Nitrogen Sputtering Research Articles

Production of High-Power Nitrogen Sputtering Plasma for TiN Film Preparation

High-density nitrogen plasma was produced using a high-power pulsed power modulator to sputter titanium targets for the preparation of titanium nitride film. The high-power pulsed sputtering discharge unit consisted of two targets facing each other with the same electrical potential. The titanium target plates were used as target materials with dimensions of 60 mm length, 20 mm height, and 5 mm thickness. The gap length was set to be 10 mm. The magnetic field was created with a permanent magnet array behind the targets. The magnetic field strength at the gap between the target plates was 70 mT. The electrons were trapped by the magnetic and electric fields to enhance the ionization in the gap. The nitrogen and argon gases were injected into the chamber with 4 Pa gas pressure. The applied voltage to the target plates had an amplitude from −600 V to −1000 V with 600 μs in pulse width. The target current was approximately 10 A with the consumed power of 13 kW. The discharge sustaining voltage was almost constant and independent of the applied voltage, in the same manner as the conventional normal glow discharge. The ion density and electron temperature at the surface of the ionization region were obtained as 1.7 × 1019 m−3 and 3.4 eV, respectively, by the double probe measurements. The vertical distribution of ion density and electron temperature ranged from 1.1 × 1017 m−3 (at 6 cm from the target edge) to 1.7 × 1019 m−3 and from 2.4 eV (at 6 cm from the target edge) to 3.4 eV, respectively. From the emission spectra, the intensities of titanium atoms (Ti I), titanium ions (Ti II), and nitrogen ions (N2+) increased with increasing input power. However, the intensities ratio of Ti II to Ti I was not affected by the intensities from N2+.

Effect of nitrogen sputtering pressure on the electronic properties of LiPON solid-state electrolyte

Effect of nitrogen sputtering pressure on the electronic properties of LiPON solid-state electrolyte

A strong dependence of sputtering power on c‐axis oriented aluminium nitride on Si (111): A structural and electrical study

AbstractGrowing and controlling the c‐axis orientation of the aluminium nitride (AlN) thin film on unheated Si (111) substrates using reactive magnetron sputtering are challenging. Sputtering parameters such as nitrogen concentration and sputtering power were effectively tuned to grow the c‐axis oriented AlN thin film. The results show that a low concentration of (25%) N2 is enough for forming AlN at a reduced flow rate, whereas a higher flow rate requires a higher concentration of N2. Low concentration with a low flow rate is preferred to grow AlN at low temperature and power. The poor crystallinity of AlN with (100) orientation was improved by varying the power from 75 to 175 W. The X‐ray diffraction results confirmed the improvisation of crystallinity of grown AlN films and indicated the strong dependence of preferred c‐axis orientation on sputtering power. Also, the dependence of sputtering power on microstrain and stress was analysed. The surface morphology study by field emission scanning electron microscopy and topography measured by an atomic force microscope shows a dependence on sputtering power. The high c‐axis orientation was observed at 175 W with low surface roughness, low leakage current density (2 × 10−9 A/cm2) and low dielectric constant (6.8).

Interface and crystallization evolution induced by reactive nitrogen and oxygen sputtering in Ni/Ti multilayer

Ni/Ti multilayers were reactively deposited with a gas mixture of Ar, N2 and O2 using the magnetron sputtering, while (N2 + O2)/Ar flow ratio during the sputtering process was varied. A detailed study on the microstructure evolution and interfacial properties was performed using grazing incidence X-ray reflectivity, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray diffuse scattering, and transmission electron microscopy. With the increase in (N2 + O2)/Ar flow ratio, the grain size in Ni layers first decreases and then increases at a critical point of 25.0 %, followed with the crystal phase transforming from Ni into NiO. The mechanism of microstructure evolution in Ni layers due to N2 and O2 gas incorporation is discussed in this paper. The interfaces of Ni/Ti multilayer are smoothened due to a decrease in the size of Ni grains. Meanwhile, the interfacial effects including the vertical replication of interfacial roughness and the diffusion between adjacent Ni and Ti layers are suppressed for the N2 and O2 gas incorporation. Furthermore, the lateral correlation length of interfacial roughness varies with (N2 + O2)/Ar flow ratio, which presents the relevance with the grain size.

Gallium nitride films of high n-type conductivity grown by reactive sputtering

The origin of n-type conductivity in as grown, undoped GaN has been debated over several decades, with contradictory views. This work deals with reactively sputtered, undoped GaN films in which a large decrease of resistivity from ∼105 to ∼2 × 10−3 Ω cm is seen, as the nitrogen percentage in argon–nitrogen sputtering atmosphere is decreased from 100% to 10%, resulting in high electron concentration ∼1020 cm−3 at the lower end of nitrogen pressure. The electrical behavior of these films has been correlated with their composition and chemical state to understand the nature of point defects which influence n-type conductivity. Powder x-ray diffraction and phi scans of the undoped GaN films grown by sputtering of GaAs at 700 °C on c-sapphire reveal epitaxial growth of single phase GaN. SIMS results show the absence of arsenic in the films and uniformly distributed gallium and nitrogen along with oxygen impurity, across their thickness. XPS data reveal the decrease of N/Ga ratio, as the nitrogen partial pressure is decreased along with the increase of uncoordinated Ga, indicating the formation of nitrogen vacancies. In the high resistivity films grown at higher nitrogen percentage in sputtering atmosphere, oxygen impurities appear to be primarily responsible for creation of n-type carriers, which are compensated by Ga vacancies and possibly VGa–ON complexes. The drastic enhancement of n-type conductivity and carrier concentration in the low resistivity films grown at lower nitrogen percentage, which reveal significantly smaller nitrogen content, is attributed dominantly to the increase in nitrogen vacancies and uncoordinated Ga.

Radiation tolerance of nanostructured TiAlN coatings under Ar+ ion irradiation

The radiation tolerance of TiAlN coatings under irradiation with 200 keV Ar+ ions is studied at room temperature. The ion fluence varied in the range of 1·1016–2·1017 ions/cm2. The TiAlN coatings were deposited by reactive magnetron sputtering on single crystalline silicon wafers as well as on AISI 304 stainless steel bars. Elemental composition of the coatings was investigated using Rutherford backscattering spectrometry with He+ ions of 2.53 MeV and 4.53 MeV as well as by energy-dispersive X-ray spectroscopy using 18 keV electrons. Phase composition and structure of TiAlN coatings were examined by X-ray diffraction and scanning electron microscopy. Mechanical properties of TiAlN coatings were evaluated by nanoindentation using a nanohardness tester with a Berkovich diamond tip and applying the Oliver-Pharr method. Some selective nitrogen sputtering was detected caused by the Ar+ ion irradiation. The TiAlN coatings crystallites refined under argon ion irradiation. It was found that the irradiation fluence of 2·1017 ions/cm2 is a threshold fluence, at which the solid solution decomposition starts. Ion irradiation causes mechanical properties improvement up to the fluence of 5·1016 ions/cm2. No destruction processes of the coatings such as blistering or flaking were detected for all irradiation fluences used in this study.

Sputtering and nitridation of transition metal surfaces under low energy, steady state nitrogen ion bombardment

Transition metal surfaces exposed to low-energy reactive ions undergo dynamic changes in composition and density due to implantation and compound formation. We report measurements of nitrogen ion induced sputter yields for transition metals relevant to fusion and optics applications. Thin films of molybdenum, ruthenium, palladium and tungsten are bombarded by nitrogen ions of kinetic energies in the range of 50–500 eV at steady state fluences (1 × 1018ions/cm2). Measured sputter yields are explained through energy and momentum transfer under the binary collision approximation using the Monte Carlo code TRIDYN. X-ray Photoelectron spectroscopy (XPS) studies showed the nitrogen content in the films at the end of ion exposure is independent of incoming ion energy. This occurs due to competing implantation and preferential surface nitrogen sputtering processes within the XPS probing depth. All metals investigated showed evidence of a nitride formed due to energetic nitrogen impact. The combination of XPS and TRIDYN simulations were applied to extract effective reaction cross-sections for each metal.

Coating of overstoichiometric transition metal nitrides (TMNx (x > 1)) by magnetron sputtering

