In₂Se₃ Nanocubes as High Current Density Cold Cathode Materials

In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocubes synthesized by laser ablation in aqueous medium. The morphological characterization carried out using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) reveal that the nanocubes have an average size of 70 nm. X-ray diffraction and Raman analysis clearly imply formation of pure and crystalline In2Se3 phases only, without any impurity phases, despite laser ablation being carried out in aqueous medium. In addition, the field emission and charge carrier behavior of In2Se3 nanocubes have been investigated. The laser-ablated sample shows a cubical morphology having a 70 nm average particle size. The ultrafast transient absorption spectroscopy (UTAS) suggests the slow decay behavior of charge carriers and an increase in the trap state levels after laser ablation, in contrast to the untreated bulk sample. Surprisingly, the In2Se3 nanocubes on a carbon tape emitter exhibits superior FE properties characterized by lower values of turn-on and threshold fields as compared to In2Se3 nanowire emitters and the ability to deliver very large current density ∼2656 μA/cm2 by applying a field of 9.7 V/μm. Furthermore, the In2Se3 nanocube emitter showed very good emission stability at the pre-set value 10 μA over a duration of 5 h. The superior FE characteristics of the In2Se3 nanocube emitter is attributed to unique morphology characterized by nanometric cubes and improved electrical properties, as revealed by UTAS analysis. The observed results imply the potential of In2Se3 nanocube emitters for practical applications in vacuum nano-microelectronic devices.