CN115639268A - Time-of-flight secondary ion mass spectrometer and mass spectrometry method thereof - Google Patents
Time-of-flight secondary ion mass spectrometer and mass spectrometry method thereof Download PDFInfo
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Abstract
The application relates to the field of component analysis, and particularly discloses a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof, wherein the method comprises the following steps of S1: determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode; step S2: focusing the components on a grating to obtain a first component distribution map; and step S3: judging whether a target area with uniformly distributed colors exists in the first component distribution map; and step S4: if the first component distribution map has a target area, scanning the target area in a sputtering mode, and performing mass spectrometry on a sample to be detected; step S5: if the target region does not exist in the first component distribution map, the scanning region on the surface of the sample to be detected is replaced, and step S1 is executed. According to the mass spectrometry method, before sputtering scanning is carried out on a sample to be detected, the surface of the sample to be detected is scanned in a scanning mode, the position is determined according to imaging, then sputtering scanning is carried out, and the accuracy of mass spectrometry is improved.
Description
Technical Field
The application relates to the field of component analysis, in particular to a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof.
Background
The secondary ion mass spectrum is a nearly nondestructive surface analysis technology, can obtain information such as isotopes and components on the surface of a substance to be detected, has high analysis sensitivity and low signal background noise, does not need to carry out chemical treatment on a sample, and can directly analyze the isotope and the componentThe characteristics of the body sample are widely applied to the fields of analytical chemistry, environmental science, life science, earth science and the like. The secondary ion mass spectrum can acquire accurate chemical element composition information in a very small range (several microns) on a sample target, and can be used for surface element analysis of various samples. The secondary ion mass spectrometry techniques are divided into static secondary ion mass spectrometry using low ion current density (less than 10) and dynamic secondary ion mass spectrometry -7 A/cm 2 ) And bombarding the surface with low-energy (hundreds to thousands of eV) primary ions, and carrying out mass spectrum analysis on the emergent secondary ions.
Time of Flight Secondary Ion Mass spectrometry (TOF-SIMS) analysis is a static Mass spectrometry method, which combines a Secondary Ion Mass spectrometry technique with a Time of Flight Mass spectrometry technique, and uses primary ions to excite the surface of a sample, so as to punch out extremely small amounts of Secondary ions, and measures the Ion Mass according to the different flying times of the Secondary ions to a detector due to different masses. The device can analyze the sample layer by layer under the condition of not damaging the surface of the sample, and realizes the depth analysis of the sample. Compared with other surface depth analysis, the time-of-flight secondary ion mass spectrometry has the advantages of high analysis sensitivity, high signal-to-noise ratio and high depth resolution. At present, when the time-of-flight secondary ion mass spectrometry is carried out, a sputtering ion gun is directly started, the surface of a sample is scanned in a sputtering mode, and elements and the content of the sample are determined according to data obtained by scanning. However, the existing time-of-flight secondary ion mass spectrometry ignores the problem of non-uniformity of the sample surface in the analysis process, and when the sample surface is non-uniform, the measurement result error is larger.
Therefore, how to solve the above technical problems should be a great concern to those skilled in the art.
Disclosure of Invention
The application aims to provide a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof, so as to improve the accuracy of mass spectrometry detection.
In order to solve the technical problem, the present application provides a time-of-flight secondary ion mass spectrometry method, including:
step S1: determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode;
step S2: focusing the components on a grating to obtain a first component distribution map;
and step S3: judging whether a target area with uniformly distributed colors exists in the first component distribution map;
and step S4: if the target area exists in the first component distribution map, scanning the target area in a sputtering mode, and performing mass spectrometry on the sample to be detected;
step S5: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Optionally, scanning the target region in a sputtering mode, and performing mass spectrometry on the sample to be detected includes:
scanning the target area by utilizing a first ion beam in a sputtering mode to obtain a mass spectrogram corresponding to the target area;
and determining the components and the component content of the sample to be detected according to the mass spectrogram.
Optionally, when the number of the target regions is two or more, determining the component content of the sample to be detected according to the mass spectrogram includes:
determining the content of the undetermined components of the sample to be detected according to the mass spectrogram corresponding to each target area;
and determining the average value of the contents of all the undetermined components as the component content of the sample to be detected.
Optionally, the method further includes:
acquiring the spectral peak intensity of each component at each second scanning;
and determining the relation between the content of each component in the sample to be detected and the depth distribution according to the spectrum peak intensity.
Optionally, the method further includes:
focusing the components on a grating to obtain a second component distribution map;
and checking the uniformity of the surface of the sample to be tested according to the second component distribution map.
Optionally, in the scanning mode, determining the components of the sample to be detected according to the secondary ions generated on the surface of the sample to be detected includes:
in a scanning mode, scanning the surface of the sample to be detected by using a second ion beam so as to generate secondary ions on the surface of the sample to be detected;
determining the mass-to-nuclear ratio of the secondary ions according to the flight time of the secondary ions;
and determining the components of the sample to be detected according to the nucleus ratio.
Optionally, scanning the surface of the sample to be measured with the second ion beam includes:
by using Bi + And scanning the surface of the sample to be detected by the ion beam, wherein the scanning time is 30-120 s.
Optionally, scanning the target region with the first ion beam comprises:
by using O 2 + An ion beam scans the target region, wherein the O 2 + The energy of the ion beam is between 1keV and 3keV, and the O 2 + The incident angle of the ion beam is between 20 and 70 degrees, and the scanning time is between 30 and 120min.
Optionally, in the scanning mode, before determining the components of the sample to be measured according to the secondary ions generated on the surface of the sample to be measured, the method further includes:
and neutralizing the charges on the surface of the sample to be detected.
The present application further provides a time-of-flight secondary ion mass spectrometer for performing any of the above-described methods of time-of-flight secondary ion mass spectrometry.
The application provides a time-of-flight secondary ion mass spectrometry method, which comprises the following steps: step S1: determining the components of a sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode; step S2: focusing the components on a grating to obtain a first component distribution map; and step S3: judging whether a target area with uniformly distributed colors exists in the first component distribution map; and step S4: if the target area exists in the first component distribution map, scanning the target area in a sputtering mode, and performing mass spectrometry on the sample to be detected; step S5: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Therefore, in the mass spectrometry method, before sputtering scanning is performed on a sample to be detected, the surface of the sample to be detected is scanned in a scanning mode, components of the sample to be detected are determined according to secondary ions generated on the surface of the sample to be detected, a first component distribution diagram is obtained according to the components, whether a target area with uniformly distributed colors exists in the first component distribution diagram or not is judged, the area with uniformly distributed colors indicates that the components of the area are uniformly distributed, mass spectrometry is performed on the target area with uniformly distributed colors, if the target area with uniformly distributed colors does not exist, the scanning area is replaced, the target area is re-determined, and mass spectrometry is performed, so that the accuracy of mass spectrometry is improved.
In addition, the application also provides a time-of-flight secondary ion mass spectrometer with the advantages.
Drawings
In order to clearly illustrate the embodiments or technical solutions of the present application, the drawings used in the embodiments or technical solutions of the present application will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flow chart of a method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 2 is a flow chart of another method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 3 is a flow chart of another method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 4 is a flow chart of another method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 5 is a flow chart of another method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 6 is a flow chart of another method of time-of-flight secondary ion mass spectrometry provided in an embodiment of the present application;
FIG. 7 is a spectrum peak of iron element in the stainless steel metal plate according to the embodiment of the present application;
FIG. 8 is a peak spectrum diagram of chromium in a stainless steel metal plate according to an example of the present application;
FIG. 9 is a peak chart of nickel in a stainless steel metal plate according to an example of the present application;
FIG. 10 is a graph showing peaks of molybdenum in a stainless steel metal plate according to an example of the present application;
FIG. 11 is the elemental Ce on the surface of the stainless steel metal plate in the scanning mode according to the embodiment of the present application 140 The composition map of (1);
FIG. 12 is the elemental Ce on the surface of the stainless steel metal plate in the scanning mode according to the embodiment of the present application 142 The composition map of (1);
FIG. 13 is the elemental Ce on the surface of the stainless steel metal plate in the sputtering mode according to the embodiment of the present application 140 The composition map of (1);
FIG. 14 shows elemental Ce on the surface of a stainless steel metal plate in a sputtering mode according to an embodiment of the present application 142 The composition map of (1);
FIG. 15 is a content-depth distribution of each element of a stainless steel metal plate according to an example of the present application;
fig. 16 is a schematic structural diagram of a time-of-flight secondary ion mass spectrometer provided in an embodiment of the present application.
