Nitrogen Content In Films Research Articles

Design, preparation and characterization of antireflective coatings using oxynitride films

In present paper, we introduce an investigation of aluminum oxynitride films deposition using one metallic target in various gas mixture. The optimized preparation conditions for such reactive sputtering were found. Non-optimized conditions led to sputtering target poisoning or under-stoichiometric films formation. The reactive deposition process was guided by the active feedback control system. Dependence between gas composition and changes of nitrogen concentration in the films and their optical properties were investigated. The increase of nitrogen content in films leads to increases in extinction coefficient in UV region and refractive index in the whole investigated wavelength range. It was shown the possibility of using oxynitride films for antireflective coating (AR) deposition. The coating composed from three layer of oxynitrides with changing the composition. It has low surface roughness and low compressive stress.

Influence of the sputtering reactive gas on the oxide and oxynitride La[sbnd]Ti[sbnd]O[sbnd]N deposition by RF magnetron sputtering

Perovskite LaTiON thin films have been grown by radio frequency magnetron sputtering from a LaTiO2N target. With a very low base pressure in the deposition chamber, two types of films can be obtained: colored oxynitride LaTiO2N films when nitrogen gas is introduced during sputtering or black N-doped LaTiO3 films when deposition is performed in pure argon. On SrTiO3 (001) substrate heated at 750°C, LaTiO2N films are epitaxially grown, while N:LaTiO3 films are poorly crystallized. With a higher base pressure in the deposition chamber, transparent La2Ti2O7 films are produced. They are (012) textured on (001) SrTiO3 substrate. As observed during the reactive sputtering of metallic targets, the evolution of the deposition rate and the nitrogen content in films according to the N2 percentage in the plasma is abrupt.

Study of Silicon Nanocrystals Formation in Annealed Amorphous In Situ Nitrogen Doped Silicon Thin Films Obtained by Low Pressure Chemical Vapor Deposition

In this work, we investigate the formation of silicon nanocrystals in annealed low pressure chemical vapor deposition in situ nitrogen doped silicon thin films (SiNx) obtained at low temperature (465 C) by using a mixture of disilane (Si2H6) and ammonia (NH3). Results show that nitrogen content in films plays an important role in defining the obtained films morphology in terms of crystallites sizes and their distribution. Indeed, according to the nitrogen content introduced in films, the crystalline state of films varies from a submicron crystalline structure to a nanocrystalline structure. An average silicon nanocrystalline size of 10 nm was obtained for film with x = 0:07 nitrogen content, annealed under a temperature of 850 C during 2 h.

Effect of nitrogen content in amorphous SiCxNyOz thin films deposited by low temperature reactive magnetron co-sputtering technique

Amorphous silicon oxycarbonitride (SiCxNyOz) films have been deposited on Si substrates by low temperature reactive magnetron co-sputtering of silicon and graphite targets in mixed Ar/N2 atmosphere. Our studies are focused on the influence of nitrogen incorporation on deposition rate, film composition, film structure, chemical bonds, and electrical resistivity of SiCxNyOz films investigated by profilometry, Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and four-point probe method. RBS results show that all samples contain significant amounts of oxygen (up to 16at.%) which led to the formation of SiCxNyOz. Further, XPS results show that most of this oxygen is located in the film surface. With the addition of N2 gas in the plasma, the carbon, and nitrogen contents in the films increase. The increased carbon content is due to the contribution of chemically driven sputtering of the graphite target and the reduction of the sputtering rate of the silicon target owing to poisoning by nitrogen. Raman spectra suggest that the films contain amorphous phases and that the a-C clusters suffer a graphitization with increased N2 gas flow rate. The XRD analysis confirmed the amorphous structure of these films. According to the XPS analysis, the increase in nitrogen content leads to an increase in SiN and CN bonds, decreasing the SiC, SiSi, and CC bonds. Finally, the films electrical resistivity depends mainly on the nitrogen content, which makes it possible to obtain semiconductor or insulator SiCxNyOz films only by adjusting the N2 concentration in the gas phase during the deposition process.

