JPS62140050A - Apparatus for measuring absorption characteristics of membrane - Google Patents

Abstract

PURPOSE:To measure the absorption characteristics of the membrane developed on the surface of a liquid with good accuracy and good sensitivity, by respectively irradiating a measuring area with exciting light and probe light modulated in intensity through the liquid at the incident angle entirely reflecting both lights on the surface of the liquid. CONSTITUTION:A liquid 3 developing a membrane 2 on the surface 1 thereof is received in a liquid tank 4 and exciting light 5 from an exciting light source 6 is allowed to irradiate the measuring area of the membrane 2 on the surface of the liquid 3 through the liquid 3 at an incident angle totally reflecting said light 5 on the surface of the liquid 3. Said exciting light is modulated in intensity by a luminous intensity modulator 7 before arrives the measuring surface to irradiate the same. Probe light 8 is emitted from a probe light source 9 to irradiate the measuring area through the liquid 3 at an incident angle totally reflected on the surface 1 of the liquid. The deflection quantity of the probe light 8 passing through the measuring area is detected by a detector 10 and scattering lights of the exciting light 5 and probe light 8 from the membrane 2 on the surface of the liquid 3 are detected by an infrared TV camera 14. As mentioned above, by monitoring the converging states of luminous fluxes of the exciting light and probe light or the relative positional relation thereof by the camera 14, the light path during measurement can be easily adjusted.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention particularly relates to a method for optically measuring the characteristics of a thin film developed on a liquid surface, and more specifically, to a method for optically measuring the characteristics of a thin film developed on a liquid surface. This invention relates to a device for measuring light absorption characteristics, which is the basis of. INDUSTRIAL APPLICATION This invention is utilized for the characteristic analysis etc. of the monomolecular film spread on the liquid surface to accumulate, for example when forming a monomolecular cumulative film.

[Prior Art] Conventionally, as a device for measuring the light absorption characteristics of an object to be measured,
There is a device that determines light absorption characteristics from transmittance or reflectance.

However, when a measured object is irradiated with light, there is scattered light in addition to transmitted light and reflected light, and in order to achieve even higher accuracy, it is important to directly measure the absorption component of light in evaluating light absorption characteristics. becomes.

A method for directly measuring the absorbed components of light is a measurement method that utilizes the fact that when the object is irradiated with light intermittently, the light energy absorbed by the object to be measured is intermittently converted into heat through a non-radiative relaxation process. Photoacoustic spectrometer (Photoac)
oustic 5pectroscopy: PAS)
and photothermal radiation spectrometer (Photothermal Rad)
iometry: PTR).

In addition, Toshite, a device that directly measures the absorption components of light,
Photothermal deflection spectrometer
ction 5pectroscopy: PDS
) There is a device called. This PDS device utilizes the fact that the refractive index changes as heat is generated due to light absorption of the object to be measured, and a temperature distribution occurs within and in the vicinity of the object to be measured, thereby deflecting the light that enters the object. . That is,
excitation light that causes a temperature distribution due to heat generation and changes the refractive index when the light is absorbed at the measurement site of the measured object;
A probe light for measuring the amount of deflection caused by this is irradiated, and the light absorption characteristics of the object to be measured are measured from the wavelength of the excitation light and the amount of deflection of the probe light. This device can set the object to be measured and the detection system independently, and is suitable for on-site measurement and remote measurement, and the basic principle of the present invention is also the same as this PDS device.

The above-mentioned PDS device can be of transverse type or vertical type depending on the arrangement of excitation light and probe light.
There are two types (linear) type, and both measure the amount of deflection of the probe light according to the amount of excitation light absorbed by the object to be measured, as described above, and the detector is a position-sensitive detector (
PSD) is often used.