This article reports on the formation of strongly overstoichiometric ZrNx>1 and Ti(Al, V)Nx>1 coatings by reactive magnetron sputtering. Problems in the formation of overstoichiometric coatings and possible ways to form strongly overstoichiometric TMNx>1 nitride coatings up to TMNx=2 dinitride coatings are discussed; here, TM are transition metals such as Ti, Zr, Mo, Ta, Nb, W, etc. The coating stoichiometry x = N/TM strongly influences its electrical and mechanical properties. The creation and properties of reactively sputtered ZrNx coatings were investigated. It was found that (1) the electrical resistivity of the ZrNx coating varies with increasing x from well electrically conducting films with x ≤ 1 through semi-conducting films with x ranging from 1 to ≤ 1.26 to non-conductive with x ≥ 1.3, showing that the stoichiometry x is a strong parameter which enables to control an electric conductivity of the coating in a wide range, (2) electrically conductive coatings with x ≤ 1 are harder than the semiconducting and electrically insulating coatings, and (3) the ZrN2 dinitride film cannot be created due to the formation of a Zr3N4 phase whose formation enthalpy is greater than that of a ZrN2 phase. Further, it is shown that the main problem in the formation of strongly overstoichiometric TMNx>1 and dinitride TMN2 coatings is a strong increase of ionization of the nitrogen sputtering gas to achieve a necessary high ratio N/TM > 1. Trends enabling the mastery of formation of the TMN2 dinitride coatings are briefly outlined.

Molecular dynamics investigation of hexagonal boron nitride sputtering and sputtered particle characteristics

The sputtering of hexagonal boron nitride (h-BN) by impacts of energetic xenon ions is investigated using a molecular dynamics (MD) model. The model is implemented within an open-source MD framework that utilizes graphics processing units to accelerate its calculations, allowing the sputtering process to be studied in much greater detail than has been feasible in the past. Integrated sputter yields are computed over a range of ion energies from 20 eV to 300 eV, and incidence angles from 0° to 75°. Sputtering of boron is shown to occur at energies as low as 40 eV at normal incidence, and sputtering of nitrogen at as low as 30 eV at normal incidence, suggesting a threshold energy between 20 eV and 40 eV. The sputter yields at 0° incidence are compared to existing experimental data and are shown to agree well over the range of ion energies investigated. The semi-empirical Bohdansky curve and an empirical exponential function are fit to the data at normal incidence, and the threshold energy for sputtering is calculated from the Bohdansky curve fit as 35 ± 2 eV. These results are shown to compare well with experimental observations that the threshold energy lies between 20 eV and 40 eV. It is demonstrated that h-BN sputters predominantly as atomic boron and diatomic nitrogen, and the velocity distribution function (VDF) of sputtered boron atoms is investigated. The calculated VDFs are found to reproduce the Sigmund-Thompson distribution predicted by Sigmund's linear cascade theory of sputtering. The average surface binding energy computed from Sigmund-Thompson curve fits is found to be 4.5 eV for ion energies of 100 eV and greater. This compares well to the value of 4.8 eV determined from independent experiments.

Interpretation of X-ray photoelectron spectra of carbon-nitride thin films: New insights from in situ XPS

We report on angular-resolved x-ray photoelectron spectroscopy (XPS) studies of magnetron sputtered CNx thin films, first in situ (without air exposure), then after air exposure (for time periods ranging from minutes to several years), and finally after Ar ion etching using ion energies ranging from 500 eV to 4 keV. The as-deposited films typically exhibit two strong N1s peaks corresponding to pyridine-like, and graphite-like, at ∼398.2 eV and ∼400.7 eV, respectively. Comparison between in situ and air-exposed samples suggests that the peak component at ∼402–403 eV is due only to quaternary nitrogen and not oxidized nitrogen. Furthermore, peak components in the ∼399–400 eV range cannot only be ascribed to nitriles or pyrrolic nitrogen as is commonly done. We propose that it can also be due to a polarization shift in pyridinic N, induced by surface water or hydroxides. Argon ion etching readily removes surface oxygen, but results also in a strong preferential sputtering of nitrogen and can cause amorphization of the film surface. The best methods for evaluating and interpreting the CNx film structure and composition with ex-situ XPS are discussed.

Characterization of nitrogen species incorporated into graphite using low energy nitrogen ion sputtering.

