Study of iridium/germanium interaction in a lateral diffusion couple

Ion beam analysis using micro-Rutherford backscattering spectrometry has been used to investigate the interaction between germanium and iridium in a lateral diffusion couple. Optical microscopy, scanning electron microscopy and atomic force microscopy have also been employed. When samples of germanium islands on iridium films are annealed within a range of temperatures between 600 to 800 °C, substantial lateral diffusion is observed, resulting in a number of reaction regions. Micro-Rutherford backscattering analysis indicates that the phase Ir₃Ge₇ stretches across the original island interface at all temperatures, with the phase Ir₄Ge₅ forming in the reaction region with unreacted iridium. The phase IrGe₄ is observed to nucleate in the middle of the island at temperatures above 800 °C. Depth information is readily obtainable from micro-Rutherford backscattering spectrometry which is used in conjunction with atomic force microscopy data to estimate the densities of the phases formed. The results demonstrate the complementary nature of the techniques used for studying lateral diffusion couples.