High temperature annealing of Europium implanted AlN

AlN was implanted with 300 keV Eu ions within a wide fluence range from 4 × 10¹⁴ to 1.4 × 10¹⁷ at/cm². The damage build-up was investigated by Rutherford Backscattering/Channelling. Sigmoidal shaped damage build-up curves indicate efficient dynamic annealing. A regime with low damage increase for fluences below 10¹⁵ at/cm² is followed by a strong increase for intermediate fluences. For the highest fluences the damage curve rises slowly until a buried amorphous layer is formed. High temperature annealing was performed in nitrogen atmospheres at low pressure (1300 °C, 10⁵ Pa) or at ultra-high pressure (1450 °C, 10⁹ Pa). Implantation damage was found to be extremely stable and annealing only resulted in slight structural recovery. For high fluences out-diffusion of Eu is observed during annealing. Nevertheless, photoluminescence (PL) measurements show intense Eu-related red light emission for all samples with higher PL intensity for the high temperature high pressure annealing.     

Structural characterization of buried nitride layers formed by nitrogen ion implantation in silicon

The synthesis of buried silicon nitride insulating layers was carried out by SIMNI (separation by implanted nitrogen) process using implantation of 140 keV nitrogen (¹⁴N⁺) ions at fluence of 1.0 × 10¹⁷, 2.5 × 10¹⁷ and 5.0 × 10¹⁷ cm⁻² into 〈1 1 1〉 single crystal silicon substrates held at elevated temperature (410 °C). The structures of ion-beam synthesized buried silicon nitride layers were studied by X-ray diffraction (XRD) technique. The XRD studies reveal the formation of hexagonal silicon nitride (Si₃N₄) structure at all fluences. The concentration of the silicon nitride phase was found to be dependent on the ion fluence. The intensity and full width at half maximum (FWHM) of XRD peak were found to increase with increase in ion fluence. The Raman spectra for samples implanted with different ion fluences show crystalline silicon (c-Si) substrate peak at wavenumber 520 cm⁻¹. The intensity of the silicon peak was found to decrease with increase in ion fluence.     

Synthesis and characterization of SnO2 nanoparticles embedded in silica by ion implantation

Tin dioxide nanoparticles embedded in silica matrix were fabricated by ion implantation combined with thermal oxidation. Silica substrate was implanted with a 150 keV Sn⁺ ions beam with a fluence of 1.0 × 10¹⁷ ions/cm². The sample was annealed for 1 h in a conventional furnace at a temperature of 800 °C under flowing O₂ gas. According to the structural characterization performed by X-ray diffraction and transmission electron microscopy techniques, metallic tetragonal tin nanoparticles with a volume average size of 12.8 nm were formed in the as-implanted sample. The annealing in oxidizing atmosphere promotes the total oxidation of the tin nanoparticles into tin dioxide nanoparticles with a preferential migration toward the surface of the matrix, where large and coalesced nanoparticles were observed, and a small diffusion toward the bulk, where smaller nanoparticles were found.     

Dynamic annealing study of SiC epilayers implanted with Ni ions at different temperatures

SiC epilayers grown on 4H-SiC single crystals were implanted with 850 keV Ni⁺ ions with fluences in the 0.5-9 × 10¹⁶ Ni⁺/cm² range. Most of the samples were implanted at 450 °C, but for comparison some implantations were performed at room temperature (RT). In addition, a post-implantation annealing was performed in N₂ at 1100 °C in order to recover the implantation-induced structural damage. The disorder produced by the implantation at 450 °C and the effect of the post-implantation annealing on the recrystallization of the substrates have been studied as a function of the fluence by Backscattering Spectrometry in channeling geometry (BS/C) with a 3.45 MeV He²⁺ beam. RT as-implanted samples showed a completely amorphous region which extends until the surface when irradiated with the highest dose, whereas in the case of 450 °C implantation amorphization does not occur. In general, partial recovery of the crystal lattice quality was found for the less damaged samples, and the dynamic recovery of the crystalline structure increases with the irradiation temperature.     

