Palladium--Hydrogen Complex in Silicon Observed by Electron Spin Resonance Measurement

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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 $g_{1} = 2.12$, $g_{2} = 2.10$, and $g_{3} = 2.03$, and the $g_{2}$ axis is along the $\langle 100 \rangle$ 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 $\langle 111 \rangle$ direction, and one hydrogen atom at the next-nearest-neighbor interstitial site along the $\langle 100 \rangle$-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.
2011-09-25