This review article summarizes the recent advances in measuring and understanding the indentation-induced plastic deformation and fracture behavior of single crystals of a wide variety of organic molecules and pharmaceutical compounds. The importance of hardness measurement for molecular crystals at the nanoscale, methods and models used so far to analyze and estimate the hardness of the crystals, factors affecting the indentation hardness of organic crystals, correlation of the mechanical properties to their underlying crystal packing, and fracture toughness studies of molecular crystals are reviewed.

Electronic materials such as semiconductors, piezo‐ and ferroelectrics, and metal oxides are primary constituents in sensing, actuation, nanoelectronics, memory, and energy systems. Although significant progress is evident in understanding the mechanical and electrical properties independently using conventional techniques, simultaneous and quantitative electromechanical characterization at the nanoscale using in situ techniques is scarce. It is essential because coupling/linking electrical signal to the nanoscale plasticity provides vital information regarding the real‐time electromechanical behavior of materials, which is crucial for developing miniaturized smarter technologies. With the advent of conductive nanoindentation, researchers have been able to get valuable insights into the nanoscale plasticity (otherwise not possible by conventional means) in a wide variety of bulk and small‐volume materials, quantify the electromechanical properties, understand the dielectric breakdown phenomenon and the nature of electrical contacts in thin films, etc., by continuously monitoring the real‐time electrical signal changes during any point on the indentation load–hold–unload cycle. This comprehensive Review covers probing the electromechanical behavior of materials using in situ conductive nanoindentation, data analysis methods, the validity of the models and limitations, and electronic conduction mechanisms at the nanocontacts, quantification of resistive components, applications, progress, and existing issues, and provides a futuristic outlook.

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Among the 13 polymorphic phases of Si, the ambient temperature stable body-centered cubic (bc8) and rhombohedral (r8) polymorphs have gained significant interest due to their attractive optical and electronic properties suitable for photovoltaic applications. Though ex situ methods were extensively employed previously to understand the pressure-induced phase transformation kinetics of Si, the limited number of available in situ studies has significantly improved the knowledge in this field and clarified uncertainties. Similarly, in this article, we attempt to understand the thermal annealing behavior of nanoindentation-induced r8 and bc8 phases of Si and their volume dependence using in situ high temperature micro-Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM). A spherical diamond indenter of ∼20-μm radius was chosen to indent diamond cubic (dc) Si (100) at different peak loads (Pmax) to create different volumes of high-pressure phases. The Raman spectra, Raman imaging, and XTEM of the pre- and postannealed indents confirm complete annealing of r8/bc8 phases at 200 ± 10 °C, irrespective of the volume of indents. In contrast to the previous ex situ studies, no signature of the presence of the hexagonal diamond (hd)-Si phase was found at elevated temperatures and the overall transformation observed is directly from r8 → polycrystalline dc-Si and bc8 → polycrystalline dc-Si rather than through other metastable phases such as Si-XIII/hd-Si. The present systematic in situ study provides evidence for a few earlier predictions and clarifies ambiguities involved in understanding the annealing behavior and transformation pathways of two high-pressure phases of Si at elevated temperatures.