Phase formation in intermixed Ni–Ge thin films: Influence of Ge content and low-temperature nucleation of hexagonal nickel germanides

Abstract

In this study, we focus on phase formation in intermixed Ni-Ge thin films as they represent a simplified model of the small intermixed interface layer that is believed to form upon deposition of Ni on Ge and where initial phase formation happens. A combinatorial sputter deposition technique was used to co-deposit a range of intermixed Ni-Ge thin films with Ge concentrations varying between 0 and 50 at.%Ge in a single deposition on both Ge (100) and inert SiO 2 substrates. In situ X-ray diffraction and transmission electron microscopy where used to study phase formation. In almost the entire composition range under investigation, crystalline phases where found to be present in the as-deposited films. Between 36 and 48 at.%Ge, high-temperature hexagonal nickel germanides were found to occur metastabily below 300°C, both on SiO 2 and Ge (100) substrates. For Ge concentrations in the range between 36 and 42 at.%, this hexagonal germanide phase was even found to be present at room temperature in the asdeposited films. The results obtained in this work could provide more insight in the phase sequence of a pure Ni film on Ge.

Ni/GeSn solid-state reaction monitored by combined X-ray diffraction analyses: focus on the Ni-rich phase

“…This phase is related to the hexagonal "-Ni 5 (Ge 0.9 Sn 0.1 ) 3 metastable phase (P6 3 /mmc space group). Thus, as demonstrated for the Ni/Ge (De Schutter et al, 2014, 2016 and suspected for the Ni/ SiGeSn (Wirths, Troitsch et al, 2015) systems, a metastable hexagonal stannogermanide phase is obtained at low temperature for the Ni/Ge 0.9 Sn 0.1 system. This identification supports our assumption that the shift observed for the Ni-rich peak at low temperature and concomitant to the total consumption of Ni is linked to stoichiometry variations.…”

Facile Access to an Active γ‐NiOOH Electrocatalyst for Durable Water Oxidation Derived From an Intermetallic Nickel Germanide Precursor

“…The molecular complex 2 was subjected to thermolysis under hot‐injection conditions at 250 °C in oleylamine to produce black powdered NiGe with ≈75 % yields (see Supporting Information ). Note that a NiGe 2 phase was expected from the precursor Ni:Ge ratio, however, NiGe 2 is a metastable phase and does not exist in the Ni‐Ge phase diagram (Figure S2) [20] . Hence, a thermodynamically stable NiGe phase is formed.…”

“…Note that aN iGe 2 phase was expected from the precursor Ni:Ge ratio,h owever, NiGe 2 is am etastable phase and does not exist in the Ni-Ge phase diagram ( Figure S2). [20] Hence,athermodynamically stable NiGe phase is formed. Thephase-purity,morphology,microstructure,c omposition, surface area, and the electronic state of NiGe were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), elemental mapping,inductively coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis,F ourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS).…”

Impurity-enhanced solid-state amorphization: the Ni–Si thin film reaction altered by nitrogen

“…Diffraction of the CuK α radiation (λ = 1.54Å) was recorded with a linear detector (Vantec D8) spanning 20 • in 2θ. 47 Ex situ, high-resolution XRD was performed at the DiffAbs beamline 48 at the Soleil synchrotron (λ = 1.54Å). Using a 6-circle goniometer and a X-ray pixel area detector (XPAD), a large section of reciprocal space can be probed in a short timeframe.…”