Pt and Li complexes in silicon. 99-07-22 16.52

Abstract

Two different Pt- and Li-related centers in silicon have been studied by excitation spectroscopy combined with uniaxial stress and isotope doping experiments. The dominating spectrum consists of a series of sharp lines between about 5000 and 8000cm−1 and is due to excitation from a deep initial state to various shallow donor states. The energy positions of the electronic lines in Li6-doped samples shift by about 1cm−1 to lower energies compared to those in Li7 samples. Phonon replicas of the no-phonon lines are detected with ℏω(Li7)=528.6cm−1 and ℏω(Li6)=547.8cm−1. Other replicas of the no-phonon lines are also observed involving an energy of about Δ=2229cm−1 as well as combinations of Δ and hω. The uniaxial stress data indicate that the center has either tetrahedral or orthorhombic I symmetry. The second center gives rise to sharp lines at 1965.64, 1974.12, and 2001.00cm−1 at T<30K. The 2001cm−1 line has a full width at half maximum of 1.4 and 0.12cm−1 at room temperature and T=10K, respectively. Uniaxial stress experiments show that all three lines originate from excitations of a trigonal center. The isotope shift is small and for Li6 samples the 2001cm−1 line shifts only by 0.06cm−1 to higher energy compared to Li7 samples.