FIG. 5(a) shows an example of a vertical type, in which the excitation light 5 emitted from the excitation light source 6 is interrupted or adjusted in intensity by a light intensity modulator 7, and is focused by a lens 13b to the object to be measured. is irradiated. The probe light 8 emitted from the probe light a9 passes through the lens 13.
When the excitation light 5 is transmitted through the measurement part of the object 2' to be irradiated by the optical path adjuster 25 such as a and a mirror and reaches the detector 10, the amount of deflection is as shown by the dotted line. be measured. FIG. 5(b) shows an example of the horizontal type, which is the same as the vertical type except that the probe light 8 is irradiated parallel to the surface of the object to be measured 2'.

Theoretical handling of this PDS device is to solve the heat conduction equation within the object to be measured, and the amount of deflection measured as the deflection angle φ is determined by the excitation light intensity and the temperature coefficient of the refractive index (an/a
T), the temperature gradient (a
It will be proportional to T/a, etc.

The term proportional to the light absorption coefficient of the object to be measured is included in (aT/a). Also, (an/δT) can take either a positive or negative value depending on the object to be measured, which means that the deflection angle can also be positive or negative. This shows that both cases are possible.

On the other hand, conventionally, a monomolecular cumulative film forming apparatus is known in which monomolecular films are layered one by one and transferred to a substrate by a monomolecular film cumulative method called the Langmuir-Prodgett method (hereinafter referred to as LB method) named after the inventor. (New Experimental Chemistry Course 1)
Volume 8, pp. 488-507, round lid).

The above device consists of a liquid tank containing a liquid, a film forming frame that is floated in the liquid tank so as to divide the liquid surface into two, and is capable of two-dimensional piston movement within the liquid tank, and a film forming frame that moves the film forming frame. It is generally composed of a driving device, a surface pressure measuring device that measures the surface pressure of a monomolecular film spread on the liquid surface, and a substrate holder that moves the held substrate up and down with respect to the liquid surface. The formation of a monomolecular film using this apparatus and its transfer to a substrate are performed as follows.

First, with the film forming frame shifted to one side of the liquid tank,
A few drops of a solution of a membrane constituent material dissolved in a volatile solvent such as benzene or chloroform at a concentration of 5 x 10-3 moff/ρ are dropped onto the liquid surface using a dropper or the like. When this solution spreads on the liquid surface and the solvent evaporates, a monomolecular film will be left on the liquid surface.

The monomolecular film exhibits two-dimensional behavior on the liquid surface. When the areal density of molecules is low, it is called a gas film of secondary gas,
A two-dimensional ideal gas equation of state is established between the occupied area per molecule and the surface pressure.

Next, from this gas film state, the film formation frame is gradually moved to reduce the area of the liquid surface where the monomolecular film is developed and increase the molecular surface density, which strengthens the intermolecular interactions. ,
It changes from a liquid film of two-dimensional liquid to a solid film of two-dimensional solid. In this solid film, the arrangement and orientation of each molecule is neatly aligned, resulting in a high degree of order and uniform ultra-thin film properties. At this time, by moving the substrate holder to move the substrate up and down, the monomolecular film, which has become a solid film, can be attached to the surface of the substrate and transferred. Moreover, a monomolecular cumulative film can be obtained by transferring a monomolecular film to the same substrate multiple times. Incidentally, as the substrate, for example, glass, synthetic resin, ceramic, metal, etc. are used.

In order to carry out the transfer operation under the condition of the monomolecular film suitable for transfer to the substrate, the surface pressure of the monomolecular film is measured. Generally, the surface pressure of a monomolecular film suitable for transfer is 15 to 30 dyn/cm.

Outside this range, the arrangement and orientation of molecules may be disturbed and the film may easily peel off. However, in special cases, for example, depending on the chemical structure of the membrane constituents, temperature conditions, etc., the suitable surface pressure value may exceed the above range, so the above range is only a rough guide.

