Surface-hardening effect of B implantation in 6H-SiC ceramics

This study was conducted on the surfacehardening effect of boron ion implantation in 6H-SiC ceramics. The SiC samples prepared by pressureless sintering were carefully polished, and 500 keV B⁺ implanted in 6H-SiC ceramics at room temperature and four implantation doses, namely, 1×10¹⁵, 5×10¹⁵, 1×10¹⁶, and 5×10¹⁶ cm⁻², were chosen. The implanted samples were analyzed by scanning electron microscope and Raman spectra. The Vickers hardness of the samples was evidently increased. The thickness of the damage layer was about 1 μm, which is consistent with the simulated results. The structure of the damage layer was different from the internal part and severely damaged at high doses.     

Defect formation in silicon implanted with ∼1 MeV/nucleon ions

Defect formation processes in silicon implanted with ∼1 MeV/nucleon boron, oxygen, and argon ions have been studied using microhardness and Hall effect measurements. The results indicate that ion implantation increases the surface strength of silicon single crystals owing to the formation of electrically inactive interstitials through the diffusion of self-interstitials from the implantation-damaged layer to the silicon surface. The radiation-induced surface hardening depends significantly on the nature of the ion, its energy, and the implant dose. In the case of low-Z (boron) ion implantation, the effect had a maximum at an implant dose of ∼5 × 10¹⁴ cm⁻², whereas that for O⁺ and Ar⁺ ions showed no saturation even at the highest dose reached, 1 × 10¹⁶ cm⁻². When the ion energy was increased to ∼3 MeV/nucleon (210-MeV Kr⁺ ion implantation), we observed an opposite effect, surface strength loss, due to the predominant generation of vacancy-type defects.     

Fabrication and characterization of Ge nanocrystalline growth by ion implantation in SiO<Subscript>2</Subscript> matrix

Ge nanocrystallites (Ge-nc) have been formed by ion implantation of Ge⁺⁷⁴ into SiO₂ matrix, thermally grown on p-type Si substrates. The Ge-nc are examined by Raman spectroscopy, photoluminescence (PL) and Fourier transform infrared spectroscopy (FTIR). The samples were prepared with various implantation doses [0.5; 0.8; 1; 2; 3; 4] × 10¹⁶ cm⁻² with 250 keV energy. After implantation, the samples were annealed at 1,000 °C in forming gas atmosphere for 1 h. Raman intensity variation with implantation doses is observed, particularly for the peak near 304 cm⁻¹. It was found that the sample implanted with a doses of 2 × 10¹⁶ cm⁻² shows maximum photoluminescence intensity at about 3.2 eV. FTIR analysis shows that the SiO₂ film moved off stoichiometry due to Ge⁺⁷⁴ ion implantation, and Ge oxides are formed in it. This result is shown as a reduction of GeO_x at exactly the doses corresponding to the maximum blue-violet PL emission and the largest Raman emission at 304 cm⁻¹. This intensity reduction can be attributed to a larger portion of broken Ge–O bonds enabling a greater number of Ge atoms to participate in the cluster formation and at the same time increasing the oxygen vacancies. This idea would explain why the FTIR peak decreases at the same implantation doses where the PL intensity increases.     

Mixing in Au/Ge system induced by Ar<Superscript>+</Superscript> ion irradiation

Rutherford Backscattering Spectrometry (RBS) and Electrical Resistivity Measurements (ERM) were used to investigate the mixing of Au/Ge bilayer deposited onto glass substrate induced by Ar ions. Mixing was initiated by bombarding the sample with 400 keV ⁴⁰Ar⁺ beam with a fluence up to 1.2 × 10¹⁷ ions/cm² at a constant flux of 0.25 μA/cm². To assist the evaluation of the experimental results, all spectra were simulated using “RUMP” computer code. RBS results indicated that ion beam mixing led to a formation of AuGe₂ compound. The mixed region was noticed to increase with the gradual increase of Ar⁺ fluence. Results were also compared with current theoretical models used to describe the mixing process. The Bφrgesen thermal spike model was found to accurately predict the diffusion in Au/Ge interface. An increase in the electrical resistivity of the film was detected during Ar⁺ irradiation.     

<Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junctions in ZnO implanted with group V ions

n-Type ZnO〈Ga〉 films were implanted with 150-keV N⁺ (As⁺) ions to a dose of 7 × 10¹⁵ cm⁻² and then annealed in atomic oxygen at different temperatures. p-Type conductivity was obtained at annealing temperatures in the range 770–870 K. The parameters of the p-type layers were determined by photoluminescence spectroscopy, secondary ion mass spectrometry, and Hall effect measurements. According to the Hall data, the p-type layers had a resistivity of ∼30 Ω cm, carrier mobility of ∼2 cm²/(V s), and carrier concentration of ∼10¹⁸ cm⁻³. The electroluminescence spectra of the p-n junctions produced by ion implantation showed a band at 440 nm, due to recombination via donor-acceptor pairs.     

