Regulating surface energy and adsorption potential of glass interfaces using mixed-chain chlorosilane multilayer films

Octadecyl-trichlorosilane (OTS) coatings serve as key materials for suppressing spin-destructive wall-collision relaxation in alkali-metal vapor cells because of their high hydrophobicity, low adsorption energy, and high optical transparency. As quantum sensors advance toward higher sensitivity and improved long-term stability, the demand for coatings that retain strong anti-relaxation capability at elevated temperatures continues to increase. Conventional OTS coatings face difficulties in achieving high-temperature endurance while maintaining high hydrophobicity, which creates the need for improved coating materials suitable for next-generation sensor applications. During prolonged operation, OTS films often show nonuniform molecular alignment, weak interfacial bonding strength, and unstable adsorption-energy distributions, and these issues limit further improvement of coating properties. A mixed-chain chlorosilane self-assembled coating is proposed to adjust surface energy and adsorption potential wells through chain-length variation and synergistic intermolecular interactions. This approach aims to enhance interfacial performance and raise the failure temperature of the coating. Contact-angle measurements, surface-roughness characterization, adhesion-force analysis, and Raman spectroscopy are used to systematically examine how mixing ratios influence coating parameters. Experimental results indicate that mixed chlorosilane coatings maintain strong hydrophobicity and stable microstructure at 200 °C temperatures, and an optimal mixing ratio is identified. The study also clarifies that a more uniform distribution of surface adsorption energy plays an important role in extending the polarization lifetime of alkali-metal atoms. The findings offer a new molecular-design pathway for anti-relaxation coatings and provide a material foundation for the development of high-performance quantum sensors.