Energetic Nitrogen Ions Research Articles

Dose-dependent milling efficiencies of helium and nitrogen beams in PMMA

Focused ion beams with varied exposure dose were used to mill rectangular trenches into PMMA on SiO2. The dose response was investigated by atomic force microscopy measurements. TRIM calculations were used to simulate the ion distributions and damages expected inside the target. The depth of the trenches measured by AFM showed an unexpected decrease for intermediate dosages of high energetic helium ions in contrast to low energetic helium and nitrogen ions. This has been attributed to the formation of metastable blisters in the PMMA layer.

The Surface Treatment of Niobium Superconducting Reentrant Cavities by Means of High Temperature Nitrogen Plasma Based Ion Implantation

High Temperature Nitrogen Plasma Based Ion Implantation (HT-NPBII) has been used to treat the surface of niobium superconducting reentrant cavities, which are part of parametric transducers in a resonant-mass gravitational wave detector. The aim is to enhance the corresponding electrical quality factors (Q-factors) which are closely related with the increase of the sensitivity of the system. In this experiment, the cavities are immersed in plasma and bombarded by energetic nitrogen ions, which are implanted into the surfaces of these heated substrates. The heating temperature of the cavities is controlled during the treatment and its level directly affects the N implantation depth profile due to the diffusion process. Additional tailoring of the nitrogen doping can be performed by the adjustment of the intensity and the duty cycle of the high negative voltage pulses used for ion implantation. For implantations performed at 5 kV /20 µs /300 Hz/ 700 °C, nitrogen atoms occupy interstitial spaces in the crystal lattice of niobium. The treatment of niobium superconducting cavities under these parameters caused the enhancement of two orders of magnitude of respective Q-factors. A set of characterization techniques was performed herein in order to help with the understanding of the underlying mechanism behind this phenomenon.

An Overview on the Formation and Processing of Nitrogen-Vacancy Photonic Centers in Diamond by Ion Implantation

Nitrogen-vacancy (NV) in diamond possesses unique properties for the realization of novel quantum devices. Among the possibilities in the solid state, a NV defect center in diamond stands out for its robustness—its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. In this paper, we illustrated the formation kinetics of NV centers in diamond and their transformation from one charge state to another. The controlled scaling of diamond NV center-based quantum registers relies on the ability to position NV defect centers with high spatial resolution. Ion irradiation technique is widely used to control the spatial distribution of NV defect centers in diamond. This is addressed in terms of energetics and kinetics in this paper. We also highlighted important factors, such as ion struggling, ion channeling, and surface charging, etc. These factors should be considered while implanting energetic nitrogen ions on diamond. Based on observations of the microscopic structure after implantation, we further discussed post-annealing treatment to heal the damage produced during the ion irradiation process. This article shows that the ion implantation technique can be used more efficiently for controlled and efficient generation of NV color centers in diamond, which will open up new possibilities in the field of novel electronics and computational engineering, including the art of quantum cryptography, data science, and spintronics.

Influence of plasma process on the nitrogen configuration in graphene

We investigated nitrogen doping into graphene on copper substrates by plasma treatment and by plasma immersion ion implantation (PIII). Two nitrogen bonding configurations were discovered to be dominant for distinct plasma processes. Pyridinic-N (P1) was the preferential N-bonding for doping with PIII while it was pyrrolic-N (P2) for plasma treatment. The ratio of pyrrolic-N and pyridinic-N bonding (P2/P1) in N-doped graphene obtained from our experiments was associated with the simulated ratio of divacancy and monovacancy defect. Vacancy defect species induced by plasma in graphene play a key role to determine preferential N-bonding. Energetic nitrogen ions can stimulate the conversion of pyrrolic-N to pyridinic-N bonding via thermal spike, which leads to the decrease of the P2/P1 ratios when exposing graphene to nitrogen ions by either prolonging implantation or increasing implantation energy.

Origin of surface electron accumulation and fermi level pinning in low energy ion induced InN/GaN heterostructure

InN/GaN heterostructure was fabricated via reactive low energetic Nitrogen ion (LENI at 300 eV) bombardment at lower substrate temperature (350 °C). X-Ray Photoemission spectroscopic (XPS) and Atomic Force Microscopic (AFM) measurements were performed to analyse the electronic structure, surface chemistry, band alignment, and the morphology of the grown heterostructure. XPS analysis revealed the evolution of InN structure with nitridation time, surface electron accumulation, fermi level pinning and the band offset of the grown InN/GaN hetero structure. The valence band and conduction band offsets (VBO & CBO) were calculated to be 0.49 ± 0.19 eV and 2.21 ± 0.1 eV and divulged the formation of a type-I heterojunction. A Fermi Level (FL) pinning of 1.5 ± 0.1 eV above the conduction band minima was perceived and indicated towards strong downward band bending. The analysis of the VB spectra suggested that surface electron accumulation occurred due to the presence of metallic In-adlayer on the surface which resulted in FL pinning and the corresponding downward band bending. Atomic Force Microscopy analysis divulged the formation of smooth surface with granular structure. It was also observed that the growth parameters (e.g. substrate temperature) strongly influence the aforementioned surface and interfacial properties.

Plasma–wall interactions with nitrogen seeding in all-metal fusion devices: Formation of nitrides and ammonia

Nitrogen is routinely used to control the power load to the divertor targets of tokamak fusion reactors. However, its chemical reactivity can have implications on design and operation of a fusion device. In this contribution experimental results from recent years on three topics are briefly presented. These are the formation of nitrides, the sputtering of beryllium in the presence of nitrogen and the production of ammonia. Laboratory experiments have shown that surface nitrides are formed both on beryllium and tungsten upon exposure to energetic nitrogen ions. Erosion rates of Be by energetic N ions are in good quantitative agreement with modeling. Erosion upon exposure of Be to a mixed N/D plasma is reduced with respect to a pure D plasma. Finally, the appearance of ammonia has been observed in mixed N/D plasmas as well as in the exhaust gas of AUG and JET. The production rate in AUG reached 5% of the injected N atoms in a series of three subsequent N2-seeded discharges.

On the synthesis of a compound with positive enthalpy of formation: Zinc-blende-like RuN thin films obtained by rf-magnetron sputtering

4d- and 5d-transition metal nitrides are of interest both because of their importance for the understanding of mechanisms of phase formation in systems that under ambient conditions present positive enthalpies of formation and because of their appealing structural and electronic properties. In this study, we report the synthesis of thin films of ruthenium mononitride (RuN) in the zinc-blende structure by radio-frequency-magnetron sputtering. Films present a characteristic structure of packed columns ending with tetrahedral tips. The effect of changing the synthesis parameters was investigated in detail. It was found that RuN can be formed if the nitrogen partial pressure exceeds a minimum value and that the addition of argon has the major effect of increasing the deposition rate because of its higher sputter ability. Temperature plays an important role: if it is too high, decomposition/desorption effects overcome those leading to the formation of the compound. Phenomena resulting in the formation of RuN occur at the surface of the growing films and are related to the interactions of ruthenium with energetic nitrogen ions, or atoms, which can penetrate the first atomic layers by low energy implantation. Because of its properties and structure, this material is a promising candidate for applications like sensing, catalysis, and electrode material for energy-storage devices.

Development of vertical compact ion implanter for gemstones applications

Abstract Ion implantation technique was applied as an effective non-toxic treatment of the local Thai natural corundum including sapphires and rubies for the enhancement of essential qualities of the gemstones. Energetic oxygen and nitrogen ions in keV range of various fluences were implanted into the precious stones. It has been thoroughly proved that ion implantation can definitely modify the gems to desirable colors together with changing their color distribution, transparency and luster properties. These modifications lead to the improvement in quality of the natural corundum and thus its market value. Possible mechanisms of these modifications have been proposed. The main causes could be the changes in oxidation states of impurities of transition metals, induction of charge transfer from one metal cation to another and the production of color centers. For these purposes, an ion implanter of the kind that is traditionally used in semiconductor wafer fabrication had already been successfully applied for the ion beam bombardment of natural corundum. However, it is not practical for implanting the irregular shape and size of gem samples, and too costly to be economically accepted by the gem and jewelry industry. Accordingly, a specialized ion implanter has been requested by the gem traders. We have succeeded in developing a prototype high-current vertical compact ion implanter only 1.36 m long, from ion source to irradiation chamber, for these purposes. It has been proved to be very effective for corundum, for example, color improvement of blue sapphire, induction of violet sapphire from low value pink sapphire, and amelioration of lead-glass-filled rubies. Details of the implanter and recent implantation results are presented.

Band alignment and Schottky behaviour of InN/GaN heterostructure grown by low-temperature low-energy nitrogen ion bombardment

InN/GaN heterostructure based Schottky diodes are fabricated by low energetic nitrogen ions at 300 °C.

Role of Ion Beam Irradiation and Annealing Effect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple (5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×1019 m−3 to 1.3×1019 m−3, respectively. Moreover, the effect of continuous annealing (473 K and 523 K) on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray diffraction (XRD) patterns with increasing focus shots are: (i) variation in the crystallinity of AlN along (111), (200) and (311) planes, (ii) increasing average crystallite size of AlN (111) plane, and (iii) stress relaxation observed in AlN (111) and (200) planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened diffraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. Raman and Fourier transform infrared spectroscopy (FTIR) analysis confirm the presence of AlN and Al2O3 for the surface layer annealed at 473 K temperature. Raman analysis shows that the overlapping of AlN and Al2O3 results in the development of residual stresses. Scanning electron microscope (SEM) results demonstrate that the formation of rounded grains (range from 20 nm to 200 nm) and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.

Effect for hydrogen, nitrogen, phosphorous, and argon ions irradiation on ZnO NWs

Zinc oxide (ZnO) nanowires (NWs) are exposed to energetic proton (H+), nitrogen (N+), phosphorus (P+), and argon (Ar+) ions to understand the radiation hardness and structural changes induced by these irradiations. High-resolution transmission electron microscopy is utilized to see the irradiation effects in NWs. Multiple doses and energies of radiation at different temperatures are used for different set of samples. The study reveals that wurtzite (crystalline)-structured ZnO NWs experience amorphization, degradation, and morphological changes after the irradiation. At room temperature, deterioration of the crystalline structure is observed under high fluence of H+, N+, and P+ ions. While for ZnO NWs, bombarded by Ar+ and P+ ions, nano-holes are produced. The ZnO NWs surfaces also show corrugated morphology full of nano-humps when irradiated by Ar+ ions at 400 °C. The corrugated surface could serve as tight-holding interface when interconnecting it with other NWs/nanotubes. These nano-humps may have the function of increasing the surface for surface-oriented sensing applications in the future.

The effect of nitrogen ion bombarding energy on the bonding structure of nitrogenated tetrahedral amorphous carbon film

The tetrahedral amorphous carbon (ta-C) films with more than 80% sp3 in fraction are deposited by the filtered cathode vacuum arc technique. Then the energetic nitrogen (N) ions are used to bombard the ta-C films to fabricate nitrogenated tetrahedral amorphous carbon (ta-C:N) films. The composition and the structure of the films are analyzed by visible Raman spectrum and X-ray photoelectron spectroscopy. The result shows that the bombardment of energetic nitrogen ions can form CN bonds, convert CC bonds into C＝C bonds, and increase the size of sp2 cluster. The CN bonds are composed of C＝N bonds and CN bonds. The content of C＝N bonds increases with the N ion bombardment energy increasing, but the content of CN bonds is inversely proportional to the increase of nitrogen ion energy. In addition, CN bonds do not exist in the films.

Increasing of Hardness of Titanium Using Energetic Nitrogen Ions from Sahand as a Filippov Type Plasma Focus Facility

In this paper a 90 kJ plasma focus facility was used to the bombardment of the titanium substrate using nitrogen ion beams. From x-ray diffraction patterns, we investigated the structure properties of titanium nitride layer has been successfully deposited on the titanium substrate such as grain size microstrain and dislocation density. In this work we observed the growth of in grain size with increasing a number of deposition shots. Decrease in dislocation density and microstrain at higher deposition is the another results we observed in this work. The topography and morphology of TiN samples was studied by scanning electron microscopy (SEM) and optical microscopy images. From SEM micrograph, damage of surface and creation of pits and cracks was reported. The goniometric test indicate increasing in contact angle of water drop for irradiated samples in respect to the unirradiated samples. The Knoop microhardness of the samples is increased about 500%. With increasing of nitrogen ion flux, the microhardness increases.

Synthesis and structure of nitrogenated tetrahedral amorphous carbon films prepared by nitrogen ion bombardment

The tetrahedral amorphous carbon (ta-C) films with more than 80% sp 3 fraction firstly were deposited by filtered cathode vacuum arc (FCVA) technique. Then the energetic nitrogen (N) ion was used to bombard the ta-C films to fabricate nitrogenated tetrahedral amorphous carbon (ta-C:N) films. The composition and structure of the films were analyzed by visible Raman spectrum and X-ray photoelectron spectroscopy (XPS). The result shows that the bombardment of energetic nitrogen ions can induce the formation of CN bonds, the conversion of C–C bonds to C C bonds, and the increase of size of sp 2 cluster. The CN bonds are made of C N bonds and C–N bonds. The content of C N bonds increases with the increment of N ion bombardment energy, but the content of C–N bonds is inversely proportional to the increment of nitrogen ion energy. In addition, C≡N bonds are not existed in the films. By the investigation of AFM (atom force microscopy), the RMS (root mean square) of surface roughness of the ta-C film is about 0.21 nm. When the bombarding energy of N ion is 1000 eV, the RMS of surface roughness of the ta-C:N film decreases from 0.21 to 0.18 nm. But along with the increment of the N ion energy ranging from 1400 to 2200 eV again, the RMS of surface roughness of the ta-C:N film increases from 0.19 to 0.33 nm.

Properties of nitrogen-implanted beryllium and its interaction with energetic deuterium

Recent successful experiments with nitrogen as a seeding gas in fusion plasma devices, together with the decision to use beryllium as an armor material in the international fusion experiment ITER, have triggered interest in interactions of energetic N ions with Be and the influence of possible compound formation on parameters relevant to reactor operation and safety. Laboratory experiments are performed to investigate the properties of the ‘mixed material’ formed upon bombardment of bulk Be with energetic (keV) nitrogen ions. The formation of beryllium nitride within the implantation zone of a few nanometres is observed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Upon implantation of N at 1.5 keV per atom, saturation of the Be surface with N occurs at a fluence of 2 × 1018 N cm−2 and a retained areal density of approximately 4 × 1016 N cm−2. The nitride undergoes an ordering process upon annealing, but does not decompose at temperatures up to 1000 K. The influence of such nitride layers on the retention and release of D implanted with different fluences is investigated by nuclear reaction analysis and temperature-programmed desorption. The nitride layer does not act as a diffusion barrier for out-diffusing hydrogen isotopes. A partial sputter yield of 0.013 N/D as a lower limit is measured upon bombardment of the nitride layer with D at 2 keV. These erosion measurements are influenced by the strong tendency of the nitride to oxidize.

Dense plasma focus ion-based titanium nitride coating on titanium

We report the synthesis of titanium nitride coating on a titanium substrate by utilizing energetic nitrogen ions emitted from a 2.3kJ dense plasma focus device for 30 focus shots. The number of nitrogen ions transferred to the sample by a single ion pulse of about 140ns duration in the energy interval (40–600keV) is about 1.09×1012 with a mean energy per ion of 58keV. The corresponding energy flux delivered to the titanium surface is estimated to be 6.17×1014keVcm−3ns−1 leading to a transient temperature rise of the top layer of about 5400K which helps layer growth. The coating is investigated on the basis of its morphological, compositional and hardness properties. X-ray diffraction analysis of the sample reveals the formation of a nanocrystalline titanium nitride coating having (111) and (200) plane reflections with an average crystallite size of 40nm. The compressive residual stresses in the nitride coating have been evaluated to be 2.80GPa and 6.81GPa corresponding to (111) and (200) plane orientations. A complete restructuring of the manually polished titanium substrate has been observed with appearance of nano-sized multidimensional granular surface morphologies. The thickness of the nitride coating is about 1μm, whereas the coating has a nitrogen content of 35.35at.% and 13.78±3.57wt.% and a surface hardness of 8.19GPa.

