Low Fluence Implantation Research Articles

Effect of vanadium implantation on the chemical bonding structure of glassy carbon

We present characterization of the glassy carbon and vanadium implanted glassy carbon. Glassy carbon (GC) substrates were implanted with 15 keV Vanadium ions to a fluence ranging from 1 × 1012 to 1 × 1015 V+/cm at room temperature. Raman spectroscopy was used to monitor the structural changes in the samples as a result of the implantation. The Raman spectrum of the pristine glassy carbon sample shows the characteristic D and G peaks at 1350 cm−1 and 1588 cm−1. Raman spectra of samples implanted at 1 × 1012, 5 × 1012 and 1 × 1013 V+/cm respectively show that the glassy carbon structure remains unchanged when compared to that of the pristine glassy carbon. This indicates that the low fluence implantation of vanadium does not result in the radiation damage of the glassy carbon structure. High fluence implantation at 1 × 1014 and 1 × 1015 V+/cm resulted in a slight change of the Raman spectrum of glassy carbon. The D and G peaks merged slightly into each other and became wider suggesting that the samples became damaged after implanting at these high fluence.

Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning

AbstractThe combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane‐formed whispering‐gallery‐mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.

Local Tuning of the Surface Potential in Silicon Carriers by Ion Beam Induced Intrinsic Defects

The immobilization of biomaterials on a carrier is the first step for many different applications in life science and medicine. The usage of surface-near electrostatic forces is one possible approach to guide the charged biomaterials to a specific location on the carrier. In this study, we investigate the effect of intrinsic defects on the surface potential of silicon carriers in the dark and under illumination by means of Kelvin probe force microscopy. The intrinsic defects were introduced into the carrier by local, stripe-patterned ion implantation of silicon ions with a fluence of 3 × 1013 Si ions/cm2 and 3 × 1015 Si ions/cm2 into a p-type silicon wafer with a dopant concentration of 9 × 1015 B/cm3. The patterned implantation allows a direct comparison between the surface potential of the silicon host against the surface potential of implanted stripes. The depth of the implanted silicon ions in the target and the concentration of displaced silicon atoms was simulated using the Stopping and Range of Ions in Matter (SRIM) software. The low fluence implantation shows a negligible effect on the measured Kelvin bias in the dark, whereas the large fluence implantation leads to an increased Kelvin bias, i.e. to a smaller surface work function according to the contact potential difference model. Illumination causes a reduced surface band bending and surface potential in the non-implanted regions. The change of the Kelvin bias in the implanted regions under illumination provides insight into the mobility and lifetime of photo-generated electron-hole pairs. Finally, the effect of annealing on the intrinsic defect density is discussed and compared with atomic force microscopy measurements on the 2nd harmonic. In addition, by using the Baumgart, Helm, Schmidt interpretation of the measured Kelvin bias, the dopant concentration after implantation is estimated.

Effects of light-ion low-fluence implantation on the pressure response of double-walled carbon nanotubes

Low-fluence light-ion $(^{11}\mathrm{B}^{+})$ medium-energy (150 keV/ion) implantation preprocessing of double-walled carbon nanotubes (DWCNTs) has been effected to ``decorate'' them with defects. These are intended to serve as nucleation sites for potential $s{p}^{3}$ interlinking between tube walls in close proximity, following on strong deformation of the tube cross sections under cold compression to 20--25 GPa in diamond anvil cells. The pressure response of such implanted DWCNTs has been monitored in situ using Raman spectroscopy, and compared with those of unimplanted reference DWCNTs. Pressure dependences of the ${G}^{+}$ mode frequency and D to ${G}^{+}$ band intensity ratio, and radial breathing modes, have been monitored. These Raman signatures show that some degree of mechanical softening occurs in the implanted tube bundles, without major disruption to tube integrity in both samples. Consequently, the collapse pressure to racetrack or peanut shaped cross-sectional profiles is lowered substantially, from ${P}_{\mathrm{c}}\ensuremath{\sim}18\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the reference tube bundles to ${P}_{\mathrm{c}}\ensuremath{\sim}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the implanted case. Defect structures also proliferate more readily in the implanted sample under pressure. Therefore, the light-ion low-fluence implantation lowers the threshold pressure for deformation of tube cross sections to high-curvature profiles decorated with defects. Considerations of whether irreversible $s{p}^{3}$ interlinking at low volume fractions is discerned in the Raman data from implanted tube bundles under compression, and the stability of such bonding is discussed.

Sensitivity of 57Fe emission Mössbauer spectroscopy to Ar and C induced defects in ZnO

Emission Mossbauer Spectroscopy (eMS) measurements, following low fluence (<1012 cm−2) implantation of 57Mn (t1/2 = 1.5 min.) into ZnO single crystals pre-implanted with Ar and C ions, has been utilized to test the sensitivity of the 57Fe eMS technique to the different types of defects generated by the different ion species. The dominant feature of the Mossbauer spectrum of the Ar implanted ZnO sample was a magnetic hyperfine field distribution component, attributed to paramagnetic Fe3+, while that of the C implanted sample was a doublet attributed to substitutional Fe2+ forming a complex with the C dopant ions in the 2− state at O vacancies. Magnetization measurements on the two samples, on the other hand, yield practically identical m(H) curves. The distinctly different eMS spectra of the two samples display the sensitivity of the probe nucleus to the defects produced by the different ion species.

Active waveguides by low-fluence carbon implantation in Nd3+-doped fluorophosphate glasses

A planar waveguide in the Nd[Formula: see text]-doped fluorophosphate glass is fabricated by a 6.0 MeV C[Formula: see text] ion implantation at a low-fluence of [Formula: see text] ions/cm2. The fluence is close to that in semiconductor industry. The dark mode spectra are recorded by a model 2010 prism coupler. The energy losses during the implantation process and the refractive index profile of the waveguide are simulated by the SRIM 2010 code and the reflectivity calculation method (RCM), respectively. The near-field light intensity profile and the propagation loss of the waveguide are measured by an end-face coupling system. The two-dimensional (2D) modal profile of transverse electric (TE) mode for the fabricated waveguide is calculated by the finite difference beam propagation method (FD-BPM). The results of microluminescence and optical absorption reveal that the spectroscopic characteristics of the Nd[Formula: see text]-doped fluorophosphate glass are nearly unaffected by the carbon ion implantation process. This work suggests that the carbon-implanted Nd[Formula: see text]-doped fluorophosphate glass waveguide is a promising candidate for integrated active devices.

Damage annealing in low temperature Fe/Mn implanted ZnO

57Fe Emission Mossbauer spectra obtained after low fluence (<1012 cm −2) implantation of 57Mn (T1/2= 1.5 min.) into ZnO single crystal held at temperatures below room temperature (RT) are presented. The spectra can be analysed in terms of four components due to Fe 2+ and Fe 3+ on Zn sites, interstitial Fe and Fe in damage regions (Fe D). The Fe D component is found to be indistinguishable from similar component observed in emission Mossbauer spectra of higher fluence (∼1015 cm −2)57Fe/ 57Co implanted ZnO and 57Fe implanted ZnO, demonstrating that the nature of the damage regions in the two types of experiments is similar. The defect component observed in the low temperature regime was found to anneal below RT.

Electron microscopy profiling of ion implantation damage in diamond: Dependence on fluence and annealing

The doping of diamond by ion implantation has been feasible for 25years, but with the proviso that low dose implants can be annealed whereas high dose implants “graphitize”. An understanding of the types of defects, and their depth profiles, produced during the doping/implantation of diamond remains essential for the optimization of high-temperature, high-power electronic applications. This study focuses on investigating the nature of the radiation damage produced during the implantation of carbon ions into synthetic type Ib and natural diamonds using a spread of 4 energies, corresponding to typical doping energies, according to the CIRA (Cold-Implantation-Rapid-Annealing) routine, as well as a single energy implantation at room temperature. Both conventional and high resolution cross-sectional electron microscopies were achieved and used to analyze the implanted diamonds in conjunction with electron energy loss spectroscopy (EELS) and selected area diffraction (SAD). The cross sections were obtained using two different preparation methods.For low fluence implantations, using the CIRA routine, it is confirmed that the damaged diamond regains its crystallinity after annealing at 1600K. However, above the amorphization threshold fluence, followed by rapid annealing at 1600K, the whole implanted layer consisted of primarily amorphous carbon. High resolution TEM shows that the implanted layer consists of nano-regions with bent (002) graphitic planes and regions of amorphous carbon. The interface between the implanted layer and the diamond substrate near end of range shows diamond nanocrystallites, interspersed between regions of amorphous carbon and with bent (002) graphitic planes. There is no evidence for epitaxial regrowth. For high dose single energy ion implantation at room temperature, the unannealed layer shows a high degree of disorder at the maximum ion range, with some alignment of basal planes related to graphitic carbon, but with some of the diamond structure still partially intact. The implanted range included a diamond layer above the damaged region. This diamond layer showed no evidence of amorphous carbon.

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.

Possible cage motion of interstitial Fe in α-Al 2 O 3

In addition to spectral components due to Fe2 + and Fe3 + , a single line is observed in emission Mossbauer spectra following low fluence (<1015 cm − 2) implantation of 57Fe*, 57Mn and 57Co in α-Al2O3. For the 57Co and 57Mn implantations, the intensity of the single line is found to depend on the emission angle relative to the crystal symmetry axis. This angular dependence can be explained by a non-isotropic f-factor and/or motion of the Fe ion between sites in an interstitial cage. It is argued that interstitial cage motion is a more likely explanation, as this can account for the lack of quadrupole splitting of the line.