Detailed Description
In order that those skilled in the art will better understand the disclosure, the following detailed description will be given with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as specifically described herein, and it will be appreciated by those skilled in the art that the present invention may be practiced without departing from the spirit and scope of the present invention and that the present invention is not limited by the specific embodiments disclosed below.
As described in the background section, currently, when performing time-of-flight secondary ion mass spectrometry, a sputtering ion gun is directly turned on, the surface of a sample is scanned in a sputtering mode, and elements and contents of the sample are determined according to data obtained by scanning. However, the existing time-of-flight secondary ion mass spectrometry ignores the problem of non-uniformity of the sample surface in the analysis process, and when the sample surface is non-uniform, the measurement result error is larger.
In view of the above, the present application provides a time-of-flight secondary ion mass spectrometry method, please refer to fig. 1, which includes:
step S1: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
Before scanning, a sample to be tested needs to be prepared, and the sample to be tested must be under the condition of ultrahigh pressure (pressure) in a SIMS analysis chamber<10 8 Torr) was kept stable. SIMS analysis must be performed under ultra-high voltage conditions for a number of reasons. Ensuring that incident particles and secondary ions (secondary ions) travel from their origin to their final destination without colliding with other atoms, molecules or ions; the composition and structure of the sample must remain constant during the analysis. The ultra-high pressure condition is particularly important to prevent contamination of the sample during SIMS analysis because SIMS has surface specificity and can detect substances at concentrations in the ppm to ppb range.
The form of the sample to be tested includes, but is not limited to, pressed powders, bulk films, fibers, particles, and films spin-coated on a substrate (e.g., glass, aluminum foil, silver, etc.). The sample to be tested is fixed on the sample pile by a mechanical mode or by using a double-sided adhesive tape. The thickness and morphology of the sample to be tested will affect the probability of secondary ion generation and hence the stability of the SIMS spectrum. The cleanliness of the sample surface to be tested is also an important consideration in sample preparation, as any contaminants deposited on the surface during handling or processing can affect the accuracy of the analysis. In addition, the sample to be tested should be analyzed immediately after preparation to avoid surface diffusion, molecular reorientation or contamination of the sample surface by the laboratory environment.
As an implementation manner, in the scanning mode, determining the composition of the sample to be measured according to the secondary ions generated on the surface of the sample to be measured includes:
step S11: and in a scanning mode, scanning the surface of the sample to be detected by using a second ion beam so as to generate secondary ions on the surface of the sample to be detected.
Optionally, scanning the surface of the sample to be measured with the second ion beam includes: by using Bi + And scanning the surface of the sample to be detected by the ion beam, wherein the scanning time is 30-120 s. However, the present application is not limited thereto, and other types of ion beams may be used for scanning, and the dose and scanning time of the ion beam are determined according to the circumstances. Bi + The dose of the ion beam being selected to be low according to the instrument used
Step S12: and determining the mass-to-nuclear ratio of the secondary ions according to the flight time of the secondary ions.
Step S13: and determining the components of the sample to be detected according to the nucleus ratio.
Each nuclear-to-cytoplasmic ratio has corresponding components, and when one nuclear-to-cytoplasmic ratio corresponds to multiple components, the specific type of the sample to be detected is combined to determine which component in the sample to be detected is specific.
Steps S11 to S13 will be explained in combination.
And the ions in the second ion beam are incident to the surface of the sample to be detected, so that the sample to be detected generates secondary ions, and the secondary ions enter the TOF analyzer and are finally detected. TOF analyzers separate secondary ions according to the mass-to-nuclear ratio m/z (mass/charge). The mass m of the ions is determined by the time it takes for them to travel the length L of the field-free flight tube after accelerating to a common energy E in the extraction field. The relationship between the common energy E and the time of flight t is:
E＝mv 2 /2＝mL 2 /2zt 2 (1)
where v is the velocity of the secondary ions, m is the mass of the ions, t is the flight time, E is the acceleration energy for the secondary ions, and L is the length of the field-free flight tube, i.e., the flight distance of the secondary ions.
The flight time t is proportional to the half power of the mass m of the exiting secondary ions, i.e.:
t＝L(m/2zE) 1/2 (2)
therefore, under the same energy condition, ions with small mass fly faster and are detected earlier than ions with large mass.
