Patent Application
20080001081
When bombardment ions impact on a sample surface to generate secondary ions in a time-of-flight secondary ion mass spectrometer, the impact ratio of the bombardment ions is influenced by the size of the bombardment ions and the density of a sample. Namely, when the size of bombardment ions is smaller than the density of the outermost surface of a sample, the impact ratio of bombardment ions on the outermost surface of the sample is decreased, and the impact ratio of bombardment ions entering the sample from the outermost surface thereof is increased. Conversely, when the size of bombardment ions is larger than the density of the outermost surface of a sample, the impact ratio of bombardment ions on the outermost surface of the sample is increased, and the impact ratio of bombardment ions entering the sample from the outermost surface thereof is decreased.
The impact ratio of bombardment ions primarily depends on the size of the bombardment ions and the density of a sample. However, the density of the surface of a sample generally tends to be lower than that of the inside of the sample, and in particular, the tendency of organic compounds and molecular compounds becomes significant. Therefore, mass spectra including information at different depths from the surface of the sample can be obtained by bombardment ions of different sizes.
Therefore, the analysis of a difference between mass spectra measured by bombardment of ions of different sizes permits the analysis of a composition profile in the depth direction from the surface of the sample.
Embodiments of the present invention will be described with reference to the drawings.
The time-of-flight secondary ion mass spectrometer shown in
The monomer ion bombardment function may include bombardment of monomers of at least two different elements. The cluster ion bombardment function may include bombardment of a plurality of types of cluster ions, such as dimer cluster ions and trimer cluster ions.
The information processing mechanism shown in
The time-of-flight secondary ion mass spectrometer shown in
As the monomer ions, at least one element selected from gold, bismuth, gallium, and indium is used. As the cluster ions, gold or bismuth can be used.
A sample is bombarded with ions in the descending order of ion sizes, and a mass spectrum of each type of ions is measured. As described below, in analysis of the present invention, an intensity difference between two spectra is taken into consideration, and thus the amount of the secondary ions detected is kept constant so that the total intensity of a spectrum is constant regardless of the type of primary ions. When ion bombardment is repeated several times to integrate the amount of the secondary ions measured, the amount of the secondary ions may be kept constant for a total number of times of ion bombardment.
The order of bombardment of primary ions may be reversed. When a sample is significantly damaged, the sample is protected by shifting the position of ion bombardment or reducing the bombardment time.
The resultant mass spectra of at least two types of primary ions of different ion sizes are transmitted to an information processing unit for data analysis on the basis of the bombardment ion sizes.
Specifically, a difference between the mass spectra obtained by bombardment of each ion is calculated. The term “difference between mass spectra” represents a difference between intensity data in each mass channel. When intensity data of a smaller-sized ion is subtracted from intensity data of a larger-sized ion, the difference is regarded as positive.
When three or more mass spectra are transmitted, the spectra are arranged in the descending order of ion sizes, and a difference between the adjacent spectra is calculated.
In higher-order data analysis, the composition of a sample may be estimated from the resultant mass spectra. The procedures thereof will be described.
In the ion source 2 shown in
Ions of a large size impact on the outermost surface of the sample, while ions of a small size impact into the outermost surface of the sample, impact molecules of the sample at a depth from the outermost surface, and emit the molecules. Therefore, the resultant mass spectra have the elements information of the sample nearer to the outermost surface of the sample, i.e., at a shallower depth of the sample, as the ion size increases.
With respect to a difference between each spectrum of different types of ions, positive intensity indicates molecules mostly distributed at a depth near the outermost surface, and negative intensity indicates molecules mostly distributed at a depth far the outermost surface. Molecules uniformly distributed regardless of depth disappear from a differential spectrum, and thus only molecules distributed depending on the depth can be clearly distinguished. This is an advantage of the differential spectrum.
By using the above-described analysis method, a composition distribution near a surface of a water-repellent material or a hydrophilic material is determined. The degree of water repellency or hydrophilicity can also be evaluated.
In addition to the constitution shown in
Like in
Procedures of analysis in the depth direction from a surface using the apparatus shown in
First, a surface of a test sample 1 is sputtered with fullerene ions from the fullerene ion sputtering mechanism 4. The surface of the sample 1 is sputtered by fullerene ions. The sputtering time is controlled to expose a surface of the sample at a desired depth.
