  The structural and electronic properties of the hydrides of silicene and
germanene have been studied using ab initio calculations. The trend for the M-H
(M=C, Si, Ge) bond lengths, and corresponding bond energies, is consistent with
the atomic size trend, and comparable to those of MH_4 hydrides. Band
structures were also obtained for the buckled configuration, which is the
stable form for both silicene and germanene. Upon hydrogenation, both silicane
(indirect gap) and germanane (direct gap) are semiconducting.
