Automated Crystal Orientation Mapping Research Articles

Atomic force microscopy and transmission electron microscopy identification of deformation twinning in the Cr2AlC MAX phase

Elementary deformation mechanisms have been investigated in a single-crystalline Cr2AlC MAX phase. Plastic deformation has been induced at room temperature by spherical nanoindentation, with a crystal orientation chosen to minimize basal slip and to promote local crystal reorientation. The combination of Atomic Force Microscopy (AFM) surface observation, Transmission Electron Microscopy (TEM) characterization and Automated Crystal Orientation Mapping (ACOM) in a same region has provided a full 3D characterization of the deformation microstructure. Localized and isolated deformation twins have been identified below the indents. The whole microstructure consists in interactions between dislocations and {112¯4} twin variants. The TEM analysis also revealed activation of a 13〈112¯0〉{1¯103} slip system never reported before in a MAX phase.

Investigating Cathode Electrolyte Interphase Formation in NMC 811 Primary Particles through Advanced 4D-STEM ACOM Analysis

Investigating Cathode Electrolyte Interphase Formation in NMC 811 Primary Particles through Advanced 4D-STEM ACOM Analysis

High precision orientation mapping from 4D-STEM precession electron diffraction data through quantitative analysis of diffracted intensities

The association of scanning transmission electron microscopy (STEM) and detection of a diffraction pattern at each probe position (so-called 4D-STEM) represents one of the most promising approaches to analyze structural properties of materials with nanometric resolution and low irradiation levels. This is widely used for texture analysis of materials using automated crystal orientation mapping (ACOM). Herein, we perform orientation mapping in InP nanowires exploiting precession electron diffraction (PED) patterns acquired by an axial CMOS camera. Crystal orientation is determined at each probe position by the quantitative analysis of diffracted intensities minimizing a residue comparing experiments and simulations in analogy to x-ray structural refinement. Our simulations are based on the two-beam dynamical diffraction approximation and yield a high angular precision (∼0.03°), much lower than the traditional ACOM based on pattern matching algorithms (∼1°). We anticipate that simultaneous exploration of both spot positions and high precision crystal misorientation will allow the exploration of the whole potentiality provided by PED-based 4D-STEM for the characterization of deformation fields in nanomaterials.

SAB-Enabled Room Temperature Hybrid Bonding

3D integration is gaining more and more interest for a large panel of applications including CMOS Image Sensor, High Performance Computing, DRAM including HBM stacks and display. Image sensors based on hybrid bonding 3D stacking are the state-of-the-art in imaging applications[1]. Highest integration densities with micron-size pixels are achieved using copper-oxide hybrid bonding in advanced CMOS Image Sensor (CIS) processes. Recently, functional imagers with sub 1 µm pitch of hybrid bonding interconnection have shown great performances in term of reliability [2]. Hybrid bonding low temperature (< 300°C) is increasingly requested by the industry to reduce thermal budget of sensible chips integration such as Image sensors, displays, or memory. Surface Activated Bonding (SAB) is one of the most promising method to enable very low temperature hybrid bonding as very early proposed by Suga et al [3]. Up to know, they have been mainly performed using modified SAB technology [4] or with Oxide recess [5].In this study, 200 mm wafers with 2.5 µm copper pads spaced 2.5 µm apart (5 µm pitch) in a silicon oxide matrix are used. SAB uses argon atom bombardment as surface activation. This bombardment is performed in UHV (ultra- high vacuum) at room temperature during several tens of seconds. Surface copper oxide is removed during the activation, leaving dangling metallic bonds on copper pads surface. Under UHV, two identical wafers are then immediately bonded at RT under a low pressure of 0.3 MPa. Noteworthy, no precise alignment is performed for this hybrid bonding. In order to better understand bonding behavior, a first part of the study focuses on the etching effect due to argon bombardment. AFM (Atomic force microscope) inspections are performed on such activated hybrid surfaces. Then the SAB bondings are characterized by SAM (Scanning Acoustic Microscopy) with or without annealing at 150°C and 200°C during 2 hours. Once the top silicon is removed by grinding, further characterizations such as TEM (Transmission Electron Microscopy) and ACOM (Automated Crystal Orientation Mapping) are carried out. For comparison purposes, standard atmospheric hybrid bonding samples are also fabricated at an annealing temperature between 200°C and 300°C. They are characterized in the same way.SAB for hybrid bonding proves its relevance in this study. Indeed, all bonded samples are successfully grinded and thinned out leaving only the damascene structure (which thickness is around 1 µm) above the bonding interface. Despite oxide/oxide and copper/oxide weak SAB interface, the thinning success for the non-annealed sample demonstrates that enough copper/copper interfaces are successfully obtained. As first suggested by AFM scans after surface activation (Figure 1) and subsequently confirmed by SAM, optimized CMP dishing and etching generated during the SAB activation step allow contacting the copper pads at room temperature. However, improved bonding closure is shown by SAM on the annealed samples. Besides, TEM sections show an excellent copper bonding interface on every SAB samples, even those without annealing. These characterizations have been performed on both SAB hybrid bonding samples and atmospheric ones, allowing comparing both processes and a better understanding of hybrid SAB ones. As could be seen on figure 2, the great copper bonding quality could be summarized by a rebuilt of the copper grains (triple grain boundaries at the interface) and the presence of few defects in the bonding pads. In addition, ACOM provides information about the crystallography of the copper pads all over a section in the bonding. SAB seems to have an effect on the pad crystallography. This will be discuss regarding the process differences.To sum up, bonding of hybrid surfaces at room temperature is successfully realized thanks to SAB. SAM characterizations after bonding, mechanical strength in grinding and TEM images confirm that this process is more than promising in the field of low temperature hybrid bonding. In the wake of these encouraging results, new vehicles including electric test structures are to be bonded with alignment in a SAB system. This new study will allow not only to validate the process on aligned bonded structures but also to qualify the electrical performances of hybrid SAB. Figure 1

Direct ageing of LPBF Al-1Fe-1Zr for high conductivity and mechanical performance

The novel Al-1Fe-1Zr alloy leverages the non-equilibrium solidification conditions characteristic of the laser powder bed fusion (LPBF) process, namely a high thermal gradient (G) and solidification front velocity (R). The multiscale characterization of its microstructure in as-built and peak-aged conditions by SEM, TEM with EDS and automated crystal orientation mapping (ACOM), brings new insights on alloy design for LPBF. The solidification conditions permit the solute supersaturation of Fe and Zr, with the latter precipitating as L12-Al3Zr nanoparticles following ageing, bringing a high strengthening contribution. In conventional Al alloy ingots, Fe tends to create coarse particles which are detrimental to ductility. Here the Fe particles show a fine globular morphology in the as-built condition, and fine faceted Fe-rich intermetallics are obtained upon ageing. Nanoindentation and in situ tensile tests in the SEM coupled with microscale strain measurements shed light on the relation between microstructural and strain heterogeneities in the as-built condition. Our characterization results for this new Al-1Fe-1Zr grade are synthesized into a simple model for its solidification upon LPBF. In particular, the origin of melt pool boundaries is revealed. These are associated with Fe depletion caused by an early planar growth front, and the evolution of these zones upon ageing is presented. With a high potential for industrial applications, the novel alloy with the two elements Zr and Fe exhibiting low solubility at equilibrium and diffusivity in the Al matrix permit to achieve high conductivity (27 MS/m) and yield strength (330MPa) after a simple direct ageing step at 400°C/4h.

Automated Crystal Orientation Mapping in py4DSTEM using Sparse Correlation Matching.

Crystalline materials used in technological applications are often complex assemblies composed of multiple phases and differently oriented grains. Robust identification of the phases and orientation relationships from these samples is crucial, but the information extracted from the diffraction condition probed by an electron beam is often incomplete. We have developed an automated crystal orientation mapping (ACOM) procedure which uses a converged electron probe to collect diffraction patterns from multiple locations across a complex sample. We provide an algorithm to determine the orientation of each diffraction pattern based on a fast sparse correlation method. We demonstrate the speed and accuracy of our method by indexing diffraction patterns generated using both kinematical and dynamical simulations. We have also measured orientation maps from an experimental dataset consisting of a complex polycrystalline twisted helical AuAgPd nanowire. From these maps we identify twin planes between adjacent grains, which may be responsible for the twisted helical structure. All of our methods are made freely available as open source code, including tutorials which can be easily adapted to perform ACOM measurements on diffraction pattern datasets.

Nanoindentation-induced deformation twinning in MAX phase Ti2AlN

Plastic deformation mechanisms have been investigated in the MAX phase Ti2AlN. Nanoindentation has been used to induce plastic deformation in a single grain, and a Transmission Electron Microscopy (TEM) lamella has been extracted in cross section through the indent by using Focused Ion Beam (FIB) technique. By combining TEM observations and automated crystal orientation mapping (ACOM), highly misoriented domains (HMD) have been revealed below a nanoindentation imprint. Thanks to a careful analysis of the relative crystal orientations between these HMD, {112¯2} and {112¯1} deformation twins have been identified for the first time in a MAX phase. Complex structures, involving secondary twinning or different {112¯2} twin variants have also been characterized.

Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy

Compositionally complex alloys (CCAs) in a nanocrystalline state often involve complex and poorly understood phase transformations which can consequently result in grain growth even at low temperatures. A detailed study of the microstructure and phase stability in CCAs is challenging due to the presence of multiple principal components. In view of these challenges the objective of the present study is to establish a systematic understanding of the phase evolution in a face centered cubic non equiatomic nanocrystalline CCA (CoCuFeMnNi). To accomplish this objective, we employed in-situ transmission electron microscope heating in combination with automated crystal orientation mapping (ACOM) and energy filtered transmission electron microscopy (EFTEM) to elucidate the sequence of phase decomposition of the high-pressure torsion (HPT) processed CoCuFeMnNi. Our analysis reveals a complex succession of grain boundary segregation and depletion steps leading to the formation of a FeCo-rich secondary phase. Our results show that prior to the formation of the secondary phase, Cu, Ni and Co segregate and Fe and Mn deplete at the grain boundaries. After the FeCo precipitation is triggered, Mn segregates to the grain boundaries along with Ni and Cu, whereas Fe and Co are depleted. The FeCo precipitates have a B2 crystal structure and typically exhibit a Kurdjumov-Sachs (K-S) and/or Nishyama-Wasserman (N-W) orientation relationships with adjacent fcc grains. Ex-situ heat treated CoCuFeMnNi analyzed by atom probe tomography (APT) revealed a highly heterogeneous segregation of the different elements to different grain boundaries. The FeCo-rich precipitates contain trace amounts of Ni, whereas Cu is rejected leading to the formation of a separate Cu rich phase. This complex segregation phenomenon is assisted by the high fraction of grain boundaries and triple junctions in the nanocrystalline material, which are critical for the phase evolution in this alloy, which is not frequently observed in the corresponding coarse-grained material.

Parent austenite reconstruction tolerant to 180° ambiguity: Application to a very-high-cycle fatigue tested bearing-steel

A novel procedure for parent austenite orientation reconstruction from ferrite maps generated by automatic crystal orientation mapping (ACOM)-transmission electron microscopy (TEM) is proposed and applied to a martensitic bearing-steel subjected to very high cycle fatigue. It enables to counteract the presence of indexing uncertainties in phase and orientation by assuming the appearance of 180°-rotation artefacts.

Multi-scale microstuctural investigation of a new Al-Mn-Ni-Cu-Zr aluminium alloy processed by laser powder bed fusion

Traditional high strength aluminum alloys such as the 2xxx or 7xxx series are prone to cracking when processed by additive manufacturing. Designing new aluminum alloys that can be processed crack-free by Laser Powder Bed Fusion (L-PBF) while exhibiting comparable or enhanced mechanical properties is a major target, which may be reached by including in the alloy design strategy specific features of this processing route such as the very high cooling rates. Here, we study a novel Al-4Mn-3Ni-2Cu-2Zr alloy processed by L-PBF, which shows some specific features in comparison to other Al-alloys developed for additive manufacturing. We establish the relationships between the processing conditions and the specific features of the microstructure inherited from L-PBF based on a multi-scale microstructural characterization approach from the melt pool scale up to the nanoscale using X-ray diffraction and electron microscopy with a special focus on Automated Crystal Orientation Mapping (ACOM) in transmission. At the melt pool scale, three regions have been identified: FEZ (Fine Equiaxed Zone), CZ (Columnar Zone) and CEZ (Coarse Equiaxed Zone) giving a hierarchical architecture to the microstructure. Each region has been thoroughly characterized by coupling ACOM and chemical mapping. Five different intermetallic phases have been identified in the as-built microstructure: Al3Zr, Al3Ni2, Al9Ni2, Al60 Mn 11Ni 14, and Al2Cu. The spatial distribution of these intermetallic phases has been found to vary within a given molten pool. The solidification sequence and the various mechanisms involved in the formation of this peculiar microstructure are discussed in the light of our multi-scale microstructural observations along with solidification thermodynamic calculations.

Exomorphism of jacobsite precipitates in bixbyite single crystals from the Thomas Range in Utah

Abstract Naturally occurring single crystals of bixbyite, (Fe,Mn)2O3, from the Thomas Mountain Range in Utah, U.S.A., were studied via (scanning) transmission electron microscopy (S)TEM. With up to 5 cm edge length, these mineral specimens are the largest bixbyite crystals found worldwide. Their hexahedral shapes are often modified by {211} facets at the corners and small {211} truncations along their cube edges. Characteristic lamellar defects, running parallel to the {100} planes, can be observed via TEM imaging. The defects are, according to EDS analyses, attributed to the tetragonal manganese silicate braunite, Mn7[SiO12]. In the present study, electron nano-diffraction and atomic resolution (S)TEM were employed to verify the presence of braunite lamellae and to investigate their orientation relationship with bixbyite. The analysis confirmed an epitaxial intergrowth of both phases, with their main-axes being parallel and the unique c-axis of braunite always aligned perpendicularly to the lamellar plane. Moreover, small rectangular-shaped precipitates, which had been, due to their almost identical chemical composition, previously interpreted as small bixbyite inclusions within the host crystal, were often observed in contact with the braunite lamellae. Electron nano-diffraction and atomic resolution (S)TEM imaging revealed these crystallites not to be bixbyite but jacobsite, a cubic iron-manganese spinel with the stoichiometric formula MnFe2O4, whose occurrence in this unique context had not been reported before. Moreover, due to the higher temperatures needed for spinel crystallization, the occurrence of jacobsite may serve as a geo-thermometer. (S)TEM in conjunction with automated crystal orientation mapping (ACOM)-TEM showed that no orientation relationship exists between the jacobsite inclusions and the bixbyite/braunite matrix. Nevertheless, their characteristic rectangular shape is typically aligned concordantly with the (001) plane of the braunite lamellae. The resulting crystal shape of jacobsite is determined by the presence of the braunite lamellae, while the respective crystallites maintain their freedom of rotation. To the authors’ knowledge, this is a novel observation of exomorphosis of jacobsite, i.e., the change in the habit of the spinel crystallites due to external conditions. Note that the term “exomorphosis” is used here in the mineralogical sense in contrast to the often-used petrological aspect. Based on the TEM results, the formation of the jacobsite precipitates is discussed and a growth model suggested.

The influence of solute on irradiation damage evolution in nanocrystalline thin-films

Grain boundaries (GBs) are considered sinks where mobile defects are attracted and annihilated thereby hampering irradiation damage accumulation. Nanocrystalline (NC) metals characteristically have greater densities of GBs relative to their coarse-grained counterparts hence they are postulated to provide enhanced resistance to irradiation damage.The use of alloying as a means to impart synergistic properties such as corrosion resistance, increased toughness, or improved conductivity is well studied, yet the cooperative effects of solute addition and grain size in the nano-regime is not well understood. In this study, a combination of in situ ion irradiation, transmission electron microscopy (TEM), and automated crystal orientation mapping (ACOM) on model Ni, NiCr, Fe, and FeCr NC thin-films are used to provide experimental evidence that grain size and irradiation induced defect morphology (defect density and size) are not directly correlated due to defect agglomeration, annihilation at sinks, and saturation, while the addition of solute impedes defect mobility, altering the final damage state.

On the role of impurities on spheroidal graphite degeneracy in cast irons

Though manufacturing spheroidal graphite cast irons is a well-established industrial process, good nodularity which is essential for mechanical properties may be hampered by several factors. Amongst them is the presence of impurities at trace level which lead to the growth of protrusions and the question is how they can destroy the spheroidizing effect of magnesium. For the first time, it is shown that such impurities are present together with magnesium at the interface between spheroid and protrusion. For getting this result, site-specific electron transparent lamellae were prepared using Focused Ion Beam and characterized at nanometric scale using atomic resolution scanning-transmission electron microscope. It is also shown by automatic crystal orientation mapping that there is no definite crystallographic relationship between protrusions and underlying spheroids.

Wear resistance of graphenic-nickel composite coating on austenitic stainless steel

In order to improve the tribological behavior of austenitic stainless steel, a novel composite coating based on reduced graphene oxide-Ni (rGO-Ni) is presented. These coatings were prepared by sol–gel using a mixture of Ni-rich xerogel films and reduced graphene oxide (rGO), with a heat treatment at 1000 °C for 1 h under an Ar flow. Raman spectroscopy confirmed that the rGO-Ni coating was formed. The rGO-Ni coating demonstrated an unusual surface topography, combined with multiple lamellar carbon growth and refined grains characterized by automatic crystal orientation mapping as determined through electron backscattered diffraction (EBSD). The rGO-Ni-composite coating exhibited a high elastic behavior from a multi-step nanoindentation with a depth of 900 nm and wear loss of ~ 0.05 to 0.3 mm3 at 1 to 5 N. It was found that the increase on wear resistance was due to both the self-lubrication properties of the rGO and the harness of refined grains on the coating.

In situ indentation and high cycle tapping deformation responses in a nanolaminate crystalline/amorphous metal composite

The incorporation of nanostructured and amorphous metals into modern applications is reliant on the understanding of deformation and failure modes in constrained conditions. To study this, a 105 nm crystalline Cu/160 nm amorphous Cu45Zr55 (at.%) multilayer structure was fabricated with the two crystalline layers sputter deposited between the top-middle-bottom amorphous layers and prepared to electron transparency. The multilayer was then in situ indented either under a single load to a depth of ~ 100 nm (max load of ~ 100 μN) or held at 20 μN and then repeatedly indented with an additional 5 μN up to 20,000 cycles in a transmission electron microscope to compare the deformation responses in the nanolaminate. For the single indentation test, the multilayer showed serrated load-displacement behavior upon initial indentation inductive of shear banding. At an indentation depth of ~ 32 nm, the multilayer exhibited perfect plastic behavior and no strain hardening. Both indented and fatigue-indented films revealed diffraction contrast changes with deformation. Subsequent Automated Crystal Orientation Mapping (ACOM) measurements confirmed and quantified global texture changes in the crystalline layers with specifically identified grains revealing rotation. Using a finite element model, the in-plane displacement vectors under the indent mapped conditions where ACOM determined grain rotation was observed, indicating the stress flow induced grain rotation. The single indented Cu layers also exhibited evidence of deformation induced grain growth, which was not evident in the fatigue-indented Cu based multilayer. Finally, the single indented multilayer retained a significant plastic crater in the upper most amorphous layer that directly contacted the indenter; a negligible crater impression in the same region was observed in the fatigued tested multilayer. These differences are explained by the different loading methods, applied load, and deformation mechanisms experienced in the multilayers.

Comparing Scanning Electron Microscope and Transmission Electron Microscope Grain Mapping Techniques Applied to Well-Defined and Highly Irregular Nanoparticles.

Investigating how grain structure affects the functional properties of nanoparticles requires a robust method for nanoscale grain mapping. In this study, we directly compare the grain mapping ability of transmission Kikuchi diffraction (TKD) in a scanning electron microscope to automated crystal orientation mapping (ACOM) in a transmission electron microscope across multiple nanoparticle materials. Analysis of well-defined Au, ZnO, and ZnSe nanoparticles showed that the grain orientations and GB geometries obtained by TKD are accurate and match those obtained by ACOM. For more complex polycrystalline Cu nanostructures, TKD provided an interpretable grain map whereas ACOM, with or without precession electron diffraction, yielded speckled, uninterpretable maps with orientation errors. Acquisition times for TKD were generally shorter than those for ACOM. Our results validate the use of TKD for characterizing grain orientation and grain boundary distributions in nanoparticles, providing a framework for the broader exploration of how microstructure influences nanoparticle properties.

Forming‐Free Grain Boundary Engineered Hafnium Oxide Resistive Random Access Memory Devices

AbstractA model device based on an epitaxial stack combination of titanium nitride (111) and monoclinic hafnia (11) is grown onto a c‐cut Al2O3‐substrate to target the role of grain boundaries in resistive switching. The texture transfer results in 120° in‐plane rotated m‐HfO2 grains, and thus, in a defined subset of allowed grain boundary orientations of high symmetry. These engineered grain boundaries thread the whole dielectric layer, thereby providing predefined breakdown paths for electroforming‐free resistive random access memory devices. Combining X‐ray diffraction and scanning transmission electron microscopy (STEM)–based localized automated crystal orientation mapping (ACOM), a nanoscale picture of crystal growth and grain boundary orientation is obtained. High‐resolution STEM reveals low‐energy grain boundaries with facing () and (21) surfaces. The uniform distribution of forming voltages below 2 V—within the operation regime—and the stable switching voltages indicates reduced intra‐ and device‐to‐device variation in grain boundary engineered hafnium‐oxide‐based random access memory devices.

Nanostructural characterization of sputter deposited Ti-Nb coatings byautomated crystallographic orientation mapping

AISI 316 L stainless steel (SS) and CrCo alloys are commonly used for manufacturing biomedical implants due to their reasonably adequate bulk properties. Commercially pure (CP) Ti and its alloys are more biocompatible, but also significantly more expensive, than SS and CoCr alloys; they have an additional advantage compared to SS and CoCr alloys: their elastic modulus values are more compatible with those of the human bones (10–40 GPa). An interesting option would be to coat an implant with a TiNb thin film having adequate composition and thickness so that the coating would enhance the material biocompatibility. In this work, TiNb coatings were deposited on AISI 316L stainless steel and silicon substrates by magnetron sputtering and then were characterized by scanning and transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) coupled with automatic crystal orientation mapping (ACOM). The results show that films form a homogenous solid solution and that the growth modes are not modified by the Nb content and substrate material. Also, the texture changes together with the grain growth morphology with the increase in the niobium content. For a columnar structure characteristic of zone II of the zone structure diagram (SZD) there are strongly marked textures in {113} for the x-axis, {110} for the y-axis, and {111} for the z axis. These are suppressed when the growth type changes for the T zone with the variation in the alloying element content, and that could be due to the high mobility generated during the deposition process.

Comprehensive analysis of TEM methods for LiFePO4/FePO4 phase mapping: spectroscopic techniques (EFTEM, STEM-EELS) and STEM diffraction techniques (ACOM-TEM)

Transmission electron microscopy (TEM) has been used intensively in investigating battery materials, e.g. to obtain phase maps of partially (dis)charged (lithium) iron phosphate (LFP/FP), which is one of the most promising cathode material for next generation lithium ion (Li-ion) batteries. Due to the weak interaction between Li atoms and fast electrons, mapping of the Li distribution is not straightforward. In this work, we revisited the issue of TEM measurements of Li distribution maps for LFP/FP. Different TEM techniques, including spectroscopic techniques (energy filtered (EF)TEM in the energy range from low-loss to core-loss) and a STEM diffraction technique (automated crystal orientation mapping (ACOM)), were applied to map the lithiation of the same location in the same sample. This enabled a direct comparison of the results. The maps obtained by all methods showed excellent agreement with each other. Because of the strong difference in the imaging mechanisms, it proves the reliability of both the spectroscopic and STEM diffraction phase mapping. A comprehensive comparison of all methods is given in terms of information content, dose level, acquisition time and signal quality. The latter three are crucial for the design of in-situ experiments with beam sensitive Li-ion battery materials. Furthermore, we demonstrated the power of STEM diffraction (ACOM-STEM) providing additional crystallographic information, which can be analyzed to gain a deeper understanding of the LFP/FP interface properties such as statistical information on phase boundary orientation and misorientation between domains.

In situ observation of deformation processes in nanocrystalline face-centered cubic metals.

The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline PdxAu1−x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin–twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains.