JPS6059538B2 - Emission spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emission spectrometer, and more particularly to an emission spectrometer suitable for analyzing minute parts on a solid surface.

Energy dispersive type S (EPMA) uses X-rays, electron beams, ion beams, etc. to analyze minute parts or surface layers of solids.
There are physical analysis methods such as EM9AES, ESCA, and Irv1A.

Although these methods are capable of detecting minute surfaces in a high range, each method has a large influence on the analysis results due to measurement parameters. Furthermore, in order to determine the absolute value of the surface composition, calibration using the same standard sample is necessary, but at present it is almost impossible to obtain these standard samples.
On the other hand, unlike the above methods, the laser micro-emission spectrometer uses synchrotron radiation from a plasma cloud generated by irradiating a sample surface with a laser, or radiation from arc discharge or spark discharge between closely spaced graphite electrodes. There is a way to directly measure light. However, when graphite electrodes are used, there are disadvantages such as contamination of the sample with graphite and expansion of the excitation-emission sample region.Furthermore, regardless of the presence or absence of graphite electrodes, the plasma temperature is low, resulting in a low energy level of the generated atomic vapor. This method has the drawbacks of a mixture of ion states and high energy level ionic states, significant influence of the matrix, and poor reproducibility. When microwave energy is used to excite sample vapor generated by a laser beam instead of the arc discharge or spark discharge described above, a waveguide is used to supply high power of 100 W or more.

If it is approximately 100W or less, it can be transmitted through a coaxial cable without being affected by insulation breakdown. Waveguides are more suitable for supplying microwave energy stably, efficiently, and in the range of 0 to 200 W, but 2
In the frequency band of ~4 GHz, the width of the aperture is several 1
〜The shape is the number of rivers I. Moreover, both the oscillating side and the receiving side must be tuned separately, and if a conventional EH tuner or non-reflection terminator was installed on the oscillating side and the receiving side, it would be large.
It's also difficult to get along. In particular, when the receiving side passes through a waveguide,
- It is difficult to achieve synchronization within the channel because the gas load is small. Further, even if the synchronization was achieved, the load would change if the temperature inside the torch or its surroundings changed, so further fine adjustment was required. In other words, with conventional methods, it has been difficult to efficiently supply and absorb energy. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an optical emission spectrometer capable of analyzing minute portions on a solid surface with high sensitivity and precision.

In order to achieve the above object, in the present invention, the vapor of the sample generated by laser beam irradiation is sent to the waveguide section by an air supply gas, and here the vapor is generated by microwave energy. The method is configured to generate a flame and perform spectroscopic analysis of synchrotron radiation emitted from the plasma flame, and a movable short-circuit plate is provided in the waveguide to improve the efficiency of turning vapor into plasma using microwave energy. It is characterized by the fact that

The present invention will be explained in detail below.

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, a laser power source 1 irradiates a laser beam 3 from a laser oscillator 2 onto the surface of a sample 6 on a sample stage 7 via a condensing system 4. At this time, the laser beam 3 passes through the cap 8, and the sample 6 is placed inside the cap. The sample 6 absorbs the energy of the laser beam 3, generates Joule heat, and generates vapor of its constituent components from the surface of the sample. This generated steam is conveyed into the torch 9 by the gas sent from the air supply gas inlet 5. The transported gas and generated steam are
In the waveguide 13, the microwave energy is supplied, and the gas generated by being excited by the same energy supply only with the insufflation gas in advance. It collides with the flame and is excited into a plasma state. FIG. 2 is a sketch showing the detailed structure of the waveguide 13 and its surroundings, and the vapor is turned into plasma by microwave excitation from the output section 22 of the magnetron 11. In order to perform this excitation efficiently. In the present invention, movable shorting plates 121 and 122 are provided. That is, the impedance between the aperture 14 and the movable short-circuit plate and between the aperture 14 and the movable short-circuit plate 122 is adjusted by moving the positions of both the movable short-circuit plates 121 and 122, and the most stable plasma is obtained. Make flame 21 occur. Returning to FIG. 1, the plasma flame 21 of generated vapor excited as described above generates synchrotron radiation by transitioning from the plasma excited state to the ground state or metastable state. Condensing system 15 for photometry
The light is focused by the spectral unit 16 and separated into spectra by the spectrometer 16. The light after this spectroscopy is
The light is received by the detection section 18 to which a high voltage is applied by the high voltage power supply 17, is sensitized by the amplification sections 1 and 9, and the type and light intensity of the spectral line of the component is recorded in the recording section 20. According to experiments based on the above embodiments, the surface area when quantifying the surface of a microscopic part is on the order of several μφ and the depth is on the order of 1 μ.

The measurement sensitivity was such that it was possible to quantify on the order of Ppm to Ppb, and the analytical accuracy was within several percent. It was also confirmed that unlike conventional methods, there was almost no contamination of the sample from the electrodes, and the analysis time was short. As is clear from the above description, according to the present invention, compared to the conventional laser prog emission spectrometer, contamination caused by the electrode during auxiliary excitation such as atomic vapor generated from the sample surface, and contamination generated from the sample measurement surface. Contamination by vapor diffusion and dust from the surrounding atmosphere can also be largely eliminated.

Moreover, since the mixture of atomic vapor and plasma state can be removed by effective excitation using microwaves, high-range, high-precision measurements are possible. In addition, regarding the configuration and shape of the power supply for applying between the auxiliary electrodes of the conventional device,
Since the excitation is performed using a microwave power source while matching the plasma emission conditions, this part can be reduced to a fraction of the size.
It can be made lighter.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the detailed structure of a microwave vibrating section. 2...Lower oscillator, 5...Air supply gas inlet section, 6...
・Sample, 7... Sample stage, 11... Magnetron, 1
21, 122...Movable short circuit plate, 13...Waveguide, 1
4... Aperture, 16... Spectroscopic section, 21... Plasma flame.

Claims (1)

[Claims] 1. Sending the sample vapor generated by the laser beam irradiation to a waveguide section using an air supply gas, and generating a plasma flame of the sample vapor in the waveguide section using microwave energy,
In an optical emission spectrometer configured to analyze the sample by spectroscopically analyzing synchrotron radiation emitted from the plasma flame, the waveguide section is provided with a plasma of the sample vapor generated by the microwave energy. An optical emission spectrometer characterized by being equipped with an aperture and a movable short circuit plate for efficiently generating flame.