JP2007033402A - Crystal evaluation method and crystal evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal evaluation method and a crystal evaluation device, capable of evaluating an internal structure of a crystalline thin film of perovskite type oxide. <P>SOLUTION: This device includes a measurement part 110 which irradiates X-rays to a sample including crystals of the perovskite type oxide placed on a sample stand and detects characteristic X-rays generated from the sample, and a processing part 50 which determines kinds of elements located at a specific crystal site based on intensity of the characteristic X-rays detected by the measurement part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a crystal evaluation method and a crystal evaluation apparatus.

Inkjet printers are known as printers that enable high image quality and high-speed printing. The ink jet printer includes an ink jet recording head having a cavity whose internal volume changes, and performs printing by ejecting ink droplets from the nozzle while scanning the head. As a head actuator in such an ink jet recording head for an ink jet printer, a piezoelectric element using a perovskite oxide represented by PZT (Pb (Zr, Ti) O ₃ ) has been conventionally used.

In recent years, since it is desired to increase the nozzle density at high speed in an ink jet printer, it is important to evaluate the internal structure of such a perovskite oxide crystalline thin film.
JP 2003-215069 A

  An object of the present invention is to provide a crystal evaluation method and a crystal evaluation apparatus capable of evaluating the internal structure of a crystalline thin film of a perovskite oxide.

The crystal evaluation method according to the present invention includes:
(A) irradiating a sample containing crystals of a perovskite oxide placed on a sample stage with an electron beam;
(B) detecting characteristic X-rays generated from the sample;
(C) determining a type of an element located at a specific crystal site based on the detected characteristic X-ray intensity;
including.

In the crystal evaluation method according to the present invention,
In the step (c), the amount of an element located at a specific crystal site can be determined.

In the crystal evaluation method according to the present invention,
In the step (c), the displacement of an element located at a specific crystal site can be determined.

In the crystal evaluation method according to the present invention,
In the step (a), an electron beam is irradiated from a plurality of incident angles,
In the step (b), characteristic X-rays can be detected for each incident angle.

In the crystal evaluation method according to the present invention,
The perovskite-type oxide crystal has an A site, a B site, and an O site,
In the step (a), an electron beam is irradiated from an incident angle parallel to a straight line connecting the A site and the O site adjacent to the A site,
In the step (c), the type of element located at the A site can be determined.

In the crystal evaluation method according to the present invention,
The perovskite-type oxide crystal has an A site, a B site, and an O site,
In the step (a), X-rays are irradiated from an incident angle parallel to a straight line connecting the A site and the B site adjacent to the A site,
In the step (c), the type of element located at the A site or the B site can be determined.

In the crystal evaluation method according to the present invention,
Before the step (a), further comprising obtaining orientation information indicating the orientation of crystals contained in the sample;
In the step (a), the electron beam can be irradiated from the incident angle determined based on the orientation information.

The crystal evaluation apparatus according to the present invention includes:
A measurement unit that irradiates a sample containing a perovskite-type oxide crystal placed on a sample stage with an electron beam and detects characteristic X-rays generated from the sample;
A processing unit that determines the type of an element located at a specific crystal site based on the intensity of the characteristic X-ray detected by the measurement unit;
including.

A program according to the present invention is stored in a computer.
A sample containing a perovskite-type oxide crystal placed on a sample stage is irradiated with an electron beam,
Detecting characteristic X-rays generated from the sample;
Based on the detected characteristic X-ray intensity, the type of element located at a specific crystal site is determined.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1. Crystal Evaluation Apparatus The crystal evaluation apparatus 100 according to the present embodiment irradiates a sample containing a perovskite oxide crystal with an electron beam, and is positioned at a specific crystal site based on the intensity of characteristic X-rays generated from the sample. The type and amount of elements to be determined can be determined.

The perovskite type has a crystal structure as shown in FIGS. 1 (a) and 1 (b), and the position indicated by A in FIGS. 1 (a) and 1 (b) is shown at A site and B. The position is called B site, and the position indicated by O is called O site. In the present embodiment, ions preferentially located at the A site are referred to as A site ions, and ions preferentially located at the B site are referred to as B site ions. For example, in Pb (Mg, Nb) O ₃ -xPbTiO ₃ (hereinafter referred to as PMN-PT), the A site ion is Pb ²⁺ and the B site ion is Mg ²⁺ , Ti ⁴⁺ and Nb ⁵⁺ . Note that O ²⁻ is located at the O site. The perovskite oxide includes a simple perovskite oxide and a composite perovskite oxide. The perovskite oxide can also be made of a relaxor material.

