Hydrogen segregation and trapping in the Al/Si(111) interface.

Abstract

A quantitative measurement of hydrogen trapping in an undisturbed solid-solid interface is reported. Trapping and segregation of hydrogen was found to occur at the semicoherent interface between Si(111) substrates and 1500-\AA{}-thick epitaxial Al films. Ion-beam-analysis techniques were used to measure the depth profile of the trapped hydrogen. Up to 1.7\ifmmode\times\else\texttimes\fi{}${10}^{16}$ H atoms/${\mathrm{cm}}^{2}$ were found to be trapped in the interface. The hydrogen was introduced by 500-eV ion implantation into the surface of the Al layer to avoid any radiation damage at the interface. The amount of trapped hydrogen was found to increase with implantation dose, without saturating. The thickness of the hydrogen-containing layer was less than 13 nm. In ramp annealing at least 70% of the trapped hydrogen was released from the interface in an abrupt stage near 390 K; a smaller release stage occurred at 150 K. The detrapped hydrogen was found to have left the sample. The annealing in the stage at 390 K obeyed first-order kinetics with an activation energy of 0.96\ifmmode\pm\else\textpm\fi{}0.06 eV. Analysis of the annealing data was used to derive the binding enthalpy and entropy of H in the interface relative to solution in the Al as 0.53\ifmmode\pm\else\textpm\fi{}0.06 eV and (-4.0\ifmmode\pm\else\textpm\fi{}1.9)k.