JP2571577B2 - Determination of boron and nitrogen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a simple separation operation which is quick and does not require correction of chemical yield within about 2 half-lives for a carbon-11 half-life of 20 minutes. And high-sensitivity, high-precision quantitative analysis of boron and nitrogen.

[Conventional technology]

Conventionally, for example, boron in gallium arsenide has been analyzed by secondary ion mass spectrometry (SIMS), spark source mass spectrometry (SSM
S), ion microanalyzer (IMA), and inductively coupled plasma emission spectroscopy (ICP). The detection limits in such SIMS, SSMS, IMA and ICP analysis methods are 3.3 ppb (1 × 10 ¹⁵ cm ⁻³ ) and 0.14 ppb (4.2 ×
10 ¹³ cm), 3.7 ppb (1.3 × 10 ¹⁵ cm ⁻³ ) and 50 ppb (1.5 × 1
0 ¹⁶ cm ^-3 ), but the standard sample must be evaluated by some method, such as detection of boron in the standard sample by activation analysis, and the detection limit is high [Kurosawa et al. , Applied Physics, vol. 54, p. 1074 (1985), J.
C. Blythe (JCBrice) et al. Journal of Materials Science (J. Mater. Sci.) Volume 2, 131
Page (1967), AM Huber, Journal of Radio Analytical Chemistry (J. Radi)
oanal.Chem.) 12, p. 75 (1972), Kurosawa et al., IEICE Transactions J67-C, p. 977 (1984)].

On the other hand, for example, N in gallium arsenide is SIMS and SSMS.
The detection limit was 0.2 ppm (4.6
× 10 ¹⁶ cm ^-3 ) and 0.1 ppm (2.3 × 10 ¹⁶ cm ^-3 ), making it difficult to analyze nitrogen in high-purity gallium arsenide.

On the other hand, if activation analysis is applied to the determination of boron in gallium arsenide, highly sensitive quantification can be achieved only by measuring radioactivity. In activation analysis using the nuclear reaction between deuteron and boron-10, there is a report that boron was quantified by a nondestructive method of measuring radioactivity without performing any operation such as chemical separation on the activated sample [ Yonezawa et al., Proceedings of the 29th Symposium on Radiation Chemistry, p. 240]. The detection limit in this case is 110pp
b (3.3 × 10 ¹⁶ cm ⁻³ ), making it difficult to quantify lower concentrations of boron. Furthermore, carbon-11 produced in nuclear reaction (half-life 20.38 min) through a CuO column, after the carbon dioxide is adsorbed on Asker light, the detection limit 0.7ppb (2 × 10 ¹⁵ cm
^-3 ), there is a report that quantified boron.
ki) et al., Japanese Journal of Applied Physics (JJAppl.Phys.), vol. 24, p. L801 (19
84)].

Usually, in activation analysis in which chemical separation of quantitative radionuclides (carbon-11) is performed, a non-radioactive isotope is added as a carrier, and the radioisotope and non-radioactive isotope carrier species are combined, and then the chemical separation is performed. After quantifying the element, the separation efficiency of the quantitative nuclide associated with the separation operation is accurately determined by a general chemical operation such as a volumetric method. However, in the above-mentioned adsorption separation operation, it is difficult to add a non-radioactive isotope as a carrier within 40 minutes and to carry out chemical separation after aligning carbon species. It is difficult to accurately determine the separation yield of the quantitative radionuclide (carbon-11) associated with the above, and it is difficult to obtain a reliable and reproducible analysis result. There have been no reports of quantifying nitrogen in gallium arsenide by activation analysis.

[Problems to be solved by the invention]

As described above, in analysis methods such as SIMS, SSMS, IMA, and ICP, it is necessary to obtain a quantitative value after evaluating a standard sample, and that the detection limit is high, and furthermore, deuterium and boron- In the determination of boron by charged particle activation analysis using 10 nuclear reactions, the detection limit is high in the case of the nondestructive method, and it is difficult to accurately determine the separation yield when a chemical separation operation is involved. There are disadvantages.

