Defect characterization of Er implanted, Ge-rich SiO2 layers using slow positron implantation spectroscopy

Electroluminescence in SiO2 layers can be created by Ge implantation and a subsequent heat treatment, which forms Ge nano-particles inside the SiO2. An additional implantation of Er, connected with a further annealing, led to an improvement of the luminescence properties. However, with exceeding an optimum concentration of the Er doping the intensity of the electro-luminescence was found to be drastically decreased.
Slow positron spectroscopy (single Doppler broadening (DB) and coincidence DB) was applied in order to probe ongoing processes at a microscopic level and, in particular an impact on the optical response depending on the concentration of rare earth Er. It could be shown that the increasing intensity of the electro-luminescence is connected with a crystalline structure of the SiO2 covering the nano-particles and the improved reverse energy transfer process between Er and Ge. Obtained positron annihilation results will be compared with Transmission Electron Microscopy investigations [1] and with conclusions in recently published papers [2, 3].

[1] A. Kanjilal, L. Rebohle, M. Voelskow, W. Skorupa, M. Helm
J. Appl. Phys. 106, 026104 (2009)
[2] C.L. Heng, E. Chelomentsev, Z.L. Peng, P. Mascher, P.J. Simpson
J Appl. Phys. 105, 014312 (2009)
[3] R.S. Yu, M. Maekawa, A. Kawasuso, T. Sekiguchi, B.Y. Wang, X.B. Qin, Q.Z. Wang
NIMB 267, 3097 (2009)