Surface Morphology and Optical Properties of Hafnium Oxide Thin Films Produced by Magnetron Sputtering

Abstract

Hafnium oxide films were deposited on sapphire and silicon (100) substrates using the DC reactive magnetron sputtering technique from a pure hafnium target at different discharge power levels. The influence of the cathode power on the chemical composition, morphology, crystallographic structure and optical properties of the films was investigated. X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and Fourier-transform infrared spectroscopy (FTIR) were employed to determine the chemical composition and bonding structure. In all cases, the films were found to be amorphous or nanocrystalline with increased crystalline content as the sputtering power was increased, according to XRD and FTIR. In addition, EDX showed that the films were oxygen-rich. The effect of power deposition on the surface topography and morphology of the films was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images revealed the emergence of mound morphologies as the cathode power was increased. These features are related to blistering effects probably due to the presence of stress and its promotion within the film thickness. Finally, the optical properties showed an average transmission of 80% in the visible range, and the refractive index determined by spectral ellipsometry (SE) was found to be in the range of 1.85–1.92, close to the reported bulk value. SE was also used to study the film porosity observed by SEM, which can be related to the oxygen-rich character of the films.

Polypyrrole–Tungsten Oxide Nanocomposite Fabrication through Laser-Based Techniques for an Ammonia Sensor: Achieving Room Temperature Operation

“…The WO 3 layer obtained by PLD (red pattern in Figure 2 a) shows similar characteristics to the original WO 3 (PLD Target). No diffraction peaks are visible in the PPy powder spectra, and the narrow peak observed at 2theta = 33.100° is a reflection of the silicon substrate [ 30 ]. The addition of PPy on top of WO 3 (WO 3 /PPy, Figure 2 a) by MAPLE makes the (002), (020), and (200) individual lattice planes not easily distinguishable, but the main aspect of the diffraction pattern is maintained.…”

Ar transport and blister growth kinetics in titania-doped germania-based optical coatings

“…We see that the shape over about 70% of their radius is very well fitted by a circle, but the edges of the blisters do not break up abruptly as a truncated sphere would do. They rather have a smooth edge, much better represented by equation (7), which takes into account the mechanical properties of the film near the edge. Yet, this equation does not consider the peeling force involved during the growth of a blister.…”

“…However there are much fewer reports on blistering occurring as a result of gas being incorporated in the material during deposition by techniques such as ion beam sputtering (IBS), magnetron sputtering (MS) or atomic layer deposition. Examples of blistering during annealing of single layers deposited by such technique are described in [7][8][9]. One recent and detailed study is that of Hatton et al [10] on Ar and Xe clustering in cadmium telluride deposited by pulsed MS, where blisters appear during an activation annealing at 400 • C. In such a case, the question arises whether blistering is initiated by stress-induced cracking, or gas accumulation, or a synergistic combination of both.…”