Structural evolution of platinum thin films grown by atomic layer deposition

Abstract

The structural properties of Pt films grown by atomic layer deposition (ALD) are investigated with synchrotron based x-ray scattering and x-ray diffraction techniques. Using grazing incidence small angle scattering, we measure the lateral growth rate of the Pt islands to be 1.0 Å/cycle. High resolution x-ray diffraction reveals that the in-plane strain of the Pt lattice undergoes a transition from compressive strain to tensile strain when the individual islands coalescence into a continuous film. This transition to tensile strain is attributed to the lateral expansion that occurs when neighboring islands merge to reduce their surface energy. Using 2D grazing incidence x-ray diffraction, we show that the lattice orientation becomes more (111) oriented during deposition, with a sharp transition occurring during coalescence. Pt ALD performed at a lower deposition temperature (250 °C) is shown to result in significantly more randomly oriented grains.

Electrical Properties of Ultrathin Platinum Films by Plasma-Enhanced Atomic Layer Deposition

“…16−19 Pt is one of the materials known to present nucleation challenges with t-ALD. 20 The high surface energy of Pt leads to Volmer–Weber (VW) growth, forming islands at the early stages of nucleation. 21,22 This growth behavior sets a lower limit on the minimum closed-film thickness, as these Pt islands must grow large enough to connect to neighboring islands before the film becomes continuous.…”

Atomic layer deposition of ruthenium using an ABC-type process: Role of oxygen exposure during nucleation

“…Figures 3(a)-3(c) depict that the islands are not monodisperse and aggregate into larger clusters, resembling previous nucleation studies for noble metal ALD. 62,68,77,78 Both small and large islands are present, corresponding to a broad particle size distribution, which suggests that the formation of nuclei does not solely occur during the first few cycles but throughout the deposition process. Figures 3(d) and 3(e) illustrate that when the islands grow in size, eventually island coalescence and film closure occurs.…”

Kevlar‐Based Supercapacitor Fibers with Conformal Pseudocapacitive Metal Oxide and Metal Formed by ALD

“…This capacitance is larger than 30 μF per unit specific surface area typically expected for a planar double layer . The ALD Pt is known to experience island growth, which gives it a rough texture, and the relatively large capacitance likely results from an increase in surface area due to roughness and/or from pseudocapacitive oxygen sites on the Pt or within the underlying aluminum oxide. The measured capacitance also confirms that the ALD Pt process is able to sufficiently coat each fiber within the yarn structure to develop an electrically accessible charge double layer on the total fiber specific surface area, which is much larger than the lateral yarn surface area.…”