The present invention has been made in view of the above points,
Highly sensitive and accurate quantification of boron and nitrogen using a simple chemical separation that does not require correction of the chemical yield while performing chemical separation, and uses a rapid chemical separation within 40 minutes with a carbon-11 half life of less than 40 minutes It is an object of the present invention to provide a method that can be carried out at

[Means for solving the problem]

In general, the present invention relates to a method for quantifying boron and nitrogen, and irradiates a deuteron or a proton to cause a nuclear reaction with boron-10 and nitrogen-14, thereby forming a carbon-containing compound.
In the boron and nitrogen determination method to measure 11 radioactivity,
A carbon compound serving as a carrier is added to the carbon-11, the carbon-11 is added with a strong oxidizing agent together with the carbon in the carbon compound to form carbonate ions, and then separated as carbon dioxide, and the carbon dioxide is converted into an alkaline solution. After collection, a substoichiometric amount of an alkali metal or an alkaline earth metal is added to precipitate as a carbonate, the substoichiometric separation is performed, and the radioactivity of carbon-11 is measured.

According to the present invention, first, an analysis sample is irradiated with deuterons or protons to convert boron-10 or nitrogen-14 in the analysis sample into carbon-11. Further, in the present invention, a known amount of a comparative standard sample is irradiated with deuterons or protons. Such a comparative standard sample may be basically any one containing a known amount of boron or nitrogen. For example, boron oxide or silicon nitride can be used as a reference sample.

Next, a carbon compound as a carrier is added to the irradiated analysis sample and then dissolved to obtain an analysis sample solution. This carbon support may be basically any. For example, one or more of potassium carbonate, amorphous carbon and the like can be used. When the carbon support is amorphous carbon, the solution is oxidized by adding a strong oxidizing agent to the solution to form carbonate ions. Then, carbon-11 is separated as carbon dioxide by volatilization, etc., and a certain amount of carbon is separated as a carbonate by using an alkali metal or alkaline earth metal salt having a small solubility product with carbon ions, and a substoichiometric separation is performed. I do. Alkali metal salts or alkaline earth metal salts used for the substoichiometric separation of carbon include calcium chloride and lithium chloride.

By comparing the radioactivity of carbon-11 in the obtained analytical sample and the radioactivity of carbon-11 in the comparative standard sample, boron and nitrogen can be quantified with high sensitivity and high accuracy.

Unlike conventional methods, during the chemical separation of carbon-11, a carbon compound (carrier) containing the non-radioactive isotope carbon-12 is added, and after pre-separation as carbon dioxide gas, a certain amount of carbonate is accurately obtained as a carbonate. Need not be determined in a separate operation. In addition, for example, even in the case of gallium arsenide, after activation, after performing the chemical separation, the operation can be performed within 40 minutes until radioactivity measurement, so that the detection limit can be set to 1 ppb. There are advantages. In addition,
When boron and nitrogen coexist, both values can be obtained as a subtraction value from the respective values obtained using deuterons and protons as usual.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

Embodiment 1 FIG. 1 shows a gallium arsenide (GaA) according to an embodiment of the present invention.
FIG. 4 is a process chart showing a chemical separation operation for quantifying boron and nitrogen contained in s).

Operation 1: irradiated GaAs sample and comparing each current value Ix to boron oxide or silicon nitride, which is a standard sample, Is, the irradiation time t _X, deuterium or hydrogen under the condition of t _s. Thereby, carbon-11 as a radionuclide is generated from boron-10 or nitrogen-14 in the GaAs sample and the comparative standard sample.

Operation 2: After etching to remove surface contamination, Ga
The As sample was dissolved in 20 ml of an ammonia-hydrogen peroxide mixed solution together with potassium carbonate as a carbon carrier.

Operation 3: 5 ml of concentrated sulfuric acid was added to the obtained GaAs sample solution, and carbon-11 was separated as carbon dioxide gas by flowing nitrogen gas, and absorbed in sodium hydroxide solution.

Step 4: for the amount of carbon added as a carrier to the absorption solution,
Add a fixed (bare equivalent) barium chloride solution less than the equivalent. After adjusting the acidity of the solution to a weak alkali and ripening the barium carbonate (BaCO ₃ ) precipitate, the precipitate was suctioned off and used as a measurement sample. This operation may be performed again.

Step 5: The radioactivity of the measurement sample obtained in step 4 and the comparative standard sample obtained in step 1 are measured by a pair of detectors, for example, a coincidence device comprising BGO (Bi ₄ Ge ₃ O ₁₂ ). The amount of boron or nitrogen in the analysis sample is M _X , the current value of the irradiation conditions, the irradiation time is I _X ,
t _X, the projected range of deuterium and hydrogen into the analysis sample R _X, radioactivity a _X after substoichiometric separated, the substoichiometric separation rate and Y, boron or nitrogen content in the reference standard sample, the irradiation conditions current, irradiation time, the projected range, the radioactivity of each _{M S, I S, t S} , R S, boron or nitrogen content M _X analytical sample with a a _S is represented by the following formula.

