Thermal stability of SrTiO3/SiO2/Si Interfaces at Intermediate Oxygen Pressures

Abstract

The thermal stability of epitaxial SrTiO3 thin films grown by molecular-beam epitaxy on Si (001) has been studied using x-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and thermodynamic calculations. Our studies focus on the stability of the SrTiO3/Si structures under the conditions typically employed in the pulse laser deposition (PLD) growth of complex metal oxide heteroepitaxy on Si. We observe additional Bragg peaks in thermally treated SrTiO3 buffered Si structures, corresponding to possibly TiSi2 and/or SrSiO3, reaction products which are consistent with the reaction schemes we propose. In addition, OM and SEM reveal microstructures that are not readily accounted for solely by the solid state reactions as put forth by previous workers but can be reasonably explained by our proposed reaction schemes. Using our observations and thermodynamic analysis, we argue that reactions involving the gaseous species SiO(g), the reactivity of which has not been previously considered in this system, are important. We attribute the onset of degradation of the SrTiO3 film at high temperatures, to the circular void forming reaction Si(s)+SiO2(s)→2SiO(g) at the interface and suggest that the reactions considered by previous workers involving all solid state reactants occurs only at the conclusion of degradation. Our results points to the need for keeping the PLD temperature as low as possible to minimize the production of reactive SiO(g) in avoiding the deleterious reactions.

Oxygen vacancy-mediated room-temperature ferromagnetism in insulating cobalt-substituted SrTiO3epitaxially integrated with silicon

“…For compositions 10-40%, the symmetric 2θ−θ scan ( become amorphized and that a thin (~1.5 nm) SiO x layer has also formed. The reason for the loss of crystallinity in the undoped STO layer are still unclear and may be due to either preferential amorphization as a result of the TEM sample preparation [40] or to reaction of the thin STO layer with silicon forming silicates and silicides [41][42].…”

Heteroepitaxy of Nd0.67Sr0.33MnO3 on silicon for bolometric x-ray detector application

“…13 The final slow cooling of the multilayer stack at 1°C / min in ϳ400-500 Torr O 2 is also conducive to the optimal oxygenation of the NSMO layer. Interestingly, before the CeO 2 and BTO depositions, it was found that the 3°C / min ramp rates yielded better samples than a 1°C / min or 2°C / min ramp rate, suggesting that minimizing the time the sample spent at high temperature ͑avoiding reactions͒ is an important factor due to the potential for interfacial reactions mediated by the silicon dioxide decomposition interfacial reaction SiO 2 +Si → 2SiO͑g͒.…”

Self-Sealing Complex Oxide Resonators

“…Unlike vdW materials, which are fundamentally at a disadvantage due to the inevitability of the weak vdW interaction with the substrate, complex oxides are able to form chemical bonds with the substrate at high temperatures. 17 Therefore, complex oxides promise a stronger adhesion to the substrate than 2D materials. For example, using direct wafer bonding (DWB), single crystal complex oxides such as LiNbO 3 have been shown to be able to bond directly onto other substrates like Si 18 − 20 to create submicron thick MEMS resonators.…”