Determination of the Ratio of Atoms and Molecules in a Tellurium Beam Using a Mass Spectrometer

Abstract

The work is devoted to clarifying the ratio of atoms and molecules of tellurium vapor in interaction with various metal substrates (copper, nickel). Atoms (Te) and molecules (Te₂) present in the tellurium vapor phase in mass spectrometric measurements correspond to ion currents of monomers J(Te⁺) and dimers J(\({\text{Te}}_{2}^{ + }\)). The work is performed on a molecular beam epitaxy unit with desorption flow control by mass spectrometry and surface condition by reflection high-energy electron diffraction (RHEED). A molecular tellurium beam is obtained using a Knudsen type source. It is shown that the proportion of monomers in the total desorption beam significantly depends on the temperature of the substrate. This dependence corresponds to the dissociation energy of Te₂ molecules on the order of 1.18 eV. At high temperatures (900 K), the proportion of Te monomers can reach 85%; at low temperatures (650 K), 8%. This circumstance should be taken into account when the composition of the vapor phase from the beam source can affect the processes under study. In particular, in mass spectrometric studies of the interaction of the vapor phase with the surface of a solid, for example, in the process of molecular beam epitaxy of CdTe.