Electronic Structure of Transition Metal Complexes in Silicon

Abstract: This thesis consists of experimental studies of the electronic of electronic structure of the transition metals Au and Pt, and the transition metal complexes, FeIn, PtLi, and AuLi in silicon. Fourier transform infrared spectroscopy, photoconductivity, uniaxial stress- and Zeeman spectroscopy are employed. The excitation spectrum of the FeIn pair in silicon is observed for the first time. Two sets of lines where observed and identified as the excitation spectra of the trigonal and orthohombic FeIn pair center. The orthorhombic configuration is stable but population of the metastable trigonal configuration was obtained by above-bandgap excitation. The Zeeman results of the orthorhombic FeIn center shows that the electronic structure of the ground and excited states is similar. This together with the fact that the excitation lines do not split under uniaxial stress, strongly suggest that the excitation lines are due to internal "d" transitions at the interstitial Fe ion. The resonance-like doublet structure observed for the Au and Pt Acceptor lines in silicon, previously attributed to the 2p' Coulombic line, is shown to be the 1S3/2(G8) phonon-assisted Fano resonance involving the zone-center G optical phonon. Stress-induced preferential alignment effects are revealed for both centers. The doublet structure is shown to be due to crystal field splitting of the 1S3/2(G8) Coulombic state. The electronic and vibrational structure of a gold and Lithium related center in silicon have been investigated. The excitation spectrum shows close similatity to the priviously studied gold-pair center in that it consists of zero-phonon lines followed by several relatively sharp phonon replicas. Transitions to three different series were observed and in all cases a phonon energy of about 59 cm-1 and 47 cm-1 was deduced for the final and initial states of the transitions, respectively. A Huang-Rhys factor of about 5.7 was determined.