Nitrogen incorporation and composition facilitated tailoring of the optical constants and dispersion energy parameters of tungsten oxynitride films

Abstract

a b s t r a c tOptical properties, including the index of refraction, extinction coefficient and band gap of 100 nm thick tungsten oxynitride (W-O-N) films are reported. In addition, the Wemple and DiDomenico (WDD) model was used to calculate the dispersion energies and oscillator energies of the films, establishing a correlation among the films' optical, chemical, and physical properties, as a function of nitrogen content. Nitrogen concentration in the W-O-N films was varied by adjusting the nitrogen gas flow rate from 0 to 20 sccm while keeping total gas flow (nitrogen þ oxygen þ argon) constant at 40 sccm. Both the index of refraction (n) and extinction coefficient (k) of W-O-N films demonstrated a high degree of sensitivity to the nitrogen content during deposition. The optical constants of films fabricated without any nitrogen correspond to transparent W-oxide (WO 3 ) where n 550 ¼ 2.1 and k 550 ¼ 0.0. The magnitude of the spectral response for both n and k tends to increase with increasing nitrogen content. Systematic increases of the films' nitrogen content lead to the formation of W-oxide (E g z 3 eV) / W-O-N oxynitride semiconductor (E g z 2 eV) / N-rich W-O-N semi-metal (E g < 2 eV) / WN 2 type metallic transition was evident in dispersion profiles of n and k for W-O-N films with increasing nitrogen content. The corresponding mechanical characteristics, namely hardness (H) and Young's modulus (E), attain a maximum of 4.46 GPa and 98.5 GPa, respectively, at a nitrogen flow rate of 5 sccm, at which point H and E values decrease to attain 3.57 GPa and 72.91 GPa, respectively. The trend observed in H and E values correlate with the W-O and W-N bonds formation in W-O-N along with the interruption of local epitaxy attributed to increasing nitrogen content within the growth chamber. A correlation among the nitrogen content, optical constants and physical properties, along with the associated dispersion model, is presented to account for the optical properties of sputter-deposited W-O-N films. The results demonstrate that tailoring the properties of W-O-N films for desired applications can be achieved by tuning the nitrogen content and chemical composition.

Znga2o4 and Znga2o4:N Thin Films Applied as Sensors for Detection of Acetaldehyde in Ethanol

“…suggest the formation of an oxynitride poorly crystalline phase by two small peaks at 2θ = 34.5° and 36.8°, which could be related to (006) and (103) crystallographic planes by analogy with GaOxNy (ICDD 32-0398), respectively. The nitrided samples exhibited porous and rough aspect, as expected [31,32,38], with quite good substrate coverage even at the Pt/Al2O3/ interface. After nitridation, it can be clearly observed on the FE-SEM images the small grains of the films on the large grains of alumina (Figure 3B and 3C).…”

Effect of post-deposition annealing on the optical and mechanical properties of amorphous tungsten oxynitride thin films

“…Whileeffortsexist in the literature to characterize the micro-structure, chemical composition, electrochromic, optical properties and mechanical behavior of W-O-N thin films [24][25][26][27][28][29][30][31][32][33], studies focused towards fundamental understanding of the effect of post-deposition thermal treatment arescarce [34][35][36][37][38].Furthermore, while results that have been published for W-O-N films regarding thermal treatment are not comprehensive,such a deeper understanding of the effect of thermal treatment and conclusive results can provide insightsinto the expected behavior of transition metal nitrides and oxynitrides in general. Experiments involving Zn-O-Nand Ta-O-N have revealed that the annealing process hassome effect on the optical properties of metal oxynitrides, depending on the temperature and processing atmosphere employed [39][40].…”