  The crystal evaluation apparatus 100 can evaluate the internal structure of the above-described perovskite oxide using so-called angle-resolved electron channeling X-ray spectroscopy (ALCHEMI-HARECXS).

  Angle-resolved electron channeling X-ray spectroscopy is a technique in which a sample is irradiated with X-rays from a plurality of incident directions and the crystal structure is analyzed using characteristic X-rays generated from the sample. In this measurement method, when strong diffraction occurs in the sample by irradiating the sample with X-rays, the incident electrons repeatedly scatter between transmitted waves and diffracted waves inside the sample, and a maximum amplitude is generated at a specific part of the crystal. Branches into several Bloch wave components. The excitation amplitude of each Bloch wave component depends on the incident direction of the electron beam. When a certain Bloch wave component is excited strongly, the incident electrons cause channeling that concentrates on a specific part of the crystal. The characteristic X-ray signal from the elements present in is enhanced. By this measurement, information on the types and amounts of elements located at specific crystal sites can be obtained.

  FIG. 2 is a block diagram showing the main functional configuration of the crystal evaluation apparatus 100 according to the present embodiment. The crystal evaluation apparatus 100 includes a measurement unit 110, a display unit 42, an input unit 44, a measurement control unit 46, a storage unit 48, and a processing unit 50. The detailed configuration of the measurement unit 110 will be described later.

  The measurement control unit 46 performs control for causing the measurement unit 110 to measure the sample. The processing unit 50 processes the measurement value measured by the measurement unit 110 and sends the processing result to the storage unit 48 or the display unit 42. The storage unit 48 serves as a work area for realizing various processing functions of the processing unit 50 and the measurement control unit 46 in addition to storing various setting data (for example, measurement control data). Can be realized by hardware such as RAM, ROM, optical disk, magneto-optical disk. The storage unit 48 may store a program for causing each unit of the crystal evaluation apparatus 100 to function. The crystal evaluation apparatus 100 can read the program stored in the storage unit 48 and realize the functions of each unit of the crystal evaluation apparatus 100. Moreover, it replaces with the memory | storage part 48, and also implement | achieves the function of each part of the crystal | crystallization evaluation apparatus 100 mentioned above by downloading the program etc. for implement | achieving each function mentioned above from a host apparatus etc. via a transmission line. Is possible.

  The display unit 42 may output an image of the setting state, the operating state, or the measurement result of the crystal evaluation apparatus 100, and its function is performed by known hardware such as a CRT, LCD, touch panel display, or the like. realizable.

  The input unit 44 is for an operator of the crystal evaluation apparatus 100 to input various setting data and operation data, and the function can be realized by hardware such as a keyboard, operation buttons, and a touch panel display.

  Next, details of the measurement unit 110 will be described. FIG. 3 is a diagram illustrating a detailed configuration of the measurement unit 110 according to the present embodiment. The measurement unit 110 has a function of irradiating the sample with X-rays from a specific incident angle and measuring the intensity of characteristic X-rays generated from the sample, and includes, for example, a transmission electron microscope (TEM). As shown in FIG. 3, the measurement unit 110 includes an electron beam source that irradiates an electron beam, an optical member 13 that collects the electron beam, and a detection unit 14 and a detection unit 15 that detect characteristic X-rays. The detection unit 14 and the detection unit 15 detect characteristic X-rays generated from the sample 12 including, for example, a crystal grown on the substrate. The optical member 13 condenses the sample 12 so that the focal point of the electron beam coincides. The X-ray source and detection unit 14 may have a goniometer structure that can rotate independently of each other about the rotation center. The detection unit 14 and the X-ray source may be provided so that the center of rotation coincides with the focal point of the optical member 13. The irradiation of the electron beam and the detection of the characteristic X-ray by the detection unit 14 can be sequentially performed while changing the angle with a goniometer.

2. Crystal Evaluation Method (1) First, orientation information indicating the orientation of crystals of the perovskite oxide included in the sample 12 is input from the input unit 44.

  (2) Next, the measurement control unit 46 determines the incident angle of the X-rays irradiated on the sample 12 based on the orientation information input from the input unit 44. Thus, the crystal evaluation apparatus 100 can determine the incident angle according to the orientation of the crystal contained in the sample by acquiring the orientation information. That is, the crystal evaluation apparatus 100 can predict the positions of the A site, the B site, and the O site in the crystal based on the orientation information. For example, the A site and the O site adjacent to the A site are connected. An incident angle parallel to the straight line can be determined. When an electron beam is irradiated from this incident angle, it is possible to detect the characteristic X-rays by separating the A site, the O site, and the B site. For example, the same element is located at the A site and the B site. However, the type and amount of each element can be determined by distinguishing between the A site and the B site.

