Infra-red photoluminescence (PL) spectra of zinc and copper related defects in silicon are presented in this thesis. Seven new PL systems with principal zero phonon lines at 919.8, 943.67, 945.8, 1033.5, 1059.9, 1090.7 and 1129.8 meV are discussed. All of the spectra can be classified as being due to isoelectronic bound exciton ( IBE ) recombination. Although the identities of the binding centres have not been conclusively established clear evidence has been obtained in most cases for the involvement of at least one specific transition metal ( TM ) impurity element. The PL systems at 945.8, 919.8 and 1059.9 meV are all observed in silicon diffused with zinc and another TM. The 945.8 meV system is observed in silicon diffused with zinc at 1100° C for 16 hours. The system is not created by interstitial Mn and substitutional Zn as previously suggested. The 919 meV system is observed in silicon co-diffused with zinc and copper at 1100° C for 16 hours, while the 1059.9 meV system is most clearly observed in SisFeZn quenched from 1000° C. For silicon implanted with zinc the 1129.8 and 1090.7 meV systems are observed. Both of these systems have ground state and excited state splittings placing them in a minority group of IBE centres in silicon associated with deep acceptors and including the indium and thallium systems. The quenching rate is found to be crucial for samples diffused with copper only. Slow quenches produce the 1034 meV SK system. Zeeman studies on the zero phonon lines of this centre reveal a singlet - triplet nature indicative of a strong central cell potential about the defect as well as a strong crystal field reaction. Rapid quenches combined with * low copper concentrations produces the 943.7 Cu PL system. Uniaxial stress and magnetic field measurements on this centre suggest that the two lowest energy transitions arise from bound exciton recombination at a defect with tetrahedral or near tetrahedral symmetry. Diffusion rate calculations show that a single interstitial copper atom is not the most likely configuration . A larger defect involving one or more atoms in a Td arrangement is more likely, perhaps similar to to those already reported for the Mn4 and Li^ defects in PL and for the NL22 Fe related centre in EPR. It is concluded that diffusion is not a suitable method of introducing transition metal impurities into silicon since the process is extremely susceptible to contamination. Implantation of the desired element followed by rapid thermal annealing is suggested as a much more promising avenue of investigation since this method affords much more control over the concentration, implantation depth and most importantly of all, the identity of the chemical element introduced into the host crystal.