Abstract
AbstractDielectric barium strontium titanate films were deposited on MgO (001) substrate by pulsed‐laser deposition (PLD) and monitored in situ by means of reflection high‐energy electron diffraction and time‐resolved X‐ray diffraction (TRXRD). TRXRD showed two growth periods of the BSTO film and a transformation in the crystalline structure was detected as the thickness exceeds 80 nm. The occurrence of two different crystalline regions, namely BSTO1 and BSTO2 was proved by X‐ray diffraction (XRD). Ex situ transmission electron microscopy (TEM) techniques, including diffraction‐contrast as well as high‐resolution TEM, nanobeam electron diffraction, and scanning TEM in combination with energy‐dispersive X‐ray spectroscopy reveal structural and microchemical peculiarities of the BSTO film. By these TEM analyses, the presence of the two different regions BSTO1 and BSTO2 within the PLD‐grown BSTO layer was demonstrated. Regions of phase BSTO2 were found on top of nanoscaled MgO islands formed on the substrate surface during annealing at high temperature. While the majority phase BSTO1 has a single‐crystalline structure over wide ranges, BSTO2 regions seem to be poly‐ or even nanocrystalline, and the chemical composition of the two phases is also different. The transition in the growth periods is presumably related to the occurrence of BSTO2 regions during layer growth.
Highlights
Introduction grown onMgO substrate.[1,4] Zhu et al.[3] recorded the highest dielectric properties for BSTO/MgO grown at 25 Pa (187 mTorr)
For Ba0.5Sr0.5TiO3 (BSTO) films grown on MgO, the choice of the present study, the oxygen pressure was set to 200 mTorr based the growth conditions such as oxygen pressure, substrate selec- on the record in the dielectric properties achieved by former tion, and substrate temperature for a certain film thickness has investigations.[3]
We have studied the evolution of the crystalline structure of BSTO films in terms of lattice parameters and residual strain as a function of the film thickness using in situ synchrotron X-ray diffraction during the growth at a temperature of T = 850 °C
Summary
MgO substrate.[1,4] Zhu et al.[3] recorded the highest dielectric properties for BSTO/MgO grown at 25 Pa (187 mTorr). In. For Ba0.5Sr0.5TiO3 (BSTO) films grown on MgO, the choice of the present study, the oxygen pressure was set to 200 mTorr based the growth conditions such as oxygen pressure, substrate selec- on the record in the dielectric properties achieved by former tion, and substrate temperature for a certain film thickness has investigations.[3] The internal strain changed during the growth. Correction added on 23 July 2020, after first online publication: Projekt Deal funding statement has been added
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