JP2005009948A - Atomic emission spectrometer for surface microregion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atomic emission spectrometer for a surface microregion capable of qualitatively and quantitatively analyzing elements, with a spatial resolution of a diameter of several nms and a depth of several nms. <P>SOLUTION: This atomic emission spectrometer for the surface microregion is constituted so that a probe 1, having a noble metal provided to the tip thereof, is allowed to approach the vicinity of the surface of a sample 6 to simultaneously irradiate the probe 1 and the surface of the sample 6, with a pulse laser 9 with a pico second, such as a pico second pulse Nd-YAG laser (355 nm, 266 nm) or a femto second pulse regenerative amplified Ti-sapphire laser (800 nm) and the sample atoms of the surface micro region are ablated, to perform not only qualitative analysis from the emission energy from excited atoms or ions, but also quantitative analysis from the emission quantity thereof. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for irradiating a sample surface with a pulse laser and measuring an emission spectrum from evaporated atoms and molecules, and in particular, emits light from atoms and molecules present in a minute region of nm level on the sample surface. It is about analysis.
[0002]
[Prior art]
Conventionally, there are laser ablation ICP emission analysis, glow discharge emission analysis, and the like as methods for measuring an atomic / molecular emission spectrum constituting a substance on a solid surface and performing elemental analysis.
[0003]
These materials irradiate a sample with laser or plasma, evaporate constituent atoms and molecules from the surface due to their physical and chemical effects, and spectroscopically analyze the light emitted when some of them are excited and relaxed to the ground state. Measure with a detector / high sensitivity detector.
[0004]
In this case, even if the laser or plasma is condensed or converged, the diameter thereof is about μm, so that the spatial resolution of information obtained corresponding to this is an area having a diameter of μm.
[0005]
Furthermore, in order to improve the spatial resolution, a technique combining a pulse laser and a near-field optical microscope has been developed.
[0006]
For example, a nanosecond pulse nitrogen laser (355 nm) is introduced into an optical fiber having a tip diameter of about 100 nmφ.
[0007]
Since the tip of the optical fiber has an aperture diameter shorter than the wavelength of the light, the light does not propagate and is converted to near-field light having a spread of about the aperture diameter.
[0008]
As a result, the near-field light is irradiated only to the region of about 100 nmφ, and only the irradiated region on the sample surface is evaporated and excited, and an atomic emission spectrum thereof is obtained.
[0009]
As a result, qualitative quantitative analysis of elements with a spatial resolution of about 100 nm in diameter and several tens of nm in depth has been achieved.
[0010]
[Problems to be solved by the invention]
In the conventional elemental analysis method having a spatial resolution of several hundreds of nanometers in diameter as described above, atomic emission after fine particle detachment using pulsed laser excitation is realized, but an optical fiber is used for laser irradiation. As long as there is a limit to improving the spatial resolution. For example, the optical fiber tip has an opening diameter of 100 nm and is shielded from light by a metal such as Al so that light does not leak. Generally, this light is introduced when light exceeding the energy threshold necessary for fine particle evaporation is introduced. Since the shielding metal melts and the aperture diameter cannot be maintained, the incident light power is limited.
[0011]
Therefore, if the incident light power is increased to evaporate the sample (atom or molecule), there is a problem that the spatial resolution cannot be improved.
[0012]
Further, due to the same problem, an optical fiber having an aperture diameter of 100 nm or less cannot be used, and it is difficult to realize further improvement in spatial resolution.
[0013]
Therefore, in view of the above situation, an object of the present invention is to provide a surface microregion atomic emission spectrometer capable of performing qualitative quantitative analysis of elements with a spatial resolution of several nm in diameter and several nm in depth.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] In a surface micro-area atomic emission spectrometer, a probe made of a noble metal material with a needle-like tip, a probe control unit that brings the tip of the probe closer to the surface of the sample, and the probe and the sample surface Qualitatively based on the energy of light emitted from excited atoms and ions by ablating the sample atoms in the surface and micro area of the sample by irradiation with the pulsed laser of less than picoseconds. It is characterized by quantitative analysis from the analysis and the amount of luminescence.
[0015]
[2] The surface microregion atomic emission spectrometer according to [1] above, wherein the noble metal at the tip of the probe is gold or silver.
[0016]
[3] In the surface microregion atomic emission spectrometer according to the above [1], the pulse laser of picosecond or less is a picosecond pulse Nd-YAG laser (355 nm, 266 nm) or a femtosecond pulse reproduction amplified Ti sapphire laser (800 nm). ).
[0017]
As described above, according to the present invention, a probe such as an atomic force microscope or a scanning tunneling microscope approaches the sample surface near the sample surface, and a pulse laser of picosecond or less is simultaneously applied to the probe and the sample. Irradiate. At that time, an interaction such as an electric field enhancement is induced between the light and the probe, and the surface atoms are evaporated and excited. At that time, emission of an atomic spectrum from the excited atom occurs, and qualitative and quantitative analysis becomes possible by spectral detection. Since the region excited by evaporation has a diameter of several nm and a depth of several nm, analysis of surface elements in a micro region is achieved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0019]
FIG. 1 is a configuration diagram of a surface microregion atomic emission spectrometer showing an embodiment of the present invention.
[0020]
