Chemical States Of Nitrogen Research Articles

Chemical effect of inert argon beam on nitride nanolayer formed by ion implantation into GaAs surface

The composition of a nitride nanolayer formed on a GaAs(100) surface by the implantation of ions with an energy of E i = 2.5 keV and the chemical state of nitrogen in this layer have been studied by the method of Auger electron spectroscopy. It is established that, in addition to GaN, a GaAsN solid solution phase is formed in the ion-implanted layer. The energies of N KVV Auger electron transitions in these phases are determined as E A (GaN) = 379.8 ± 0.2 eV and E A (GaAsN) = 382.8 ± 0.2 eV (relative to the Fermi level), which allowed the distribution of nitrogen between these phases to be evaluated as [N(GaN)] = 70% and [N(GaAsN)] = 30%. It is established that an argon ion beam produces a chemical effect on the nitride layer, which is related to a cascade mixing of the material. Under the action of the argon ion bombardment, the distribution of nitrogen in the indicated phases changes to opposite. As a result a nitride nanolayer is formed in which the narrow-bandgap semiconductor (GaAsN) predominates rather than the wide-bandgap component (GaN).

XPS Study on Chemical State and Phase Structure of PBII Nitriding M50 Steel

X-ray diffraction (XRD) and X-ray photoelectron spectroscopy were used to study the structure and the element chemical states of plasma-based ion implantation (PBII) nitriding M50 steel. An ~70-nm-thick oxygen-rich layer was formed in the surface after PBII treatment, where C and V elements were absent, Cr and Mo elements were in the manner of oxide, and Fe element was in the manner of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and iron nitride. XRD patterns revealed that the Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> phase was formed in the subsurface of the nitrided layer. Four different chemical states of nitrogen with binding energies of 404.1, 399.2, 396.7, and 394.3 eV were found in sequence with sputtering time increasing, which were confirmed to belong to NO bonding, Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (N, O) [or Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (NO)], Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N (or Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> N), and Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> .

X-ray photoelectron spectroscopy study of Al- and N- co-doped p-type ZnO thin films

The chemical state of nitrogen, aluminum, oxygen and zinc in Al–N co-doped p-type ZnO thin films was investigated by X-ray photoelectron spectroscopy (XPS). N 1s peak were detected in both the two p-type ZnO thin films, showing two components. The higher binding energy peak may be due to the Al–N O–H species, and the lower one perhaps derive from the (NH 2) − cluster for the ammonia introduction. These two peaks both contribute to the p-type behavior in the ZnO films. A symmetry 74.4 eV binding energy in Al 2p3/2 photoelectron peaks revealed an Al–N bonding state, a key factor to the co-doping method.

Nitrogen-doped diamond film and its doping behavior

Nitrogen-doped diamond films were synthesized by electron assisted chemical vapor deposition.The quality and chemical state of nitrogen in the diamond films were characterized by SEM,Raman,XPS,and EPR.Results showed that the morphologies of the diamond films changed from integrated facets to the “cauliflower-like” diamond(100)faces,the amorphous carbon content increased and its quality dropped with increasing nitrogen flow rate.The chemical state of nitrogen in the diamond films was of the form Ns0,\[N-V\]0 and \[N-V\]-1.The amounts of \[N-V\]0 and \[N-V\]-1 were higher when the nitrogen flow rate was lower,and the mass fraction of Ns0 varied from 1.50×10-5 to 4.83×10-4.

Thermal stability of nitrogen-doped SrTiO3 films: Electronic and optical properties studies

The thermal stability of nitrogen-doped SrTiO3 (001) films in terms of electronic and optical properties has been studied by using x-ray photoemission spectroscopy, x-ray absorption spectroscopy, and spectroscopic ellipsometry techniques. The chemical states of nitrogen in nitrogen-doped SrTiO3 films include both substitutional and interstitial states. The N 2p states localized above the O 2p-derived valence band maximum are attributed to the change of optical properties. Postannealing will induce the valence band edge shift due to the thermal instability of interstitial N states, which may degrade the photocatalysis of nitrogen-doped SrTiO3 films during applications.

