Lithium Implantation Research Articles

One-dimensional Hierarchical Porous Layered Oxide LiNi0.8Co0.1Mn0.1O2 Cathode for Lithium-ion Batteries via Self-template Interstitial Co-precipitation Method

A novel architecture, one-dimensional, microrod-like Ni-rich LiNi0.8Co0.1Mn0.1O2 cathodes assembled from small primary particles have been successfully constructed through morphology-conserved and solid-phase lithium implantation reaction. The considerable initial reversible discharge capacity (198.5 mAh·g−1 at 0.2 C) and cyclic performance (capacity retention of ∼73% after 100 cycles at 1 C) are obtained, attributed to the combined merits of unique microrod-like porous structure. Moreover, this work can be regarded as an attractive synthetic pathway toward the development of high-performance Ni-rich battery materials in future.

Lithium implantation at low temperature in silicon for sharp buried amorphous layer formation and defect engineering

The crystalline-to-amorphous transformation induced by lithium ion implantation at low temperature has been investigated. The resulting damage structure and its thermal evolution have been studied by a combination of Rutherford backscattering spectroscopy channelling (RBS/C) and cross sectional transmission electron microscopy (XTEM). Lithium low-fluence implantation at liquid nitrogen temperature is shown to produce a three layers structure: an amorphous layer surrounded by two highly damaged layers. A thermal treatment at 400 °C leads to the formation of a sharp amorphous/crystalline interfacial transition and defect annihilation of the front heavily damaged layer. After 600 °C annealing, complete recrystallization takes place and no extended defects are left. Anomalous recrystallization rate is observed with different motion velocities of the a/c interfaces and is ascribed to lithium acting as a surfactant. Moreover, the sharp buried amorphous layer is shown to be an efficient sink for interstitials impeding interstitial supersaturation and {311} defect formation in case of subsequent neon implantation. This study shows that lithium implantation at liquid nitrogen temperature can be suitable to form a sharp buried amorphous layer with a well-defined crystalline front layer, thus having potential applications for defects engineering in the improvement of post-implantation layers quality and for shallow junction formation.

Isotope distribution in electrochemical ion implantation in metals and composite materials

Experimental data are reported for the isotope distribution in the electrochemical implantation of lithium and hydrogen isotopes in metals and composite materials from LiOD and LiOH solutions. General regularities are identified for the changes in isotopic composition in the metal-matrix in which ions are implanted, in impurities in the metals, and in the ions responsible for electrolyte conductivity. Possible mechanisms for lithium implantation are considered on the basis of the analysis of isotope distribution.

Interaction of interstitials with buried amorphous layer in silicon

AbstractBuried amorphous layers have been produced in silicon single crystal by lithium implantation at liquid nitrogen temperature and followed by a 400 °C annealing. By this process, a wide region, perfectly crystalline and free of any extended defect, is formed ahead of the buried amorphous layer up to the implanted surface. Neon has then been implanted in this front region at high fluence and high temperature (250 °C) in order to create bubbles and avoid further amorphization. In the presence of a buried amorphous layer, significant decrease of the extended defect density is observed at the neon end of range region. The results are discussed in terms of interstitial trapping, i.e. the buried amorphous layer acting as an efficient sink for interstitials during recrystallization. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plasma Immersion Ion Implantation With Lithium Atoms

A new method was developed to produce lithium plasma for plasma immersion ion implantation. Initially, an argon glow discharge with operation pressure ranging from 2 times 10-1 to 1 mbar is generated by negatively polarizing an electrode from -400 to -1500 V. Small pieces of metallic lithium that are 99.9% pure fill the top of a conic crucible, with a depth of 2 cm, in electric contact with the electrode. Argon ions from the plasma are used to bombard this target, where heat is created by the momentum transfer from the impacting ions to the crucible. By controlling the operation pressure and the electrode voltage polarization, it is possible to easily heat the crucible to temperatures above the lithium melting point (180degC), causing its evaporation. Lithium atoms are then ionized, mainly due to collisions, with argon ions moving toward the crucible. Double Langmuir probe measurements indicated variation in the density of the discharge from 4 times 109 cm-3 to 1010 cm-3 after lithium evaporation. Silicon wafer pieces immersed in this mixed plasma were submitted to repetitive negative high-voltage pulses (3 kV/6 mus/2.5 kHz) to accelerate plasma ions. High strain in the treated layers was measured by high-resolution X-ray diffraction. Photoluminescence intensity increased after annealing. X-ray photoelectron spectrometry measurement revealed lithium implantation in silicon with an atomic concentration of 78% on the top surface and a penetration depth of about 75 nm.

