JPH0378944B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron spin resonance apparatus, and more particularly to an electron spin resonance apparatus in which an electromagnetic horn is used instead of a cavity resonator to apply microwaves to a sample.

Generally, in an electron spin resonance apparatus, a sample is inserted into a cavity resonator to perform measurements. Although this method has the great feature of high measurement sensitivity, (a) there are limitations on the shape and size of the sample due to the fact that the sample is placed inside the cavity (conventional equipment has a maximum of 10 mm);
(b) Due to the resonance condition, the frequency of the microwave applied to the sample cannot be arbitrarily selected.

In order to eliminate this drawback, an electron spin resonance apparatus having the basic configuration shown in FIG. 1 without using a cavity resonator has been proposed in Japanese Patent Application No. 57-215075 (Japanese Patent Application Laid-open No. 59-105551). In the figure, numerals 1 and 2 are electromagnetic horns placed opposite each other. Microwaves generated by a microwave oscillator (not shown) and guided through a waveguide are radiated from an electromagnetic horn 1 toward an electromagnetic horn 2. A test sample 3 such as a sample tube containing a sample or a wafer-shaped sample is placed between these two electromagnetic horns, and a DC magnetic field is applied, for example, in the direction indicated by the arrow in the figure. When a sample absorbs microwaves by electron spin resonance,
Since the microwave power incident on the electromagnetic horn 2 changes, the electron spin resonance of the sample can be detected based on the change.

According to this device, since the sample only needs to be placed in a relatively large space between the two horns, electron spin resonance measurements can be performed on samples of any shape and size, such as semiconductor wafers, amorphous silicon wafers, etc. This method has the great effect of being able to measure even large wafers such as bubble memory wafers without destroying them. Furthermore, since there is no resonator, it is possible to arbitrarily select the microwave frequency.

By the way, in this device, the electromagnetic horn 1
Almost all of the microwaves emitted from the sample and applied to the sample are received by the electromagnetic horn 2.
The detection diode used as a receiver has at most
It can only tolerate microwave power of about 10mW.
Therefore, the power of the microwave applied to the sample from the electromagnetic horn 1 has to be set at a low level commensurate with the allowable power, and therefore high-power microwaves are applied to the sample to perform sensitive measurements. It was difficult.

The present invention has been made in view of this point, and by arranging the transmitting and receiving electromagnetic horns in such a manner that the length directions of their respective end faces intersect in the proposed device, high power can be applied to the sample. The purpose of the present invention is to provide an electron spin resonance apparatus that can perform sensitive measurements by applying microwaves. Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 shows the configuration of an embodiment of the present invention, and in the figure, 4 is a magnet. Inside the magnet 4, a transmitting electromagnetic horn 1 and a receiving electromagnetic horn 2 are arranged facing each other, and a sample 3 is inserted between them. Further, a modulation coil 5 for magnetic field modulation is installed inside the magnet 4, and a modulation current having a frequency of, for example, about 100 KHz is supplied from an oscillator 7 via an amplifier 6 to the coil 5.

Microwaves generated from a microwave oscillator 8 such as a gun oscillator are sent to the transmitting electromagnetic horn 1 via an isolator 9 and an attenuator 10. The microwave incident on the receiving electromagnetic horn 2 is sent to the detection diode 11 and detected.
In this embodiment, in order to set the operating point of the detection diode to an appropriate level, microwaves of an appropriate level are extracted from the transmission system by the directional coupler 12.
A directional coupler 13 is used to send the signal to the receiving system. 14 is a phase shifter for adjusting the phase. The detection signal obtained from the diode 11 is sent via an amplifier 15 to a demodulator (for example a phase sensitive detector) 16. A modulation signal from the oscillator 7 is supplied to the demodulator 16 via a phase shifter 17, and the detection signal is demodulated based on the modulation signal. The demodulated detection signal is sent to a recorder 19 such as a recorder via an amplifier 18, and is recorded in relation to the magnetic field sweep by the excitation power source 20 that excites the magnet 4.

In the configuration as described above, the transmitting electromagnetic horn 1
It is assumed that the receiving electromagnetic horns 2 are the same fan-shaped H-plane horn. In this H-plane horn, the H-plane (the plane parallel to the magnetic field, in other words, the wide side of the rectangular waveguide) of the connected rectangular waveguide is widened, and the E-plane (the plane parallel to the electric field) is widened. , in other words, the narrower side of the rectangular waveguide) remains unchanged. As can be seen from the perspective view in Fig. 3, the two horns are substantially orthogonal, in other words, they are arranged facing each other so that their H planes are orthogonal to each other (which means that their E planes are also perpendicular to each other). There is.

Microwaves transmitted in a rectangular waveguide are
The horn 1 efficiently radiates a fan-shaped beam with sharp directivity into the free space where the sample exists, toward the horn 2, with almost no reflected waves. The plane of the fan is perpendicular to the H plane. At this time, in the proposed device (Fig. 1) in which the horn 2 is arranged to face the horn 1 so that the H plane and the E plane face each other, the directivity of the two horns is the same, and the radiation from the horn 1 is The microwave beam that has passed through the sample portion is efficiently received by the horn 2 with almost no reflected waves according to the reciprocity theorem, resulting in the above-mentioned inconvenience.

In this regard, in the present invention, the receiving horn 2 is arranged approximately 90 degrees rotated with respect to the horn 1, and since the directivity of the horn 2 does not match the direction of the beam emitted from the horn 1, In a state where electron spin resonance is not occurring, in which microwaves that are not affected in any way arrive at the horn 2, the microwaves are hardly received. However, when the magnetic field strength reaches a value that satisfies the resonance condition due to the sweeping by the power supply 20, the microwave magnetic field is activated in the microwave irradiation direction (x) in the plane perpendicular to the static magnetic field and in the direction (y) perpendicular to it. Vibration magnetization Mx,
My is induced in the sample, and the horn 2, which is arranged so that the H plane and the E plane intersect with the horn 1, can receive the microwave power of the My component.

In this way, in the present invention, unlike the proposed device, all the microwaves emitted from the horn 1 do not constantly enter the receiving horn, so the intensity of the microwaves applied to the sample from the horn 1 is increased. However, the receiving diode will not be destroyed even if the receiving diode is damaged, so it is possible to dramatically increase the measurement sensitivity.

In the above-described embodiment, a fan-shaped H-plane electromagnetic horn was used as the transmitting and receiving horn, but an electromagnetic horn on the fan-shaped E-plane may also be used as the transmitting-receiving horn. It goes without saying that you may also use .

Further, the transmitting and receiving horns do not necessarily have to be orthogonal, and the crossing angle may be set as appropriate.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the proposed device, Fig. 2 is a diagram showing the configuration of an embodiment of the present invention, and Fig. 3 is a perspective view for explaining the arrangement of the transmitting and receiving horns in Fig. 2. . 1: Electromagnetic horn for transmission, 2: Electromagnetic horn for reception, 3: Sample, 4: Magnet, 8: Microwave oscillator, 11: Detection diode.

Claims (1)

[Claims] 1. A means for generating a magnetic field to be applied to a sample, a means for generating microwaves to be applied to the sample, a transmitting fan-shaped or pyramid-shaped electromagnetic horn for emitting the microwaves toward the sample, and a means for sandwiching the sample. and a receiving fan-shaped or pyramidal electromagnetic horn arranged opposite to the transmitting electromagnetic horn, and the transmitting and receiving electromagnetic horns are arranged oppositely so that their respective H planes and E planes intersect with each other. An electron spin resonance device characterized by: