Influence of the chemical and electronic structure on the electrical behavior of zirconium oxynitride films

Abstract

This work is devoted to the investigation of decorative zirconium oxynitride, ZrOxNy, films prepared by dc reactive magnetron sputtering, using a 17:3 nitrogen-to-oxygen-ratio gas mixture. The color of the films changed from metallic-like, very bright yellow pale, and golden yellow, for low gas mixture flows [from 0 to about 9SCCM (SCCM denotes cubic centimeter per minute at STP)] to red brownish for intermediate gas flows (values up to 12SCCM). Associated to this color change there is a significant decrease of brightness. With further increase of the reactive gas flow, the color of the samples changed from red brownish to dark blue (samples prepared with 13 and 14SCCM). The films deposited with gas flows above 14SCCM showed only apparent colorations due to interference effects. This change in optical behavior from opaque to transparent (characteristic of a transition from metallic to insulating-type materials), promoted by the change in gas flow values, revealed that significant changes were occurring in the film structure and electronic properties, thus opening new potential applications for the films, beyond those of purely decorative ones. Taking this into account, the electrical behavior of the films was investigated as a function of the reactive gas flow and correlated with the observed chemical, electronic, and structural features. The variations in composition disclosed the existence of four different zones, which were correlated to different crystalline structures. For the so-called zone I, x-ray diffraction revealed the development of films with a B1 NaCl face-centered cubic zirconium nitride-type phase, with some texture changes. Increasing the reactive gas flow, the structure of the films is that of a poorly crystallized overstoichiometric nitride phase, which may be similar to that of Zr3N4, but with some probable oxygen inclusions within nitrogen positions. This region was characterized as zone II. Zone III was indexed as an oxynitride-type phase, similar to that of γ-Zr2ON2 with some oxygen atoms occupying some of the nitrogen positions. Finally, occurring at the highest flow rates, zone IV was assigned to a ZrO2 monoclinic-type structure. The composition∕structure variations were consistent with the chemical bonding analysis carried out by x-ray photoelectron spectroscopy, which showed oxygen doping in both Zr3N4- and ZrN-type grown films. The electronic properties of the films exhibited significant changes from zone to zone. Resistivity measurements revealed a very wide range of values, varying from relatively highly conductive materials (for zone I) with resistivity values around few hundreds of μΩcm to highly insulating films within zones III and IV, which presented resistivity values in the order of 1015μΩcm. Regarding zone II, corresponding to oxygen doped Zr3N4-type compounds, the observed behavior revealed resistivity values increasing steeply from about 103 up to 1015μΩcm, indicating a systematic transition from metallic to insulating regimes.

Structural, optical and hydrophobic properties of sputter deposited zirconium oxynitride films

“…Fig. 1 shows the XRD pattern of the nanocrystalline thin films of zirconium oxynitride (A, B, C, D and E) deposited in N 2 + Ar mixture with varying oxygen partial pressure at 500 • C. At 2.5% oxygen partial pressure, the (2 2 2) and (4 4 0) peaks of metastable ␥-Zr 2 ON 2 which are also observed by Carvalho et al [8] , along with (1 1 1) peak of m-ZrO 2 are observed. The evolution of (4 0 0), (4 3 1), and (3 1 1) peaks of ␥-Zr 2 ON 2 occurs from 4.0% oxygen partial pressure.…”

Analysis of multifunctional oxycarbide and oxynitride thin films by modulated IR radiometry

“…On the other hand, the inverse calibrated phases, measured for the two coatings ZrON1 (o) and ZrON2 (∆) at higher modulation, deviate from the two-layer model to lower values. This behaviour, which is characteristic for a three-layer structure with a thin surface on top of the coating of reduced thermal effusivity, e s < e c , can be explained for the two coatings ZrON1 and ZrON2 by very thin oxide contamination layers just at the surface [4].…”

“…4, the coatings ZrON1 and ZrON2 are metal-like coatings with a cubic-type structure, whereas the coatings ZrON3 and ZrON4 have a different crystalline structure characterized by a mixture of two electrically insulating structures: An orthorhombic nitride structure and a cubic oxynitride structure [3]. These differences of composition and structure, which affect all film properties [3,4], are found in the range of intermediate and higher modulation frequencies of the inverse calibrated modulated IR phases ( 1/2 > 150, the inverse calibrated phases measured for the two coatings ZrON3 ( ) and ZrON4 (+) considerably exceed the zero-line (Φ n = 0 deg), showing a behavior which is characteristic for semi-transparent coatings, as observed in fact for these two films in optical measurements carried out by UV-Vis spectrophotometry [3,4]. On the other hand, the inverse calibrated phases, measured for the two coatings ZrON1 (o) and ZrON2 (∆) at higher modulation, deviate from the two-layer model to lower values.…”

“…The atomic composition of the as-deposited coatings was measured by Rutherford Backscattering Spectroscopy (RBS) using a 2 MeV He + beam as well as 1.4 and 2 MeV proton beams, to increase the accuracy in the oxygen signals [3,4]. The structure and the phase distribution of the coatings were analyzed by X-ray diffraction (XRD), using a Philips PW 1710 diffractometer (Cu-K radiation) operating in a Bragg-Brentano configuration.…”

Colored semi-transparent Cu-Si oxide thin films prepared by magnetron sputtering

“…In many cases, these thin films also present a good electrical conductivity. Within this type of materials we can quote the nitrides, oxinitrides, carbides and nitrocarbides of the elements of the first transition series [8]. In comparison with the huge number of works on this topic available in the literature, there are very few reports on the preparation of colored oxide thin films which show some absorption in the visible region of the electromagnetic spectra.…”