Analysis of the distribution of oxygen in the surface layers of metals on the basis of emission of photons by sputtered molecules of oxides

Abstract

Iatoms and ions of metals included in the composition of the spattered matter. Consequently, IPS makes it possible to carry out the qualitative and quantitative analysis of the content of these elements in various materials. However, the atoms of nonmetals, especially oxygen, are not excited and do not contribute to optical emission. The presence of oxygen in the surface layers can be estimated indirectly on the basis of its effect on the intensity of the lines of other elements of the bombarded surface (on the basis of the so-called "chemical" effect [2]). In this article, we propose a method of direct determination of the oxygen content on the basis of the radiation of spattered molecular oxideS. However, the number of data on molecular bands suitable for diagnostics purposes examination, in ion bombardment, of bright is very small. Previous studies contained only the data on the emission of MoO [3, 4] and HoO [5] bands in ion bombardment of molybdenum and holmium in the presence of oxygen. In this work, we examined the new molecular bands detected in the radiation spectra of the sputtered particles and demonstrated the possibilities of the layer analysis of the distribution of oxygen in the surface layers of metals by the IPS method, l We examined the emission spectra formed in ion bombardment of the transition metals Ti, V, Cr, Zr, Nb, Mo, Fe, Ni, Hf, Ta, W and rare-earth metals Gd, Tb, Ho, Tm, and Yb. The objects were selected on the basis of the fact that the ion bombardment of these metals (the elements with the empty d- or f-shells) the optical emission spectra show the so-called continuous emission which depends strongly on the presence of oxygen on the surface [6]. In addition to this, examination of secondary ion emission from the surface of various oxides showed that the intensity of the sputtered ions of the MeO + type for the transition metals is an order of magnitude higher, and for the rare-earth metals two orders of magnitude higher than for other elements [7]. Sputtering was carried out with K + ions with an energy of E = I0 keV and the current density of j - 0.2 mA/cm 2. The pressure of the residu~l,gases in operation of the ion source did not exceed 5"10 -6 Pao The amount of oxygen adsorbed on the bombarded surface was varied by increasing its pressure in the target area from minimum, corresponding to the pressure of residual gases, to 2"10 -3 Pa. The measurements were taken in the conditions of the steady interaction ~etween the ion beam and the surface. The emission emitted by the excited partitles flying away from the surface was analyzed in MDR-2 diffraction monochromator and recorded in a photoelectronic system using FEIJ-106 cooled photoelectronic multiplier (Fig. i). The corona glow caused by ion bombardment of the target was displaced from the vacuum chamber through a quartz window. Using a quartz lens, the image of the corona was focused on the input slit of the monochromator. The monochromator and the lens were placed in position in which their optical axes coincided and were parallel to the bombarded surface. Feeding oxygen to a pressure of 1-2"10 -3 Pa resulted in the uniform coating of the metal surface with the adsorbed oxygen atomsl the coating was equal approximately to the monolayer coating. This was accompanied by effective sputtering of the bombarded surfaces in the form