Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films

Abstract

Tungsten oxide (WO x ) films were fabricated by (i) reactive thermal evaporation (RTE) at room temperature with oxygen ambient pressure P O 2 as a parameter, and (ii) reactive magnetron sputtering (RMS) with substrate temperature T s as a parameter. The film structure revealed by x-ray photoelectron spectroscopy, x-ray diffraction, density measurements, infrared absorption, and atomic force microscopy was correlated with the nanoindentation hardness H. The RTE WO x films deposited at high P O 2 were amorphous and porous, while H depended appreciably on normalized penetration depth h D (indentation depth/film thickness) due to the closing of the pores at the point of indentation. Decrease in P O 2 from 10 to 2 × 10 −3 mtorr led to smaller porosity, weaker h D dependence of H, and higher average H (measured at h D ≈ 0.2 to 0.3, for example). The RMS WO x film deposited at room temperature was amorphous and denser than all RTE films. The rise in substrate temperature T s first densified the film structure (up to 110°C) and then induced crystallization with larger grain size for T s ജ 300°C. Correspondingly, the h D dependence of H became weaker. In particular, H of the RMS sample deposited at 110°C showed a peak at h D slightly above 1 owing to pileup at the contact point of indentation. For higher T s , pileup occurred at shallower h D and the average H (measured at h D ≈ 0.2 to 0.3, for example) rose, accompanied by the increase of grain size.

Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

“…With increase in the deposition time, mechanical properties gradually decrease mainly due to the development of film porosity ( Supplementary Fig. 4D–H ) 56 . Surface roughening is required to increase its hydrophobicity; however, many of the superhydrophobic coatings fail mechanically at this stage 57 .…”

Interfacial Engineering of Hierarchically Porous NiTi/Hydrogels Nanocomposites with Exceptional Antibiofouling Surfaces

“…After electrochemically dealloyed for 1 h, NiTi exhibited certain decrease in both surface elastic modulus and hardness, where E and H were 89.4 ± 17.9 and 4.5 ± 0.7 GPa, respectively. As dealloying time increased, mechanical properties gradually decreased mainly due to the development of surface porosity . Meanwhile, when dealloying time increased to 3 h, E and H decreased to 82.1 ± 12.1 and 3.9 ± 1.1 GPa, respectively.…”

Effects of oxygen contents on the electrochromic properties of tungsten oxide films prepared by reactive magnetron sputtering

“…The M x WO 3−y films have intense blue, red, or golden color which depends on the x value and process of ion insertion and electron injection. Lee et al [5] reported that a-WO 3 Various techniques are available for the preparation of tungsten oxide thin films for electrochromic application [6][7][8][9][10][11][12]. However, the effects of oxygen contents to the electrochromic properties of tungsten oxide films need more discussions.…”