Chemical states of nitrogen in ZnO studied by near-edge X-ray absorption fine structure and core-level photoemission spectroscopies

Interaction of low-energy nitrogen ions with ZnO surface has been studied by photoemission spectroscopy (PES) around N 1s core-level and near-edge X-ray absorption fine structure (NEXAFS) around N K-edge. Nitrogen can break Zn–O bonds at the surface and form N–O, Zn–N or Zn–N–O bonds, characterised by specific chemical shifts in PES or absorption peaks in NEXAFS. A distinctive signal from molecular nitrogen has also been observed in ion-bombarded samples in both NEXAFS and PES.

Interaction of ZDDP with Borated Dispersant Using XANES and XPS

The thermochemical reaction and tribochemical reaction of zinc dialkyldithiophosphate (ZDDP), a borated dispersant, and the mixture of ZDDP and borated dispersant on steel surfaces were investigated. Both pin-on-disk and ball-on-disk were used to generate tribofilms. The chemical state of nitrogen, boron, phosphorus, and sulfur in heated oil solutions, thermal films, and tribofilms were analyzed by X-ray absorption near edge structure (XANES) spectroscopy to obtain the chemical nature of species on the surface and in the bulk of the films. High-resolution X-ray photoelectron spectroscopy (XPS) has also been used to analyze boron (B) in tribofilms.The borated dispersant in base oil by itself yields good anti-wear behavior. This can be attributed to the presence of boron in the dispersant. The wear scar widths (WSW) for ZDDP alone, and in combination with the dispersant, yield similar results within the experimental error. It was found that the borated dispersant facilitates the decomposition of ZDDP and the formation of phosphate in tribofilms and thermal films. B K-edge XANES shows that boron has a trigonal coordination in the untreated additive, but the coordination changes partially to a tetrahedral coordination in the tribofilm upon rubbing. No BN was detected in the film analyzed by B K-edge or N K-edge. Boron 1s XPS also did not show the presence of BN in the film.

Chemical state of nitrogen in a high nitrogen face-centered-cubic phase formed on plasma source ion nitrided austenitic stainless steel

A single high nitrogen face-centered-cubic phase (γN) was formed on the plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel. Auger electron spectroscopy and x-ray photoelectron spectroscopy, in conjuction with ion beam sputtering, were used to determine the chemical composition and bonding of nitrogen in the γN phase. The chemical composition of the γN phase was shown as a formula with atomic fraction (Fe0.60,Cr0.22,Ni0.18)2N. The γN phase possessed weaker Cr–N ionic-type bonds and stronger Fe–N ionic-type bonds, compared with the stoichiometric nitrides. The Cr2p3∕2 binding energy was 1.1eV lower than that of CrN and Cr2N phases (at 575.5eV). The chemical shift of the Fe–N bonding compared with the Fe–Fe bonding was nearly 2.1eV. The N1s binding energies showed that the nitrogen was in the chemical state with iron (at 396.6eV) and chromium (at 397.7eV). All the chromium appeared to be in the Cr–N bond. A part of iron was also observed in the nitride state, and all the nickel was contained in the metallic state.

Deposition and electrical properties of N–In codoped p-type ZnO films by ultrasonic spray pyrolysis

The N–In codoped p-type ZnO films have been prepared by ultrasonic spray pyrolysis. X-ray photoelectron spectroscopy analysis confirmed the presence of nitrogen and indium in the codoped films, and the incorporation of indium causes the change in the chemical state of nitrogen, which promotes the formation of p-type conduction. Low resistivity of 1.7×10−2 Ω cm, high carrier concentration of 2.44×1018 cm−3 and Hall mobility of 155 cm2 V−1 s−1 at room temperature for the codoped films were obtained. A conversion from p-type conduction to n type in a range of temperature has been identified by the measurement of Seebeck and Hall effect.

