Interfacial Misfit Dislocations Research Articles

Characterization of the interfacial structure and fracture behavior of in situ synthesized ceramics to reinforce Ni-based composite coatings

This work used the in-situ synthesis of molten-state nitride ceramic phase-reinforced Ni-based alloy coatings, aiming to improve the phase-interface bonding through the interdependent co-solidification between molten droplets. The XRD was used to analyze the physical phases of the composite coatings. The microstructure and phase-interface structure were characterized in detail by combining SEM, TEM, HRTEM, FFT, and SAED techniques. Microhardness tester and microforce microhardness tester were employed to measure the surface hardness and elastic modulus of the composite coatings. The fracture behavior of the composite coatings was characterized by observing the fracture morphology of the coatings using SEM combined with the EDS technique. It was found that the formation mechanisms of interfacial misfit dislocation assistance, lattice distortion, aggregation of stacking faults, and specific growth orientation between the γ-Ni matrix phase and each ceramic phase in NiCrBSi-TiCrN composite coatings improved the lattice matching between the two-phase interface, which resulted in the formation of atomically corresponding coherent lattice relations and stepped interfacial semi-coherent lattice relations, and enhanced the degree of phase-interface bonding. On this basis, the composite coatings with high Cr content further inhibited the expansion of interphase penetration cracks due to the existence of Cr-rich zones at the phase interface, thus exhibiting high fracture toughness. This work provides new opinions on the improvement of phase-interface bonding and composition design of Ni-based composite coatings.

Epitaxial growth of high-quality GaAs on Si(001) using ultrathin buffer layers

The direct growth of III–V semiconductors on silicon holds tremendous potential for photonics applications. However, the inherent differences in their properties lead to defects in the epitaxial layer, including threading dislocations (TDs), antiphase boundaries (APBs), and thermal cracks, significantly impacting device performance. Current processes struggle to suppress these defects simultaneously, necessitating the development of methods to inhibit TDs and APBs in a thin buffer on silicon. This study introduces a GaSb buffer layer during GaAs epitaxy on a silicon (001) substrate. This approach successfully suppresses defect formation by promoting the formation of interfacial misfit dislocation arrays at both the AlSb/Si and GaAs/GaSb interfaces. The resulting GaAs layer exhibits a step-flow surface with a rough mean square of ∼3.8 nm and a full width at half maximum of 158 arcsec. Remarkably, the growth is achieved without any observable interfacial intermixing. Building on this platform, InAs/GaAs quantum dots are grown with a density of 3.8 × 1010 cm−2, emitting at a wavelength of 1288 nm. This breakthrough holds immense promise for developing high-quality GaAs films with reduced defect densities on silicon for O band lasers, laying the foundation for the mass production of silicon-based integrated circuits.

Growth mechanisms of eta phase in 718Plus alloy

Growth mechanisms of eta phase in 718Plus alloy were investigated by high-resolution scanning transmission electron microscopy. The results demonstrated the nucleation and growth of the η platelets were arranged along the {111}γ habit planes. The fine lamellae γ phase, enveloped in the η platelets blocks, was determined. The possible occurrence of interfacial misfit dislocations could effectively release the mismatch strain, and enhance the ledges nucleation on the {0001}η plane. Analysis of the experimental observations, and possible mechanisms of growth were also addressed.

Free-surface proximity induced bistability and semi-semicoherency in precipitation systems

In systems without a ‘high misfit’ and in the early stage of growth, the precipitates tend to remain coherent with the parent matrix. On further growth beyond a critical size (r*), the precipitates undergo a coherent to semi-coherent transition by formation of interfacial misfit dislocation loops to minimize the total strain energy of the system. The variation of r* with domain size has been studied and the concept of re-entrant interface transition to the coherent state was demonstrated in finite crystals. Dislocations can exist in a state of mechanical equilibrium; but are thermodynamically metastable. In the proximity of ‘interfaces’ dislocations experience a configurational force. The current work pertains to study the stability of an interfacial misfit dislocation loop in the proximity of a free-surface; wherein we evaluate configurational effects in a semi-infinite body. The Cu-2 wt%γFe alloy is used as a model system in this study. In this work we: (i) demonstrate the stabilization of the coherent state (divergence of r*), induced by the proximity of the free-surface; (ii) discover the existence of bistability in materials at the microstructural scale, resulting from the destabilization of the equatorial position of the dislocation loop and arising from symmetry breaking in climb of the interfacial loop due to the vicinity of a free-surface. (iii) identify regimes of ‘equi-bistablity’ and regions with asymmetry in energy wells, (iv) establish the existence of a ‘semi’-semicoherent state. Here, one specific system has been chosen to illustrate the effects; however, we expect the conclusions to have a broader applicability.

Development of “GaSb-on-silicon” metamorphic substrates for optoelectronic device growth

The epitaxial development and characterization of metamorphic “GaSb-on-silicon” buffers as substrates for antimonide devices is presented. The approach involves the growth of a spontaneously and fully relaxed GaSb metamorphic buffer in a primary epitaxial reactor, and use of the resulting “GaSb-on-silicon” wafer to grow subsequent layers in a secondary epitaxial reactor. The buffer growth involves four steps—silicon substrate preparation for oxide removal, nucleation of AlSb on silicon, growth of the GaSb buffer, and finally capping of the buffer to prevent oxidation. This approach on miscut silicon substrates leads to a buffer with negligible antiphase domain density. The growth of this buffer is based on inducing interfacial misfit dislocations between an AlSb nucleation layer and the underlying silicon substrate, which results in a fully relaxed GaSb buffer. A 1 μm thick GaSb layer buffer grown on silicon has ∼9.2 × 107dislocations/cm2. The complete lack of strain in the epitaxial structure allows subsequent growths to be accurately lattice matched, thus making the approach ideal for use as a substrate. We characterize the GaSb-on-silicon wafer using high-resolution x-ray diffraction and transmission electron microscopy. The concept’s feasibility is demonstrated by growing interband cascade light emitting devices on the GaSb-on-silicon wafer. The performance of the resulting LEDs on silicon approaches that of counterparts grown lattice matched on GaSb.

Plastic deformation of Ag/MgO interface system during tensile fracture: A molecular dynamics study

Fracture experiments on layered metal-ceramic composites show that the plastic dissipation in the metal near the crack tip accounts for most of the macroscopic fracture toughness. In this work we studied the microscopic plastic deformation mechanisms of Ag/MgO interface systems using molecular dynamics (MD) method. As tensile strain increases, lattice dislocations nucleate at interface misfit dislocations and propagate in metal layer. The formation of immobile Hirth dislocations in Ag causes hardening. As the metal layer increases, the yield strength decreases and the hardening range is shortened. Large interface area increases the degree of inhomogeneity of dislocation motion and interface fracture behavior, leading to decreased interface yield strength.

Low Dark Current Operation in InAs/GaAs(111)A Infrared Photodetectors: Role of Misfit Dislocations at the Interface.

We demonstrate an extended short-wave infrared (e-SWIR) photodetector composed of an InAs/GaAs(111)A heterostructure with interface misfit dislocations. The layer structure of the photodetector consists simply of an n-InAs optical absorption layer directly grown with a thin undoped-GaAs spacer layer on n-GaAs by molecular beam epitaxy. The lattice mismatch was abruptly relaxed by forming a misfit dislocation network at the initial stage of the InAs growth. We found high-density threading dislocations (1.5 × 109 cm-2) in the InAs layer. The current-voltage characteristics of the photodetector at 77 K had a very low dark current density (<1 × 10-9 A cm-2) at a positive applied voltage (electrons flow from n-GaAs to n-InAs) of up to ∼+1 V. Simulation of the band structure revealed that the direct connection of GaAs and InAs and the formation of interfacial states by the misfit dislocations play significant positive roles in suppressing dark current. Under illumination with e-SWIR light at 77 K, a clear photocurrent signal was observed with a 2.6 μm cutoff wavelength, which is consistent with the bandgap of InAs. We also demonstrated e-SWIR detection at room temperature with a 3.2 μm cutoff wavelength. The maximum detectivity at 294 K exceeds 2 × 108 cm Hz0.5 W-1 for the detection of e-SWIR light at 2 μm.

The effect of loading axes on deformation behavior of Cu/Al multilayer

The effect of loading axes on deformation behavior of Cu/Al multilayer is studied via molecular dynamics. The yield strength under x-axis or y-axis loading parallel to interface is lower than that under z-axis loading perpendicular to interface, while tensile strength is opposite. Partial dislocations preferentially nucleate at nodes of interfacial misfit dislocations under parallel loading, but explosively nucleate below interface under perpendicular loading. Deformation mechanisms under loading along x, y, and z axes are partial dislocation and deformation twinning, extended full dislocation, as well as partial dislocation, respectively. Strip-like voids form at interface under parallel loading and sphere-like voids form below interface under perpendicular loading, respectively.

Viewing SiGe Heterostructure for Qubits with Dislocation Theory

SiGe/Si/SiGe heterostructure serves as one of the ideal semiconductor material system to build large scale electron spin qubits[1]. To further push the scalability and extend the coherence times of qubits built on SiGe/Si/SiGe heterostructures, there are several factors to improve, one of that is the lattice homogeneity of strained Si. One source of lattice homogeneity break down are dislocations. Due to the difficulties of high quality SiGe bulk crystal growth [2-3], relaxed SiGe is commonly grown on Si substrates by epitaxy. Viewing the SiGe/Si/SiGe heterostructure on native Si substrate, dislocations half loops form unavoidably because of the misfit between SiGe and the Si substrate. These dislocation half loops consist of threading segments extending through the whole heterostructure (figure 1 (a) and (c)) [4]. Due to the stress caused by the strained Si quantum well layer, the threading dislocations can be driven to glide, resulting in additional misfit segments in the lower interface of strained Si layer when the critical thickness is exceeded (figure 1 (b)) [5]. The extension of these misfit segments is blocked when they meet other perpendicular dislocations (figure 1 (d)) [6]. These misfit dislocations destroy strain uniformity and cause tilt inside the Si layer, resulting in a distortion of the valley splitting and ultimately, reducing the coherence time of qubits [7-8].In this work, we present the observation of dislocations in SiGe/Si/SiGe heterostructures for qubit application by plan-view TEM (Figure 1 (right)). Here, the experimental observations agree with dislocation theory that threading dislocations (some are marked by (b)) will glide and elongate to have misfit segments (some are marked by (c)) in the interface when two requirements are fulfilled: misfit exists between epitaxial layer and substrate; critical thickness is exceeded. When the misfit dislocations meet perpendicular misfit dislocation line, they are blocked since the thickness is not enough to glide over it [6]. This is the case in figure 1 right marked by (d). Due to the misfit segment generation and blocking effects, the misfit dislocation spacing is proportional to the threading dislocation density both theoretically and experimentally. These misfit dislocations bring local strain field around them [9], which disturb the desired homogeneous strain field by misfit. Therefore, misfit dislocation generation needs to be suppressed if one wants to achieve homogeneous strain in Si thin layer in large scale.According to Matthews-Blakeslee theory, one can avoid the formation of misfit dislocations in the Si interface by controlling the strained layer within the critical thickness. The critical thickness of Si on Si0.7Ge0.3 is calculated as 8.5 nm. The Electron channeling contrast images of Si with difference thickness 10 nm and 5 nm grown on high threading dislocation relaxed Si0.7Ge0.3 buffer at 700°C by reduced pressure chemical vapor deposition in Figure 2 are collaborating with theory: obviously misfit dislocation appear in 10 nm Si on relaxed Si0.7Ge0.3 (Figure 2 (left)) and no misfit dislocation are presented in 5 nm Si on Si0.7Ge0.3 (Figure 2 (right)).Our results show that dislocation generation and movement needs to be taken into consideration to further develop SiGe heterostructure based qubits.

Mid-infrared InAs/InAsSb Type-II superlattices grown on silicon by MOCVD

In this work we report the growth of the InAs/InAsSb type-II superlattice (T2SL) onto Si substrates via the use of a GaSb/GaAs/Si buffer layer structure all grown by MOCVD. Transmission electron microscopy (TEM) was used to show the effectiveness of the buffer layer structure in reducing threading dislocation density and to verify the formation of an interfacial misfit dislocation array between the GaSb and GaAs layers. Electron channelling contrast imaging was used to measure a threading dislocation density of 6.73 × 108/cm2 at the surface of the T2SL. TEM and X-ray diffraction show that the T2SL itself was grown to a high quality considering the large mismatch of the heteroepitaxy. Fourier transform infrared spectroscopy was used to measure the photoluminescence performance of the T2SL which was found to have a FWHM of 50 meV at a peak wavelength of 4.5 µm at 77 K. These results are a step forward towards integration of full InAs/InAsSb T2SL device structures onto Si substrates via MOCVD.

Effects of interdiffusion on shear response of semi-coherent {111} interfaces in Ni/Cu

Intermixing of chemical species as a result of interdiffusion during the manufacturing of metallic nanolaminates leads to diffuse interface structures which have distinct properties compared to corresponding atomically sharp interfaces. The effect of interdiffusion-induced changes to the interface structure on interface shear strength is complex due to the presence of solute atoms and a reduced misfit dislocation density. The shear responses of {111} Cu/Ni nanolaminate interfaces with varying levels of interdiffusion are studied using atomistic methods to elucidate the effect of interface structure changes on shear deformation mechanisms. Models with diffuse interfaces exhibit improved interface shear strength relative to the atomically sharp case; however, shear strength does not increase monotonically with solute concentration. The distribution of maximum changes in energy per misfit node and non-uniform misfit node displacements, filtered using microrotation vector analysis, suggest heterogeneous interface resistance to sliding. No strong correlation is found between solute concentration near misfit node centroids and misfit node displacements, indicating the importance of the longer-range misfit dislocation structure. Increased activation of misfit dislocation glide is associated with larger solute concentrations as a result of increased misfit node displacements. Analysis of change in energy during the shear deformation process, however, reveals that interface sliding is dominated by the misfit node behavior. These findings highlight the importance of modeling realistic diffuse interface structures and emphasize the competing effects of solute concentration and interface misfit dislocation density.

Mechanical properties and [formula omitted] interfacial misfit network evolution: A study towards the creep behavior of Ni-based single crystal superalloys

The aim of this study is to investigate the role of the temperature, stress, and rhenium (Re) on the γ/γ' interfacial misfit dislocation network and mechanical response of Ni-based single crystal superalloys. After aging at elevated temperatures, mismatch between the two phases results in an interfacial dislocation network to relieve the coherency stress. Molecular dynamics (MD) simulations have been performed to study the properties of the (100), (110), and (111) phase interface crystallographic directions. Increasing temperature disperses the atomic potential energy at the interface diminishing the strength and stability of the networks. In the case of loading, when a constant strain rate of 2×108(s−1) is applied at 0 K, the (100) and (111) phase interface models lose their co-coordinating role of maintaining the dynamic equilibrium. Dislocation propagation in the γ phase is the dominant deformation mechanism in these two interfacial models, resulting in dislocations pile-up in the damaged area, and the network is no longer able to fortify the interface. For the (110) phase interface model, the dominant deformational mechanism is precipitate shearing. As temperature increases, the elastic modulus, initial mismatch stress, and yield strength decrease. Also, the pinning effect of Re atoms is evaluated in the γ phase at 1600 K. The dislocation hampering property of Re is more perceptible when enough dislocations in the γ phase are moving at elevated temperatures. In addition, Re manages to relieve the interfacial stress field and does not affect the network morphology. Finally, an investigation of the creep behavior of the superalloy is provided. It is observed that the escalated damage to the interfacial network due to the increased temperature leads to the domination of the softening mechanisms (cross-slip and dislocation climb) on the deformation and shortens the steady-state creep. Moreover, Re atoms act as an extra hardening factor to improve the tertiary creep.

Macroscale stress induced stabilization of coherent precipitates

In systems with 'moderate' misfit, on nucleation and in the initial stages of the growth, precipitate crystals may be coherent with the matrix. This reduces the interfacial chemical energy; but a higher cost is paid in terms of the energy stored in the long range strain fields. On the growth beyond a critical size (r*), the energy of the system is minimized via the formation of interfacial misfit dislocation loops. It has been shown that the coherent state is stable in two separate size regimes of the precipitate in finite bodies (i.e. shows a re-entrant interface character transition) and further the coherent state can be fully stabilized below a critical size of the domain (R*). The presence of stress fields in the material, either due to internal sources or due to externally applied loads, is expected to alter the magnitude of the r*. In the current work, finite element simulations are used to study the effect of elastic stress fields on r*. The Cu-2wt.%γFe alloy is used as a model system towards this end. A map is generated demarcating the regions of stability of the coherent and semi-coherent states; with normalized r*, domain size (R) and elastic stress (σyy) as axes. We conclude the following. (i) Stresses of the order of GPa leads to a change in r*. (ii) The re-entrant interface character transition to the coherent state is suppressed by tensile stress. (iii) The coherent state is stabilized due to compressive stress. (iv) Compressive stress expands the phase field of the coherent state, while tensile stress has the opposite effect. (v) In 'very small' domains the coherent state can be stabilized in spite of being subjected to tensile stress.

Strain relaxation and spinodal decomposition in composition adjusted TiO2-VO2 films on TiO2(100) substrates

In this study, we investigate the process of strain relaxation and spinodal decomposition in TiO2-VO2 films on TiO2(100) substrates. Herein, the film composition was adjusted to Ti0.2V0.8O2 for the relaxation of the in-plane tensile c-axis strain in the films. A 115 nm thick Ti0.2V0.8O2 solid-solution film is epitaxially grown on a rutile-type TiO2(100) substrate using a pulsed laser deposition technique, and is annealed inside the spinodal region. Reciprocal space mapping measurements show that the in-plane tensile c-axis strain is almost fully relaxed in the solid-solution film. Scanning transmission electron microscopy (STEM) observation results reveal that the annealed film causes spinodal decomposition along the c-axis direction, forming vertically aligned multilayer structures. The STEM observations also suggest the presence of interfacial misfit dislocations along the c-axis, indicating the generation of plastic strain relaxation along the c-axis in the film. Composition analysis reveals that the Ti-V interdiffusion between the film and substrate is considerably suppressed. The overall results of this study show that the composition adjustment to Ti0.2V0.8O2 is effective for strain relaxation along the in-plane c-axis and occurrence of spinodal decomposition with reduced Ti-V interdiffusion in the TiO2-VO2 films on TiO2(100). Our study helps establish a method for the formation of nanostructures via spinodal decomposition in the TiO2-VO2 films.

Atomistic modeling of interface strengthening in Al-Si eutectic alloys

Al-Si cast alloys are usually composed of α-Al and Al-Si eutectic. Si flakes and Al matrix generally hold cube-on-cube orientation relationship with the primary interface (111)Al∥(111)Si. Extensive experimental studies demonstrated that Si flakes cannot significantly improve mechanical properties of Al-Si cast alloys. We hypothesize that the weak strengthening effect associated with Si flakes might be attributed to thermomechanical properties of Al-Si interfaces besides their morphologies. To characterize Al-Si interfaces with a large lattice mismatch (> 30%), we proposed the quasi-coincident site lattice (Q-CSL) as reference lattice, and demonstrated that the Q-CSL Al-Si coherent interface has three characteristic coherent structures, one stable and low energy structure and two metastable and high energy structures. The translation vectors for the same type of coherent Q-CSL structures are consistent with three displacement shift complete (DSC) vectors. The two metastable structures can be obtained by shifting the low energy structure with three partial DSC vectors. Semi-coherent interface is composed of the low energy Q-CSL patches and three sets of interface misfit dislocations with Burgers vectors same as the DSC vectors. Atomistic simulations revealed that Al-Si interface exhibits low shear resistance. Ideal shear strength of the Q-CSL coherent interface is 110 MPa and semi-coherent interface is 20 MPa. The low shear resistance is attributed to the glide of interface misfit dislocations. Al-Si interface also exhibits low formation and migration energies of point defects. Owing to low shear strength and low formation and migration energies of point defects, interface sliding or shear readily happen under mechanical loading or during dislocation-interface interactions. Lattice dislocations can cross slip onto or climb along Al-Si interfaces. These reactions decrease the number of accumulated dislocation loops around Si flakes and promote nucleation and emission of lattice dislocations from Al-Si interfaces to matrix, consequently reduce the repulsive force on approaching dislocations and weaken Si flakes strengthening effect. In situ tension and compression tests in a scanning electron microscope reveal relatively weak strengthening effect due to Si flakes, consistent with the computed dislocation interaction with interfaces and shear behavior of interfaces.

Interaction between the edge dislocation dipole pair and interfacial misfit dislocation network in Ni-based single crystal superalloys

Understanding the intrinsic strengthening mechanism is of great significance for microstructural design of Ni-based single crystal superalloys. In this paper, from an atomistic perspective, the interacting mechanism between edge dislocation dipole pair and interfacial misfit dislocation network has been elaborated. It is shown that a network of interfacial misfit dislocations can effectively impede the movement of matrix dislocations, accommodate and pile up the edge dislocation dipole pairs in Ni matrix. Furthermore, we have systematically elucidated the influence of loading rates on the stimulating period of edge dislocation dipole pairs and stiffness of Ni/Ni3Al substrate. These findings provide a better understanding of the interfacial strengthening mechanism of Ni-based single crystal superalloys.

Interface structures and dislocation nucleation of Cu/graphene interface via molecular dynamic simulations

Molecular dynamic simulations have been performed to investigate the effects of Cu {111}/graphene interface structures on the initial dislocation nucleation behavior in Cu/graphene layered composites. The characteristics of interfacial structures, including four possible types of stacking structures, interfacial misfit dislocations and interfacial energy distribution, have been studied based on geometrical analysis Thompson tetrahedron, disregistry analysis, and excess potential energy. In addition, interfacial structures are transformed by rotating the graphene layer with various angles, which further changing the morphology of the interface. After relaxation, the equilibrium state of the interface consists of a hexagon unit region arranging in periodicity, which also depicts the periodic energy distribution both on the Cu and graphene side. Under uniaxial X and Y directions loading, the evolution of interface patterns provides a non-Schmid factor for initial interfacial dislocation nucleation which prefers to locate the sites of higher potential energy area. Moreover, the rotation of the graphene layer changes the interfacial structures by changing the atoms mismatch on the Cu/graphene interface, which consequently influences the nucleation conditions including sites, morphology and slip system as well. This work provides an understanding of the Cu/graphene interface-dominated dislocation nucleation.

Numerical investigation on threading dislocation bending with InAs/GaAs quantum dots* *Project supported by the National Natural Science Foundation of China (Grant Nos. 61874148, 61974141, and 61674020), the Beijing Natural Science Foundation, China (Grant No. 4192043), the National Key Research and Development Program of China (Grant No. 2018YFB2200104), the Fund from the Beijing Municipal Science & Technology Commission, China (Grant No.

The threading dislocations (TDs) in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon. The insertion of InAs quantum dots (QDs) acting as dislocation filters is a pretty good alternative to solving this problem. In this paper, a finite element method (FEM) is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations (MDs). Making a comparison of elastic strain energy between the two isolated systems, a reasonable result is obtained. The effect of the cap layer thickness and the base width of QDs on TD bending are studied, and the results show that the bending area ratio of single QD (the bending area divided by the area of the QD base) is evidently affected by the two factors. Moreover, we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs. For the QD with 24-nm base width and 5-nm cap layer thickness, taking the QD density of 1011 cm−2 into account, the bending area ratio of single-layer QDs (the area of bending TD divided by the area of QD layer) is about 38.71%. With inserting five-layer InAs QDs, the TD density decreases by 91.35%. The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.

Interface Structures and Dislocation Nucleation of Cu/graphene Incoherent Interface Via Molecular Dynamic Simulations

Molecular dynamic simulations have been performed to investigate the effects of Cu {111}/graphene interface structures on the initial dislocation nucleation behavior in Cu/graphene layered composites. The characteristics of interfacial structures, including four possible types of stacking structures, interfacial misfit dislocations and interfacial energy distribution, have been studied based on geometrical analysis Thompson tetrahedron, disregistry analysis and excess potential energy. In addition, interfacial structures are transformed by rotating the graphene layer with various angles, which further changing the morphology of the interface. After relaxation, the equilibrium state of the interface consists of a hexagon unit region arranging in periodicity, which also depicts the periodic energy distribution both on the Cu and graphene side. Under uniaxial X and Y directions loading, the evolution of interface patterns provides a non-Schmid factor for initial interfacial dislocation nucleation which prefer to locate the sites of higher potential energy area. Moreover, the rotation of graphene layer changes the interfacial structures by changing the atoms mismatch on the Cu/graphene interface, which consequently influences the nucleation conditions including sites, morphology and slip system as well. This work provides an understanding on the Cu/graphene interface-dominated dislocation nucleation.

Lattice dislocation induced misfit dislocation evolution in semi-coherent {111} bimetal interfaces

The study of dislocation plasticity mediated by semi-coherent interfaces can aid in the design of certain heterostructured materials, such as nanolaminates. The evolution of interface misfit patterns under complex stress fields arising from dislocation pileups can influence local dislocation/interface interactions, including effects of multiple incoming dislocations. This work utilizes the Concurrent Atomistic-Continuum modeling framework to probe the evolution of misfit structures at semi-coherent Ni/Cu and Cu/Ag interfaces impinged by dislocation pileups generated via nanoindentation. A continuum microrotation metric is computed at various stages of the indentation process and used to visualize the evolution of the interface misfit dislocation pattern. The stress state from approaching dislocations induces mixed contraction and expansion of misfit dislocation structures at the interface. A lower number of misfit nodes per unit interface area coincides with greater localized deformation with regard to atoms near misfit nodes for Ni/Cu. The decreased misfit node spacing for Cu/Ag alternatively distributes the restructuring associated with plastic deformation over a larger percentage of atoms at the interface. Interface sliding facilitated by misfit dislocation motion is found to facilitate deformation extending into the bulk lattices centered on misfit nodes. The depth of penetration of those fields is found to be greater for Ni/Cu than for Cu/Ag. The study of dislocation plasticity mediated by semi-coherent interfaces can aid in the design of certain heterostructured materials, such as nanolaminates. The evolution of interface misfit patterns under complex stress fields arising from dislocation pileups can influence local dislocation/interface interactions, including effects of multiple incoming dislocations. This work utilizes the Concurrent Atomistic-Continuum modeling framework to probe the evolution of misfit structures at semi-coherent Ni/Cu and Cu/Ag interfaces impinged by dislocation pileups generated via nanoindentation. A continuum microrotation metric is computed at various stages of the indentation process and used to visualize the evolution of the interface misfit dislocation pattern. The stress state from approaching dislocations induces mixed contraction and expansion of misfit dislocation structures at the interface. A lower number of misfit nodes per unit interface area coincides with greater localized deformation with regard to atoms near misfit nodes for Ni/Cu. The decreased misfit node spacing for Cu/Ag alternatively distributes the restructuring associated with plastic deformation over a larger percentage of atoms at the interface. Interface sliding facilitated by misfit dislocation motion is found to facilitate deformation extending into the bulk lattices centered on misfit nodes. The depth of penetration of those fields is found to be greater for Ni/Cu than for Cu/Ag.