Effect of nitrogen partial pressure on the structure, physical and mechanical properties of CrB 2 and Cr–B–N films

The investigation of structure and properties of Cr–B and Cr–B–N films deposited by direct current magnetron sputtering of CrB 2 target in argon and argon–nitrogen environments, respectively is presented. The nitrogen partial pressure was kept at 10, 15, and 25% of the total pressure. The microstructure, phase and chemical composition of Cr–B–(N) films were studied by means of X-ray diffraction, transmission- and scanning-electron microscopy, X-ray photoelectron spectroscopy, electron probe microanalysis and secondary neutral mass-spectrometry. The films were characterized in terms of their electrical resistivity, optical reflectivity and transmittance. Measurements of hardness and elastic modulus were performed by depth sensing nanoindentation. The results obtained show that the films deposited in pure Ar had a hexagonal AlB 2-type structure with crystallites, 15–17 nm in lateral size, elongated in the direction of film growth. The Cr–B–N films consisted of nanocrystalline nc-CrB 2 and amorphous a-BN phases. As the nitrogen content in films was raised, the volume fraction of the nc-CrB 2 phase decreased and a-BN phase increased. When nitrogen was added to the gas discharge during deposition, the nc-CrB 2 crystallite size decreased down to 3–5 nm. Without nitrogen, the films exhibited a columnar morphology. Nitrogen introduction suppressed the columnar growth of films because formation of a-BN intergranular layers. The films deposited under optimal parameters showed hardness in the range of 36–43 GPa and Young's modulus below 300 GPa. For all films, electrical resistivity values between approximately 200 and 700 µΩ cm were recorded.

Synthesis and characterization of atomic layer deposited titanium nitride thin films on lithium titanate spinel powder as a lithium-ion battery anode

Lithium titanate spinel (Li 4Ti 5O 12, or LTS) is receiving consideration as a nanopowder anode material for use in lithium-ion batteries. LTS has more positive working potential than traditional graphite anodes, and it does not react with electrolyte components. However, the main drawback of LTS powder is its poor interparticle electronic conductance that reduces the high-rate ability of the electrode. To improve this we have coated the surface of the LTS powder with a titanium nitride layer by atomic layer deposition (ALD). In situ infrared spectroscopy studies were conducted to confirm the attachment of the titanium precursor. The nitrogen content of films was measured by total nitrogen content testing. Transmission electron microscopy (TEM) micrographs confirmed the formation of a thin titanium nitride film around LTS particles by ALD. Finally, lithium cells with electrodes made of original and modified LTS nanopowders were assembled and tested.

A-CN thin film properties as a function of laser ablation plasma parameters

In this work the laser ablation plasma parameters (mean kinetic ion energy, plasma density and type of excited species) were studied as a function of the laser fluence under different working atmospheres. Amorphous carbon nitride thin films were deposited using the plasma conditions previously diagnosed in order to establish a correlation between plasma parameters and thin film properties. The plasma was produced using the fundamental line of a Nd:YAG laser with 28 ns pulse duration focused on a high purity graphite target. A single planar probe was used to determine the mean kinetic energy of ions and their density. Time and space resolved optical emission spectroscopy was used to identify the excited species present in the plasma. It could be established that the film nitrogen content as a function of the ion energy has an abrupt increase for low ion energies and for greater energies saturation was observed. The saturation value depended on the working pressure, with a maximum value of 30 at.% at 10 Pa. A similar trend was observed for the band gap, which also reached a saturation value, which depended on the working pressure. The density of the material and its microstructural properties showed different behaviors. It was observed that a-CN thin films with the same composition but different microstructural and optical properties could be obtained.

