KR100222320B1 - Magneto-optical and ellipsometric spectrometer - Google Patents

Abstract

The present invention simultaneously performs the functions of a magneto-optical Kerr spectrometer that can measure the magneto-optical rotation angle and ellipticity by changing the wavelength of light and a spectroscopic ellipsometer that can measure the optical characteristics. An optical magneto-ellipse spectrometer provided, comprising: a light source for generating a beam for irradiating a first sample and a second sample placed in two different directions; Magneto-optical means for causing the beam irradiated by the magneto-optical effect of the first sample placed in the magnetic field on the beam irradiated from the light source to be input to a later double photodetector; Spectroscopic elliptic analysis means for causing the beam irradiated from the light source to change its polarization state by the optical property of the second sample and input the dual light detection means; Rotation angle and ellipticity are selectively increased by using dual light detecting means for selectively receiving the light input from the magneto-optical means and the spectroscopic elliptic analysis means and outputting the light to the optical measuring means. Provides a magneto-optic and ellipscopy spectrometer composed of optical measuring means for performing a magneto-optical spectroscopic analysis function or a spectroscopic ellipsoid analysis function for measuring a complex refractive index. It is possible to study the magneto-optical effect that must be used independently by using a single device, thereby maximizing the ease of analysis and interpretation of data as well as the cost reduction in manufacturing.

Description

Magneto-optical spectroscopy

The present invention simultaneously performs the functions of a magneto-optical Kerr spectrometer that can measure the magneto-optical rotation angle and ellipticity by changing the wavelength of light and a spectroscopic ellipsometer that can measure the optical characteristics. It relates to a magneto-optical and ellipscopy spectrometer equipped.

The magneto-optical effect is a phenomenon in which the polarization state of the light reflected from the magnetic material is changed by the influence of the magnetized sample. In this case, when the linearly polarized light is elliptically polarized, the angle of rotation of the polarization axis is increased, and the rotation angle is referred to as an ellipticity of an arc tangent of the ratio between the long axis and the short axis of the ellipse.

This magneto-optical effect is a physical phenomenon that occurs due to the spin-polarized band structure of the sample, which causes the electrons aligned in the positive direction and the electrons aligned in the negative direction to the light. To understand this effect, a measurement of the dielectric tensor of the sample is required. At this time, the dielectric constant tensor of the sample magnetized in the z direction, which is the simplest case, has the shape as shown in Equation 1 below.

_XX

_xx

n²의 관계를 가진다.Diagonal component in the formula 1

_XX

_xx

has a relationship of n ² .

_K는 아래와 같은 식 2로 나타내진다.In addition, when light is incident on a medium having a refractive index of n ₀ , the magneto-kerr effect θ _K and the ellipticity

_K is represented by following formula (2).

_xy에 있다고 정의할 수 있다. 그러므로, 광자기 커 효과(Kerr effect)를 제대로 이해하기 위해서는 반드시 유전율 텐서의 비대각 성분인

_xy를 측정해야 한다.Thus, the cause of the magnetoelectric Kerr effect is the non-diagonal component of the dielectric constant tensor.

Can be defined to be in _xy . Therefore, in order to understand the Kerr effect properly, the non-diagonal component of the dielectric tensor

_xy should be measured.

_xy를 측정하기 위해서는 커 회전각과 타원율, 그리고 복소 굴절률을 독립적으로 측정해야 하는 것으로 알려져 있다(W. Reim and J. Schoenes, "Ferromagnetic Materials," Vol. 5 edited by E. P. Wohlfarth, and K. H. J. Buschow, North-Holland, Ch.2, 134 (1990) 참조).In this case, the non-diagonal component of the dielectric constant tensor

_In order to measure _xy , it is known that Kerr rotation angle, ellipticity and complex refractive index must be measured independently (W. Reim and J. Schoenes, "Ferromagnetic Materials," Vol. 5 edited by EP Wohlfarth, and KHJ Buschow, North- See Holland, Ch. 2, 134 (1990)).

Therefore, in order to properly study the Kerr effect, a magneto-optical spectrometer capable of measuring the Kerr effect and the ellipticity and a spectroscopic elliptic analyzer capable of measuring the complex refractive index are necessary.

First, looking at the instruments that measure the Kerr effect, the most basic method is the quadrature polarizer method. The advantage of this method is that the device is simple. However, since accuracy is poor and ellipticity is difficult to measure, it is not currently widely used.