Effect of annealing on structure and hardness of oxygen-implanted layer on Ti6Al4V by plasma-based ion implantation

Ti6Al4V was treated by oxygen plasma-based ion implantation at the voltage pulses of −30 and −50 kV with a constant fluency of 0.6 × 10¹⁷ O/cm². After implantation, the annealing in vacuum was applied to the implanted samples to control phase structure of the implanted layer. The higher voltage implantation forms nano-size rutile in the implanted layer, but the subsequent annealing at 600 °C induces the resolution of the previous rutile. Although, the lower voltage implantation does not lead to rutile, the annealing can precipitate anatase and rutile in the implanted layer. The higher voltage implantation results in a higher hardness of the implanted layer. The annealing at 500 °C leads to an apparent increase in hardness of the implanted layer, but the annealing at 600 °C induces a rapid decrease in hardness.     

Structural studies of silicon oxynitride layers formed by low energy ion implantation

Silicon oxynitride (Si_xO_yN_z) layers were synthesized by implanting ¹⁶O₂⁺ and ¹⁴N₂⁺ 30 keV ions in 1:1 ratio with fluences ranging from 5 × 10¹⁶ to 1 × 10¹⁸ ions cm⁻² into single crystal silicon at room temperature. Rapid thermal annealing (RTA) of the samples was carried out at different temperatures in nitrogen ambient for 5 min. The FTIR studies show that the structures of ion-beam synthesized oxynitride layers are strongly dependent on total ion-fluence and annealing temperature. It is found that the structures formed at lower ion fluences (∼1 × 10¹⁷ ions cm⁻²) are homogenous oxygen-rich silicon oxynitride. However, at higher fluence levels (∼1 × 10¹⁸ ions cm⁻²) formation of homogenous nitrogen rich silicon oxynitride is observed due to ion-beam induced surface sputtering effects. The Micro-Raman studies on 1173 K annealed samples show formation of partially amorphous oxygen and nitrogen rich silicon oxynitride structures with crystalline silicon beneath it for lower and higher ion fluences, respectively. The Ellipsometry studies on 1173 K annealed samples show an increase in the thickness of silicon oxynitride layer with increasing ion fluence. The refractive index of the ion-beam synthesized layers is found to be in the range 1.54-1.96.     

Effects of Mg-ion implantation in α-Al2O3 and α-Al2O3:Mg crystals: Electrical conductivity and electronic structure changes

Undoped and Mg-doped α-Al₂O₃ single crystals were implanted with Mg ions, with an energy of 90 keV and a fluence of 10¹⁷ ions/cm². DC electrical measurements using the four-point probe method, between 295 and 428 K, were used to characterize the electrical conductivity of the implanted area. Measurements in this temperature range indicate that the electrical conductivity after implantation is thermally activated with an activation energy of about 0.03 eV both in undoped and in reduced Mg-doped α-Al₂O₃ crystals, whereas the activation energy in oxidized Mg-doped α-Al₂O₃ crystals remains close to that before implantation. The I-V characteristics of the latter samples reveal a blocking behavior of the electrical contacts on the implanted area in contrast to the ohmic contacts observed in α-Al₂O₃ single crystals with the c-axis perpendicular to the broad face, where the Mg ions were implanted. We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation, rather than to the implanted Mg ions. The relationship between the oxygen vacancy concentrations at different stages of etching and the changes in the electronic structure, the chemical bonding, and the Al³⁺(2p)/O²⁻(1s) and Mg²⁺(1s)/O²⁻(1s) relative intensities was studied by X-ray Photoemission Spectroscopy.     

The interdiffusion and solid-state reaction of low-energy copper ions implanted in silicon

At room temperature, single-crystal silicon was implanted with Cu⁺ ions at an energy of 80 keV using two doses of 5 × 10¹⁵ and 1 × 10¹⁷ Cu⁺ cm⁻². The samples were heat treated by conventional thermal annealing at different temperatures: 200 °C, 230 °C, 350 °C, 450 °C and 500 °C. The interdiffusion and solid-state reactions between the as-implanted samples and the as-annealed samples were investigated by means of Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). After annealing at 230 °C, the XRD results of the samples (subject to two different doses) showed formation of Cu₃Si. According to RBS, the interdiffusion between Cu and Si atoms after annealing was very insignificant. The reason may be that the formation of Cu₃Si after annealing at 230 °C suppressed further interdiffusion between Si and Cu atoms.     

