As the semiconductor industry advances towards increasingly complex 3D structures, it requires deposition techniques which offer atomic level control and conformality. Atomic layer deposition (ALD) has emerged as a bottom-up method to meet these demands. This work investigates two surface blocking approaches for area-selective ALD (AS-ALD) to inhibit growth of aluminum oxide (Al2O3) on silicon dioxide (SiO2) surfaces. Experiments were conducted using in-situ quartz crystal microbalance (QCM) to monitor mass changes in real time. A drift correction method was developed to improve the accuracy of data affected by thermal fluctuations. The effectiveness of Dimethylaminotrimethylsilane (DMATMS) as the small molecule inhibitor (SMI) and Alcohol X as the coadsorbate was evaluated across various conditions. Experiments were conducted to test all combinations using Trimethylaluminum (TMA) and bis-dimethylamino-diamino-aluminum (BDMADA- Al) as the precursors, with water (H2O) and tert-butanol (t-BuOH) as the co-reactants, at two temperatures: 120°C and 285°C. The first approach, the ABC process, involved an inhibitor soak (“C”) followed by cycles of precursor (“A”), coreactant (“B”) and inhibitor (“C”) reapplication which demonstrated promising blocking ability. The second approach, the ABCD process introduced the coadsorbate (“D”) with the precursor to enable competitive adsorption while retaining the inhibitor soak and the reapplication step. Results using coadsorbate showed better blocking performance as compared to the ABC process.