Oxynitride Films Research Articles

Role of annealing temperature on structural and optical properties of zinc oxy-nitride films synthesized by powder vapor transport technique

Zinc oxy-nitride (ZnON) is an emerging semiconductor having tunable energy bandgap (Eg) and refractive index (n). Herein, the effect of annealing temperature on ZnON films synthesized on glass substrates at different (50, 100 and 150 sccm) nitrogen gas flow rates (NGFR) by simple powder vapor transport (PVT) technique is studied. All the synthesized ZnON films are annealed at 300 °C for 60 min. The unannealed and annealed ZnON (Un-&-An-ZnON) films are characterized by XRD, SEM, Raman and UV spectroscopies. XRD analysis confirms the formation of polycrystalline ZnN films and no diffraction plane related to oxide phase. The crystallinity of Un-ZnN films is increased after annealing, however, it is maximum for 100 sccm NGFR. Raman analysis indicates the presence of vibrational modes related to ZnN and ZnO phases, thereby confirming the formation of ZnON films. After annealing, the surface morphologies of Un-ZnON films is transformed from nano-sheets/nano-blocks to rounded nanoparticles. The change in structural and morphological features of ZnON films, associated with annealing temperature causes to create stresses and defects and hence Eg and n. The values of n (1.85–1.87) and Eg (2.6–2.7 eV) of Un-ZnON films are increased to (1.98–2.62) and (3.16–3.25 eV), after annealing, respectively. These inexpensive but high quality ZnON films can be used for semiconducting and optoelectronic devices.

Innovative all-silicon based a-SiNx:O/c-Si heterostructure solar-blind photodetector with both high responsivity and fast response speed

The photoresponsivity and response speed are two key figures of merit for the photodetector (PD). According to the previous reports, there is an inherent contradiction between high photoresponsivity and fast response speed in normal photoconductive-type PDs. Facing the challenge of coordinating this inherent contradiction, we propose an innovative design idea, which employs a luminescent wide-bandgap (WBG) amorphous oxynitride (a-SiNx:O) film as an absorption layer combining with monocrystalline silicon (c-Si) as a carrier transport layer, to construct an all-silicon based a-SiNx:O/c-Si heterostructure photoconductive-type solar-blind photodetector (SBPD). Benefiting from the built-in electric field in the a-SiNx:O/c-Si heterojunction and good passivation at the SiNx:O/Si interface, the photogenerated carriers in the a-SiNx:O layer can be injected into the c-Si layer, which separates the carrier transport process from the carrier photogeneration/recombination process in the different layers. Since the transport process of injected carriers in the c-Si layer is much faster than their recombination process, the detector yields a large photoconductive gain, thus overcoming the above-mentioned inherent contradiction in normal photoconductive-type PDs, where both the defect-related carrier photogeneration/recombination process and carrier transport process occur in the same active layer. The designed SBPDs exhibit highlighted performance with both the high responsivity (R) of 4 × 103 A/W at 225 nm and the fast response speed of 4.3 µs. Compared to most other WBG semiconductor SBPDs, e.g., AlxGa1−xN, MgxZn1−xO, Ga2O3, and diamond, the advantages of the a-SiNx:O/c-Si heterostructure SBPD lie not only in adopting economic Si-based materials but also in manufacturing processes compatible with mature CMOS technology, thereby rendering it preferable for the development of cost-effective large-area SBPD arrays.

Characterization and electrical response of reactively sputtered thin film deposited at oxygen and nitrous oxide environment

Niobium oxynitride (NbON) thin films were deposited on silicon substrate using DC reactive magnetron sputtering technique of niobium metal targets at different nitrous oxide (N2O) and oxygen flow in the plasma during deposition. To get NbON thin films, the deposition parameters were also optimized. X-ray reflectivity (XRR) technique was used to estimate the film thickness of the as deposited films. The films' surface morphology and chemical compositions were investigated by field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) techniques. SEM images indicate the smooth surface morphology of the deposited films. XPS study exposes the noticeable presence of N2 in the niobium oxynitride films deposited with only 20 sccm nitrous oxide flows in the plasma. The leakage current-voltage (I-V) measurement reveals the reduction in leakage current with higher N2O and lowers oxygen flow rates. The resistivity of the thin films was measured. The thin films deposited with higher N2O flow give high resistivity because of lesser availability of defect states. It may be stated that nitrous oxide content reduces the leakage current thus, improves the film and interface properties.

