TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method comprises: repeating steps (b)-(d) before beginning step (e) until the desired silicon dioxide layer thickness is obtained; and optionally repeating steps (e)-(g) until the desired aluminum oxide layer thickness is obtained. The method comprises: (h) annealing the aluminum oxide/silicon dioxide stack issued of step (g) at 400-900 degrees C, preferably 400-425 degrees C in an atmosphere of nitrogen. The duration of the annealing step is no more than 10 minutes. Preferred Components: The silicon containing compound is BDEAS. The silicon dioxide layer has a thickness of 1-15 nm, and the aluminum oxide layer has a thickness of 30 nm. The silicon containing compound comprises at least 97% of at least one silicon containing compound comprising BDEAS, BDMAS, DIPAS or DTBAS, and molybdenum (200 ppb to 5 ppm), iron (1000 ppb to 5 ppm), copper (200 ppb to 5 ppm), tantalum (200 ppb to 10 ppm). The aluminum containing compound comprises at least 97% of at least one trimethylaluminum or trimethylaluminum and molybdenum (200 ppb to 5 ppm), iron (1000 ppb to 5 ppm), copper (200 ppb to 5 ppm), tantalum (200 ppb to 10 ppm). EXAMPLE - The silicon dioxide layer was deposited on an n-type silicon substrate by plasma-enhanced atomic layer deposition. Oxygen plasma was used as a reactant in combination with bis(diethylamino)silane. The silicon precursor was stored in a stainless steel canister heated at 50 degrees C. The precursor was vapor drawn. The substrate temperature was regulated at 150 degrees C. The precursor was first introduced into the reactor (50 ms pulse). Oxygen was introduced continuously in the reactor as well as argon. After a 2 s purge sequence, plasma was activated for 4 s. This sequence was followed by a 2 s purge sequence. The pressure in the reactor was 0.2 Pa. The aluminum oxide layer was deposited on the previously deposited silicon dioxide layer from trimethylaluminum (TMA) and oxygen plasma. TMA had a high vapor pressure thus the vapor was drawn into the reactor. The precursor was introduced into the reactor with a 10 ms duration pulse. Oxygen was introduced continuously in the reactor as well as argon. A first 10 ms TMA pulse was introduced into the reactor followed by a 2 s purge sequence. Plasma was then activated for 4 s and followed by a 2 s purge sequence to give the aluminum oxide/silicon dioxide stack.