When the ion energy is constant, the best ion separation or mass resolution can be obtained. The primary ion source must produce secondary ions with minimal time dispersion with a short pulse width (sub-nanosecond) to produce minimal energy spread. A fixed voltage then accelerates the secondary ions into the TOF analyzer, the polarity of which determines whether positive or negative secondary ions are being analyzed. The energy and angular dispersion of the secondary photons generated by the emission process can be compensated with a focusing element such as an ion mirror or a mirror. For example, the mirrors focus the secondary ions through a decelerating electric field in the middle of the flight path, thereby improving mass separation (higher mass resolution).
The secondary ions are separated in the TOF analyzer and focused onto a detector by an ion lens. Since high-mass ions propagate at a slower speed, post-acceleration voltages of up to 15keV are applied to the ions to improve detection efficiency. The ion impact detection unit is generally composed of a photoelectric conversion electrode, a groove plate, a scintillator, a photomultiplier and a counter which are connected in series.
Further, a mass spectrum can be determined according to the mass-to-nuclear ratio and the electric signal intensity of the secondary ions.
Step S2: focusing the components on a grating to obtain a first component distribution map.
The first component profile is a colored picture.
The chemical composition of the sample to be measured can be mapped by focusing the main beam to a narrow diameter and rastering the surface. A complete mass spectrum includes each point of the beam grating, and this mode is called microprobe imaging. Using liquid metal ion guns (e.g. Ga) + Ion source) the main beam can be focused to 150 nm, allowing images to be generated with the same lateral resolution. The measurement may take several minutes to several hours. The smaller beam diameter reduces the amount of material available per pixel (image point) in the uppermost monolayer. This limits the number of secondary ions that can be generated and reduces the sensitivity and dynamic range of each spot. After data acquisition, a particular ion or combination of ions may be selected and its surface profile plotted. Also using SIMS imaging, a region of interest can be identified from the total ion image and the mass spectra of the pixels in that region summed, allowing spectral evaluation in the recovered sensitivity and dynamic range. To generate a topographical map of the surface, ion-induced secondary electrons (similar to scanning electron microscopy) or total secondary ion emission may be used.
And step S3: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
Whether there is a target region can be determined by observing the first composition profile.
And step S4: and if the target area exists in the first component distribution map, scanning the target area in a sputtering mode, and performing mass spectrometry on the sample to be detected.
Step S5: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Before a sample to be detected is subjected to sputtering scanning, the surface of the sample to be detected is scanned in a scanning mode, components of the sample to be detected are determined according to secondary ions generated on the surface of the sample to be detected, a first component distribution diagram is obtained according to the components, whether a target area with uniformly distributed colors exists in the first component distribution diagram or not is judged, the area with uniformly distributed colors shows that the components of the area are uniformly distributed, the target area with uniformly distributed components is subjected to mass spectrometry, if the target area with uniformly distributed colors does not exist, the scanning area is replaced, the target area is re-determined, mass spectrometry is performed again, accidental errors caused by non-uniform surfaces of the sample to be detected are avoided, and therefore the accuracy of mass spectrometry is improved.
Referring to fig. 2, in an embodiment of the present application, based on the above-mentioned embodiment, the time-of-flight secondary ion mass spectrometry method includes:
step S1: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
Step S2: focusing the components on a grating to obtain a first component distribution map.
And step S3: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
And step S4: if the target area exists in the first component distribution map, scanning the target area by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target area.
As one possible implementation, scanning the target region with a first ion beam includes:
by using O 2 + An ion beam scans the target region, wherein the O 2 + The energy of the ion beam is between 1keV and 3keV, and the O 2 + The incident angle of the ion beam is between 20 and 70 degrees, and the scanning time is between 30 and 120min.
Step S5: and determining the components and the component content of the sample to be detected according to the mass spectrogram.
The abscissa of the mass spectrum is the mass-to-nuclear ratio and the ordinate is the intensity. The mass spectrogram contains a large number of peaks, the components of the sample to be detected can be determined according to the mass-to-nuclear ratio, and the component content is determined according to the area of the peaks. By assessing the quality of the signal, peaks can generally be identified from the molecular ions of the analyte, fragments of the molecular ions, and ions of any other components that may be present in the sample.
