Lattice relaxation induced by electronic excitation in Al2O3

Transient volume change induced by irradiation with an electron pulse of alpha -Al 2 O 3 and Cr doped Al 2 O 3 have been measured above 77K. It is found that the volume change induced in alpha -Al 2 O 3 shows a single exponential decay with a lifetime of 12 ms below 140K and that the initial value of the volume change is a linear function of the electron fluence and is not influenced by doping with Cr 3+ . It is suggested that the transient volume change observed in alpha -Al 2 O 3 is associated with the relaxed excited state resulting from fundamental electronic excitation, possibly the self-trapped exciton.