Using a tolerance factor approach, it was predicted that xBiScO3–(1−x)BaTiO3 will have a morphotropic phase boundary that should enhance both the polarizability and permittivity, relative to the BiScO3 end member, near a composition of x=0.4. To verify this prediction, pulsed laser deposition was used to grow xBiScO3–(1−x)BaTiO3 thin films on (100) SrRuO3∕LaAlO3 and Pt-coated Si substrates. Typical growth conditions were 700°C and 100mTorr O2∕O3. The perovskite structure was found to be stable for compositions of x=0.2–0.6 in epitaxial films, with reduced stability in polycrystalline films. The temperature where the maximum permittivity occurs rises as BiScO3 is added to BaTiO3, and increasingly relaxorlike behavior is observed with increasing BiScO3 content. Room temperature permittivity values ranged from 200 to 400, with loss tangents of ∼0.1 at 10kHz. The experimental morphotropic phase boundary occurs near x=0.4. 0.4BiScO3–0.6BaTiO3 showed a broad permittivity maximum near 800 from 150–275°C. Films with x=0.4 show a coercive field of about 200kV∕cm with a modest room temperature remanent polarization near 8μC∕cm2. The films exhibit a dielectric tunability of greater than 25% at fields of ∼500kV∕cm. The combination of high polarizability and high transition temperature makes this family an interesting base composition for lead-free piezoelectrics, especially if the degree of relaxor character could be reduced.

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The heteroepitaxial growth of Ge on thin Si membranes can lead to significant bending under self-assembled Ge hut nanostructures. Undercut silicon-on-insulator mesas approximate a Si freestanding membrane and serve as a crystalline substrate for the growth of Ge huts. Synchrotron x-ray microdiffraction shows a local curvature on the lateral scale of the size of the hut and an overall bending of the freestanding region. In comparison with conventional mechanically rigid substrates, the freestanding film can bend significantly. We have found a local radius of curvature of 6μm beneath huts on 30-nm-thick Si membranes.