Thin film dielectrics have been and still remain a key component in the semiconductor industrial pipeline. Gaining an understanding of the properties of complex amorphous and crystalline oxides will facilitate their implementation in future technologies. Here, we investigate the effects of dopants on the dielectric and structural properties of various amorphous and crystalline thin films deposited using 90 degree off-axis magnetron co-sputtering. We first explore the composition dependence of the dielectric properties of Zr-Al-O and Zr-Si-O to determine the effect of the presence or absence of crystallinity on the dielectric constant and the breakdown field of these materials. We then study the composition dependence of the dielectric and the structural properties of Ta-Ge-O and Ta-Si-O. We find that doping a small amount of GeO2 into Ta2O5 greatly enhances the dielectric constant, with a maximum dielectric constant of εr ∼34 at a Ta cation fraction of 0.97. In contrast, SiO2 doping into Ta2O5 does not elicit such an effect. We determine that the enhancement observed in Ta-Ge-O is due to an enhancement in the ionic polarizability. We follow with a study which probes the atomic structure of amorphous Ta2O5 and Ta-Ge-O thin films by systematically applying high energy x-ray diffraction and absorption techniques as well as computational simulations. The diffraction and absorption studies were greatly facilitated in part, by depositing the composition spreads onto amorphous silicon nitride membranes. Finally, we co-deposit several technologically relevant dielectrics—Hf-Si-O, Hf-Ge-O, Ta-Sn-O, and Nb-Ge-O—to study their dielectric and structural properties as a function of composition and to test whether the type of dielectric behavior observed in the Ta-Ge-O system is a more widespread phenomenon.