Carbonitriding of silicon using plasma focus device

Carbonitride thin films have been deposited on silicon substrate by the irradiation of energetic nitrogen ions emanated from dense plasma focus device. The carbon ions are ablated by the irradiation of relativistic electrons from the insert material (graphite) placed at the anode tip. The x-ray diffraction analysis demonstrates that a polycrystalline thin film consisting of various compounds such as Si3N4, SiC, and C3N4 is formed on the silicon (100) substrate. Crystallinity of different compounds decreases with the increase in angular positions (0°, 10°, and 20°). Raman spectroscopy shows the appearance of graphitic and disordered bands with silicon nitride and silicon carbide indicating the formation of carbonitride. Raman spectra also indicate that broadening of bands increases with the increase in focus deposition shots, leading to the amorphization of the thin film. The amorphization of the thin films depends on the ion energy flux as well as on the sample angular position. The scanning electron microscopy exhibits the damaging of the substrate surface at 0° angular position. The microstructure shows the tubular shape for higher ion dose (40 focus shots). At 10° angular position, a two phase phenomenon is observed with the ordered phase in the solid solution. A smooth and uniform surface morphology showing a small cluster is observed for the 20° angular position.

Synthesis of nano-crystalline zirconium aluminium oxynitride (ZrAlON) composite films by dense plasma Focus device

Zirconium aluminium oxynitride multiphase composite film is deposited on zirconium substrate using energetic nitrogen ions delivered from dense plasma Focus device. X-ray diffractometer (XRD) results show that five Focus shots are sufficient to initiate the nucleation of ZrN and Al 2O 3 whereas 10 Focus shots are sufficient to initiate the nucleation of AlN. XRD results reveal that crystal growth of nitrides/oxides increases by increasing Focus shots (up to 30 Focus shots) and resputtering of the previously deposited film is taken place by further increase in Focus shots (40 Focus shots). Scanning electron microscopic (SEM) results indicate the uniform distribution of spherical grains (∼35 nm). A smoother surface is observed for 20 Focus shots at 0° angular position. SEM results also show a net-type microstructure (thread like features) of the sample treated for 30 Focus shots whereas rough surface morphology is observed for 40 Focus shots. Energy dispersive spectroscopic profiles show the distribution of different elements present in the deposited composite films. A typical microhardness value of the deposited composite films is 5255 ± 10 MPa for 10 grams imposed load which is 3.3 times than the microhardness values of unexposed sample. The microhardness values of the exposed samples increases with increasing Focus shots (up to 30 Focus shots) and decreases for 40 Focus shots treatment due to resputtering of the previously deposited composite film. The microhardness values of the composite films decreases by increasing the sample's angular position.

Nitridation of zirconium using energetic ions from plasma focus device

The nitridation of zirconium disks is achieved by irradiating energetic nitrogen ions from 2.3 kJ plasma focus device using multiple focus deposition shots (10, 20, 30 and 40) at different angular positions with respect to the anode axis. The X-ray diffraction analysis reveals the evolution of ZrN, Zr 2N and Zr 3N 4 phases of zirconium nitride depending upon the ion energy flux and angular positions. The crystallite size of ZrN and Zr 2N phases increases by increasing the number of focus deposition shots. The residual stresses estimated for Zr (101), ZrN (111) and ZrN (200) phases are maximum in the nitrided surfaces at lower nitrogen ion dose, decreases as the nitrogen ion dose increases. The field emission scanning electron microscopy results exhibit the uniform and smooth film of zirconium nitride with granular surface morphology at 10° angular position. The energy dispersive X-rays spectroscopy data indicate that nitrogen content in the film is improved for higher nitrogen ion dose while reduced at larger angular positions. The Vickers microhardness of the film is enhanced up to 400%. The microhardness increases by increasing the nitrogen ion dose and decreases rapidly by increasing the angular position.

Depth Selective Electronic State Analysis of Implanted Nitrogen in Visible-Light Response TiO<sub>2</sub> Photocatalyst

Energetic nitrogen ion was injected into a TiO2 photocatalyst in order to investigate the optimal local concentration of doped nitrogen for visible-light response. N+-implanted TiO2 samples promoted the photocatalytic activity under visible-light irradiation. N K-edge XANES of the highest activity sample indicated that N replaces the O sites near the surface, whereas in the samples of higher N+ fluence, N−O and/or N−N species formed. Depth-resolved N K-edge ELNES revealed the two types of N, depending on the concentration, and we found the local N concentration effective for visible-light response was less than ∼1 at%. Further, the spatial distributions of the different chemical states of N by energy-filtering TEM (FETEM) supported these findings.