Non-destructive probing of interfacial oxidation and nitridation states at RTP Si-oxides

The quality of the SiO 2/Si interface is of crucial importance in the development and performance of sub 0.1 μm technologies. The knowledge of the chemical composition of the interface is an important piece of information in the preparation of ultra-thin oxides and high-k dielectrics, in order to maintain a high-quality interface and channel mobility. Here we report on investigations of 2 nm oxide layers formed by a RTP process under various gas mixtures containing N 2O and NH 3 at different concentrations. We studied the SiO 2/Si(001) interface by a non-destructive depth profiling using Synchrotron radiation photoelectron spectroscopy. We determine the thickness of the oxide layer, the relative content and chemical state of nitrogen within the oxide, the thickness of the interface layer, and the relative abundance of Si intermediate oxides within. In all systems we find the thickness of the intermediate layer to be approximately 0.17 nm. The intermediate layer contains Si atoms in the oxidation states +1, +2 and +3 with similar relative abundance. Nitrogen is found predominantly close to the intermediate layer forming SiN as well as SiNO bonds. Within the oxide there are only spurious nitrogen content with predominately SiNO bonds. Our method is able to detect a nitrogen content within the intermediate layer as low as approximately 5%.

Surface chemical changes induced by low‐energy ion bombardment in chromium nitride layers

AbstractIn this work three types of CrNx layers—one close to Cr2N, the other to CrN and a third with high nitrogen content CrN1+x—were prepared by reactive magnetron sputtering. The samples were subjected to bombardment by Ar+ and N2+ ions applied in sequence. The relative atomic concentration and the chemical states of the elements in the surface layer were determined by x‐ray photoelectron spectroscopy. Alternate bombardment with Ar+ and N2+ ions (1–2 keV) resulted in significant compositional and chemical state changes. Although prolonged Ar+ bombardment did not decrease the nitrogen content of Cr2N below the nominal (CrN0.5) composition, it decreased the nitrogen content of the closely stoichiometric CrN appreciably, to about CrN0.8. At bombardment with N2+ ions nitrogen could be implanted into the Cr2N films, changing its composition up to about CrN0.8. It was shown that extra nitrogen could be incorporated also into the CrN samples, increasing the nitrogen content above the stoichiometric composition up to about CrN1.2. The CrN1+x‐type sample showed high stability towards Ar+ bombardment. Two significantly different chemical states of nitrogen were determined for the two types of nitrides: the N 1s peak at 397.5 ± 0.1 eV binding energy was characteristic of N in Cr2N and the peak at 396.5 ± 0.1 eV of N in the CrN state. The effect of Ar+ and N2+ bombardment on the surface composition discussed in this paper may provide information for elaboration of deposition conditions for CrNx coatings with predetermined chemical composition and structure. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Target surface condition during reactive glow discharge sputtering of copper

During reactive glow discharge sputtering of copper in an argon/nitrogen plasma, we noticed an abrupt change of the target voltage and the deposition rate when the nitrogen concentration in the plasma exceeds a critical value. To explain this behaviour, the target surface after reactive glow discharge sputtering was examined by x-ray photoelectronspectroscopy (XPS). An experimental arrangement was constructed that allows direct transfer of the glow discharge cathode to the XPS analysis chamber without air exposure. These XPS measurements revealed that several different chemical states of nitrogen are present in the layer that forms on the target surface. The relative concentration of these different states changes when the critical nitrogen concentration in the plasma is exceeded.

Impact of Nitrogen Profile in Gate Oxynitride on Complementary Metal Oxide Semiconductor Characteristics

We demonstrated that the control of the nitrogen profile in the gate oxynitride for complementary metal oxide semiconductors (CMOSs) is very important. We grew NO or N2O nitrided gate oxide at 800°C or 900°C to prepare three kinds of oxynitrides with different nitrogen profiles, and investigated the atomic configuration and the chemical state of nitrogen using secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. Furthermore, we fabricated CMOS field effect transistors with gate oxide and oxynitride, and evaluated the interface state density and the hot carrier immunity. By systematical investigation of the relationship between the nitrogen profile and the electrical characteristics, we found that the nitrogen in the oxynitride should exist only at the interface for realizing the CMOS devices having high performance and high reliability.