Optical properties investigation of reactively sputtered tantalum oxynitride films

The coalescent behavior of metal oxide and metal nitride in metal oxynitride (MON) is making the material more conspicuous. Along with tunable optical properties, enhances mechanical properties, better chemical stability can be derived for MONs, which are of prime importance in the fields, such as photovoltaic, photo-chromatics, photocatalytic, protective and aesthetic coatings. In this paper, the optical properties of tantalum oxynitride thin film deposited through a reactive magnetron sputtering method were explored. Pure tantalum target was sputtered with argon gas in the presence of an optimized O2/N2 gas ratio. The chemical and physical properties of the film were investigated by X-ray diffraction technique, Scanning Electron Microscopy and AFM. Optical properties were explored with UV–visible spectroscopy and Spectroscopic Ellipsometry (SE). Transmittance and reflectance of the films show that the optical properties of the films have transparency (70–90%) and an absorption edge near 350 nm. For the analysis of SE data, the Tauc-Lorentz optical model with an additional Lorentz oscillator for semiconductor or insulator material were used. Here, the Ellipsometry technique has provided detailed optical nature of the film in terms of refractive index (n) ranging from 1.82 to 2.62, Energy Bandgap (Eg) 3.6 eV along with film thickness (∼200 nm) and surface roughness (∼6 nm).All these optical properties make the material a suitable candidate for antireflective coating, preparation of optical filters, photocatalytic agent, transparent coating for optical devices.

Electrocatalytic Reduction of Nitrogen to Ammonia: the Roles of Lattice O and N in Reduction at Vanadium Oxynitride Surfaces.

Vanadium oxynitride and other earth-abundant oxynitrides are of growing interest for the electrocatalytic reduction of nitrogen to NH3. A major unresolved issue, however, concerns the roles of lattice N and lattice O in this process. Electrochemistry and photoemission data reported here demonstrate that both lattice N and dissolved N2 are reduced to NH3 by cathodic polarization of vanadium oxynitride films at pH 7. These data also show that ammonia production from lattice N occurs in the presence or absence of N2 and involves the formation of V≡N: intermediates or similar unsaturated VN surface states on a thin vanadium oxide overlayer. In contrast, N2 reduction proceeds in the presence or absence of lattice N and without N incorporation into a vanadium oxide lattice. Thus, both lattice N and N2 reduction mechanisms involve oxide-supported V surface sites ([V]O) in preference to N-supported sites ([V]N). This result is supported by density functional theory-based calculations showing that the formation of V≡N:, V-N═N-H, and a few other plausible reaction intermediates is consistently energetically favored at [V]O rather than at [V]N surface sites. Similar effects are predicted for the oxynitrides of other oxophilic metals, such as Ti.

Retraction Note to: Structural and electrochemical impedance spectroscopic studies on reactive magnetron sputtered titanium oxynitride (TiON) thin films

Titanium oxynitride films were deposited onto commercially pure titanium substrates by direct current reactive magnetron sputtering method using Ti targets and an Ar–N2–O2 mixture discharge gas. The X-ray photoelectron spectroscopy survey spectra on the etched surfaces of TiON films exhibited the characteristic Ti 2p, N 1s, and O 1s peaks at the corresponding binding energies 454.5, 397.0, and 530.7 eV, respectively. The surface topography of these coatings was studied using atomic force microscopy. The characteristic Raman peaks at 200 and 641 cm−1 for the TiN bonds and at 148, 398 ,and 518 cm−1 for the TiO2 bonds were observed from the Laser Raman spectrometer. The potentiodynamic polarization studies in simulated bodily fluid were performed and the results are reported in this article.

