Oxygen-Activated Surface Chemistry Enabling Low-TemperatureCVD of RuS for Broadband Photodetectors

초록

Ruthenium sulfide (RuS2) is a promising channel material for light detection because of its high carrier mobility, suitable bandgap, and long-term stability. However, conventional synthesis requires high temperatures and predominantly yields nanoparticle-based structures, which are unsuitable for optoelectronic devices. In this work, we demonstrate the direct growth of high-quality RuS2 films at a remarkably low temperature of 300 degrees C, enabled by an O2 coinjection strategy during chemical vapor deposition (CVD). Systematic characterization reveals that O2 plays a critical role in facilitating low-temperature growth while suppressing metallic Ru or RuO2 formation. Machine-learning interatomic potential (MLIP)-based theoretical analysis on surface reactions reveals that slightly oxidized RuS2 surfaces formed under O2/H2S coinjection enhance H2S activation, surface reactivity, and precursor-ligand elimination, thereby supporting low-temperature RuS2 CVD growth. Consequently, the O2-assisted process yields phase-pure, polycrystalline RuS2 films with minimal oxygen incorporation. Metal-semiconductor-metal (MSM) RuS2 photodetectors exhibit broadband photoresponse across the visible to near-infrared (NIR) region, very low dark current (similar to 1.7 nA), and high responsivity, along with fast response times (47/65 mu s) and excellent stability. These findings demonstrate that O2-assisted CVD provides a robust, low-temperature route for synthesizing RuS2 thin films and highlight their potential for next-generation optoelectronic applications.

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