Zirconium nitride films deposited in (Ar + N2 + H2) sputtering atmosphere: Optical, structural, and electrical properties

Abstract

Zr–N films were grown on glass substrates via radio-frequency magnetron sputtering using an Ar + N2 + H2 mixture. Hydrogen was employed in order to reduce oxygen contamination coming from background pressure, as confirmed by secondary ion mass spectroscopy analysis. The tuned process parameter was the nitrogen flux percentage (RN2) in the mixture. The crystallographic structure of the films was studied using x-ray diffraction. The measurements show that the films deposited at low RN2 (lower than or equal to 50%) crystallize in the rocksalt ZrN structure. As RN2 exceeds 50%, the film exhibits the co-presence of ZrN and Zr3N4 (denoted as o-Zr3N4) phases. When the deposition is performed in only nitrogen atmosphere (RN2 = 100%), a broad peak located at 2θ ≈ 32.2° is mainly attributed to the contribution coming from (320) planes of the o-Zr3N4. An envelope method, based on the optical reflection and transmission spectra taken at normal incidence, has been applied for the optical characterization of the nitride films. Such a method allows the determination of the samples’ average thickness and optical constants (refractive index n and extinction coefficient k) in the ultraviolet-visible-near infrared regions. The evaluated thickness was about 2500 nm, which is in good agreement with the value obtained from profilometry. The absorption coefficient α was calculated from reflectance and transmittance spectra. The energy bandgap ranges from 2.3 eV to 2.4 eV. Electrical characterization was performed using capacitance-voltage measurements, which showed that the films evolve from insulating to semiconductor behavior when the nitrogen content in the sputtering atmosphere is decreased, confirming structural and optical results.

Optical, electrical, and structural properties of ZrON/Ag/ZrON multilayer transparent conductor for organic photovoltaics application

“…Despite the absence of an oxygen source during sputtering, the dielectric films grown were identified to be a mixture of ZrN-ZrO compound (referred to herein as ZrON). This is due to the fact that transition metals have a high affinity with oxygen [15]. In other words, during deposition, Zr metal actively reacts with oxygen-containing molecules (e.g., water vapor) within a chamber and consequently ZrN-O compound is unintentionally formed, as confirmed by the XPS result.…”

Role of oxygen contaminant on the physical properties of sputtered AlN thin films

“…The lowering of the band gap, observed as optical absorption below the fundamental edge, is induced by an exponential distribution of the density of localized states in the tails of the allowed bands. These localized states can be introduced inside the band gap by disorder and defects (such as nitrogen vacancies and oxygen impurities) in the crystalline structure [25]. An estimation of the extent of these states can be derived from the Urbach tail [32], which is obtained from the slope of the linear approximation of ln(a) versus the photon energy.…”

Effects of Nitrogen Flow Ratio on Structures, Bonding Characteristics, and Mechanical Properties of ZrNx Films

“…By contrast, N-rich compounds such as Ti 3 N 4 , Zr 3 N 4 , and Hf 3 N 4 have been reported [15]. Zr 3 N 4 crystallizes in an orthorhombic (o-Zr 3 N 4 ) [16][17][18] or cubic (c-Zr 3 N 4 ) [19][20][21][22][23] phase. o-Zr 3 N 4 was reported as a transparent insulator [16,24], whereas c-Zr 3 N 4 with a cubic Th 3 P 4 -type structure was suggested as an alternating hard material [19,23].…”