Distribution of Ion-Implanted Nitrogen in Iron Alloys Investigated by AES

The depth distribution and the lateral distribution of nitrogen after implantation by means of plasma immersion ion implantation (PIII) in ferritic alloys with 0.3 wt.-% Al and 3.6 wt.-% Cr has been studied by scanning Auger electron spectrometry (AES). To get information about the chemical state of nitrogen and to improve the detection limit methods of data analysis (factor analysis, LLS) have been applied to depth and line profiles, respectively. Thereby the detection limit for nitrogen was reduced from 6% to 1%. The nitrogen distribution is laterally homogeneous in the near surface region only. Depth profiles obtained at several points within the sputter crater showed that the in-depth distribution of nitrogen varies markedly between different points on the sample and from sample to sample. The nitrogen concentration in the implantation maximum corresponds to Fe2N1−x (x ≈ 0.04 0.18). A remarkable feature are grains having a 10 μm wide seam rich in N and a nearly nitrogen-free grain’s interior. The N/Fe ratio determined from line profiles show that the outer layer of the grains has almost the exact composition Fe4N and the transition to the nearly nitrogen-free grain's interior (cN ≤ 1%) occurs within 1 4 μm. The same shape of the N(KLL) peak was found in depth profiles and line scans, respectively, and it corresponds to gasnitrided samples γ ′–Fe4N and ɛ–Fe2N1−x.

Denitrogenation behavior and tensile strength increase during carbonization of stabilized pan fibers

Carbonization of stabilized PAN fibers was studied by focusing nitrogen using elemental analysis and XPS, in relation to mechanical properties. A difference in denitrogenation on the surface and in the bulk of the fibers was observed in a range of carbonization temperatures between 600 and 1000°C, with denitrogenation on the surface occurring much earlier (600–800°C) than in the bulk (>800°C). The chemical state of nitrogen seemed to be different between the surface and the core; more tertiary nitrogen (– N | –) was present at the surface than in the core in a temperature range between 600 and 1000°C. This difference might be responsible for the retardation in the tensile strength development of the fibers while increasing the HTT from 700 to 800°C.

The role of nitrogen in the passivity of austenitic stainless steels

Three austenitic stainless steels (a Fe-17Cr-13Ni-0.15N alloy, an ultra pure Fe-18Cr-10Ni alloy and a type 304 stainless steel) were used in this study in order to investigate the effect of nitrogen on the electrochemical behaviour and on the nature of the passive film formed on the steels in acidic solution (0.5 M H 2SO 4). The presence of nitrogen in the alloy does not apparently have a significant influence on the response of the material to anodic polarization in the acid electrolyte. Surface analysis of the alloys by XPS after passivation shows that nitrogen is enriched at the surface by anodic segregation during dissolution and passivation of the nitrogen-bearing alloys. After passivation of the alloys three chemical states of nitrogen are detected in the N 1s spectrum. The peak at low binding energy (397.7 ± 0.1 eV) corresponds to nitrogen bonded essentially to chromium under the form of a nitride which is incorporated in the passive film. The N 1s peaks observed at higher binding energies (400.2 ± 0.1 and 402 ± 0.1 eV) correspond to nitrogen species located on the surface of the passivated alloys, which are produced by reaction of the alloy surface with the solution.

XPS study of the passive films formed on nitrogen-implanted austenitic stainless steels

Austenitic stainless steels (304-type) have been implanted with nitrogen ions in order to investigate the effects of implanted nitrogen on their electrochemical behaviour and on the nature of the passive film formed on the steels in acid (0.5M H 2SO 4). Alloys with two nitrogen doses have been prepared (2.5×10 16 and 2×10 17 N atoms/cm 2). The implanted alloys have been characterized by 15NNRA (nuclear reaction analysis) and XPS (X-ray photoelectron spectroscopy). Alloy surfaces with well-defined N concentrations were prepared, prior to the electrochemical measurements, by argon-ion sputtering of the implanted material for a fixed time in order to reach a well-defined point on the nitrogen depth profile. The samples were then transferred without exposure to air to an electrochemical cell mounted in an inert gas glove box. The implanted nitrogen modifies the electrochemical behaviour of the alloy. The anodic dissolution in the active state is enhanced, and the current density in the passive state is increased. Surface analysis of the alloys by XPS after passivation shows that implanted nitrogen is enriched on the surface during dissolution and passivation of the alloys. The process by which N is enriched on the surface is anodic segregation, which was first observed and characterized for S on Ni and NiFe alloys [J. Oudar and P. Marcus, Appl. Surf. Sci. 3 (1979) 48: P. Marcus, A. Teissier and J. Oudar, Corros. Sci. 24 (1984) 259]. The passive films formed on both the unimplanted and implanted alloys have a bilayer structure with an inner oxide layer and an outer hydroxide layer, but on the nitrogen-implanted alloy, a chromium nitride phase is formed at the expense of the chromium oxide. After passivation of the implanted alloys, three chemical states of nitrogen are detected in the N 1s spectrum. The high binding energy (399.4 eV) peak corresponds to a nitrogen species located on the surface of the passive film, which is produced by reaction of the implanted nitrogen with the solution. The peak at low binding energy (396.3 eV) is assigned to nitrogen bonded essentially to chromium, under the form of a nitride, which is incorporated in the passive film. The peak at intermediate binding energy (397.0 eV) corresponds to implanted nitrogen in the alloy, and is detected because the passive film is very thin. The XPS measurements and the sputter depth profiles indicate that during the anodic segregation of N, the chromium-rich nitride which is formed is incorporated as islands in the passive film.