Alternative methods include Faraday Cell and Rotational Probe, but both of these methods use λ / 4 plates or Soleil-Barnet Compensators (Soleil-) suitable for each wavelength to measure ellipticity. Babinet compensators need to be adjusted for each wavelength. Therefore, Kerr spectroscopy of phase modulation method using photoelastic modulator (PEM) that can measure Kerr rotation angle and ellipticity at the same time is the most suitable for this application. 296 (1995)).

In the case of a spectroscopic ellipsometer showing optical properties, the most common method is a rotational analyzer / polarizer method (Sang-Yeul Kim, 1, 73 (1990), RM Azzam and NM Bashara, "Ellipsometry and polarized light, "(North-Holland Co. 1979).

Another method is a phase modulated spectroscopic ellipsometer using a photoelastic modulator, which is a popular method in recent real-time measurement due to the fast analysis speed.

Therefore, as pointed out above, the magneto-optical spectrometer and the spectroscopic ellipsometer are essential for the study of the magneto-optical effect. However, since the two pieces of equipment have to be manufactured or purchased independently, a problem arises in that the cost is very large.

An object of the present invention for solving the above problems is to combine the two devices into a single device by using the common point of the two devices, the magneto-optical spectrometer and the spectroscopic ellipsometer which are essential for the study of the magneto-optical effect To provide a magneto-optical and ellipsometric spectrometer for.

1 is a schematic diagram of a magneto-optical and ellipscopy spectrometer according to the present invention.

2 is a schematic view of a housing of a Xe-lamp.

3 is a schematic representation of a double-monochromator.

* Explanation of symbols for main parts of the drawings

1: light source 2: first ellipsoid

3: first polarizer 4: first sample

5: electromagnet 6: first photoelastic modulator

7: first analyzer 8: second ellipsoid

9 double light detecting means 10 light measuring means

11: third ellipsoidal 12: second polarizer

13 second photoelastic modulator 14 second sample

15: second analyzer 16: fourth ellipsoid

Configuration according to a preferred embodiment of the present invention for achieving the above object is as shown in FIG.

That is, a light source for generating beams irradiated to the first sample and the second sample placed in different directions, and a beam that is elliptically polarized by the magneto-optical effect of the first sample placed in the magnetic field is emitted from the light source. Magneto-optical means for inputting to the dual photodetecting means, spectroscopic elliptic analytical means for changing the polarization state of the beam irradiated from the light source due to the optical properties of the second sample and inputting the dual photodetecting means; Rotation angle and ellipticity are selectively increased by using dual light detecting means for selectively receiving the light input from the magneto-optical means and the spectroscopic elliptic analysis means and outputting the light to the optical measuring means. Optical measuring means for performing a magneto-optical spectroscopic function for measuring or for performing a spectroscopic elliptic analysis for measuring complex refractive index It is configured to include.

In addition, the magneto-optical means is placed at a predetermined position in a predetermined shape so that the irradiation beam generated from the light source is incident perpendicularly to the first sample, the first ellipsoidal mirror to increase the intensity of the incident light, and the first ellipsoidal mirror A first polarizer for polarizing the beam passing therethrough, an electromagnet for generating a magnetic field so as to be elliptically polarized by a magneto-optical effect when the irradiation beam passing through the first polarizer is incident and reflected perpendicularly to the first sample, and an elliptical polarization A first photoelastic modulator for modulating the phase of light sequentially placed on a path where the irradiated beam is incident on the dual light detecting means, a first analyzer for detecting a component projected in the direction of the optical axis from the polarized light, and a first detector And a second ellipsoid reflecting the light passing through the ruler to the incident slit of the double photodetecting means.

In addition, the spectroscopic elliptic analysis means includes a second polarizer for linearly polarizing the irradiation beam generated by the light source and a phase of light before the linearly polarized irradiation beam is incident on the second sample at a predetermined inclination angle. A second photoelastic modulator for modulating and a polarized state whose polarization state is changed by the optical properties of the second sample, and the light of the polarization state in which the reflected beam is sequentially placed on the path incident to the dual photodetector means in the direction of the optical axis And a second ellipsometer for detecting the projected component and a fourth ellipsoid for reflecting the light passing through the second analyzer to the incident slit of the dual photodetecting means.