The electronic structures of nitrogen species incorporated into highly oriented pyrolytic graphite (HOPG), prepared by low energy (200 eV) nitrogen ion sputtering and subsequent annealing at 1000 K, were investigated by X-ray photoelectron spectroscopy (XPS), angle-dependent X-ray absorption spectroscopy (XAS), and Raman spectroscopy. An additional peak was observed at higher binding energy of 401.9 eV than 400.9 eV for graphitic1 N (graphitic N in the basal plane) in N 1s XPS, where graphitic2 N (graphitic N in the zigzag edge and/or vacancy sites) has been theoretically expected to appear. N 1s XPS showed that graphitic1 N and graphitic2 N were preferably incorporated under low nitrogen content doping conditions (8 × 10(13) ions cm(-2)), while pyridinic N and graphitic1 N were dominantly observed under high nitrogen content doping conditions. In addition, angle-dependent N 1s XAS showed that the graphitic N and pyridinic N atoms were incorporated into the basal plane of HOPG and thus were highly oriented. Furthermore, Raman spectroscopy revealed that low energy sputtering resulted in almost no fraction of the disturbed graphite surface layers under the lowest nitrogen doping condition. The suitable nitrogen doping condition was discovered for realizing the well-controlled nitrogen doped HOPG. The electrochemical properties for the oxygen reduction reaction of these samples in acidic solution were examined and discussed.

Effect of the preparation conditions of Al–3%Y powder on its structural and adsorption properties

In view of the great practical utility of aluminum–rare earth metal (REM) powders as adsorbents and catalyst supports, the dispersion composition and morphology of Al–3%Y alloy powder particles obtained by various methods (gas plasma recondensation, nitrogen sputtering) were studied by low-temperature nitrogen adsorption, scanning electron microscopy, XRD, etc. The phase composition of the powders was determined, and the amount of active aluminum was calculated. The nitrogen adsorption on the powder surface was studied experimentally at–196°С at relative pressures of Р/Рs = 10–3–0.999. The specific surface areas of the powders were determined.

Sputtering of amorphous silicon nitride irradiated with energetic C60 ions: Preferential sputtering and synergy effect between electronic and collisional sputtering

Amorphous silicon nitride films (thickness 30nm) deposited on Si(001) were irradiated with 30–1080keV C60 and 100MeV Xe ions to fluences ranging from 2×1011 to 1×1014ions/cm2. The composition depth profiles of the irradiated samples were measured using high-resolution Rutherford backscattering spectrometry. The sputtering yields were estimated from the derived composition profiles. Pronounced preferential sputtering of nitrogen was observed in the electronic energy loss regime. In addition, a large synergy effect between the electronic and collisional sputtering was also observed. The sputtering yields were calculated using the unified thermal spike model to understand the observed results. Although the calculated results reproduced the observed total sputtering yields with a lowered sublimation energy, the observed preferential sputtering of nitrogen could not be explained. The present results suggest an additional sputtering mechanism related to the electronic energy loss.

Increasing the active surface of titanium islands on graphene by nitrogen sputtering

Titanium-island formation on graphene as a function of defect density is investigated. When depositing titanium on pristine graphene, titanium atoms cluster and form islands with an average diameter of about 10 nm and an average height of a few atomic layers. We show that if defects are introduced in the graphene by ion bombardment, the mobility of the deposited titanium atoms is reduced and the average diameter of the islands decreases to 5 nm with monoatomic height. This results in an optimized coverage for hydrogen storage applications, since the actual titanium surface available per unit graphene area is significantly increased.

Electroluminescence of copper-nitride nanocrystals

Nanocrystals can behave as quantum boxes with confined electronic states governing their optoelectronic properties. The formation of nanometer-size crystals of copper nitride $({\mathrm{Cu}}_{3}\mathrm{N})$ grown by nitrogen sputtering of a Cu(110) surface is reported. Scanning tunneling spectroscopy shows that the nanocrystals exhibit a series of well-defined sharp electronic resonances, which correspond to confined free-electron-like states. We observe that electrons from a scanning tunneling microscope tip induce the emission of light with a larger efficiency than on the bare metal surface. The spectral analysis of the emitted photons reveals various radiative inelastic pathways enabled by the confined states, which explain the enhanced light emission. Thus, the ${\mathrm{Cu}}_{3}\mathrm{N}$ nanocrystals can be employed as nanometer-size light sources.

RF sputtering of polycrystalline (100), (002), and (101) oriented AlN on an epitaxial 3C-SiC (100) on Si(100) substrate

In this paper, the RF sputtering of polycrystalline AlN thin film on epitaxial 3C-SiC(100) on Si(100) substrate is presented. The effect of nitrogen concentration, deposition temperature and sputtering pressure are studied. These parameters are optimized to improve the crystal quality and deposition rate. Nitrogen concentration was varied from 40% to 100%, and it was found that the maximum deposition rate was observed at 40%. The RF bias power on substrate was also varied from 100 to 400 W, and it was observed that the deposition rate increases proportionally. The process temperature was varied from 200 to 400 °C to see the effect on the crystal quality and deposition rate; it was found that temperature variation does not yield significant shifts. This paper is able to demonstrate a successful RF sputtering of a polycrystalline AlN (100), (101), and (002) on epitaxial 3C-SiC(100) using RF power supply of 550 W.

