Hydrogen segregation at the Al/Si(1 1 1) interface

The density depth profile of hydrogen trapped at an epitaxial solid-solid interface has been measured by neutron reflection. The interface was between a Si(1 1 1) substrate and an epitaxial film of Al 1500 Å thick, into which hydrogen was introduced by low-energy implantion. The measurements, carried out at room temperature, indicated that a total of 0.7 × 1016 H atoms/cm2 were trapped at the interface. This number corresponds approximately to one atomic layer of liquid hydrogen; however, hydrogen was found to be spread over a thickness of 60 Å. Cooling the sample from room temperature to 220 K did not significantly alter the distribution of hydrogen trapped at the interface. © 1998 Published by Elsevier Science B.V.