Nano sulfide and oxide semiconductors as promising materials for studies by positron annihilation

16th International Conference on Positron Annihilation

Nambissan, P.M.G.^1

Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India^1

关键词: Coincidence doppler broadening;    Experimental techniques;    Line shape parameters;    Positron annihilation parameters;    Quantum confinement effects;    Structural transitions;    TiO2 nano-particles;    Vacancy-type defects;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012040/pdf
DOI  :  10.1088/1742-6596/443/1/012040

来源: IOP

【 摘 要 】

A number of wide band gap sulfide and oxide semiconducting nanomaterial systems were investigated using the experimental techniques of positron lifetime and coincidence Doppler broadening measurements. The results indicated several features of the nanomaterial systems, which were found strongly related to the presence of vacancy-type defects and their clusters. Quantum confinement effects were displayed in these studies as remarkable changes in the positron lifetimes and the lineshape parameters around the same grain sizes below which characteristic blue shifts were observed in the optical absorption spectra. Considerable enhancement in the band gap and significant rise of the positron lifetimes were found occurring when the particle sizes were reduced to very low sizes. The results of doping or substitutions by other cations in semiconductor nanosystems were also interesting. Variously heat-treated TiO2nanoparticles were studied recently and change of positron annihilation parameters across the anatase to rutile structural transition are carefully analyzed. Preliminary results of positron annihilation studies on Eu-doped CeO nanoparticles are also presented.