Synthesis, Electrical And Optoelectrical Properties Of Cadmium Selenium And Cadmium Sulfide Nanobelts

Cadmium selenide (CdSe) and cadmium sulfide (CdS) are importantII-VI semiconductor compounds with direct-bandgap, and theirone-dimensional nanostructures are important building blocks forelectronic, optoelectronic devices etc.. However, the fabrication of Ohmiccontacts between intrinsic CdSe and metal electrodes are difficult to beachieved, which limits their application in high performance nanodevices.Doping is an efficient method for improving the electrical transport andoptoelectrical properties. In this paper, the electrical and optoelectricalproperties of the CdSe nanobelts were improved via Bi or Cl doping.Besides, the synthesis of one-dimensional CdS micro-nanostructures wasalso investigated.The Bi-doped CdSe nanobelts were synthesized via a thermalevaporation process. The XRD, SEM, TEM, EDS, Raman were employedto characterize the morphology, structure and composition of nanobelt.The valence states of elements wer analysized by XPS technique. Theresults indicate that the as-synthesized CdSe nanobelts havesingle-crystalline wurtzite structure. The single nanobelt field effecttransistors (FETs) was fabricated and investigated, indicating thatBi-doped nanobelts are n-type semiconductor. The conductivity of theBi-doped nanobelts is~105times more than that of the intrinsic nanobelts.Cl-doped CdSe nanobelts were also synthesized using the thermalevaporation method. The single Cl-doped nanobelt FETs andphotodetectors were fabricated and investigated. The results indicate thatthe Cl-doped CdSe nanobelts show n-type behavior and enhancedconductivity (~106times more than that of the intrinsic nanobelts). Thephotodetectors exhibit high spectral response rate (8.87×105AW-1) andexternal quantum efficiency (1.14×106). In addition, the electron transport properties of Cl-doped CdSe nanobelts in vacuum or air have beenstudied, indicating that the Cl-doped nanobelts show higher conductivityin vacuum than that in the air.One-dimensional CdS micro-nanostructures were synthesized via thethermal evaporation method with Au and Ag2S as catalysts orcatalyst-free growth mode. The morphology and structure of the materialswere characterized by SEM and XRD. The results show that micron andsub-micron structures can be obtained under catalyst-free growth. BothAu and Ag2S are active catalysts for growth of one-dimensional CdSnanostructures. TEM-EDS characterizations confirm thatone-dimensional CdS nanostructure can be catalysted by Ag2S.