Physical Electronics and Materials, Faculty of Engineering, LondonSouth Bank University, 103 Borough Road, London SE1 0AA, U.K.

Abstract – We present a model that provides a description of the microwave dielectric loss in oxides. The dielectric loss (tan d) in single crystal and polycrystalline MgO and Al₂O₃ is measured over the temperature range 70-300 K. We are able to model the dielectric loss in terms of a 2-phonon difference model. There are two key parameters in this model: the third derivative, f_3, of the lattice potential and the linewidth, g, of the thermal phonons. In polycrystalline samples, rather than considering the different mechanisms of extrinsic loss, it is assumed that the main effect of extrinsic factors is a modification of the line width of the thermal phonons. By varying g(T) it is shown that the model can describe the loss in both single crystals and polycrystallines materials. In single crystal and polycrystalline MgO we use g as a fitting parameter. In single crystal and polycrystalline Al₂O₃ we obtain g(T) by Raman spectroscopy. The theory gives the right order of magnitude of the measured loss.

Pдr Rundqvist, Andrei Vorobiev¹⁾, Spartak Gevorgian^1,2)

¹⁾ Department of Microelectronics, Chalmers University of Technology, MC-2, SE-41296 Gцteborg, Sweden
²⁾ Microwave and High Speed Electronics research center, Ericsson AB, 43184 Moelndal Sweden

Abstract – The microstructure, surface morphology and interfaces of Ba_1-XSr_XTiO₃(BST)/SiO₂/Si and Ba_1-XSr_XTiO₃/Pt/Au/Pt/TiO₂/SiO₂/Si multilayer structures have been studied using Transmission Electron Microscope, X-Ray Diffraction, Atomic Force Microscopy and Electron Diffraction Spectroscopy. The Ba_1-XSr_XTiO₃ films are grown at 800 °C on an amorphous SiO₂/Si template and reveal a textured structure where the BST(110) dominant phase has minimum surface energy. Pt/Au layers annealed at 650 °C show polycrystaltextured structures with (111) dominant orientation. The BST films deposited at 650 °C on a Pt/Au/Pt/TiO₂/SiO₂/Si template reveal a poly-crystal column-textured structure of dominantly BST(111) and BST(110) phases growing through quasi-epitaxial and self-assembled mechanisms, respectively. Both phases of BST (111) and (110) are subject of compressive in-plane strain. The lateral grain sizes of the BST film increases with increasing deposition temperature in the range 600-800 °C. The BST/Pt/Au interface area contains the intermediate layer with thickness of 10-20 nm. The correlation between orientation, strains, grain sizes, interface dead layer and dielectric response of BST films are discussed.