EPR spectroscopy of platinum-hydrogen complexes in silcon

Two similar defects in silicon, resulting from doping with platinum in an atmosphere containing water vapor, were studied by means of electron paramagnetic resonance. Both spectra have effective electron spin S=1/2, and exhibit platinum- and hydrogen-related hyperfine structure and remarkable behavior under band-gap illumination. One of the centers has been identified with the recently reported Pt-${\mathrm{H}}_2$ complex. Ligand hyperfine interaction and values of electron localization on two silicon neighbors and two protons have been measured and found to support the model of the Pt-${\mathrm{H}}_2$ center. The second spectrum, labeled Si-NL53, is also reported here. This spectrum has trigonal symmetry and displays hyperfine interactions with three equivalent platinum nuclei. Spin-Hamiltonian parameters of the spectrum were determined and the microscopic model of the defect is proposed. It has been concluded that annealing at high temperature in water-vapor atmosphere provides a high concentration of hydrogen in the bulk silicon and that it can be trapped there forming stable complexes with platinum.