Modification of polycarbonate surface by Ar ion implantation for various opto-electronic applications

The samples of polycarbonate were implanted to 100 keV Ar⁺ ions at fluences ranging from 1 × 10¹⁵ to 2 × 10¹⁶ ions/cm². The effect of ion implantation on DC conductivity and optical behaviour of this polymer has been investigated. The observed changes have been correlated with the induced structural changes in the implanted layer using Raman spectroscopy. The increase in electrical conductivity, decrease in UV-visible transmission and red shifting of the optical absorption edge may be due to the formation of a three dimensional carbonaceous structure having conjugated double bonds in the near surface layer of polycarbonate as a result of ion implantation. The shift in the conduction mechanism in the implanted layer from ohmic towards SCLC has been observed as a function of implantation dose. The novelty of the present study is to investigate the implantation induced electrical conduction mechanism in the implanted polycarbonate and to comprehend it with induced optical behaviour for its utilization as optically active material with conductive surface in various opto-electronic devices.     

Correlation between surface damage and micro-defects in Si covered with insulating layer by implantation of He and H ions

Cz n-type Si (100) wafers covered with a 220 nm SiO₂ layer or a 170 nm Si₃N₄ layer were singly implanted with 160 keV He ions at a dose of 5 × 10¹⁶/cm² or successively implanted with 160 keV He ions at a dose of 5 × 10¹⁶/cm² and 110 keV H ions at a dose of 1 × 10¹⁶/cm². Surface morphologies together with defect microstructures have been studied by means of several techniques, including optical microscopy, atomic force microscopy, and cross-sectional transmission electron microscopy (XTEM). Only surface blistering has been observed for He and H sequentially implanted SiO₂/Si samples after annealing in temperature range up to 1000 °C. However, as for the He and H implanted Si₃N₄/Si samples, surface features including blistering and the localized exfoliation of both the top Si₃N₄ layer and the implanted Si layer have been well demonstrated during subsequent annealing. XTEM observations reveal quite different defect morphologies in two kinds of materials under the same implantation and annealing conditions. The possible mechanisms of surface damage in two kinds of materials have been discussed and presented based on the XTEM results.     

Properties of implanted PET by W ion using MEVVA implantation

Polyethylene terephthalane (PET) has been modified with W ions from a metal vapour arc source (MEVVA). W ions were implanted at 136 keV to doses ranging from 5×10¹⁵ to 2×10¹⁷/cm². The surface of the implanted PET darkened with increasing ion dose, when the metal ion dose is greater than 1×10¹⁷ cm⁻² the colour changed to metallic bright. The surface resistance obviously decreases with increasing dose. The resistivity is stable after long-term storage. TEM photos revealed the presence of W nanometer particles on the surface resulting from the high does implantation. The depth of implanted layer is approximately between 180 and 100 nm for W-implanted PET to doses of 2×10¹⁷/cm² and 5×10¹⁶/cm², respectively. The conductivity and wear resistance have been improved significantly due to W ion implantation. It can be seen that nanometer particles of W precipitation, and carbides have been formed in the implanted layer. The nano-hardness of the implanted PET has been measured by a nano-indenter. The results show that the surface hardness, modulus and wear resistance could be increased.     

Wear resistance of TiN coatings implanted with Al and N ions

Titanium nitride (TiN) coatings were prepared on HS 6-5-2 high-speed steel cutting inserts and next implanted either with Al ions (fluence 2×10¹⁷ ions/cm²) or with Al and N ions (fluence (1+1)×10¹⁷ ions/cm²) on the rake face. Microhardness and friction coefficient of the implanted surfaces were examined. A noticeable increase of microhardness in Al implanted inserts has been observed.The elemental composition and structural properties of the surface layer were examined by glow discharge optical emission spectroscopy (GDOES) and gliding angle X-ray diffraction (XRD).The tests of turning of 40 H constructional steel with the cutting inserts have shown an improvement in the implanted inserts, especially marked in those implanted with Al+N.     

