Sample plate for mass spectrometric analysis, mass spectrometric analysis method, and mass spectrometric analysis device
10332734 ยท 2019-06-25
Assignee
Inventors
Cpc classification
H01J49/164
ELECTRICITY
H01J49/0418
ELECTRICITY
International classification
H01J49/04
ELECTRICITY
G01N27/64
PHYSICS
G01N27/62
PHYSICS
Abstract
Provided is a sample plate for mass spectrometric analysis, which comprises a substrate and a metal thin film formed on the substrate. The metal thin film contains Ag, Al or Cu as the main component and further contains a specific additive element M.sub.Ag, M.sub.Al or M.sub.Cu depending on the element as the main component, in a ratio (M.sub.Ag/Ag) of the total number of atoms of the additive element M.sub.Ag to the number of atoms of Ag of from 0.001 to 0.5, a ratio (M.sub.Al/Al) of the total number of atoms of the additive element M.sub.Al to the number of atoms of Al of from 0.001 to 0.5, or a ratio (M.sub.Cu/Cu) of the total number of atoms of the additive element M.sub.Cu to the number of atoms of Cu of from 0.001 to 0.5.
Claims
1. A sample plate for mass spectrometric analysis, which comprises a substrate and a metal thin film formed on the substrate, wherein a surface of the metal thin film opposite to a substrate side is an outermost surface, wherein the metal thin film is selected from the group consisting of the following (A), (B), and (C): (A) a metal thin film containing Ag and at least one additive element M.sub.Ag selected from the group consisting of Pd, Au, Pt, Ir, Cu, Al, Zn, Sn, Ni, Cr, Co, Zr, Si, Ti, Sb, Ga, Nd, Ge and Bi, wherein a ratio M.sub.Ag/Ag of the total number of atoms of the additive element M.sub.Ag to the number of atoms of Ag in the metal thin film is from 0.001 to 0.5; (B) a metal thin film containing Al and at least one additive element M.sub.Al selected from the group consisting of Nd, Cu, Si, Mg, Cr, Mn, Zn, Fe, Ta, Ni, La, Ge, Ga, Ag, Au, Pd, Pt, Ir and Ti, wherein a ratio M.sub.Al/Al of the total number of atoms of the additive element M.sub.Al to the number of atoms of Al in the metal thin film is from 0.001 to 0.5; and (C) a metal thin film containing Cu and at least one additive element M.sub.Cu selected from the group consisting of Sn, Zn, Pb, Ni, Al, Fe, Mn, Au, Ti, Cr, Mg, Si, In, Ga, Se, Ca, Ag, Au, Pd, Pt, Ir and P, wherein a ratio M.sub.Cu/Cu of the total number of atoms of the additive element M.sub.Cu to the number of atoms of Cu in the metal thin film is from 0.001 to 0.5, wherein the metal thin film is deposited or sputtered and a thickness of the metal thin film is from 0.1 to 20 nm, and wherein the sample plate does not contain concave-convex structures, nanostructures, and microstructures formed on its surface.
2. The sample plate according to claim 1, wherein the sample plate comprises the metal thin film (A), wherein the metal thin film (A) comprises a number of oxygen (O) atoms, and wherein a ratio O/Ag of the number of 0 atoms to the number of Ag atoms in the metal thin film (A) is from 0 to 0.2.
3. The sample plate according to claim 2, wherein the ratio O/Ag of the number of O atoms to the number of Ag atoms in the metal thin film (A) is from 0.05 to 0.2.
4. The sample plate according to claim 1, wherein the sample plate comprises the metal thin film (A), and resistivity of the metal thin film (A) is at most 110.sup.4 .Math.cm.
5. The sample plate according to claim 1, wherein in an X-ray photoelectron spectrum of the surface of the metal thin film (A) obtained by X-ray photoelectron spectroscopy, integrated intensity of a peak observed at a binding energy position higher by from 2.5 to 5 eV than the position 368 eV of a peak derived from Ag3d.sub.5/2 photoelectrons, is higher than 0.001, wherein the integrated intensity of the peak derived from Ag3d.sub.5/2 photoelectrons is 1.
6. The sample plate according to claim 1, wherein the sample plate comprises the metal thin film (B), wherein the metal thin film (B) comprises a number of oxygen (O) atoms, and wherein a ratio O/Al of the number of O atoms to the number of Al atoms in the metal thin film (B) is from 0 to 1.5.
7. The sample plate according to claim 6, wherein the ratio O/Al of the number of O atoms to the number of Al atoms in the metal thin film (B) is from 0.5 to 1.5.
8. The sample plate according to claim 1, wherein the sample plate comprises the metal thin film (B), and resistivity of the metal thin film (B) is at most 110.sup.3 .Math.cm.
9. The sample plate according to claim 1, wherein in an X-ray photoelectron spectrum of the surface of the metal thin film (B) obtained by X-ray photoelectron spectroscopy, integrated intensity of a peak observed at a binding energy position higher by from 5 to 43 eV than the position 73 eV of a peak derived from Al2p.sub.3/2 photoelectrons, is higher than 0.01, where the integrated intensity of the peak derived from Al2p.sub.3/2 photoelectrons is 1.
10. The sample plate according to claim 1, wherein the sample plate comprises the metal thin film (C), wherein the metal thin film (C) comprises a number of oxygen (O) atoms, and wherein a ratio O/Cu of the number of O atoms to the number of Cu atoms in the metal thin film (C) is from 0 to 0.3.
11. The sample plate according to claim 10, wherein the ratio O/Cu of the number of O atoms to the number of Cu atoms in the metal thin film (C) is from 0.1 to 0.3.
12. The sample plate for mass spectrometric analysis according to claim 1, wherein the sample plate comprises the metal thin film (C), and resistivity of the metal thin film (C) is at most 110.sup.3 .Math.cm.
13. A mass spectrometric analysis method, comprising providing the sample plate of claim 1, placing a sample on the surface of the metal thin film of the sample plate, and conducting a mass spectrometric analysis.
