Ion beam modification of Gd 2Ti 2O 7

Abstract

Irradiation of Gd 2Ti 2O 7 with 3 MeV Ar + ions results in expansion of the unit cell volume and irradiation-induced amorphization. The damage cross section for amorphization determined from X-ray diffraction data is 0.023 nm 2. Transmission electron microscopy and electron diffraction confirm the irradiation-induced amorhous character at high fluences. Raman spectroscopy indicates a decrease in scattered intensity and an increase in linewidth with fluence for the principal vibrational modes, consistent with increasing-induced disorder. The wave number of the most intense Raman peak at ≈310 cm −1 (attributed to the O-Gd-O bending mode) decreases with fluence, indicating a change in bond angle. The increase with fluence in the wave number of the Raman peak at ≈ 515 cm −1 (attributed to the Gd-O stretching mode) suggests a decrease in this bond length. At intermediate fluences, a forbidden peak at ≈ 765 cm −1 becomes slightly activated by irradiation-induced disorder on the cation sites.