Influence of aluminum ions implanted on oxidation behavior of ZIRLO alloy at 500 °C

The beneficial effect of aluminum ion implantation on the oxidation behavior of ZIRLO alloy at 500 °C has been studied. ZIRLO alloy specimens were implanted with aluminum ions with fluence range from 1×10¹⁶ to 1×10¹⁸ ion/cm², using a MEVVA source at an extraction voltage of 40 kV at maximum temperature of 380 °C. The weight gain curves were measured after being oxidized in the air at 500 °C for 120 min, which showed that a significant improvement was achieved in the oxidation behavior of ZIRLO alloy implanted with aluminum compared with that of the virgin ZIRLO alloy. It has been obviously found that when the fluence is 1×10¹⁸ ion/cm², the oxidization of the implanted ZIRLO alloy is reduced into 30% of the virgin ZIRLO alloy.     

Magnetism in GaN layers implanted by La, Gd, Dy and Lu

We present a complex study of rare earth elements implanted GaN layers grown by low pressure metal-organic vapor phase epitaxy on c-plane sapphire substrates. Gd, Dy, La and Lu ions were implanted with energies of 200 keV and doses ranging from 5 × 10¹³ to 4 × 10¹⁷ atoms.cm^− 2. The chemical composition and concentration profiles of ion-implanted layers were studied by secondary ion mass spectrometry and Rutherford back scattering. The structural properties of the layers were characterized by Rutherford back scattering/channeling and X-ray diffraction reciprocal space mapping. Gd implanted layers exhibit ferromagnetic behavior persisting up to ~ 720 K. Since the ferromagnetic behavior was not observed in the case of La and Lu implanted layers, it cannot be attributed to the structural damage of the layer. Based on the fact that the samples are electrically conducting we conclude that the ferromagnetism can be associated with doped electrons mediating the ferromagnetic interaction between local moments on Gd and Dy.     

Effect of Si and He implantation in the formation of ultra shallow junctions in Si

He, Si and B implantation are successively combined in order to produce ultra shallow junctions (USJs). Si is implanted at 180 keV to create a ‘vacancy-rich’ layer. Such a layer is however followed by a deeper interstitial rich one. He implantation is performed at a dose high enough (5 × 10¹⁶ cm^− 2) to create a cavity layer in Si sample. Eventually, B is introduced by low energy ion implantation. Since cavities are known to be sinks for self-interstitials (Is), they might be able to decrease the transient enhanced diffusion (TED) of B during the dopant activation annealing in all processes investigated in this study. The samples are divided in two groups (named S1 and S2) to check the benefits of defect engineering of each implantation element. Hence, sample 1 is first implanted with He, followed by cavity formation annealing and second with B. Si implantation is performed on S2 after cavity formation, and followed by B implantation in the same condition as S1. All samples are characterized by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM) and Hall effect measurements. Results show that, in all cases, boron TED is suppressed while working with a cavity layer created before activation annealing. This layer acts as an Is barrier. Finally, an USJ with a low junction depth (X_j = (13 ± 1) nm, determined at 10¹⁸ cm^− 3 boron level) is successfully realized.     

Diffusion of Pb in carbon ion-implanted silicon: Discovery of a new crystalline phase after electron beam annealing

A novel phase has been discovered by dual low-energy ion implantation and high vacuum electron beam annealing. (100) p-type Si was implanted with (a) 20 keV ¹²C⁺ ions to the fluence of 6 × 10¹⁶ cm⁻² and (b) 7 keV Pb⁺ ions to the fluence of 4 × 10¹⁵ cm⁻². The ¹²C ion implantation results in an understoichiometric shallow SiC_x layer that intersects with the surface. The implanted Pb ions decorate a shallow subsurface region. High vacuum electron beam annealing at 1000 °C for 15 s using a temperature gradient of 5 °C s⁻¹ leads to the formation of large SiC nanocrystals on the surface with RBS measurements showing Pb has diffused into the deeper region affected by the ¹²C implantation. In this region, a new crystalline phase has been discovered by XRD measurements.     