14. A mass spectrometric analysis device, which is provided with the sample plate for mass spectrometric analysis as defined in claim 1.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DESCRIPTION OF EMBODIMENTS
(19) The following definitions of terms apply throughout the specification including Claims.
(20) A sample plate means a member on which a sample is to be placed in a mass spectrometric analysis device.
(21) Ag means Ag element unless otherwise specified, and is not limited to Ag metal simple substance. The same applies to other elements such as Al and Cu.
(22) <Sample Plate for Mass Spectrometric Analysis>
(23) The sample plate for mass spectrometric analysis of the present invention comprises a substrate and a metal thin film formed on the substrate.
(24)
(25) The visible light transmittance of the sample plate for mass spectrometric analysis of the present invention is preferably at least 50%, more preferably at least 70%, further preferably at least 80%. When the visible light transmittance of the sample plate for mass spectrometric analysis of the present invention is at least the lower limit value of the above range, observation with an optical microscope by backlight is possible. As a result, in IMS, both information on the form of a sample obtainable from optical images by an optical microscope and e.g. distribution of an analyte in the sample obtainable by mass spectrometric analysis can be utilized for analysis.
(26) (Substrate)
(27) As a material of the substrate, glass, a resin, a metal, a semiconductor or a ceramic may, for example, be mentioned.
(28) The substrate is preferably a transparent substrate with a view to increasing the visible light transmittance of the sample plate for mass spectrometric analysis, and is particularly preferably a substrate made of glass. A glass substrate having a transparent electrically conductive film formed thereon may also be used.
(29) The shape of the substrate is not particularly limited so long as a sample can be placed on it when the substrate is formed into a sample plate for mass spectrometric analysis.
(30) (Metal Thin Film)
(31) The metal thin film contains Ag, Al or Cu as the main component and further contains a specific additive element M.sub.Ag, M.sub.Al or M.sub.Cu depending upon the element as the main component. Hereinafter M.sub.Ag, M.sub.Al and M.sub.Cu will sometimes generally be referred to as M.
(32) Ag, Al and Cu, which have a high ultraviolet absorptance, are expected to efficiently absorb an ultraviolet laser employed in LDI-MS and efficiently vaporize sample molecules. Further, Ag, Al and Cu, which are metals capable of generating the surface plasmon, are expected to improve the efficiency of formation of cationized sample molecules by the effect of the surface plasmon excited on the surface of the metal thin film. That is, electrons are captured by the localized electric field formed by the surface plasmon, and the electron density increases in the vicinity of the surface of the metal thin film, whereby an improvement of the probability of collision between electrons and neutral particles (Ag, Al or Cu), thus an improvement in the efficiency of formation of cations (Ag.sup.+, Al.sup.+ or Cu.sup.+) and further an improvement in the efficiency of formation of the cationized sample molecules are expected.
(33) However, Ag, Al or Cu simple substance is reported to have a low ionization-assisting effect as compared with Pt or Au. For example, Non-Patent Document 2 reports that no ionization-assisting effect is confirmed on Ag nanoparticles and Cu nanoparticles.
(34) The present inventors have made extensive studies on reasons for this and as a result, found that Ag, Al or Cu simple substance is inferior in the moisture resistance and oxidation resistance, and its surface is thereby easily oxidized, and thus it has a low ionization-assisting effect.
(35) Accordingly, in the present invention, the environmental resistance such as the moisture resistance and the oxidation resistance of Ag, Al or Cu is improved by adding a specific additive element M to Ag, Al or Cu, depending on each element. By such addition, a high ultraviolet absorptance and the effect of the surface plasmon which Ag, Al or Cu intrinsically has, are sufficiently achieved. As a result, a metal thin film containing Ag, Al or Cu as the main component and further containing a specific additive element M depending on the element as the main component, can efficiently absorb an ultraviolet laser employed in LDI-MS and efficiently vaporize sample molecules, and further, can improve the efficiency of formation of cationized sample molecules by the effect of the surface plasmon excited on the surface of the metal thin film.
(36) Now, a first embodiment in which the main component of the metal thin film is Ag, a second embodiment in which the main component of the metal thin film is Al, and a third embodiment in which the main component of the metal thin film is Cu, will be described in detail.
First Embodiment
(37) According to a first embodiment of the present invention, the sample plate for mass spectrometric analysis comprises a metal thin film containing Ag as the main component. The metal thin film contains Ag and at least one additive element M.sub.Ag selected from the group consisting of Pd, Au, Pt, Ir, Cu, Al, Zn, Sn, Ni, Cr, Co, Zr, Si, Ti, Sb, Ga, Nd, Ge and Bi. The metal thin film according to the first embodiment may contain O (oxygen).
(38) In the first embodiment, the ratio (M.sub.Ag/Ag) of the total number of atoms of the additive element M.sub.Ag to the number of atoms of Ag in the metal thin film is from 0.001 to 0.5, preferably from 0.005 to 0.25, more preferably from 0.01 to 0.15. When M.sub.Ag/Ag is at most the upper limit value of the above range, the amount of Ag will be sufficient, and sample molecules can efficiently be vaporized and cationized. When M.sub.Ag/Ag is at least the lower limit value of the above range, the environmental resistance such as the moisture resistance and the oxidation resistance of Ag can be improved by the additive element M.sub.Ag. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Ag intrinsically has can be sufficiently achieved, and a sufficient ionization-assisting effect by the surface of the metal thin film can be achieved.
