High-fluence Ion Implantation Research Articles

Ion-Beam Synthesis of Structure-Oriented Iron Nanoparticles in Single-Crystalline Rutile TiO2

Magnetic nanoparticles embedded into semiconductors have current perspectives for use in semiconducting spintronics. In this work, 40 keV Fe+ ions were implanted in high fluences of (0.5 ÷ 1.5) × 1017 ion/cm2 into an oxide semiconductor and single-crystalline TiO2 plates of rutile structure with (100) or (001) face orientations. Microstructure, elemental-phase composition, and magnetic properties of the Fe-ion-implanted TiO2 were studied by scanning and transmission electron microscopies (SEM and TEM), X-ray photoelectron (XPS) and Rutherford backscattering (RBS) spectroscopies, as well as vibrating-sample magnetometry (VSM). The high-fluence ion implantation results in the formation of magnetic nanoparticles of metallic iron beneath the irradiated surface of rutile. The induced ferromagnetism and observed two- or four-fold magnetic anisotropy are associated with the endotaxial growth of Fe nanoparticles oriented along the crystallographic axes of TiO2.

Formation of ZnSe Nanoclusters in Silicon Dioxide Layers by High-Fluence Ion Implantation: Experimental Data and Simulation Results

Formation of ZnSe Nanoclusters in Silicon Dioxide Layers by High-Fluence Ion Implantation: Experimental Data and Simulation Results

Endotaxial α-Fe Nanoparticles in the High-Fluence Iron-Implanted Single-Crystal MgO

In this work, we report on the endotaxial growth of α-Fe nanoparticles in the near-surface layer under high-fluence iron ion implantation of the single-crystal magnesium oxide substrate. Comprehensive Mössbauer effect and magnetometry studies show that the implanted sample reveals a pronounced ferromagnetic response even at room temperature, and the α-Fe nanoparticles serve as its main source. The broad band at ~1000 Oe in the X-band magnetic resonance spectra originates from the α-Fe fraction. It manifests the properties of the easy-plane system with the four-fold in-plane anisotropy. The last indicates that the α-Fe nanoparticles are coherently incorporated into the host MgO matrix.

Fluence effect on photo- and electroluminescence of silica layers implanted with Sn+ ions

High-fluence ion implantation has been applied to create silica-based light-emitting nanocomposite for silicon photonics. Samples of SiO2/Si have been implanted with Sn ions (80 keV, 2.5 × 1016 cm−2, 5 × 1016cm−2 and 1 × 1017 ion/cm2) and afterwards annealed at 900 °C for 60 min in air ambient. The intense violet band at 3.2 eV dominates in photoluminescence (PL) end electroluminescence (EL) spectra. Its intensity decreases with the Sn concentration increase in silica. Besides, the PL spectra exhibit orange band which quenches after passing a charge flow (0.35C/cm2) through the samples. The origin of the observed emission as well as its degradation mechanisms are discussed.

Effect of 60 keV argon ion implantation in Makrofol® DE 1-1 on the optical properties

Ion implantation in polymeric materials has recently attracted considerable attention in various technology and science fields. The effect of 60 keV low-energy and high-fluence argon ion implantation in the Makrofol® DE 1-1 polymer on the nonlinear and linear optical properties was investigated. Structural changes of the polymer were studied with Raman spectroscopy to ensure the structural modifications induced by argon ions. Linear optical parameters such as the absorption and refractive index were investigated for the ion-implanted sheets. Direct and indirect optical band gaps were observed to decrease with an increase in argon ion fluence. In addition, an increase in the optical conductivity was found with increasing number of ions implanted in the sheets. The photoluminescence (PL) measurements reveal enhanced PL intensity of higher-fluence ion implanted in contrast to the PL of lower ion implantation fluence. Additionally, nonlinear absorption and optical limiting were investigated via the Z scan technique. The implanted materials have saturable nonlinear absorption, the nonlinear absorption coefficients and the figure of merit were calculated for the investigated samples, and the results show that the implanted argon ion Makrofol is a good candidate for saturable absorbers, optoelectronic devices and medical products.

Optical properties of porous GaAs formed by low energy ion implantation

We report about chemical, structural and optical characteristics of porous GaAs near-surface layers formed by low energy and high fluence ion implantation of Si+ and Ge+ ions. The energy of implanted ions was 25 keV and the ion dose was 2 × 1016 ion⋅cm−2 for both species. After implantation, experimental samples were annealed under N2 atmosphere resulting in the increment of porosity. The chemical properties of the samples were studied by SIMS and Raman spectroscopy. The Raman spectroscopy was used as well for examining the presence of amorphous phase in a near surface layer caused by ion implantation. The porous GaAs demonstrates visible photoluminescence under ultraviolet excitation. Optical reflection coefficient radically decreases after implantation due to the porous layer formation. The size and in-depth distribution of pores were analyzed by AFM in combination with controlling Ar+ ion etching. Our findings, let us suggests that ion implantation can be used as a reliable technique to prepare porous semiconductors with potential applications for fabrication of optoelectronic devices. The mechanism of pores formation and growth during ion implantation in semiconductors and post-implantation annealing is discussed.

