Marco Salvalaglio

Marco Salvalaglio
Technische Universität Dresden | TUD · Institute of Scientific Computing & Dresden Center for Computational Materials Science

PhD

About

81
Publications
8,438
Reads
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880
Citations
Introduction
I'm a theoretical material scientist, working at the crossroads between solid-state physics, computational material science and applied mathematics. My research focuses on the modeling and simulation of material properties/evolution by continuum elasticity models, Phase-Field methods and Finite Element Method calculations. In particular, I'm interested in developing continuum and coarse-grained approaches to explain and tailor the outcome of experiments.
Additional affiliations
October 2019 - December 2019
City University of Hong Kong
Position
  • Fellow
August 2019 - September 2019
Aalto University
Position
  • Fellow
December 2018 - February 2021
Technische Universität Dresden
Position
  • Research Assistant
Education
January 2013 - January 2016
Università degli Studi di Milano-Bicocca
Field of study
  • Materials Science
October 2010 - June 2012
October 2007 - September 2010

Publications

Publications (81)
Article
Several crystalline structures are metastable or kinetically-frozen out-of-equilibrium states in the phase space. When the corresponding lifetime is sufficiently long, typical equilibrium features such as regular and extended faceting can be observed. However, interpreting the extension of the facets and the overall shape in terms of a standard Wul...
Article
Full-text available
Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulat...
Article
Full-text available
Crystal lattice deformations can be described microscopically by explicitly accounting for the position of atoms or macroscopically by continuum elasticity. In this work, we report on the description of continuous elastic fields derived from an atomistic representation of crystalline structures that also include features typical of the microscopic...
Article
Materials featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, such as light management and topologically protected electronic states. These applications require scalable fabrication, which...
Article
The velocity of dislocations is derived analytically to incorporate and predict the intriguing effects induced by the preferential solute segregation and Cottrell atmospheres in both two-dimensional and three-dimensional binary systems of various crystalline symmetries. The corresponding mesoscopic description of defect dynamics is constructed thro...
Preprint
We present a phase-field crystal (PFC) model for solidification that accounts for thermal transport and a temperature-dependent lattice parameter. Elasticity effects are characterized through the continuous elastic field computed from the microscopic density field. We showcase the model capabilities via selected numerical investigations which focus...
Preprint
An intrinsic feature of nearly all internal interfaces in crystalline systems (homo- and hetero-phase) is the presence of disconnections (topological line defects constrained to the interface that have both step and dislocation character). Disconnections play a major role in determining interface thermodynamics and kinetics. We demonstrate that ela...
Preprint
We derive a phase field crystal model that couples the diffusive evolution of a microscopic structure with the fast dynamics of a macroscopic velocity field, explicitly accounting for the relaxation of elastic excitations. This model captures better than previous formulations the dynamics of complex interfaces and dislocations in single crystals as...
Article
We introduce a dislocation density tensor and derive its kinematic evolution law from a phase field description of crystal deformations in three dimensions. The phase field crystal (PFC) model is used to define the lattice distortion, including topological singularities, and the associated configurational stresses. We derive an exact expression for...
Article
Comprehensive investigations of crystalline systems often require methods bridging atomistic and continuum scales. In this context, coarse-grained mesoscale approaches are of particular interest as they allow the examination of large systems and time scales while retaining some microscopic details. The so-called Phase-Field Crystal (PFC) model conv...
Preprint
We derive the amplitude expansion for a phase-field-crystal (APFC) model that captures the basic physics of magneto-structural interactions. We demonstrate the symmetry breaking due to magnetization and compute the magnetic anisotropy for a BCC crystal. Using efficient numerics and appropriate computing power we consider the shrinkage of a spherica...
Preprint
Comprehensive investigations of crystalline systems often require methods bridging atomistic and continuum scales. In this context, coarse-grained mesoscale approaches are of particular interest as they allow the examination of large systems and time scales while retaining some microscopic details. The so-called Phase-Field Crystal (PFC) model conv...