Surface hardening in N<Superscript>+</Superscript> implanted polycarbonate

The influence of low energy nitrogen ions on the surface hardness of polycarbonate has been studied by implanting some of these specimens with 100 keV N⁺ ions at a beam current of 1 μA/cm² in the dose range of 1 × 10¹⁵ to 1 × 10¹⁷ ions cm^?2. Knoop microhardness has been found to be increased nearly 24 times at a load of 9.8 mN, for the dose of 1 × 10¹⁷ ions cm^?2. The structural changes occurred in implanted specimens were studied by Raman analysis, UV–Visible spectroscopy, and X-ray diffraction techniques. Raman studies point toward the formation of a structure resembling hydrogenated amorphous carbon. Disordering in the surface structure (I _D/I _G ratio) has also been found to increase with ion fluence using Raman technique. UV–Visible spectroscopic analysis shows a clear enhancement in Urbach energy (disorder parameter) from a value of 0.61 eV (virgin sample) to 1.72 eV (at a fluence of 1 × 10¹⁷ N⁺ cm^?2) with increasing ion dose. The increase in Urbach energy has been found to be correlated linearly with the increase in Knoop microhardness number. Results of X-ray diffraction analysis also indicate disordering in implanted layers as a result of implantation. In the present work, the possible mechanism behind the formation of harder surfaces due to implantation has been discussed in detail.     

Leaching of<Superscript>60</Superscript>Co and<Superscript>137</Superscript>Cs from spent ion exchange resins in cement-bentonite clay matrix

The leaching rate of⁶⁰Co and¹³⁷Cs from the spent cation exchange resins in cement-bentonite matrix has been studied. The solidification matrix was a standard Portland cement mixed with 290–350 (kg/m³) spent cation exchange resins, with or without 2–5% of bentonite clay. The leaching rates from the cementbentonite matrix for⁶⁰Co : (4,2–7,0) × 10⁻⁵ (cm/d) and¹³⁷Cs : (3,2–6,6) × 10⁻⁴ (cm/d), after 125 days were measured. From the leaching data the apparent diffusivity of cobalt and cesium in cement-bentonite clay matrix with a waste load of 290–350 (kg/m³) spent cation exchange resins, was measured for⁶⁰Co : (1,1−4,0) × 10⁻⁶ (cm²/d) and¹³⁷Cs : (0,5–2,6) x× 10⁻⁴ (cm²/d), after 125 days. The results presented in this paper are part of the results obtained in a 20-year mortar and concrete testing project which will influence the design of radio-active waste management for a future Serbian radioactive waste disposal centre.     

Analysis of layer splitting in x and z-cut KTiOPO4 implanted by H+ ions

H⁺ ions with various fluences are implanted into x and z-cut KTP crystals to achieve KTP film. Post-implantation annealing under different temperature is imposed on the samples to induce layer splitting and surface morphology modification. Layer exfoliation is observed in freestanding z-cut samples. Layer splitting is obtained using bonding method in x-cut sample implanted with 117 keV H⁺ ions at ion fluence of 6 × 10¹⁶ ions/cm². Optical microscopy, scanning electron microscope and atomic force microscopy are used to observe splitting phenomenon. Rutherford backscattering spectroscopy/channeling method is employed to measure lattice damage and to investigate the relationship between implantation-induced defects and layer splitting.     

Surface modification of Ti-4Al-2V alloy by nitrogen implantation

Ti-4Al-2V is a new type of alpha titanium alloy that suitable for the application in high-temperature and high-pressure water/steam environment. Ti-4Al-2V can be used in marine engineering, nuclear power industry. In this paper the surface characterization of the Ti-4Al-2V implanted with 75 keV nitrogen with fluences of 3 × 10¹⁷ and 8 × 10¹⁷ N⁺/cm² is investigated by glancing-incidence XRD, XPS and microhardness. The results show that new phase TiN are formed after N implantation in the surface region. The nitrogen implantation increases the surface hardness up to 340 and 260% for fluence of 8 × 10¹⁷ and 3 × 10¹⁷ N⁺/cm², respectively. The enhancement of hardness is related to the formation of TiN and irradiation induced hardness.     

