Identification of alkali metal clusters by field desorption
D.P. Bernatsky, V.G. Pavlov
Ioffe Institute
DOI: 10.26456/pcascnn/2025.17.795
Original article
Abstract: The formation of clusters of potassium and cesium atoms on the surface of tungsten and rhenium crystals has been studied. The study was carried out using field electron microscopy, field desorption microscopy, and time-of-flight mass analysis of ions desorbed by an electric field. To determine the masses, particles adsorbed on the sample surface were desorbed with a high-voltage pulse lasting several ns, and the ion flight time from the sample to the detector was measured. The experiments were carried out in an ultrahigh vacuum (p < 10-9 Torr). Alkali metal atoms were deposited on the surface of tungsten and rhenium field emitters from an external spray. As a result of the measurements, not only monatomic alkali metal ions were detected, but also cluster ions containing up to seven atoms. The number of ions of each mass depended on the electric field strength on the surface of the emitters. As the field strength increases, the number of monatomic ions increases slightly at first and then decreases. In the opposite way, the number of cluster ions depends on the field strength. As the field increases, the number of cluster ions initially decreases, then increases. When a certain value of the field strength is reached, the emission of both monatomic and cluster ions stops. The described patterns are probably related to the movement of the field desorption zone, and, accordingly, the cluster identification area along the surface of the tip-shaped sample. The number of desorbed cluster ions reflects the cluster distribution over the sample surface. At low field strengths, ions are desorbed only from the area near the tip apex. This area consists of a densely packed crystal plane and wide steps surrounding this plane. As the tension increases, the desorption zone expands and passes through the rounded area of the surface between the flat faces, and the number of cluster ions
decreases. Then, desorption begins from the lateral faces and steps, and the number of ion clusters being desorbed increases. Thus, it can be assumed that clusters are predominantly formed and located on a surface with steps of densely packed planes.
Keywords: adsorption, cesium, potassium, tungsten, rhenium, electric field, ions
- Dmitrii P. Bernatsky – Ph. D., Docent, Senior researcher, Ioffe Institute
- Victor G. Pavlov – Dr. Sc., Senior researcher, Ioffe Institute
For citation:
Bernatsky D.P., Pavlov V.G. Identifikatsiya klasterov shchelochnykh metallov s pomoshchyu polevoj desorbtsii [Identification of alkali metal clusters by field desorption], Fiziko-khimicheskie aspekty izucheniya klasterov, nanostruktur i nanomaterialov [Physical and chemical aspects of the study of clusters, nanostructures and nanomaterials], 2025, issue 17, pp. 795-804. DOI: 10.26456/pcascnn/2025.17.795. ⎘
Full article (in Russian): download PDF file
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