JP2020034434A - Electron spin resonance measuring apparatus and method - Google Patents

Abstract

To determine a sufficient measurement condition for each measuring method, when an electron spin resonance (ESR) is measured by a plurality of measuring methods.SOLUTION: In a sweep process of a static magnetic field, for each cycle of a reference signal 90, an EDMR measurement is executed in a first half section, and an ESR measurement (lateral magnetization measurement) is executed in a second half section. In order to perform these measurements, a microwave processor 100 modulates the intensity of the microwave in the first half section, and suppresses the intensity of the microwave in the second half section. In the second half section, a magnetic field modulation is performed. An EDMR spectrum 138 is generated on the basis of an EDMR detection signal. An ESR spectrum 124 is generated on the basis of a reflection wave signal from a cavity 72.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an electron spin resonance (Electron Spin Resonance: hereinafter also referred to as “ESR”) measuring apparatus, and particularly to an apparatus capable of measuring electron spin resonance by a plurality of measuring methods.

  Generally, in electron spin resonance spectroscopy, a sample is placed in a cavity placed in a static magnetic field. In the cavity, electromagnetic energy is applied to electron spins in the sample. When the electromagnetic wave energy (hν) matches the Zeeman energy (gμBo) due to the static magnetic field (Bo), the electromagnetic wave energy is absorbed in the sample, and the phenomenon is observed as electron spin resonance. Here, h is Planck's constant, v is the frequency of the electromagnetic wave, g is the g value, and μ is the magnetic moment of the electron.

  In the ESR measurement apparatus, when the direction of the static magnetic field is the z-axis, the electron spin in the sample has a magnetization (Mz) parallel to the z-axis direction. In this state, the microwave is supplied and the static magnetic field is swept (specifically, the intensity of the static magnetic field is changed). In the process, when the resonance condition is satisfied, a vibration magnetization (transverse magnetization) component (My) in the y-axis direction is generated. A general “ESR spectrum” (CW-ESR spectrum) observed in an ESR measuring apparatus is a plot of a change in a vibration magnetization component (My) with respect to a change in the strength of a static magnetic field.

  Several methods for observing electron spin resonance as a measurement signal different from the above have been proposed (see Patent Document 1). In the EDMR (Electrically Detected Magnetic Resonance) measurement method, a current flowing through a sample is observed. When electron spin resonance occurs in a sample, a change occurs in the current flowing through the sample. In the EDMR measurement, such a change in current is detected. In the ODMR (Optically Detected Magnetic Resonance) measurement method, light emitted from a sample is detected. When electron spin resonance occurs in a sample, a change occurs in the amount of light emitted from the sample. In the ODMR measurement method, such a change in light amount is detected. In LOD (Longitudinally detected) -ESR measurement method (also referred to simply as “LOD measurement method”), longitudinal magnetization in a sample is detected. The longitudinal magnetization is a magnetization component (Mz) in the z-axis direction, and is different from the above-described vibration magnetization component (My) in the y-axis direction.

JP-A-2006-75665

  If electron spin resonance can be measured simultaneously by a plurality of measurement methods, valuable information for analyzing the physical properties of a sample can be obtained. However, the conventional ESR measuring apparatus cannot basically measure electron spin resonance simultaneously by a plurality of measuring methods. Even if electron spin resonance is simultaneously measured by a plurality of measurement methods using a conventional ESR measurement device, if the measurement conditions such as microwave intensity and modulation frequency are common among the plurality of measurement methods, For example, all of the measurement results cannot be made good.

  An object of the present invention is to measure electron spin resonance using a plurality of measurement methods and under measurement conditions suitable for each measurement method.

  An electron spin resonance measurement apparatus according to an embodiment includes a magnetic field generator that generates a static magnetic field, a member that is disposed in the static magnetic field, and that receives a sample, in which microwaves are supplied, and the sample generates electron spin resonance. And a measuring means for cyclically executing a plurality of measurement methods for measuring the electron spin resonance in the process of sweeping the static magnetic field.

  According to the above configuration, a plurality of measurement methods are cyclically executed in the process of sweeping the static magnetic field. Since a plurality of measurement methods are executed in a time-sharing manner, it is possible to set measurement conditions suitable for each measurement method when each measurement method is executed. In addition, since a plurality of measurement methods can be executed in parallel, synchronism can be ensured when matching a plurality of measurement results. In order to smoothly perform the cyclical execution of the plurality of measurement methods, in particular, to periodically control the microwave, a composite signal described later is used in the embodiment.

