Glow discharge mass spectrometer
Glow discharge mass spectrometry (GDMS) is considered as the most effective method for the direct trace and ultra trace element analysis of solid conductive materials. Because of its direct solid sampling, nearly 20 years has been widely used in high purity metals, alloys and other materials analysis. GDMS not only has the advantages of excellent detection limits and wide dynamic range, but also has the advantages of simple sample preparation, small difference in sensitivity between elements, and low matrix effect. GDMS has been widely used in the field of electronics, chemistry, metallurgy, geology and materials science for its superior analytical performance. It has shown its superiority in the analysis of high-purity metals and semiconductors, and has been widely used in the fields of insulators, powders, Liquid, organic and biological materials analysis and determination of negative ions in the application is also actively research and improvement, development prospects are very broad.
principle
Glow discharge (GD) belongs to the phenomenon of gas discharge under low pressure and has historically been used as an effective atomization and ionization source for analysis. In the glow discharge mass spectrometer ion source, the sample to be tested is used as the cathode of the glow plasma light source. An inert gas (usually argon) is filled between the cathode and the anode, and the pressure is maintained at 10-1000 Pa. When a high voltage of 500 ~ 1500 V is applied to both ends of the electrode, Ar ionizes into electrons and Ar +, and Ar + accelerates to the cathode under the action of an electric field. The atoms of the cathode sample are stripped from the cathode sample (cathode sputtering) by the energy of 5-15 eV under the impact of argon ions, into the plasma until they reach the plasma, and the electrons in the plasma or metastable Ar atom collisions (Penning) ionization, become positive ions: M + e- → M + + 2 e-, M + Ar * a M + + Ar + e-. It has been demonstrated that Penning ionization in the GD source is the dominant ionization process.
Cathode sputtering products for the cathode material atoms, atomic groups, but also produce secondary and secondary electrons. Cathode sputtering process is precisely the sample atoms generated, but also for the depth of the sample can be the theoretical basis. The mechanism by which a large number of atoms, ions and electrons participate in the plasma collision process makes the glow discharge very complicated. Among the many areas formed by glow discharge, there are two areas of importance for sample analysis, the "negative glitch" and the "dark cathode area." The cathode dark area is a thin layer near the cathode surface with a high positive ion density. The voltage drop across the glow discharge is almost entirely applied to this area. Negative glow area generally occupy most of the volume of glow discharge, almost a field-free area, the electronic bear the role of conduction current. Therefore, secondary ions generated by sputtering are generally pulled back to the electrode surface to form deposition difficult to pass the dark cathode region, while the neutral atoms will be diffused into the negative brightness region is excited or ionized, of course, may also be frequent The collision is returned during the collision, which is an obvious feature of glow discharge. Glow discharge sources have the ability to produce atoms of a representative composition in a solid sample, along with the ability to generate excited and ionic states for these atoms. Therefore, glow discharge can be used as both a light source and an ion source for the content and depth analysis of solid samples. Glow discharge provides two important advantages for mass spectrometry analysis: cathode sputtering and Penning ionization. Cathode sputtering provides a direct means of obtaining a large number of atoms of representative composition directly from a solid sample; the Penning ionization process plays an important role in ionization out of spilled atoms into mass spectrometry.
principle
Glow discharge (GD) belongs to the phenomenon of gas discharge under low pressure and has historically been used as an effective atomization and ionization source for analysis. In the glow discharge mass spectrometer ion source, the sample to be tested is used as the cathode of the glow plasma light source. An inert gas (usually argon) is filled between the cathode and the anode, and the pressure is maintained at 10-1000 Pa. When a high voltage of 500 ~ 1500 V is applied to both ends of the electrode, Ar ionizes into electrons and Ar +, and Ar + accelerates to the cathode under the action of an electric field. The atoms of the cathode sample are stripped from the cathode sample (cathode sputtering) by the energy of 5-15 eV under the impact of argon ions, into the plasma until they reach the plasma, and the electrons in the plasma or metastable Ar atom collisions (Penning) ionization, become positive ions: M + e- → M + + 2 e-, M + Ar * a M + + Ar + e-. It has been demonstrated that Penning ionization in the GD source is the dominant ionization process.
Cathode sputtering products for the cathode material atoms, atomic groups, but also produce secondary and secondary electrons. Cathode sputtering process is precisely the sample atoms generated, but also for the depth of the sample can be the theoretical basis. The mechanism by which a large number of atoms, ions and electrons participate in the plasma collision process makes the glow discharge very complicated. Among the many areas formed by glow discharge, there are two areas of importance for sample analysis, the "negative glitch" and the "dark cathode area." The cathode dark area is a thin layer near the cathode surface with a high positive ion density. The voltage drop across the glow discharge is almost entirely applied to this area. Negative glow area generally occupy most of the volume of glow discharge, almost a field-free area, the electronic bear the role of conduction current. Therefore, secondary ions generated by sputtering are generally pulled back to the electrode surface to form deposition difficult to pass the dark cathode region, while the neutral atoms will be diffused into the negative brightness region is excited or ionized, of course, may also be frequent The collision is returned during the collision, which is an obvious feature of glow discharge. Glow discharge sources have the ability to produce atoms of a representative composition in a solid sample, along with the ability to generate excited and ionic states for these atoms. Therefore, glow discharge can be used as both a light source and an ion source for the content and depth analysis of solid samples. Glow discharge provides two important advantages for mass spectrometry analysis: cathode sputtering and Penning ionization. Cathode sputtering provides a direct means of obtaining a large number of atoms of representative composition directly from a solid sample; the Penning ionization process plays an important role in ionization out of spilled atoms into mass spectrometry.