Novel corrosive behavior of titanium oxynitride film deposited on nickel–titanium alloy using cathodic cage plasma processing technique

AbstractIn this study, we used a cathodic cage plasma system to deposit an oxynitride coating on a nickel–titanium metallic substrate for three different processing gas compositions (60%H2 + 40%N2; NT1, 50%H2 + 50%N2; NT2%, and 40%H2 + 60%N2; NT3). The influence of various gas mixtures on surface morphology, chemical composition, and crystal structure of treated samples (NT1, NT2, and NT3) was investigated. A spectrophotometer is used to determine the amount of nickel ion leaching in a chloride‐containing saline electrolyte using atomic absorption spectroscopy. Potentiodynamic polarization curves and electrochemical impedance spectroscopy depict the enhanced corrosion resistance of treated samples as compared to the base Ni–Ti sample. Titanium oxynitride coating in NT3 samples shows an excellent barrier against corrosion behavior and nickel ion leakage in a corrosive environment.

Application of SiOxNy films in industrial bifacial PERC solar cells

The bifacial p-type silicon (p-Si) passivated emitter and rear cells (PERCs) have dominated the industrial bifacial solar cells. In this paper, we have investigated the impact of hydrogenated amorphous silicon oxynitride (SiOxNy) films on the optical and electrical performance of bifacial p-Si PERCs. Simulation and characterization are carried out to show the improvement of bifacial p-Si PERCs, yielding an absolute front-side efficiency improvement of 0.14% and 016% with SiOxNy films introduced to the front-side and rear-side, respectively. When SiOxNy films are employed to both sides of bifacial p-Si PERCs, the front-side and rear-side efficiency separately increase by 0.27% and 0.26% compared to the baseline without SiOxNy films. We have achieved on the bifacial p-Si PERCs production line an averaged front-side efficiency of 23.23% (champion efficiency of 23.42%), together with a 17.31% averaged rear-side efficiency. Furthermore, the introduction of SiOxNy films has been demonstrated to reduce the rear-side potential induced degradation (PID) effect through both single-cell modules and commercial glass-glass modules, due to the SiOxNy films protecting AlOx from corrosion and maximizing the field-effect passivation of AlOx layers.

Optical properties of silicon oxynitride films grown by plasma-enhanced chemical vapor deposition

In this paper, silicon oxynitride films (SiOxNy) grown by plasma-enhanced chemical vapor deposition are investigated. As precursor gases silane (SiH4), nitrous oxide (N2O), nitrogen (N2) and ammonia (NH3) are used with different compositions. We find that for achieving high nitrogen content adding ammonia to the precursor mix is most efficient. Moreover, we investigate the balance between adsorption and desorption processes during film growth by investigating the film growth rate as a function of the substrate temperature. From these data we are able to determine an effective activation energy for the film growth, corresponding to the difference between adsorption and desorption energy. Finally, we have thoroughly investigated the optical properties of the films using spectroscopic ellipsometry. From these measurements, we suggest a parametrized model for the refractive index and extinction coefficient in a wide range of compositions based on a Cauchy- and a Lorentz-fit.

Preparation of Multifunctional Metal Oxynitride 2D Crystals and Oriented Transparent Free-Standing Oxynitride Films

Metal oxynitride two-dimensional (2D) crystals prepared by the delamination of layered compounds have attracted attention as photocatalysts, electrode catalysts, and electrolyte materials. However, the preparation of such materials is a significant challenge because of the difficulty related to producing chemically stable layered oxynitrides. In this study, oxynitride 2D crystals having triple perovskite units (A site: Ca, B site: Ta) were successfully prepared via the perfect delamination of the chemically stable Ruddlesden–Popper phase layered oxynitrides, Na2Ca2Ta3O9N. The layered compound was found to be stable during proton exchange in 6 M HNO3 and a subsequent delamination process, and the resulting oxynitride 2D crystals (herein [Ca2Ta3O9.5N0.5]−1.5) were observed to have a yellow coloration along with a band gap of 2.58 eV. The [Ca2Ta3O9.5N0.5]−1.5 2D crystals modified with RhCrOx and CoOx cocatalysts restacked with alkali ions exhibited photocatalytic activity for H2 and O2 evolution from pure water under UV light and visible light illumination. A transparent, free-standing oxynitride 2D-crystal film having a thickness of around 1 μm was prepared from the 2D-crystal suspension. This film was perfectly oriented in the [001] direction, which resulted in flexibility, mechanical strength, and airtightness due to face-to-face lamination of the 2D crystals. The proton conductivity of the oxynitride 2D-crystal film was around 10–3–10–4 S/cm at 25–50 °C (RH: 90–100%). The cell exhibited a power density of 9 mW/cm2 at 25 mA/cm2. This type of free-standing, flexible oxynitride film is expected to provide a new possibility and to enable the use of oxynitride materials in various applications.

