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By hybrid density functional theory, we have investigated anisotropies in the electronic, optical, and mechanical properties of the body centered tetragonal C4 phase of carbon. We predict a strong electronic anisotropy associated with the in-plane carbon-carbon covalent bonds and the zigzag carbon chains along the c-direction (out-of-plane), which results in a state-resolved directional distribution of valence electrons at the top of the valence band. The calculated adsorption spectra display highly anisotropic features which are already manifested at ambient pressure by a substantial difference (2 eV) for the absorption edges between the in-plane and out-of-plane components of the tetragonal cell. Similar anisotropic features in the elastic compressibility are also discussed. [ABSTRACT FROM AUTHOR]

Bi3.15Nd0.85Ti3O12 thin films of two different preferred orientations were sol-gel grown on Pt/Ti/SiO2/Si. Using different heating rates during crystallization, either films containing 65% columnar grains with (104)/(014) orientation or fine-grained films with a predominant c-axis orientation were obtained. Anisotropic ferroelectric and piezoelectric properties were determined, with a remanent polarization 2Pr=46.4 μC/cm2 and a piezoelectric coefficient d33=17 pm/V in a predominantly (104)/(014)-oriented film, but only 2Pr=16.7 μC/cm2 and d33=5 pm/V in a predominantly c-axis-oriented film. These values confirm that the polarization vector of this material is close to the crystallographic a axis. [ABSTRACT FROM AUTHOR]

Polycrystalline Bi3.15Nd0.85Ti3O12 (BNdT) thin films of a-axis preferential orientation [α(100)=62%] and high c-axis orientation [α(001)=96%] were fabricated directly on Pt/Ti/SiO2/Si substrates through a sol-gel process. We observed strong dependences of ferroelectric and dielectric properties on the film orientation, with a remanent polarization 2Pr of 39 μC/cm2 and dielectric constant [variant_greek_epsilon]r of 343 at 100 kHz in the a-axis oriented film; 2Pr of 20 μC/cm2 and [variant_greek_epsilon]r of 331 in the film of random orientation; and 2Pr of 13 μC/cm2, [variant_greek_epsilon]r of 218 in the highly c-axis oriented film. Furthermore, the 2Pr value of a purely a-axis-oriented BNdT film can be predicted to be ∼51 μC/cm2. The large anisotropy of 2Pr and [variant_greek_epsilon]r values demonstrates that the polarization vector of BNdT is close to the a axis. [ABSTRACT FROM AUTHOR]

A correction to the article "Anisotropic ferro- and piezoelectric properties of sol-gel grown Bi3.15Nd0.85Ti3O12 films with two different orientations on Pt/Ti/SiO2/Si" that was published in previous issue is presented.