Homogeneous Decomposition of Aryl- and Alkylimido Precursors for the Chemical Vapor Deposition of Tungsten Nitride: A Combined Density Functional Theory and Experimental Study

MOCVD growth of tungsten nitride (WN(x)()) and tungsten carbonitride (WN(x)()C(y)()) thin films has been reported from the complexes Cl(4)(CH(3)CN)W(NR) (1: R = Ph; 2: R = (i)Pr; 3: R = C(3)H(5)). To evaluate the role of the imido substituent in film growth, gas-phase homogeneous decomposition of precursor molecules was investigated using density functional theory (DFT) calculations. Computational results and NMR kinetics of acetonitrile exchange by 2 in solution verified that dissociation of the acetonitrile ligand should be facile for 1-3 in the temperature range used for film growth (>450 degrees C). A computational search for transition states for cleavage of W-Cl bonds in the presence of H(2) carrier gas was consistent with a sigma-bond metathesis pathway. Natural bonding orbital (NBO) analysis and bond energy calculations indicated that 1 has a stronger N-C(imido) bond and a slightly weaker W-N bond than 2 and 3, suggesting a greater role for W-N bond cleavage in depositions from 1. These results are consistent with mass spectrometric fragmentation patterns from 1-3 and low nitrogen content in films deposited from 1 as compared to those from 2 and 3.

Intrinsic reoxidation of microwave plasma-nitrided gate dielectrics

The impact of nitrogen concentration on nitrided gate dielectric scaling has been found to depend on the process conditions used to incorporate nitrogen. For example, the variation in the nitrogen content of gate dielectrics processed at high pressure (>107Pa) has a strong impact on gate leakage current, but not on equivalent oxide thickness. While this effect allows nearly independent control of gate leakage and drive currents of the device, it prevents scaling of the gate dielectric. In contrast, it is found that at low process pressures (<13Pa) the gate dielectric behaves in a more conventional fashion, where both electrical oxide thickness and film leakage change with film nitrogen content. A model is proposed to explain this behavior based on an intrinsic reoxidation process. Chemical bond analysis results are presented to support the proposed model.

Nitrogen effect on the electrical properties of CN x thin films deposited by reactive magnetron sputtering

Amorphous carbon nitride (a-CN x ) thin films have been synthesized by rf reactive magnetron sputtering of a graphite target in an Ar/N 2 gas mixture. The total discharge pressure was 1.3 Pa and an N 2 fraction in plasma was between 0 and 0.5. The electrical resistivity of films was studied as a function of temperature between 80 and 360 K. At very low nitrogen contents in films, the resistivity decreases with increasing nitrogen content, whereas there is a strong increase in ρ at nitrogen content higher than 13 at.%. Chemical composition and C–N bonds was investigated by X-ray Photoelectron Spectroscopy (XPS). The results, related to the core level C1s and N1s, show the structural change. The temperature dependence evolutions was thermally activated and suggest the presence of two types of conduction associated with two different activation energies. The conductivity variation was interpreted within the limits of the band structure model of the π electrons in a disordered carbon with the presence of localized states.

The effect of r.f. substrate bias on the properties of carbon nitride films produced by an inductively coupled plasma chemical vapor deposition

Carbon nitride films were deposited on a Si (100) wafer by an inductively coupled plasma assisted chemical vapor deposition (ICP-CVD) at room temperature. A mixture of N 2 and C 2H 2 were used as the precursor. Additional r.f. power (13.56 MHz) was applied to the substrate with various negative self bias voltages ( V self=0 to −60 V), and the effect of the substrate bias on the structure and properties of the films was investigated. The composition and chemical bonding of the films were analyzed by Raman spectroscopy, Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The surface roughness of films was investigated by atomic force microscopy (AFM). It was found that nitrogen content of films were in the range of 13.5–21.4 at.%, decreased with increasing bias voltage. As the bias voltage was increased, the deposition rate decreased due to resputtering and the substrate temperature increased as a result of the energetic ions. The film hardness increased with increasing bias voltage up to 30 GPa at −60 V. The results from Raman and XPS analyses showed that the amount of sp 3 C C or sp 3 C N bonds increased with increasing bias voltage, while the number of the C H, N H and sp 2 C N bonds decreased.