N-type diamond produced by MeV lithium implantation in channeling direction

Natural diamond implanted with lithium ions at high energy ( E = 2MeV) in axial channeling direction is investigated. Hall measurements show n-type conductivity caused by the lithium implantation. These measurements show two regions in the Arrhenius plot for both resistance and charge carrier concentration. The resistance measurement in the low and high temperature range revealed the activation energies of E Rlow = 406meV and E Rhigh = 105meV. The slope for the charge carrier concentration shows a more complex behaviour. After annealing, the n-type conductivity caused by implanted lithium disappears.

A novel process for plasma immersion ion implantation and deposition with ions from vaporization of solid targets

AbstractA novel source for plasma immersion ion implantation and deposition (PIII&D) was developed in order to perform surface treatment of materials with ions from vaporization of solid targets. Usually this is obtained by means of beamline ion implanters, in which three dimensional implantation requires target manipulation, or by vacuum arc discharges, in which the presence of macroparticles is the main problem to be overcame. Samples of silicon wafers immersed in a lithium plasma produced by this source were submitted to low negative high frequency pulses (3‐4 kV/6 μs/3 kHz), causing lithium implantation and deposition. A very high strain and photoluminescence measured by high resolution X‐ray diffraction and Raman spectroscopy, respectively, were observed in the analyzed layers of the samples that were immersed in this plasma. XPS measurements revealed thick Li deposition for samples treated under conditions of high lithium vaporization rate. This novel process was effective for Li implantation/deposition and shows potential for PIII or PIII&D of many different elements from solid targets as Ca, K, Mg and Al. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Lithium nanocluster formation in Li+ - ion implanted MgO

AbstractPhoton absorption (PA), Positron Beam Analysis (PBA) and Neutron Depth Profiling (NDP) is applied to study the relation between photon absorption behavior and the precipitates formed by ion implantation and thermal annealing. Monocrystals of MgO(100) were implanted with 1.0×10166Li ions cm−2 at an energy of 30 keV. The samples were thermally annealed in air in steps up to 1200 K. After each step Doppler broadening Positron Beam Analysis (PBA) was applied to monitor the depth profile of the implantation defects. The evolution of the depth profile of lithium was followed with the aid of NDP. During the annealing there is hardly any change in the location of the lithium implantation peak at 150 nm (peak concentration 2 at. %). Only after annealing to 1200 K the majority of the lithium has left the crystal and optical absorption effects have disappeared. During annealing at 750 K an absorption band develops between 400 and 600 nm; at 950 K the maximum absorption is centered at 450 nm corresponding to Mie absorption and scattering by lithium nanoclusters. Positron beam analysis shows a considerable increase of annihilations with low momentum electrons in the implanted zone. A positron method for measuring electron momentum distributions (2D-ACAR) coupled to an intense positron beam gave evidence for the presence of semi-coherent metallic lithium inclusions.

Effects of lithium-implantation on the hydrogen retention in both a-C:H and a-SiC:H materials submitted to deuterium bombardment

The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from the a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both materials were implanted with different fluences of lithium ions. Before and after each irradiation, depth profiles of H, Li and deuterium were determined by nuclear microanalysis. After deuterium bombardment, it is shown that the retention of the initial hydrogen in both materials was enhanced by increasing the total dose of the implanted Li. For the a-C:H samples, the hydrogen desorption under deuterium bombardment was strongly reduced by lithium implantation. This effect was also evidenced in a-SiC:H samples, even though it is less spectacular than in a-C:H. Also, nuclear analyses showed that the retained dose of deuterium decreases when the lithium concentration increases. This could be a result of the formation of LiH bonds which occurs to the detriment of deuterium retention in both a-C:H and a-SiC:H materials. Preliminary results of both materials exposed to TdeV tokamak discharges confirms the role of Li in hydrogen retention, already observed in deuterium bombardment exposure.