Thermal Annealing Effect on Structure and Properties of Tungsten Surface Irradiated with High Fluence and Low Energy Alpha-Particles

The paper presents research into the surface morphology, helium cluster formation and mechanical properties of high-purity tungsten after the high fluence and low-energy helium ion implantation and subsequent annealing. Investigations are based on scanning electron and atomic force microscopy observations and thermal desorption measurements. Because of the local stresses appearing within the energy loss straggling of helium ions, atoms migrate at distances significantly increasing the ion projective range, and create mobile coalescence of helium atoms and immobile helium-vacancy clusters. The latter form helium bubbles in the energy loss straggling which cause the surface blistering. Local stresses induced by helium coalescence and helium-vacancy clusters beyond the energy loss straggling result in the material strengthening or hardness increase. Subsequent 600°С annealing provides the size growth of blisters on the metal surface irradiated with helium ions and high helium desorption due to the migration of mobile coalescence of helium atoms. With the increasing annealing temperature from 600 to 1000°С, the layer corresponding to the projective range of helium ions fully fractures due to the interstitial helium atoms releasing from immobile helium-vacancy clusters. After 1000°С annealing, the tungsten hardness returns to its initial value.

Formation of ZnSe nanoclusters in the layers of silicon dioxide by high-fluence ion implantation and annealing

In this work we used the method of hot implantation of zinc and selenium ions into SiO2/Si structures in combination with subsequent heat treatment in order to form nanosized phases. Implantation modes for ionic synthesis chosen in such a way that the concentration of the embedded impurity is maximum approximately at the middle of the thickness of the dielectric layer. For the subsequent clustering of the impurity, it is necessary to create a high concentration of the implanted impurity at the maximum of the depth profile. The computer stimulation to select Implantation modes was carried out using the SRIM- 2013 program. Also we calculated the thickness of the silicon dioxide layer sprayed during high-dose implantation of zinc ions was. In this way, we have studied the formation of ZnSe precipitates in silicon dioxide by means of Zn (150 keV, 4×1016 cm−2) and Se (170 keV, 4×1016 cm−2) implantation at 550 °C and subsequent annealing at 1000 °C for 3 min. From analysis of XTEM images it has been showen that the use of hot implantation leads to the formation of small nanoclusters with sizes from 2 to 15 nm. Subsequent annealing results in the redistribution of nanoclusters within the implanted layer and the formation of large crystallites (up to 80 nm). To analyze the distribution of the introduced impurity throughout the sample depth the Rutherford backscattering (RBS) method was used. The band at 251-256 cm-1 associated with LO phonons of crystal ZnSe was registered in Raman spectra.

Lithium implanted into diamond: Regular trends and anomalies

Diamond single crystals implanted with 7Li+ ions within broad range of fluences including those higher graphitization threshold were studied by secondary ion mass spectrometry (SIMS) and optical interference profilometry. It has been shown that sputtering coefficient of diamond does not depend on the level of radiation damage and on the microstructure of the material, which may be due to the formation of an amorphous layer on the surface during the ion bombardment. Graphitization domains were observed immediately after high-fluence ion implantation, prior to annealing. No diffusion of implanted lithium (at any fluences) was observed in diamond both at high-temperature treatment and under strong photothermal excitation near the ablation threshold. SIMS measurements have shown sharp decrease of lithium ion yield in strongly damaged diamond, particularly in graphitized region, which has not yet been satisfactorily explained.

Nano-Crystal Formation and Growth from High-Fluence Ion Implantation of Au, Ag or Cu in Silica

The linear and non-linear optical properties of silica may be tailored by the introduction of a random distribution of nanocrystallites of an immiscible metal within a near-surface region. The size, size distribution, and spatial distribution of these crystallites must be controllable in order to optimize the functional properties for device applications. In this paper, we present a novel fabrication technique that offers such control. Energetic metal ions are implanted in silica at room temperature. Subsequent heat treatment leads to diffusion of the implanted atoms, nucleation and growth of metal crystallites, and Ostwald ripening of the resulting clusters. We have observed the kinetics and effective activation energies describing the multiple processes involved, for the cases of Au, Ag or Cu implanted at MeV energies, at various fluences, and then annealed at fixed temperatures in the range 500°C-1000°C. Effective activation energies found for nanocrystal nucleation and growth at temperatures below 800°C (e.g. 64 meV for Ag) are replaced above this temperature range by much higher activation energies (e.g. 400 meV for Ag). We may attribute this to the depletion of un-attached mobile metal atoms (so that ripening of clusters will be limited by energy barriers for escape of such mobile atoms from small crystallites), and/or the annealing of implant-caused stress in the silica structure at high temperatures, that creates new channels for thermal diffusion of metal atoms within the silica host.

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.

Improved ion implant fluence uniformity in hydrogen enhanced glow discharge plasma immersion ion implantation into silicon.

Enhanced glow discharge plasma immersion ion implantation does not require an external plasma source but ion focusing affects the lateral ion fluence uniformity, thereby hampering its use in high-fluence hydrogen ion implantation for thin film transfer and fabrication of silicon-on-insulator. Insertion of a metal ring between the sample stage and glass chamber improves the ion uniformity and reduces the ion fluence non-uniformity as the cathode voltage is raised. Two-dimensional multiple-grid particle-in-cell simulation confirms that the variation of electric field inside the chamber leads to mitigation of the ion focusing phenomenon and the results are corroborated experimentally by hydrogen forward scattering.

Surface Plasmon Resonance in Ag Nanoparticles Synthesized in Silica Glass by Low-Energy High-Fluence Ion Implantation

Surface Plasmon Resonance in Ag Nanoparticles Synthesized in Silica Glass by Low-Energy High-Fluence Ion Implantation

Transformation of YSZ under high fluence argon ion implantation

In this work, we present the effect of extremely high fluence ion implantation on microstructure of single crystalline YSZ samples with three major low index orientations: (100), (110) and (111). The samples were implanted at room temperature with 150keV Ar+ ions to a fluence of 1×1017Ar/cm−2 corresponding to the peak damage level of ∼120dpa and peak Ar atom concentration of ∼12at.%. Rutherford backscattering/channeling spectrometry (RBS/C), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and associated analytical tools were used to determine the orientation dependent damage, surface morphology, and microstructure modifications of the implanted layers. Ar+ ion implantation resulted in formation of severely damaged layers, which however remained crystalline. The damage peak maximum, determined by RBS/C, indicated that the fourth damage accumulation stage, previously predicted for Ar-implanted YSZ, was achieved. The (110) oriented YSZ demonstrated slightly better radiation tolerance, as observed by RBS/C, compared to the other low index orientations. Microstructural studies revealed large cavities aligned parallel to the specimen surface, which emerged in a form of circular blisters on the surface. The origin of the cavities was related to the segregation of Ar atoms into pressurized gas filled bubbles. The crystallographic anisotropy of microstructural parameters (thickness of the damages layer, surface blister density and diameter, cavity dimensions) remains uncertain.

Ion-beam synthesis and characterization of narrow-gap A3B5 nanocrystals in Si: Effect of implantation and annealing regimes

The process of InAs and GaSb nanoprecipitates creation in Si matrix using high-fluence ion implantation of species from groups V and III followed by thermal treatment has been investigated. We have studied in detail a complex system of defects and nanocrystals in implanted layers, have compared a damage level for both systems, evaluated the influence of implantation and annealing regimes on a size of A3B5 nanocrystals and on a defect distribution in implanted layers. The crystalline nature of precipitates was identified by observing Moiré fringe patterns in TEM images, the Moiré period showing a tendency to increase with increasing size of inclusion. A “glowing” effect was observed at the nanocrystal/Si interfaces in the dark-field TEM images of the implanted and annealed samples, this being ascribed to the presence of misfit dislocation networks at the InAs/Si and GaSb/Si interfaces generated as a result of strain relaxation in the highly mismatched A3B5/Si systems. Also we compared our results on structural characterization of “A3B5 nanocrystals–Si matrix” systems with other papers.

Thermal instability of pseudomorphically strained phosphorus doped Si:C alloy

We study the thermal stability of P doped and undoped pseudomorphically strained Si:C alloy formed by high fluence ion implantation and subsequent solid phase epitaxial regrowth (SPER), under post-annealing conditions far below the β-SiC precipitation threshold. The strain is measured by high resolution X-ray diffractometer (HRXRD) and kinematic simulation. By plotting the differential strain relaxation with respect to post-annealing time, we found much lower deactivation energy at the near surface region while the presence of high P concentration results in more significant strain relaxation. We explain the near surface relaxation by considering the interstitials injection by surface oxide formations during the post annealing process. P in the bulk on the other hand plays the role as additional interstitial kick-out mediator and lowers the thermal stability.

High-energy heavy ion beam annealing effect on ion beam synthesis of silicon carbide

Silicon carbide (SiC) is a superior material potentially replacing conventional silicon for high-power and high-frequency microelectronic applications. Ion beam synthesis (IBS) is a novel technique to produce large-area, high-quality and ready-to-use SiC crystals. The technique uses high-fluence carbon ion implantation in silicon wafers at elevated temperatures, followed by high-energy heavy ion beam annealing. This work focuses on studying effects from the ion beam annealing on crystallization of SiC from implanted carbon and matrix silicon. In the ion beam annealing experiments, heavy ion beams of iodine and xenon, the neighbors in the periodic table, with different energies to different fluences, I ions at 10, 20, and 30 MeV with 1–5 × 10 12 ions/cm 2, while Xe ions at 4 MeV with 5 × 10 13 and 1 × 10 14 ions/cm 2, bombarded C-ion in implanted Si at elevated temperatures. X-ray diffraction, Raman scattering, infrared spectroscopy were used to characterize the formation of SiC. Non-Rutherford backscattering and Rutherford backscattering spectrometry were used to analyze changes in the carbon depth profiles. The results from this study were compared with those previously reported in similar studies. The comparison showed that ion beam annealing could indeed induce crystallization of SiC, mainly depending on the single ion energy but not on the deposited areal density of the ion beam energy (the product of the ion energy and the fluence). The results demonstrate from an aspect that the electronic stopping plays the key role in the annealing.

On artefacts in the secondary ion mass spectrometry profiling of high fluence H+ implants in GaAs

Abstract High fluence (>1017 H/cm2) ion implantation of H in GaAs is suitable for the ion cut process, and produces H bubbles under the surface which may cause blistering. By comparing the destructive depth profiling of these implants by secondary ion mass spectrometry (SIMS) with non-destructive profiling by elastic recoil detection analysis (ERD), we demonstrate that SIMS underestimates total H content by up to a factor of 2 due to undetected H escaping from bubbles during analysis. We also show that the depth of the maximum H concentration from SIMS can be in error by 20% due to large variations in the sputter rate through the profile.

Magnetoresistive Effect in PET Films with Iron Nanoparticles Synthesized by Ion Implantation

Thin polyethyleneterephthalate (PET) layers with Fe nanoparticles (NPs) were synthesized by high-fluence ion implantation. Temperature dependence of conductance and magnetoresistance, were studied as a function of ion fluence. It is found that the implantation with fluences of about 1.0×10 17 cm -2 causes high enough concentration of metal inclu- sions to provide conditions for electrical percolation that leads to an insulator-to-metal transition (IMT) in charge carrier transport mechanisms. The magnetoresistance measurements indicate that the magnetic percolation takes place at metal concentrations (fluences) lower than those needed for the electrical percolation. For the samples on insulating side of the IMT, a non-monotonous dependence of resistance in an increasing external magnetic field is observed due to anisotropic magnetoresistive effect and charge carrier scattering on magnetic inclusions. For the samples implanted with fluences ≥ 1.0×10 17 cm -2 , the magnetoresistance becomes a monotonous decreasing function of the external magnetic field which is typical for ferromagnetic metals that indicates effective magnetic coupling of the iron inclusions.

Study of structure and surface modification of silicon-on-insulator (SOI) devices synthesized by dual ion implantation

Silicon oxynitride (Si xO yN z) buried layers were synthesized by high fluence (≥ 1 × 10 17 ions-cm − 2 ) ion implantation of O + and N + sequentially into single crystal silicon at 150 keV to produce silicon-on-insulator (SOI) structures. The structures of the SOI devices were analyzed by FTIR and XRD measurements and the surface modification by using atomic force microscopy (AFM). The FTIR measurements on the implanted samples (≤ 1 × 10 18 ion-cm − 2 ) show a single absorption band in the wavenumber range 1300–750 cm − 1 attributed to the formation of silicon oxynitride bonds in silicon. The integrated absorption band intensity is found to increase with increase in the fluence. The samples with nitrogen–oxygen sequence of implantation showed nitrogen-rich oxynitride formation whereas samples with oxygen–nitrogen sequence resulted in oxygen-rich oxynitride. The formation of separate phases of Si–O and Si–N bonds was observed at high fluence level (≅ 2 × 10 18 ions-cm − 2 ). The XRD studies show the formation of mixed phases of Si 2N 2O and SiO 2 in the sample. The structures of the ion beam synthesized silicon oxynitride layers are found to be strongly dependent on the sequence of implantation. The surface roughness is observed to be very small at lower fluences and it increases as we go to high fluence levels due to heavy damage caused by implantation. The conical hill like structures on the silicon surface is seen due to heavy surface swelling and sputtering phenomena.