Luminescence Properties of Yb- and Nd- Implanted CdS
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Luminescence Properties of Yb- and Nd- Implanted CdS A. K. Alshawa, H. J. Lozykowski, T. Li, Ohio University, Department of Electrical and Computer Engineering, Athens, OH. ; and I. Brown, University of California, Berkeley, Lawrence Berkeley Laboratory, Berkeley, CA ABSTRACT The photoluminescence (PL) and time resolved spectra of Nd- and Yb-implanted CdS samples are studied under pulsed and CW excitations using Ar+ ion laser for different excitation intensities and temperature (9 - 300 K). The samples were annealed under different conditions using the thermal-pulse method. For CdS:Nd, the PL spectra was recorded in the range 890930 nm (transitions 4F3 2d-4I1 /) and for CdS:Yb it was recorded in the range 985 - 1010 nm (transitions 2F5 / -2 2F7n). The Rise time and decay time were studied for both CdS:Nd and CdS:Yb at different emission lines as a function of temperature and excitation power. INTRODUCTION The photoluminescence properties of rare earth (RE) ions in II-VI semiconductor compounds have been of interest for many years. The light emission due to radiative transitions in the partially occupied 4f' shell of REV3 ions in the form of lines and narrow bands is the basis for numerous applications such as solid state lasers. Beside the application aspect, the rare earth impurities are of great interest from scientific point of view. Scientific interest is related to the uniqueness of optical and electrical properties of rare earth impurities in semiconductor hosts. It is well known that the rare earth luminescence depends very little on the nature of the host and the temperature. The 4f orbits of rare earth ions incorporated in semiconductors are so deeply buried within the electronic shell that the energy levels of the 4Pfconfiguration are only slightly perturbed compared to free ion energy levels. The electronic structure of the rare earth luminescence centers and their electrical activities, as well as their indirect photoluminescence excitation mechanisms are still not well understood. The luminescence of rare earth doped cadmium sulphide has been reported by many V3 in CdS. researchers[1-4]. The attempt was to explain the mechanisms of exciting the RE In [1], Kingsley and et al, proposed that the energy is transferred from luminescence centers ( in his case, copper) to the rare earth ions. Anderson [2] proposed that the transfer of energy is due to the electronic transition between donor-acceptor levels. In this paper, we report the luminescence properties of Nd3+ and Yb3 + implanted in CdS. Time resolved spectra was recorded for Nd3+ and Yb 3+ in the ranges 890-930 nm (transitions 4F3&--4Ig91 ) and 9851010 nm (transitions 2Fsa/-- 2F7/2), respectively. The term assignments for these transitions are obtained from [5]. The PL spectra was investigated at different temperatures in the range 8.5 - 300 K. Rise time and decay time processes were also studied as a function of temperature and excitation intensity. SAMPLES AND MEASUREMENT The implantation of Yb and Nd was performed with an unconventional technique u
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