The method used to assess TOF-SIMS signals is similar to conventional mass spectrometry. One method is to compare the mass spectra of the sample to be tested with the fingerprint spectra of the standard using a spectral library and a manual. Furthermore, the latest software version accompanying TOF-SIMS mass spectrometers contains a database with a searchable library of spectra. The operator may add other standard spectra. Another method of TOF-SIMS spectral evaluation is logical inference. Molecular structure can generally be identified by knowledge of fragmentation patterns and fragmentation pathways. The fragmentation rules (α and β fragmentation, rearrangement processes) applicable to electron impact mass spectrometry are useful in elucidating fragmentation processes; TOF-SIMS software containing a database allowing "peak identification" is also useful; the exact mass of the peak of interest is considered and a list of possible ion information is generated.
Step S6: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
During mass spectrometry, a target area on the surface of a sample to be detected can be directly subjected to sputtering scanning, so that the components and the component content of the sample to be detected can be determined. In one embodiment of the present application, in order to improve the accuracy of the measurement, a plurality of target areas on the surface of the sample to be measured may be measured. When the number of the target regions is two or more, referring to fig. 3, the time-of-flight secondary ion mass spectrometry method includes:
step S1: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
Step S2: focusing the components on a grating to obtain a first component distribution map.
And step S3: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
And step S4: if the target area exists in the first component distribution map, scanning the target area by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target area.
Step S5: and determining the content of the undetermined components of the sample to be detected according to the mass spectrogram corresponding to each target area.
Step S6: and determining the average value of the contents of all the undetermined components as the component content of the sample to be detected.
Step S7: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Based on the above embodiments, in an embodiment of the present application, referring to fig. 4, the time-of-flight secondary ion mass spectrometry method includes:
step S1: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
Step S2: focusing the components on a grating to obtain a first component distribution map.
And step S3: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
And step S4: if the target area exists in the first component distribution map, scanning the target area by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target area.
Step S5: and determining the components and the component content of the sample to be detected according to the mass spectrogram.
Step S6: the spectral peak intensity of each component at each second scan is acquired.
Step S7: and determining the relation between the content of each component in the sample to be detected and the depth distribution according to the spectrum peak intensity.
Step S8: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
The ion mass spectrometry method in this embodiment can obtain the relationship between the content and the depth distribution of each component in the sample to be detected, that is, realize the depth analysis of the sample to be detected.
In an embodiment of the present application, referring to fig. 5, the time-of-flight secondary ion mass spectrometry method includes:
step S1: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
Step S2: focusing the components on a grating to obtain a first component distribution map.
And step S3: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
And step S4: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Step S5: if the target area exists in the first component distribution map, scanning the target area by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target area.
Step S6: and determining the components and the component content of the sample to be detected according to the mass spectrogram.
Step S7: the spectral peak intensity of each component at each second scan is acquired.
Step S8: and determining the relation between the content of each component in the sample to be detected and the depth distribution according to the spectrum peak intensity.
Step S9: the components are focused onto a grating to obtain a second component distribution map.
It is understood that the composition in this step is a composition scanned in the sputtering mode.
Step S10: and checking the uniformity of the surface of the sample to be tested according to the second component distribution map.
And judging the uniformity of the surface of the sample to be detected according to the color distribution condition of the second component distribution map.
In this embodiment, not only can the components and the component content of the sample to be detected be analyzed, and the second component distribution map of the sample to be detected is obtained, so that the transverse analysis of the sample to be detected is realized, but also the longitudinal analysis of the sample to be detected can be realized.
Referring to fig. 6, in an embodiment of the present application, based on the above-mentioned embodiments, the time-of-flight secondary ion mass spectrometry method includes:
step S1: and neutralizing the charges on the surface of the sample to be detected.
The electrons emitted by the electron gun can be used to neutralize the charge on the surface of the sample to be measured.
Most samples of biological material to be tested are electrical insulators and accumulate charge on the surface during analysis, which can reduce or completely eliminate secondary ion signals. Charging of the sample to be tested can occur during sputtering because positively charged primary ions bombard the surface of the sample to be tested and simultaneously lose secondary electrons, which area will acquire a net positive charge unless the sample to be tested has sufficient conductivity to transport the electrons to the sputtering area. In order to neutralize charge accumulation during TOF-SIMS analysis, the sample surface to be measured is flooded with low energy electron pulses between the primary ion pulses, and the current and voltage of the electrons must be low enough to minimize electron-stimulated ion emission and damage to the sample to be measured.
