RhO2 belongs to the family of conducting platinum group metal oxides, which have attracted attention as new capacitor electrode materials for dynamic random access memories (DRAMs) and nonvolatile ferroelectric random access memories (FeRAMs). Rh, Rh2O3, and RhO2 thin films were prepared by sputtering and their XPS spectra were collected with a monochromatic Al Kα x-ray source. This report includes XPS spectra of Rh 3d and O 1s core regions for these films.

In this study, we have examined the preparation of thin films of Ni oxyhydroxide, which are used for batteries, supercapacitors, and electrochromic devices, by reactive sputtering. Transmittance and resistivity were found to decrease with the incorporation of H 2 O into the sputtering gas. This indicates that the valence state of Ni atoms in the film changes from Ni 2þ to Ni 3þ . Peaks due to Ni-OH and hydrogen bonded OH were observed by Fourier transform IR (FTIR) spectroscopy of the films sputtered in O 2 þ H 2 O mixed gas. From the obtained results, it is confirmed that Ni oxyhydroxide films are formed by reactive sputtering in O 2 þ H 2 O mixed gas. An electrochromic coloration efficiency of 29 cm 2 /C was obtained in 1 M KOH aqueous electrolyte solution for the Ni oxyhydroxide films.

Thin films of RhO 2 , which belongs to the family of conducting platinum group metal oxides, were prepared by reactive sputtering. Influences of sputtering parameters, such as rf power and substrate temperature, and postdeposition annealing on crystallinity, chemical bonding state and resistivity of the deposited films were studied, in order to obtain low-resistivity RhO 2 thin films. The resistivity of the deposited films decreased with decreasing rf power. Plasma emission measurement suggested that oxidation of Rh proceeded under the low rf power condition. Poorly-crystallized conducting RhO 2 thin films with resistivity of 300-500 µ cm were prepared at substrate temperatures below 150 • C; the resistivity of the films increased with increasing substrate temperature above 150 • C due to the formation of semiconducting Rh 2 O 3 . After postdeposition annealing in oxygen atmosphere at up to 700 • C, well-crystallized RhO 2 films were formed, and the minimum resistivity of 80 µ cm was obtained.

We have expected that the epitaxial growth of (111)Rh and (001)Rh films with a thickness of 100 nm can be controlled on (11 2 0) sapphire by changing sputtering parameters using an ultrahigh-vacuum sputtering system, because the lattice mismatches between the two-dimensional superlattice cells of (111)Rh/(11 2 0) sapphire and (001)Rh/(11 2 0) sapphire systems are the same. Thus, the effect of rf sputtering power (Prf) on each epitaxial growth was examined, and the crystal quality, surface morphology, resistivity and temperature coefficient of resistivity (TCR) of the prepared Rh films were evaluated. As a result, it is revealed that both the (111)Rh and (001)Rh films can be grown epitaxially on (11 2 0) sapphire by adjusting only the values of Prf (deposition rate: Rd) under the condition of the substrate temperature (Ts) of 500 °C. In addition, it is confirmed that the average surface roughness of these epitaxially grown Rh films is below approximately 1.2 nm, and resistivity of approximately 5.6 ×10-6 Ω cm is obtained.

Conducting Rh oxide thin films were prepared by sputtering a Rh target in an Ar and O2 mixed gas. Effects of the oxygen gas flow ratio on the crystallinity, chemical bonding state and resistivity were studied. Amorphous Rh2O3 films were prepared at an O2 flow ratio of 20%. The Rh2O3 films had a relatively high resistivity of 2 mΩcm and a negative temperature coefficient of resistance (TCR) of -1000 ppm/°C, which indicated semiconducting characteristics. On the other hand, amorphous RhOx films with a composition of 1.5 ≤x ≤1.7 were prepared at O2 flow ratios above 40%. Resistivity of these RhOx films were 800 µΩcm and had almost no temperature dependence. Metallic conduction characteristics of RhO2 were assumed to be revealed by the decrease in the oxygen deficiency.