Study On Optical Properties Of Mn Doped CdS Nanobelts And Optoelectronic Properties Of CdSSe Nanobelts

Among ?-? of one-dimensional?1D?nanometer semiconductor materials,cadmium sulfide has been widely used in the field of photoelectric detection,light emitting diodes,and solar cells due to its good chemical and physical properties.Cadmium sulfide is a direct gap semiconductor with 2.42 eV at room temperature,its photoelectronic performance is related to its size and structure.Therefore,it is very importance to study the controlled synthesis of nanomaterials to adjust the properties of materials.Pure CdS,Mn-CdS and CdSSe nanobelts were prepared by thermal evaporation at 820? with a carrier gas of argon?18 sccm?.The morphology,structure and composition of the nanobelts were characterized by scanning electron microscope?SEM?,transmission electron microscopy?TEM?,high-resolution transmission electron microscope?HRTEM?,X-ray diffraction?XRD?,energy dispersive X-ray spectrometer?EDS?,and X-ray photoelectron spectroscopy?XPS?.In addition,the optical properties of the nanobelts were studied by UV-visible?UV-vis?,Raman spectroscopy?Raman?,photoluminescence?PL?and cathodoluminescence?CL?.Finally,the photodetective properties of the fabricated devices are studied.The main results are as follows:On the optical properties: it is found that the prepared nanobelts have uniform size,smooth surface and very thin.The band gaps of pure CdS,Mn-CdS and CdSSe nanobelts were 2.32 eV,2.25 eV and 1.97 eV,respectively.Compared with that of pure CdS nanobelts,the band gap of Mn doped CdS nanobelts was reduced by 0.07 eV,and its PL occurred red shift.The Raman spectra of pure CdS nanobelts with the first order?1LO?and the second order?2LO?longitudinal optical vibrational modes are located at 318 cm^-1 and 618 cm^-1,respectively.Compared with that of pure CdS nanobelts,the Raman spectra of Mn doped CdS nanobelts show a slight red shift.Photoluminescence showed that the characteristic peak of pure CdS is 510 nm;Mn doped CdS nanobelts have two emission peaks,which are located at 510 nm and 642 nm,respectively.The emission peak of 642 nm may be caused by the vacancy of Sor surface defects.CL spectrum revealed that the pure of CdS nanobelts and Mn doped CdS nanobelts have stronger intensity at low temperature than at room temperature.Compared with that of pure CdS,Mn doped CdS nanobelts exhibits blue shift on the vicinity of around 500 nm and 700 nm.The photoluminescence spectra of the CdSSe nanobelts show that the emission band is located between those of the CdS and CdSe;the CL spectra at low temperature is stronger than that at room temperature.On the photodetective properties: under the illuminstion of white light and at the bias voltage of 1V,the photocurrent of a single CdSSe nanobelts device is1.60×10^-7A,the dark current is 1.96?10-10 A,and the ratio of light current to dark one is 816.It is found that the CdSSe nanobelts have good photoelectric properties.The spectral responsivity of the device is 3.77 AW^-1,the external quantum efficiency?EQE?is about 6.94%,and the photoconductivity?Gph?is about 8.0×10^-2 S/cm.In addition,the photocurrent increases with the increase of the optical power density.the relationship between the photocurrent and the optical power density is ruled by I_P=AP^0.69.Therefore,CdSSe nanobelts have good stability and repeatability in the field of photoelectronic detectors.