  The crystal evaluation apparatus 100 can also determine an incident angle parallel to a straight line connecting the A site and the B site adjacent to the A site. By irradiating an electron beam from this incident angle, it is possible to detect the characteristic X-rays by separating the A site, the B site, and the O site. Therefore, the A site, the B site, and the O site are distinguished from each other. The type and amount of element can be determined.

  (3) Next, the measurement unit 110 emits X-rays from the incident angle determined by the measurement control unit 46 and detects characteristic X-rays generated from the sample 12.

  (4) Next, the processing unit 50 determines the type, amount, and displacement amount of the element located at a specific crystal site based on the characteristic X-ray detected by the measurement unit 110.

3. Experimental Example 3.1. Sample preparation
A (001) -oriented PMN-xPT (x = 32, 37 at%) single crystal was produced by the Bridgman method. Ag was formed as an evaluation electrode and subjected to polarization treatment with an electric field of 1 kV / mm.

The Bridgman method is a method of growing a crystal while gradually lowering a crucible enclosing a single crystal raw material, and mononucleating using a temperature gradient generated at a heater end portion. Pt crucible was filled with PbO, MgO, Nb ₂ O ₅ , TiO ₂ (each purity 99.99% or more) powder of PMN-PT at a ratio of each condition, and the crucible was placed in the furnace at 1380 ° C. or higher. Dissolve. After holding for about 10 hours, it was lowered at a speed of 0.1 to 1 mm / h to obtain a (001) -oriented PMN-xPT single crystal.

  A single crystal with x = 32 at% is designated as PMN-32PT, and a single crystal with x = 37 at% is designated as PMN-37PT.

3.2. Crystal Evaluation Method and Evaluation Results The following evaluations were performed on the obtained samples.

  PMN-32PT was analyzed by angle-resolved electron channeling X-ray spectroscopy (ALCHEMI-HARECXS). The experiment was performed on 111 and 130 system reflection rows.

  The 111-line reflection array can be analyzed by irradiating X-rays from an incident angle parallel to a plane on which the A-O site and the B site can be separately observed, that is, a straight line connecting the A site and the O site. It is a surface. The 130-line reflection array can be analyzed by irradiating X-rays from an incident angle parallel to a plane on which the AB site and the O site can be separately observed, that is, a straight line connecting the A site and the B site. Surface.

  In the 111 system, the characteristic X-ray intensity change of each constituent element when continuously tilting from −3 g to 2 g black condition and in the 130 system from −2 g to 2 g black condition was continuously observed. ) And the profile shown in FIG.

  FIG. 4 (a) shows the ALCHEMI-HARECXS experimental profile of PMN-32PT with 111 system reflection rows. FIG. 4B shows the theoretical value of the ALCHEMI-HARECXS profile of the 111 system reflection train.

In the experiment, the sample is tilted so as to be the [112] zone axis from [110], which is the sample preparation direction, and the sample is tilted to the [−110] direction therefrom, and only the g = 111 system reflection row is excited. It was. And the characteristic X-ray intensity change of each constituent element when making it incline continuously from -3g to 2g black conditions was observed continuously, and the profile was obtained. For comparison, Pb ²⁺ , Mg ²⁺ , Nb ⁵⁺ , Ti ⁴⁺ , and O ²⁻ occupy A, B, B, B, and O sites, respectively, based on the dynamic diffraction theory considering inner-shell electron excitation. FIG. 4 (b) shows a HARECXS theoretical profile assuming a certain ideal ion arrangement (no spontaneous displacement, no defect, sample thickness 150 nm). The HARECXS theoretical profile indicates the X-ray generation cross section (probability of generation) per atom of each normalized site. In order to simplify the calculation, the crystal structure is a cubic crystal (lattice constant: 4.018Å).

In FIG. 4A, the characteristic X-ray intensity varies greatly depending on the diffraction conditions, and in the range of −1 <k / g111 <1 with the symmetrical excitation condition interposed, Pb ²⁺ and O ²⁻ The signal was strong, and on the contrary, the signals of Nb ⁵⁺ and Ti ⁴⁺ were weakened, and it was confirmed that this intensity relationship was reversed on the higher-order reflection side. These trends are consistent with the theoretical intensity profile shown in FIG. 4 (b), the A-O site located is ^{Pb 2+} and O ^{2 over, the Nb 5+} and ^{Ti 4+} are located in the B-site Is qualitatively understood. Further, it was confirmed that Mg ²⁺ was deficient or substituted because the diffraction condition was weakly dependent and the behavior was clearly different from the theoretical intensity profile.