The surface pressure of the monomolecular film is automatically and continuously measured by a surface pressure measuring device. Surface pressure measuring devices include those that apply the method of determining the surface tension from the difference in surface tension between the liquid surface that is not covered with a monomolecular film and the liquid surface that is covered with a monomolecular film; There are methods that directly measure the two-dimensional pressure applied to a floating film forming frame that separates the liquid surface that is not covered with a monomolecular film from the liquid surface that is covered with a monomolecular film, and each method has its own characteristics. In addition to the surface pressure, the occupied area per molecule of the monomolecular film and the amount of change thereof are also usually measured. The occupied area and the amount of change thereof are determined from the left and right movement of the film forming frame.

The movement of the film forming frame described above is controlled based on the surface pressure of the monomolecular film measured by the measuring device.

In other words, the driving device that moves the film forming frame maintains a constant surface pressure of the monomolecular film selected within a range suitable for the transfer operation, so that the surface of the monomolecular film measured by a surface pressure measuring device is used to move the film forming frame. Controlled based on pressure. This movement control of the film forming frame is performed not only when the monomolecular film transfer operation is started after the solution of the film constituent material is dropped, but also continuously during the transfer operation. For example, in a transfer operation, as the monolayer is transferred to the substrate, the areal density of the monolayer molecules on the liquid surface decreases, and the surface pressure also decreases. Therefore, the film forming frame is moved to reduce the area in which the monomolecular film is developed, and the resulting drop in surface pressure is corrected to maintain a constant surface pressure.

[Problems to be solved by the invention] However, it is difficult to measure a very thin object under a unique environment, such as a thin film such as a monomolecular film spread on a liquid surface.
If you try to use a PAS device, PTR device, or PDS device as is, the problem is that the measurement itself becomes difficult and accuracy and sensitivity tend to decrease because the object to be measured is on the liquid surface or is very thin. There is.

PAS devices can be divided into microphone type and piezoelectric element type depending on the type of detector, but the microphone type requires the sample to be placed in a sealed sample chamber, and the piezoelectric element type has restrictions on the arrangement of the detector and sample. Therefore, both methods are unsuitable for measuring thin films spread on the liquid surface as they are.

Furthermore, in PDS measurement, the state of convergence of the light beams of the excitation light and the probe light affects the sensitivity, and the relative positional relationship between the excitation light and the probe light also greatly influences the sensitivity. Therefore, it is necessary to monitor the irradiation positions of the excitation light and probe light and their relative positions.
The scattered light of the excitation light and probe light has been visually monitored using a microscope, but this method introduces unnecessary disturbances such as vibrations of the liquid surface. Furthermore, when measuring light absorption characteristics, the wavelength used is not limited to visible light; for example, when infrared light is used, there is a drawback that the irradiation position cannot be visually confirmed.

On the other hand, as mentioned above, various delicate adjustments are required to obtain a monomolecular cumulative film. However, until now it has not been possible to know what conditions are optimal without conducting various experiments, and whether or not the monomolecular film on the liquid surface is in a suitable state for accumulation depends on factors such as surface pressure. This can only be confirmed indirectly, and lacks accuracy. This is PAS.

If it were possible to directly grasp the physical properties of the monomolecular film on the liquid surface using a PTR or PDS device, it would be much improved, but
Due to the problems mentioned above, the current situation is that even if there is a request, it cannot be accommodated.

An object of the present invention is to enable accurate and sensitive measurement of the light absorption characteristics of a thin film spread on a liquid surface, which is extremely thin and under a unique environment.

[Means for solving the problems] The means taken to solve the above problems in the present invention will be explained with reference to FIG. 1, which corresponds to an embodiment of the present invention. A liquid bath 4 containing a liquid 3 for developing a thin film 2 and an excitation light 5 irradiated from below the liquid surface to a measurement site of the thin film 2 on the liquid surface 1 at an incident angle that is totally reflected by the liquid surface 1. An excitation light source 6, a light intensity modulator 7 that modulates the intensity of the excitation light 5 before it reaches the measurement site, and a probe light 8 that is irradiated from below the liquid surface 1 to the measurement site at an incident angle such that it is totally reflected by the liquid surface 1. A probe light source 9 that emits a probe light source 9, a detector 10 that detects the amount of deflection of the probe light 8 that has passed through this measurement site, and a thin film 2 on the liquid surface 1 that detects the excitation light 5 and the scattered light of the probe light 8. The purpose of the present invention is to provide a thin film light absorption characteristic measuring device having an infrared television camera 14.

