Unveiling the brittleness of hybrid organic-inorganic 0-D histammonium zinc chlorometallate by nanoindentation

Hybrid organic-inorganic halometallates, with different organic and inorganic components, can provide a wide array of tunable physical properties. While many optoelectronic phenomena are being explored, research on the mechanical properties of this class of materials, especially fracture toughness, is lacking, resulting in conclusions on material flexibility being drawn from their elastic modulus and hardness alone with an implicit assumption that these properties correlate with material flexibility. In this Letter, we report nanoindentation results on the elastic modulus, hardness, and fracture toughness of single crystal samples of hybrid organic-inorganic histammonium chlorozincate, HistZnCl4 along the [001] axis. We find that the elastic modulus is 12.078 ± 1.034 GPa, and the hardness is 0.611 ± 0.089 GPa. Moreover, the fracture toughness of this sample is measured to be 0.098 MPa m 1 2. Although these materials have a hardness to modulus ratio similar to that of metals, they fracture like brittle materials, demonstrating the importance of conducting studies on a material fracture toughness before determining their applicability in flexible device applications.