Bonding configurations in amorphous carbon and nitrogenated carbon films synthesised by femtosecond laser deposition

The effect of nitrogen addition and laser fluence on the atomic structure of amorphous carbon films (a-C) synthesized by femtosecond pulsed laser deposition has been studied. The chemical bonding in the films was investigated by means of X-ray photoelectron (XPS) and Raman spectroscopies. XPS studies revealed a decrease in the sp3 bonded carbon sites and an associated increase in the N-sp2C bonding sites with increasing nitrogen content in the CNx films. An increase in laser fluence from 0.36 to 1.7 J/cm2 led to a rise in sp3C sites. These results were further confirmed by Raman spectroscopy. The ID/IG ratio increased monotonically and G line-width decreased with the increase of nitrogen content in the films indicating a rise in either the number or the size of the sp2 clusters. Furthermore a visible excitation wavelength dependence study established the resonant Raman process in a-C and CNx films.

Effects of Irradiation by Low Energy Nitrogen Ions on Carbon Nitride Thin Films

ABSTRACTCarbon nitride (CNx) thin films have been prepared by hot carbon filament chemical vapor deposition, and the nitrogen content in the films is approximately 0.05. The CNx films have been irradiated by 0.1 keV nitrogen ions to increase the nitrogen content after deposition. The nitrogen content in the CNx films was obtained with X-ray photoelectron spectroscopy. Scanning electron microscopy was employed to study microstructures of the films. The experimental results show that nitrogen ions are chemically combined with the CNx films and as a result the nitrogen content increases up to approximately 0.30. Furthermore, it is found that nitrogen ions change the film microstructures and sputter the surfaces of CNx films.

Growth and characterisation of hard and elastic carbon nitride thin films

Hard CN x films were prepared by nitrogen ion beam-assisted deposition (IBAD) of evaporated carbon on silicon wafers with a nitrogen ion energy of 100–1200 eV, ion/neutral transport ratios from 0.7 to 1.7, and deposition temperatures from RT to 1000°C. By varying the deposition parameters a maximum nitrogen content of below 33 at.% was found at N/C transport ratios of approximately 1.2. XPS measurements reflect a shift of the main chemical state of the nitrogen bonds with changing nitrogen content of the films and with increasing deposition temperature. The nitrogen content of the films decreases significantly with increasing temperatures above 600°C. EELS investigations show weak changes of the plasmon peak position and the sp 2/sp 3 ratio with increasing deposition temperature in correlation to the nitrogen content of the carbon films. Nanoindentation techniques have been used to investigate the mechanical properties of the films. All measured structural and mechanical properties correlate with the analysed nitrogen content.

Temperature and substrate influence on the structure of TiNxOy thin films grown by low pressure metal organic chemical vapour deposition

This paper presents the growth and characterization of titanium oxinitride (TiNxOy) films grown by low pressure metal organic chemical vapour deposition (LP-MOCVD). The film nitrogen content, obtained by Rutherford backscattering spectroscopy (RBS), increases as the growth temperature increases (from 23at.% at 450°C to 46at.% at 750°C). Below 550°C, the films do not show any X-ray diffraction pattern. Above 550°C, the deposited films present the (111) and (200) TiN textures. Films deposited on (100) Si exhibit a 2θ shift to higher Bragg angles, depending on the N/O ratio. These shifts are explained by using a substitutional oxygen model. Moreover, the atomic structure of such materials is described from this behaviour in terms of lattice vacancies and N/O substitutions, leading to different titanium valencies confirmed by X-ray photoelectron spectroscopy (XPS) analysis.

Study of Amorphous Carbon Nitride Films by X-ray Photoelectron Spectroscopy

X-ray photoelectron spectroscopy measurements of amorphous carbon nitride films have been performed. The samples were prepared by magnetic filtered plasma deposition, and cleaned by Ar+ ion sputtering before analysis to eliminate the surface contamination. The spectra include standard survey scans and high resolution scans of the photoelectron peaks of C, N, and O atoms. These spectra were collected using a monochromatic Mg Kα x-ray source operated at 300 W (20 mA, 15 kV). The survey scans were collected using an 80 eV pass energy, while high resolution scans were recorded using a 20 eV pass energy. By deconvolution of the XPS spectra, it was found that the XPS C 1s and N 1s signals could be deconvoluted into three and two Gaussian peaks, respectively. A plausible suggestion on the assignments of XPS peaks to C3N4, CNx, and ta-C phases was discussed. The relative abundance of CN bonds, calculated from the area of the respective C 1s Guassian peaks divided by the total area of the C 1s spectra, was determined to be 80%, and the actual nitrogen content in films in terms of atomic percentage is 46%.