[Function] In the measuring device according to the present invention, the excitation light 5 at the thin film 2
, an infrared television camera 1 that detects scattered light of the probe light 8
4, and a thin film 2 of excitation light 5 and probe light 8.
The magnitude and relative position of the luminous flux above can be monitored. Therefore, measurements can always be performed under the same conditions even when using different films. Furthermore, probe light 8. Even when using a wavelength other than the visible range as the wavelength of the excitation light 5, by using the infrared television camera 14 that is sensitive to this wavelength,
The optical path can be easily adjusted, allowing highly accurate measurements.

[Example] Figures 1 to 3 show an example of the present invention when used in a monomolecular cumulative film forming apparatus.

In FIG. 1, reference numeral 4 denotes a liquid tank containing a liquid 3, and a thin film 2, which is an object to be measured, is spread on the liquid surface 1 of the tank. The illustrated thin film 2 is a schematic representation of a monomolecular film.

A probe light source 9 is provided on the side of the liquid 4114 and slightly below. The probe light 8 is emitted from this probe light source 9 at an angle at which it is totally reflected by the liquid surface 1 on which the thin film 2 is developed.
is irradiated from the liquid 3 side toward the measurement site of the thin film 2. Further, a detector 1O for detecting the position of the probe light 8 sent is provided at a position facing the probe light source 9 and the liquid tank 4 therebetween. The signal of this detector 10 is
The signal is sent to the lock-in amplifier 12 via the dry/<-11.

Further, an excitation light source 6 is provided on the side of the liquid tank 4 and slightly below. The excitation light source 6 irradiates the excitation light 5 toward the measurement site of the thin film 2 at an angle such that it is totally reflected by the liquid surface l on which the thin film 2 is spread. A light intensity modulator 7 such as a chopper or a variable filter is provided at a position along the optical path of the excitation light 5 to make the excitation light 5 into intermittent light or to irradiate the light with varying intensity. In addition, the excitation light 5
is further focused by a lens 13 and irradiated onto the measurement site of the thin film 2.

Scattered light of the excitation light 5 and the probe light 8 on the thin film 2 on the liquid surface 1 is collected by a lens 26 and guided to the infrared television camera 14, where the excitation light 5 and the probe light 8 on the liquid surface 1 are collected. spot will be output on the TV screen.

The light intensity modulator 7 is connected to a lock-in amplifier 12, and can synchronously detect the signal from the detector 10 using a signal indicating the intermittent or strong/weak state of the excitation light 5 sent from the light intensity modulator 7 as a reference signal. It looks like this.

The liquid tank 4 does not need to be entirely transparent as long as a transparent window is provided at least in the portion that becomes the optical path of the probe light 8 and the excitation light 5. In addition, if the liquid 3 has a small absorption of the excitation light 5, even if it has a direct influence on the probe light 8, it will not have much of an adverse effect on the measurement, but it is preferable that the liquid 3 be transparent.

In the above configuration, first, the excitation light 5 emitted from the excitation light source 6 is modulated by the light intensity modulator 7 into intermittent or variable intensity light, and is incident such that the incident angle is larger than the critical angle of the liquid 3. Then, the measurement area of the thin film 2 spread on the liquid surface 1 of the liquid tank 4 is irradiated. That is, the excitation light 5
is totally reflected on the liquid surface. In the area on the measurement site that is irradiated with the excitation light 11, the thin film 2 on the liquid surface 1 absorbs the light and generates heat intermittently or with varying degrees of intensity due to a non-radiative radiation process, which causes a change in the refractive index in the vicinity. will occur intermittently.

