Pulsed Ion Implantation Research Articles

Numerical Simulation of Thermal Processes and the Effect of Heating of Near-Surface Layers of Titanium on the Diffusion Transfer of Dopants during High-Intensity Pulsed Ion Implantation

Numerical Simulation of Thermal Processes and the Effect of Heating of Near-Surface Layers of Titanium on the Diffusion Transfer of Dopants during High-Intensity Pulsed Ion Implantation

High Dielectric Transparent Film Tailored by Acceptor and Donor Codoping.

High dielectric constant materials are of particular current interests as indispensable components in transistors, capacitors, etc. In this context, there are emerging trends to exploit defect engineering in dielectric ceramics for enhancing the performance. However, demonstrations of similar high dielectric performance in integration-compatible crystalline films are rare. Herein, such a breakthrough via the functionalization of donor-acceptor dipoles by compositional tuning in GaCu codoped ZnO films is reported. The dielectric constant reaches ~200 at 1kHz and the optical transmittance in visible light reaches ~80%. Importantly, by analyzing the impedance spectroscopy data, prominent relaxation mechanisms in correlation with the dipole properties, enabling consistent explanations of the dielectric constant as a function of frequency are discriminated. The atomistic nature of the dipoles is revealed by the systematic X-ray spectroscopy analysis. Spectacularly, similar trends for the dielectric properties are observed, while synthesizing samples by pulsed laser deposition and ion implantation, indicating the general character of the phenomena.

A high-k Cu-doped ZnO film formed via Ga-ion implantation: The acceptor-donor co-doping approach

Dielectric thin films having high permittivity (high-k) and low dielectric loss is essential for developing high performance capacitive devices like metal oxide field effect transistor or thin film transistor. Ga ion implantation performed on Cu-doped ZnO film fabricated by pulsed laser deposition with optimized doping concentrations and post-implantation annealing yielded film having high permittivity and low dielectric loss (ε = 87 and tan δ = 0.17 at the frequency of 1 kHz). Moreover, the permittivity exhibits good stability over a wide range of frequency from 20 Hz to 10 MHz. The high-k film was characterized by detailed dielectric studies, including frequency dependence of permittivity and dielectric loss, complex electrical modulus analysis, impedance spectroscopy and ac conductivity. The enhancement of the permittivity was attributed to the correlated potential barrier hopping of electrons between the neighboring acceptor-donor defect complex states in the band gap created by the co-doping, thus acting as electric dipoles polarizing the film. This work opens up future possibility for ‘dielectric engineering’. The three-dimensional dielectric spatial profile can be controlled via the selective area ion implantation with the depth controlled by the ion implantation energy. • A high-k Ga-Cu co-doped ZnO film formed via pulsed laser deposition and ion implantation method. • Optimized doping concentrations yielded high permittivity and low dielectric loss (ε=87 and tan δ=0.17 at 1 kHz). • Enhancement of permittivity was attributed to the correlated barrier hopping of electrons between neighboring defect complex.

Fabrication of metal-dielectric nanocomposites using a table-top ion implanter

A miniature low-voltage vacuum spark is an effective facility for creating composite layers in a dielectric matrix, including metal clusters, which have numerous optical applications. The results of studies of the optical characteristics of alkali-halide crystals (LiF and KCl) irradiated with beams of accelerated metal ions, which are emitted by a small-sized, low-voltage (2.5 kV) and low-energy (10 J) vacuum spark and a high-voltage (50 kV) pulsed ion implanter are presented. In both cases, composite layers of metal nanoparticles and/or molecular clusters are formed at submicrometer depth when irradiating these crystals. The low voltage implant method produces similar optical effects as seen in crystals processes at much higher energies. This result shows the possibility of creating a desktop metal ion implanter for various applications.

Creation of Si quantum dots in a silica matrix due to conversion of radiation defects under pulsed ion-beam exposure.

