Andrej Furlan

Ge was deposited as thickness gradient films at temperatures up to 800 °C by direct current (DC) and high power pulsed magnetron sputtering (HPPMS). Structural characterization shows increased crystallization with increasing substrate temperature and film thickness. Thermal conductivity was measured by a novel high‐throughput time‐domain thermo‐reflectance method. Thermo‐electrical properties correlate to the degree of crystallization. Conductivities increase with increasing substrate temperature up to 500 °C. For higher temperatures the trend reverses. A room temperature deposited/annealed film displays smaller crystallites (10 nm) and lower thermal conductivity (5 Wm⁻¹ K⁻¹) compared to 25 Wm⁻¹K⁻¹ for hot DC deposition. Compared to DC, HPPMS films show higher thermal conductivities up to 45 Wm⁻¹K⁻¹.

We investigate the amorphous structure, chemical bonding, and electrical properties of magnetron sputtered Fe _{1− x} C _x (0.21 ⩽ x ⩽ 0.72) thin films. X-ray, electron diffraction and transmission electron microscopy show that the Fe _{1− x} C _x films are amorphous nanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeC _y , and a carbon-rich matrix. Pair distribution function analysis indicates a close-range order similar to those of crystalline Fe ₃ C carbides in all films with additional graphene-like structures at high carbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we find that the amorphous carbidic phase has a composition of 15–25 at% carbon that slightly increases with total carbon content. X-ray absorption spectra exhibit an increasing number of unoccupied 3d states and a decreasing number of C 2p states as a function of carbon content. These changes signify a systematic redistribution in orbital occupation due to charge-transfer effects at the domain-size-dependent carbide/matrix interfaces. The four-point probe resistivity of the Fe _{1− x} C _x films increases exponentially with carbon content from ∼200 μ Ω cm ( x = 0.21) to ∼1200 μ Ω cm ( x = 0.72), and is found to depend on the total carbon content rather than the composition of the carbide. Our findings open new possibilities for modifying the resistivity of amorphous thin film coatings based on transition metal carbides through the control of amorphous domain structures.

The crystal structure and chemical bonding of magnetron-sputtering deposited nickel carbide Ni₁-xCx (0.05 ⩽ x⩽0.62) thin films have been investigated by high-resolution x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and soft x-ray absorption spectroscopy. By using x-ray as well as electron diffraction, we found carbon-containing hcp-Ni (hcp-NiCy phase), instead of the expected rhombohedral-Ni₃C. At low carbon content (4.9 at%), the thin film consists of hcp-NiCy nanocrystallites mixed with a smaller amount of fcc-NiCx. The average grain size is about 10-20 nm. With the increase of carbon content to 16.3 at%, the film contains single-phase hcp-NiCy nanocrystallites with expanded lattice parameters. With a further increase of carbon content to 38 at%, and 62 at%, the films transform to x-ray amorphous materials with hcp-NiCy and fcc-NiCx nanodomain structures in an amorphous carbon-rich matrix. Raman spectra of carbon indicate dominant sp(2) hybridization, consistent with photoelectron spectra that show a decreasing amount of C-Ni phase with increasing carbon content. The Ni 3d-C 2p hybridization in the hexagonal structure gives rise to the salient double-peak structure in Ni 2p soft x-ray absorption spectra at 16.3 at% that changes with carbon content. We also show that the resistivity is not only governed by the amount of carbon, but increases by more than a factor of two when the samples transform from crystalline to amorphous.