Effect of ZnS and PbS shell on mem-behavior of CdS quantum dots

In this paper, a systematic study is carried out on mem-behavior of CdS, CdS@ZnS, and CdS@PbS core-shell nanocomposites with emphasis on the effect of ZnS and PbS shell on mem-behavior of CdS quantum dots. From X-ray diffraction, the CdS quantum dots are found to be hexagonal in nature with average crystallite size similar to 10.3 nm. From high-resolution transmission electron microscope images, the particle size is calculated around 3-4 nm for CdS quantum dots. For core-shell nanoparticles, formation of epitaxial shell layer on CdS core is clearly evident with enhancement in particle sizes. Active layer of as-synthesized samples is deposited on Indium tin oxide-coated glass which is used as one electrode. Aluminium is used as counter electrode and deposited over the active layer using thermal evaporation technique. The fabricated devices show bipolar switching characteristics with prominent hysteresis loops. The current-voltage characteristics of the devices show memristive, memcapacitive, and meminductive behavior depending on the type of active layer used. It is also observed that the inclusion of ZnS and PbS shell significantly alters the mem-behavior of the CdS quantum dots which is the major finding of this study. The conduction through the device is found to be due to coulomb blockade which also supports the ON/OFF switching mechanism. The sensitivity of the devices can be determined from RON/ROFF ratio, and it is found to be higher for CdS@ZnS core-shell nanoparticles compared to CdS quantum dots and CdS@PbS nanoparticles.