Next, the sputtered surface of the test sample 1 is bombarded with cluster ions of gold or bismuth from the cluster ion bombardment mechanism 2, and a mass spectrum of secondary ions ionized at the outermost surface of the sample is measured.
Further, the ion source of the cluster ion bombardment mechanism 2 is changed, and the sputtered surface of the test sample 1 is bombarded with monomer ions of gold, bismuth, gallium, indium, or germanium. A mass spectrum of secondary ions ionized into the outermost surface of the sample is measured by the detector 3.
The order of ion bombardment of the sample surface may be reversed so that the surface is first bombarded with monomer ions and then bombarded with cluster ions. However, when the sample is significantly damaged, the ion bombardment position is shifted or the bombardment time is reduced.
After the completion of measurement, the resultant two or more mass spectra are subjected to data analysis on the basis of bombardment ion sizes in the information processor 6.
The data analysis on the basis of bombardment ion sizes can be performed on the basis of the fact that as the bombardment ion size increases, the mass number of secondary ions ionized increases and the bombardment ions less impact into the sample 1 from the outermost surface.
When the measurement surface of the sample 1 is composed of large molecules, the large molecules (with a high mass number) constituting the measurement surface of the sample 1 can be more sensitively detected by larger bombardment ions. In other words, a mass spectrum to be measured depends on the bombardment ion size. Therefore, consideration is given to variation in mass spectra according to the bombardment ion sizes so that the size of molecules constituting a surface can be analyzed.
The approach depth from a sample surface varies depending on the bombardment ion size, and when a mass spectrum varies depending on the bombardment ion size, it can be analyzed that a substance different from an internal substance forms a thin layer structure in a surface of the sample.
By using the above-described method of structural analysis of a measurement surface, it is possible to evaluate the degree of fullerene contamination in fullerene ion sputtering as shown in
The method of structural analysis in the depth direction by fullerene ion sputtering of the present invention is not limited to a data analysis method based on bombardment ion sizes as shown in examples which will be described below. Peaks in a spectrum may be differentiated or integrated or peculiar functional processing may be performed. The structural analysis is not limited to a specified arithmetic processing and analysis method as long as data analysis enables comparison between spectra measured by bombardment ions.
In the present invention, a sample 1 can be sputtered with fullerene ions while being cooled to analyze a structure in the depth direction.
In addition to the constitution shown in
The cooling mechanism 5 is adapted for cooling a measurement sample 1 by heat conduction from liquid nitrogen. The cooling temperature is preferably −100° C. or less, and the cooling atmosphere is preferably a vacuum atmosphere or an atmosphere at a low moisture pressure. When the cooling temperature is −100° C. or more, some liquid components or volatile components to be measured may move or evaporate during measurement. In a cooling atmosphere at a high moisture pressure, ice may adhere to the measurement sample due to dew condensation. Therefore, the cooling atmosphere is preferably a vacuum atmosphere or an atmosphere replaced by an inert gas such as nitrogen gas or argon gas.
A surface of the cooled measurement sample 1 is sputtered with fullerene ions from the fullerene ion sputtering mechanism 4 to expose a sputtered surface at a desired depth.
The sputtered surface of the measurement sample 1 is bombarded with cluster ions of gold or bismuth from the primary ion bombardment mechanism 2 to measure a mass spectrum of secondary ions ionized in the surface of the sample.
Further, the sputtered surface is bombarded with monomer ions of any one of gold, bismuth, gallium, indium, and germanium to measure a mass spectrum of secondary ions ionized in the surface of the sample.
The order of ion bombardment of the sputtered surface of the sample may be reversed so that the surface is first bombarded with monomer ions and then bombarded with cluster ions. However, when the sample is significantly damaged, the ion bombardment position can be shifted or the bombardment time can be reduced.
The resultant two or more mass spectra are subjected to data analysis on the basis of bombardment ion sizes in the information processing mechanism of the apparatus of structural analysis in the depth direction by fullerene ion sputtering of the present invention shown in
The surface analysis method and the surface measuring apparatus of the present invention will be described with reference to an example of application to a sample.