In addition, the dual light detecting means has two incidence slits for inputting the beam from the magneto-optical means and the spectroscopic elliptic analytical means, and a plane for selectively irradiating the irradiation beam to any one of the two incidence slits. And a mirror, an angle adjusting means for adjusting the angle of the planar mirror, and routing means for setting a path so that the beam reflected from the plane mirror is input to the optical measuring means through an output slit.

Hereinafter, with reference to the accompanying drawings will be described the operation of the magneto-optical and ellipscopy spectrometer according to a preferred embodiment of the present invention having the above-described configuration.

First, the operation characteristics of the magneto-optical spectrometer and the spectroscopic ellipsometer to be combined in the present invention, first of all, the principle of the magneto-optical spectrometer is to inject the linearly polarized light perpendicularly to the sample to which the external magnetic field is applied The polarization state of light changed by the Kerr effect is measured.

In the case of a spectroscopic ellipsometer, the state of the elliptical polarization caused by the difference in the reflection coefficients of the p wave and the s wave of the light when the linearly polarized light is incident on the sample at an oblique angle. Thus, the commonality between the two instruments is to measure the state of change in polarization, and the difference is the angle of incidence of light and the presence of an applied magnetic field.

Thus, if you build only two ellipsoids with a common light source and a common photodetector part, and use a polarizer, a detector, and a photoelastic modulator in common, you can easily add a spectroscopic ellipsometer to the photomagnetic beaker spectrometer. This is the technical idea of the present invention.

The magneto-optic and ellipsoidal spectrometer proposed by the above-described technical idea, as shown in FIG. 1, light emitted from the light source (xenon lamp) 1 is reflected by the first ellipsoidal mirror 2, and thus the first polarizer 3 After passing through), it is incident almost perpendicularly to the first sample 4 placed in the magnetic field generated by the electromagnet 5. At this time, the light passing through the first polarizer 3 is incident on the first sample 4 in a linearly polarized state, and the light reflected from the first sample 4 placed in the magnetic field is reflected in the first sample ( It becomes elliptical polarization by the magneto-optical effect of 4).

Subsequently, the light reflected by being elliptically polarized and reflected by the magneto-optical effect of the first sample 4 is incident on the first photoelastic modulator 6 to modulate the phase, and the light in the polarized state is emitted from the first analyzer 7. The component projected in the direction of the optical axis is detected and reflected by the second ellipsoidal mirror 8 and then enters the dual light detecting means 9 through the incident slit.

The change in the polarization state of light at this time can be expressed by the following Equation 3 using a Jones matrix.

P, A, S, and M are polarizers, analyzers, samples, and photoelastic modulators, respectively, and are Jones matrices given by Equation 4 below.

₀sin

로 주어지는데,

₀는 광탄성 변조기의 광학 헤드 부분의 변조 크기이며,

는 진동수이다. 또,

는 각각 좌, 우 원편광의 반사계수이다.here,

₀ sin

Given by

₀ is the modulation size of the optical head portion of the photoelastic modulator,

Is the frequency. In addition,

Are the reflection coefficients of left and right circularly polarized light, respectively.

At this time, the other optical system except for the sample is described in the linear polarization system, and the sample is described based on the circular polarization system with the left and right circularly polarized states as the basis vector. Therefore, to change these two coordinate systems, we need a matrix called F as shown in Equation 5 below.

π/4 이라고 하면 경우 아래의 식 6과 같이 된다.At this time, the measured intensity of light is an example of the angle of the analyzer as a

In the case of π / 4, Equation 6 below is used.

Here, using the following definition and the properties of the Bessel function, a relational expression can be obtained as shown in Equation 7 below.

Therefore, according to Equation 7, the same result as in Equation 8 below can be obtained.

Here, J ₀ , J ₁ , and J ₂ are 0, 1, and quadratic functions of the Bessel function, respectively, and A and B are constants determined through quantification. Therefore, the Kerr rotation angle and the ellipticity to be obtained can be measured by measuring the direct current component, the first harmonic wave, and the second harmonic wave with respect to the modulation frequency of the photoelastic modulator.

Now, let's take a look at the measuring principle of the spectroscopic ellipsometer. Similar to the case of the magneto-optical spectrometer, the light from the light source 1 is reflected by the third ellipsoid 11 and passes through the second polarizer 12 so that linearly polarized light After passing through the second photoelastic modulator 13, the phase of the light is modulated and then incident on the second sample 14 at an inclination angle 60-70 ⁰ .

