JP5468992B2 - Temperature-programmed desorption analysis method and temperature-programmed desorption analyzer - Google Patents

Description

  The present invention relates to a temperature-programmed desorption analysis method and a temperature-programmed desorption analyzer that analyze components in a solid sample.

  Among the components present in a solid sample, there is a temperature programmed desorption analysis method as a method for analyzing a gas component or a component desorbed as a gas at a high temperature (see Non-Patent Document 1). An apparatus for performing temperature-programmed desorption analysis is called a temperature-programmed desorption analyzer.

  The temperature-programmed desorption analysis method was originally mainly used as an analysis method for measuring contaminant gas components and adsorbed components on the semiconductor surface and inside the semiconductor with respect to the semiconductor material. However, in recent years, it has also been used as an analytical method for measuring the amount of intrusion of gas components such as hydrogen that impair the mechanical properties of steel.

  Temperature-programmed desorption analysis is usually performed by increasing the temperature of a solid sample at a constant temperature rise rate in a vacuum, and desorbing the gas component from the solid sample at each temperature and releasing it into the vacuum, such as electron impact. The ionized gas component is fractionated for each mass / charge ratio by a mass spectrometer and guided to a detector, and the amount of the ionized gas component is measured as a current value. Alternatively, each ionized gas component is detected as a voltage pulse, and the voltage pulse is amplified and counted. That is, the signal is a current or counted pulse of ions having a certain mass / charge ratio derived from a certain gas component. A graph in which the horizontal axis represents temperature and the vertical axis represents signal intensity is called a temperature programmed desorption spectrum.

  From the temperature programmed desorption spectrum in which a component present in a solid sample is desorbed as a gas, knowledge about the energy for desorbing the component as a gas can be obtained. Since the existence state in the solid sample is closely related, the existence state of the component existing in the solid sample can be known by obtaining the temperature-programmed desorption spectrum. The energy is referred to herein as activation energy. For example, if a temperature-programmed desorption spectrum can be measured for a component in a solid state that is strongly bound to a trap site in a solid and the temperature-programmed desorption spectrum can be analyzed, the activation energy at this time is weakly bound. It is shown that it is higher than the activation energy in the state.

Michihiko Nagumo, “Basics of Hydrogen Embrittlement Behavior of Hydrogen and Embrittlement Mechanism,” Uchida Otsukuru, p. 55-56, 2008

  In a temperature-programmed desorption analysis method using a known technique, if a temperature-programmed desorption spectrum in which a component present in a solid sample is desorbed as a gas can be measured and the temperature-programmed desorption spectrum can be analyzed, Knowledge should be obtained and the presence state of the components present in the solid sample should be known, but the analysis is not easy.

For example, if the rate of temperature rise is a positive constant r, the activation energy is E _a , the gas constant is R, and the temperature at which the temperature-programmed desorption spectrum of a component in a certain presence state shows a peak, that is, the peak temperature is T _p . There is the following relationship.

This equation (1) indicates that the peak temperature T _p of the temperature programmed desorption spectrum of the component in a certain existing state varies with the temperature rising rate r. Then, ln (r / Tp ² ) is set to 1 / Tp using T _p obtained experimentally when several temperature-programmed desorption spectra are measured under the condition where the temperature-raising rate r is changed. When plotted, a straight line is obtained, and the activation energy E _a can be obtained from the slope of the straight line using a known gas constant R.

  At this time, in order to obtain a straight line, the number of experiments under the condition that the heating rate r is changed is theoretically two times. However, in order to obtain a straight line experimentally, there is an error in the experiment. Considering that, the number of experiments is required to be at least 3 times.

  However, if the experiment under the condition where the heating rate r is changed is performed three times, for example, three samples (hereinafter referred to as the same sample) in which the components present in the solid sample can be regarded as the same existence state must be prepared. I must. In three experiments, a sample must be put into the apparatus every time, and the apparatus must be in a high vacuum state that allows measurement. Of the three experiments, the measurement time is often 3 hours or more under the condition of the lowest rate of temperature increase. Further, during each experiment, it is necessary to lower the temperature to about room temperature, but it usually takes about 1 hour to lower the temperature. That is, it takes time to perform all measurements, and it may take a day.

