Ramakanta Naik; C. Sripan; R. Ganesan
Abstract
In this manuscript, the As40Se60 and As50Se50 samples of 800nm thickness were deposited onto glass substrate by thermal evaporation technique. The as-deposited films were characterized using X-ray diffraction (XRD) and FTIR Spectrophotometer. The prepared samples are amorphous type. The transmission ...
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In this manuscript, the As40Se60 and As50Se50 samples of 800nm thickness were deposited onto glass substrate by thermal evaporation technique. The as-deposited films were characterized using X-ray diffraction (XRD) and FTIR Spectrophotometer. The prepared samples are amorphous type. The transmission is found to be decreased for As50Se50 film. The indirect optical transition mechanism for the photon absorption happens inside the studied film. The optical band gap is decreased with change in As and Se content. The density of state model and increase in disorder is responsible for the reduction of optical band gap in the studied films. The addition of more % As creates localised states in the gap which results the tailing of the band edges. The Urbach energy which gives the degree of disorder changes that indicates the more disorderness of As50Se50 than As40Se60 film. The XPS As3d, Se3d core level spectra variation infers the optical changes in the film and such type of film can be used for optical materials and optoelectronics.
Mukta Behera; Rozalin Panda; Naresh C. Mishra; Ramakanta Naik
Abstract
In the present work, structural, microstructural, compositional and electronic band gap properties of As40Se60 and As40Bi15Se45 bulk and thin films are reported. The films were prepared by thermal evaporation technique under high vacuum. X-ray diffraction (XRD) study indicated amorphous nature of As40Se60 ...
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In the present work, structural, microstructural, compositional and electronic band gap properties of As40Se60 and As40Bi15Se45 bulk and thin films are reported. The films were prepared by thermal evaporation technique under high vacuum. X-ray diffraction (XRD) study indicated amorphous nature of As40Se60 in bulk prepared by melt quenching technique. Bi incorporation in As40Se60 with composition Bi15As40Se45 however led to nucleation of Bi2Se3 nanocrystallites in the amorphous matrix of As40Se60. The films made out of the two targets of composition As40Se60 and As40Bi15Se45 did not show any XRD peak, indicating their amorphous nature. UV-Visible-NIR spectroscopic study indicated a large decrease in the electronic band gap from 1.74 eV in films of composition As40Se60 to 1.28 eV for compositon Bi15As40Se45. This decrease is explained on the basis of a high concentration of defect states leading to the presence of localized states in the band gap due to Bi incorporation. Field emission scanning electron microscopy (FESEM) images show smooth and homogeneous surface for the As40Se60 films, while Bi incorporation led to increases of the surface roughness in the Bi15As40Se45 films. The decreased band gap and increased surface roughness on Bi incorporation in As40Se60 films indicate the suitability of these films for solar cell applications.