Transversely Excited Atmospheric (TEA) CO2 laser‐irradiation of gaseous tetramethylgermane (TMG)–tetramethyltin (TMT) mixtures in Ar results in decomposition of both organometallic compounds and in chemical vapour deposition of nanostructured films analyzed by FTIR and Raman spectroscopy, X‐ray diffraction and electron microscopy. They were shown to have similar morphology and elemental composition and constituents dependent on the TMG–TMT ratio. The analyses confirm the presence of nanosized carbon‐rich (graphitic) structures that incorporate CM and MM (M Ge, Sn) bonds containing an amorphous phase together with crystalline, either β‐Sn or metastable Sn‐rich GeSn alloy. The unique latter constituent is favored at high concentrations of TMG precursor. Copyright © 2010 John Wiley & Sons, Ltd.