(39) In the first embodiment, the ratio (O/Ag) of the number of atoms of O (oxygen) to the number of atoms of Ag in the metal thin film is preferably from 0 to 0.2, more preferably from 0 to 0.1, further preferably from 0 to 0.05. When O/Ag is at most the upper limit value of the above range, oxidation of Ag is suppressed. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Ag intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(40) Whether Ag is in a metal state in the metal thin film in the first embodiment can be confirmed by a Ag3d photoelectron spectrum in an X-ray photoelectron spectrum of the surface of the metal thin film obtained by X-ray photoelectron spectroscopy. In a case where Ag is in a state of a metal not oxidized, a peak derived from Ag3d.sub.5/2 photoelectrons is observed at a position with a binding energy of 368 eV. In a case where Ag is oxidized, the peak derived from Ad3d.sub.5/2 photoelectrons shifts to the lower energy side by 0.3 eV (Ag.sub.2O) or 0.6 eV (AgO). I.sub.AlM/I.sub.AlO, where I.sub.AlM is the integrated intensity of a component derived from the metal, and I.sub.AlO is the integrated intensity of a component derived from the oxide, of the peak derived from Ag3d.sub.5/2 photoelectrons, is preferably from 0.5 to 1, more preferably from 0.8 to 1, further preferably from 0.9 to 1.
(41) The resistivity of the metal thin film in the first embodiment is preferably at most 110.sup.4 .Math.cm, more preferably at most 510.sup.5 .Math.cm, further preferably at most 110.sup.5 .Math.cm. The resistivity of the metal thin film being at most the upper limit value of the above range means that oxidation of Ag is suppressed. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Ag intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(42) Whether the metal thin film in the first embodiment achieves the effect of the surface plasmon can be confirmed by an X-ray photoelectron spectrum of the surface of the metal thin film obtained by X-ray photoelectron spectroscopy.
(43) In a case where the metal thin film in the first embodiment achieves the effect of the surface plasmon, a peak is observed (hereinafter this peak will be referred to as Ag3d.sub.5/2PL) at a binding energy position higher by from 2.5 to 5 eV than the position of a peak derived from Ag3d.sub.5/2 photoelectrons. Ag3d.sub.5/2PL is considered to be a peak derived from Ag3d.sub.5/2 photoelectrons the energy of which is lost by the Ag surface plasmon (surface plasmon loss peak), from the following document.
(44) Non-Patent Document 3: Y. Tachibana, et al., Thin Solid Films 2003, vol. 442, p. 212-216
(45) A higher peak integrated intensity of Ag3d.sub.5/2PL indicates a higher effect of the surface plasmon. Accordingly, the peak integrated intensity of Ag3d.sub.5/2PL is preferably higher than 0.001, more preferably higher than 0.005, further preferably higher than 0.01, where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons is 1.
(46) The thickness of the metal thin film in the first embodiment is preferably from 0.1 to 20 nm, more preferably from 1 to 12 nm, further preferably from 5 to 7 nm. When the thickness of the metal thin film is at least the above lower limit value, the amount of Ag will be sufficient, and the cationized sample molecules can efficiently be formed. When the thickness of the metal thin film is at most the above upper limit value, the visible light transmittance of the sample plate for mass spectrometric analysis can be increased.
(47) The above metal thin film according to the first embodiment corresponds to the metal thin film (A) in Claims of this application.
Second Embodiment
(48) According to a second embodiment of the present invention, the sample plate for mass spectrometric analysis comprises a metal thin film containing Al as the main component. The metal thin film contains Al, and at least one additive element M.sub.Al selected from the group consisting of Nd, Cu, Si, Mg, Cr, Mn, Zn, Fe, Ta, Ni, La, Ge, Ga, Ag, Au, Pd, Pt, Ir and Ti. The metal thin film according to the second embodiment may contain O (oxygen).
(49) In the second embodiment, the ratio (M.sub.Al/Al) of the total number of atoms of the additive element M.sub.Al to the number of atoms of Al in the metal thin film is from 0.001 to 0.5, preferably from 0.005 to 0.25, more preferably from 0.01 to 0.15. When M.sub.Al/Al is at most the upper limit value of the above range, the amount of Al will be sufficient, and sample molecules can efficiently be vaporized and cationized. When M.sub.Al/Al is at least the lower limit value of the above range, the environmental resistance such as the moisture resistance and the oxidation resistance of Al can be improved by the additive element M.sub.Al. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Al intrinsically has can be sufficiently achieved, and a sufficient ionization-assisting effect by the surface of the metal thin film can be achieved.
(50) In the second embodiment, the ratio (O/Al) of the number of atoms of O (oxygen) to the number of atoms of Al in the metal thin film is preferably from 0 to 1.5, more preferably from 0 to 1, further preferably from 0 to 0.5.
(51) The chemical bonding state of Al in the metal thin film in the second embodiment can be confirmed by an Al2p photoelectron spectrum in an X-ray photoelectron spectrum of the surface of the metal thin film obtained by X-ray photoelectron spectroscopy. In a case where Al is in a state of a metal not oxidized, a peak derived from Al2p.sub.3/2 photoelectrons is observed at a position with a binding energy of 73 eV. In a case where Al is oxidized, the peak derived from Al2p.sub.3/2 photoelectrons shifts to the higher energy side by about 3 eV. Since Al is a material which is easily oxidized, its outermost surface is oxidized by the time a film formed in vacuum is taken out to the air. Accordingly, even with an Al film having a low resistivity, both peak of a component derived from the metal and peak of a component derived from the oxide are observed as a peak derived from Al2p.sub.3/2 photoelectrons in many cases. I.sub.AlM/I.sub.AlO, where I.sub.AlM is the integrated intensity of a component derived from the metal, and I.sub.AlO is the integrated intensity of a component derived from the oxide, of the peak derived from Al2p.sub.3/2 photoelectrons, is preferably from 0.1 to 1, more preferably from 0.3 to 1, further preferably from 0.5 to 1.
(52) When O/Al is at most the upper limit value of the above range and I.sub.AlM/I.sub.AlO is at least the lower limit value of the above range, Al which is not oxidized is present in the vicinity of the surface. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Al intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(53) The resistivity of the metal thin film in the second embodiment is preferably at most 110.sup.3 .Math.cm, more preferably at most 510.sup.5 .Math.cm, further preferably at most 110.sup.5 .Math.cm. The resistivity of the metal thin film being at most the upper limit value of the above range means that oxidation of Al is suppressed. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Al intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(54) Whether the metal thin film in the second embodiment achieves the effect of the surface plasmon can be confirmed by an X-ray photoelectron spectrum of the surface of the metal thin film obtained by X-ray photoelectron spectroscopy.