Article
The motion of interfaces is an essential feature of microstructure evolution in crystalline materials. While atomic-scale descriptions provide mechanistic clarity, continuum descriptions are important for understanding microstructural evolution and upon which microscopic features it depends. We develop a microstructure evolution simulation approach...
Preprint
In many processes for crystalline materials such as precipitation, heteroepitaxy, alloying, and phase transformation, lattice expansion or compression of embedded domains occurs. This can significantly alter the mechanical response of the material. Typically, these phenomena are studied macroscopically, thus neglecting the underlying microscopic st...
Preprint
We present a general method to compute the dislocation density tensor and its evolution from the configuration of a spatially periodic order parameter associated with a given crystal symmetry. The method is applied to a phase field crystal model (PFC) of a bcc lattice, and used to investigate the shrinkage of a dislocation loop. The dislocation vel...
Article
Full-text available
The development of three-dimensional architectures in semiconductor technology is paving the way to new device concepts for various applications, from quantum computing to single photon avalanche detectors. In most cases, such structures are achievable only under far-from-equilibrium growth conditions. Controlling the shape and morphology of the gr...
Article
A long-standing goal of materials science is to understand, predict and control the evolution of microstructures in crystalline materials. Most microstructure evolution is controlled by interface motion; hence, the establishment of rigorous interface equations of motion is a universal goal of materials science. We present a new model for the motion...
Article
Full-text available
We extend the doubly degenerate Cahn–Hilliard (DDCH) models for isotropic surface diffusion, which yield more accurate approximations than classical degenerate Cahn–Hilliard (DCH) models, to the anisotropic case. We consider both weak and strong anisotropies and demonstrate the capabilities of the approach for these cases numerically. The proposed...
Article
Full-text available
We discuss two doubly degenerate Cahn–Hilliard (DDCH) models for isotropic surface diffusion. Degeneracy is introduced in both the mobility function and a restriction function associated to the chemical potential. Our computational results suggest that the restriction functions yield more accurate approximations of surface diffusion. We consider a...
Article
Full-text available
The cover image is based on the Original Article Doubly Degenerate Diffuse Interface Models of Anisotropic Surface Diffusion by Marco Salvalaglio et al., https://doi.org/10.1002/mma.7118.
Preprint
A long-standing goal of materials science is to understand, predict and control the evolution of microstructures in crystalline materials. Most microstructure evolution is controlled by interface motion; hence, the establishment of rigorous interface equations of motion is a universal goal of materials science. We present a new model for the motion...
Preprint
The motion of interfaces is an essential feature of microstructure evolution in crystalline materials. While atomic-scale descriptions provide mechanistic clarity, continuum descriptions are important for understanding microstructural evolution and upon which microscopic features it depends. We develop a microstructure evolution simulation approach...
Preprint
Full-text available
The velocity of dislocation is derived analytically to incorporate and predict the intriguing effects induced by the preferential solute segregation and Cottrell atmospheres in both two-dimensional and three-dimensional binary systems of various crystalline symmetries. The corresponding mesoscopic description of defect dynamics is constructed throu...
Preprint
We extend the doubly degenerate Cahn-Hilliard (DDCH) models for isotropic surface diffusion [arXiv:1909.04458], which yield more accurate approximations than classical degenerate Cahn-Hilliard (DCH) models, to the anisotropic case. We consider both weak and strong anisotropies and demonstrate the capabilities of the approach for these cases numeric...
Article
Full-text available
We present an experimental and theoretical analysis of the formation of nanovoids within Si micro-crystals epitaxially grown on Si patterned substrates. The growth conditions leading to the nucleation of nanovoids have been highlighted and the roles played by the deposition rate, substrate temperature, and substrate pattern geometry, are identified...
Article
Full-text available
We investigate the temperature dependence of the Ge Raman mode strain–phonon coefficient in Ge/Si heteroepitaxial layers. By analyzing the temperature‐dependent evolution of both the Raman Ge─Ge line and of the Ge lattice strain, we obtain a linear dependence of the strain–phonon coefficient as a function of temperature. Our findings provide an eff...
