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(Te2+). The work was performed on a molecular beam epitaxy unit with desorption flow control by mass spectrometry and surface condition by fast electron diffraction. A molecular tellurium beam was obtained using a Knudsen type source. In this work, 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 of the order of 1.18 eV. At high temperatures (900 K), the proportion of Te monomers can reach 85%, and 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.