Effect of sputter pressure on Ta thin films: Beta phase formation, texture, and stresses

Ellis, Elizabeth A.; Chmielus, Markus; Baker, Shefford P.

doi:10.1016/j.actamat.2018.02.050

Cited by 38 publications

(9 citation statements)

References 67 publications

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“…The presence of (002) diffraction peak near θ=33.5° and (011) peak near 38.5° conclusively suggests the formation of mixed phases, i.e., -Ta and -Ta in these samples. However, it is reported that the phase of Ta thin films can be tuned by tunning the sputtering rate, energy of the sputtered species and working pressure [29] [30]. The presence of (011) peak of -Ta of even 3 nm nominally thin Ta film in the bilayer conclusively suggests that the Ta films grew crystalline over amorphous CFB even at ultrathin regime unlike previous report [31].…”

Section: A X-ray Diffraction (Xrd) Studymentioning

confidence: 81%

Impact of Ferromagnetic Layer Thickness on the Spin Pumping in Co60Fe20B20/Ta Bilayer Thin Films

Hait

Husain

Gupta

et al. 2021

Preprint

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We report the tuneable spin angular momentum transfer (spin pumping) from Co60Fe20B20 (CFB) amorphous alloy into the Ta heavy metal nanolayers. All the films are grown on Si (100) substrate at room temperature using ion-beam sputtering technique. Structural studies reveal that the grown Ta films over amorphous CFB are crystalline even at ultrathin regime. The bilayers possess very low interface roughness (<0.5 nm) and are continuous throughout the thickness range. Comparative analysis of the spin pumping in CFB (4, 6 and 8 nm) as a function of the Ta thickness (vary from 1 to 10 nm in step of 1nm) has been performed employing ferromagnetic resonance (FMR) spectroscopy. It is observed that the effective damping increase exponentially with the increase of Ta i.e., follows ballistic spin transport) in two series of CFB (4nm)/Ta (0-10nm) and CFB(6nm)/Ta (0-10nm) bilayers, which is characteristic of normal spin pumping. However, the anomalous behaviour has been observed for CFB (8nm)/Ta (0-10nm) bilayer series where the spin current generated in Ta with the thicker CFB behaves oppositely. The results demonstrate the strong dependence of ferromagnet thickness on the spin pumping into the Ta nanolayers. This study paves the way to choose suitable ferromagnetic layer thickness for spin current induced switching applications in spintronics.

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Section: A X-ray Diffraction (Xrd) Studymentioning

confidence: 81%

Impact of Ferromagnetic Layer Thickness on the Spin Pumping in Co60Fe20B20/Ta Bilayer Thin Films

Hait

Husain

Gupta

et al. 2021

Preprint

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“…In the case of Ta, no transient feature is observed in the

and

vs.

curves, and the β-Ta phase is formed, which is intrinsically more resistive (typical resistivity of 170 µΩ·cm compared to 25–30 µΩ·cm for bcc-Ta [ 128 ]) and of lower crystal symmetry. It was proposed that this phase is stabilized by minimization of interface energies [ 128 ], although other authors argued that phase formation is governed by the presence of TaO x interlayer and template (epitaxial) growth [ 131 ].…”

Section: Interface Reactivity and Structure Formationmentioning

confidence: 99%

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

et al. 2020

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Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of ~2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal β-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.

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“…Other candidate phases and their diffraction patterns are included below the diffractogram for comparison. A BCC structure is expected when employing Ti adhesion layers [16,17]. Tantalum films had a fiber texture with most grains having a (110) and (211) out-of-plane orientation aligned to the LiF (100) substrate normal.…”

Section: B Tantalum Targetsmentioning

confidence: 99%

Estimates of Ta strength at ultrahigh pressures and strain rates using thin-film graded-density impactors

et al. 2019

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Effect of sputter pressure on Ta thin films: Beta phase formation, texture, and stresses

Cited by 38 publications

References 67 publications

Impact of Ferromagnetic Layer Thickness on the Spin Pumping in Co60Fe20B20/Ta Bilayer Thin Films

Impact of Ferromagnetic Layer Thickness on the Spin Pumping in Co60Fe20B20/Ta Bilayer Thin Films

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

Estimates of Ta strength at ultrahigh pressures and strain rates using thin-film graded-density impactors

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