  Preferably, the plurality of measurement methods for measuring electron spin resonance include a measurement method for observing a reflected wave from a cavity and a measurement method for observing a measurement signal from a sample that is different from the reflected wave. Method. Three or more measurement methods may be performed cyclically. In general, a plurality of measurement methods are cyclically executed in a cycle considerably earlier than the sweep period of the static magnetic field. The measuring unit corresponds to a configuration around the cavity except for the cavity and the static magnetic field generator, and specifically, is configured by circuits, elements, and the like necessary to execute a plurality of measuring methods. .

  In an embodiment, the plurality of measurement methods include a first measurement method and a second measurement method, wherein the microwave supplied to the cavity is modulated in the first measurement method, and the static electricity is modulated in the second measurement method. The magnetic field is modulated. In each of the first measurement method and the second measurement method, a microwave (electromagnetic wave) is supplied to the cavity. At least the first measurement method modulates the microwave, and at least the second measurement method modulates the static magnetic field. In the embodiment, the modulation method is dynamically switched for each measurement method.

  In an embodiment, the modulation frequency of the microwave is lower than the modulation frequency of the static magnetic field. In the embodiment, the intensity of the microwave supplied to the cavity in the first measurement method is higher than the intensity of the microwave supplied to the cavity in the second measurement method. As described above, in the embodiment, the modulation frequency and the microwave intensity are switched for each measurement method.

  In an embodiment, the measuring means includes: a composite signal generation circuit that generates a composite signal including an amplitude modulation signal corresponding to the first measurement method and a DC signal corresponding to the second measurement method; A microwave that modulates a microwave supplied to the cavity according to the amplitude modulation signal when performing a method, and sets an intensity of the microwave supplied to the cavity according to a level of the DC signal when performing the second measurement method; A magnetic field modulation signal generation circuit that generates a magnetic field modulation signal when the second measurement method is executed and supplies the magnetic field modulation signal to the magnetic field modulation coil.

  The composite signal functions as a signal for amplitude-modulating the microwave when the first measurement method is executed, and functions as a signal for setting a constant microwave intensity when the second measurement method is executed. The microwave processing circuit to which the composite signal is supplied is a circuit that dynamically controls the amplitude of the microwave, and functions as a microwave modulator and a microwave intensity adjuster.

  In the embodiment, further, when the first measurement method is performed, a first detection circuit that detects a measurement signal obtained from the sample according to a fundamental frequency of the composite signal; A second detection circuit for detecting a reflected wave signal from the cavity in accordance with a magnetic field modulation frequency of the magnetic field modulation signal during execution. The fundamental frequency of the composite signal determines each execution period of the first measurement method and the second measurement method. In an embodiment, the measurement signal is at least one of a measurement signal obtained by an EDMR measurement method, a measurement signal obtained by an ODMR measurement method, and a measurement signal obtained by a LOD measurement method. Other measurement methods may be employed.

  An electron spin resonance measurement method according to an embodiment includes a step of disposing a sample in a cavity provided in a static magnetic field, a step of generating an amplitude modulation signal corresponding to the first measurement method, and a method of generating an amplitude modulation signal corresponding to the second measurement method. Generating a setting signal; modulating a microwave supplied to the cavity in accordance with the amplitude modulation signal when performing the first measurement method; and controlling the cavity in accordance with the amplitude setting signal when performing the second measurement method. And setting the intensity of the microwave supplied to the static magnetic field and modulating the static magnetic field at a higher frequency than the frequency of the amplitude modulation signal.

  According to the above configuration, electron spin resonance generated in the sample is measured by a plurality of measurement methods. At that time, in the first measuring method, the microwave is amplitude-modulated, and in the second measuring method, the static magnetic field is modulated while controlling (for example, suppressing) the intensity of the microwave. Preferably, the first measurement method and the second measurement method are cyclically executed in a short cycle in the process of sweeping the static magnetic field.

  According to the present invention, electron spin resonance can be measured by a plurality of measurement methods and under measurement conditions suitable for each measurement method.

It is a figure showing the 1st example of reference of an ESR measuring device. It is a figure showing the 2nd example of reference of an ESR measuring device. It is a figure showing the 3rd example of an ESR measurement device. It is a figure showing the 4th example of an ESR measuring device. It is a figure showing the 5th example of an ESR measuring device. It is a figure showing a 6th example of an ESR measuring device. It is a figure showing the electron spin resonance measuring device concerning a 1st embodiment. FIG. 3 is a diagram illustrating a reference signal, a composite signal, and a magnetic field modulation signal. It is a figure showing a measurement result concerning a comparative example. FIG. 5 is a diagram showing a measurement result according to the first embodiment. It is a figure showing the ESR measuring device concerning a 2nd embodiment. It is a figure showing the ESR measuring device concerning a 3rd embodiment.