The recovery rate of the secondary ions depends on several factors and is not in direct proportion to the concentration of the components in the sample to be detected, so that TOF-SIMS quantitative analysis has certain difficulty. The "matrix effect" plays an important role in TOF-SIMS quantitative analysis, and the problem can be defined as the change in ion yield with changes in surface composition. In different chemical environments, the same analyte will not have the same secondary ion yield, and therefore a direct comparison between samples is difficult. The environment of a single test sample can also change during analysis. As a result, preferential sputtering can result in varying degrees of particle removal from the sample being tested. In addition, the probability of ion formation may vary due to variations in the sputtering process.
Step S2: and determining the components of the sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode.
And step S3: focusing the components on a grating to obtain a first component distribution map.
And step S4: and judging whether a target area with uniformly distributed colors exists in the first component distribution map.
Step S5: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
Step S6: if the target area exists in the first component distribution map, scanning the target area by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target area.
Step S7: and determining the components and the component content of the sample to be detected according to the mass spectrogram.
Step S8: the spectral peak intensity of each component at each second scan is acquired.
Step S9: and determining the relation between the content of each component in the sample to be detected and the depth distribution according to the spectrum peak intensity.
Step S10: the components are focused onto a grating, resulting in a second component profile.
It is understood that the composition in this step is a composition scanned in the sputtering mode.
Step S11: and checking the uniformity of the surface of the sample to be tested according to the second component distribution map.
In this embodiment, before the sample to be measured is scanned, the charges on the surface of the sample to be measured are neutralized, so that the electrical signal intensity of the secondary ions obtained by measurement can be enhanced.
The time-of-flight secondary ion mass spectrometry method in the present application is described below by taking the precise analysis and measurement of the content of each element in a processed 316L stainless steel metal plate sample, in which cerium is added manually and is of more interest.
And 3, starting an electron gun to neutralize the charges on the surface of the sample to be measured, and enhancing the strength of the measured electric signal.
And 5, determining the components and the contents of all elements according to the information such as the mass-to-nuclear ratio, the stainless steel grade and the like, and determining that the stainless steel mainly contains iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo) and cerium (Ce). And the chemical components of the stainless steel metal plate are focused on the grating for imaging to obtain Ce 140 And Ce 142 The composition patterns of (2) are shown in fig. 11 and 12. And selecting a uniform area as a target area according to the color distribution of the two-dimensional composition diagram, and entering the step 6. If no uniform area can be found, the sample detection position is changed, and the procedure returns to step 4.
As can be seen from fig. 11 and 12, the color uniformity of each region is different in fig. 11 and 12, which indicates that the overall uniformity of the scanned region is poor, and it is necessary to find a region with uniform color as the target region in fig. 11 and 12, and the uniformity of the distribution of the components in the target region is good.
Step 6, starting the sputtering ion gun to generate O 2 + Ion beam, incident at an angle of energy 2kev,45 degrees, instrumental analysis mode using sputtering mode, sputtering area: 350 μm, but only data are collected for an area of 100 μm in the central region, with a sampling time of 60 minutes, and the resulting secondary ions enter a time-of-flight analyzer and are calculated to obtain a spectral peak plot for that location.
And 7, determining the components and the contents of the elements according to the obtained spectral peak diagram again, and imaging againObtaining a composition profile, ce 140 And Ce 142 The composition distribution patterns of (2) are shown in fig. 13 and 14, and the uniformity of the position is analyzed. As can be seen from fig. 13, the color distribution of the whole area is uniform, and the color distribution of the whole area in fig. 14 is also relatively uniform, further proving that the color distribution of the selected target area is uniform.
And step 8, summarizing the spectrum peak information obtained by scanning every second in a sputtering mode, extracting and sorting the spectrum peak information into the same coordinate, and obtaining the content-depth distribution of each element of the stainless steel metal plate, as shown in fig. 15.
the working parameters of the time-of-flight secondary ion mass spectrometer are as follows:
primary ion beam: bi + Energy 30keV,45deg incident;
scanning area: 500 μm × 500 μm;
sputtering area: 350 μm × 350 μm;
analysis area: 100 μm × 100 μm;
secondary ion polarity and mass range: negative ions, 0-900 amu;
sputtering ion beams: o is 2 + Energy 2keV,45deg incident.
The present application further provides a time-of-flight secondary ion mass spectrometer for performing the time-of-flight secondary ion mass spectrometry method of any of the above embodiments.
A schematic diagram of a time-of-flight secondary ion mass spectrometer is shown in fig. 16, and includes an ion source 1 for emitting an ion beam, a primary ion optical system 2, and a time-of-flight analyzer 3.
