Acoustic shock wave driven dynamic recrystallization induced reversible rod-to-cube morphology transition in CdS: preserving structural integrity with optical modifications

Cadmium sulfide (CdS) is a promising semiconductor with a narrower bandgap, making it highly suitable for optoelectronic and energy storage applications. However, its response to extreme conditions, such as acoustic shock waves, remains unexplored. In this study, CdS samples were subjected to varying shock pulses such as 100, 200, 300, and 400 at a transient pressure of 0.59 MPa and a temperature of 520 K, with a Mach number of 1.5, to investigate structural, optical, and morphological modifications. Analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy, UV-Vis Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) spectroscopy, and Field-Emission Scanning Electron Microscopy (FE-SEM), were employed for comprehensive analysis. XRD and Raman results confirm that the structure remains stable up to 400 shock pulses, with only a minor peak shift observed at 300 shock pulses and, at 400 shock pulses which subsequently reverts to its original position. Optical studies reveal a reversible bandgap shift from 2.37 eV to 2.24 eV, while the PL emission peak shifts from 518 nm to 528 nm and reverts to its original position at 400 shock pulses. Most interestingly, FE-SEM analysis reveals a morphological transition, and the rod morphology evolves into a cube morphology at 300 shock pulses due to shock wave-induced dynamic recrystallization. Remarkably, at 400 shock pulses, the morphology reverts to its original rod morphology, highlighting the reversibility of morphology. These results highlight the critical role of dynamic recrystallization in enabling morphology modulation without structural phase alteration. This study establishes acoustic shock waves as a promising pathway to tune both optical properties and morphology of materials while preserving their structural integrity, offering new directions for functional material design and processing.