Optical and structural properties of Mg-ion implanted GaN nanowires

Mg⁺ ions (60 keV) were implanted into GaN nanowires (NWs) with total fluxes of 5 × 10¹²-5 × 10¹⁴ cm⁻² followed by thermal annealing at 700 °C in N₂ ambient. Transmission electron microscopic images showed amorphous layer formation and defect accumulation in the higher dose Mg-implanted GaN NWs after annealing. Photoluminescence spectra (300 K) of the annealed Mg-implanted GaN NWs exhibited near-band-edge (NBE) emission, donor-acceptor pair (DAP) emission, and defect-related yellow luminescence. With increasing dose, the NBE and DAP emissions are red shifted. Similar phenomena were observed in samples implanted with Ar to produce similar amounts of lattice disorder. The NWs show a much higher sensitivity to defect accumulation than GaN thin films.     

Effect of Titanium ion implantation on the oxidation behaviour of zircalloy-4 at 500 °C

The beneficial effect of titanium ion implantation on the oxidation behaviour of zircalloy-4 at 500 °C was investigated. Titanium ions were implanted by a MEVVA source at an energy of 40 keV with dose 5×10¹⁶, 1×10¹⁷, and 2×10¹⁷ ion/cm² at the maximum temperature 130 °C. Weight gain curves of the as-received and implanted zircalloy-4 were measured after oxidation in air at 500 °C for 100 min. It was found that improvement was achieved in the oxidation behaviour of titanium ion implanted samples compared with that of the as-received one. The valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy. Glancing angle X-ray diffraction was used to examine the phase transformation in the oxide films and is showed that the addition of titanium transformed the phase from monoclinic zirconia to hexagonal zirconia. Finally, the mechanism of improvements oxidation behaviour is discussed.     

Ion-implanted resist removal using atomic hydrogen

We removed B-, P-, and As-ion-implanted positive-tone novolak resists with an implantation dose of 5 × 10¹² to 5 × 10¹⁵ atoms/cm² at 70 keV, using atomic hydrogen. Though the removal rate decreased with increase in the implantation dose, all of the ion-implanted resists were removed. The rates of thickness of the surface-hardened layer/all resist layer of B, P, and As implanted resists were 0.38, 0.26, and 0.16, respectively, by SEM observation. The removal rate decreased with increasing the rate of the surface-hardened layer. The energy supplied from the ions to the resist concentrated on the surface side in the increasing order of B-P-As.     

Surface analysis of argon-implanted zircalloy-2 and influence of bubble formation on the corrosion behavior

In order to simulate the irradiation damage, argon ions were implanted into zircalloy-2 alloy with a fluence ranging from 1×10¹⁶ to 1×10¹⁷ ions/cm², using an implanter at an extraction voltage of 190 kV, at liquid nitrogen temperature. Then the effect of argon ion implantation on the aqueous corrosion behavior of zircalloy-2 alloy was studied. The valence states of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) was used to examine the microstructure of the argon-implanted samples. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the argon ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircalloy-2 alloy in a 1 M H₂SO₄ solution. It was found that the bubbles were formed on the surface of implanted samples; the bubbles grew larger with increasing argon fluence. The microstructure of argon-implanted samples changed from amorphous to partial amorphous, then to polycrystalline and finally to amorphous. The bubble forming and changing and microstructure changes affected the corrosion properties of implanted samples. Finally, the mechanism of the corrosion behavior of argon-implanted zircalloy-2 alloy is discussed.     

