2018 年 67 巻 9 号 p. 840-843
We fabricated field-effect transistors (FETs) using ammonium sulfide-treated PbS colloidal nano-dot (CND) films. After the ligand molecules were removed from the CNDs by the ammonium sulfide treatment, many cracks were observed in the atomic force microscope image of the PbS ND monolayer that was formed by horizontal lifting method. Those cracks were filled and almost disappeared after we repeated the formation of the PbS CND monolayer and removal of the ligand molecules for three times. The FETs fabricated with the cracked PbS ND films exhibited serious bias stress effect and very low hole mobility of 5.6×10-5 cm2V-1s-1, which were attributed to the carrier traps existing on the NDs surface. On the other hand, the carrier mobility of the FETs with the crack-free PbS ND films was improved to be 1.1×10-3 cm2V-1s-1 because the cracks were filled and the trap density was significantly reduced.