As-implanted Samples Research Articles

Structural, optical and electrical properties of argon implanted TiN thin films

Modification in structural, optical and electrical properties of titanium nitride (TiN) thin films induced by argon ion irradiation and thermal annealings was studied using various experimental techniques. TiN thin films deposited by dc reactive sputtering on Si substrate were implanted with argon ions at 200keV. As-implanted samples were annealed before or after ion irradiation at 600°C and 700°C, respectively. Rutherford backscattering spectrometry, X-ray diffraction, cross-sectional (high-resolution) transmission electron microscopy, spectroscopic ellipsometry and electrical measurements were carried out in order to study structural, optical and electrical properties of TiN/Si samples. After irradiation with 200keV Ar ions the columnar microstructure of TiN was changed and the presence of smaller crystalline grains was observed. Partial loss of columnar structure observed in implanted samples was completely recovered after annealing at 700°C. Observed changes in microstructure induced by ion irradiation and annealings were correlated with the variation in optical parameters obtained by spectroscopic ellipsometry. It was found that both refractive index and extinction coefficient are strongly dependent on the defects' concentration and size of the crystalline grains in TiN layers.

Structural and optical properties of 70-keV carbon ion beam synthesized carbon nanoclusters in thermally grown silicon dioxide

The structural and optical properties of carbon nanoclusters formed in thermally grown silicon dioxide film via the ion beam synthesis process have been investigated. A low-energy (70 keV) carbon ion beam (C−) at a fluence of 3 × 1017 atoms/cm2 was used for implantation into a thermally grown silicon dioxide layer (500 nm thick) on a Si (100) wafer. Several parts of the implanted samples were subsequently annealed in a gas mixture (4 % H2 + 96 % Ar) at 900 °C for different time periods. The as-implanted and annealed samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The carbon ion implantation depth profile was simulated using a widely used Monte Carlo-based simulation code SRIM-2012. Additionally, the elemental depth profile of the implanted carbon along with host elements of silicon and oxygen were simulated using a dynamic ion–solid interaction code T-DYN, which incorporates the effects of the surface sputtering and gradual change in the elemental composition in the implanted layers due to high-fluence ion implantation. The elemental depth profile obtained from the XPS measurements matches closely to the T-DYN predictions. Raman measurements indicate the formation of graphitic phases in the annealed samples. The graphitic peak (G-peak) was found to be increased with the annealing time duration. In the sample annealed for 10 min, the sizes of the carbon nanoclusters were found to be 1–4 nm in diameter using TEM. The PL measurements at room temperature using a 325-nm laser show broad-band emissions in the ultraviolet to visible range in the as-implanted sample. Intense narrow bands along with the broad bands were observed in the annealed samples. The defects present in the as-grown samples along with carbon ion-induced defect centers in the as-implanted samples are the main contributors to the observed broad-band luminescence centered around 2.4 and 2.9 eV. The intense narrow peaks observed in the PL spectra centered on ~2.67 and 2.8 eV with full width at half maxima ≤ 150 meV are believed to be mainly due to the quantum size effects of the carbon nanoclusters formed in the annealed samples. The relative intensities of the narrow peaks are seen to be changing with the annealing time interval. This may be due to the change in the size distribution of the carbon nanoclusters.

The feasibility of Al-based oxide precipitation in Fe–10%Cr alloy by ion implantation

This paper reports the feasibility of nano-oxide precipitate formation in Fe–Cr alloy by ion implantation synthesis. High contents of Al+ and O+ ions were implanted into thin films of high purity Fe–10%Cr alloy at room temperature and were studied by transmission electron microscopy (TEM) and atom probe tomography (APT). In contrast, to the common two-stage implantation/annealing scheme of precipitate ensemble synthesis by ion beams, cluster formation took place at the implantation stage in our study, requiring no subsequent high-temperature annealing. The post-implantation microstructural examination revealed in the as-implanted thin foil an array of precipitates with diameters in the range of 3–30 nm. The precipitate number density distribution was found to depend on the foil thickness. The precipitate enrichment with both Al and O was confirmed by the energy-filtered TEM analysis. Judging from the electron diffraction pattern and high-resolution TEM analysis, the crystal lattice of precipitates corresponds to some cubic modification of aluminium-rich oxide or pure aluminium oxide. The precipitate lattice alignment with the host matrix was revealed for at least a part of precipitates. The analysis of APT data using cluster detection algorithm indicates the presence of local zones enriched in Al and O, even in those areas of as-implanted samples where no clusters were visible by TEM.

