In Situ Ellipsometry Study of the Early Stage of ZnO Atomic Layer Deposition on In 0.53 Ga 0.47 As

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Short-range mechanisms in the creation of a ZnO/InGaAs interface

International audienceWe perform quantitative analysis of the X-ray absorption data taken in situ during the earliest cycles of the ZnO atomic layer deposition on atomically flat InGaAs (001) surfaces. As deposition progresses, we observe a transition from an amorphous structure to a nanocrystalline one. The former retains much of the characteristics of a ZnO crystal in the Zn coordination shell, while the latter shows atomic ordering up to at least the third neighbor shell of Zn atoms, despite the absence of Bragg X-ray diffraction peaks. We show that the different chemical preparation of the substrate surface affects the ZnO local structure and that, counterintuitively, a stronger short-range order is obtained in the nanostructures characterized by lower local order at the interface. We propose a model that accounts for these findings

The initial stages of ZnO atomic layer deposition on atomically flat In 0.53 Ga 0.47 As substrates

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Transition Metal Dichalcogenide TiS₂ Prepared by Hybrid Atomic Layer Deposition/Molecular Layer Deposition: Atomic-Level Insights with <i>In Situ</i> Synchrotron X‑ray Studies and Molecular Surface Chemistry

In this work, a two-dimensional (2D) titanium disulfide (TiS2) film was grown using tetrakis(dimethylamido)titanium and 1,2-ethanedithiol on a 100 nm thick amorphous SiO2/Si substrate. The first step of the process relied on the growth of an amorphous film of Ti-amidothiolate by hybrid atomic layer deposition/molecular layer deposition (ALD/MLD) at 50 °C. Such thiolate converted into TiS2 upon subsequent thermal annealing under H2(4%)/Ar(96%) at 450 °C. The final lamellar TiS2 layers tend to be parallel to the substrate surface, as observed by transmission electron microscopy and confirmed at a larger scale by X-ray absorption linear dichroism at the Ti K-edge. The crystalline quality of the resulting films was assessed by Raman scattering. Angle-resolved X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy confirmed the stoichiometry of the TiS2 layers. Repetitive and self-limiting growth behavior on the thermal SiO2/Si substrate was displayed from the early stages of the growth using in situ synchrotron radiation, yielding the Ti and S X-ray fluorescence, as well as in situ ellipsometry and X-ray reflectivity. Modeling the initial ALD and MLD half-cycles on high-surface-area silica beads afforded characterization by more analytical techniques and provided insights into the growth chemistry that agreed with observations on the SiO2/Si substrate. Four-point probe resistivity measurements and spectroscopic ellipsometry strongly suggest that the thin films grown on SiO2/Si substrates behave as heavily doped semiconductors