Effects of nitrogen on the structure and properties of highly tetrahedral amorphous carbon films

Nitrogen-containing tetrahedral amorphous carbon films (ta-C) have been prepared using a magnetic field filtered plasma stream deposition method. The plasma stream was first formed by sputtering of a graphite target in nitrogen-argon atmospheres. The partial pressure of nitrogen, , was in the range 0-7 Pa at total pressure of deposition Pa. The optical and electrical properties of samples were studied using x-ray photoelectron spectroscopy (XPS), Fourier transform infrared absorption spectroscopy (FTIR), UV-visible optical absorption spectroscopy and measurements of electrical conductivity in the temperature range 300-500 K. The incorporation of small amounts of nitrogen will result in an increase in electrical conductivity, a slight drop of the band gap and an increase in band-tail absorption. These suggest that incorporation of a small amount of nitrogen into ta-C films will induce graphitization of bonding. For samples deposited at Pa, nitrogenation of films is very pronounced. The actual nitrogen content in films in terms of atomic percentage can be as much as 47%. The films have a wide band gap of 4.05 eV and an extremely low electrical conductivity. These suggest that a carbon nitride film is formed. The configurations of N atoms in the ta-C network are identified and discussed.

Structural characterisation (AFM and XRD) and hardness of spultered CrxNy coatings

Hard coatings for wear and oxidation/corrosion protection based on chromium nitride were deposited by means of a commercial rf magnetron sputtering unit with a mixture of nitrogen and argon from a target of the pure metal. The present paper reports on the influence of deposition parameters on coating morphology, crystallographic structure, and hardness. The coating surfaces viewed by atomic force microscopy showed that grain shape depends on the composition of the vapour phase, and especially on the presence or absence of reactive gas. In addition, special attention was paid to the first stages of growth. The crystalline phases Cr, Cr2N, and CrN were identified by X -ray diffraction analysis as a function of the film nitrogen content. Finally, hardness measurements were performed and compared to coating structure and composition.

Superstoichiometric h-BN films synthesized by ion-beam assisted deposition; N-concentration and respective ion energy dissipation

Experimental data on the nitrogen content in films grown by ion-assisted deposition are compared to the specific energy (per film atom) dissipated by the ions in displacement damage. As shown there exists a proportionality between the overstoichiometric N content and the energy dissipated in a superficial layer of the growing film.

An ultrahigh vacuum, magnetron sputtering system for the growth and analysis of nitride superlattices

An ultrahigh vacuum, magnetron sputtering system designed for the deposition and in situ analysis of nitride superlattices is described. Superlattices are deposited from two sputter sources aimed at a fixed substrate position. The chamber features a sample insertion load lock, a computer-controlled shutter to modulate the sputtered fluxes, a retarding field analyzer for in situ low energy electron diffraction and Auger electron spectroscopy (AES), and substrate heating to >800 °C. Deposition of epitaxial TiN, VN, NbN, and nitride superlattices is described. Deposition rates decreased, and the film nitrogen content increased until stoichiometry was reached, as the N2 partial pressure was increased. The film thickness and composition were uniform to within 10% over the 1.2 cm wide substrates. AES studies of the initial stages of TiN deposition onto VN(100) indicated a layer-by-layer growth mechanism. Single-crystal TiN/NbN(100) and TiN/V0.6Nb0.4N(100) superlattices were grown and found to have flat, sharp interfaces, and exhibited hardness enhancements in excess of 200% over homogeneous alloys of the same composition.