Article
Full-text available
Flexible and stretchable photonics are emerging fields aiming to develop novel applications where the devices need to conform to uneven surfaces or whenever lightness and reduced thickness are major requirements. However, owing to the relatively small refractive index of transparent soft matter including most polymers, these materials are not well...
Article
Full-text available
Large-scale, defect-free, micro- and nano-circuits with controlled inter-connections represent the nexus between electronic and photonic components. However, their fabrication over large scales often requires demanding procedures that are hardly scalable. Here we synthesize arrays of parallel ultra-long (up to 0.75 mm), monocrystalline, silicon-bas...
Preprint
Full-text available
Materials featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, such as light management and topologically protected electronic states. Spontaneous formation of stable patterns could be a via...
Article
Full-text available
The phase-field crystal model in an amplitude equation approximation is shown to provide an accurate description of the deformation field in defected crystalline structures, as well as of dislocation motion. We analyze in detail stress regularization at a dislocation core given by the model, and show how the Burgers vector density can be directly c...
Preprint
The phase-field crystal model in its amplitude equation approximation is shown to provide an accurate description of the deformation field in defected crystalline structures, as well as of dislocation motion. We analyze in detail the elastic distortion and stress regularization at a dislocation core and show how the Burgers vector density can be di...
Article
Capillary-driven mass transport in solids is typically understood in terms of surface-diffusion limited kinetics, leading to conventional solid-state dewetting of thin films. However, another mass transport mechanism, so-called surface-attachment/detachment limited kinetics, is possible. It can shrink a solid film, preserving its original topology...
Preprint
We discuss two doubly degenerate Cahn-Hilliard (DDCH) models for surface diffusion. Degeneracy is introduced in both the mobility function and a restriction function associated to the chemical potential. Our computational results suggest that the restriction functions yield more accurate approximations of surface diffusion. We consider a slight gen...
Preprint
The study of polycrystalline materials requires theoretical and computational techniques enabling multiscale investigations. The amplitude expansion of the phase field crystal model (APFC) allows for describing crystal lattice properties on diffusive timescales by focusing on continuous fields varying on length scales larger than the atomic spacing...
Article
The faceting of a growing crystal is theoretically investigated by a continuum model including the incorporation kinetics of adatoms. This allows us for predictions beyond a simple Wulff analysis which typically refers to faceted morphologies in terms of the equilibrium crystal shape for crystals with an anisotropic surface‐energy, or to steady‐sta...
Article
Nanoscale membranes have emerged as a new class of vertical nanostructures that enable the integration of horizontal networks of III-V nanowires on a chip. To generalize this method to the whole family of III-Vs, progress in the understanding of the membrane formation by selective area epitaxy in oxide slits is needed, in particular for different s...
Preprint
Crystal lattice deformations can be described microscopically by explicitly accounting for the position of atoms or macroscopically by continuum elasticity. In this work, we report on the description of continuous elastic fields derived from an atomistic representation of crystalline structures that also include features typical of the microscopic...
Article
Full-text available
Ge vertical heterostructures grown on deeply-patterned Si(001) were first obtained in 2012 (C.V. Falub et al., Science2012, 335, 1330–1334), immediately capturing attention due to the appealing possibility of growing micron-sized Ge crystals largely free of thermal stress and hosting dislocations only in a small fraction of their volume. Since then...
Article
We address the solid state dewetting of ultra-thin and ultra-large patches of monocrystalline silicon on insulator. We show that the underlying instability of the thin Si film under annealing can be perfectly controlled to form monocrystalline, complex nanoarchitectures extending over several microns. These complex patterns are obtained guiding the...
Article
Full-text available
We address a three-dimensional, coarse-grained description of dislocation networks at grain boundaries between rotated crystals. The so-called amplitude expansion of the phase-field crystal model is exploited with the aid of Finite Element Method calculations. This approach allows for the description of microscopic features, such as dislocations, w...
Article
Full-text available
We present the morphological evolution obtained during the annealing of Ge strips grown on Si ridges as a prototypical process for 3D device architectures and nanophotonic applications. In particular, the morphological transition occurring from Ge/Si nanostrips to nanoislands is illustrated. The combined effect of performing annealing at different...
