JP3058042B2 - Ion scattering analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion scattering analyzer.

[0002]

2. Description of the Related Art As one type of ion scattering analyzer, low energy ions (2 to 3 keV) are made to collide with atoms on a sample surface, and the intensity of ions scattered backward by the collision is measured. There is an apparatus for analyzing elemental species present on a sample surface. In this analyzer, for example, the intensity of scattered ions is measured while changing the ion incident angle on the sample, and the crystal structure is analyzed from the angle dependence data of the ion scattering intensity.

In the field of this type of ion scattering analysis, a technique of simulating ion scattering by a computer has been studied. As one of the techniques, a simulation calculation of ion scattering intensity is performed by using an ion incident angle as a measurement parameter. A technique for displaying the calculation result (angle dependence of ion scattering intensity) in a line graph has been disclosed.

[0004]

In the simulation of ion scattering, an ideal crystal structure of a sample is assumed, and a simulation calculation is performed based on the structure. The calculation result is based on the ion scattering intensity. Often does not match the actual measurement data.

[0005] In particular, in a low energy ion scattering analyzer, since the surface structure of a sample is sensitive, if there is a change in the surface structure, the simulation result will greatly differ from the measured data. In other words, since the surface of many materials usually differs from the ideal structure, even if the simulation calculation is performed assuming the ideal crystal structure, the calculation result does not match the measured data. become.

If the simulation result does not match the actually measured data, the operation for obtaining the actual crystal structure becomes extremely complicated. The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an ion scattering analyzer capable of easily obtaining an actual crystal structure from simulation data of ion scattering.

[0007]

A configuration for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The ion scattering analyzer of the present invention irradiates a sample S with ions. A measuring device 1 for measuring the intensity of ions scattered backward from the irradiation position while changing the angle of incidence of ions on the sample S, crystal structure data on constituent atoms of the sample S and the positional relationship of each atom, And incident ion species,
An input unit 2 for inputting incident conditions such as an incident energy and an incident angle, changing input crystal structure data, and an input unit 2
And a display unit 4 for displaying the calculation result and the actual measurement data obtained by the measuring device 1 by calculating the ion scattering intensity based on the crystal structure data and the incident conditions. Attached.

[0008]

In the analyzer according to the present invention, the data actually measured by the measuring device 1 and the result of the simulation calculation of the ion scattering are displayed on the display unit 4. From the display, the assumed structure used for the simulation calculation is actually changed. It can be easily determined whether or not the crystal structure matches.

In the analyzer of the present invention, the initial value (structure data) initially input in the simulation operation is an ideal crystal structure. The simulation result based on this initial value and the measured data are used. Therefore, as a next operation, the crystal structure of the initial value is changed, a simulation calculation is performed again, and the calculated value is compared with the actual measurement data. The operation of performing a simulation calculation is sequentially repeated by trial and error until the calculated value of the simulation matches the actually measured data.

Here, in the analyzer of the present invention, parameters for changing the crystal structure include a lattice constant, an element type of an atom present at a lattice point, the presence or absence of an atom at a lattice point, and the like.

When the crystal structure is changed from an initial value (ideal structure), the fact known in the field of this type of crystal structure analysis, for example, in the case of SrTiO ₃ , O (oxygen) of the surface layer escapes. Taking into account the tendency and form of the actual structural change of the crystal, such as ease, it is possible to eliminate unnecessary trial and error.

[0012]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. First, the analyzer of this example includes an ion scattering measurement device 1, an input device 2, an arithmetic processing device 3, and a display 4 such as a CRT.

The ion scattering measurement device 1 irradiates the sample S with ions (He ⁺ ) from the ion source 1a, and measures the intensity of the ions backscattered from the sample S by the ion irradiation on the same axis as the ion source 1a. This is a device that detects with a detector (MCP) 1b disposed and outputs a detected value of the scattering intensity.

In this measurement system, the sample S is held on the gonio stage 1c, and the angle of incidence α (φ) of the ions on the sample S is obtained by rotating the gonio stage 1c.
Can be set arbitrarily. Here, the incident angles α and φ are respectively PolarAngle (polar angle); α and Azimuth as shown in FIG.
Angle (azimuth angle);

The input device 2 is a keyboard or the like, and includes crystal structure data relating to element types of atoms constituting the sample and the positional relationship between the respective atoms, and incident ion types, incident energies, incident angles of ions, and the like. The ion incidence condition can be input to the arithmetic processing unit 3. However, since the analyzer according to the present invention measures the angle dependency of the ion scattering intensity, the ion incident angle in the above data is used as a measurement parameter to indicate the range in which the incident angle is changed and the width (step) of the angle change. It can be entered. Regarding the crystal structure data, it is assumed that an initial value can be sequentially changed after an ideal crystal structure is input.

On the other hand, the arithmetic processing unit 3 is, for example, a computer, and includes a measurement execution unit 3a and an actual measurement data storage unit 3.
b, simulation operation unit 3c, and display control unit 3d.

The measurement execution section 3a controls the measurement operation of the ion scattering measurement apparatus 1 based on the set value of the input measurement parameter [ion incident angle; α (φ)], and controls the gonio stage 1c. First, the ion incident angle is set to the initial value of the measurement range, and then the incident angle is sequentially changed for each setting step, and a start command signal is supplied to the ion scattering measurement device 1 for each angle setting. The control is performed, and the detected value of the scattered intensity for each execution of the measurement is sequentially stored in the measured data storage unit 3b corresponding to the ion incident angle.