On the other hand, the probe light 8 emitted from the probe light source 9 is
The light is incident so that the angle of incidence is larger than the critical angle of the liquid 3, is totally reflected at the irradiated part of the excitation light 5 on the liquid surface 1, passes through the liquid 3, and is absorbed by the absorber 27 provided outside the liquid tank 4. be done. Therefore, the probe light 8 passes through a measurement site whose refractive index changes intermittently by irradiation with the excitation light 5.

When the probe light 8 emitted from the probe light source 9 passes through a region where the refractive index changes intermittently, the optical path is deflected as shown by the dotted line in accordance with the changed refractive index distribution.

Excitation light from thin film 2 on liquid surface 5. Scattered light of the probe light 8 is captured by an infrared television camera 14, and excitation light 5. A spot of probe light 8 is output on the screen.

While monitoring this spot, it is possible to adjust the magnitude of the luminous flux of the excitation light and the probe light as well as the relative positions of the two spots of the excitation light and the probe light.

The detector IO continuously receives the probe light 8 and sends the receiving position of the probe light 8 to the lock-in amplifier 12 via the driver 11. The lock-in amplifier 12 receives the signal from the optical intensity modulator 7 at the same time as receiving the signal from the detector 10, and by synchronizing both signals,
The light receiving position signal of the probe light 8 when the excitation light 5 is irradiated or at high intensity, and the probe light 8 when the excitation light 5 is not irradiated or at low intensity
The difference between the light receiving position signal and the light receiving position signal is detected with a good S/N ratio. The detected difference corresponds to the amount of deflection of the probe light 8, and based on this, the light absorption characteristic at the wavelength of the excitation light 5 can be calculated. Therefore, by sequentially changing the wavelength of the excitation light 5, the thin film 2
It is possible to obtain the spectral absorption characteristics of

The light energy absorbed by the thin film 2 is determined from the light intensity distribution of the excitation light 5 at the measurement site, the characteristics of the refractive index change due to heat of the liquid 3, the incident beam position of the probe light 8, and the amount of deflection at that time.

Therefore, by monitoring the irradiation energy of the excitation light 5 onto the thin film M2 using a photosensor or the like, the absolute light absorption characteristics of the thin film 2 can be obtained from both. Then, by changing the wavelength of the excitation light 5, absolute spectral absorption characteristics can be obtained. Further, the relative spectral absorption characteristics can be obtained by simply determining the relative intensity of the excitation light 5 at each wavelength in advance and determining the amount of deflection of the probe light 8 corresponding to the wavelength. The relative value and absolute value of the light absorption characteristic may be appropriately selected depending on the purpose of measurement.

Incidentally, the structure around the liquid tank 4 is similar to that of a conventional monomolecular cumulative film forming apparatus using the LB method, and this will be explained with reference to FIGS. 2 and 3.

The liquid tank 4 has a wide and shallow rectangular shape, and an inner frame 16 made of polypropylene or the like is suspended horizontally inside the tank 4 to partition the liquid level 1. As the liquid 3, pure water is usually used. A film forming frame 17 made of, for example, polypropylene is floated inside the inner frame 1B. Film forming frame 17
The book is a rectangular parallelepiped whose book is slightly shorter than the inner width of the inner frame 16, and is capable of two-dimensional piston movement in the left and right directions in the figure. A weight 3118 for pulling the film forming frame 17 to the right in the figure is tied to the film forming frame 17 via a pulley 19. Further, there are provided a magnet 20 fixed on the film forming frame 17 and counter magnets 21 which are movable from side to side in the figure above the film forming frame 17 and repel each other when approaching the magnet 20. Accordingly, the film forming frame 17 can be moved from side to side in the figure and stopped. Instead of such a weight 18 or a set of magnets 20, 21, there is also a system that uses a rotary motor or a pulley to directly move the acid fl1N7.