  In addition, the condition that three samples that can be regarded as the same are prepared is possible if the sample is prepared by artificial control, but even if the sample is obtained from the natural world or is an artificial object, When the sample is taken out from the environment after exposure, there is only one sample, and it is impossible to satisfy the condition that three samples that can be regarded as the same are prepared.

  As described above, the temperature-programmed desorption analysis method using a known technique can measure a temperature-programmed desorption spectrum in which a component present in a solid sample is desorbed as a gas. It is not easy to perform analysis for knowing the existence state of components present in a solid sample, and in some cases it was impossible.

  The present invention has been made in order to solve the above-described problems. The activation energy value of the component in the solid sample can be easily obtained, and the presence state of the component in the solid sample can be known. It is an object to provide a thermal desorption analysis method and a temperature-programmed desorption analyzer.

The present invention relates to a temperature-programmed desorption analysis method in which a solid sample is heated, a gas generated from the solid sample is detected while the solid sample is heated, and components in the solid sample are analyzed from the gas detection results. A temperature raising step for raising the temperature of the solid sample, the temperature of the solid sample being heated is a first function having time as a variable, a certain positive number is a radix, and an inverse of the first function is an index. The first function is provided so that the second function to be integrated can be integrated over time, and the primitive function of the second function is an elementary function.
Moreover, one configuration example of the temperature programmed desorption analysis method of the present invention is characterized in that the first function is given as a function that is inversely proportional to a linear expression of time.
In addition, one configuration example of the temperature programmed desorption analysis method of the present invention further includes a detection step for detecting a gas component generated from the solid sample during the temperature increase of the solid sample, and a temperature programmed desorption that is a detection result of the gas component. And a calculation step for obtaining the activation energy value of the component in the solid sample by fitting the desorption spectrum and the theoretical curve of the thermal desorption spectrum.

In addition, the present invention is a temperature-programmed desorption analysis in which a solid sample is heated, a gas generated from the solid sample is detected while the solid sample is heated, and components in the solid sample are analyzed from the gas detection result. The apparatus comprises a temperature raising means for raising the temperature of the solid sample, and a control means for controlling the temperature raising means to control the temperature of the solid sample, and the temperature of the solid sample being heated is made variable with time as a variable. A first function, a second function whose base is a positive number and the reciprocal of the first function as an exponent can be integrated over time, and the primitive function of the second function is an elementary function Thus, the first function is given.
Further, one configuration example of the temperature-programmed desorption analyzer of the present invention is characterized in that the first function is given as a function that is inversely proportional to the linear expression of time.
Further, one configuration example of the temperature-programmed desorption analyzer of the present invention further includes a detection means for detecting a gas component generated from the solid sample during the temperature rise of the solid sample, and a temperature-programmed desorption that is a detection result of the gas component. And a calculation means for obtaining a value of activation energy of a component in the solid sample by fitting the desorption spectrum and the theoretical curve of the thermal desorption spectrum.

  According to the present invention, the temperature of the solid sample being heated is a first function with time as a variable, and a second function with a certain positive number as a radix and an inverse of the first function as an index is a function of time. By providing the first function so that it can be integrated and the primitive function of the second function is an elementary function, the temperature-programmed desorption spectrum for a certain component in a certain existing state can be directly interpreted. It becomes like this. Specifically, the thermal desorption spectrum obtained experimentally is associated with the theoretical thermal desorption spectrum, whereby the activation energy values of the components in the solid sample can be easily obtained. It is possible to know the presence state of the component in the sample.

  In the present invention, the first function is given as a function inversely proportional to the linear expression of time, which is one of the rational functions obtained by the four arithmetic operations of the polynomial function. Thereby, in this invention, it becomes possible to directly interpret the temperature-programmed desorption spectrum for a certain component in a certain existing state.

It is a figure which shows an example of the temperature rising curve in the temperature rising desorption analysis method and the temperature rising curve in the temperature rising desorption analysis method which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the temperature-programmed desorption analyzer which concerns on embodiment of this invention. It is a figure which shows the concept of the temperature rising control in the temperature desorption analysis method which concerns on embodiment of this invention. It is a figure which shows an example of the temperature-programmed desorption spectrum in embodiment of this invention.