Next, FIG. 5 (a) shows the ALCHEMI-HARECXS profile of the 130 system reflection row. In the experiment, the sample was tilted from the [−310] zone axis, which is the sample preparation direction, to the [001] direction, and only the g = 130 system reflection train was excited. And the characteristic X-ray intensity change of each constituent element when making it incline continuously from -2g to 2g black conditions was observed continuously, and the profile was obtained. For comparison, an ideal ion arrangement in which Pb ²⁺ , Mg ²⁺ , Nb ⁵⁺ , Ti ⁴⁺ , and O ²⁻ occupy A, B, B, B, and O sites (no spontaneous displacement, no defect, sample thickness of 100 nm, respectively) FIG. 5 (b) shows the HARECXS theoretical profile that assumes).

In FIG. 5A, the characteristic X-ray intensity greatly changes depending on the diffraction condition, and Pb ²⁺ , Mg ²⁺ , Nb ^{5+ in} the range of −1 <k / g130 <1 with the symmetrical excitation condition interposed. , Ti ⁴⁺ signal is strong, and this intensity relationship is reversed on the higher-order reflection side. On the other hand, it can be seen that the O ²⁻ signal shows almost no dependence on the diffraction conditions. These tendencies are consistent with the theoretical intensity profile shown in FIG. 5 (b), where Pb ²⁺ , Mg ²⁺ , Nb ⁵⁺ , Ti ⁴⁺ are located at the AB site, and O ²⁻ is located at the O site. It is understood qualitatively. Comparing the characteristic X-ray intensities of Pb ^{2+ at} the A site and Nb ⁵⁺ and Ti ^{4+ at} the B site in FIG. 4, it can be seen that the dependence of the diffraction conditions of Nb ⁵⁺ and Ti ⁴⁺ is weak. If the amount of displacement from the lattice point is large, the intensity change near the black condition for higher-order reflection is suppressed, and this is interpreted as a decrease in intensity due to spontaneous ion displacement of the ferroelectric. The HARECXS method is sensitive not only to the ion arrangement in the local region, but also to the displacement from the lattice points of the atoms and the thickness of the sample. Therefore, the amount of spontaneous ion displacement can be quantified by comparing experimental results with theoretical calculations. It is.

FIG. 6B is a HARECXS theoretical profile when Mg ²⁺ and Pb ²⁺ are mutually substituted. FIG. 6 (a) shows the ALCHEMI-HARECXS experimental profile as in FIG. 4 (a). Specifically, FIG. 6B shows that about 45% (about 2 at%) of Mg ²⁺ (total amount of 4.32 at%) goes to the A site, and about 10% of equal amount of Pb ²⁺ (total amount 19.15 at%) is about 10%. It is a HARECXS theoretical profile when substituting for the B site. Since FIG. 6B substantially coincides with FIG. 6A, it was confirmed that the A site ion and the B site ion were mutually substituted in PMN-32PT.

  FIG. 5A shows the ALCHEMI-HARECXS profile of the PMN-32PT of the 130 system reflection train. FIG.5 (b) shows the theoretical value of the ALCHEMI-HARECXS profile of 130 system | strain reflective row | line | column.

FIG. 7A shows the ALCHEMI-HARECXS profile of the PMN-32PT of the 130 system reflection train. FIG. 7B is a HARECXS theoretical profile in the case where Mg ²⁺ and Pb ²⁺ of PMN-32PT in the 130 system reflection row are mutually replaced. FIG. 7C is a HARECXS theoretical profile in the case where Mg ²⁺ and Pb ²⁺ of PMN-32PT in the 130 system reflection row are mutually replaced.

  As shown in FIG. 7, it was confirmed that the A site ion and the B site ion were mutually substituted in the PMN-32PT in the 130-line reflection row as well.

As shown in FIG. 7C, about 45% (about 2 at%) of Mg ²⁺ (total amount of 4.32 at%) is transferred to the A site, and about 10% of the equivalent amount of Pb ²⁺ (total amount of 19.15 at%) ( About 2 at%) mutually replaces the B site, and the displacement amounts are Pb ²⁺ (A): u = 0.175Å, Pb ²⁺ (B): u = 0.15Å, Mg ²⁺ (A): u = 0, respectively. .15Å, Mg ²⁺ (B): u = 0.15Å, Nb ⁵⁺ (B): u = 0.1 ＝, Ti ⁴⁺ (B): u = 0.125Å, O ²⁻ (O): u = 0. A profile approximated to the experimental value of FIG.