Influence of the ion implantation of nitrogen and boron and TiN coatings on the corrosion of VT-6 titanium alloy

We study the corrosion-electrochemical properties of VT-6 titanium (α + β)-alloy in solutions of hydrochloric and sulfuric acids after high-energy ion implantation with nitrogen (E = 30 keV) for a dose of 2 · 10¹⁷ ion/cm² with subsequent annealing in a vacuum, with boron (E = 100 keV) for a dose of 1 · 10¹⁵ ion/cm², and with nitrogen and boron, as well as in the presence of ion-plasma titanium-nitride coating. It is shown that the modification of the surface increases the corrosion resistance of titanium in highly concentrated solutions of the acids. Note that the corrosion resistance of the titanium-nitride coating whose thickness does not exceed 10μm is somewhat lower than the corrosion resistance of the implanted alloy. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 89–94, May–June, 2008.     

Irradiation induced grain growth and surface emission enhancement of chemically tailored ZnS : Mn/PVOH nanoparticles by Cl<Superscript>+9</Superscript> ion impact

Manganese doped zinc sulfide nanoparticles are fabricated on polyvinyl alcohol dielectric matrix. They are bombarded with energetic chlorine ions (100 MeV). The size of the crystallites is found to increase with ion fluence due to melting led grain growth under ion irradiation. The increased size as a result of grain growth has been observed both in the optical absorption spectra in terms of redshift and in electron microscopic images. The photoluminescence (PL) study was carried out by band to band excitation (λ_ex = 220 nm) upon ZnS : Mn, which results into two emission peaks corresponding to surface states and Mn⁺² emission, respectively. The ion fluence for irradiation experiment so chosen were 1 × 10¹¹, 5 × 10¹¹, 5 × 10¹² and 10¹³ Cl/cm².     

Photoluminescence and Raman studies in swift heavy ion irradiated polycrystalline aluminum oxide

Polycrystalline aluminum oxide is synthesized by combustion technique and XRD studies of the sample revealed the α-phase. The synthesized sample is irradiated with 120 MeV swift Au⁹⁺ ions for the fluence in the range from 1 × 10¹¹ to 1 × 10¹³ ions cm⁻². A broad photoluminescence (PL) emission with peak at ∼ 447 nm and two sharp emissions with peak at ∼ 679 and ∼ 695 nm are observed in pristine when sample was excited with 326 nm. However, in the irradiated samples the PL intensity at ∼ 447, 679 and 695 nm decreases with increase in ion fluence. The α-Al₂O₃ gives rise to seven Raman modes with Raman intensity with peaks at ∼ 253, 396, 417, 546, 630, 842, 867 cm⁻¹ observed in pristine. The intensity of these modes decreases with increase in ion fluence. However, the Raman modes observed at lower fluences are found to disappear at higher fluence.     

Protonic conduction in Al2(SO4)3·16H2O: coulometry,transient ionic current,infrared and electrical conductivity studies

Proton transport in Al₂(SO₄)₃·16H₂O has been established using different techniques namely coulometry, transient ionic current, i.r., DTA/TGA and electrical conductivity. The possible charge carriers are H⁺ and OH⁻ generated as a result of possible electrolysis of hydrate water molecules. The mobilities of the two charge carriers are approximately 4×10⁻⁵ and 2.4×10⁻⁵cm²V⁻¹s⁻¹. The electrical conductivity shows strong dependence upon humidity and also shows a against 1/T behaviour closely related with its thermal dehydration reaction.     

Physical Properties of AZ91D Measured Using the Draining Crucible Method: Effect of SF<Subscript>6</Subscript>

The draining crucible (DC) technique was used for measurements on AZ91D under Ar and SF₆. The DC technique is a new method developed to simultaneously measure the physical properties of fluids, the density, surface tension, and viscosity. Based on the relationship between the height of a metal in a crucible and the outgoing flow rate, a multi-variable regression is used to calculate the values of these fluid properties. Experiments performed with AZ91D at temperatures from 923 K to 1173 K indicate that under argon, the surface tension (N · m⁻¹) and density (kg · m⁻³) are [0.63 − 2.13 × 10⁻⁴ (T − T _L)] and [1656 − 0.158 (T − T _L)], respectively. The viscosity (Pa · s) has been determined to be [1.455 × 10⁻³ − 1.209 × 10⁻⁵ (T − T _L)] over the temperature range from 921 K to 967 K superheat. Above 967 K, the viscosity of the alloy under argon seems to be constant at (2.66 × 10⁻⁴ ± 8.67 × 10⁻⁵) Pa · s. SF₆ reduces the surface tension of AZ91D.     

