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We report a systematic study of the superconducting and normal state properties of reactively sputtered Nb0.62Ti0.38N thin films deposited on thermally oxidized Si wafers. The superconducting transition temperature (Tc) was found to increase from 12 K for films prepared on unheated substrates to over 16 K for films prepared on substrates maintained at 450°C. A Nb buffer layer was found to improve Tc by ∼0.5 K for growths at lower substrate temperatures. The films fabricated at 450°C have an amply smooth surface (1.5±0.25 nm root mean square roughness), a sufficiently high Tc, and sufficiently small penetration depth (200±20 nm at 10 K) to be useful as ground planes and electrodes for current-generation 10 K rapid single-flux quantum circuit technology.