Optical doping and damage formation in AlN by Eu implantation

AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3×1014 to 1.4×1017 atoms/cm2 in two different geometries: “channeled” along the c-axis and “random” with a 10° angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the channeled implantation within the entire fluence range. For random implantation, a buried amorphous layer is formed at the highest fluences. Red Eu-related photoluminescence at room temperature is observed in all samples with highest intensities for low damage samples (low fluence and channeled implantation) after annealing. Implantation damage, once formed, is shown to be stable up to very high temperatures.

The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

Si nanoparticle formation in SiO 2 by Si ion implantation: Effect of energy and fluence on size distribution and on SiO 2 composition

The injection of current in electroluminescent devices based on silicon nanocrystals (Si-nc) embedded in SiO 2 matrix is facilitated by the use of very thin SiO 2 layer. Therefore, the production of Si-nc by implantation of excess Si ions in the SiO 2 substrate has to be performed at lower energy. We have hence studied the effect of the Si ion energy on the Si-nc size distribution as well as on the surrounding SiO 2 matrix. Si has been implanted into thermally grown oxide film on Si (100) substrate at 50 and 150 keV with 5 × 10 16 to 2.2 × 10 17 Si +/cm 2. TEM has shown that for low doses (where the photoluminescent signal is at maximum) the Si-nc size is nearly uniform around 3 nm, whereas at high doses there is a size distribution (1.8–20 nm). A good agreement in the Si-nc average size has been found between XRD and TEM characterizations. Measurement by TEM of the implanted SiO 2 thickness has revealed that the swelling is more important for low fluence implantation due to the formation of amorphous Si clusters. XPS has shown partial oxygen depletion near the surface as well as a production of non-stoichiometric oxides of varying composition with depth.

A method for very low fluence implantations using Rutherford scattering

A simple method for extremely low fluence ion implantation is described. It is based on implanting ions which are Rutherford backscattered (RBS) from a thin gold layer into the desired target. This method enables ion implantations to be carried out, as are needed to realize quantum centers on the atomic scale to serve as qubits and other nano sized devices. The required implantation fluences are orders of magnitude below the commonly-used current integration capabilities; hence control on the implanted fluence is usually complicated. The described method enables control on the implanted fluence even when extremely low. The dependence of the energy and fluence of scattered ions on the angle and scattering target thickness is analyzed by using SRIM simulations. These are verified for the case of N scattering implantation by direct counting in a surface barrier detector and for the case of Xe by counting the tracks that scattered and implanted Xe ions leaved in HOPG as viewed by scanning probe microscopy.

Implantation of P ions in SiO 2 layers with embedded Si nanocrystals

The effect of 10 13–10 16 cm −2 P ions implantation and of subsequent annealing on Si nanocrystals (Si-ncs), formed preliminarily in SiO 2 layers by the ion-beam synthesis, has been studied. Photoluminescence (PL), Raman spectroscopy, high resolution electron microscopy (HREM), X-Ray Photoelectron Spectroscopy (XPS) and optical absorption were used for characterizations. The low fluence implantations have shown even individual displacements in Si-ncs quench their PL. Restoration of PL from partly damaged Si-ncs proceeds at annealing less than 1000 °C. In the low fluence implanted and annealed samples an increased Si-ncs PL has been found and ascribed to the radiation-induced shock crystallization of stressed Si nanoprecipitates. Annealing at temperatures under 1000 °C are inefficient when P ion fluences exceed 10 14 cm −2, thus becoming capable to amorphize Si-ncs. High crystallization temperature of the amorphized Si-ncs is attributed to a counteraction of their shell layers. After implantation of the highest P fluences an enhanced recovery of PL was found from P concentration over 0.1 at.%. Raman spectroscopy and HREM showed an increased Si-ncs number in such layers. The effect resembles the impurity-enhanced crystallization, known for heavily doped bulk Si. This effect, along with the data obtained by XPS, is considered as an indication P atoms are really present inside the Si-ncs. However, no evidence of free electrons appearance has been observed. The fact is explained by an increased interaction of electrons with the donor nuclei in Si-ncs.

