Behavioral change in Optical and Electrical property of Cd Chalcogenidefilms containing Te, Se deposited by Thermal and Electron beam evaporation

摘要

Cadmium Chalcogenide material has emerged as a promising semiconductor because of its potential applications in the field of electronics and technology. Ternary films of Cd Te Se were coated on glass substrate by thermal and electron beam evaporation. Optical characterization such as Transmittance (T%) and Reflectance (R%) data’s were collected. Samples were subjected to thermal analysis like DSC, DTA and TGA to find the composition and the stability. Some of the samples deposited by electron beam evaporation were annealed at temperatures 200° C and 400° C. For the annealed films (Cd0.6Te0.2Se0.2 & Cd0.7Te0.2Se0.1) % of R and % of T has changed to comparable R&T and finally to T%. These values reveal the antireflection behavior of the coating. Refractive index ‘n’ of the films deposited by thermal evaporation is very high. This can be explained due to thickness variation or due to density of state. The absorption spectra of the annealed sample gave very broad band absorption characteristics (absence of absorption peak) having potential to yield a broad band antireflection. Optical energy band gap has varied from1.3 eV to 2.65 eV for the various compositions of CdTeSe. The electrical resistivities of few ternary films have been carried out using four probe techniques. It is surprising that samples answer for both +TCR and –TCR, (Temperature co efficient of Resistance) and change occurring at and around 368°K which happens to be the inversion/Transition temperature. Whereas, the other sample answering for both +TCR and –TCR, change occurs at 378°K. Materials with appropriate composition selected for the present study have exhibited both ohmic and semiconducting nature as well as both R%, comparable R% & T%, finally T%. Above points justify the major role played by Se and Te content in the investigated films. The present study signifies the behavioral changes in optical and electrical properties exhibited by Cd Chalcogenide films. Further studies to know the exact inversion/transition temperature is under investigation.