Ion beam analysis of the interaction between platinum and germanium

When samples of germanium islands on platinum films are annealed within a range of temperatures between 400 and 600 °C, substantial lateral diffusion is observed, resulting in several distinct phase regions.This work is a continuation of previous work carried out by Nemutudi et al. (Thin Solid Films, 358 (2000) 270). The previous work employed Rutherford backscattering spectrometry on the nuclear microprobe (μRBS) to study the lateral diffusion couple interaction between platinum and germanium. We have successfully used particle induced X-ray emission on the nuclear microprobe (μPIXE) to study the lateral diffusion couple interaction of the same binary system. Both stoichiometric and lateral phase growth information was extracted using μPIXE. Our study also includes the use of μRBS, the results of which are compared with the μPIXE results on the same samples. Our successful use of μPIXE extends the range of possible systems that can now be studied on the microprobe, since the effective use of RBS is limited to couples of elements that are not too close in atomic number and therefore do not produce excessive RBS peak overlap. The present lateral diffusion couple work also goes further than the previous work by including a study of the kinetics of the interaction; the activation energies determined from the lateral growth rates of Pt2Ge3, PtGe and PtGe2 phase regions were, 0.9 ± 0.1, 1.3 ± 0.4 and 1.5 ± 0.2 eV, respectively. Scanning electron microscopy (SEM) and optical microscopy were also employed in the lateral diffusion couples study. We demonstrate the complementary use of the techniques used.The movement of a thin layer of Ti, used as an inert marker during the formation of Pt2Ge, was monitored. Previously it was only determined that Pt was the dominant diffusing species. We have carried out a quantitative determination of the atomic diffusion ratio of Pt to Ge across the marker and found it to be 4 to 1.