Raffaele Resta

NON-NOMINAL VALUE OF THE DYNAMICAL EFFECTIVE CHARGE IN ALKALINE-EARTH OXIDES

We calculate ab initio the electronic states and the Born dynamical charge

Control of Ge homojunction band offsets via ultrathin Ga–As dipole layers

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Can We Tune the Band Offset at Semiconductor Heterojunctions

of the alkaline-earth oxides in the local-density approximation. We investigate the trend of increasing

Band offsets engineering at semiconductor heterojunctions

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Band Offsets at Semiconductor Heterojunctions: Bulk or Interface Properties?

values through the series, using band-by-band decompositions and computational experiments performed on fake materials with artificially modified covalence. The deviations of

AB INITIO STUDY OF PIEZOELECTRICITY AND SPONTANEOUS POLARIZATION IN ZNO

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Towards a quantum theory of polarization in ferroelectrics: The case of KNbO3.

from the nominal value 2 are due to the increasing interaction between O 2p orbitals and unoccupied cation d states. We also explain the variations, along the series, of the individual contributions to

Local interface composition and band discontinuities in heterovalent heterostructures.

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Role of covalent bonding in the polarization of perovskite oxides: The case of KNbO3.

arising from the occupied band manifolds.

Ab initio calculation of phonon dispersions in II-VI semiconductors.

We have created 0.35–0.45 eV band offsets at Ge homojunctions using Ga–As dipole intralayers, with the Ge valence band edge on the As side of the junction at lower energy. This is, to our knowledge, the first time that intralayer control of band discontinuities is extended to homojunctions, thereby expanding the potential domain of band gap engineering. Because these offsets occur over just a few atomic spacings, they rival heterojunction band edge discontinuities in breadth. The offsets were measured with synchrotron‐radiation photoemission spectroscopy. Similar band offset magnitudes occur for both ‘‘Ga‐first’’ and ‘‘As‐first’’ growth sequences, consistent with a truly dipolar effect. Both cleaved Ge(111) and thick ≊50 A Ge films deposited on cleaved Ge(111) were used as substrates, obtaining consistent results. The sign and magnitude of the effect is in agreement with a ‘‘theoretical alchemy’’ model. Experimental evidence of microdiffusion is discussed.