X-ray n-beam diffraction to study nanodefects of Xe+ implantation in Si(001)

Investigations about the nanocavities/bubbles formation by inert gas ion implantation in Si matrix and its properties have constituted an ongoing challenge in material science. Dislocation/extended defects (likely the {113} defects) are produced by post-implant annealing, which affect directly the nanocavities/bubbles structural evolution. In this work, the formation of defects induced by Xenon gas ion implantation in a Si sample (#Si-pristine) was studied by high-resolution reciprocal space mappings (RSM) and non-conventional X-ray Multiple Diffraction (XRMD) using synchrotron radiation. For this, Xe+ ions (80 keV; 5x1015 cm-2) were implanted in Si(001) at room temperature. Subsequently, the as-implanted samples were thermally annealed in air atmosphere at 600, 700 and 800 °C for 30 min in order to nucleate Xe nanobubbles that were detected in annealed samples by TEM images. Differences in the diffracted intensity pattern, along the crystal truncation rod, were detected in the Si (113) asymmetrical RSM for as-implanted and annealed samples, in comparison to pristine Si, indicating defect contribution along in-plane an out-of-plane directions. The ω(incident):Φ(azimuthal) coupled scans of two XRMD cases: 3-beam Bragg-Surface-Diffraction (BSD) (000)(002)(1-11) and the 4-beam (000)(002)(1-1-1)(1-13) have shown expected broader peaks (as-implanted sample) in comparison to the pristine sample, besides the ω-axis intensity asymmetry (c-axis strain induced). Furthermore, the analysis of all BSD mappings has provided: i) the annealing effect of reducing the lattice strain (600 and 700 °C samples), and ii) a huge surface effect through the diffuse scattering (800 °C-sample). As to the 4-beam case, a strong streak (diffraction condition trace) was observed for annealed sample patterns. This remarkable effect can be associated to the {113} defects, which are in the same direction of the secondary/coupling diffracting planes (XRMD phenomenon). It is believed that these defects break the spatial coherence, increasing the streak intensity. On the other hand, the streak is suppressed by the primary extinction effect in the pristine-Si and as-implanted samples. Financial support by Brazilian Synchrotron Light Laboratory (LNLS), CAPES, CNPq and FAPEMA.

Iodine assisted retainment of implanted silver in 6H-SiC at high temperatures

The effect of high temperature thermal annealing on the retainment and diffusion behaviour of iodine (I) and silver (Ag) both individually and co-implanted into 6H-SiC has been investigated using RBS, RBS-C and heavy ion ERDA (Elastic Recoil Detection Analysis). Iodine and silver ions at 360keV were both individually and co-implanted into 6H-SiC at room temperature to fluences of the order of 1×1016cm−2. RBS analyses of the as-implanted samples indicated that implantation of Ag and of I and co-implantation of 131I and 109Ag at room temperature resulted in complete amorphization of 6H-SiC from the surface to a depth of about 290nm for the co-implanted samples. Annealing at 1500°C for 30h (also with samples annealed at 1700°C for 5h) caused diffusion accompanied by some loss of both species at the surface with some iodine remaining in the iodine implanted samples. In the Ag implanted samples, the RBS spectra showed that all the Ag disappeared. SEM images showed different recrystallization behaviour for all three sets of samples, with larger faceted crystals appearing in the SiC samples containing iodine. Heavy Ion ERDA analyses showed that both 109Ag and 131I remained in the co-implanted SiC samples after annealing at 1500°C for 30h. Therefore, iodine assisted in the retainment of silver in SiC even at high temperature.

Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6×1020cm−3) into ZnO is performed using a multiple-step energy. The high resistivity of ∼103Ωcm in un-implanted samples remarkably decreased to ∼10−2Ωcm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000°C annealed ZnO.