In this work we present an innovative method of creating Si quantum dots under pulsed ion-beam exposure. The evolution of defect structure ODC(II) → E'→ ODC(I) → Si QDs in glassy SiO2 under ion-beam implantation was established by optical absorption and photoluminescence spectroscopies. Depending on the mode of ion exposure, it is possible to easily control the type and concentration of defects in the host and modify its optical properties for novel applications. Ab initio calculations confirm that bond softening in SiO2 is attainable via the use of Gd ion implantation. According to our experimental and theoretical results, the three-stage interaction of primary oxygen-deficient centers leads to the formation of stable silicon quantum dots with a size of 3.6 nm and luminescence at 1.8 eV excited by incoherent light.

Enhanced clustering tendency of Cu-impurities with a number of oxygen vacancies in heavy carbon-loaded TiO2 - the bulk and surface morphologies

The over threshold carbon-loadings (∼50 at.%) of initial TiO2-hosts and posterior Cu-sensitization (∼7 at.%) was made using pulsed ion-implantation technique in sequential mode with 1 h vacuum-idle cycle between sequential stages of embedding. The final Cx-TiO2:Cu samples were qualified using XPS wide-scan elemental analysis, core-levels and valence band mappings. The results obtained were discussed on the theoretic background employing DFT-calculations. The combined XPS-and-DFT analysis allows to establish and prove the final formula of the synthesized samples as Cx-TiO2:[Cu+][Cu2+] for the bulk and Cx-TiO2:[Cu+][Cu0] for thin-films. It was demonstrated the in the mode of heavy carbon-loadings the remaining majority of neutral C–C bonds (sp3-type) is dominating and only a lack of embedded carbon is fabricating the O–CO clusters. No valence base-band width altering was established after sequential carbon-copper modification of the atomic structure of initial TiO2-hosts except the dominating majority of Cu 3s states after Cu-sensitization. The crucial role of neutral carbon low-dimensional impurities as the precursors for the new phases growth was shown for Cu-sensitized Cx-TiO2 intermediate-state hosts.

The influence of repetitively pulsed plasma immersion low energy ion implantation on TiN coating formation and properties

Application of high frequency short pulse plasma immersion low energy ion implantation for titanium nitride coating deposition using vacuum arc metal plasma and hot-cathode gas-discharge plasma on R6M5 alloy was investigated. Implementation of negative repetitively pulsed bias with bias amplitude 2 kV, pulse duration 5 μs and pulse frequency 105 Hz leads to 6.2-fold decrease of vacuum arc macroparticle surface density for macroparticles with diameter less than 0.5 μm. Ion sputtering due coating deposition reduces the production rate approximately by 30%. It was found that with bias amplitude range from 1.1 to 1.4 kV and pulse duration 5 μs yields to formation of coatings with local hardness up to 40 GPa. This paper presents the results of experimental studies of adhesion strength, tribological properties and surface morphology of deposited TiN coatings.

Soft electronic structure modulation of surface (thin-film) and bulk (ceramics) morphologies of TiO2-host by Pb-implantation: XPS-and-DFT characterization

The results of combined experimental and theoretical study of substitutional and clustering effects in the structure of Pb-doped TiO2-hosts (bulk ceramics and thin-film morphologies) are presented. Pb-doping of the bulk and thin-film titanium dioxide was made with the help of pulsed ion-implantation without posterior tempering (Electronic Structure Modulation Mode). The X-ray photoelectron spectroscopy (XPS) qualification of core-levels and valence bands and Density-Functional Theory (DFT) calculations were employed in order to study the yielded electronic structure of Pb-ion modulated TiO2 host-matrices. The combined XPS-and-DFT analysis has agreed definitely with the scenario of the implantation stimulated appearance of PbO-like structures in the bulk morphology of TiO2:Pb, whereas in thin-film morphology the PbO2-like structure becomes dominating, essentially contributing weak O/Pb bonding (PbxOy defect clusters). The crucial role of the oxygen hollow-type vacancies for the process of Pb-impurity “insertion” into the structure of bulk TiO2 was pointed out employing DFT-based theoretical background. Both experiment and theory established clearly the final electronic structure re-arrangement of the bulk and thin-film morphologies of TiO2 because of the Pb-modulated deformation and shift of the initial Valence Base-Band Width about 1eV up.

Pleomorphic structural imperfections caused by pulsed Bi-implantation in the bulk and thin-film morphologies of TiO2

The results of combined experimental and theoretical study of pleomorphic substitutional and clustering effects in Bi-doped TiO2 hosts (bulk and thin-film morphologies) are presented. Bi-doping of the bulk and thin-film titanium dioxide was made with help of pulsed ion-implantation (EBi+=30 keV, D=1×1017cm−2) without posterior tempering. The X-ray photoelectron spectroscopy (XPS) qualification (core-levels and valence bands) and Density-Functional Theory (DFT) calculations were employed in order to study the electronic structure of Bi-ion implanted TiO2 samples. According to XPS data obtained and DFT calculations, the Bi→Ti cation substitution occurs in Bi-implanted bulk TiO2, whereas in the thin-film morphology of TiO2:Bi the Bi-atoms have metal-like clusters segregation tendency. Based on the combined XPS and DFT considerations the possible reasons and mechanism for the observed effects are discussed. It is believed that established peculiarities of bismuth embedding into employed TiO2 hosts are mostly the sequence of pleomorphic origin for the formed “bismuth–oxygen” chemical bonding.

Pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium

The results from investigating the pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium are presented. It is shown that variations in the elemental and phase composition of surface layers, their microscopic characteristics, and their mechanical properties as a function of implantation time are not monotonous but follow certain patterns. The possibility of interpreting the obtained data in terms of surface modification by metallic clusters with at least ~100 atoms generated in the gas of metal atoms evaporated from cathode spots is discussed.

Octahedral conversion of a-SiO2 host matrix by pulsed ion implantation

XPS measurements and DFT calculations are supported by Russian Science Foundation (Grant no. 14-22-00004). The preparation of a-SiO 2 samples and ion-implantation treatment are supported by Deutsche Forschungsgemeinschaft-DFG (German Research Foundation Project FI 497/15-1) and the Russian Ministry of Science and Education (Government Task 3.2016.2014/K).

XPS and DFT study of Sn incorporation into ZnO and TiO2host matrices by pulsed ion implantation

Bulk and thin films ZnO and TiO2 samples were doped with Sn by pulsed ion implantation and studied by means of X-ray photoelectron core-level and valence band spectroscopy as well as density functional theory calculations for comprehensive study of the incorporation of Sn. XPS spectral analysis showed that isovalent Sn cation substitution occurs in both zinc oxide (Sn2+ -> Zn2+) and titanium dioxide (Sn4+ -> Ti4+) for bulk and film morphologies. For TiO2 films, the implantation also led to occupation of interstitials by doped ions, which induced the clustering of substituted and embedded Sn atoms; this did not occur in ZnO:Sn film samples. Density functional theory (DFT) formation energies were calculated of various incorporation processes, explaining the prevalence of substitutional defects in both matrices. Possible mechanisms and reasons for the observed trends in Sn incorporation into the ZnO and TiO2 matrices are discussed.

Study of the plasma immersion implantation of titanium in stainless steel

The results of the study of the pulsed plasma-immersion ion implantation of titanium in steel Cr18Ni10Ti depending on the time (dose) implantation are presented. It is shown that the change of the element and the phase composition of the surface layers and their microscopic characteristics and mechanical properties (hardness, wear resistance) depending on the implantation time is not monotonic, but follows to a certain rule. The possibility of interpretation of the obtained results in the thermal spike concept of the generation on the surface by the stable (magic) clusters is discussed. This concept follows logically from the recent studies on the plasma arc composition and from a polyatomic clusters-surface interaction.

The formation of Ti–O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

Titanium ions are implanted into amorphous SiO2 at two different fluences using pulsed ion implantation, and the resulting samples are annealed. Bulk sensitive soft X-ray absorption spectroscopy of the Ti L2,3 edge reveal strikingly different spectra for the two fluences. Spectral simulations using multiplet crystal field theory show clearly that for low fluence the Ti ions have a local octahedral coordination, while at higher fluence the formation of Ti4+–O tetrahedra dominates. Using O K-edge X-ray absorption and emission, the effect of the Ti states on the valence and conduction bands of the host SiO2 is revealed. With the introduction of Ti tetrahedra, the band gap reduces from about 8 eV to just over 4 eV, due entirely to the Ti 3d conduction band states. These results demonstrate the possibility to obtain Ti–O tetrahedra in silica by Ti ion implantation and a suitable thermal treatment, clarify the mechanism of band gap reduction with Ti doping in SiO2, and demonstrate the sensitivity of L-edge X-ray absorption with a multiplet crystal field theory analysis to the Ti coordination of novel materials.

Structural ordering in a silica glass matrix under Mn ion implantation

Mn+-implanted, amorphous SiO2 samples were synthesized using pulsed-ion implantation without thermal annealing. The crystal and electronic structures have been studied using x-ray diffraction and synchrotron-based soft x-ray absorption and emission spectroscopy at the Si and Mn L2,3 edges. We find a combination of small MnO clusters and Si crystallites at shallow depths while tetrahedral Mn coordination is found deeper in the host target. Through a combination of techniques, we find that the implantation process simultaneously decreases the long-range order in the near-surface region and increases order deeper in the SiO2 host. Our results suggest Mn substitution into Si sites at deep levels catalyzes the formation of α-quartz, providing insight into the complex interactions that determine the local structure around the impurities as well as the overall changes to the crystallinity of implanted SiO2.

ZnO based third generation biosensor

Zinc oxide (ZnO) has emerged as a leading material in the field of biosensors. However, the absence of redox couple is proving to be the major hindrance towards the development of a ZnO based third generation biosensor. Development of a composite matrix can be a possible way towards the realization of ZnO based mediator-less biosensor. In the present work pulsed laser deposition, chemical method and ion implantation has been explored for realization of ZnO based matrix which can be exploited for biosensor applications in mediator-free environment.

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness approximatly 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm2 to 1.0 x 10(17) ions/cm2 The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TIN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

Distribution of carbon in polycrystalline copper surfaces treated by methane plasma immersion ion implantation

Copper substrates with rather large grains (dimensions of some mm) treated by pulsed methane plasma immersion ion implantation exhibit a laterally inhomogeneous carbon distribution. Areas with high carbon X-ray intensity in electron probe microanalysis coincide with thicker carbon containing layers as seen in sputter depth profiling via secondary ion mass spectrometry. The distribution of carbon within the surface depends not only on the treatment time and pulse repetition rate but also on the orientation of the individual copper grains.

Broad excitation of Er luminescence in Er-doped HfO2 films

We investigated the broad and sensitized luminescence properties of Er-doped HfO2 films synthesized by pulsed laser deposition (PLD) and ion implantation techniques. In the investigation we focused on the mechanism of energy transfer in the host matrix. Based on the comparison of photoluminescence (PL), photoluminescence excitation (PLE), and cathode-luminescence (CL), as well as on microstructure measurements, an excitation transfer process resulting in the broad excitation for Er, luminescence at 1540 nm, is identified. In this process, the oxygen vacancies and Hf in the host HfO2 serve mainly as effective sensitizers for neighboring Er ions in the nonresonant excitation process. Furthermore, the direct Er3+ intra-4f transitions and full spectral emission of Er ions in the HfO2 matrix are clearly observed under the wide-spectrum excitation in the CL measurement. This reveals more detailed features for the energy transfer and transition processes.

1.54 μ m photoluminescence emission and oxygen vacancy as sensitizer in Er-doped HfO2 films

In this letter, we report on the characteristics of 1.54μm photoluminescence emission of Er-doped HfO2 films synthesized by pulsed laser deposition and ion implantation. An efficient emission at 1.54μm in the annealed HfO2 films has been observed under a broad band excitation from 400nm to a higher energy at room temperature. X-ray diffraction and electron paramagnetic resonant measurements were used to analyze the correlation between the optical properties and microstructures. An energy transfer mechanism is proposed that the O vacancy in the bulk acts as an effective sensitizer for the neighboring Er ions and greatly enhances the 1.54μm band emission. These results lay an important basis for the future silicon-based integrated optoelectronic device applications of Er-doped HfO2 films.