FTIR and RBS study of ion-beam synthesized buried silicon oxide layers

Single crystal silicon samples were implanted at 140 keV by oxygen (¹⁶O⁺) ion beam to fluence levels of 1.0 × 10¹⁷, 2.5 × 10¹⁷ and 5.0 × 10¹⁷ cm⁻² to synthesize buried silicon oxide insulating layers by SIMOX (separation by implanted oxygen) process at room temperature and at high temperature (325 °C). The structure and composition of the ion-beam synthesized buried silicon oxide layers were investigated by Fourier transform infrared (FTIR) and Rutherford backscattering spectroscopy (RBS) techniques. The FTIR spectra of implanted samples reveal absorption in the wavenumber range 1250-750 cm⁻¹ corresponding to the stretching vibration of Si-O bonds indicating the formation of silicon oxide. The integrated absorption band intensity is found to increase with increase in the ion fluence. The absorption peak was rather board for 325 °C implanted sample. The FTIR studies show that the structures of ion-beam synthesized buried oxide layers are strongly dependent on total ion fluence. The RBS measurements show that the thickness of the buried oxide layer increases with increase in the oxygen fluence. However, the thickness of the top silicon layer was found to decrease with increase in the ion fluence. The total oxygen fluence estimated from the RBS data is found to be in good agreement with the implanted oxygen fluence. The high temperature implantation leads to increase in the concentration of the oxide formation compared to room temperature implantation.     

The influence of the microstructure evolution on the surface morphology in the annealing process of helium-implanted spinel

Single-crystalline spinel (MgAl₂O₄) specimens were implanted with helium ions of 100 keV at three successively increasing fluences of (0.5, 2.0 and 8.0) × 10¹⁶ ions/cm² at room temperature. The specimens were subsequently annealed in vacuum at different temperatures ranging from 500 to 1100 °C. Different techniques, including Fourier transformed infrared spectroscopy (FTIR), thermal desorption spectrometry (TDS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the specimens. It was found that the absorbance peak in the FTIR due to the stretching vibration of the Al-O bond shifts to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with an increase of annealing temperature. The absorbance peak shift has a linear relationship with the fluence increase in the as-implanted state, while it does not have a linear relationship with the fluence increase after the annealing process. Surface deformation occurred in the specimens implanted with fluences of 2.0 and 8.0 × 10¹⁶ ions/cm² in the annealing process. The phenomena described above can be attributed to differences in defect formation in the specimens.     

Oxidation kinetics of magnesium alloys treated by tantalum ions implantation

AZ31 magnesium alloys were implanted with tantalum ions with doses of 1 × 10¹⁶, 5 × 10¹⁶ and 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc (MEVVA) at an extraction voltage of 45 kV. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) analysis suggested that tantalum ions implantation promoted the formation of the pre-oxidation layer and a new Ta₂Al phase was formed in the implanted layer. Then, the oxidation kinetics of the implanted specimens was investigated by isothermal oxidation at 773 K in pure O₂ up to 90 min. The results showed that after implantation treatments the oxidation resistance of the specimens was significantly improved and the specimen with the highest dose had the best oxidation resistance. Finally, the mechanism of the anti-oxidation effects was also discussed.     

Surface exfoliation and defect structures in Si induced by 160 keV He and 110 keV H ion implantation

Cz n-type Si(100) wafers were implanted at room temperature with 160 keV He ions at a fluence of 5 × 10¹⁶/cm² and 110 keV H ions at a fluence of 1 × 10¹⁶/cm², singly or in combination. Surface phenomena and defect microstructures have been studied by various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). Surface exfoliation and flaking phenomena were only observed on silicon by successive implantation of He and H ions after subsequent annealing at temperatures above 400 °C. The surface phenomena show strong dependence on the thermal budget. At annealing temperatures ranging from 500 to 700 °C, craters with size of about 10 μm were produced throughout the silicon surface. As increasing temperature to 800 °C, most of the implanted layer was sheared, leaving structures like islands on the surface. AFM observations have demonstrated that the implanted layer is mainly transfered at the depth around 960 nm, which is quite consistent with the range of the ions. XTEM observations have revealed that the additional low fluence H ion implantation could significantly influence thermal growth of He-cavities, which gives rise to a monolayer of cavities surrounded by a large amount of dislocations and strain. The surface exfoliation effects have been tentatively interpreted in combination of AFM and XTEM results.     

N-TiO2 nanoparticles embedded in silica prepared by Ti ion implantation and annealing in nitrogen

Room-temperature Ti ion implantation and subsequent thermal annealing in N₂ ambience have been used to fabricate the anatase and rutile structured N-doped TiO₂ particles embedded in the surface region of fused silica. The Stopping and Range of Ions in Matter (SRIM) code simulation indicates a Gaussian distribution of implanted Ti, peaked at ∼75 nm with a full width at half maximum of ∼80 nm. However, the transmission electron microscopy image shows a much shallower distribution to depth of ∼70 nm. Significant sputtering loss of silica substrates has occurred during implantation. Nanoparticles with size of 10-20 nm in diameter have formed after implantation. X-ray photoelectron spectroscopy indicates the coexistence of TiO₂ and metallic Ti in the as-implanted samples. Metallic Ti is oxidized to anatase TiO₂ after annealing at 600 °C, while rutile TiO₂ forms by phase transformation after annealing at 900 °C. At the same time, N-Ti-O, Ti-O-N and/or Ti-N-O linkages have formed in the lattice of TiO₂. A red shift of 0.34 eV in the absorption edge is obtained for N-doped anatase TiO₂ after annealing at 600 °C for 6 h. The absorbance increases in the ultraviolet and visible waveband.     

Fabrication of hollow nanoclusters by ion implantation

Ag ions with four kinds of energies were implanted into silica to doses of 5 × 10¹⁶ and 1 × 10¹⁷ ions/cm², respectively. Hollow Ag nanoclusters were observed in the 1 × 10¹⁷ Ag⁺ ions/cm² implanted samples with energies of 150 and 200 keV. The evolution of hollow nanoclusters during annealing was carried out by in situ transmission electron microscopy observation. The energy dependence for the formation of hollow nanoclusters is studied. A potential mechanism for the formation of irradiation-induced nanovoids in nanoclusters is discussed.     

Structure and tribological performance of helium-implanted layer on Ti6Al4V alloy by plasma-based ion implantation

The present paper concentrates on tribological performance of Ti6Al4V alloy treated by helium plasma-based ion implantation with a voltage of −30 kV and a dose range of 1, 3, 6 and 9 × 10¹⁷ He/cm². X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and Atomic force microscopy (AFM) were used to characterize composition, structure and surface morphology, respectively. The variation of hardness with indenting depth was measured and tribological performance was evaluated. The uniform cavities with a diameter of several nanometers are formed in the helium-implanted layer on Ti6Al4V alloy. Helium implantation enhances the ingress of O, C and N and produces TiO₂, Al₂O₃, TiC, TiN in the near surface layer on their removal from the vacuum and exposure to normal atmospheric condition. In the near surface layer, the hardness of implanted samples increases remarkably comparing with the untreated sample, and the maximum peak increasing factor is up to 2.9 for the sample implanted with 3 × 10¹⁷ He/cm². A decrease in surface roughness, resulting from the leveling effect of sputtering and re-deposition during implantation, has also been observed. Comparing with the untreated sample, implanted samples have a good wear resistance property. And the maximum increase in wear resistance reaches over seven times that of the untreated one for the sample implanted with 3 × 10¹⁷ He/cm². The wear mechanism of implanted samples is abrasive-dominated.     

Determination of migration of ion-implanted helium in silica by proton backscattering spectrometry

Understanding the processes caused by ion implantation of light ions in dielectric materials such as silica is important for developing the diagnostic systems used in fusion and fission environments. Recently, it has been shown that ion-implanted helium is able to escape from SiO₂ films. To study this process in details, helium was implanted into the central part of a buried SiO₂ island up to a fluence of 4 × 10¹⁷ He/cm². The implanted helium could be detected in the SiO₂ island, if the oxide was insulated properly from the vacuum. The shape of the helium depth distributions was far from SRIM simulation because helium distributed in the whole 1 μm thick oxide layer. After the ion implantation, helium was observed only on the implanted spot. After nine months the implanted helium filled out the whole oxide island as it was expected from the high diffusivity.     

Tailoring optical and electrical properties of MgO thin films by 1.5 MeV H implantation to fluences

Thin films of magnesia (MgO) with (1 0 0) dominant orientations were implanted with 1.5 MeV H⁺ ions at room temperature to various fluences of 10¹³, 10¹⁴ and 10¹⁵ ions/cm². X-ray analysis unambiguously showed crystallinity even after a peak damage fluence of 10¹⁵ ions/cm². Rutherford backscattering spectrometry combined with ion channeling (RBS/C) was used to analyze radiation damages and defect distributions. Optical absorption band observed at 5.7 eV in implanted films was assigned to the anion vacancies and the defect was completely disappeared on annealing at 450 °C. Number of F-type defects estimated was 9.42 × 10¹⁵ cm⁻² for the film implanted with 10¹⁵ ions/cm². DC electrical conductivity of 4.02 × 10⁻⁴ S cm⁻¹ was observed in the implanted region which was three orders higher than the as-deposited films. In unison, film surface was modified as a result of the formation of aggregates caused by the atomic mixing of native matrix atoms (Mg and O) and precipitated hydrogen.     

Structural and magnetic characterization of cobalt implanted GaN films

Cobalt ions were implanted into GaN films with multiple energies between 50 keV and 380 keV with two total fluences, 1.25 × 10¹⁶ and 1.25 × 10¹⁷ cm⁻², followed by annealing at temperatures between 600 and 850 °C. The crystal quality and surface morphology of as-implanted and subsequently annealed films were investigated by X-ray diffraction (XRD) 2θ scans, ω-rocking curve measurements and atomic force microscopy (AFM). The profiles of impurities and defects were analyzed by Rutherford backscattering spectrometry (RBS) in random and channeling configurations. The virgin GaN films have an excellent crystal quantity (χ_min = 1.4%) and in the implanted samples 60% disorder induced by ion implantation was recovered after annealing. The annealed sample become ferromagnetic, with a spontaneous magnetization of 0.1 emu/g and a coercive magnetic field of 100 Oe at 10 K, and the Curie point was found to be higher than room temperature.     

The range distribution and annealing behavior of Er ions implanted in silicon-on-insulator

The range distribution for energetic 400 keV Er ions implanted in silicon-on-insulator (SOI) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The damage distribution and annealing behavior of implanted Er ions in SOI at the energy of 400 keV with dose of 5 × 10¹⁵ cm⁻² were obtained by Rutherford backscattering technique. It has been found that the damage around the SOI surface had been almost removed after annealed in nitrogen atmosphere at 900 °C, and a lot of Er atoms segregate to the surface of sample with the recrystallization of surface Si of SOI sample after annealing at 900 °C.     

Effect of swift heavy ion irradiation on structural, optical and electrical properties of Cd2SnO4 thin films

Transparent conducting cadmium stannate thin films were prepared by spray pyrolysis method on Corning substrate at a temperature of 525 °C. The prepared films are irradiated using 120 MeV swift Ag⁹⁺ ions for the fluence in the range 1 × 10¹² to 1 × 10¹³ ions cm⁻² and the structural, optical and electrical properties were studied. The intensity of the film decreases with increasing ion fluence and amorphization takes place at higher fluence (1 × 10¹³ ions cm⁻²). The transmittance of the films decreases with increasing ion fluence and also the band gap value decreases with increasing ion fluence. The resistivity of the film increased from 2.66 × 10⁻³ Ω cm (pristine) to 5.57 × 10⁻³ Ω cm for the film irradiated with 1 × 10¹³ ions cm⁻². The mobility of the film decreased from 31 to 12 cm²/V s for the film irradiated with the fluence of 1 × 10¹³ ions cm⁻².