For synchrotron measurements, Al2O3 ALD films were deposited on pre-cut 3 mm x 3 mm Si substrates (Pi-KEM, Prime Grade, intrinsic dopant). The substrates originated from a diced 2 inch diameter Si(100) wafer (275±25 μm thick, >200 𝜴 ⋅cm) single-side polished with a thermal dry oxide layer of 20nm±10 percent on both sides. Substrates with varying numbers of ALD layers were prepared, ranging from 2 to 1000. XAS measurements shown in this work were obtained from the 1000 layer sample. For NMR measurements more sample were required, so an 8 inch Si wafer (Picosun) was used and 1000 ALD layers were deposited. Al K-edge XAS total electron yield experiments were conducted at the I09 beamline at Diamond Light source (United Kingdom) in a total electron yield setup.