Atomistic simulation of irradiation effects in GaN nanowires

We have studied effects of ion irradiation in GaN nanowires using classical molecular dynamics simulations. Nanowires with diameters of 3 and 4nm were irradiated with 100 Ar ions at energies of 100eV to 10keV corresponding to ion fluence of about 3×1014ions/cm2. The structure of the nanowires was analyzed along with sputtering yields and mechanical properties in the form of Young’s modulus. The results show a total sputtering yield of up to 8.3 sputtered atoms per ion and preferential sputtering of nitrogen with gallium to nitrogen ratio approximately 0.7. The Young’s modulus of the nanowires was observed to decrease as a function of the irradiation dose with the largest relative effect observed for ion energies of 1 and 10keV.

The influence of various sputtering parameters on structural, wettability and optical properties of Zr2ON2 thin films

Zirconium oxynitride films were deposited by reactive magnetron sputtering using helium as inert gas and oxygen and nitrogen as reactive gases. The effect of various sputtering parameters such as nitrogen flow rate, deposition time and sputtering pressure on structural, wettability and optical properties of zirconium oxynitride films is investigated. The X-ray diffraction graphs shows formation of well crystalline gamma phase of zirconium oxynitride with various textures at different nitrogen flow rate and deposition time, whereas variation of sputtering pressure shows decline in evolution of different textures for gamma phase of zirconium oxynitride and evolution of zirconia phase. The wettability determined by contact angle measuring system indicates that zirconium oxynitride films are hydrophobic. The increase in surface energies was observed with decline in contact angle values. The decline in band gap values was observed for zirconium oxynitride films deposited at various nitrogen flow rate (3.22–2.96 eV) and deposition time (2.91–2.77 eV).

The parameter space of hydrogen content added to Ar–nitrogen sputtering gas and substrate bias voltage for the formation of cubic boron nitride thin film deposited by unbalanced magnetron sputtering method

The parameter space for the formation of cubic phase of boron nitride thin films as a function of substrate bias voltage and hydrogen content added to Ar–N2 reactive sputtering gas was proposed. Cubic boron nitride (c-BN) films were deposited by unbalanced magnetron sputtering (UBM) method. Thin (100μm) Si strips (3×40mm2) were used as substrates. A boron nitride target was used, which was connected to a radio frequency (RF) power supply set at 400W. High frequency power connected to a substrate holder was used for self-biasing of up to −110V. The deposition pressure was 0.27Pa with a flow of Ar (18sccm) — N2 (2sccm) mixed gas irrespective of hydrogen addition. Hydrogen gas up to 16sccm was added to the Ar–N2 mixed gas. The addition of hydrogen tended to decrease the threshold substrate bias voltage for c-BN formation. Even under low bias voltage, where only hexagonal boron nitride (h-BN) formed under the Ar–N2 gas atmosphere, c-BN began to form with the addition of hydrogen to the gas. The surface of the film was very flat irrespective of the amount of added hydrogen. The deposition rate reduced with increasing hydrogen content. The residual stress decreased to 2GPa with a hydrogen flow of 10sccm, while maintaining the c-BN fraction in the film above 60%. The role of the hydrogen during the c-BN formation was briefly discussed.

Study on the Corrosion Resistance of ZrN Films on the Aluminium Alloys Surface

Aluminum alloy have the active chemical properties,low standard electrode potential, and the surface will be easily forming about 1-3nm oxide film in dry air, therefore aluminum alloy have the poor corrosion resistance.ZrN film deposited by mid frequency reactive magnetron sputtering process on aluminium alloy surface in order to improve the corrosion performance. Study the influences of nitrogen flow rate, sputtering time and temperature to the corrosion performance. The results show that: The corrosion performance of ZrN films will be improved with the nitrogen flow rate increase,but when the nitrogen flow rate was more than 18sccm, ZrN film corrosion resistance will be reduce;The corrosion performance improved with the sputtering time increase,when the time reach 15min, ZrN film corrosion resistance was no longer increase;The corrosion performance improved with the temperature, when the temperature reach 130°C, the corrosion resistance was no longer increase.The best process parameters was: nitrogen flow rate 18sccm, sputtering time 15min, temperature 130°C.