Rutherford backscattering and nuclear reaction analyses of hydrogen ion-implanted ZnO bulk single crystals

The origins of low resistivity in H ion-implanted ZnO bulk single crystals are studied by Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) photoluminescence (PL), and Van der Pauw methods. The H-ion implantation (peak concentration: 1.45×1020cm−3) into ZnO is performed using a 500keV implanter. The resistivity decreases from 2.5×103Ωcm for unimplanted ZnO to 6.5Ωcm for as-implanted one. RBS measurements show that Zn interstitial as a shallow donor is not recognized in as-implanted samples. From photoluminescence measurements, the broad green band emission is observed in as-implanted samples. NRA measurements for as-implanted ZnO suggest the existence of the oxygen interstitial. The origins of the low resistivity in the as-implanted sample are attributed to both the H interstitial as a shallow donor and complex donor between H and disordered O. The activation energy of H related donors estimated from the temperature dependence of carrier concentration is 29meV.

On ion implantation and damage effect in Li2TiO3 as a fusion breeder blanket: A technological approach for degradation testing

The present work is a technological approach to establish testing techniques able to evaluate the release of the two Li-transmutation products and characterize the degradation of Li2TiO3 as breeder material. In an attempt to find the outgassing/release temperature of light gases and to study its bulk diffusion, nuclear reaction analysis (NRA) was used for profiling the 3He and D depth distributions of the as-implanted and damaged samples as a function of the annealing temperature. The defects generated by γ-rays and heavy-ion (Ti4+) irradiation were characterized by microRaman spectroscopy and confocal microscopy luminescence (CML) techniques. Considering the relevance of the microstructure (porosity and grain size), the study was supported by transmission electron microscope (TEM) observations and Hg-porosimetry measurements. Concerning D-implanted samples, the results suggest the complete release at temperatures higher than 200°C. On the other hand, the implanted 3He desorbs continuously with temperature, a 7–8% still being measured at 700°C.

A study of the structural and magnetic properties of ZnO implanted by Gd ions

The structural and magnetic properties of ZnO (0001) single crystals implanted with 200keV Gd ions up to a fluence of 5×1015cm−2 and subsequently annealed at 800°C in various atmospheres were studied. The chemical composition and concentration depth profiles of ion-implanted layers were characterised by Rutherford Back-Scattering spectrometry (RBS) and compared to SRIM simulations. The as-implanted Gd depth profiles were found to be broader than those simulated by SRIM, but the projected range coincided well with that simulated. After annealing at 800°C, the depth profiles became narrower. The structural changes in the layers modified by ion implantation and subsequent annealing were characterised by RBS channelling. The annealing led to partial recrystallisation and a decrease in the number of Gd atoms situated in substitutional positions. Raman spectroscopy showed that the point defects in Zn and O vacancies had been created by implantation and that these defects are most effectively cured after annealing in oxygen atmosphere. AFM analysis was used to determine the surface-morphology changes after the implantation and annealing procedures. The as-implanted samples exhibited ferromagnetism persisting up to room temperature. The annealing procedure led to paramagnetic behaviour, probably caused by the formation of gadolinium clusters.

Two shallow donors related to Zn interstitial in S-ion implanted ZnO epitaxial film

Two shallow donors are observed in sulfur-ion implanted ZnO epitaxial films on sapphire substrates. The resistivity varies from ~103Ωcm for un-implanted samples to 1.7×10−2Ωcm for as-implanted ones. This low resistivity is attributed to zinc interstitial (Zni), corresponding to the activation energy (26meV) estimated from the temperature dependence of electron concentration. The presence of Zni is evaluated from ion channeling by Rutherford backscattering spectroscopy. The disordered concentration is ~40% of Zn atoms at a maximum point (300nm) from the surface in as-implanted samples and recovers to ~80% after 1000°C annealing. In 1000°C annealed samples, a shallower donor level of 12meV is observed, suggesting the presence of complex defects consisting of remaining Zni and sulfur atoms replaced to the oxygen atom.

Characterization of in-depth cavity distribution after thermal annealing of helium-implanted silicon and gallium nitride

Single-crystalline silicon wafers covered with sacrificial oxide layer and epitaxially grown gallium nitride layers were implanted with high-fluence helium ions (2–6×1016cm−2) at energies of 20–30keV. Thermal annealings at 650–1000°C, 1h were performed on the Si samples and rapid thermal annealings at 600–1000°C, 120s under N2 were performed on the GaN samples. The as-implanted samples and the near-surface cavity distributions of the annealed samples were investigated with variable angle spectroscopic ellipsometry. In-depth defect profiles and cavity profiles can be best described with multiple independent effective medium sublayers of varying ratio of single-crystal/void. The number of sublayers was chosen to maximize the fit quality without a high parameter cross-correlation. The dependence of the implantation fluence, oxide layer thickness and annealing temperature on the cavity distribution was separately investigated. The ellipsometric fitted distributions were compared and cross-checked with analyses of transmission electron micrographs where the average surface cavity was determined sublayer by sublayer. The in-depth profiles were also compared with simulations of He and vacancy distributions.

