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MedeA® Application Notes for Electronics
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In the design of substrates for the epitaxial growth of InxGa1-xN alloys it is useful to know the elastic properties of the semiconductor as a function of composition. This application note shows the use of MedeA® with VASP 5.2 and the mechanical-thermal (MT) module in computing these properties. Judging by the results for the binaries GaN and InN, the level of accuracy is comparable with that achieved in experiments. 
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First-principles calculations reveal a three-fold increase in the Young’s modulus of graphite as it is lithiated (C→LiC₆). A linear expression is determined that describes the approximate stiffness of Li intercalated graphite as a function of loading which may lead to greatly improved continuum models of electrode deformation and failure. 
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A key process in the semiconductor manufacturing is the reactive adsorption of molecules such as silane (SiH4) and dichlorosilane (SiCl2H2) on the surfaces of silicon wafers. This case study demonstrates the calculation of the geometry of a silane molecule on a reconstructed Si(001) surface. 
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First-principles computations correctly describe the ferroelectric distortions and the macroscopic polarization of BaTiO₃ in agreement with experiment. Computations of the vibrational properties (phonons) reveal that a cubic perovskite structure of BaTiO₃ becomes stable under compression of the lattice. This demonstrates the usefulness of first-principles calculations in the design and optimization of ferroelectric materials. 
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The work function of the metal gate in a CMOS stack depends on the composition and structure of the interfaces. This is demonstrated here for the case of a Si-HfO2-W stack by introducing a Hf vacancy at the Si/HfO2 interface. At a concentration of 1.2 vacancies per nm2 the work functions is increased by 500 meV. 
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Elemental germanium is a semiconductor with a measured indirect band gap of 0.66 eV. Using a hybrid functional as implemented in VASP 5.2, the computed value is 0.66 eV while standard density functional approaches incorrectly predict Ge to have no band gap. Other features of the band structure such as the direct gap at Γ are also well reproduced by the current level of theory, namely 0.8 eV (measured) and 0.73 eV (computed), thus demonstrating the reliability of this level of approach in predicting energy band structures. This sets the stage for using computations to modify the band structure for example by uniaxial strain to meet specific design criteria. 
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