Palladium-hydrogen complex in silicon observed by electron spin resonance measurement

We have investigated a palladium-hydrogen complex in silicon by electron spin resonance (ESR) measurement. A new ESR spectrum was detected in a sample diffused with palladium and hydrogen. The hyperfine structure of hydrogen atoms in the ESR spectrum shows that the spectrum originates from a palladium-hydrogen complex containing three hydrogen atoms (Pd-H³). The anisotropic g-value of Pd-H³ shows that the Pd-H³ complex has an anisotropic character of orthorhombic (C^2v) symmetry. The calculated g-values of the Pd-H³ complex are g₁ = 2:12, g₂ = 2:10, and g₃ = 2:03, and the g₂ axis is along the (100) direction. The anisotropic character of orthorhombic (C^2v ) symmetry results from a configuration consisting of one Pd atom at a substitutional site, two equivalent hydrogen atoms at interstitial sites along the (111) direction, and one hydrogen atom at the next-nearest-neighbor interstitial site along the h100i-twofold symmetry axis. We have also studied the dissociation of a platinum-hydrogen complex by thermal treatment. The activation energy for the dissociation of the Pd-H³ complex is estimated to be about 1.6 eV.