SIMS of thin films grown by pulsed laser deposition on isotopically labeled substrates

Real-time monitoring of stress evolution during thin film growth by in situ substrate curvature measurement

“…A possible way to rationalize the experimental observation is the aforementioned high oxygen ion mobility in STO and its tendency to be reduced when exposed to the typical deposition conditions of high temperature and relatively low oxygen background pressure. As observed in [ 33 ] and [ 34 ] for films of LAO and YSZ, the STO substrate can become the main source of oxygen for the growing film which act as a sort of oxygen pump for the substrate. Due to the fast oxygen ion diffusion in SDC, the oxygen ion concentration is expected to equilibrate through the film thickness (40 nm) quite fast and no gradient of the oxygen ion concentration is expected in the film after the deposition, as observed for YSZ.…”

“…Using 18 O-labelled STO substrates it was shown that the STO substrate itself can become the main source of oxygen for the growing film, even more than the oxygen molecules in the surrounding gaseous environment of the target material when low background pressure is used. 33,34 This may have very important consequences as far as the stress generation and evolution in the growing film is concerned, as described in Figure 5. Figure 5a shows the XRD analysis of two films of approximately the same thickness (36 -38 nm) of SDC grown on LAO (100) and STO (100).…”

“…Due to the fast oxygen ion diffusion in SDC, the oxygen ion concentration is expected to equilibrate through the film thickness (40 nm) quite fast and no gradient of the oxygen ion concentration is expected in the film after the deposition, as observed for YSZ. 34 Conversely, oxygen ion will be depleted from an STO layer at the film/substrate interface and in this interfacial layer the more reduced STO will have a slightly larger lattice parameter than the less reduce STO in the bulk. Within this scenario, the formation of such a layer would have the equivalent effect of the deposition of thin film of a material in compressive in-plane stress that would bend the substrate inducing a positive variation of the m.d.s.…”

Can solute segregation in ceramic materials be reduced by lattice strain?

“…Depending upon the growth technique and conditions used, changes in the anion and cation nonstoichiometry 46 can occur, as well as additional sources of strain originating from a number of processes such as thermal mismatch, grainboundary effects, 47,48 and reduction in the substrate, 49 all of which may be expected to change at elevated temperatures. However, there are also a number of disadvantages that must be considered which will complicate comparisons to bulk materials.…”

Probing vacancy behavior across complex oxide heterointerfaces

“…Pulsed laser deposition (PLD) has been shown to heavily reduce the underlying oxide substrate during thin-film fabrication, thus increasing the local oxygen vacancy concentration extending from the film-substrate interface (18)(19)(20)(21). Although the mechanism is still obscure, an emerging body of work attributes this highly reduced state to metal oxide films scavenging oxygen from the underlying substrate and adjacent films even under nonreducing deposition atmosphere (15,19,22,23).…”