Anomalous isotopic effect on the lattice parameter of silicon

H-C Wille; Yu V Shvyd'ko; E Gerdau; M Lerche; M Lucht; H D Rüter; J Zegenhagen

doi:10.1103/PhysRevLett.89.285901

Anomalous isotopic effect on the lattice parameter of silicon

Phys Rev Lett. 2002 Dec 31;89(28 Pt 1):285901. doi: 10.1103/PhysRevLett.89.285901. Epub 2002 Dec 27.

Authors

H-C Wille¹, Yu V Shvyd'ko, E Gerdau, M Lerche, M Lucht, H D Rüter, J Zegenhagen

Affiliation

¹ Institut für Experimentalphysik, Universität Hamburg, D-22761 Hamburg, Germany.

PMID: 12513163
DOI: 10.1103/PhysRevLett.89.285901

Abstract

The difference Delta(a)=a(30)-a(28) of the lattice parameter of 30Si and 28Si crystals is measured over a temperature range from 4.7 to 700 K. In disagreement with existing knowledge, the strongest isotopic effect is not detected at the lowest achieved temperature T=4.7 K. An anomalous behavior is observed: The relative difference |Delta(a)/a| attains its maximum value of 56.8(5) ppm at T=75(10) K. The anomalous behavior is attributed to the influence of phonon modes with negative Grüneisen parameters. At T=700 K the effect still amounts to 30% of the maximal value. The experimental data are consistent with an approach based on the density-functional perturbation theory.