In this work, we investigate the integration of graphene nanoplatelets (GNPs) with amorphous germanium (Ge) substrates. The unique properties of amorphous Ge, such as its ability to introduce localized energy states and disorders, significantly influence the electronic interactions within the composite material. These peculiarities, including density variations and distinct optical properties, are crucial in determining the overall behavior of the GNPs–amorphous Ge composite.

Germanium films were deposited onto glass substrates using DC magnetron sputtering, followed by the deposition of GNPs through a dip-coating process. The optical properties of these composites were meticulously characterized using Variable Angle Spectroscopic Ellipsometry (VASE) across a wavelength range of 300–1000 nm and incident angles between 50° and 70°. A comprehensive spectral fit was achieved using a generalized oscillator model incorporating three Gaussian oscillators.

Our findings reveal a significant alteration in the optical properties resulting from the interaction between GNPs and the amorphous Ge substrate. This interaction likely involves the merging of electronic states from both materials, leading to an increased density of states at the Fermi level and enhanced optical absorption. The resulting composite exhibited an improved refractive index and extinction coefficient, suggesting a stronger light–matter interaction.

These enhanced optical properties underscore the potential of GNPs–amorphous Ge composites in various optoelectronic applications. This study provides a deeper understanding of the interaction mechanisms at play, paving the way for the development of advanced materials with tailored optical properties for specific technological applications.