Atomic layer deposition (ALD) is a thin film growth technique based on sequential, self-limiting surface reactions. ZnO ALD can be achieved using sequential exposures of Zn(CH@sub2@CH@sub3@)@sub2@ [diethylzinc (DEZ)] and H@sub2@O at 180°C. This talk will characterize the surface chemistry and film growth during ZnO ALD using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) spectroscopy and 4-point probe resistivity measurements. The QCM measurements display a staircase structure that is consistent with a mass increase of 110 ng/cm@super2@ or 2.0 Å per DEZ/H@sub2@O reaction cycle. The FTIR results show that the growing ZnO surface displays vibrational modes consistent with ZnOH* species following the H@sub2@O exposures. DEZ exposure converts these species back to Zn(CH@sub2@CH@sub3@)* species. The background infrared absorbance of the ZnO film also increases progressively with number of DEZ/H@sub2@O cycles as expected for an electrical conductor. The 4-point probe investigations reveal dramatic oscillations in the ZnO film resistivity that are dependent on both film thickness and adsorbed surface species. The resistivity is much higher with ZnCH@sub2@CH@sub3@* species than with ZnOH* species. This resistivity dependence on surface species may be important for an understanding of ZnO gas sensors. The ZnO ALD films are polycrystalline and have an electrical resistivity of ~10@super-2@ @ohm@cm. Excellent ultrathin and conformal ZnO ALD films are observed on ZrO@sub2@ and BaTiO@sub3@ particles.