When the time-of-flight secondary ion mass spectrometer in this application is carrying out mass spectrometry, before carrying out sputter scanning to the sample that awaits measuring, scan the sample surface that awaits measuring under scanning mode earlier, the composition of the sample that awaits measuring is confirmed to the secondary ion that produces according to the sample surface that awaits measuring, obtain first composition distribution diagram according to the composition, and then judge whether there is the target area of colour evenly distributed in the first composition distribution diagram, the region of colour evenly distributed shows that this part regional composition distributes evenly, and then carry out mass spectrometry to the target area that the composition distributes evenly, if there is not the target area of colour evenly distributed, then change the scanning area, confirm the target area again, mass spectrometry again, thereby promote mass spectrometry's accuracy.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other.
The time-of-flight secondary ion mass spectrometer and the mass spectrometry method thereof provided by the application are described in detail above. The principles and embodiments of the present application are explained herein using specific examples, which are provided only to help understand the method and the core idea of the present application. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.
Claims (10)
1. A method of time-of-flight secondary ion mass spectrometry comprising:
step S1: determining the components of a sample to be detected according to secondary ions generated on the surface of the sample to be detected in a scanning mode;
step S2: focusing the components on a grating to obtain a first component distribution map;
and step S3: judging whether a target area with uniformly distributed colors exists in the first component distribution map;
and step S4: if the target area exists in the first component distribution map, scanning the target area in a sputtering mode, and performing mass spectrometry on the sample to be detected;
step S5: and if the target area does not exist in the first component distribution map, replacing the scanning area of the surface of the sample to be detected, and executing the step S1.
2. The method of time-of-flight secondary ion mass spectrometry of claim 1, wherein scanning the target region in a sputtering mode and performing mass spectrometry on the sample to be tested comprises:
scanning the target area by utilizing a first ion beam in a sputtering mode to obtain a mass spectrogram corresponding to the target area;
and determining the components and the component content of the sample to be detected according to the mass spectrogram.
3. The method of claim 2, wherein determining the constituent content of the sample to be tested from the mass spectrum when the number of target regions is two or more comprises:
determining the content of the undetermined components of the sample to be detected according to the mass spectrogram corresponding to each target area;
and determining the average value of the contents of all the undetermined components as the component content of the sample to be detected.
4. The method of time-of-flight secondary ion mass spectrometry of claim 2, further comprising:
acquiring the spectral peak intensity of each component at each second scanning;
and determining the relation between the content of each component in the sample to be detected and the depth distribution according to the spectrum peak intensity.
5. The method of time-of-flight secondary ion mass spectrometry of claim 2, further comprising:
focusing said components onto a grating to obtain a second component profile;
and checking the uniformity of the surface of the sample to be tested according to the second component distribution map.
6. The method of time-of-flight secondary ion mass spectrometry of claim 1 in which determining the composition of the sample to be tested from secondary ions generated at the surface of the sample to be tested in a scan mode comprises:
in a scanning mode, scanning the surface of the sample to be detected by using a second ion beam so as to generate secondary ions on the surface of the sample to be detected;
determining the mass-to-nuclear ratio of the secondary ions according to the flight time of the secondary ions;
and determining the components of the sample to be detected according to the nucleus ratio.
7. The method of time-of-flight secondary ion mass spectrometry of claim 6 in which scanning the surface of the sample to be tested with a second ion beam comprises:
by using Bi + And scanning the surface of the sample to be detected by the ion beam, wherein the scanning time is 30-120 s.
8. The method of time-of-flight secondary ion mass spectrometry of claim 2, wherein scanning the target region with a first ion beam comprises:
by using O 2 + An ion beam scans the target region, wherein the O 2 + The energy of the ion beam is between 1keV and 3keV, and the O 2 + The incident angle of the ion beam is between 20 and 70 degrees, and the scanning time is between 30 and 120min.
9. The method of time-of-flight secondary ion mass spectrometry of any of claims 1 to 8, further comprising, prior to determining the composition of the sample to be tested from secondary ions generated at the surface of the sample to be tested in a scan mode:
and neutralizing the charges on the surface of the sample to be detected.
10. A time-of-flight secondary ion mass spectrometer for performing a time-of-flight secondary ion mass spectrometry method according to any one of claims 1 to 9.
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