Synthesis And The Optical And Optoelectronic Properties Of ZnSe Nanomaterials

ZnSe nanoribbons grown for35minutes and50minutes were synthesized by anAu-catalyzed chemical vapor deposition method. And the samples grown for35minutes were annealed at700℃in a Zn-rich atmosphere for20minutes,50minutesand75minutes, respectively. The morphology and microstructure of the as-synthesiz-ed products were characterized by field emission scanning electron microscopy,high-resolution transmission electron microscopy and XRD, respectively. At the sametime, the composition, the optical properties and the optoelectronic properties of ZnSenanoribbons were also characterized. The conclusions are drawn as follows:(1) High resolution transmission electron microscopy (HRTEM) measurement sindicate that there are structure defects existing at the edges of the nanoribbons grownfor35minutes, such as stacking faults, twinning defects and grain boundaries. Themicro photoluminescence (-PL) spectra and PL mappings show the near bandemission is very weak due to the existence of structure defects and a broad DDemission band appears. The broad DD emission band can be fitted into threesub-bands with Gauss profiles, centered at635nm,560nm and535nm, respectively.PL mappings clearly identify the relationship between the microstructure and theoptical properties. There are more defects at the edges than that at the central region.The power dependent PL spectra of the ZnSe nanoribbons further identify theexistence of the three emission bands and the nature of each level. The temperaturedependent PL spectra at a certain excitation power demonstrate that the carrierstransfer among the different defect states. All of the diffraction peaks can be indexedto zinc-blende-structured ZnSe according to the XRD characterization.(2) High resolution transmission electron microscopy (HRTEM) measurement sshow that the defects exist in the nanoribbons grown for50minutes. At the same time,the existence of the defects is also proved by the surface photovoltage test and theKelvin test, which is well corresponding with the characterization results. The surfacephotovoltage test, CPD and surface work function characterized by Kelvin probesuggest that ZnSe compound semiconductor is n-type semiconductor. It can be foundthat the photogenerated electrons move in the direction of backlight by analyzing thephase diagram. (3) The products after annealing treatment for75minutes have hardly anydefects by the TEM characterization and the composition analysis. It provides theevidence that the annealing treatment in a Zn-rich atmosphere can reduce the defects.At the same time it proves that the defects are mainly induced by lack of zinc. Thelonger the annealing time is, the fewer and fewer defects there are. All of thediffraction peaks can be indexed to zinc-blende-structured ZnSe according to theXRD characterization.