(55) In a case where the metal thin film in the second embodiment achieves the effect of the surface plasmon, a plasmon loss peak is observed (hereinafter this peak will be referred to as Al2p.sub.3/2PL) at a binding energy position higher by from 5 to 43 eV than the position of a peak derived from Al2p.sub.3/2 photoelectrons.
(56) A higher peak integrated intensity of Al2p.sub.3/2PL indicates a higher effect of the surface plasmon. Accordingly, the peak integrated intensity of Al2p.sub.3/2PL is preferably higher than 0.01, more preferably higher than 0.05, further preferably higher than 0.1, where the integrated intensity of a peak derived from Al2p.sub.3/2 photoelectrons is 1.
(57) The thickness of the metal thin film in the second embodiment is preferably from 1 to 20 nm, more preferably from 5 to 12 nm, further preferably from 5 to 7 nm. When the thickness of the metal thin film is at least the above lower limit value, the amount of Al will be sufficient, and the sample molecules can efficiently be cationized. When the thickness of the metal thin film is at most the above upper limit value, the visible light transmittance of the sample plate for mass spectrometric analysis can be increased.
(58) The above metal thin film according to the second embodiment corresponds to the metal thin film (B) in Claims of this application.
Third Embodiment
(59) According to a third embodiment of the present invention, the sample plate for mass spectrometric analysis comprises a metal thin film containing Cu as the main component. The metal thin film contains Cu and at least one additive element M.sub.Cu selected from the group consisting of Sn, Zn, Pb, Ni, Al, Fe, Mn, Au, Ti, Cr, Mg, Si, In, Ga, Se, Ca, Ag, Au, Pd, Pt, Ir and P. The metal thin film according to the third embodiment may contain O (oxygen).
(60) In the third embodiment, the ratio (M.sub.Cu/Cu) of the total number of atoms of the additive element M.sub.Cu to the number of atoms of Cu in the metal thin film is from 0.001 to 0.5, preferably from 0.005 to 0.25, more preferably from 0.01 to 0.15. When M.sub.Cu/Cu is at most the upper limit value of the above range, the amount of Cu will be sufficient, and sample molecules can efficiently be vaporized and cationized. When M.sub.Cu/Cu is at least the lower limit value of the above range, the environmental resistance such as the moisture resistance and the oxidation resistance of Cu can be improved by the additive element M.sub.Cu. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Cu intrinsically has can be sufficiently achieved, and a sufficient ionization-assisting effect by the surface of the metal thin film can be achieved.
(61) In the third embodiment, the ratio (O/Cu) of the number of atoms of O (oxygen) to the number of atoms of Cu in the metal thin film is preferably from 0 to 0.3, more preferably from 0 to 0.2, further preferably from 0 to 0.1. When the ratio of O is at most the upper limit value of the above range, oxidation of Cu is suppressed. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Cu intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(62) The resistivity of the metal thin film in the third embodiment is preferably at most 110.sup.3 .Math.cm, more preferably at most 510.sup.5 .Math.cm, further preferably at most 110.sup.5 .Math.cm. The resistivity of the metal thin film being at most the upper limit value of the above range means that oxidation of Cu is suppressed. Accordingly, a high ultraviolet absorptance and the effect of the surface plasmon which Cu intrinsically has can further be achieved, and a higher ionization-assisting effect by the surface of the metal thin film can be achieved.
(63) The thickness of the metal thin film in the third embodiment is preferably from 1 to 20 nm, more preferably from 5 to 12 nm, further preferably from 5 to 7 nm. When the thickness of the metal thin film is at least the above lower limit value, the amount of Cu will be sufficient, and the sample molecules can more efficiently be cationized. When the thickness of the metal thin film is at most the above upper limit value, the visible light transmittance of the sample plate for mass spectrometric analysis can be increased.
(64) The above metal thin film according to the third embodiment corresponds to the metal thin film (C) in Claims of this application.
(65) (Method for Producing Sample Plate for Mass Spectrometric Analysis)
(66) The sample plate for mass spectrometric analysis of the present invention is produced by forming a metal thin film on a substrate by a known film-forming method.
(67) The film-forming method may, for example, be a physical deposition method (such as a sputtering method or a vacuum deposition method), and with a view to suppressing the amount of oxygen included in the metal thin film, it is preferably a physical deposition method, particularly preferably a sputtering method.
(68) In a case where a metal thin film is formed by a physical deposition method, it is preferred to sufficiently remove residual gases in a vacuum chamber before film forming, from the following reasons.
(69) As a vacuum chamber is evacuated with a vacuum pump, N.sub.2 and O.sub.2 which are major components in the air are removed, and the major residual gas in the vacuum chamber is H.sub.2O. O and OH derived from the residual gas component are included in the metal thin film, and their amount depends on the amount of the residual gas in the vacuum chamber, that is, the degree of vacuum. For example, in a case where the ultimate vacuum degree in the vacuum chamber is 110.sup.1 Pa, the proportion of O in the metal thin film tends to be higher, and the resistivity tends to be higher.
(70) In a case where the metal thin film is prepared by a sputtering method, it is preferred that the ultimate vacuum degree in the vacuum chamber is adjusted to be at most 510.sup.4 Pa, and then high purity Ar gas (purity of 99.99% or higher) is introduced to adjust the degree of vacuum to 110.sup.1 to 1 Pa, and a target metal material is sputtered by Ar.sup.+. In such a manner, a metal thin film having a low proportion of O and having electrical conductivity close to that of a bulk material can be formed.
(71) (Mechanism of Action)
(72) The above-described sample plate for mass spectrometric analysis of the present invention comprises a substrate and a metal thin film formed on the substrate, wherein the metal thin film contains Ag, Al or Cu as the main component and contains a specific additive element M depending on the element as the main component in a specific ratio, and accordingly the environmental resistance such as the moisture resistance and the oxidation resistance of Ag, Al or Cu is improved. Accordingly, the metal thin film can efficiently absorb an ultraviolet laser employed in LDI-MS and can efficiently vaporize sample molecules. Accordingly, use of a matrix in combination is not necessary.
(73) Further, since the environmental resistance such as the moisture resistance and the oxidation resistance of Ag, Al or Cu is improved, the ionization-assisting effect will hardly decrease with the lapse of time.
(74) Further, since the environmental resistance such as the moisture resistance and the oxidation resistance of Ag, Al or Cu is improved, the effect of the surface plasmon excited on the surface of the metal thin film will sufficiently be achieved, and the efficiency of formation of cations will improve, and thus the efficiency of formation of cationized sample molecules will improve. Accordingly, a high efficiency of formation of cationized sample molecules will be achieved even without using a cationizing agent in combination.
(75) In the sample plate having a metal thin film formed on its surface, the in-plane dispersion of the ionization-assisting effect tends to be small as compared with a sample plate having metal nanoparticles supported.
(76) Further, a sample plate having a metal thin film formed on a substrate can easily be produced as compared with a sample plate having fine concave-convex structures formed on the surface of a substrate and a sample plate having metal nanostructures provided on the surface of a substrate.
Other Embodiment
(77) The sample plate for mass spectrometric analysis of the present invention is not limited to the sample plate for mass spectrometric analysis shown in the drawing so long as it comprises a substrate and a metal thin film formed on the substrate, and the metal thin film contains Ag, Al or Cu as the main component and contains a specific additive element M depending on the element as the main component in a specific ratio. For example, it may have a layer containing a sample formed between the substrate and the metal thin film.
(78) <Mass Spectrometric Analysis Method and Mass Spectrometric Analysis Device>
(79) The mass spectrometric analysis method of the present invention is a method which uses the sample plate for mass spectrometric analysis of the present invention.
(80) The mass spectrometric analysis device of the present invention is a device which is provide with the sample plate for mass spectrometric analysis of the present invention.
(81) The sample plate for mass spectrometric analysis of the present invention is suitable for LDI-MS among the mass spectrometric analysis methods.
(82) LDI-MS may, for example, be LDI-time-of-flight mass spectrometry (LDI-TOFMS), LDI-ion-trap MS, LDI-fourier transform MS, LDI-quadruple time-of-flight MS or time-of-flight connected MS, and is preferably LDI-TOFMS. For such analysis methods, a means known in SALDI-MS may be employed.
(83) The mass spectrometric analysis device used for LDI-TOFMS may, for example, be one comprising a vacuum chamber, a sample plate placed in a vacuum chamber, a support table to support the sample plate, a light irradiation part to irradiate the sample plate with a ultraviolet laser, a flying direction controlling part to make cationized sample molecules desorbed from the sample on the sample plate fly toward a detector, and a detector.
(84) (Mechanism of Action)
(85) According to the above-described mass spectrometric analysis method and mass spectrometric analysis device of the present invention, which use the sample plate for mass spectrometric analysis of the present invention of which the ionization-assisting effect will hardly decrease with the lapse of time, and the efficiency of formation of cationized sample molecules is good without using a cationizing agent in combination, peaks derived from the sample can sufficiently be detected in a mass spectrum. Further, since the sample plate for mass spectrometric analysis of the present invention which requires no use of a matrix in combination, is used, peaks derived from the sample can easily be distinguished in a mass spectrum. Further, since the sample plate for mass spectrometric analysis of the present invention of which in-plane dispersion of the ionization-assisting effect is small, is used, an accurate distribution or the like of an analyte can be obtained by IMS.
EXAMPLES
(86) Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to the following specific description.
(87) Ex. 1, 3, 4, 6 to 16 and 18 to 24 are Examples of the present invention, and Ex. 2, 5 and 17 are Reference Examples.
(88) (Thickness)
(89) The thickness of the metal thin film was measured by a surface profiler (manufactured by ULVAC, Inc., Dektak6M). At the time of forming the metal thin film, the substrate transport rate was adjusted to obtain a metal thin film having a desired thickness.
(90) (Elemental Analysis)
(91) The ratio of the total number of atoms of the additive elements to the number of atoms of the element as the main component on the surface of the metal thin film was calculated from the outermost surface composition measured by an X-ray photoelectron spectroscopy (manufactured by ULVAC-PHI, INCORPORATED, Quantera SXM). The ratio of the number of atoms of O (oxygen) to the number of atoms of the element as the main component was calculated from compositional analysis results at a point where no C1s peak was detected after surface organic contamination adsorbed on the outermost surface of the sample was removed by low acceleration Ar.sup.+ ion beam sputtering in the X-ray photoelectron spectroscopy under the following conditions.
(92) Ar.sup.+ Ion beam accelerating voltage: 500 V
(93) Ar.sup.+ Ion beam scanning region: 2 mm2 mm
(94) Ar.sup.+ Sputtering time: 1 to 1.5 minutes
(95) (Resistivity)
(96) The resistivity of the metal thin film was obtained by multiplying the sheet resistivity of the metal thin film by the thickness of the metal thin film. The sheet resistance of the metal thin film was measured by the four-point probe method using a resistivity meter (manufactured by Mitsubishi Petrochemical, Loresta FP MCP-Tester).
(97) (Visible Light Transmittance)
(98) The visible light transmittance of the sample plate for mass spectrometric analysis was measured by a luminous transmittance meter (manufactured by Asahi Spectra Co., Ltd., Model 304).
(99) (Measurement of Surface Plasmon)
(100) The X-ray photoelectron spectrum of the surface of the metal thin film was measured by an X-ray photoelectron spectroscopy (manufactured by ULVAC-PHI, INCORPORATED, Quantera SXM).
(101) In a case where the main component of the metal thin film was Ag, the integrated intensity of a peak (Ag3d.sub.5/2PL) observed at a binding energy position higher by from 2.5 to 5 eV than a peak derived from Ag3d.sub.5/2 photoelectrons, where the integrated intensity of the peak derived from Ag3d.sub.5/2 photoelectrons was 1, was obtained.
(102) (Mass Spectrometric Analysis)
(103) As a mass spectrometric analysis device, a laser desorption/ionization time-of-flight mass spectrometer (manufactured by JEOL Ltd., JMS-S3000) was used.
(104) The sample plate for mass spectrometric analysis provided with a sample, prepared in each Ex., was set in an engraved portion of a SUS target plate attached to the mass spectrometer. The target plate was placed in a vacuum chamber of the mass spectrometer, and mass spectrometric analysis was performed under the following conditions.
(105) Irradiation light: Nd: YLF laser, wavelength: 349 nm (frequency: 1 kHz)
(106) Radius of irradiation area: about 20 m
(107) Accelerating voltage: 20 kV
(108) Measurement ion mode: positive ion mode
(109) Delay Time: 300 nsec and 150 nsec
(110) Grid voltage: 3 kV
(111) (Substrate)
(112) As the substrate, a glass plate (manufactured by Asahi Glass Company, Limited, alkali-free glass, 15 mm20 mm0.5 mm in thickness) and a polyethylene terephthalate (hereinafter referred to as PET) film (manufactured by TOYOBO CO., LTD., A4300, 50 mm50 mm0.07 mm in thickness) were prepared.
(113) (Sample)
(114) Polyethylene glycol (PEG600) was dissolved in tetrahydrofuran to prepare a 1 mass % sample solution (1). Polyethylene glycol (PEG2000) was dissolved in tetrahydrofuran to prepare a 1 mass % sample solution (2). Further, Tinuvin (registered trademark) 292 (a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate) was dissolved in tetrahydrofuran to prepare a 1 mass % sample solution (3).
Ex. 1
(115) A glass plate was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by BOC Industrial Gases, ILS-1600). The degree of vacuum in the vacuum chamber was adjusted to at most 1.310.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 14 nm) was formed on the surface of the glass plate by using an Ag target (432 mm127 mm) containing 5 atomic % of Au, using an Ar gas as a sputtering gas and applying an electric power of 0.6 kw, to prepare a sample plate for mass spectrometric analysis. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance, and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 1.
(116) 2 L of the sample solution (1) was dropped on the surface of the metal thin film and dried to prepare a sample plate for mass spectrometric analysis provided with a sample, and mass spectrometric analysis was carried out. In this Ex., no matrix agent nor cationizing agent was used. The mass spectrum obtained by mass spectrometric analysis is shown in
Ex. 2
(117) The X-ray photoelectron spectrum of the surface of a metal thin film on a sample plate for mass spectrometric analysis prepared in the same manner as in Ex. 1 is shown in
Ex. 3
(118) A glass plate was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by Nisshin Seiki, JVS-S03). The degree of vacuum in the vacuum chamber was adjusted to at most 810.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 10 nm) was formed on the surface of the glass plate by using an Ag target (200 mm70 mm) containing 1 atomic % of Bi and 0.2 atomic % of Nd, using an Ar gas as a sputtering gas and applying an electric power of 0.2 kw to prepare a sample plate for mass spectrometric analysis. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 1.
(119) Mass spectrometric analysis was carried out in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 3 was used. In the same manner as in Ex. 1, peaks derived from Ag.sup.+-adduct sample molecules were observed at m/z of from 350 to 1,050. The mass spectrum at m/z of from 460 to 1,050 is shown in
Ex. 4
(120) A sample plate for mass spectrometric analysis was obtained in the same manner as in Ex. 3 except that the target as identified in Table 1 was used. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance, and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 1. Mass spectrometric analysis was performed in the same manner as in Ex. 1 and 3 except that the sample plate for mass spectrometric analysis in Ex. 4 was used. In the same manner as in Ex. 1 and 3, peaks derived from Ag.sup.+-adduct sample molecules were observed at m/z of from 350 to 1,050. The mass spectrum at m/z of from 460 to 1,050 is shown in
Ex. 5
(121) An ITO film (thickness: 300 nm, sheet resistance: 8.0 /sq.) was formed on the surface of a glass plate in the same manner as in Ex. 1 except that an ITO (In.sub.2O.sub.3/SnO.sub.2: 95 wt %/5 wt %) target was used, a mixed gas of Ar and O.sub.2 (O.sub.2/Ar volume ratio=5/95) was used as a sputtering gas, and an electric power of 2 kw was applied, to prepare a sample plate for mass spectrometric analysis. Mass spectrometric analysis was performed in the same manner as in Ex. 1, 3 and 4 except that the sample plate for mass spectrometric analysis in Ex. 5 was used, however, no mass spectrum derived from sample molecules (at the intervals, m/z 44) was observed at m/z of from 350 to 1,050 (see
(122) TABLE-US-00001 TABLE 1 Ex. 1 Ex. 3 Ex. 4 Target Main Ag Ag Ag component Additive Au Bi, Nd Bi, Nd, Ge element Ratio of 5 atomic Bi: 1 atomic % Bi: 1 atomic % additive % Nd: 0.2 Nd: 0.2 atomic % element atomic % Ge: 1 atomic % Metal thin M.sub.Ag/Ag 0.04 Bi/Ag: 0.01 Bi/Ag: 0.01 film Nd/Ag: 0.002 Nd/Ag: 0.002 Ge/Ag: 0.01 O/Ag n.d. 0.08 0.09 Thickness of metal 14 10 8 thin film (nm) Sheet resistance of metal 6.4 9.6 16.4 thin film (/sq.) Resistivity of metal thin 9.0 10.sup.6 9.6 10.sup.6 1.3 10.sup.5 film ( .Math. cm) Visible light 53 61 68 transmittance of sample plate (%) Peak intensity of 0.07 0.06 0.05 Ag3d.sub.5/2PL
Ex. 6
(123) A sample plate for mass spectrometric analysis was obtained in the same manner as in Ex. 1 except that the target as identified in Table 2 was used. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 2. Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 6 and the sample solution (2) were used. Peaks derived from Ag.sup.+-adduct sample molecules are observed at m/z of from 1,600 to 2,700 at the intervals, m/z 44 (derived from CH.sub.2CH.sub.2O) (see
(124) M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance, and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, of the sample in Ex. 6, are shown in Table 2.
Ex. 7
(125) For reference, on the SUS target plate attached to the mass spectrometer, the sample solution (2) was directly dropped and dried, and further CHCA as a matrix agent and NaI as a cationizing agent were dropped and dried, and then mass spectrometric analysis was performed. The obtained mass spectrum is shown in
Ex. 8
(126) A PET film was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by Nisshin Seiki, JVS-S03). The degree of vacuum in the vacuum chamber was adjusted to at most 810.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 13 nm) was formed on the surface of the PET film by using an Ag target (200 mm70 mm) containing 1 atomic % of Cu, using an Ar gas as a sputtering gas and applying an electric power of 0.2 kw to prepare a sample plate for mass spectrometric analysis. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 2.
(127) Mass spectrometric analysis was carried out in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 8 and the sample solution (2) were used. The mass spectrum in Ex. 8 obtained by mass spectrometric analysis is shown in
Ex. 9 to Ex. 14
(128) A sample plate for mass spectrometric analysis in each of Ex. 9 to 14 was obtained in the same manner as in Ex. 3 except that the target as identified in Table 2 or 3 was used. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity, the visible light transmittance and the integrated intensity of a peak of Ag3d.sub.5/2PL where the integrated intensity of a peak derived from Ag3d.sub.5/2 photoelectrons was 1, are shown in Table 2 or 3.
(129) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in each of Ex. 9 to 14 and the sample solution (2) were used. The mass spectra in Ex. 9 to 14 obtained by mass spectrometric analysis are shown in
Ex. 15
(130) A PET film was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by BOC Industrial Gases, ILS-1600). The degree of vacuum in the vacuum chamber was adjusted to at most 1.310.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 20 nm) was formed on the surface of the PET film by using an Al target (432 mm127 mm) comprising an AlMgSi alloy (alloy No.: A6061), using an Ar gas as a sputtering gas and applying an electric power of 1 kw, to prepare a sample plate for mass spectrometric analysis. M.sub.Al/Al, O/Al, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 4.
(131) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 15 and the sample solution (2) were used. The mass spectrum of Ex. 15 obtained by mass spectrometric analysis is shown in
Ex. 16
(132) A PET film was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by Nisshin Seiki, JVS-503). The degree of vacuum in the vacuum chamber was adjusted to at most 810.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 11 nm) was formed on the surface of the PET film by using a Cu target (200 mm70 mm) comprising a Cu alloy with a ratio of the number of atoms of P to the number of atoms of Cu (P/Cu) of 0.001, using an Ar gas as a sputtering gas and applying an electric power of 0.2 kw to prepare a sample plate for mass spectrometric analysis. M.sub.Cu/Cu (P/Cu in this Ex.), O/Cu, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 4.
(133) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 16 and the sample solution (2) were used. The mass spectrum in Ex. 16 obtained by mass spectrometric analysis is shown in
Ex. 17
(134) A glass plate was placed in a vacuum chamber of a magnetron sputtering apparatus (manufactured by Nisshin Seiki, JVS-S03), the degree of vacuum in the vacuum chamber was adjusted to at most 810.sup.4 Pa, and high purity Ar gas (purity: 99.99 vol %) was introduced to adjust the degree of vacuum to 210.sup.1 Pa. A metal thin film (thickness: 10 nm) was formed on the surface of the glass plate by using a Ag target (200 mm70 mm) with purity of 4N, using an Ar gas as a sputtering gas and applying an electric power of 0.2 kw to prepare a Ag metal thin film-provided glass substrate, which was left in the air for one year, to prepare a sample plate for mass spectrometric analysis. Peaks derived from Ag3d.sub.5/2 photoelectrons of the surface of the sample plate by X-ray photoelectron spectroscopy are shown in
(135) TABLE-US-00002 TABLE 2 Ex. 6 Ex. 8 Ex. 9 Ex. 10 Target Main Ag Ag Ag Ag component Additive Au Cu Zr Sn element Ratio of 5 1 0.85 5.5 mass % additive atomic % atomic % mass % element Metal M.sub.Ag/Ag 0.04 0.03 0.09 0.22 thin O/Ag n.d. n.d. 0.16 0.06 film Thickness of metal 7 13 15 11 thin film (nm) Sheet resistance 12.4 5.3 6.1 15.2 of metal thin film (/sq.) Resistivity of metal 8.7 10.sup.6 6.9 10.sup.6 9.1 10.sup.6 1.6 10.sup.5 thin film ( .Math. cm) Visible light 68 50 51 51 transmittance of sample plate (%) Peak intensity of 0.07 0.05 0.04 0.06 Ag3d.sub.5/2PL
(136) TABLE-US-00003 TABLE 3 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Target Main Ag Ag Ag Ag component Additive Cr Ti Co Pd element Ratio of 0.49 0.45 0.55 10 additive mass % mass % mass % mass % element Metal thin M.sub.Ag/Ag 0.02 0.04 0.08 film O/Ag 0.03 0.05 n.d. Thickness of metal 13 13 15 9 thin film (nm) Sheet resistance of 4.6 5.8 7.4 18 metal thin film (/sq.) Resistivity of metal 6.0 10.sup.6 7.5 10.sup.6 1.1 10.sup.5 1.6 10.sup.5 thin film ( .Math. cm) Visible light 49 51 52 49 transmittance of sample plate (%) Peak intensity of 0.07 0.08 0.07 0.06 Ag3d.sub.5/2PL
(137) TABLE-US-00004 TABLE 4 Ex. 15 Ex. 16 Target Type AlMgSi alloy (A6061) Cu alloy Additive element Mg: 0.8-1.2% P/Cu: 0.001 and its ratio Si: 0.4-0.8% Cu: 0.15-4.0% Cr: 0.04-0.35% Metal thin M.sub.Al/Al, M.sub.Cu/Cu Mg/Al: 0.07 P/Cu: n.d. film O/Al, O/Cu 1.48 0.08 Thickness of metal 20 11 thin film (nm) Sheet resistance of metal 7.6 21.8 thin film (/sq.) Resistivity of metal thin 1.5 10.sup.5 2.4 10.sup.5 film ( .Math. cm) Visible light transmittance 7 53 of sample plate (%)
(138) In Table 4, 1.48 in the row of the metal thin film in Ex. 15 represents the O/Al value, and 0.08 in the row of the metal thin film in Ex. 16 represents the O/Cu value.