High-fluence Co implantation in Si, SiO 2/Si and Si 3N 4/Si : Part II: sputtering yield transients, the approach to high-fluence equilibrium

The partial sputtering yields of different species from silicon dioxide/Si and silicon nitride/Si during high-fluence keV Co Metal Vapour Vacuum Arc (MEVVA) irradiation are of importance for both silicide formation and interpretation of sputter profiling. Three sets of samples, nitride/Si(1 0 0), oxide/Si(1 0 0) and oxide/Si(1 1 1), have been bombarded to different normal fluences, Θ, from 1 × 10 16 to 2.6 × 10 18 ions cm −2. The partial sputtering yields for N and Si in the thick nitride films are ∼1.0 and ∼0.65, respectively, which indicates that the relative sputtering ratio of N/Si is ∼1.5. The partial sputtering yields for O and Si of oxide/Si(1 0 0) samples are determined as ∼1.0 and ∼0.3, respectively. Although the O and Si sputtering yields from oxide/Si(1 1 1) samples are ∼15% higher, the average sputtering ratio of O/Si is ∼3.4, the same for both sets of oxide/Si samples. As expected, the partial sputtering yield of Co, Y Co( Θ), is small for low fluence implantation and increases with increasing Co fluence. At a normal fluence of ∼5 × 10 17 ions cm −2, Y Co( Θ) reaches the high fluence quasi-equilibrium limit, the value is very close to unity. The sputtering yield of Co reduces slightly at even higher fluences, which is associated with erosion of the sample surface.

The impact of in situ photoexcitation on the formation of vacancy-type complexes in silicon implanted at 85 and 295 K

Photoexcitation of silicon during low-fluence implantation with MeV Si and Ge ions is observed to suppress vacancy-type point-defect formation, as determined by in situ deep-level transient spectroscopy. The A-center formation after low-temperature implantation is extended over a wide temperature interval indicating that electrically inactive clusters, which emit vacancies during annealing, are formed in the end-of-range region during implantation at 85 K. The number of vacancies stored in these clusters is influenced by low-temperature in situ photoexcitation.

High fluence boron implantation into polymers

100 keV B+ ions are implanted at high fluence into three polymers of technological importance and into a polymeric mixture, respectively. The boron depth distributions are measured by the neutron depth profiling technique. It is shown that the boron atoms redistribute after their implantation according to the nuclear (collisional) energy transfer distribution. This contrasts to low fluence implantation, where the boron atoms redistribute according to their electronic energy transfer distributions. Subsequently, the samples are annealed isochronally. The change of the boron depth profiles with annealing temperature is then evaluated to determine the diffusional, trapping and detrapping behavior of the boron atoms. At, or slightly above room temperature, intrinsic boron impurities of the examined polymer foils become mobile and getter in the ion-implanted region. At higher temperatures, the thermal desorption spectra show a nearly continuous desorption of both the implanted and gettered boron, with no pronounced desorption peaks. Due to the high polymeric destruction yield, the different polymers show little difference in their desorption behavior.

Chemical and compositional changes induced by N+ implantation in amorphous SiC films

The effects of 30 keV N+ implantation in amorphous silicon carbide films deposited on silicon substrates by rf sputtering over a fluence range of 1×1016–2×1017 ions cm−2, are studied by means of x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and infrared (IR) absorption techniques. The ion-induced modifications of these films have been investigated on the basis of the chemical state evolution of Si, C, and N (using XPS and AES) and on the basis of the vibrational features of the films components (using IR absorption). The results show that implanted N bonds Si selectively, substituting the C atoms in the silicon carbide, and the C substitution by N results in a composite layer of carbonitrides and free C. An ion-induced C transport has also been observed and correlations are established between the formation of silicon carbonitrides and the dynamical behavior of the C in the implanted layer. The latter appears as a superposition of (a) a chemically induced atomic redistribution, required by local stoichiometry and space-filling possibilities in an amorphous network, and (b) a radiation-induced redistribution, a mechanism that is prevailing at low-fluence implantation.

Implanted He retention and release from boronized layers

He has been implanted at an energy of 3 keV into amorphous hydrogenated boron-carbon (a-BC) films deposited by rf sputtering onto single crystal Si substrates. The initial composition of the films was analyzed by nuclear-enhanced backscattering spectrometry to be B2C with ∼20% H and ∼10% O. The areal density of the implanted and retained 3He was measured in situ by a new ion beam analysis technique using the 3He(3He, pp) three-body nuclear reaction. The He trapping or pumping efficiency at room temperature is only 3.4% for low fluence implants and the a-BC layer saturates with He at a fluence of 5×1017 He/cm2. At this saturation fluence, only 3.1×1015 He/cm2 is retained in the film. Isochronal annealing of the implanted samples reveals a distributed release of implanted He at ∼200°C, which corresponds to a trap activation energy of 1.65±0.25 eV. 3He was trapped less efficiently at 250°C than at room temperature and exhibited a saturated retention of 8.6×1014 He/cm2. These results indicate that wall pumping should play only a minor role in the interpretation of the Textor He-pump experiment carried out earlier this year. The results also show that the unintentional deposition of a-BC, onto He pumping plates could adversely affect the operation of such devices, and should therefore be avoided.