Tuning silicon nitride refractive index through radio-frequency sputtering power

Fabrication of thin-film multilayer structures by sputtering typically requires a multi-cathode deposition machine. This study proposes a simpler approach based on the radio-frequency power modulation; thin silicon nitride (SiNx) thin films were prepared by radio-frequency reactive sputtering in an (Ar + N2) atmosphere at room temperature. The samples were analyzed to highlight the effects of different deposition conditions on the morphological and optical properties of the films in the visible and near/mid-infrared (IR) regions. The refractive index of the films was varied from 1.5 - 2.5 (at ?=800 nm) by tuning the sputtering power. IR reflectance measurements indicated the absence of spurious (oxygen- or hydrogen-based) phases; atomic force microscopy and scanning electron microscopy indicated flat and homogeneous sample surfaces. ? 2021 Elsevier B.V.