 Hydrogen is employed to saturate broken ( " dangling " ) bonds of amorphous silicon and amorphous carbon that helps stabilizing material properties . It is also a potential electron donor in various oxide materials , including ZnO , SnO2 , CdO , MgO , ZrO2 , HfO2 , La2O3 , Y2O3 , TiO2 , SrTiO3 , LaAlO3 , SiO2 , Al2O3 , ZrSiO4 , HfSiO4 , and SrZrO3 . 