  First, some reference examples will be described, problems occurring there will be organized, and then some embodiments will be described.

(1) Description of Reference Example FIG. 1 shows an outline of a general ESR measurement apparatus as a first reference example. The illustrated ESR measuring device is a device for measuring electron spin resonance according to the CW method.

  The sample 10 to be measured is arranged in the cavity 12. Microwave is supplied to the cavity 12. The cavity 12 is a cavity and acts as a resonator for microwaves. Note that the sample 10 is a gas, a liquid, or a solid.

The static magnetic field generator 14 includes a pair of electromagnet coils and the like that generate a static magnetic field (B ₀ ). The static magnetic field is a magnetic field parallel to the z-axis direction at least around the sample 10. The intensity of the static magnetic field is swept to produce electron spin resonance. The sweep is repeated as needed. In the illustrated configuration example, a magnetic field modulation coil 16 is arranged between the static magnetic field generator 14 and the sample 10. The magnetic field modulation coil 16 generates a modulation magnetic field (oscillating magnetic field) that modulates the static magnetic field by superimposing the static magnetic field on the static magnetic field. The magnetic field modulation coil 16 is provided with the magnetic field modulation signal generated by the magnetic field modulation signal generator 24. The microwave generator 18 generates a microwave. The attenuator 20 is a circuit that adjusts the power, that is, the intensity of the generated microwave. The microwave that has passed through the attenuator is introduced into the cavity 12 via the circulator 22.

  In the sweeping process of the static magnetic field, when certain resonance conditions are satisfied, the electron spins in the sample interact with the microwaves to be in a resonance state. At this time, the tuning balance of the cavity 12 is lost, and a reflected wave oscillating at the modulation frequency leaks out of the cavity 12. The reflected wave leaking from the cavity 12 passes through the circulator 22 and is sent to the microwave detector 26, where it is detected by mixing the microwaves. As a result, a signal in the audio frequency band is generated. The phase shifter 28 shifts the phase of the microwave. After the signal after detection is amplified by the amplifier 30, the signal is input to a phase detector 32 configured as, for example, a lock-in amplifier, where the signal is subjected to phase detection. In the phase detector 32, the reference signal generated by the magnetic field modulation signal generator 24 is mixed with the signal output from the amplifier 30. Thereby, a DC signal is generated as a signal after detection. The DC signal is converted into a digital signal in an A / D converter 34, and the converted digital signal is input to an information processing device 36 such as a PC. In the information processing device 36, an ESR spectrum is generated. This ESR spectrum represents the y-axis component (transverse magnetization) of the magnetization due to the electron spin as described above.

  FIG. 2 shows, as a second reference example, a first example of an ESR measuring device according to an EDMR (Electrically Detected Magnetic Resonance) measuring method. In the description of each drawing, the same reference numerals are given to the elements described before, and the description will be omitted.

  In this method, as described below, an EDMR spectrum is observed under the CW method. In the illustrated first example, some components are added to a general ESR measurement device. In the EDMR measurement, the sample 38 is typically a semiconductor device. A voltage is applied to the sample 38 by a power supply 40. The voltage between both ends of the sample 38 is detected by the amplifier 42. When electron spin resonance occurs in the sample during the process of sweeping the static magnetic field, the current flowing through the sample 38 changes. The change in the current is observed in the amplifier 42 as a change in the voltage. The detection signal output from the amplifier 42 is sent to the phase detector 44. By mixing the detection signal with the magnetic field modulation signal (reference signal output from the magnetic field modulation signal generator 24), the detection signal is subjected to phase detection. The signal (DC signal) after the phase detection is converted into a digital signal in the A / D converter 46, and the digital signal is sent to the information processing device 48. The information processing device 48 generates an EDMR spectrum.

  The EDMR spectrum, unlike the ESR spectrum, does not directly reflect the magnetic moment, but reflects a change in the current path (conductivity, current path, etc.) caused by a change in the magnetic moment. At the same time as information, it can be said that it is current information due to electron spin.

  In the configuration shown in FIG. 2, when the EDMR spectrum is observed, the configurations of the microwave detector 26, the amplifier 30, the phase detector 32, the A / D converter 34, the information processing device 36, and the like do not function. Although it is possible to make them work, various problems may arise if the two measurement methods are executed in parallel under the same measurement conditions, as described later.

  FIG. 3 shows a second example of an ESR measuring device according to the EDMR method as a third reference example. In the second embodiment, the magnetic field modulation is applied. In the third embodiment, the amplitude modulation (AM modulation) is applied.