Suction nozzles 23 connected to a suction pump (not shown) via a suction vibrator 22 are provided on both sides of the inner frame 16.
are lined up. This suction nozzle 23 quickly removes unnecessary monomolecular films from the previous process on the liquid surface l in order to prevent impurities from being mixed into the monomolecular film or monomolecular cumulative film. It is used for. Note that 15 is a board that is attached to the board holder 24 and is vertically moved up and down.

The principles of forming a monomolecular film and obtaining the cumulative film using the above-described monomolecular cumulative film forming apparatus are basically the same as those of the conventional method.

As a method of forming a film, first, the film forming frame 17 is moved,
The liquid surface 1 is purified by sweeping up any unnecessary monomolecular film or the like on the liquid surface 1 and sucking it out from the suction nozzle 23. Next, the film forming frame 17 is moved to one end of the liquid tank 4, and after dropping the film constituent material onto the liquid surface l, the film forming frame 17 is moved to narrow the development area, and after forming a solid film, the substrate 15 is moved up and down. Then, the formed monomolecular film can be transferred.

By the way, in the apparatus according to this embodiment, as explained in FIG. 1, the physical properties of the thin film 2, which is a monomolecular film spread on the liquid surface 1, can be directly measured on the spot optically. .

Therefore, if the movement of the counter magnet 21, that is, the movement of the film forming frame 17, is controlled by the measurement controller 14 based on this measurement from the formation of the monomolecular film to the completion of its transfer, a monomolecular film with desired physical properties can be obtained. can be reliably accumulated on the substrate 15.

FIG. 4 shows another embodiment in which the excitation light 5 is irradiated. Although the excitation light 5 has a different incident angle from the probe light 8, the excitation light 5 and the probe light 8 illuminate the thin I pattern 2. The light is totally reflected at the liquid level l at the measurement site. In this way, it is possible to minimize disturbance of the excitation light 5 due to dust in the air or fluctuations, and further improve accuracy.

[Effects of the Invention] As explained above, according to the present invention, by monitoring the convergence state of the luminous flux of the excitation light and the probe light and their relative positional relationship with an infrared television camera, It is possible to easily adjust the fluctuations in the optical path of the liquid, and the physical properties of the thin film developed on the liquid surface can be accurately determined by measuring the light absorption characteristics with high precision and sensitivity, making the measurement work easier. It can be made into something. Therefore, when used in a monomolecular cumulative film forming apparatus, a monomolecular cumulative film with extremely high characteristic accuracy can be obtained.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention when used in a monomolecular cumulative film forming apparatus, Figs. 2 and 3 are explanatory diagrams of the liquid tank and its surroundings, and Fig. 4 is an excitation light irradiation diagram. FIGS. 5(a) and 5(b) are explanatory diagrams showing other embodiments of the prior art. 1: liquid surface, 2: thin film, 3: liquid, 4: liquid bath, 5: excitation light, 6: excitation light source, 7: light intensity modulator, 8 niblob light, 9 niblob light source, 10: detector. 11: Driver, 12: Lock-in amplifier, 13:
Lens, 14: Infrared television camera, 15: Board, 16:
Inner frame, 17: Film forming frame, 18: Weight, 19: Pulley, 20:
Magnet, 21: Pair magnet, 22: Suction pipe, 23: Suction nozzle, 24: Substrate holder, 25: Optical path adjuster, 26: Lens, 27: Absorber.

Claims (1)

[Claims] 1) A liquid tank containing a liquid that spreads a thin film on the liquid surface;
An excitation light source that emits excitation light that is irradiated onto a measurement site on a thin film above the liquid surface, a light intensity modulator that modulates the intensity of the excitation light before it reaches the measurement site, and a probe that irradiates the measurement site from below the liquid surface. A probe light source that emits light, a detector that detects the amount of deflection of the probe light that has passed through the measurement site, a television microscope that displays the excitation light and scattered light of the probe light at the measurement site, and adjusts the optical path. 1. An apparatus for measuring light absorption characteristics of a thin film, comprising a television receiver.