The fundamental reactions in HfO2 atomic layer deposition (ALD) with the precursors tetrakis(ethylmethylamino) hafnium (TEMAH), ozone, and water vapor on Si (1 0 0) surfaces at room temperature (RT) were studied by infrared absorption spectroscopy (IRAS) with a multiple internal reflection geometry. The IRAS results indicated that TEMAH can be adsorbed at OH sites on Si surfaces at RT. Ozone irradiation on the TEMAH-adsorbed Si surface at RT effectively removes hydroaminocarbon adsorbates introduced in the course of TEMAH adsorption, although this treatment provides no OH-group adsorption sites for TEMAH on the Si surface at RT. For further adsorption, water-vapor treatment at around 160 degrees C is effective in restoring the adsorption sites. The IR study suggests that the cyclic process of TEMAH adsorption and ozone treatment at RT followed by OH restoration with water vapor at a temperature of 160 degrees C allows continuous HfO2 deposition. (C) 2012 Elsevier B.V. All rights reserved.