  The microwave generated by the microwave generator 18 is sent to the switch 52 via the attenuator 20. The modulation signal generated by the modulation signal generator 50 is input to the switch 52, and the switch 52 performs an on / off operation according to the modulation signal. Thereby, the microwave whose amplitude has been modulated is supplied to the cavity 12 through the circulator 22. In the cavity 12, a sample 38 made of a semiconductor device or the like is arranged as in the second reference example. In the phase detector 44, a modulation signal (a reference signal output from the modulation signal generator 50) is mixed with the detection signal from the amplifier 42, and thereby a DC signal is generated as a signal after the phase shift detection. . When electron spin resonance occurs in the sample 38 in the process of the magnetic field sweep, the current flowing through the sample 38 changes, and the change is observed as a change in the detection signal. An EDMR spectrum is generated based on the observation result.

  According to the third reference example that complies with the EDMR method, the displacement amount can be larger than that of the second reference example that complies with the EDMR method, so that it is generally possible to measure a broadband EDMR spectrum with high sensitivity. Further, in the magnetic field modulation system, an induced electromotive force is easily generated in a semiconductor device, but in the microwave intensity modulation system, such an induced electromotive force is hardly generated. As a result, there is obtained an advantage that it is easy to avoid saturation of the lock-in amplifier due to an increase in offset.

  FIG. 4 shows, as a fourth reference example, a first example of an ESR measurement apparatus that follows the ODMR (Optically Detected Magnetic Resonance) measurement method. In the EDMR method, the current flowing through the sample 38 is detected, whereas in the ODMR method, the intensity of light emitted from the sample 38 or the intensity of light transmitted through the sample 38 is detected. A power supply 40 is connected to the sample 38. A photodetector 54 is provided near the sample 38, and a detection signal from the photodetector 54 is sent to a phase detector 44 via an amplifier 56. In the phase detector 44, the detection signal is mixed with the magnetic field modulation signal (the reference signal output from the magnetic field modulation signal generator 24), whereby the detection signal is subjected to phase detection. An ODMR spectrum is generated based on the signal after the phase detection. The physical quantity obtained by this method is information on light intensity and light energy (wavelength).

  FIG. 5 shows a second example of the ESR measuring device according to the ODMR method as a fifth reference example. In the fourth embodiment, the magnetic field modulation method is applied, but in the fifth embodiment, the microwave amplitude modulation is applied as in the third embodiment shown in FIG. Since the individual elements shown in FIG. 5 have already been described, the description of the configuration in FIG. 5 will be omitted.

  FIG. 6 shows, as a sixth reference example, an ESR measuring device according to a LOD (Longitudinally Detected) measuring method. In this method, a magnetization component (longitudinal magnetization) in the same direction as the static magnetic field direction is detected from the magnetization caused by the electron spin, and a LOD spectrum (LOD-ESR spectrum) is generated. An LOD coil 58 for detecting longitudinal magnetization is arranged around the sample 10. The LOD coil 58 detects an induced electromotive force due to a change in longitudinal magnetization. The detection signal from the LOD coil 58 is input to the phase detector 44 via the amplifier 60. In the phase detector 44, the detection signal is multiplied by the intensity modulation signal (the reference signal output from the modulation signal generator 50), and the LOD-ESR spectrum is generated based on the result of the multiplication. The sixth reference example also observes a change in a detection signal caused by electron spin resonance occurring in a sample in the process of sweeping a magnetic field.

  The LOD spectrum, like the ESR spectrum, represents information on the magnetic moment of electron spin. However, while the ESR spectrum represents the magnetization component in the y-axis direction perpendicular to the static magnetic field, the LOD spectrum represents the magnetization component in the z-axis direction. This method is used as a method for obtaining T1 information (spin lattice relaxation time) of electron spin.

  Although the EDMR spectrum, ODMR spectrum, and LOD spectrum described above are all spectra due to electron spin resonance, the physical quantities reflected in them are essentially different from the physical quantities represented by the ESR spectrum. ing. Therefore, it is desired to observe other spectra simultaneously with the observation of the ESR spectrum.

  For example, in the analysis of the physical properties of a diode, it is desirable to obtain information on the recombination current depending on the electron spin, and such information is obtained by an EDMR measurement method or an ODMR measurement method. The current flowing through the sample and the light emission generated in the sample are closely related to defective electrons and temporary electron spin pairs existing in the energy level of the semiconductor. In general, a lattice defect generated intentionally or unintentionally exists in a semiconductor device and contains an electron spin as an impurity.

