F. La Via

Mechanisms of growth and defect properties of epitaxial SiC

In the last ten years, large improvements in the epitaxial silicon carbide processes have been made. The introduction of chloride precursors, the epitaxial growth on large area substrate with low defect density, the improvement of the surface morphology, the understanding of the chemical vapour deposition (CVD) reactions, and epitaxial mechanisms by advanced simulations are just the main results obtained in the homo-epitaxy process of 4H-SiC. After this large stride in the process of SiC epitaxial growth, it is time to collect this knowledge in a review that can be a reference point for the future work in this interesting field. The structure of the review is the following. After an introduction on the evolution and history of the epitaxial growth of 4H-SiC, the main physics parameter of this epitaxial growth process is explained in detail using the traditional Burton-Cabrera-Franck theory and the experimental observations of the surface instability due to the off-axis growths. Then the introduction of ch...

Electron backscattering from stacking faults in SiC by means ofab initioquantum transport calculations

We study coherent backscattering phenomena from single and multiple stacking faults (SFs) in 3C- and 4H-SiC within density functional theory quantum transport calculations. We show that SFs give rise to highly dispersive bands within both the valance and conduction bands that can be distinguished for their enhanced density of states at particular wave number subspaces. The consequent localized perturbation potential significantly scatters the propagating electron waves and strongly increases the resistance for

Study of the role of particle-particle dipole interaction in dielectrophoretic devices for biomarkers identification

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Micro-Raman Analysis of a Micromachined 3C-SiC Cantilever

-doped systems. We argue that resonant scattering from SFs should be one of the principal degrading mechanisms for device operation in silicon carbide.

4H-SiC defects evolution by thermal processes

A three dimensional Coupled Monte Carlo-Poisson method has been used to evaluate the impact of particle-particle dipole interactions in the equilibrium distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. We compare the simulated distributions with experimental ones both for micro-(MDA-MB-231 breast tumor cells) and nano-(multiwall carbon nanotubes) particles. In both cases the equilibrium distributions near the electrodes are dominated by dipole interactions which locally enhance the DEP effect and promote long particles chains.

Monte Carlo study of the early growth stages of 3C-SiC on misoriented and 6H-SiC substrates: role of step-island interaction

In this work, Raman microscopy is used to study the stress distribution on 3C-SiC cantilevers. Also we compare the strain distribution observed on the microstructure, using the shift of the transverse optical (TO) mode in micro-Raman maps, with the values predicted using a recent analytic theory [1]. Along the width of the cantilever is observed a reduction of stress ascribed to the etching processes that removes a thin layer of the interface between the 3C-SiC film and the substrate close to the edge of the microstructure. It is possible to show that this variation can be ascribed to a non-linearity of the strain field along the 3C-SiC film thickness. Also, helped by Finite Element Modelling (FEM), we determined the stress tensor along the cantilever. This result shows that, for a complete stress description of the cantilevers, it is necessary taking into account the role of diagonal and off-diagonal stress tensorial components.

Optical characterization of bulk mobility in 3C‐SiC films grown on different orientation of Si substrates

4H-SiC defects evolution after thermal processes has been evaluated. Different annealing temperatures have been used to decrease the defect density of epitaxial layer (as stacking faults) and recover the damage occurred after ion implantation. The propagation of defects has been detected by Photoluminescence tool and monitored during the thermal processes. The results show that implants do not affect the surface roughness and how a preliminary annealing process, before ion implantation step, can be useful in order to reduce the SFs density. It shown the effect of tuned thermal process. A kind of defect, generated by implant and subsequent annealing, can be removed by an appropriate thermal budget, while others can increase. A fine tuning of thermal process parameters, temperature and timing, is useful to recover the crystallographic quality of the epilayer and increase the yield of the power device.

Micro-Raman analysis and finite-element modeling of 3 C-SiC microstructures

In this paper, we use three-dimensional kinetic Monte Carlo simulations on superlattices to study the hetero-polytypical growth of cubic silicon carbide polytype (3C-SiC) on hexagonal 6H-SiC step-bunched substrates with miscuts towards the and directions. We find that the preferential 3C conversion observed on misoriented substrates could be due to a different step-to-island interaction which enhances island stability and expansion in this specific direction. For this reason 3-4 degrees off step-bunched 6H substrates with miscut towards the direction should be the best choice for the stable and reproducible hetero-polytypical growth of high quality cubic epitaxial films. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural and electronic transitions in Ge2Sb2Te5 induced by ion irradiation damage

Raman microscopy has been used to study the carrier concentration and mobility in n‐doped 3C‐SiC epilayers grown on different silicon substrates, namely (100) Si and (111) Si on axis and off‐axis towards the [110] direction. By analyzing the longitudinal optical phonon‐plasmon coupled mode (LOPC), we were able to estimate the 3C‐SiC electron bulk mobility (μ) within the range between 5 and 500 cm2/Vs. The carrier concentration (n) was ranging from 2×1016 to 6×1018 cm−3. The observed trend shows a reduction in the electron mobility as the carrier concentration increases for films grown on any substrate considered, accordingly to the existent theory. For equal values of doping concentration, 3C‐SiC epitaxial films grown on (100) Si substrates show a higher mobility than films grown on (111) Si counterparts. This could be ascribed to a higher defect density in (111) Si samples. A deeper characterization by performing Raman maps shows a broadening and a splitting of the 3C‐SiC transverse optical (TO) peaks fo...