[Principle of the Invention]
In a temperature-programmed desorption analysis method using a known technique, when a temperature-programmed desorption spectrum in which a component present in a solid sample is desorbed as a gas is measured, the temperature-raising rate is basically constant. The temperature-programmed desorption analysis method is abbreviated as TDS (Thermal Desorption Spectroscopy), but the term TPD (Temperature Programmed Desorption) also exists as a term indicating the same analysis method. However, even in the case of TPD, the temperature is such that the temperature rising rate is constant, whether it is rapidly raised and lowered in a delta function (flash heating), or rapidly raised in a step function and kept constant. Only program controlled.

In a temperature-programmed desorption analysis method using a known technique, when the temperature-raising rate is constant, which is a general condition, the temperature-raising rate is a constant positive number r, and the activation energy of a certain existing component is E _a , the gas constant is R, the temperature during measurement is T, the temperature at the start of measurement is T ₀ , the amount of a certain component in the solid sample at temperature T ₀ is 1, and the temperature in the solid sample at temperature T is 1 When the amount of the component is 1-x, when the elimination reaction is represented by a primary reaction, the amount per unit time that the component in the solid sample becomes a gas at a certain time t is desorbed in the solid sample. Is proportional to the amount of the component.

  Here, k is a proportionality constant, but changes with temperature in the temperature programmed desorption analysis.

  Here, A is a constant called a frequency factor. The temperature T during measurement is represented by the following equation (4) using the temperature rising rate r.

  Equation (4) can be regarded as defining temperature T as a first function with time as a variable. From the equations (3) and (4), the following equation (5) is obtained.

  Expression (6) is obtained from Expression (2), and the following Expression (7) is obtained.

  Expression (7) can be transformed as the following Expression (8).

Expression (8), which is a modification of Expression (7), is the primitive of the second function with the positive number exp (−E _a / R) as the radix and the reciprocal of the first function represented by Expression (4) as the exponent. Contains a function, but this primitive function is not represented by an elementary function. The theoretical temperature-programmed desorption spectrum shape of a component in a certain existing state is given by the following equation (9) obtained by differentiating equation (8) with respect to time.

Since the right side of equation (9) cannot be expressed by the four arithmetic operations and synthesis of elementary functions, the activation energy E _a and the frequency are calculated when trying to analyze the temperature programmed desorption spectrum obtained by the experiment using equation (9). A numerical value must be applied to the factor A to calculate the formula (9) numerically. However, in the calculation for obtaining the optimum value of the activation energy E _a while fitting the temperature-programmed desorption spectrum obtained in the experiment with the equation (9), the calculation amount becomes enormous. However, it is not easy to analyze the temperature-programmed desorption spectrum obtained by the experiment by the equation (9).

  According to the present invention, a second function having a temperature as a first function with time as a variable, a certain positive number as a radix, and an inverse of the first function as an index can be integrated with time, and A temperature-programmed desorption analysis method that provides a first function and a temperature-programmed desorption analyzer that realizes a temperature-programmed desorption analysis method so that the primitive function of the second function is an elementary function. As a specific example, the first function is given as a function such as the following expression (10) that is inversely proportional to the linear expression of time. Here, the elementary function refers to a function displayed by a polynomial function having a complex number as a variable, an exponential function, an arithmetic operation of a logarithmic function, or synthesis.

By determining the values of α and β so that T = T ₀ when t = 0 at the start of measurement and T = T _f when t = t _f at the end of measurement, the following equations (11) and (11) (12) is obtained.

  From the equations (3) and (11), the following equation (13) is obtained.

  Here, the following formula (14) is established.

  At this time, the following formula (15) is obtained from the formula (2).

C in Formula (15) is a constant. This equation (15) includes a primitive function of a second function in which the positive number exp (−E _a / R) is a radix and the reciprocal of the first function represented by the equation (10) is an exponent. An example in which a function is represented by an elementary function is shown. From the equation (15), the following equation (16) is obtained.

  When t = 0, the constant C is obtained from the condition that x = 0.

  The theoretical temperature-programmed desorption spectrum shape for a component in a certain existing state is given by the following equation obtained by differentiating equation (17) with respect to time.

The right side of Equation (18) is expressed by four arithmetic operations and synthesis of elementary functions. Therefore, by correlating the shape of the temperature programmed desorption spectrum obtained in the experiment with the theoretical curve expressed by Equation (18), the optimal value of activation energy E _a can be easily obtained. Therefore, the temperature programmed desorption spectrum obtained in the experiment can be directly interpreted.