An aqueous solution of a styrene-acrylate copolymer having a surface-active function was adhered to an epoxy resin surface provided with water repellency by fluorocarbon treatment and then dried by nitrogen gas spraying to prepare a sample. The sample was measured and analyzed by time-of-flight secondary ion mass spectrometer TRIFT III manufactured by ULVAC-PHI. The type of primary ion bombardment was changed by replacing a filament of a primary ion gun (not shown) of the ion source 2 and changing an electric circuit of a primary ion bombardment control electrode (not shown). The acceleration voltage was 15 kV in Ga+ ion bombardment and 22 kV in Au+ ion bombardment and Au3+ ion bombardment.
First, a mass spectrum of secondary ions produced by Ga+ ion bombardment was measured, and next a mass spectrum of secondary ions produced by Au+ ion bombardment was measured. Finally, a mass spectrum of secondary ions produced by Au3+ ion bombardment was measured.
The obtained three mass spectra are shown in
Then, the following differential spectra were determined from the spectra shown in
(Spectrum of Au3+ ion bombardment)−(Spectrum of Au+ ion bombardment)
(Spectrum of Au+ ion bombardment)−(Spectrum of Ga+ ion bombardment)
The resultant differential spectra are shown in
Surface structural analysis by the spectra shown in
Among the spectral peaks detected in the spectra shown in
A differential spectrum of (Au3+ ion bombardment)−(Au+ ion bombardment) indicates that the peaks at Mass=78, 95, 103, 122, and 149 have high intensity on the side (plus side) above the 0 level.
Next, a differential spectrum of (Au+ ion bombardment)−(Ga+ ion bombardment) indicates that the peaks at Mass=95, 122, and 149 have high intensity on the side (plus side) above the 0 level, and the peaks at Mass=91 and 115 have high intensity on the side (minus side) below the 0 level.
Considering the above-mentioned results and the fact that primary bombardment ions less impact into the sample from the outermost surface as the size of the bombardment ions increases in the order of Ga+, Au+, and Au3+, it is analyzed that the acrylate moiety of the styrene-acrylate copolymer is mainly present in the outermost surface, and the styrene moiety of the styrene-acrylate copolymer is mainly present in the epoxy resin surface treated with fluorocarbon. Namely, it is analyzed that there is formed a molecular level layer structure (like an oriented structure) in which the styrene moiety of the styrene-acrylate copolymer adheres to the fluorocarbon-treated epoxy resin surface, and the acrylate moiety of the styrene-acrylate copolymer appears in the outermost surface.
When, in an example, analysis is performed by only a mass spectrum obtained by each of the primary ion bombardments, the analysis can lead to the *** analysis result. For example, most of the peaks resulting from the acrylate moiety of the styrene-acrylate copolymer are not detected in a spectrum obtained by Ga+ ion bombardment. This leads to the wrong analysis result that the acrylate moiety of the styrene-acrylate copolymer is absent from the surface.
Also, the peaks resulting from the styrene moiety of the styrene-acrylate copolymer and the peaks resulting from the acrylate moiety are mixed and detected only in a spectrum obtained by Au+ ion bombardment. This leads to the wrong analysis result that the styrene-acrylate copolymer is randomly present in the surface.
Further, most of the peaks resulting from the styrene moiety of the styrene-acrylate copolymer are not detected in a spectrum obtained by Au3+ ion bombardment. This may lead to the correct analysis result that the surface is covered with the acrylate moiety of the styrene-acrylate copolymer. However, the amount (layer thickness) of the acrylate moiety covering is unknown from the analysis result.
As described above, clear and accurate analysis results cannot be obtained by a mass spectrum measured by each of the primary ion bombardments.
An example of the method and apparatus for structural analysis in the depth direction by fullerene ion sputtering of the present invention will be described on the basis of
A silicon releasing agent was adhered to an epoxy resin surface provided with water repellency by fluorocarbon treatment to prepare a sample 1. The sample 1 was sputtered by fullerene ion sputtering apparatus 06-C60 (4) manufactured by ULVAC-PHI and then analyzed with respect to a structure in the depth direction by time-of-flight secondary ion mass spectrometer TRIFT III (3) manufactured by ULVAC-PHI. The type of primary ion bombardment was changed by replacing a filament of a primary ion gun (not shown) of the cluster ion source 2 and changing an electric circuit of a primary ion bombardment control electrode.