M _X = M _S (I _S / I _X ) (S _S / S _X ) (R _S / R _X ) (a _X / a _S ) (1 / Y) where S _X and S _S are saturation coefficients , S _X = 1−exp (−
Represented by _{0.693t X /20.38),S S = 1-exp} (-0.693t S /20.38).

FIG. 2 is a view showing the influence of a carbon carrier (potassium carbonate) when a fixed amount of a barium chloride solution as a precipitant is added in the substoichiometric separation in the operation 4. That is, FIG. 2 shows the amount of BaCO ₃ precipitated (mm) when 0.6 mmol of a barium chloride solution was added and 0.15 to 1.8 mmol of potassium carbonate was added.
4 is a graph showing the relationship between the ol vertical axis) and the amount of added potassium carbonate (mmol horizontal axis). The inclined portion in FIG. 2 indicates a region where the barium chloride solution is in excess of the carbon carrier, and a region parallel to the horizontal axis indicates a substoichiometric separation region of carbon. It is understood that the use of a region parallel to the horizontal axis in FIG.

Table 1 shows that a known amount of carbon-
11 shows the carbon absorption rate and the sedimentation rate when carbon-11 was separated according to the operation shown in FIG.

As shown in Table 1, the absorption increased from 6.3% to 55% or more by increasing the basicity of the absorbent. Further, the precipitation rate of carbon was 50.5 for 1.2 mmol of potassium carbonate.
%, 25.3% for 24 mmol, 0.6 mmol added
Theoretical precipitation rate of BaCO ₃ obtained by barium solution of 50
% And 25%, respectively. From the results in Table 1, if the amount of carbon carrier added at the beginning and the amount of barium chloride added at the last equivalent are determined, the separation (precipitation) rate of carbon-11 is determined, and the chemical yield is determined by another operation. It turns out that there is no need to ask. The time required for this operation was about 40 minutes, which enabled separation with a half-life of 20.38 minutes for carbon-11. As a result, the detection limit of boron and nitrogen in gallium arsenide was 1 ppb (B 3 × 10 ¹⁴ cm ^-3 , N
2.3 × 10 ¹⁴ cm ^-3 ).

Table 2 shows the results of quantification of boron in carbon-doped and undoped GaAs produced by the liquid entrapment pulling method (LEC method).

The present invention has the advantage that boron and nitrogen can be quantified with high sensitivity and high accuracy without the need to correct the chemical yield.

Example 2 Determination of boron in NBS standard sample steel (SRM1265a) Here, in operation 2 of Example 1, the steel was dissolved with dilute sulfuric acid and hydrogen peroxide, and a carbon carrier was added to obtain a sample solution. Other operations are the same as those in the first embodiment. The quantitative value of boron was 1.32 ± 0.02 ppm, which was in good agreement with the guaranteed value of NBS of 1.3 ppm.

As described in Example 2, in the present invention, boron and nitrogen contained in other semiconductor materials, high-purity materials, and the like can be quantified only by changing the method of dissolving the analysis sample in operation 2.

〔The invention's effect〕

As described above, according to the method for determining boron and nitrogen according to the present invention, the analysis sample is not limited to the GaAs of the example. Further, there is an advantage that boron and nitrogen can be quantified with high sensitivity and high accuracy by a simple separation operation and without performing the yield correction accompanying the chemical separation operation.

[Brief description of the drawings]

FIG. 1 is a flow chart showing the operation steps of one embodiment of the method for quantifying boron and nitrogen in gallium arsenide according to the present invention, and FIG. It is the graph which showed the relationship of the precipitation amount of barium carbonate.

Continuation of front page (72) Inventor Toshio Shigematsu 162 Shirane, Shikata, Tokai-mura, Naka-gun, Ibaraki Pref. )

Claims (1)

(57) [Claims] 1. A method for determining the radioactivity of carbon-11 formed by irradiating deuterons or protons to cause a nuclear reaction with boron-10 and nitrogen-14, and determining the radioactivity of the formed carbon-11.
A carbon compound serving as a carrier was added to 11, and the carbon-11 was separated as carbon dioxide by adding a strong oxidizing agent together with the carbon in the carbon compound to form carbonate ions, and the carbon dioxide was collected in an alkaline solution. A method for quantifying boron and nitrogen, comprising adding a sub-equivalent of an alkali metal or an alkaline earth metal to precipitate as a carbonate, separating the sub-equivalent, and measuring the radioactivity of carbon-11.