Xe bubbles in si observed by extended x-ray-absorption fine-structure spectroscopy

We report the first experimental investigation of Xe bubbles in Si single crystals by extended x-ray-absorption fine-structure (EXAFS) spectroscopy. Measurements have been performed on the Xe L₃ edge at 70 and 300 K, on both as-implanted and annealed samples. Implanted doses up to 10¹⁷ atoms/cm² have been investigated. The as-implanted samples did not show any EXAFS structure, revealing that the gas is randomly diffused in the host matrix either in an atomic configuration or in small gaslike aggregates. By way of contrast, annealed samples show an EXFAS structure due to the presence of Xe bubbles in the fcc crystalline phase. The observation of a temperature-dependent average Xe-Xe nearest-neighbor distance in the bubbles is shown to be related to the overpressure on the bubbles due to the host matrix. These results are in excellent agreement with independent thermodynamic calculations.