RESUMEN
In this work we present the novel atomic models of the (1 1 0)-(16 × 2), (1 1 0)-c(8 × 10), (1 1 0)-(5 × 8) and (17 15 1)-(2 × 1) silicon surface reconstructions. The models are also valid for respective germanium surfaces. The dataset reports atomic coordinates for each surface reconstruction and related calculated bias-dependent scanning tunneling microscopy (STM) images. The data were obtained using the standard first-principles density functional theory calculations. The atomic models reported in this dataset are based on the universal building block for (1 1 0)-family silicon and germanium surfaces, proposed by R.A. Zhachuk and A.A. Shklyaev [1] and a vast number of STM data published in the literature. For comparison the data for the Si(1 1 0)-(16 × 2) older models by Stekolnikov et al. [2] and Yamasaki et al. [3] are also given. The presented models and related calculated scanning tunneling microscopy images allow to derive experimentally testable hypotheses and to interpret the experimental data. The reported atomic coordinates can be directly reused in other calculations related to Si(1 1 0) and Ge(1 1 0) surfaces provided that this work is cited.
RESUMEN
We report on the investigation of the atomic and electronic structures of a clean Si(331)-(12 × 1) surface using a first-principles approach with both plane wave and strictly localized basis sets. Starting from the surface structure proposed by Zhachuk and Teys [Phys. Rev. B 95, 041412(R) (2017)], we develop significant improvements to the atomic model and localized basis set which are critical for the correct description of the observed bias dependence of scanning tunneling microscopy (STM) images. The size mismatch between the Si pentamers from the surface model and those seen by STM is explained within the context of the Tersoff-Hamann model. The energy barriers that separate different Si(331) buckled configurations were estimated, showing that the surface structure is prone to dynamic buckling at room temperature. It is found that empty electronic states on Si(331) are essentially localized on the pentamers with interstitials and under-coordinated Si sp 2-like atoms between them, while filled electronic states are localized on under-coordinated Si sp 3-like atoms and dimers on trenches. The calculated electronic density of states exhibits two broad peaks in the fundamental bandgap of Si: one near the valence band top and the other near the conduction band bottom. The resulting surface bandgap of 0.58 eV is in an excellent agreement with spectroscopy studies.
RESUMEN
Currently an extensive range of noble metal colloidal nanocrystals (NCs) can be readily produced by diverse chemical methods. These nanomaterials present novel physical properties and can be regarded as building blocks to the nanofabrication of smaller, energy efficient and faster devices. Moreover, when these NCs are deposited on the surface of luminescent semiconductors, as it is the case of GaN-based heterostructures, exciton coupling with the metal plasmons may occur. In this work we report on the deposition of noble metal NC at the surface of InGaN/GaN multiple quantum wells (MQW), with efficient light emission in the visible range. We investigate the surface organization of Ag and Au NCs with sizes ranging from 5-30 nm as a function of deposition conditions. Scanning Electron Microscopy and Atomic Force Microscopy clearly showed that the metallic nanoparticles were successfully incorporated within the MQWs of the nitride semiconductors.