7,358 research outputs found
Real-time monitoring of stress evolution during thin film growth by in situ substrate curvature measurement
Strain engineering is the art of inducing controlled lattice distortions in a
material to modify specific physicochemical properties. Strain engineering is
applied for basic fundamental studies of physics and chemistry of solids but
also for device fabrication through the development of materials with new
functionalities. Thin films are one of the most important tools for strain
engineering. Thin films can in fact develop large strain due to the crystalline
constrains at the interface with the substrate and/or as the result of specific
morphological features that can be selected by an appropriate tuning of the
deposition parameters. Within this context, the in situ measurement of the
substrate curvature is a powerful diagnostic tool allowing a real time
monitoring of the stress state of the growing film. This manuscript reviews a
few recent applications of this technique and presents new measurements that
point out the great potentials of the substrate curvature measurement in strain
engineering. Our study also shows how, due to the high sensitivity of the
technique, the correct interpretation of the results can be in certain cases
not trivial and require complementary characterizations and an accurate
knowledge of the physicochemical properties of the materials under
investigation
Strain engineering in graphene by laser irradiation
We demonstrate that the Raman spectrum of graphene on lithium niobate can be controlled locally by continuous exposure to laser irradiation. We interpret our results in terms of changes to doping and mechanical strain and show that our observations are consistent with light-induced gradual strain relaxation in the graphene layer
Strain engineering in Ge/GeSn core/shell nanowires
Strain engineering in Sn-rich group IV semiconductors is a key enabling
factor to exploit the direct band gap at mid-infrared wavelengths. Here, we
investigate the effect of strain on the growth of GeSn alloys in a Ge/GeSn
core/shell nanowire geometry. Incorporation of Sn content in the 10-20 at.%
range is achieved with Ge core diameters ranging from 50nm to 100nm. While the
smaller cores lead to the formation of a regular and homogeneous GeSn shell,
larger cores lead to the formation of multi-faceted sidewalls and broadened
segregation domains, inducing the nucleation of defects. This behavior is
rationalized in terms of the different residual strain, as obtained by
realistic finite element method simulations. The extended analysis of the
strain relaxation as a function of core and shell sizes, in comparison with the
conventional planar geometry, provides a deeper understanding of the role of
strain in the epitaxy of metastable GeSn semiconductors
Multi-scale approach for strain-engineering of phosphorene
A multi-scale approach for the theoretical description of deformed
phosphorene is presented. This approach combines a valence-force model to
relate macroscopic strain to microscopic displacements of atoms and a
tight-binding model with distance-dependent hopping parameters to obtain
electronic properties. The resulting self-consistent electromechanical model is
suitable for large-scale modeling of phosphorene devices. We demonstrate this
for the case of an inhomogeneously deformed phosphorene drum, which may be used
as an exciton funnel
Fermi Velocity Modulation in Graphene by Strain Engineering
Using full-potential density functional theory (DFT) calculations, we found a
small asymmetry in the Fermi velocity of electrons and holes in graphene. These
Fermi velocity values and their average were found to decrease with increasing
in-plane homogeneous biaxial strain; the variation in Fermi velocity is
quadratic in strain. The results, which can be verified by Landau level
spectroscopy and quantum capacitance measurements of bi-axially strained
graphene, promise potential applications in graphene based straintronics and
flexible electronics.Comment: 4 pages, 3 figures. SOLID STATE PHYSICS: Proceedings of the 57th DAE
Solid State Physics Symposium 2012, Indian Institute of Technology Bombay,
Mumbai, India, 3-7 December 2012, Editors: A. K. Chauhan, Chitra Murli and S.
C. Gadkar
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