Raman spectra of amorphous isotope-enriched 74Ge with low-strained Ge nanocrystals

• Amorphous Ge samples were produced by plasma-enhanced chemical vapor deposition.
• These samples containing 86% of 74Ge isotope were deposited from 74GeF4.
• The nanocrystalline phase formed by thermal or laser annealing was registered.
• The arrays of Ge nanocrystals in the amorphous Ge matrix were found to be low-strained.

Our objective is to study Raman spectra from 74Ge isotope enriched nc-Ge/amorphous-Ge structures, given the expected minimal influence of the matrix on the nanocrystalline phase in the structures with a modified isotope composition. We also assess the potential of plasma-enhanced chemical vapor deposition for producing germanium nanocrystals in the amorphous matrix from germanium tetrafluoride enriched with 74Ge isotope. The nanocrystal phase was formed by annealing the samples in different conditions. The nc-Ge peak width and position in the Raman spectrum agree well with the theoretical data. The out-of-plane elastic strain of the nc-Ge lattice in the annealed structures, estimated from the shift of the Ge (111) and (220) diffraction peaks, was of the order of 1∙10− 3.