The growth of a multi-principal element (CoCrFeMnNi) oxynitride film by direct current magnetron sputtering using air as reactive gas

CoCrFeMnNi multi-principal element alloy films were grown by direct current magnetron sputtering in a mixture of argon and air. The air fraction was varied from 4 to 50%, which resulted in a change of the phase state of the growing film. A 〈100〉 preferred orientation face centered cubic metal (doped with O and N) structure develops below 12% of air. Between 12 and 30% air, a two phase 〈100〉 preferred orientation face centered cubic metal + oxynitride (B1) structure forms. Above 30% of air a single phase B1 oxynitride structure is observed. Compared to nitrogen, oxygen is preferentially incorporated into the growing structures. The 〈100〉 preferential orientation is the result of selective nucleation (below 30% of air) or competing growth (above 30% of air) of the forming crystals.Detailed microscopic analysis shows a complex structure for both the metal and the oxynitride phase in the films deposited at low and high air fraction. In both cases, the films are characterized by local structures ordered on a few nanometer scale and their formation is explained as a result of spinodal decomposition of the as-formed homogenous structure which occurs during film growth.

Optimization of Fabrication Process for SiON/SiOx Films Applicable as Optical Waveguides

In this paper, the analysis of silicon oxynitride (SiON) films, deposited utilizing the plasma enhanced chemical vapor deposition (PECVD) process, for optical waveguides on silicon wafers is presented. The impact of N2O flow rate on various SiON film properties was investigated. The thickness and refractive index were measured by micro-spot spectroscopic reflectometry and confirmed by spectroscopic ellipsometry. The chemical composition of SiON films was analyzed using Secondary Ion Mass Spectrometry (SIMS). The surface roughness was analyzed using Atomic Force Microscopy (AFM). Increasing the N2O flow rate during deposition caused the deposition rate to increase and the refractive index to decrease. By changing the flow rate of gases into the chamber during the PECVD process, it is possible to precisely adjust the oxygen (O2) ratio and nitrogen (N2) ratio in the SiON film and thus control its optical properties. This was possibility utilized to fabricate SiON films suitable to serve as a waveguide core for optical waveguides with a low refractive index contrast.

Composition, dielectric breakdown, and bandgap of ultra-thin amorphous boron oxynitride produced by magnetron sputtering

Ultra-thin amorphous boron oxynitride films were deposited at room temperature on silicon and polymer substrates using radio frequency magnetron sputtering of a hexagonal boron nitride target in varied argon-nitrogen background gas ratios. The effects of nitrogen content in the sputtering gas, changes in target-to-substrate distance, and magnetron power density on the film composition were investigated with X-ray photoelectron spectroscopy and correlated to the dielectric breakdown strength and bandgap obtained from current-voltage measurements and Tauc plots. Films grown in pure Ar atmosphere at a large target-to-substrate distance displayed compositions containing metallic boron, which led to a decrease in the dielectric breakdown strength. The use of Ar:N2 mixtures and pure N2 eliminated metallic boron bonding. Decreasing the target-to-substrate distance and target power density during reactive sputtering resulted in B:N stoichiometry ratio closer to one and about 25–30 at.% oxygen. Smooth surface morphology films grown in pure N2 at a small target-to-substrate distance exhibited dielectric breakdown strength of 2.1–2.4 MV cm−1at 30 nm film thickness and bandgap of 5.4 eV. The results show the suitability of amorphous boron oxynitride for application as an insulator or gate dielectric in thin-films flexible transistors and other electronics when a low processing temperature is required.