Electrical properties of lithium-implanted layers on synthetic diamond

Lithium implantation (40 and 50 keV; doses of 2 × 10 16 and 4 × 10 16 cm −2) has been performed in several synthetic and natural diamond crystals at room temperature (RT) and 850–900 °C (high temperature (HT) implantation). In contrast with the case of the RT implantation, the HT implantation did not result in radiation-induced surface graphitization. The samples implanted at RT and 850 °C were subsequently annealed at 900 °C. Comparison of the electrical properties of the doped crystals shows the dependence of the electrical activation on the annealing temperature. Thermal emf measurements have established that the conductivity is n-type.

Photoluminescence Study of Li-implantation into ZnSe Epitaxial Layers Grown by Molecular Beam Epitaxy

ABSTRACTLithium ion-implantation was performed on ZnSe layers which were grown on GaAs substrates by MBE. Strong photoluminescence emission due to acceptor-bound excitons was observed from samples implanted with lithium doses of up to 1015cm−2 and annealed under optimized conditions for rapid thermal annealing. Lithium implantation results in low damage to the ZnSe as well as the formation of a shallow acceptor level. Thermal degradation of both implanted and unimplanted epilayers caused by the rapid thermal annealing was inviestigated at various annealing temperatures. We find that, under certain annealing conditions, unimplanted samples show greater thermal degradation than lithium implanted samples. The photoluminescence spectrum of an unimplanted sample annealed at 800°C shows considerable degradation; however, a lithium-implanted sample annealed at the same temperature still shows strong luminescence in the excitonic region.

Generation of new bound exciton lines by lithium implantation of CdS

Sharp new bound exciton optical absorption lines are observed following very low fluence (φ<5×1012 cm−2 room-temperature 7Li implantation of high quality cadmium sulfide platelets. A substantial broadening of the free exciton resonance by the lithium neutral donor impurities is observed. A model of the line shape is proposed.

Surface microhardening in a lithium implanted aluminium alloy

This paper describes changes observed in microhardness after implanting energetic lithium ions into pure aluminum and its 2024-T351 alloy. The addition of lithium to aluminum lowers the density and increases both the modulus of elasticity and tensile strength. Thus, these properties make such alloys attractive in aerospace applications. The authors believe that this is the first report where lithium implantation has been used to evaluate near surface changes.

Experiments on the sputtering of group VI elements

At the last REI ∗ ∗ 1st Intl. Conf. on Radiation Effects in Insulators, held in Arco, Lago di Garda, Italy (30.6. 1981). conference, we reported that 30…300 keV He + ions impinging on elemental solid sulfur cause tremendous erosion, corresponding to sputtering yields of 10 4 to 10 6 sulfur atoms per incident He ion. In the present work, these experiments were repeated at various temperatures to test our previously proposed model of a radiation enhanced sublimation. The measured temperature dependence indicates a thermally activated process. Further experiments on sulfur were performed with 3–9 keV Ar + ions for analysis of the masses and energies of the sputtered sulfur species. In contrast to thermal sublimation with predominantly S 2, S 4, and S 8 molecules, there is a preference for smaller clusters in sputtering by 3–9 keV Ar + ions. The other chalcogenes, selenium and tellurium, were irradiated with 50…300 keV He and Li for sputtering yield measurements. No special features or abnormally high sputtering yields were observed with these targets. Subsequent checks on the implanted helium and lithium revealed some unique features: the implanted helium is found to be extremely mobile in selenium at room temperature in contrast to the helium behaviour in metals. In the case of lithium implantation into selenium and tellurium, at least a major fraction shows mobility at room temperature, whereas the residual lithium is distributed in the targets according to theoretical predictions of range and damage distributions (TRIM calculations).