On the other hand, the displacement amounts are Pb ²⁺ (A): u = 0.2 mm, Pb ²⁺ (B): u = 0.2 mm, Mg ²⁺ (A): u = 0.2 mm, Mg ²⁺ (B): u = When 0.4 場合, Nb ⁵⁺ (B): u = 0.4Å, Ti ⁴⁺ (B): u = 0.4Å, O ²⁻ (O): u = 0.2Å, FIG. 7 (b) As shown in FIG. 4, the relative intensity relationships of the ions do not match within the range of −1 <k / g111 <1 with the symmetrical excitation condition interposed therebetween. From this, it is clear that the amount of displacement of Nb ⁵⁺ and Ti ⁴⁺ seen from the 130 system row does not exceed the amount of displacement of Pb ²⁺ .

  With the above evaluation method, the internal structure of the crystalline thin film of perovskite oxide could be evaluated.

  As described above, the embodiments of the present invention have been described in detail. However, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. . Accordingly, all such modifications are intended to be included in the scope of the present invention.

The figure for demonstrating the crystal structure of a perovskite type oxide. The block diagram which shows the function structure of the crystal | crystallization evaluation apparatus concerning this Embodiment. The figure which shows the structure of the measurement part concerning this Embodiment. FIG. 4 (a) shows the ALCHEMI-HARECXS experimental profile of PMN-32PT with 111 system reflection rows. FIG. 4 (b) shows a HARECXS theoretical profile of PMN-32PT with 111 system reflection rows. FIG. 5 (a) shows the ALCHEMI-HARECXS experimental profile of PMN-32PT with 130 line reflectors. FIG. 5 (b) shows a HARECXS theoretical profile of PMN-32PT with a 130-line reflection train. FIG. 6 (a) shows the ALCHEMI-HARECXS experimental profile of PMN-32PT with 111 system reflection rows. FIG. 6 (b) shows the HARECXS theoretical profile of PMN-32PT of 111-line reflection train when A site ion and B site ion are mutually substituted. FIG. 7 (a) shows the ALCHEMI-HARECXS experimental profile of PMN-32PT with 130 line reflectors. FIG. 7 (b) shows a HARECXS theoretical profile of PMN-32PT with 130 system reflection rows. FIG. 7 (b) shows a HARECXS theoretical profile of PMN-32PT with 130 system reflection rows.

Explanation of symbols

12 Samples, 13 Optical members, 14 Detection units, 15 Detection units, 42 Display units, 44 Input units, 46 Measurement control units, 48 Storage units, 50 Processing units, 100 Crystal evaluation devices, 110 Measurement units

Claims (8)

(A) irradiating a sample containing crystals of a perovskite oxide placed on a sample stage with an electron beam;
(B) detecting characteristic X-rays generated from the sample;
(C) determining a type of an element located at a specific crystal site based on the detected characteristic X-ray intensity;
A crystal evaluation method comprising: In claim 1,
In the step (c), a crystal evaluation method for determining an amount of an element located at a specific crystal site. In claim 1 or 2,
In the step (c), a crystal evaluation method for determining a displacement of an element located at a specific crystal site. In any of claims 1 to 3,
In the step (a), an electron beam is irradiated from a plurality of incident angles,
In the step (b), a crystal evaluation method for detecting characteristic X-rays for each incident angle. In any of claims 1 to 4,
The perovskite-type oxide crystal has an A site, a B site, and an O site,
In the step (a), an electron beam is irradiated from an incident angle parallel to a straight line connecting the A site and the O site adjacent to the A site,
In the step (c), a crystal evaluation method in which the type, displacement or amount of an element located at the A site or the B site is determined. In any of claims 1 to 5,
The perovskite-type oxide crystal has an A site, a B site, and an O site,
In the step (a), an electron beam is irradiated from an incident angle parallel to a straight line connecting the A site and the B site adjacent to the A site,
In the step (c), a crystal evaluation method in which the type, displacement or amount of an element located at the A site or B site is determined. In any one of Claims 1 thru | or 6.
Before the step (a), further comprising obtaining orientation information indicating the orientation of crystals contained in the sample;
In the step (a), an electron beam is irradiated from an incident angle determined based on the orientation information. A measurement unit that irradiates a sample containing a perovskite-type oxide crystal placed on a sample stage with an electron beam and detects characteristic X-rays generated from the sample;
A processing unit that determines the type of an element located at a specific crystal site based on the intensity of the characteristic X-ray detected by the measurement unit;
A crystal evaluation apparatus.

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