An upgraded ultra-high vacuum magnetron-sputtering system for high-versatility and software-controlled deposition

Magnetron sputtering is a widely used physical vapor deposition technique. Reactive sputtering is used for the deposition of, e.g, oxides, nitrides and carbides. In fundamental research, versatility is essential when designing or upgrading a deposition chamber. Furthermore, automated deposition systems are the norm in industrial production, but relatively uncommon in laboratory-scale systems used primarily for fundamental research. Combining automatization and computerized control with the required versatility for fundamental research constitutes a challenge in designing, developing, and upgrading laboratory deposition systems. The present article provides a detailed description of the design of a lab-scale deposition chamber for magnetron sputtering used for the deposition of metallic, oxide, nitride and oxynitride films with automated controls, dc or pulsed bias, and combined with a coil to enhance the plasma density near the substrate. LabVIEW software (provided as Supplementary Information) has been developed for a high degree of computerized or automated control of hardware and processes control and logging of process details.

Anticorrosive Behavior Enhancement of Stainless Steel 304 through Tantalum-Based Coatings: Role of Coating Morphology

Stainless steel (SS 304) has good mechanical strength and corrosion resistance properties, but it is not resistive to halides corrosion which limits the use of SS 304 in seawater applications. In this regard, the present work has been focused on the investigation of anticorrosive nature of Ta2O5 (tantalum pentoxide), Ta3N5 (tantalum nitride) and TaON (tantalum oxynitride) films deposited on AISI 304 stainless steel by RF reactive magnetron sputtering technique for anticorrosive applications. The predominant influencing factors especially film composition and surface morphology of the coatings were characterized by XRD, FE-SEM and AFM. The anticorrosive properties of the coatings were investigated through potentiodynamic polarization (Tafel) test and electrochemical impedance spectroscopy in 1M NaCl solution at room temperature. The morphological results showed that the films are uniform with low surface roughness, i.e., less than 10 nm. The contact angle and corrosion study of the films revealed that the tantalum oxynitride film, with nanoscale roughness, has greatly enhanced the corrosion protection of the stainless steel in 1M NaCl solution. The tantalum oxynitride film showed hydrophobic nature and the corrosion current density in the order of 10-11 A/cm2, which led to better anticorrosive behavior. The highest polarization resistance (Rp) was observed for tantalum oxynitride film, i.e., 3.14 MΩ. Overall, tantalum-based coatings have reduced the corrosion rate and enhanced the inhibition efficiency (more than 50%) in comparison with the bare SS 304 substrate.

Experimental Investigation on the Sputtering Process for Tantalum Oxynitride Thin Films

Metal oxynitrides are compounds between nitrides and oxides with a certain level of photocatalytic functions. The purpose of this study is to investigate an appropriate range of oxygen flow rate during sputtering for depositing tantalum oxynitride films. The sputtering process was carried out under fixed nitrogen but variable oxygen flow rates. Post rapid thermal annealing was conducted at 800 °C for 5 min to transform the as-deposited amorphous films into crystalline phases. The material characterizations of annealed films include X-ray diffraction and Raman spectroscopy for identifying crystal structures; scanning electron microscope for examining surface morphology; energy-dispersive X-ray spectroscopy to determine surface elemental compositions; four-point probe and Hall effect analysis to evaluate electrical resistivity; UV-visible-NIR spectroscopy for quantifying optical properties and optical bandgaps. To assess the photocatalytic function of oxynitride films, the degradation of methyl orange in de-ionized water was examined under continuous irradiation by a simulated solar light source for six hours. Results indicate that crystalline tantalum oxynitride films can be obtained if the O2 flow rate is chosen to be 0.25–1.5 sccm along with 10 sccm of N2 and 20 sccm of Ar. In particular, films deposited between 0.25 and 1.5 sccm O2 flow have higher efficiency in photodegradation on methyl orange due to a more comprehensive formation of oxynitrides.

Hydrogen‐assisted nitrogen incorporation in zinc oxynitride films grown by rf sputtering

Zinc oxynitride has good electrical characteristics applicable for thin-film transistors in display devices. Since nitrogen has lower reactivity compared to oxygen, tiny amount of background oxygen can prohibit nitrogen incorporation into the films. In order to minimise the effects of oxygen, hydrogen gas was introduced during sputtering growth. The main hypothesis was that the hydrogen gas would react with oxygen to lower the oxygen density in the vacuum chamber. The films were grown by rf sputtering using zinc metal target and nitrogen gas. Energy dispersive spectroscopy results showed that nitrogen incorporation in the grown films was increased by the additional hydrogen. It was also shown that nitrogen pulsing was an effective method to maintain a reliable target condition.

