Sequential Cation Exchange Generated Superlattice Nanowires Forming Multiple p–n Heterojunctions

Fabrication of superlattice nanowires (NWs) with precisely controlled segments normally requires sequential introduction of reagents to the growing wires at elevated temperatures and low pressure. Here we demonstrate the fabrication of superlattice NWs possessing multiple p–n heterojunctions by converting the initially formed CdS to Cu2S NWs first and then to segmented Cu2S–Ag2S NWs through sequential cation exchange at low temperatures. In the formation of Cu2S NWs, twin boundaries generated along the NWs act as the preferred sites to initiate the nucleation and growth of Ag2S segments. Varying the immersion time of Cu2S NWs in a AgNO3 solution controls the Ag2S segment length. Adjacent Cu2S and Ag2S segments in a NW were found to display the typical electrical behavior of a p–n junction.