Atomic layer deposition (ALD) using (MeCp)PtMe 3 and O 2 gas or O 2 plasma is a well-established technique for the deposition of thin films of Pt, but the potential of ALD to deposit platinum oxide (PtO x ) has not yet been systematically explored. This work demonstrates how PtO x can be deposited by plasma-assisted (PA)-ALD in a temperature window from room temperature (RT) to 300°C by controlling the O 2 plasma and (MeCp)PtMe 3 exposure. With increasing substrate temperature, the thermal stability of PtO x decreases and the reducing activity of the precursor ligands increases. Therefore, longer O 2 plasma exposures and/or lower (MeCp)PtMe 3 exposures are required to obtain PtO x at higher temperatures. Furthermore, it is established that, during the nucleation stage, PtO x ALD starts by the formation of islands that grow and coalesce during the initial $40 cycles. Closedlayer thin films of PtO x with an O/Pt ratio of 2.5 can be deposited at 100°C with a minimal thickness of only $2 nm. It is also demonstrated that a conformality of $90% can be reached for PtO x films in trenches with an aspect ratio of 9 when using optimized O 2 plasma and precursor exposure times.

Ultralow-power gas sensing devices need to operate without an energy consuming heater element. This requires the design of sensing devices that are so efficient that they can operate at room temperature (RT). Here, we report on the RT sensing performance of atomic layer deposition (ALD) prepared i-ZnO and Al-doped ZnO sensing devices. The sensitivity of these devices has been catalytically enhanced with ALD Pt nanoparticles (NPs). It was shown that the size distribution of the Pt NPs can be controlled by the number of Pt-ALD cycles. The Pt-enhanced sensing devices showed a reversible, proportional change in current response at RT upon exposure to O2 and CO. O2 could be detected, diluted in N2, down to 0.5%. CO could be detected, diluted in N2 in the presence of O2 and H2O, down to 20 ppm. Reference devices without Pt NPs showed no response, indicating the importance of the Pt NPs for the sensing mechanism.

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