Where Is the Unmatched Transition Metal in Substoichiometric Diboride Line Compounds

The atomic structure and local composition of high quality epitaxial substoichiometric titaniumdiboride (TiB1.9) thin film, deposited by unbalanced magnetron sputtering, were studied usinganalytical high-resolution scanning transmission electron microscopy, density functional theoryand image simulations. The unmatched Ti is pinpointed to planar defects on {1-100} prismaticplanes and attributed to the absence of B between Ti planes that locally relaxes the structure.This mechanism allows the line compound to accommodate the off-stoichiometry and remaina line compound between defects. The planar defects are embedded in otherwise stoichiometricTiB2 and are delineated by insertion of dislocations. An accompanied decrease in Ti-Ti bondlengths along and across the faults is observed.Introduction