Enhanced lithium electrochromic performance of tungsten oxide films by rapid co-synthesis of iron and tantalum oxides using cold atmospheric pressure plasma polymerization

Lithium electrochromic performance of organo-tungsten oxynitride (WOz1Cz2Nz3) films enhanced by additions of organo-iron oxynitride (FeOz1Cz2Nz3) or organo-tantalum oxynitride (TaOz1Cz2Nz3) with an atmospheric pressure plasma jet (APPJ) by a rapid deposition onto 60 Ω/square flexible polyethylene terephthalate (PET)/indium tin oxide (ITO) substrate at a short exposed duration of 54 s has been investigated. Flexible organo-tungsten-iron-tantalum oxynitride (WFexTayOz1Cz2Nz3) film possesses the significant Li+ ionic electrochromic performance, even though after being bent 360° around a 2.5-cm diameter rod for 1000 times and tested for 200 cycles of reversible Li+ ion intercalation and de-intercalation in a 1 M LiClO4-propylene carbonate electrolyte respectively by the potential sweep switching from the potential 2 V to − 1 V at a scan rate of − 40 mV/s and from the potential − 1 V to 2 V at a scan rate of 40 mV/s and by the potential step altering at the potential − 1 V for 20 s and the potential 2 V for 30 s, respectively. Li+ ionic intercalated charge of up to 13.2 mC/cm2 and optical modulation of up to 64.8% at a wavelength of 850 nm are proven for WFexTayOz1Cz2Nz3 film, respectively.

Evaluation of in Vitro Corrosion Behavior of Titanium Oxynitride Coated Stainless Steel Stents

Coronary artery disease (CAD) affects every fifth person in the world. The gold-standard treatment for CAD is stent implantation, however, the existing therapy is not sufficient. In recent years, titanium oxynitride (TiOxNy) coatings on bare metal stents (BMSs) attracted the attention of many researchers around the world due to their promising results and improved surface properties. However, good coating adhesion and coverage of the inner surface in stent applications is still a challenging task. Moreover, enhanced corrosion resistance and durability over a longer period under the influence of an aggressive biological environment is one of the main requirements while developing novel coatings for bare-metal stents. In this work, the titanium oxynitride (TiOxNy) coated stainless steel stents were fabricated by magnetron sputtering and the corrosion behavior of coated and uncoated stents has been studied using immersion, fluid dynamic, and electrochemical corrosion tests. For the first time, the entire stent surface has been used for quantitative corrosion tests on stents. We discuss and compare the in vitro biostability and corrosion behavior of bare stainless steel (316L) and titanium oxynitride films (TiOxNy) coated stents.TiOxNy coatings provide valuable stability to the BMS against harsh environments or conditions. The coated stents are remarkably more stable when compared with the reference uncoated stents (316L BMS), regardless of the ratio of O2 and N2. The variation of stent coating parameters is still possible to get more anticorrosive and biostable behavior; therefore, the results could provide the basis for further research.

Investigation of optical and anti-corrosive properties of reactively sputtered vanadium oxynitride thin films

Abstract In the present study, synthesis of Vanadium oxynitride thin films on various substrates are done using reactive magnetron sputtering technique. Physical and chemical properties were studied through XRD, FE-SEM and AFM methods. Optical and anti-corrosive properties were investigated by UV–Vis spectroscopy and potentiodynamic polarization (Tafel). Electrochemical impedance spectroscopy (EIS) methods were used to study the interaction of coating and 3.5 wt% NaCl solution. Reactively sputtered vanadium oxynitride films have good uniformity, low roughness i.e. below 50 nm and thickness of 250 nm in 30 min deposition. The study reveals that the vanadium oxynitride coating has an average transmittance of 42% in the wavelength range from 550 nm to 800 nm. The compound exhibited an energy band gap of 2.13 eV. The coatings show good anticorrosive nature by reducing the corrosion current by 6 times due to its passivating behavior.