(139) In Tables 1 to 4, n.d. represents the detection lower limit or lower in X-ray photoelectron spectroscopy. With respect to a trace amount of Cr in the metal thin film in Ex. 11, the composition cannot be calculated since the binding energy positions of Cr2p and Ag3p.sub.3/2 as main peaks overlap with each other, and the value of M.sub.Ag/Ag is represented as -. In Table 3, with respect to a trace amount of O in the metal thin film in Ex. 14, the composition cannot be calculated since the binding energy positions of O1s and Pd3p.sub.3/2 as main peaks overlap with each other, and the value of O/Ag is represented as -. In Table 4, the amounts of Si, Cu and Cr in the metal thin film in Ex. 15 are at most the detection lower limit in X-ray photoelectron spectroscopy, and only the Mg/Al value is shown.
Ex. 18, 19 and 22
(140) In Ex. 18, 19 and 22, the same sample plates for mass spectrometric analysis as in Ex. 6, 14 and 12, respectively, were prepared. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 5.
(141) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample solution (3) was used. The mass spectra in Ex. 18, 19 and 22 obtained by mass spectrometric analysis are shown in
Ex. 20 and 21
(142) Sample plates for mass spectrometric analysis in Ex. 20 and 21 were obtained in the same manner as in Ex. 3 except that the target shown in Table 5 was used. M.sub.Ag/Ag, O/Ag, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 5.
(143) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in each of Ex. 20 and 21 and the sample solution (3) were used. The mass spectra of Ex. 20 and 21 obtained by mass spectrometric analysis are shown in
Ex. 23
(144) The same sample plate for mass spectrometric analysis as in Ex. 15 was prepared. M.sub.Al/Al, O/Al, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 6.
(145) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 23 and the sample solution (3) were used. The mass spectrum in Ex. 23 obtained by mass spectrometric analysis is shown in
Ex. 24
(146) The same sample plate for mass spectrometric analysis as in Ex. 16 was prepared. M.sub.Cu/Cu (P/Cu in this Ex.), O/Cu, the thickness of the metal thin film, the sheet resistance, the resistivity and the visible light transmittance are shown in Table 6.
(147) Mass spectrometric analysis was performed in the same manner as in Ex. 1 except that the sample plate for mass spectrometric analysis in Ex. 24 and the sample solution (3) were used. The mass spectrum in Ex. 24 obtained by mass spectrometric analysis is shown in
(148) TABLE-US-00005 TABLE 5 Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22 Target Main component Ag Ag Ag Ag Ag Additive element Au Pd Ni Si Ti Ratio of additive element 5 atomic % 10 mass % 7.8 mass % 1 atomic % 0.45 mass % Metal M.sub.Ag/Ag 0.04 0.08 0.20 0.02 0.02 thin film O/Ag n.d. 0.05 0.01 0.05 Thickness of metal thin film (nm) 7 9 10 14 13 Sheet resistance of metal thin film (/sq.) 12.4 18 23.8 5.6 5.8 Resistivity of metal thin film ( .Math. cm) 8.7 10.sup.6 1.6 10.sup.5 2.5 10.sup.5 7.6 10.sup.6 7.5 10.sup.6 Visible light transmittance of sample plate (%) 68 49 47 51 51
(149) TABLE-US-00006 TABLE 6 Ex. 23 Ex. 24 Target Type AlMgSi alloy (A6061) Cu alloy Additive element Mg: 0.8-1.2% P/Cu: 0.001 and its ratio Si: 0.4-0.8% Cu: 0.15-4.0% Cr: 0.04-0.35% Metal thin M.sub.Al/Al, M.sub.Cu/Cu Mg/Al: 0.07 P/Cu: n.d. film O/Al, O/Cu 1.48 0.08 Thickness of metal 20 11 thin film (nm) Sheet resistance of metal 7.6 21.8 thin film (/sq.) Resistivity of metal thin 1.5 10.sup.5 2.4 10.sup.5 film ( .Math. cm) Visible light transmittance 7 53 of sample plate (%)
(150) In Table 6, 1.48 in the row of the metal thin film in Ex. 23 represents the O/Al value, and 0.08 in the row of the metal thin film in Ex. 24 represents the O/Cu value.
(151) In Tables 5 and 6, n.d. represents the detection lower limit or lower by X-ray photoelectron spectroscopy. In Table 5, with respect to a trace amount of O in the metal thin film in Ex. 19, the composition cannot be calculated since the binding energy positions of O1s and Pd3p.sub.3/2 as main peaks overlap with each other, and the O/Ag value is represented as -.
INDUSTRIAL APPLICABILITY
(152) The sample plate for mass spectrometric analysis of the present invention is useful as a sample plate for mass spectrometric analysis used when IMS is conducted by LDI-MS.
(153) This application is a continuation of PCT Application No. PCT/JP2016/063676, filed on May 6, 2016, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-095363 filed on May 8, 2015. The contents of those applications are incorporated herein by reference in their entireties.
REFERENCE SYMBOLS
(154) 10: Sample plate for mass spectrometric analysis 12: Substrate 14: Metal thin film What is claimed is: