The field of metallurgy has greatly benefited from the development of electron microscopy over the last two decades. Scanning electron microscopy (SEM) has become a powerful tool for the investigation of nano-and microstructures. This article reviews the complete set of tools for crystallographic analysis in the SEM, i.e., electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD), and electron channeling contrast imaging (ECCI). We describe recent relevant developments in electron microscopy, and discuss the state-of-the-art of the techniques and their use for analyses in metallurgy. EBSD orientation measurements provide better angular resolution than spot diffraction in TEM but slightly lower than Kikuchi diffraction in TEM, however, its statistical significance is superior to TEM techniques. Although spatial resolution is slightly lower than in TEM/ STEM techniques, EBSD is often a preferred tool for quantitative phase characterization in bulk metals. Moreover, EBSD enables the measurement of lattice strain/rotation at the sub-micron scale, and dislocation density. TKD enables the transmitted electron diffraction analysis of thin-foil specimens. The small interaction volume between the sample and the electron beam enhances considerably the spatial resolution as compared to EBSD, allowing the characterization of ultra-finegrained metals in the SEM. ECCI is a useful technique to image near-surface lattice defects without the necessity to expose two free surfaces as in TEM. Its relevant contributions to metallography include deformation characterization of metals, including defect visualization, and dislocation density measurements. EBSD and ECCI are mature techniques, still undergoing a continuous expansion in research and industry. Upcoming technical developments in electron sources and optics, as well as detector instrumentation and software, will likely push the border of performance in terms of spatial resolution and acquisition speed. The potential of TKD, combined with EDS, to provide crystallographic, chemical, and morphologic characterizations of nano-structured metals will surely be a valuable asset in metallurgy.

This article presents a characterization of the damage caused by energetic beams of electrosprayed nanodroplets striking the surfaces of single-crystal semiconductors including Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN. The sputtering yield (number of atoms ejected per projectile's molecule), sputtering rate, and surface roughness are measured as functions of the beam acceleration potential. The maximum values of the sputtering yields range between 1.9 and 2.2 for the technological important but difficult to etch SiC and GaN respectively, and 4.5 for Ge. The maximum sputtering rates for the non-optimized beam flux conditions used in our experiments vary between 409 nm/min for SiC and 2381 nm/min for GaSb. The maximum sputtering rate for GaN is 630 nm/min. Surface roughness increases modestly with acceleration voltage, staying within 2 nm and 20 nm for all beamlet acceleration potentials and materials except Si. At intermediate acceleration potentials, the surface of Si is formed by craters orders of magnitude larger than the projectiles, yielding surface roughness in excess of 60 nm. The effect of projectile dose is studied in the case of Si. This parameter is correlated with the formation of the large craters typical of Si, which suggests that the accumulation of damage following consecutive impacts plays an important role in the interaction between beamlet and target.

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The hypervelocity impact of electrosprayed nanodroplets on single-crystal silicon amorphizes a thin layer of the target. Molecular Dynamics simulations have shown that the amorphization results from the melting of the material surrounding the impact interface, followed by an ultrafast quenching that prevents recrystallization. This article extends this previous work to study the role of the projectile's diameter and velocity on the amorphization phenomena and compares the simulation results with experimental measurements of a bombarded silicon target. In the range of projectile diameter and impact velocity studied (diameter between 5 and 30 nm, and velocity between 1 and 6 km/s), the projectile velocity plays a more relevant role than its diameter. A significant amorphous layer begins to develop at a velocity near 3 km/s, its thickness rapidly increasing with velocity until it plateaus at about 4 km/s. The reduction of the melting temperature with pressure combined with the conversion of kinetic energy into thermal energy are responsible for the melting of silicon starting at an impact velocity of 3 km/s. Once the conditions inducing amorphization are reached, the volume of the generated amorphous phase scales linearly with both the kinetic energy and the volume of the projectile.