**2. Experimental**

#### *2.1. ALD and Precursors*

All thin films were deposited in a F-120 Sat reactor (ASM Microchemistry, Helsinki, Finland) at a reactor temperature of 300 ◦C, unless otherwise stated. The temperature was chosen to comply with applicable temperatures for the binary oxide processes. Nitrogen was used as a purging gas, supplied from gas cylinders (99.999%, Praxair Norway, Oslo, Norway) and run through a Mykrolis purifier (Avantor Fluid Handling LLC, Devens, MA, USA) to remove oxygen and water impurities. The purging gas was maintained at a 300 cm<sup>3</sup> min−<sup>1</sup> flow rate, giving an operating pressure of 2.6 mbar throughout the process.

Co(thd)2 (99.9+%, Volatec, Porvoo, Finland), Gd(thd)3 (99.9%, Strem Chemicals Inc., Kehl, Germany) and Ca(thd)2 (99.9+%, Volatec) were used as cation sources, maintained in open boats in the reactor at 115 ◦C, 140 ◦C, and 198 ◦C, respectively (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate). All precursors were re-sublimated before use to enhance purity. O3 was used as the oxygen source, made from O2 gas (99.6%, Praxair Norway) with an In USA (AC-2505) ozone generator producing 15 mass% O3 in O2. Pulse durations were set to 1.5 s for all metal precursors, whereas ozone was pulsed for 5 s subsequent to Co(thd)2 and 3 s subsequent to Gd(thd)3 and Ca(thd)2 pulses. All purge durations were set to 2 s. The pulse and purge durations were chosen in agreemen<sup>t</sup> with previous reports of self-limiting growth using these precursors in similar reactor infrastructures.

#### *2.2. Substrates and Annealing*

Films were routinely deposited on 1 × 1 cm<sup>2</sup> Si(100) for characterization of thickness, whereas 3 × 3 cm<sup>2</sup> Si(100) substrates were used for compositional analysis with X-ray fluorescence (XRF) and for investigating any thickness gradients. Selected films were deposited on 1 × 1 cm<sup>2</sup> LaAlO3 (100)pseudocubic (LAO, MTI Corp., Richmond, CA, USA), YAlO3 (100) (MTI Corp.) and YAlO3 (010) (YAP, MTI Corp.) for the facilitation of epitaxial growth. The investigation of conformality on high-aspect-ratio substrates was carried out on silicon substrates with parallel grooves of 20 μm depth and 10 μm width (SINTEF IKT made by reactive ion etching with the Bosch process).

The selected films were annealed at 650 ◦C for 30 min in 1 atm air in an OTF-1200X rapid thermal processing (RTP) furnace (MTI Corp., Richmond, CA, USA) to facilitate crystallization prior to structural investigation.