ESCA studies of nitrogen-containing stainless steels

ESCA examination of films formed on nitrogen-containing stainless steels after immersion in 0.1 M NaCl revealed that nitrogen was enriched in the outer 0.5 nm of the film at a concentration a few times higher than in the substrate. The N(1s) binding energy varied from 399.6–399.7 eV at the outermost surface of the film to 398.3–398.8 eV in the film at a depth of about 0.5 nm. This indicates a change in the chemical state of nitrogen upon exposure of the nitrogen-containing stainless steels to the solution, and furthermore, that the surface nitrogen enrichment could be of significance in the improved pitting resistance.

Three-dimensional X-ray microtomography: 37388 Flannery, B.P.; Deckman, H.W.; Roberge, W.G.; D'Amico, K.L. Science, Vol. 237, No. 4821, pp. 1439–1444 (18 Sep. 1987)

Multilayer graphene (MLGR) and its bulk analog, highly oriented pyrolytic graphite (HOPG), were treated by radio frequency activated low pressure N2 gas plasma (at negative bias 0–200 V, for 5–20 min). Surface composition and chemical-state alterations were delineated by X-ray photoelectron spectroscopy (XPS). Covalently bonded nitrogen of 5–15 at% incorporated into the surface. The higher N concentration in MLGR below 100 V is attributed to the larger number of defects. The equal N content at 200 V indicates intensive formation of reactive sites. In-depth distribution of N is restricted to 2–4 monolayers. Model calculation resulted in 23 at% N (at 100 V) in the top graphene layers of HOPG. Three different chemical states of nitrogen (pyridine-type at 398.3 eV, pyrrole- and triazine-type at 399.7 eV and N substituting C in graphite-like network at 400.9 eV) were determined from high-resolution N1s spectral region for all samples. Pyridine and pyrrole–triazine components increase preferentially with increasing bias. Alterations of the C1s and O1s spectra are discussed in a critical approach. The amount of reacted carbon was consistent with that required for the three different nitrogen and oxygen states, thus validating the proposed assignments.

On the chemical states of nitrogen on iron surfaces reacted with ammonia and sodium cyanide, studied by X-ray photoelectron spectroscopy

The reaction products of iron reacted with ammonia gas and molten sodium cyanide are studied using X-ray photoelectron spectroscopy. Ammonia gas dissociates on iron surfaces to form a nitride and a loosely bound NH 3-like species with N 1 s B.E.'s at 397.2 and 399.8 eV, respectively. On iron specimens dipped into molten NaCN three species are found at 398.6, 397.8 and 397.2 eV. The 398.6-eV peak is ascribed to adsorbed −CN, and the 397.8-eV peak to carbonitride formed by the reaction of the cyanide with iron. Decreasing binding energies are found for adsorbed −CN ligand, carbonitride compound and nitride, which seem to correspond to an apparent order of stronger interaction of nitrogen with iron. An iron sample was scratched with a file and the surface species of nitrogen were observed below 400°C. The nitrogen atoms in the sample diffuse and concentrate on the surface, depending on the nitrogen content in the bulk. Desorption patterns of nitrogen from a heated iron surface are examined with a view to the determination of gaseous constituents in metal samples.