  In ordinary ESR measurement, electron spins related to the function of the device and electron spins unrelated to the function are detected without distinction. According to the EDMR measurement method or the ODMR measurement method, it is possible to selectively measure electron spins related to device operation. From such a background, it is required to measure ESR and other phenomena simultaneously and in parallel, and to measure them under measurement conditions suitable for each measurement method. The embodiment described below meets such a need.

(2) Detailed Description of Embodiment FIG. 7 shows an ESR measurement device according to the first embodiment. This ESR measuring device is a device that simultaneously measures an EDMR spectrum and an ESR spectrum in a time-division manner. In other words, this electron spin resonance measurement apparatus is an apparatus that simultaneously executes the EDMR measurement method as the first measurement method and the ESR measurement method as the second measurement method in parallel under appropriate measurement conditions. .

  Prior to the description of the specific configuration, measurement conditions employed in each measurement method will be described. In the embodiment, in the process of sweeping the static magnetic field, the EDMR measurement method and the ESR measurement method are repeatedly and alternately executed in a short cycle. In the EDMR measurement method, a microwave is modulated while the modulation of a static magnetic field is stopped, and a measurement signal obtained from a sample is phase-detected by a reference signal having the same frequency as the microwave modulation signal. On the other hand, when performing the ESR measurement method, the static magnetic field is modulated in a state where the modulation of the microwave is stopped, and the microwave having a constant intensity (low intensity) is supplied to the cavity. The reflected wave from the cavity is phase-detected by a reference signal having the same frequency as the magnetic field modulation signal.

  Generally, in order to obtain a good SN ratio in the EDMR measurement method, for example, it is required to supply a strong microwave of about 100 to 200 mW to the cavity. In the EDMR spectrum, there is a tendency for the line width to spread, and in order to obtain a sufficient signal intensity, it is necessary to set a large modulation magnetic field intensity. Furthermore, due to the nature of the response characteristics of the device as a sample, the modulation frequency is set, for example, in the vicinity of 1 kHz.

  On the other hand, in the ESR measurement method, when the intensity of the microwave is increased and the intensity of the modulation magnetic field is increased, the ESR spectrum is saturated, and distortion due to overmodulation occurs in the ESR spectrum. The modulation frequency used in the ESR measurement method is, for example, 100 kHz.

  In general, when an EDMR spectrum is measured by a magnetic field modulation method, an induced electromotive force due to a fluctuating magnetic field is generated in a sample as a device, and the frequency of a generated signal is the same as a modulation frequency, so that lock-in detection can be properly performed. The problem that there is not easily occurs. In order to avoid this, it is desired to employ microwave amplitude modulation instead of magnetic field modulation. However, when microwave amplitude modulation is applied in ESR spectrum measurement, detection may be difficult due to the influence of a large offset component in some cases.

  Therefore, it is desired to individually set the microwave intensity, the modulation method, the modulation frequency, and the like for the two measurement methods. In addition, it is desirable to synchronize the two measurement methods and execute them cyclically at appropriate timing. The first embodiment shown in FIG. 7, the second embodiment shown later in FIG. 11, and the third embodiment shown later in FIG. It has a configuration that can be executed under the following conditions. This will be specifically described below.

  In the ESR measuring apparatus according to the first embodiment shown in FIG. 7, the sample 70 is, for example, a semiconductor device. The sample 70 is arranged in a cavity 72 as a resonator. In the vicinity of the sample 70, a uniform static magnetic field is generated by the static magnetic field generator 74. The static magnetic field generator 74 has a function of sweeping the intensity of the static magnetic field to generate electron spin resonance. A magnetic field modulation coil 76 for generating a modulation magnetic field superimposed on the static magnetic field is arranged near the sample 70. It does not work in EDMR measurements, but in ESR spectra measurements. The magnetic field modulation coil 76 is arranged outside the cavity 72 or inside the cavity 72.

  A DC power supply 78 is provided for applying a voltage to the sample 70. By the operation of the switch 80, it is possible to switch whether or not to apply a voltage. When the terminal A is selected, a voltage is applied to the sample 70. For example, the terminal B is selected by the switch 80 when observing a solar cell or when observing the reverse spin Hall effect. A change in current flowing through the sample 70 is detected by the amplifier 82 as a change in voltage. The amplifier 82 outputs an EDMR detection signal 134.

