liquid containing the substance of the above, the thin film sample is irradiated with a neutron beam through the first substrate.
A measuring method comprising detecting a reflected beam from the thin film sample and measuring the state of the surface of the first surface of the thin film sample. Measure the time change of critical reflection evaluated by neutron reflectance,
The measuring method according to claim 1, wherein the diffusion coefficient is quantitatively evaluated by tracking the time change of the water concentration in the first surface. The thin film sample is a dry thin film sample.
Heavy water or light water vapor is supplied to the second surface from the through opening.
The measuring method according to claim 1 or 2, wherein the composition of the light hydrogen or the deuterium in the first surface is measured based on the isotope substitution of the light hydrogen and the deuterium. The thin film sample is a sample obtained by immersing a dry thin film sample in light water or heavy water in advance.
A dry air stream is supplied to the second surface from the through opening, and the composition of the light hydrogen or deuterium in the first surface is measured based on the isotope substitution of light hydrogen and deuterium. The measuring method according to claim 1 or 2. At the same time as the reflected beam from the thin film sample, the transmitted beam of the thin film sample is detected.
Claims 1 to 4 are characterized in that information on the surface composition of the first surface of the thin film sample and information on the inside of the thin film sample are simultaneously acquired from the detection results of the reflected beam and the transmitted beam. The measuring method according to any one of the above items. The thin film sample is a skin or artificial biological membrane.
The first surface of the thin film sample is irradiated with the neutron beam while supplying heavy water vapor from the through opening.
The measuring method according to claim 1 or 2, wherein the state of permeation of water molecules into the thin film sample is measured. The thin film sample is a stratum corneum.
The surface of the stratum corneum is pressed against the first substrate,
While supplying the vapor of the heavy water to the back surface of the stratum corneum from the through opening, the surface of the stratum corneum is irradiated with the neutron beam through the first substrate to obtain the composition of the surface of the stratum corneum and water molecules. The measuring method according to claim 6, wherein the permeation state of the water is measured. The thin film sample is an electrolyte membrane.
The electrolyte membrane is irradiated with the neutron beam while supplying the electrolytic solution from the through opening.
Measuring the infiltration behavior of the electrolyte solution into the electrolyte membrane,
The measuring method according to claim 1 or 2. The measuring method according to any one of claims 1 to 8, wherein the neutron beam is incident on the thin film sample from the edge of the first substrate. With the main body
A sample installation unit that can support the sample in the neutron irradiation area on the front of the main body,
A chamber that forms a space inside the main body when the sample is set in the sample setting portion.
The supply port and the discharge port communicating with the chamber,
Have,
A neutron beam is incident on the interface of the sample at an incident angle where mirror reflection occurs while supplying gas or liquid from the chamber to the sample, and the surface state of the sample is changed while changing the incident angle or wavelength in the vicinity of the critical reflection angle. A measuring device that enables neutron scattering measurement.

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