[Embodiment]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a temperature rise curve in a conventional temperature programmed desorption analysis method and a temperature rise curve in the temperature programmed desorption analysis method of the present embodiment. 100 in FIG. 1 shows a temperature rising curve in the conventional temperature programmed desorption analysis method, and 101 shows a temperature rising curve in the temperature programmed desorption analysis method of the present embodiment.

  In the temperature rising curve in the conventional temperature-programmed desorption analysis method, the temperature rising rate is a constant value, which is 10 K / min in the example of FIG. In the temperature rise curve in the temperature programmed desorption analysis method of the present embodiment, the temperature T (unit K) is represented by a function that is inversely proportional to the linear expression of time t. This function is given by equation (11). In the case of the example of FIG. 1, the value of α is 1/27000 from the equation (12). The temperature rise curve in the temperature programmed desorption analysis method has a condition that it must be expressed by a monotonically increasing function of time, and the temperature rise curve in the temperature programmed desorption analysis method of the present embodiment satisfies this condition. Satisfied.

  FIG. 2 shows a configuration example of the temperature programmed desorption analyzer according to the present embodiment. In the example of FIG. 2, the sample is heated by an infrared lamp. The sample 202 carried into the vacuum chamber 201 is placed on a heat conducting rod 204 that is thermally connected to an infrared lamp 203 serving as a temperature raising means. The temperature of the sample 202 is measured by the thermocouple 205 installed most recently, and the value of the measured temperature is output from the thermocouple monitor 206. If there is a difference between the temperature value indicated by the thermocouple monitor 206 and the temperature of the sample 202, the temperature indicated by a thermocouple (not shown) directly attached to the sample 202 and the temperature indicated by the thermocouple monitor 206 are preliminarily determined. What is necessary is just to obtain | require the difference with a value and to calibrate. Here, it is assumed that the temperature of the sample 202 is equal to the temperature value indicated by the thermocouple monitor 206.

  A temperature controller 207 serving as a control unit acquires the temperature value indicated by the thermocouple monitor 206, and in accordance with the setting before measurement by the measurer, the infrared ray is transmitted so that the temperature of the sample 202 becomes a specified value at a specified time. The current value flowing through the lamp 203 is controlled. As a method of feeding back the temperature value indicated by the thermocouple monitor 206 and controlling the temperature of the sample 202 to a desired set temperature, proportional control (P control), integral control (I control), differential control (D control). There is PID control that integrates these, and usually PID control that is most easily controlled is adopted. Commercially available temperature controllers usually support PID control.

  A part of the gas component desorbed from the sample 202 and released into the vacuum at a certain time is ionized by an ion method such as electron bombardment in the ionization chamber 208, and the ionized gas component is mass / The sample is taken for each charge ratio, guided to the detector 210, and the amount of the ionized gas component is measured as a current value by the detector 210. Alternatively, each ionized gas component is detected as a voltage pulse by the detector 210, and the voltage pulse is amplified and counted.

  Thus, the detector 210 outputs a current or counted pulse of ions having a certain mass / charge ratio derived from a certain gas component as a signal. A diagram in which the horizontal axis represents time (elapsed time when the start time is 0) and the vertical axis represents signal intensity is an example of a temperature programmed desorption spectrum to be analyzed in the present embodiment. The computer 213 can display the temperature-programmed desorption spectrum on the display device 212 as indicated by 211 in FIG. 2, and can record it on an internal storage device (not shown) or an external recording medium ( (Not shown). The computer 213 includes a CPU, a storage device, and an external interface, and the CPU executes processing such as recording of experimental data and analysis of a temperature-programmed desorption spectrum according to a program stored in the storage device.

  Since the temperature rise curve 101 in the temperature programmed desorption analysis method of the present embodiment shown in FIG. 1 represents the set temperature at each time, PID control is performed so that the temperature of the sample 202 becomes the set temperature. Thus, the sample 202 can be heated according to the temperature rise curve 101. However, since the temperature rising curve 101 is more complicated than the temperature rising curve 100 in the conventional temperature rising desorption analysis method, a commercially available temperature controller strictly controls the temperature according to the temperature rising curve 101. Can not.

