International audienc

International audienceA complementary suite of in situ synchrotron X-ray techniques is used to investigate both structural and chemical evolution during ZnO growth by atomic layer deposition. Focusing on the first 10 cycles of growth, we observe that the structure formed during the coalescence stage largely determines the overall microstructure of the film. Furthermore, by comparing ZnO growth on silicon with a native oxide with that on Al2O3(001), we find that even with lattice-mismatched substrates and low deposition temperatures, the crystalline texture of the films is dependent strongly on the nature of the interfacial bonds

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In this work, a two-dimensional (2D) titanium disulfide (TiS 2 ) film was grown using tetrakis(dimethylamido)titanium and 1,2-ethanedithiol on a 100 nm thick amorphous SiO 2 /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 TiS 2 upon subsequent thermal annealing under H 2 (4%)/Ar(96%) at 450 °C. The final lamellar TiS 2 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 TiS 2 layers. Repetitive and self-limiting growth behavior on the thermal SiO 2 /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 SiO 2 /Si substrate. Four-point probe resistivity measurements and spectroscopic ellipsometry strongly suggest that the thin films grown on SiO 2 /Si substrates behave as heavily doped semiconductors.

A new high‐vacuum multipurpose diffractometer (called FORTE from the French acronyms of the project) has recently been installed at the tender/hard X‐ray SIRIUS beamline of Synchrotron SOLEIL, France. The geometry chosen allows one to work either in the classical Eulerian four‐circle geometry for bulk X‐ray diffraction (XRD) or in the z‐axis geometry for surface XRD. The diffractometer nicely fits the characteristics of the SIRIUS beamline, optimized to work in the 1.1–4.5 keV range, and allows one to perform unprecedented diffraction anomalous fine structure (DAFS) experiments in the tender X‐ray region, also around non‐specular reflections, covering a large reciprocal‐space volume. Installation of an X‐ray fluorescence detector on a dedicated flange allows simultaneous DAFS and X‐ray absorption (XAS) measurements. The access to the tender X‐ray region paves the way to resonant investigations around the L‐edges of second‐row transition elements which are constituents of functional oxide materials. It also enables access to several edges of interest for semiconductors. Finally, the control architecture based on synchronized Delta Tau units opens up exciting perspectives for improvement of the mechanical sphere of confusion.