Electronic structure of aluminium trihydride studied using soft x-ray emission and absorption spectroscopy

We have performed soft x-ray emission spectroscopy (SXES) and soft x-ray absorption spectroscopy (SXAS) experiments on aluminum hydride alpha-AlH(3). The occupied and unoccupied electronic states of the Al 3p partial density of states are obtained experimentally. By comparing the data from Al metal and alpha-AlH(3), a band gap with a few eV is found for alpha-AlH(3). In addition, the occupied states of alpha-AlH(3) have a larger spectral intensity than that of Al metal, indicating an increase in the number of electrons with the Al 3p character through Al-H bond formations. The results of a band-structure calculation account for the formation of the energy gap and the increase of the Al 3p electrons qualitatively. This suggests that a covalent-like nature is important to the Al-H bond in alpha-AlH(3).