Single crystalline epitaxial platinum film on Al₂O₃(0001) prepared by oxygen-doped sputtering deposition

Abstract

We have deposited platinum by inductively coupled plasma-assisted radio frequency sputtering on an Al2O3(0001) substrate annealed at approximately 700 °C with and without oxygen blend. The surface morphology and crystallinity of the obtained Pt films with a thickness of approximately 200 nm were subjected to atomic force microscope (AFM) and X-ray diffraction (XRD) investigations. Without oxygen being introduced during the sputtering process, a (111)-oriented polycrystalline film was obtained. The introduction of oxygen led to the generation of twin single crystalline epitaxial Pt(111) films with a typical fcc(111) surface morphology of hexagonal symmetry.

Structural twinning-induced insulating phase in CrN (111) films

“…[18] On the other hand, when viewed along the [111] direction, CrN consists of alternating planes of Cr 3+ and N 3− ions with a hexagonal structure (Figure 1b), which is similar to that of the (0001) surface of sapphire (α−Al2O3, R−3c). [19,20] The atomic distance between two nearby Cr 3+ ions is 2.93 Å, which is close to the atomic distance between two Al 3+ ions (2.77 Å) in α−Al2O3 (Figure 1c). [21] The (111)-oriented CrN film grown on α−Al2O3 will suffer an extremely large compressive strain up to −5.4%.…”

Oscillatory interlayer coupling in spin Hall systems

“…Depending on the crystallographic direction of Cu, there can be several critical wavevectors 47 . The layers in sample set 1 are grown on oxidized silicon and present a weak (111) crystallographic texture 48 – 50 . Several critical wavevectors therefore contribute to the exchange coupling and obscure a sharp periodic behavior 37 , 47 , 51 .…”

Ultrasmooth Epitaxial Pt Thin Films Grown by Pulsed Laser Deposition

“…Proper substrate selection with a low lattice mismatch is needed to achieve highly crystalline and smooth Pt films. In particular, Pt has been grown epitaxially on MgO, ,,, SrTiO 3 , ,, LaAlO 3 , YSZ, ,, and α-Al 2 O 3 (sapphire). − ,− Due to its commercial availability at a wafer scale, α-Al 2 O 3 has been widely adopted to grow Pt, which results in (111) orientation when deposited on α-Al 2 O 3 (0001). Low lattice mismatch (0.9%) between Pt (111) and α-Al 2 O 3 (0006) makes epitaxial growth possible and reduces the dislocation density at the interface …”

“…For example, while increasing the deposition temperature can improve crystallinity, high-temperature Pt deposition leads to three-dimensional (3D) island formation and high roughness . To address this issue, annealing procedures after deposition are often employed to convert the island morphology into a better-defined thin film . However, this procedure requires relatively thick films (200 nm–1 μm), , incompatible with thin-film current collector applications.…”

“…However, this procedure requires relatively thick films (200 nm–1 μm), , incompatible with thin-film current collector applications. Other growth strategies include the presence of oxygen during deposition, which improves epitaxy by allowing a single in-plane orientation that is necessary to eliminate additional parasitic twining of the Pt crystallites. , Alternatively, Pt electrodes have been grown using a Ti adhesion layer . However, Ti atoms can diffuse rapidly through the Pt electrodes, producing a Ti-rich Pt surface that can oxidize and compromise subsequent deposition on Pt at high temperatures. , …”