Naslov
Nanocrystalline nickel prepared by magnetron sputtering - structure and thermal stability

Autori
Radić, Nikola ; Ivkov, Jovica ; Djerdj, Igor ; Tonejc, Anton ; Tonejc, Andjelka ; Dubček, Pavo

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
ICTF13/ACSIN8 Abstract Book / Karlsson, Ulf - Stockholm : Swedish vacuum Society, 2005, 54-54

Skup
13th INternational Congress on Thin Films/ 8th International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures

Mjesto i datum
Stockholm, Švedska, 19.06.2005. - 23.06.2005

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Nanocrystalline nickel; magnetron sputtering

Sažetak
Nanocrystalline nickel (nc-Ni) is very interesting material due to its greatly enhanced mechanical properties and reduced localized corrosion. However, it exhibits a metastable structure, and transforms into a more stable large-grain nickel upon heating/ at temperatures 200-300 °C. Pulsed electrodeposition is by far a prevailing/ dominant technique of "bulk" nc-Ni preparation. Here we present results on structure and thermal stability of the nc-Ni thin films prepared by magnetron sputtering technique. Nickel thin films were prepared by a dc magnetron sputtering onto various substrates (glass, fused silica, alumina, sapphire, mono-Si) of 1 cm dia, which rotated during deposition in order to avoid build-up of preferential stress axis in the film. Base pressure in the process chamber was 10-6 - 10-5 Pa, and working gas was argon in continuous flow. Total surface averaged power density was about 6W/cm2, and the deposition rate was about 7-8 nm/min. Film thickness was in most cases about 400 nm, although some films with about 100 nm and 20 nm were prepared, as well. In order to examine the effects upon film structure, argon pressure was varied in the 0, 35-1, 33 Pa range, while substrate temperature was varied in the room temperature - 700 °C range. Structure of the as-deposited films and thermally treated films was examined by the XRD method, TEM/HREM , while their surface features were examined by the AFM. It was found (by the Rietveld analysis of the XRD patterns) that the Ni-films prepared ar room temperature exhibit nanocrystalline structure. The grains are predominantly 111-oriented, and the average grain-size ranges from 11.7 nm (at ?? Pa argon pressure) to 15.7 nm (at ?? Pa argon pressure). However, the average grain-size of nickel films deposited onto substrates at 150 °C or higher temperature is about 90 nm. Thermal stability of the prepared nc-Ni films was examined by isochronal annealing in vacuum (better than 10-4 Pa) up to 700 °C, while continuously monitoring the electric resistance of the film. The initial el. resistance of the as-deposited nc-Ni films is generally several times higher that after the annealing cycle is completed. A variation of the el. resistance with temperature upon first heating indicates a phase transformation at about 170-200 °C range - roughly corresponding to the temperature of abnormal grain growth in electrodeposited nc-Ni. However, a more dramatic transformation occurs above about 600°C, with a steep drop of the el. resistance to the bulk Ni value. During subsequent cooling (or further temperature up-down cycles) electric resistance of the films follows a temp. dependance characteristic for bulk coarse-grain nickel. The XRD analysis revealed that the grain-size of the annealed Ni-films is in the 75-105 nm range.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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