Structural, optical, and electronic properties of magnetron-sputtered platinum oxide films

Abstract

Stable platinum oxide films have been prepared through magnetron sputtering and have been analyzed on the bases of energy-sensitive microanalyses, x-ray diffraction, resistivity, and optical reflectance measurements. The complex dielectric function has been determined for various oxygen contents in the film covering the wave-number regime 50 cm−1–λ−1–50 000 cm−1. The vibrational properties are dominated through a strong band, centered at 765 cm−1, associated with a asymmetric stretching mode of the Pt—O bond. The films are amorphous, with chemical composition PtOx, where 1<x<2.1, and are considered as a homogeneous solid solution of PtO and PtO2. The materials system displays a conductor–insulator transition at x≥2, in connection with an optical band gap Eg of ∼1.2 eV in the fully oxidized state. The conduction mechanism over the whole range of compositions is thermally activated and is determined through a large density of localized states extending into the band gap. At x<2 the optical gap disappears, consistent with the semimetallic behavior of the materials system for this range of composition.

Thermal Stability of $$\beta $$ β -PtO $$_2$$ 2 Investigated by Simultaneous Thermal Analysis and Its Influence on Platinum Resistance Thermometry

“…A decomposition sequence PtO 2 → PtO → Pt as it is proposed in [4,5] seems unlikely for our case as the mass loss at T D of 11 % to 12 % is significantly bigger than this decomposition sequence implies, i.e., M = 7.5 % for PtO 2 → PtO. Because the overall mass loss is consistent with the expectations, a non-stoichiometric composition such as for some amorphous films, where a composition PtO 1.6 can be found, is also unlikely [9]. However, it cannot be completely excluded as this stoichiometry is consistent with the mass loss at T D , when the mass loss happening before is attributed to other effects, e.g., degassing or decomposition of adsorbed components sticking on the particles.…”

“…However, first-principle thermodynamics calculations based on density functional theory suggest that metallic Pt 3 O 4 is formed at high oxygen coverages, replacing the semi-conducting PtO on Pt(100) and being stable up to around 900 K at atmospheric pressure [6]. The metallic character of Pt 3 O 4 and the semi-conducting behavior of PtO have been confirmed experimentally for amorphous thin films [7][8][9].…”

Toward tailored functionality of titania nanotube arrays: Interpretation of the magnetic-structural correlations

“…(3), a large v pp is associated with a large density of states at the Fermi level, which consequently can result in higher photocurrent values and potentially lead to stronger catalytic activity. 27,28 As summarized in Table I, the observed trend of v pp for NTs and anatase reference is v pp ðanataseÞ > v pp ðamorphousÞ > v pp ðH 2 À ann:Þ % v pp ðO 2 À ann:Þ >> v pp ðAr À ann:Þ. This indicates a reduction of the density of states at the Fermi level N(E f ) after annealing the NTs, Table I, regardless of the annealing atmosphere.…”

Changes in Preferred Orientation of Pt Thin Films Deposited by dc Magnetron Sputtering Using Ar/O2 Gas Mixtures

“…The resistivity of Pt films increased with the oxygen content in the films, 17,18 as shown in Fig. Thus, resistivity measurements were made from the Pt films deposited at various oxygen fractions in the sputtering gas.…”