Compositionally graded Ba1−<i>x</i>Sr<i>x</i>TiO3 thin film for SIMS applications

A heterostructure of Ba1−xSrxTiO3/La1.1Sr0.9NiO3/SrTiO3 has been analyzed by magnetic sector secondary ion mass spectrometry (SIMS). The stoichiometry parameter x of the top layer was made varying continuously from 0 to 1 along the width of the sample by combinatorial pulsed laser deposition. Prior to SIMS analysis, the composition gradient of Ba1−xSrxTiO3 was quantitatively characterized by chemical characterizations including wavelength and energy dispersive x-ray spectroscopies. Even if the Ti content is constant into Ba1−xSrxTiO3, its ionic yield exhibits an increasing trend as Ba is substituted by Sr. Such a phenomenon can be explained by the variation of the neighboring atoms chemistry, which affects the ionization probability of titanium during the sputtering process. In addition to the continuously varying composition, the oxide multilayer sample features sharp interfaces hence the in-depth resolution under our analyzing conditions has been investigated too. The modeling of the interface crossing profiles reveals that the instrumental contribution to the profile broadening is as low as 5 nm.