  The ESR measurement device according to the first embodiment includes a first signal generator 84 and a second signal generator 86. The first signal generator 84 is a circuit that generates a composite signal 88 and a reference signal 90. The reference signal 90 also functions as a reference signal when performing phase detection. The composite signal 88 is a signal synchronized with the reference signal 90. The reference signal 90 is a logic signal, which has a first modulation frequency (fmod1) as a fundamental frequency, which is a frequency of several tens to several kHz, for example. The first modulation frequency is a modulation frequency in amplitude modulation of a microwave. Each one cycle of the reference signal 90 includes a first half section (H section, EDMR measurement period) and a second half section (L section, ESR measurement period). In the first half section, EDMR measurement is performed. An ESR measurement is performed. The duty of the reference signal 90 is 50% in the illustrated example. The composite signal 88 has an amplitude modulation signal in the first half section, and has a constant DC signal having a low level in the second half section. The amplitude-modulated signal has a gentle mountain-like form, which is smoothly connected to the subsequent DC signal. The amplitude modulation signal has, for example, a Gaussian distribution form, which does not have a steep rising or a steep falling (that is, a high-frequency component).

  The second signal generator 86 generates a sine wave signal 94 having a second modulation frequency (fmod2) and a logic signal 96. The second modulation frequency is higher than the first modulation frequency, which is, for example, several tens to several hundreds kHz. The duty of the logic signal 96 is 50% in the illustrated example. The second modulation frequency is used as a modulation frequency of the static magnetic field. The switching circuit 106 allows the sine wave signal 94 to pass only in the latter half section of the reference signal 90, that is, in the L section. As a result, a magnetic field modulation signal 108 that functions only in each of the latter half sections is generated. The magnetic field modulation signal 108 is supplied to the magnetic field modulation coil 76 via the amplifier 110. Thereby, the modulation magnetic field is superimposed on the static magnetic field in the latter half section.

  The microwave generated by the microwave generator 98 is input to the microwave processor 100. The microwave processor 100 is a circuit that controls the amplitude of a microwave based on a composite signal. Specifically, in the first half section, the microwave is amplitude-modulated according to the amplitude modulation signal. In the latter half section, the intensity of the microwave is suppressed to be constant according to the DC signal. The microwave that has undergone such processing is supplied to the cavity 72 via the amplifier 102 and the circulator 104.

  If a magnetic field that satisfies the ESR resonance conditions is generated during the sweep of the static magnetic field, the microwaves interact with the electron spins contained in the sample, and the tuning in the cavity 72 is disrupted, so that a reflected wave from the cavity 72 is generated. . In that case, a reflected wave signal modulated by the microwave modulation frequency is obtained in each first half section, and a reflected wave signal modulated by the magnetic field modulation frequency is obtained in each second half section.

  When the switch 128 is off and the switch 114 selects the terminal A, the reflected wave signal from the cavity 72 is input to the microwave detector 112 via the circulator 104. The microwave detector 112 converts the reflected wave signal into a signal in the audio frequency band. The converted signal is input to the lock-in amplifier 120 via the amplifier 116 as the detection signal 118. The lock-in amplifier 120 is a circuit that performs phase detection of the detection signal 118 based on the logic signal 96 having the magnetic field modulation frequency. In the lock-in amplifier 120, the reflected wave signal component having the microwave modulation frequency is rejected, and the reflected wave signal component having the magnetic field modulation frequency is extracted. The DC signal output from the lock-in amplifier 120 is input to the information processing device 122. The information processing device 122 generates the ESR spectrum 124 by plotting the level of the DC signal in the process of sweeping the static magnetic field.

  On the other hand, when the switch 128 is on and the switch 114 selects the terminal B, the reflected wave signal from the circulator 104 is input to the demodulator 130. Demodulator 130 is a detector or a mixer. In the demodulator 130, the reflected wave signal is mixed with the microwave, whereby the reflected wave signal is detected and converted into an audio signal. Reference numeral 126 denotes a phase shifter. When such a circuit configuration is used, the phase of the microwave can be easily adjusted, and an AFC (Automatic Frequency Control) function can be used. In the configuration illustrated in FIG. 7, the microwave detector 112 and the demodulator 130 are provided in parallel, but only one of them may be provided.

  On the other hand, when a magnetic field that satisfies the ESR resonance condition is generated during the sweep of the static magnetic field, the microwave interacts with the electron spin related to the current in the sample 70, and the bias current and the induced current change in the sample 70. . That is, the current flowing through the sample changes. The change in the current is detected by the amplifier 82, and a detection signal 134 is output from the amplifier 82. The detection signal 134 becomes a signal modulated by the microwave modulation frequency in each first half section, and becomes a signal modulated by the magnetic field modulation frequency in each second half section. The detection signal 134 is input to the lock-in amplifier 132. In the lock-in amplifier 132, the detection signal 134 is phase-detected by the reference signal 90 having the microwave modulation frequency. That is, a detection signal component having a microwave modulation frequency is extracted in each first half section. On the other hand, in each latter half section, the detection signal component having the magnetic field modulation frequency is rejected. The DC signal output from the lock-in amplifier 132 is input to the information processing device 136. The information processing device 136 generates the EDMR spectrum 138 by plotting the level of the changing DC signal in the process of sweeping the static magnetic field.