Comparison of corrosion behavior of zirconium bombarded with self-ion and molybdenum ion

In order to study the effects of zirconium and molybdenum ion bombardment on the aqueous corrosion behavior of zirconium, one group of specimens was implanted with zirconium ions with ions surface densities ranging from 1 × 10¹⁵ to 2 × 10¹⁷ ions/cm² at about 170 °C, using a metal vapor vacuum arc (MEVVA) source operated at an extraction voltage of 50 kV. The other group of specimens was bombarded with molybdenum ion with ions surface densities ranging from 1 × 10¹⁶ to 5 × 10¹⁷ ions/cm² at about 160 °C, using a MEVVA source operated at an extraction voltage of 40 kV. The valence states and depth distribution of elements in the surface of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Polarization curves measurement was employed to evaluate the aqueous corrosion resistance of the zirconium samples in a 1N H₂SO₄ solution. It was found that the aqueous corrosion resistance of zirconium implanted with 5 × 10¹⁶ Zr ions/cm² is the best in first group samples. For molybdenum ion implantation, the aqueous corrosion resistance of samples declined with raising ions surface densities. The natural corrosion potentials of zirconium samples bombarded with self-ions are more negative than that of the as-received zirconium. While, as for molybdenum ion implantation, the results are opposite. Finally, the mechanisms of the corrosion behavior of the zirconium samples implanted with zirconium and molybdenum ions are discussed.     

Effects of Si-ion implantation on crystallization behavior of Ge2Sb2Te5 film

Crystallization and thermal stability of Ge₂Sb₂Te₅ (GST), the benchmark working material in phase-change non-volatile memory, were modified via Si-ion implantation. Through 5 × 10¹⁵ Si-ions/cm² ion-implantation, crystallization temperature increases from 165 °C to 177 °C. Furthermore, the activation energy of crystallization increases from 2.9 eV in the pristine film to 3.3 eV and 4.0 eV in films implanted with the doses of 5 × 10¹⁵ and 5 × 10¹⁶ Si-ions/cm², respectively. Temperatures corresponding to a 10-year failure-time increase from 83 °C in the pristine film to 96 °C and 107 °C in films implanted with 5 × 10¹⁵ and 5 × 10¹⁶ Si-ions/cm², respectively. Thermal stability of Si-ion implanted GST thus improves significantly. It was also found that grain growth is inhibited with higher implantation doses. In the case of the 5 × 10¹⁶ ion/cm² dose, the second-phase transition from face-centered cubic to hexagonal closed-packed structure of the GST is completely inhibited. However, crystallization time increases slightly due to Si-ion implantation.     

Effect of calcium-ion implantation on the corrosion resistance and bioactivity of the Ti6Al4V alloy

The corrosion resistance and bioactivity of Ti6Al4V alloy after calcium-ion implantation were examined. Polished samples were implanted with a dose of 10¹⁷ Na⁺/cm² at a beam energy of 25 keV. The chemical composition of the surface layer formed during the implantation was determined by XPS and SIMS. The bioactivity of the samples was evaluated by soaking them in a simulated body fluid (SBF) at 37 °C for 168 and 720 h. The corrosion resistance in SBF at 37 °C was determined by electrochemical methods after exposure in SBF for various times. The surfaces of the samples before and after examinations were observed by optical microscopy, SEM-EDS and AFM.The results of the corrosion examinations indicated that under stationary conditions and after short-term exposures, the calcium-ion implanted titanium alloy had an increased corrosion resistance, but during the anodic polarization, calcium-implanted samples underwent pitting corrosion. The microscopic observations show that the precipitations of calcium phosphates are present on the surface, but they do not form a continuous layer.     

Rapid degradation of biomedical magnesium induced by zinc ion implantation

The degradation rate is important to biodegradable magnesium materials. In this study, Zn is implanted using a cathodic arc source into pure magnesium at an accelerating voltage of 35 kV. The nominal ion implant fluence is 2.5 × 10¹⁷ ions cm⁻². After Zn implantation, the degradation rate in simulated body fluids is increased significantly. It is postulated that because Zn exists in the metallic state in the implanted layer, the galvanic effect between the Zn rich surface region and magnesium matrix induces the observed accelerated degradation.     