In this case, the polarized state of the light reflected by the second sample 14 is changed again by the optical property of the sample. The light containing the information about the optical properties of the sample is detected again by the second analyzer 15, the component projected in the direction of the optical axis is reflected by the fourth ellipsoid 16, the dual light detection means 9 Incident to the incident slit.

This process can be expressed using the Jones matrix as shown above, as shown in Equation 9 below.

Here, the difference from Equation 3 is a method of representing the Jones matrix of the sample. For the spectroscopic ellipsometer, the Jones matrix of the sample is given by

이고, 각각은 p파와 s파의 복소 반사계수이다.At this time,

Are the complex reflection coefficients of the p and s waves.

,

는

와 같이 정의된다. 편광자의 각도가 0, 광탄성 변조기의 각도가 π/4 이며, 검광자의 각도가 π/4 일 때에 광검출기에서 검출되는 빛의 세기는 다음과 같다.In this case, a factor generally used in the analysis of a spectroscopic ellipsometer

,

Is

Is defined as: When the angle of the polarizer is 0, the angle of the photoelastic modulator is π / 4, and the angle of the analyzer is π / 4, the intensity of light detected by the photodetector is as follows.

와

의 정의를 이용하고, 베셀(Bessel) 함수의 성질을 이용하면 다음의 식 12와 같은 결과를 얻을 수 있다.From here again

Wow

Using the definition of and using the properties of the Bessel function, we can obtain the result as in Equation 12 below.

을 만족시키면, 다음의 식 13을 얻을 수 있다.here

If the following is satisfied, the following equation (13) can be obtained.

와

를 실험적으로 얻을 수 있다.So we take the argument of the elliptic solver

Wow

Can be obtained experimentally.

와

를 얻으면 여기서 간단한 구조를 가진 시료의 경우 직접적인 계산 방법으로, 복잡한 구조를 가진 시료의 경우 수치해석적인 모델링 과정등을 통해서 시료의 광학적 성질을 얻어낼 수 있다.Generally

Wow

In this case, the optical properties of the sample can be obtained by the direct calculation method for the sample with the simple structure and through the numerical modeling process for the sample with the complicated structure.

The measurement principles of the magneto-optical spectrometer and the spectroscopic ellipsometer are briefly discussed. It can be seen here that the two instruments are quite similar in principle or components of the measuring instrument. It is this invention that focuses on this point. Let's look at the features of the present invention for each part.

First of all, the light source used Hamamatsu's type L2175 Xen lamp. At this time, the shape of the Xen-lamp generally has a cylindrical symmetry. However, the lamp housing generally uses only a portion of the light emitted from the lamp by making holes in one side of the rectangular parallelepiped as shown in FIG. Alternatively, spherical mirrors can be installed on the opposite side of the hole to increase the available light intensity.

In the present invention, such a housing was improved to drill additional holes on the side with existing holes so that the light of the light source could be used in two directions. Therefore, it is possible to obtain a "point light source" that emits light in a direction perpendicular to each other in one light source.

If you want to use light in three or four directions, you can do this by drilling additional holes as well.

As shown in FIG. 1, the first irradiation beam of the light emitted from the light source 1 in the perpendicular direction to each other is reflected by the first ellipsoid 2 and passes through the first polarizer 3, followed by the electromagnet 5. It is incident almost perpendicularly to the first sample 4 located therein. The light reflected from the first sample 4 passes through the first photoelastic modulator 6 and the first analyzer 7 and is then reflected by the second ellipsoidal mirror 8 so that the light of the double photodetector 9 It enters into a 1st incident slit.

The second irradiation beam emitted in a direction perpendicular to the first irradiation beam is reflected by the third ellipsoid 11 to pass through the second polarizer 12 and the second photoelastic modulator 13 to have a predetermined inclination angle. Incident on the second sample 14. The light reflected from the second sample 14 passes through the second analyzer 15 and is reflected by the fourth ellipsoidal mirror 15 to enter the second incident slit of the dual photodetector 9.

The double photodetecting means 9 used at this time is a product of Oriel Corporation (model number 77200), and its detailed internal structure is as shown in FIG.

It should be noted that an enlarged view of FIG. 3, that is, a portion indicated by reference numeral A is used.