Article
Full-text available
Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typi...
Article
Abstract In this work we present an innovative approach to realise coherent, highly-mismatched 3-dimensional heterostructures on substrates patterned at the micrometre-scale. The approach is based on the out-of-equilibrium deposition of SiGe alloys graded at an exceptionally shallow grading rate (GR) of 1.5% / µm by low energy plasma enhanced chemi...
Article
Convexity splitting like schemes with improved accuracy are proposed for a phase field model for surface diffusion. The schemes are developed to enable large scale simulations in three spatial dimensions describing experimentally observed solid state dewetting phenomena. We introduce a first and a second order unconditionally energy stable scheme a...
Article
Full-text available
One of the major difficulties in employing phase field crystal (PFC) modeling and the associated amplitude (APFC) formulation is the ability to tune model parameters to match experimental quantities. In this work we address the problem of tuning the defect core and interface energies in the APFC formulation. We show that the addition of a single te...
Article
Full-text available
Shadowing effects during the growth of nano- and microstructures are crucial for the realization of several technological applications. They are given by the shielding of the incoming material flux provided by the growing structures themselves. Their features have been deeply investigated by theoretical approaches, revealing important information t...
Article
We demonstrate that the elastic stress relaxation mechanism in micrometre-sized, highly mismatched heterostructures may be enhanced by employing patterned substrates in the form of necked pillars, resulting in a significant reduction of the dislocation density. Compositionally graded Si1−x Ge x crystals were grown by low energy plasma enhanced chem...
Article
In this work, we demonstrate the growth of Ge crystals and suspended continuous layers on Si(001) substrates deeply patterned in high aspect-ratio pillars. The material deposition was carried out in a commercial reduced-pressure chemical vapor deposition (RPCVD) reactor, thus extending the "vertical-heteroepitaxy" technique developed by using the p...
Article
The structure, interface abruptness and strain relaxation in InAs/GaAs nanowires grown by molecular beam epitaxy in the Ga self-catalysed mode on (111) Si have been investigated by transmission electron microscopy. The nanowires had the zincblende phase. The InAs/GaAs interface was atomically and chemically sharp with a width around 1.5 nm, i. e. s...
Article
Abstract We present a detailed experimental and theoretical analysis of the epitaxial stress relaxation process in micro-structured compositionally graded alloys. We focus on the pivotal SiGe/Si(001) system employing patterned Si substrates at the micrometre-size scale to address the distribution of threading and misfit dislocations within the hete...
Article
Semiconductor heteroepitaxy involves a wealth of qualitatively different, competing phenomena. Examples include three- dimensional island formation, injection of dislocations, mixing between film and substrate atoms. Their relative importance depends on the specific growth conditions, giving rise to a very complex scenario. The need for an optimal...
Article
We present a new concept applicable to the epitaxial growth of dislocation-free semiconductor structures on a mismatched substrate with a thickness far exceeding the conventional critical thickness for plastic strain relaxation. This innovative concept is based on the out-of-equilibrium growth of compositionally graded alloys on deeply patterned su...
Article
Monolithic integration of III-V compounds into high density Si integrated circuits is a key technological challenge for the next generation of optoelectronic devices. In this work, we report on the metal organic vapor phase epitaxy growth of strain-free GaAs crystals on Si substrates patterned down to the micron scale. The differences in thermal ex...
Article
An experiment has demonstrated that truly dislocation free SiGe crystals with widths of at least 5μm can be epitaxially grown on Si substrates by applying the compositional grading developed for layers to 3D structures. At such crystal widths, the epitaxial growth of SiGe alloys with a constant high Ge content inevitably leads to the injection of d...
Article
Dislocation networks are one of the most principle sources deteriorating the performances of devices based on lattice-mismatched heteroepitaxial systems. We demonstrate here a technique enabling fully coherent Ge islands selectively grown on nano-tip patterned Si (001) substrates. The Si-tip patterned substrate, fabricated by complementary metal-ox...