In this figure, 1 is a probe, 2 is a cantilever, 3 is a laser irradiation unit, 4 is a laser beam, 5 is a quadrant photodetector, 6 is a sample, 7 is a sample mounting table, and 8 is an excitation pulse laser irradiation unit ( Reproduction amplification femtosecond laser; femtosecond pulse regeneration amplification Ti sapphire laser), 9 is an excitation pulse laser, 10 is a focus lens, 11 is an objective lens, and 12 is an emission spectrum measurement unit (spectral detection system).
[0021]
As described above, the surface micro-region atomic emission spectrometer includes the probe control unit (not shown) using the atomic force, the excitation pulse laser irradiation unit 8, and the emission spectrum measurement unit 12. The probe control unit brings the probe 1 close to the vicinity of several nanometers just above the sample 6 by the cantilever 2 that holds the probe 1 having a needle-like tip made of a material such as gold or silver.
[0022]
Here, as a method of bringing the probe 1 close, an optical lever method is used, the cantilever 2 is irradiated with the laser beam 4, the light reflected on the surface of the sample 6 is detected by the four-divided photodetector 5, and the atom is detected from the reflection position. The force is estimated and the distance from the sample 6 to the probe 1 is controlled.
[0023]
With the probe 1 close to the sample 6, an excitation pulse laser 9 from a regenerative amplification femtosecond laser 8, which is an excitation source, passes through a focus lens 10 and has a diameter of several μm on the surface of the probe (tip) 1 and the sample 6. Irradiate.
[0024]
Atomic emission from ultrafine particles generated from the surface of the sample 6 due to the interaction between the excitation pulse laser 9 and the probe 1 is collected by the objective lens 11 and introduced into the spectroscopic detection system 12 to measure the emission spectrum.
[0025]
As a result, the element type can be identified from the measured emission wavelength, and the quantitative analysis can be performed from the light emission amount (light intensity).
[0026]
In the apparatus of the present invention, since the electric field enhancement effect generated between the probe 1 and the excitation pulse laser 9 of picosecond or less is used for fine particle evaporation, the interaction is several nanometers or less. It is possible to evaporate and excite atoms on the surface with a spatial resolution and a resolution of a depth of several nanometers or less.
[0027]
As an application example, FIG. 2 shows an atomic force microscope image of the silicon surface on which PdCu alloy fine particles are adsorbed. In FIG. 2A, the state in which PdCu alloy fine particles having a diameter of 10 nm are adsorbed on the silicon surface is observed as an atomic force microscope image. FIG. 2 (b) shows an atomic force microscope image showing that a part of the apparatus is evaporated in a crater as a result of evaporation.
[0028]
From this figure, it can be seen that evaporation only in the region of about 10 nmφ is realized.
[0029]
Also, FIG. 3 shows an emission spectrum when the PdCu alloy fine particles are evaporated from the crater portion of FIG. In FIG. 3, the horizontal axis represents wavelength (nm) and the vertical axis represents light intensity (relative unit).
[0030]
As is apparent from this figure, an atomic spectrum of palladium with a wavelength of 283.3 nm and copper of 327.4 nm was detected, and no light emission by silicon was observed.
[0031]
The same result can be obtained even if the excitation laser 9 is a picosecond pulse Nd-YAG laser (355 nm, 266 nm).
[0032]
The above results indicate that the present apparatus has achieved emission spectroscopic analysis of atoms existing on the sample surface with a spatial resolution of several nmφ.
[0033]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0034]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0035]
(A) Since the electric field enhancement effect between light and a noble metal probe is used for evaporation of the surface constituent material, the excitation evaporation region is limited to several nm, and element identification and quantitative analysis with a spatial resolution of several nm Is possible.
[0036]
(B) Since an atomic emission spectrum can be obtained with a spatial resolution of several nm, atomic identification and quantification are possible. In addition, it is possible to solve the problem of atom identification, which is difficult with a scanning probe microscope or a near-field optical microscope.
[0037]
(C) Since an electric field or the like is not used, it can be applied to a non-conductor. These characteristics can contribute not only to the identification of adsorbed atoms on the metal surface, but also to the identification of atoms adsorbed on the semiconductor surface, as well as the identification of atoms existing locally in the biological cell membrane and the elucidation of their behavior.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a surface microregion atomic emission spectrometer showing an embodiment of the present invention.
FIG. 2 is a diagram showing an atomic force microscope image of a silicon surface on which PdCu alloy fine particles are adsorbed.
FIG. 3 is an atomic emission spectrum generated when the crater portion of FIG. 2 is formed.
[Explanation of symbols]
1 Probe 2 Cantilever 3 Laser irradiation part (laser light source)
Reference Signs List 4 Laser beam 5 Quadrant photo detector 6 Sample 7 Sample mounting table 8 Excitation pulse laser irradiation unit 9 Excitation pulse laser 10 Focus lens 11 Objective lens 12 Emission spectrum measurement unit (spectral detection system)

Claims (3)

(A) a probe having a needle-like tip made of a noble metal material;
(B) a probe control unit that brings the tip of the probe close to the surface of the sample;
(C) a pulse laser of picosecond or less that is simultaneously irradiated onto the probe and the sample surface;
(D) ablating the sample atoms on the surface of the sample and in a minute region by irradiation with the pulse laser of the picosecond or less, and qualitative analysis from the energy of emission from the excited atoms and ions, and quantitative analysis from the amount of emission Characteristic surface micro-area atomic emission spectrometer. 2. The surface microregion atomic emission spectrometer according to claim 1, wherein the noble metal at the tip of the probe is gold or silver. 2. The surface microregion atomic emission spectrometer according to claim 1, wherein the picosecond pulse laser is a picosecond pulse Nd-YAG laser (355 nm, 266 nm) or a femtosecond pulse reproduction amplified Ti sapphire laser (800 nm). Surface micro-area atomic emission spectrometer characterized by

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