Imaging of microwave permittivity, tunability, and damage recovery in (Ba, Sr)TiO3 thin films

We describe the use of a near-field scanning microwave microscope to quantitatively image the dielectric permittivity and tunability of thin-film dielectric samples on a length scale of 1 mu m. We demonstrate this technique with permittivity images and local hysteresis loops of a 370-nm-thick Ba0.6Sr0.4TiO3 thin film at 7.2 GHz. We also observe the role of annealing in the recovery of dielectric tunability in a damaged region of the thin film. We can measure changes in relative permittivity epsilon(r) as small as 2 at epsilon(r) = 500, and changes in dielectric tunability d epsilon(r)/dV as small as 0.03 V-1. (C) 1999 American Institute of Physics. [S0003-6951(99)00446-5].