  The control unit 139 controls the operation of each component shown in FIG. 7, and is configured by, for example, an information processing device. The control unit 139 may execute synthesis, matching, analysis, and the like of the ESR spectrum 124 and the EDMR spectrum 138. The information processing devices 122 and 136 and the control unit 139 may be configured by a single computer.

  In the timing chart shown in FIG. 8, (A) shows a reference signal 90. (B) shows the composite signal 88. (C) shows the magnetic field modulation signal 108. The frequency of the reference signal 90 is a microwave modulation frequency. As described above, each cycle 200 of the reference signal 90 includes a first half section 200A for EDMR measurement and a second half section 200B for ESR measurement. The composite signal 88 has a mountain-like waveform in the first half section 200A, which constitutes a microwave amplitude modulation signal 88A, and is a flat signal in the second half section 200B, which constitutes a DC signal 88B for microwave intensity setting. I do. The level (offset) 202 of the DC signal 88B can be set arbitrarily. In the magnetic field modulation signal 108, the first half section 200A is a no-signal section 204, and a burst 108A having a magnetic field modulation frequency occurs in the second half section 200B. Reference numeral 206 indicates one cycle of the magnetic field modulation frequency.

  In the above description, the EDMR measurement is performed in the first half section and the ESR measurement is performed in the second half section, but they may be reversed. Also, a third measurement may be added and the three measurement methods may be performed cyclically. In that case, a circuit for the third measurement is added.

  If a rectangular pulse is used as the pulse for amplitude modulation, many high-frequency components are included in the detection signal, lock-in detection cannot be performed properly, and non-negligible beat noise may be superimposed on the EDMR spectrum. There is. On the other hand, if a pulse having a gentle shape as described above is used as the pulse for amplitude modulation as in the above-described embodiment, the occurrence of the above problem can be avoided or reduced. Instead of the mountain-shaped pulse, a pulse having another form having no sharp change may be used. In addition, the intensity of the microwave can be adjusted during the ESR measurement period by the DC signal 88B, and more specifically, the intensity can be reduced, so that the problem of saturation of the ESR spectrum can be avoided or reduced.

  According to the first embodiment, in the sweeping process of the static magnetic field, the EDMR measurement and the ESR measurement can be alternately and repeatedly performed in a short cycle. In the EDMR measurement, the intensity of the microwave is increased, the amplitude modulation of the microwave is applied, and a low frequency is set as the frequency. On the other hand, in the ESR measurement, the intensity of the microwave is reduced and the magnetic field is modulated. A high frequency is set as the frequency. As described above, it is possible to apply measurement conditions suitable for each measurement method. Therefore, it is possible to optimize both the EDMR measurement and the ESR measurement. Since the two measurement methods are executed substantially simultaneously in parallel, it is also possible to ensure the synchronization of the measurements. That is, it is possible to simultaneously observe a phenomenon occurring at a specific timing in a sample by using a plurality of measurement methods.

  FIG. 9 shows an EDMR spectrum 210 and an ESR spectrum 212 according to the comparative example. The spectra 210 and 212 are obtained by performing the EDMR measurement and the ESR measurement simultaneously under the same measurement conditions by the configuration shown in FIG. Focusing on the vicinity of 336 mT in the ESR spectrum 212, saturation occurs due to excessive microwave power, that is, the waveform is broken. In the tablet signals on both sides, the line width is widened due to excessive magnetic field modulation. On the other hand, FIG. 10 shows an EDMR spectrum 214 and an ESR spectrum 216 according to the first embodiment. Focusing on the vicinity of 336 mT in the ESR spectrum 216, a normal waveform is obtained because the microwave power is appropriate. Normal waveforms are also obtained from the tablet signals on both sides by appropriate magnetic field modulation. In the EDMR spectrum 214, a strong signal is obtained by low frequency modulation and high power irradiation. As is clear from the comparison between FIGS. 9 and 10, according to the first embodiment, a good EDMR spectrum 214 and a good ESR spectrum 216 can be obtained.

  In the configuration shown in FIG. 7, the lock-in amplifier 120 keeps outputting no signal in each first half section (ESR measurement section), and the average value of the detected signal is reduced by half. In order to avoid this, in the lock-in amplifier 120, a plurality of DC signals obtained separately in a plurality of later sections may be connected, and the connected DC signals may be sent to the information processing device 122.