The dual light detection means 9 has two incidence slits 21 and 22, the angle of which can be adjusted so that the plane mirror 23 in the double light detection means 9 is selected so that the light coming from one of the two slits is selected. Means are provided. Thus, by adjusting the planar mirror 23, only one of the light coming in from both directions is selected so that the path setting means in the double photodetector 9, i.e., the first spherical mirror 24, the first grating 25, Monochromatic spectroscopy was performed by sequentially passing through the two spherical mirror 26, the second flat mirror 27, the third flat mirror 28, the third spherical mirror 29, the second grating 30, and the fourth spherical mirror 31. After that, the light may be incident on the optical measuring means 10 attached to the output slit 32. Therefore, the positioning of the incident slit of the light source 1 and the dual light detection means 9 is very important.

The incident light is converted into a current proportional to the intensity of the light in a light multiplier (not shown) in the light detecting means 10 and input to a light measuring part that can be used jointly by the two devices. Thus, it can be adjusted by adjusting the planar mirror 23 in the dual photodetector 9 only when used as a magneto-optical beaker spectrometer and when used as a spectroscopic ellipsometer.

The optical measuring means 10 may be used by two devices in common. Although the inside of the optical measuring means 10 is not shown, an optical amplifier, a preamplifier of the optical amplifier, a lock-in amp 2 And a computer. The common use of these parts can maximize the utilization not only in terms of manufacturing cost but also in the analysis and interpretation of the measured signals.

According to the present invention, it is possible to study the magneto-optical effect that must be used independently of each other, the magneto-optical beaker spectroscopy and the spectroscopic ellipsometer using one device. By combining the two instruments, you can reduce manufacturing costs and maximize the ease of analysis and interpretation of the measured data.

Therefore, the present invention has an effect that the non-diagonal component of the dielectric constant tensor, which is most important in the study of the magneto-optical effect, can be easily obtained.

Claims (5)

A light source for generating a beam irradiating the first sample and the second sample; Magneto-optical means for causing the beam irradiated by the light source to be elliptically polarized by the magneto-optical effect of the first sample placed in the magnetic field to be input to the later double photodetecting means; Spectroscopic elliptic analysis means for causing the beam irradiated from the light source to change its polarization state by the optical property of the second sample and input the dual light detection means; Dual photodetecting means for selectively receiving the light input from the magneto-optical means and the spectroscopic elliptic analysis means and outputting the light to the optical measuring means; And an optical measuring means for performing a magneto-optical spectroscopic function for selectively measuring a large rotation angle and an ellipticity using light input from the dual photodetector or a spectroscopic elliptic analysis function for measuring a complex refractive index. Magneto-optical spectroscopy characterized in that. The magneto-optic and ellipscopy spectrometer according to claim 1, wherein the light source generates an irradiation beam in two different directions so that the beam is irradiated to the first sample and the second sample placed in different directions. The light emitting device of claim 1, wherein the magneto-optical means comprises: a first ellipsoidal mirror placed at a predetermined position in a predetermined shape such that the irradiation beam generated from the light source is incident on the first sample perpendicularly, and increasing the intensity of the incident light; A first polarizer for polarizing the beam passing through the first ellipsoid; An electromagnet for generating a magnetic field such that the irradiation beam passing through the first polarizer is elliptically polarized by a magneto-optical effect when it is incident and reflected perpendicularly to the first sample; A first detector that modulates a phase of light that is sequentially placed in a path in which an elliptical polarized irradiation beam is incident to the dual photodetector, and a light that passes through the first photodetector to an incident slit of the dual photodetector A magneto-optic and ellipscopy spectrometer comprising two ellipsoidal mirrors. 2. The apparatus of claim 1, wherein the spectroscopic elliptic analysis means comprises: a second polarizer generated by the light source and linearly polarizing the irradiation beam through a third ellipsoid mirror; A second photoelastic modulator placed to modulate the phase of the light before the linearly polarized irradiation beam is incident on the second sample at a predetermined inclination angle; A second component for detecting the component projected in the direction of the optical axis from the light in the polarization state in which the radiation beam whose polarization state is changed and reflected by the optical property of the second sample is sequentially placed on the path incident to the dual light detection means; And a fourth ellipsoid reflecting light passing through the analyzer and the second analyzer to the incident slit of the double photodetector. The method of claim 1, wherein the dual light detection means has two incidence slits for inputting beams from the magneto-optical means and the spectroscopic elliptic analytical means, wherein the irradiation beam is selectively directed to any one of the two incidence slits. A planar mirror to be incident; Angle adjusting means for adjusting an angle of the plane mirror; And a path setting means for setting a path such that the beam reflected from the planar mirror is inputted to the optical measuring means through the slit.

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