Plasma-Enhanced Atomic Layer Deposition of Nickel Nanotubes with Low Resistivity and Coherent Magnetization Dynamics for 3D Spintronics

Abstract

We report plasma-enhanced atomic layer deposition (ALD) to prepare conformal nickel thin films and nanotubes using nickelocene as a precursor, water as the oxidant agent, and an incycle plasma-enhanced reduction step with hydrogen. The optimized ALD pulse sequence, combined with a post-processing annealing treatment, allowed us to prepare 30 nm-thick metallic Ni layers with a resistivity of 8 μΩ cm at room temperature and good conformality both on the planar substrates and nanotemplates. Thus, we fabricated several micrometers-long nickel nanotubes with diameters ranging from 120 to 330 nm. We report the correlation between ALD growth and functional properties of individual Ni nanotubes characterized in terms of magnetotransport and the confinement of spin-wave modes. The findings offer novel perspectives for Ni-based spintronics and magnonic devices operated in the GHz frequency regime with 3D device architectures.

Ni80Fe20 nanotubes with optimized spintronic functionalities prepared by atomic layer deposition

“…Thereby extrinsic contributions to the peak broadening were less dominant. The spin-wave spectroscopy confirmed the good quality of the PEALD-grown permalloy and its reduced damping compared to PEALD-grown Ni, 48 opening new possibilities for applications in 3D nanomagnonics.…”

“…This value is larger than the one found for low-damping ALD-grown Ni which was 3.9%. 48 We register an anomalous high AMR % value for the NiFe sample prepared with m = 7, and we attribute it to the different morphology and the larger number of holes in the thin film.…”

“…The μ-BLS spectrum of the permalloy NT is much richer than the ones reported for PEALD-prepared nickel nanotubes. 48 We attribute the larger number of resolved spin-wave resonances in Fig. 7f to the lower damping of NiFe compared to Ni.…”

“…In ref. 48 the authors argued that the confined modes observed for the Ni nanotubes reflected standing spin waves formed in azimuthal direction inside the ferromagnetic shell. High-frequency peaks in the spectrum were identified with spin waves of correspondingly shorter wavelength fulfilling the constructive interference condition along the circumference.…”

Area Selective Chemical Vapor Deposition of Metallic Films using Plasma Electrons as Reducing Agents

“…For instance, iron oxide films can be deposited at temperatures ranging from 150 °C to 500 °C by thermal ALD [36][37][38][70][71][72], and by PEALD [73]. Cobalt and nickel films can be deposited at temperatures ranging from 125 °C to 350 °C by thermal ALD [41,[74][75][76][77][78], and PEALD [39,[79][80][81]. However, issues such as precursor decomposition (i.e., CVD growth) and the loss of the characteristic self-limiting component of ALD, have been reported in many of these processes.…”