Anomalous reaction of Saucedo-etching on CdZnTeSe crystal

•The CZT and CZTS were grown by Bridgman method to investigate the dislocation.•Anomalous pattern and reaction between Se and Ag in Saucedo-etchant were discovered.•By XPS, EPMA, SEM-EDS, the anomalous phenomena were demonstrated as a Ag2Se.•This study will guide the investigate dislocation in Se-added CdTe-based compounds. CdTe-based materials are vital for charge-collecting devices such as solar cells and radiation detectors. This study investigates anomalous reaction between Se-added CdTe-based crystal and Saucedo-etchant unexpectedly unveiled. CZT and CZTS ingots were grown, and anomalous patterns were explored using EPMA, XPS, and SEM-EDS. The unique pattern from Saucedo-etching on CZTS was attributed to Ag2Se formation. These findings offer guidance into dislocation research in Se-added CdTe-based semiconductors.