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 (C2v) 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 direction. The anisotropic character of orthorhombic (C2v) symmetry results from a configuration consisting of one Pd atom at a substitutional site, two equivalent hydrogen atoms at interstitial sites along the direction, and one hydrogen atom at the next-nearest-neighbor interstitial site along the -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.