  Therefore, the temperature rise curve 101 in the temperature programmed desorption analysis method of the present embodiment is divided into several sections, and each section has a linear function temperature rise curve so that the original temperature rise curve is obtained. It can be an approximate curve of a curve. FIG. 3 shows the concept of such temperature rise control. In FIG. 3, the temperature rising curve 101 is divided into six sections, and the temperature rising curve 101 is approximated for each section to obtain approximate curves 300 to 305 of the temperature rising curve 101. Some commercially available programmable temperature controllers can set the number of the sections to several tens, and can be a sufficient approximate curve.

FIG. 4 shows an example of a temperature programmed desorption spectrum. In FIG. 4, 400 is experimental data obtained by heating the sample 202, and 401 is a theoretical curve that is a theoretical temperature-programmed desorption spectrum expressed by the equation (18). Here, the temperature-programmed desorption spectrum of hydrogen electrochemically added to the steel sample 202 is used as experimental data. The computer 213 analyzes the experimental data by associating the thermal desorption spectrum of the experimental data with the theoretical curve, which is the theoretical thermal desorption spectrum expressed by Equation (18), and activates the activation energy E _a. A value of 80 kJ / mol is obtained. In this example, the value of the activation energy E _a is closely related to the magnitude of the energy which hydrogen is trapped in the steel is solid. As described above, according to the present embodiment, it is possible to easily know the existence state of components present in a solid sample.

  The present invention is not limited to the embodiment described above, and is applicable to thermal analysis methods and thermal analysis devices other than temperature-programmed desorption analysis method and temperature-programmed desorption analysis device in vacuum. It is obvious that many variations are possible by those having ordinary knowledge in the art within the technical idea of the present invention.

  The present invention can be applied to a technique in which a solid sample is heated to analyze components in the solid sample.

  DESCRIPTION OF SYMBOLS 201 ... Vacuum chamber, 202 ... Sample, 203 ... Infrared lamp, 204 ... Thermal conducting rod, 205 ... Thermocouple, 206 ... Thermocouple monitor, 207 ... Temperature controller, 208 ... Ionization chamber, 209 ... Mass spectrometer, 210 ... Detection 211, temperature-programmed desorption spectrum, 212, display device, 213, calculator.

Claims (6)

In a temperature-programmed desorption analysis method in which a temperature of a solid sample is raised, a gas generated from the solid sample is detected during the temperature rise of the solid sample, and components in the solid sample are analyzed from the gas detection results
A heating step for heating the solid sample;
The temperature of the solid sample being heated is a first function with time as a variable, and a second function with a certain positive number as a radix and the reciprocal of the first function as an index can be integrated over time. And the first function is provided so that the primitive function of the second function is an elementary function. The temperature-programmed desorption analysis method according to claim 1,
A temperature-programmed desorption analysis method characterized in that the first function is given as a function inversely proportional to a linear expression of time. The temperature-programmed desorption analysis method according to claim 1 or 2,
Furthermore, a detection step for detecting a gas component generated from the solid sample during the temperature rise of the solid sample;
And a calculation step for obtaining a value of activation energy of a component in a solid sample by fitting a temperature desorption spectrum, which is a gas component detection result, and a theoretical curve of the temperature desorption spectrum. Thermal desorption analysis method. In a temperature-programmed desorption analyzer that heats a solid sample, detects gas generated from the solid sample during temperature rise of the solid sample, and analyzes the components in the solid sample from the gas detection result,
A temperature raising means for raising the temperature of the solid sample;
Control means for controlling the temperature of the solid sample by controlling the temperature raising means,
The temperature of the solid sample being heated is a first function with time as a variable, and a second function with a certain positive number as a radix and the reciprocal of the first function as an index can be integrated over time. The temperature-programmed desorption analyzer is characterized in that the first function is given so that the primitive function of the second function is an elementary function. The temperature-programmed desorption analyzer according to claim 4,
A temperature-programmed desorption analyzer, wherein the first function is given as a function inversely proportional to a linear expression of time. The temperature-programmed desorption analyzer according to claim 4 or 5,
Furthermore, detection means for detecting a gas component generated from the solid sample during the temperature rise of the solid sample;
And a calculation means for obtaining a value of activation energy of a component in a solid sample by fitting a temperature desorption spectrum, which is a gas component detection result, and a theoretical curve of the temperature desorption spectrum. Thermal desorption analyzer.

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