Study of SHI induced recrystallization effects in SOI structures synthesized by nitrogen and oxygen ion implantation in silicon

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻² to prepare silicon on insulator (SOI) structures. The as implanted samples were held at 270 °C and irradiated to total fluence of 1 × 10¹⁴ cm⁻² by 60 MeV Ni⁺⁵ to study the structural changes/recrystallization of SOI structures induced by swift heavy ion (SHI) irradiation. Fourier transform infrared (FTIR) measurements on the as implanted samples (≤1 × 10¹⁸ cm⁻²) show a single absorption band in the wavenumber range 1300-750 cm⁻¹ attributed to the formation of silicon oxynitride (Si-O-N) bonds in the implanted silicon. It is observed that a nitrogen rich silicon oxynitride structure is formed after SHI irradiation. The study of X-ray rocking curves on the samples show the formation of small silicon crystallites due to swift heavy ion irradiation.     

Cyclic oxidation behaviour of cerium implanted AZ31 magnesium alloys

AZ31 samples were implanted with 90 keV cerium ions with a dose of 1 × 10¹⁷ ions/cm². Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Glancing angle X-ray diffraction (GAXRD) were used in order to investigate the characterization of elements in the implanted surface. The results indicate that after cerium implantation a pre-oxidation layer with double structure was formed. The influence of cerium implantation on the cyclic oxidation behaviour of AZ31 samples was studied at 773 K in air for 96 h, and the morphologies of the oxide scales were examined by scanning electron microscopy (SEM). It was found that the oxidation resistance of the implanted sample has been improved. The mechanisms to explain the experimental results were also proposed.     

HI-ERDA, Micro-Raman and HRXRD studies of buried silicon oxynitride layers synthesized by dual ion implantation

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by dual implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially into single crystal silicon in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻². Heavy ion elastic recoil analysis (HI-ERDA) studies of as implanted samples show Gaussian like distributions of nitrogen and oxygen. After annealing at 800 °C, both the nitrogen and oxygen distributions appear as flat plateau like regions near projected range showing the formation of a continuous buried oxynitride layer. Micro-Raman study of as implanted samples shows a broad peak at 480 cm⁻¹ for all fluences. It signifies a complete amorphization of silicon due to high fluence implantation. The annealing at 800 °C results in the reduction of the intensity of the broad peak observed at 480 cm⁻¹ and also gives rise to an additional peak at 517 cm⁻¹. It shows partial recrystallization of damaged silicon due to annealing. The X-ray rocking curves studies from high-resolution X-ray diffraction (HRXRD) of the samples implanted with different fluences have also further confirmed partial recrystallization of damaged silicon on annealing.     

Phase formation and modification of corrosion property of nitrogen implanted Ti-Al-V alloy

In the present investigation, polished samples were implanted with nitrogen ion at an energy of 60 keV and implantation doses were 1×10¹⁶, 5×10¹⁶, 1×10¹⁷ and 6×10¹⁷ ions/cm². Glancing incidence X-ray diffraction was employed on the implanted specimens to understand the phases formed with increasing dose. The valence states of nitrogen, titanium and carbon on the sample surfaces were analyzed by X-ray photoemission spectroscopy. The corrosion resistance was examined by the electrochemical methods in a solution with pH=10 at room temperature in order to determine the optimum dose that can give good corrosion resistance in a simulated nuclear reactor condition. Scanning electron microscopy was used to observe the topographies of nitrogen-implanted Ti-Al-Zr after potentiodynamic measurement. It was found that implanted nitrogen dissolved in titanium matrix with increasing dose and the resultant nitrides such as TiN and Ti₂N precipitated. Implantation of nitrogen ions into the surface of Ti-Al-V alloy improves its corrosion resistance, and the increase of the corrosion resistance depends on the nitrogen dose employed; the maximum improvement of the corrosion resistance was observed at a dose of 1×10¹⁷ N⁺/cm².