First, a mass spectrum of secondary ions produced by Ga+ ion bombardment was measured, and next a mass spectrum of secondary ions produced by Au+ ion bombardment was measured. Finally, a mass spectrum of secondary ions produced by Au3+ ion bombardment was measured.
The peak at Mass=91 assigned to an aromatic ring possibly resulting from a fullerene contamination was mainly detected in a surface layer of the sputtered surface of the sample. It was thus confirmed that the sputtered surface of the sample is contaminated by the fullerene.
Considering the fact that primary bombardment ions less impact into the sample from the outermost surface as the size of the irradiating ions increases in the order of Ga+, Au+, and Au3+, molecular structural analysis of the surface layer of the sputtered surface of the sample was performed on the basis of the fullerene ion irradiation time with attention to the peak at Mass=69 resulting from fluorocarbon and the peak at Mass=73 resulting from the silicon releasing agent. As a result, it was confirmed that the silicon releasing agent adhering to the surface of the sample is sputtered by fullerene ion to expose the fluorocarbon-treated surface on the sputtered surface without fracture.
The above-mentioned method and apparatus for structural analysis in the depth direction by fullerene ion sputtering permit analysis of a molecular structure in the depth direction of a molecular compound such as an organic compound or a silicon compound.
An example of structure analysis of a cooled sample in the depth direction by fullerene ion sputtering will be described with reference to
Luster paper printed by an ink jet printer was used as a measurement sample and analyzed with respect to the structure in the depth direction using time-of-flight secondary ion mass spectrometer TRIFT V nanoTOF manufactured by ULVAC-PHI.
First, a measurement chamber was replaced with nitrogen gas, and the measurement sample was cooled to −120° C. by a cooling stage 5 due to heat conduction of liquid nitrogen.
Then, the sample was bombarded with primary ions from the cluster ion bombardment mechanism 2 using a Ga ion gun and an Au ion gun as a primary ion gun, and mass spectra of the surface of the measurement sample were measured.
Then, the surface of the sample was sputtered by fullerene ions using a fullerene ion gun of the fullerene ion sputtering mechanism 4. The sputtered surface was further bombarded with primary ions using a Ga ion gun and an Au ion gun as a primary ion gun, and mass spectra were measured. This measurement cycle was repeated to analyze the structure of the measurement sample in the depth direction.
In one time of mass spectral measurement, the sample was bombarded with primary ions of different ion sizes as follows: First, a mass spectrum of secondary ions produced by Ga+ ion bombardment was measured, and next a mass spectrum of secondary ions produced by Au+ ion bombardment was measured. Finally, a mass spectrum of secondary ions produced by Au3+ ion bombardment was measured.
Peaks assigned to an aromatic ring possibly resulting from a fullerene contamination were mainly detected in a surface layer of the sputtered surface of the sample. It was thus confirmed that the sputtered surface of the sample is contaminated by the fullerene.
Considering the fact that primary bombardment ions less impact into the sample from the outermost surface as the size of the bombardment ions increases in the order of Ga+, Au+, and Au3+, molecular structural analysis of the measurement sample in the depth direction was performed by fullerene ion sputtering with attention to the peaks resulting from water used as an ink solvent for printing and the peaks resulting from an ink dye. As a result, it was confirmed that the ink solvent is three-dimensionally distributed around the ink dye in a print portion of the luster paper.
The above-mentioned method and apparatus for structural analysis of a cooled sample in the depth direction by fullerene ion sputtering permit analysis of a molecular structure in the depth direction of a molecular compound such as an organic compound, which contains a liquid component and a volatile component, or a silicon compound and analysis of a distribution of components.
The same measurement sample 1 as in Example 3 was cooled to −90° C. by the cooling stage 5 due to heat conduction of liquid nitrogen and measured by the same method as in Example 1.
As a result of analysis, the peaks resulting from water used as an ink solvent were not easily detected, and thus it was impossible to obtain the same data as in Example 3 that the ink solvent is three-dimensionally distributed around the ink dye in a print portion of the luster paper.
It was thus found from comparison to Example 3 that the cooling temperature of a sample is preferably −100° C. or less.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures and functions.
This application claims the benefit of Japanese Application No. 2006-179815 filed Jun. 29, 2006 and No. 2007-107173 filed Apr. 16, 2007, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-179815 | Jun 2006 | JP | national |
| 2007-107173 | Apr 2007 | JP | national |