  FIG. 11 shows an ESR measurement device according to the second embodiment. The same components as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

  In the ESR measurement device according to the second embodiment, the ODMR measurement and the ESR measurement are performed simultaneously. A photodetector 140 is provided near the sample 70, from which a detection signal is output. The detection signal is a signal modulated by the microwave amplitude modulation frequency. The signal is input to the lock-in amplifier 132 via the amplifier 142 as the detection signal 144. In the second embodiment, the ODMR measurement is performed in each first half period, and the ESR measurement is performed in each second half period.

  FIG. 12 shows an ESR measurement device according to the third embodiment. The same components as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

  In the ESR measurement device according to the third embodiment, the LOD measurement and the ESR measurement are performed simultaneously. An LOD detection coil 148 is provided outside or inside the cavity 72, and a detection signal indicating a change in longitudinal magnetization is sent to the lock-in amplifier 132 via the amplifier 150. In the third embodiment, LOD measurement is performed in each first half period, and ESR measurement is performed in each second half period.

  According to each of the above embodiments, electron spin resonance can be measured by cyclic execution of a plurality of measurement methods, and in particular, it is possible to optimize measurement conditions when executing each measurement method.

  70 samples, 72 cavities, 74 static magnetic field generator, 76 magnetic field modulation coil, 84 first signal generator, 86 second signal generator, 98 microwave generator, 100 microwave processor, 106 switch, 120 lock-in amplifier , 132 Lock-in amplifier.

Claims (8)

A static magnetic field generator for generating a static magnetic field,
A member that is arranged in the static magnetic field and accommodates a sample, wherein a microwave is supplied, and a cavity that causes electron spin resonance in the sample;
Measuring means for cyclically executing a plurality of measuring methods for measuring the electron spin resonance in the process of sweeping the static magnetic field,
An electron spin resonance measurement device comprising: The electron spin resonance measuring apparatus according to claim 1,
The plurality of measurement methods include a first measurement method and a second measurement method,
In the first measuring method, the microwave supplied to the cavity is modulated,
In the second measuring method, the static magnetic field is modulated,
An electron spin resonance measuring apparatus, comprising: The electron spin resonance measuring apparatus according to claim 2,
The modulation frequency of the microwave is lower than the modulation frequency of the static magnetic field,
An electron spin resonance measuring apparatus, comprising: The electron spin resonance measuring apparatus according to claim 3,
The intensity of the microwave supplied to the cavity in the first measurement method is higher than the intensity of the microwave supplied to the cavity in the second measurement method,
An electron spin resonance measuring apparatus, comprising: The electron spin resonance measuring apparatus according to claim 2,
The measuring means comprises:
A composite signal generation circuit that generates a composite signal including an amplitude modulation signal corresponding to the first measurement method and a DC signal corresponding to the second measurement method;
Modulating the microwave supplied to the cavity according to the amplitude modulation signal during the execution of the first measurement method, and modulating the intensity of the microwave supplied to the cavity according to the level of the DC signal during the execution of the second measurement method; A microwave processing circuit to be set;
A magnetic field modulation signal generation circuit that generates a magnetic field modulation signal during the execution of the second measurement method and supplies the magnetic field modulation signal to the magnetic field modulation coil;
An electron spin resonance measurement device comprising: The electron spin resonance measuring apparatus according to claim 5,
A first detection circuit that detects a measurement signal obtained from the sample according to a fundamental frequency of the composite signal when the first measurement method is executed;
A second detection circuit that performs detection on a reflected wave signal from the cavity according to a magnetic field modulation frequency of the magnetic field modulation signal when the second measurement method is performed;
An electron spin resonance measurement device comprising: The electron spin resonance measuring apparatus according to claim 6,
The measurement signal is at least one of a measurement signal obtained by the EDMR measurement method, a measurement signal obtained by the ODMR measurement method, and a measurement signal obtained by the LOD measurement method.
An electron spin resonance measuring apparatus, comprising: Placing the sample in a cavity placed in a static magnetic field,
Generating an amplitude modulation signal corresponding to the first measurement method and generating an amplitude setting signal corresponding to the second measurement method;
Modulating the microwave supplied to the cavity according to the amplitude modulation signal when performing the first measurement method;
Setting the intensity of the microwave supplied to the cavity according to the amplitude setting signal during the execution of the second measurement method, and modulating the static magnetic field at a frequency higher than the frequency of the amplitude modulation signal;
A method for measuring electron spin resonance, comprising: