EFFECT OF AMBIENT RELATIVE HUMIDITY AND SOAKING TIME ON THE FORMATION OF OCTADECYLTRICHLOROSILANE COATINGS ON BOROSILICATE GLASS SUBSTRATES FOR ALKALI-METAL VAPOR CELLS

The most sensitive spin-exchange relaxation-free (SERF) magnetometer generally requires a working temperature greater than 100 ∘ C. To date, octadecyltrichlorosilane (OTS) coating is one of the best candidates for this temperature range. However, the performance and consistency of the OTS coatings within the alkali-metal vapor cells are still poor. In this paper, the formation of OTS coatings on borosilicate glass (BG) substrates was investigated. The effects of ambient relative humidity (RH) on the formation of OTS coatings were examined by atomic force microscopy (AFM) and contact angle measurement. The results showed that 75 % $\%$ RH can improve the order of the OTS coatings and reduce the root mean square (RMS) roughness of the OTS coatings. Under three different ambient RHs, the soaking time of OTS molecules should be greater than 60 $$ min to form complete OTS coating.