ELECTRICAL PROPERTIES OF MO-W-C NANOCOMPOSITE FILMS
Transition metal carbides due to their excellent electrical, mechanical, and thermal properties, and the possibility of manipulating them through changes in the chemical composition, are of great interest nowadays [1,2].
This paper presents the results of a study of the alternating electrical properties of
Mo-W-C composition layers. The layers were prepared using a two-source magnetron sputtering method. Structural studies showed that the obtained layers are nanocomposites consisting of metal carbide nanoparticles incorporated into an amorphous carbon matrix with
a thickness of approximately 950 nm. The alternating-current electrical properties of the films were measured in the temperature range from 20 K to 375 K in the frequency range from 50 Hz to 2 MHz.
Two nanocomposite layers S1 and S4 were selected for conductivity and dielectric permeability studies. Layer S1 contained 100% of (Mo2+W2)C nanoparticles, while layer
S4 contained 28 % of (Mo2+W2)C and 72 % of a MoWC nanoparticles. Nano-grained structure of the layers supports the occurrence of hopping conductivity [3]. To analyse the results obtained, a model of DC and AC step conductivity based on the quantum mechanical phenomenon of electron tunneling between nanometer-sized potential wells was used [4].
The temperature-frequency characteristics of the conductivity and the frequency factor α(f) were determined for both layers. For both samples, there were two mechanisms observed to influence the conductivity and α(f) factor values, high-frequency and low-frequency. From the maxima on the α(f) factor characteristics, the values of relaxation time were calculated, and in terms of the occurrence of the low-frequency stage, the temperature dependence of the relaxation time was determined, and from this, the activation energy of the relaxation time was determined to be ΔE1≈0.316 eV for layer S1 and ΔE4≈0.333 eV for layer S4. Based on the dielectric permeability of the layers, the potential energy of the dipoles was determined to be (0.07±0.004) eV. On this basis, the average distance between carbide nanoparticles (distance over which electrons tunnel) was calculated, which was (3.4±0.2) nm.
nanocomposite coatings, transition metal carbides, tunneling, conductivity, permitivity
Participation in the 2023 IEEE 13th International Conference Nanomaterials: Application & Properties was funded by a grant Szkola Doktorska-Grant -Piotr Gałaszkiewicz
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