The simulation calculation unit 3c uses the crystal structure data input from the input device 2, the incident ion species and the incident energy as the measurement parameters, and sets the ion scattering intensity for each step of the incident angle as a measurement parameter. Is configured to calculate Since the calculation formula used for the simulation calculation is publicly known, the description is omitted here.

The display controller 3d sets two individual display areas (windows) on the screen of the display 4,
In one of the display areas, the angle dependency data of the ion scattering intensity is displayed as a line graph (change curve) based on the storage content of the measured data storage section 3b, and at the same time, the simulation calculation section 3c displays the other display area. The calculation result is also configured to be displayed in a line graph.

Next, the analysis procedure of the embodiment of the present invention will be described with reference to SrT
The case of analyzing the structure of iO ₃ will be described as an example. First, the input device 2 inputs the structural data relating to an ideal crystal structure of SrTiO ₃ [FIG. 2 (A)] as an initial value, the incident ion species (the He ^+), each incidence condition of the incident energy and angle of incidence Enter At this time, for the incident angle, as described above, the range in which the incident angle is changed and the step of changing the angle are input.

When the analysis operation is started, actual measurement and simulation calculation by the ion scattering measurement device 1 are executed in parallel. In the ion scattering measurement operation, the ion scattering measurement is first performed with the incident angle set at the beginning of the measurement range by controlling the gonio stage 1c, and then the incident angle is changed by one step and the measurement is performed similarly. The above procedure is sequentially repeated, and the procedure ends when data collection at all measurement points is completed, and all of the actually measured data obtained by this one measurement is stored in the actually measured data storage unit 3b.

On the other hand, in the simulation operation, based on the input crystal structure data, the incident ion species and the incident energy, the ion scattering intensity is sequentially calculated using the ion incident angle as a measurement parameter. When both processes of the actual measurement are completed, the calculation result and the actually measured data are simultaneously displayed on the screen of the display unit 4.

At this time, the change curve displayed on the display unit 3 has a shape as shown in FIG. 3A in the case of the simulation result, while it has a shape as shown in FIG. 3B in the case of the actually measured data. It becomes a shape, and it turns out that it does not correspond when comparing the change curves of both.

Therefore, the crystal structure data used for the simulation calculation is changed, and how to make the simulation result coincide with the actually measured data is trial-and-error. In this example, SrTiO ₃ is used as an analysis target. Therefore, the tendency of the structural change, that is, SrT
Considering the well-known fact that iO ₃ easily releases oxygen from the surface, the crystal structure data of the model shown in FIG. Perform simulation calculations.

In this example, since the actual crystal structure is the structure shown in FIG. 2 (B), the simulation result is changed by performing the above trial and error only once, as shown in FIG. 3 (B). The curves will match perfectly. But,
In practice, the simulation result rarely coincides with the actually measured data by one trial and error. In such a case, the crystal structure is changed by, for example, changing the arrangement of the constituent atoms or changing the lattice constant. Then, simulation calculation is performed, and such a change in crystal structure → simulation calculation is repeated by trial and error until the simulation result matches the measured data to estimate the actual crystal structure.

Here, in the above-described embodiment, the actual measurement of the ion scattering intensity and the simulation calculation are configured to be executed by parallel processing. However, these processings are not necessarily parallel. However, the measurement of the angle dependence of the ion scattering intensity and the simulation calculation process
In each case, it takes more than one hour in many cases, so that it is practical and preferable to reduce the time by parallel processing.

In addition to the configuration of the embodiment of the present invention described above, each time crystal structure data is input, an atom bonding model as shown in FIG. The function to display on the screen may be added, and by providing such a function, it becomes possible to visually grasp the input crystal structure, and to change the crystal structure from the ideal structure of the input initial value. Can be performed more smoothly when changing is made sequentially.

In the data used in the embodiment of the present invention, the initial value (ideal structure) of the crystal structure data is as follows.
A method of preliminarily inputting data of a plurality of samples into a device by reading a magnetic disk or the like, storing the data in a memory or the like, and reading out the molecular structure data of a sample to be analyzed from the memory when performing analysis. May be adopted.

[0029]

As described above, according to the analyzer of the present invention, a measuring device for actually measuring the angle dependence of the ion scattering intensity, and a simulation calculation of the ion scattering intensity based on the assumed crystal structure. Since the calculation unit is configured to display the simulation result and the measured data, the simulation result is compared with the measured data to determine the actual crystal structure so that the simulation result approaches the measured data. As a result that a method of changing the assumed crystal structure becomes possible, the estimation work is facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 shows a crystal structure of SrTiO ₃ .

FIG. 3 is a diagram showing both a display example of a simulation result and a display example of actual measurement data.

FIG. 4 is a diagram showing Polar Angle α and Azimuth Angle φ

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion scattering measurement device 2 Input device 3 Arithmetic processing unit 3a Measurement execution part 3b Actual measurement data storage part 3c Simulation operation part 3d Display control part 4 Display

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 37/252 G01N 23/225

Claims (1)

(57) [Claims] An apparatus for irradiating a sample with ions and measuring the intensity of ions scattered backward from the irradiation position while changing the angle of incidence of the ions on the sample, a constituent atom of the sample and each atom thereof Crystal structure data on the positional relationship of
Input of input conditions such as incident ion species, incident energy, and incident angle, an input section for changing input crystal structure data, and simulation of ion scattering intensity based on crystal structure data and input conditions from the input section An ion scattering analyzer comprising: a calculation unit for calculating; and a display for displaying the calculation result and actual measurement data obtained by the measurement device.