Luminescence of a titanate compound under europium ion implantation

The ability to incorporate europium ions in a near-surface layer of a nonlinear optical material KTiOPO4 by ion implantation is reported here. Europium diffusion as well as surface modification were characterized after annealing using RBS. The photoluminescence of the as-implanted samples indicates that the creation of defects gives rise to green visible emission centered about 550nm. Annealing up to 1000°C does not allow the oxidation to the 3+ valence state of the europium ion. However it is shown that annealing up to such high temperature gives rise to an intense near infra-red photoluminescence in the range 800–1100nm in implanted samples at an optimal fluence of 2×1013 europium ions/cm2.

ZnO Nanoparticle Formation in Si by Co-Implantation of Zn<sup>+</sup> and O<sup>+ </sup>Ions

ZnO nanoparticles (NPs) formed in Czochralski-grown n-type (100) silicon substrates have been studied. The NPs were formed by co-implantation of 64Zn+ and 16O+ ions followed by furnace annealing in neutral/inert atmospheres for 1h. High-resolution transmission electron microscopy (HR TEM) of cross-section samples enabled the structural properties of the near surface layers to be characterized after implantation and annealing. The distribution of implant profiles was analyzed by secondary ion mass-spectrometry (SIMS). The surface morphology was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Identification of the phase content of the materials was carried out by high-resolution X-ray diffraction in θ-2θ scanning mode. In as-implanted samples, a big amorphous layer was formed which destroyed the NPs beneath the surface. After furnace annealing from 600 up to 800°C, ZnO(102) NPs with a size of ~7nm were formed in the recrystallization layer. Furnace annealing at temperatures above 900 °C gave rise to a restructuring of the silicon surface and ZnO NPs formed on the sample surface. At temperatures above 1000 °C, out-diffusion of Zn from the sample occurred due to the large diffusion coefficient Zn at these temperatures.

Influence of the hydrogen implantation power density on ion cutting of Ge

In this work, surface morphologies, strain status, and defect evolution were investigated for Ge wafers after hydrogen implantation with different implantation power densities. Hydrogen implantation generates strain in the Ge lattice at lower implantation power densities, and this strain is crucial for a successful ion cut. At higher implantation power densities, the strain is relaxed and mosaic structures are seen in the as-implanted samples, where platelet defects grow, propagate, and coalesce owing to the self-annealing effect during hydrogen implantation. This defect evolution behavior results in either no blistering or formation of discrete blisters after annealing of the implanted Ge samples, rather than the desired ion cut.

Depth Profiling of Electronic Transport Parameters in n-on-p Boron-Ion-Implanted Vacancy-Doped HgCdTe

We report results of a detailed study of electronic transport in n-on-p junctions formed by 150-keV boron-ion implantation in vacancy-doped p-type Hg0.769Cd0.231Te without postimplantation thermal annealing. A mobility spectrum analysis methodology in conjunction with a wet chemical etching-based surface removal approach has been employed to depth profile the transport characteristics of the samples. In the as-implanted samples, three distinct electron species were detected which are shown to be associated with (a) low-mobility electrons in the top 220-nm surface-damaged layer (E1: μ80K = 2940 cm2/Vs), (b) the B-ion implantation region in the top 500-nm region (E2: μ80K = 7490 cm2/Vs), and (c) high-mobility electrons in the n-to-p transition region at a depth of 600 nm to 700 nm (E3: μ80K = 25,640 cm2/Vs). Due to the maximum magnetic field employed (2 T), hole carriers from the underlying vacancy-doped p-type region were detected only after the removal of the top 220 nm of the profiled sample (μ80K = 126 cm2/Vs), revealing fully p-type character 800 nm below the original sample surface. A comparison of the extracted E2 electron concentration and calculated B-impurity profile suggests that the n-type region is due primarily to near-surface implantation-induced lattice damage.

Positron annihilation Doppler broadening study of Xe-implanted aluminum

Positron annihilation Doppler broadening measurements were conducted to characterize information of defects in 380keV Xe+-implanted aluminum upon thermal annealing at temperatures ranging from 100 to 600°C. The results suggest a broad distribution in the depth of vacancy-type defects in all the as-implanted samples. Meanwhile, with an increase in implantation dose the defect-rich region shifts toward the sample surface. It was found that increasing the annealing temperature triggers surface-directed migration and coalescence of vacancy and XenVm clusters in samples with implantation doses of 1E15 and 1E16 Xe+cm−2. In the sample implanted with a high dose of 1E17 Xe+cm−2, positron annihilation revealed a decomposition and even elimination of such defects under post-implantation annealing treatment.

Ion beam synthesis and carrier dynamics of ZnO nanoparticles embedded in a SiO2 matrix

Zinc oxide (ZnO) nanostructures have been synthesized by the implantation of ZnO molecular ions into SiO2 followed by high temperature thermal annealing. 35 keV ZnO− ions were implanted to a fluence of 5×1016 ions/cm2 into SiO2 at room temperature (RT). The implanted sample was annealed in an oxygen environment to allow the growth of ZnO precipitates. In the as-implanted sample, Zn nanoparticles up to 4.5 nm in diameter were observed and were distributed throughout the implanted depth in the SiO2. The highest concentration of Zn from the implantation was at a depth of 25 nm. During annealing, Zn diffused into the substrate and combined with oxygen to form ZnO. ZnO nanostructures thus formed had diameters up to 8 nm, embedded in SiO2. Donor-bound exciton (D, X), acceptor-bound exciton (A, X), and donor–acceptor-pair (DAP) transitions were observed in low temperature photoluminescence (PL) measurements on an annealed sample. RT-PL measurement showed band-edge emission in the ultraviolet region with a full width at half maximum of 121 meV. Time-resolved PL measurements performed at 4 K revealed an excitonic lifetime of 160 ps.

Annealing behavior of impurities and defects in keV Er-implanted ZnO bulk single crystals

We have investigated the effect of implantation and annealing temperatures on crystalline quality, disorder recovery and dopant distribution in ZnO bombarded with Er ions using Rutherford backscattering/channeling spectrometry. The channeling results indicate that the damage retains a low level in as-implanted samples due to the dynamic annealing effect during implantation at 600°C. It is also found that the implantation disorder is well recovered when the samples are annealed at 1000°C for 30min. The results also demonstrate that many Er ions diffuse towards the surface during the whole annealing program. In particular, Er is distributed almost randomly after annealing at 1000°C for 30min.

Characterization of the lattice defects in Ge-ion implanted ZnO bulk single crystals by Rutherford Backscattering: Origins of low resistivity

A Ge ion implantation using a multiple-step energy into ZnO bulk single crystals is performed (net concentration: 2.6×1020cm−3). The origins of low resistivity of the Ge implanted ZnO samples are studied by Rutherford backscattering spectroscopy (RBS), photoluminescence (PL). The resistivity measured by Van der Pauw method decreases from ∼103Ωcm for the un-implanted samples to 1.45×10−2Ωcm for the as-implanted samples, originating from the lattice displacement of Zn (Zni) (∼30meV [Look et al., Phys. Rev. Lett. 82, 2552 (1999)]), the existence of which is revealed by the RBS measurements. In contrast, the 1000°C annealed samples show the higher resistivity of 6.26×10−1Ωcm, indicating that the Zni related defects decrease but still remain despite the annealing. A new PL emission appears at around 372nm (3.33eV) in the annealed samples, suggesting a Ge donor with an activation energy of 100meV. This value corresponds to the activation energy (102meV) of a Ge donor estimated from the temperature dependence of carrier concentration. These results suggest that the resistivity in the 1000°C annealed samples results from both the Zni related defects and the electrically activated Ge donor.

Photoluminescence investigation of erbium-implanted in KTiOPO4 and RbTiOPO4

KTiOPO4 (KTP) and RbTiOPO4 (RTP) crystals have been implanted with 500keV Er ions at a dose of 3×1015ions/cm2 with the aim of optically doping the material in the near surface region. The sample was annealed at 500°C for 90min in oxygen atmosphere after implantation. Photoluminescence (PL) and Rutherford backscattering spectrometry studies were performed on the as-implanted samples before and after annealing. 1.54μm photoluminescence emission was observed at both room-temperature and low-temperature in KTP without any annealing. After annealing luminescence intensity is improved at 12K and photoluminescence quenching were found at room temperature for both samples. The reasons are discussed in the paper.