A time-of-flight (TOF) ion scattering and direct recoil spectrometer (ISS/DRS) has been developed to study the surface composition and reconstruction of metals, metal-oxides, and semiconductors, and to provide in situ characterization of the thin-film deposition process. The in situ, real-time study of Pb, Zr, and Ru ultrathin films produced by ion beam sputter deposition is presented here as the first demonstration of TOF-ISS as a means of characterizing monolayer and submonolayer growth, both in UHV and in mTorr oxygen background. The capability of performing surface analysis at pressures >10(-3) Torr is unique to pulsed ion beam surface analysis among surface analytical methods and enables the in situ monitoring of oxide thin-film growth processes and surface-gas phase reactions. Using angular-resolved ISS combined with Auger electron spectroscopy, we studied the oxygen adsorption and reconstruction of (001) oriented InSb thin-film surfaces. It was found that the adsorption of molecular oxygen on the InSb (001) surface is consistent with the Langmuir model. Oxygen adsorption preferentially occurs on the antimony sites corresponding to the extension of the lattice into the vacuum and reduces the inward contraction of the first two layers of the clean InSb (001) surface relative to the bulk atomic spacing.