Controlling the wavelength of InGaAs/GaAs/InGaP lasers by ion implantation

The possibility of controlling the wavelength of emission from an InGaAs/GaAs/InGaP laser heterostructure with strained quantum wells (QWs) using medium-energy proton implantation followed by thermal annealing has been studied. It is established that the optimum proton energy is related to the arrangement of QWs in the structure (e.g., 150 keV for QWs at a depth of ≈1.3 μm). Proton irradiation to a total dose of 6 × 10¹⁴ cm⁻² followed by annealing at 700°C allows the wavelength of emission from the modified region to be decreased by 8–10 nm at minimum losses in the output intensity. The observed effect can be used to obtain two-band emission from the same chip and has good prospects for use in the development of new optoelectronic schemes.     

Nitrogen ion implantation effects on the structural,optical and electrical properties of CdSe thin film

In the present study, thin films of cadmium selenide (CdSe) are deposited on ITO substrate by electrodeposition method using aqueous solution of 3CdSO₄·8H₂O and SeO₂. These films are implanted with 40 keV N⁺ ions with different fluencies i.e. 1?×?10¹⁵, 5?×?10¹⁵, 1?×?10¹⁶ and 5?×?10¹⁶ ions/cm² using a beam current of 0.9 µA. The structural, morphological, optical and electrical properties of pristine and nitrogen ion-implanted CdSe thin films are analyzed using XRD, SEM, AFM, UV-PL Spectrophotometer and I–V four probes setup. XRD analysis revealed the effects of nitrogen ions on the structural parameters such as grain size, FWHM, micro strain and dislocation density etc. Crystallanity of the material increased with increase in implantation dose. SEM and AFM analysis show decrease in the surface roughness with implantation. From the optical studies, band gap value decreased from 2.50 to 2.29 eV with increase in N⁺ implantation doses. Noticeable changes in the electrical properties are also reported. The effect of N⁺ ion implantation on the properties of CdSe thin films are discussed on the basis of lattice disorder.     

Surface texturing of silicon by dynamic recoil mixing

A technique known as dynamic recoil mixing is used in which a film of constant mass of gold can be maintained on a silicon substrate whilst it is being bombarded by energetic ions. The technique is used to produce surface texturing of silicon. Scanning electron microscopy and Rutherford backscattering techniques have been used to study the development of surface texture as a function of 10 keV Ar⁺ ion fluence. The results show the regrowth of silicon crystallites into the gold film as the Ar⁺ ion fluence increases until at high doses of 1 × 10¹⁷ ions cm^-2 the silicon crystallites coalesce and overlap the initial layer burying some of the gold beneath them. IR transmission of the silicon textured surface shows an increase of 4% for an ion fluence of (1–6) × 10¹⁶ ions cm^-2 in the wavelenght range 2.5–3 μm.     

Preparation and characterization of indium oxide (In2O3) films by activated reactive evaporation

The electrical and optical properties of In₂O₃ films prepared at room temperature by activated reactive evaporation have been studied. Hall effect measurements at room temperature show that the films have a relatively high mobility 15 cm²v⁻¹s⁻¹, high carrier concentration 2·97 × 10²⁰/cm³, with a low resistivityρ = 1·35 × 10⁻³ ohm cm. As-prepared film is polycrystalline. It shows both direct and indirect allowed transitions with band gaps of 3·52eV and 2·94eV respectively.     

Electrically conducting thin films obtained by ion implantation in pyrolyzed polyacrylonitrile

Heat treatment of polyacrylonitrile (PAN) leads to products with semiconductor-to-metal range of conductivities. The electrical properties of these materials are further modified by ion implantation. The conductivity, 1×10^–7 (Ω cm)^–1, of heat treated PAN at 435°C (PAN435) increases upon ion implantation with As⁺, Kr⁺, Cl⁺ or F⁺, reaching the maximum value of 8.9×10^–1 (Ω cm)^–1 at a dose of 5×10¹⁶ ion/cm² and an energy of 200 KeV for the case of F⁺ implantation. On the other hand, ion implantation in the more conducting heat-treated PAN at 750 °C (PAN750) leads to a decrease in the electrical conductivity. It is shown that the conductivity modifications are primarily due to structural rearrangements induced by the energetic ions. Specific chemical doping contribution to conductivity is noted for halogen implantation in PAN435. The temperature dependence of conductivity of PAN heat treated at 750°C suggests a two path conduction, namely a three dimensional variable range hopping conduction and a metallic conduction. After ion implantation, the conductivity-temperature dependence is interpreted in terms of a variable range hopping conduction mechanism. Received: 25 August 2000 / Reviewed and accepted: 28 August 2000     

Diffusion coefficient of Fe<Superscript>2+</Superscript> in single-crystal ZnSe

The diffusion coefficient of Fe in single-crystal ZnSe has been measured in the temperature range 886–995°C. The 995°C diffusion coefficient is (47 ± 5) × 10⁻¹¹ cm²/s, and the average activation energy for Fe diffusion is 2.9 ± 0.3 eV.