Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9 % corresponding to an unexpected 9.9 cm-1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.
@article{arxiv.1604.04391,
title = {Accurate strain measurements in highly strained Ge microbridges},
author = {A. Gassenq and S. Tardif and K. Guilloy and G. Osvaldo Dias and N. Pauc and I. Duchemin and D. Rouchon and J-M. Hartmann and J. Widiez and J. Escalante and Y-M. Niquet and R. Geiger and T. Zabel and H. Sigg and J. Faist and A. Chelnokov and F. Rieutord and V. Reboud and V. Calvo},
journal= {arXiv preprint arXiv:1604.04391},
year = {2016}
}