Ion-induced Photon Emission Research Articles

Rearrangements on the Surface of Heavy-Ion-Implanted LiNbO3

Metal-nanoparticle composites were fabricated by implantation of 60 keV Cu−, Ag−, and Au− ions into LiNbO3 single crystals. Monitoring of the chemical composition variations using ion-induced photon emission (IIPE) has shown that the ion implantation stimulates the accumulation of weakly bounded atoms at the irradiated surface. The contribution of weakly bounded atoms to IIPE was observed by stopping and subsequent renewal of ion implantation. The irradiated surface of nanocomposites experienced lasting rearrangement after ion implantation resulted in formation of surface structures. Results suggest that the heavy-ion implantation can be used for embedment of metal nanoparticles and initiation of self-organization on surfaces.

Ion-induced photon emission: Neutralization mechanism of surface plasmon excitation

A mechanism of surface plasmon excitation occurring in any, including resonant, processes of neutralization of positive and negative ions near metal surface is proposed and a model of this mechanism is developed. High efficiency of the mechanism and adequacy of the model to the ion-induced photon emission data are demonstrated. The main formulas of the model are discussed in terms of the quantum-mechanical perturbation theory and dielectric formalism.

Ferrous Ion Induced Photon Emission as a Method to Quantify Oxidative Stress in Stored Boar Spermatozoa

The aim of the study was to evaluate the effect of semen storage on ferrous ion induced luminescence of boar spermatozoa and to determine the relationship between parameters of this luminescence and lipid peroxidation as measured by malondialdehyde (MDA) contents. Boar semen samples were diluted in Biosolwens extender and stored for 12 days at 15 degrees C. Luminescence and MDA were measured directly after dilution (day 0) and at 6 and 12 days of semen storage. Luminescence was measured at 20 degrees C using a luminometer equipped with a cooled photomultiplier with a spectral response range from 370 to 620 nm. Emission was induced by adding FeSO4 solution (final concentration 0.05 mM). MDA content was measured by the HPLC method. The day of storage had a significant effect on some luminescence parameters and MDA content in spermatozoa. A significant correlation was observed between luminescence parameters and MDA concentration. The results of the study confirm that induced luminescence is strictly related to lipid peroxidation in spermatozoa that occur during boar semen storage. Parameters of luminescence treated as a holistic response of cells to oxidative stress can be useful for monitoring spermatozoa quality during semen preservation.

Effects of argon-ion bombardment on the properties of the surface layer in spinel crystals of different composition

Ion-induced photon emission (IPE) during bombardment of magnesium aluminate spinel crystals MgO· nAl 2O 3 by 20 keV Ar + ions was studied. The dependence of the yield of particles in specific excited states on the fluence of incident ions in the range of (0.1–1.6)×10 17 ions/cm 2 was measured. It was shown that yield of magnesium and aluminum atoms and ions in most excited states do not depend (or slightly depend) on the fluence of ion bombardment. An exception was found for yields of Mg + ions in the 4s 2S excited state and Al atoms in the 5p 2P 0 excited state leading to emission lines at 292.8 and 669.6 nm, respectively. The yield of particles in these excited states drastically decreases at the start of ion bombardment. Analysis of these results and published data on the bombardment-induced surface modification of spinel crystals allows to elucidate the role of crystal structure and chemical bonding in the formation of some excited states. The dependence of excited state yield (except of Mg and Al indicated above) from spinel crystals of different composition MgO· nAl 2O 3 ( n=1.0, 1.5, 2.0, and 2.5) does not reflect quantitatively the variation of the calculated bulk concentration of constituent atoms in these targets.

Stability of metal nanocomposites under heavy-ion bombardment of insulators

Optical transmission and ion-induced photon emission of SiO2 (silica glass), LiNbO3 and Al2O3 were measured during implantation of 60-keV Cu− or Au− ions. Conditions of stability of metal nanocomposites were determined and represented with the help of nonequilibrium phase diagrams. Formation of structures dynamically stable under ion bombardment diminished the efficiency of ion implantation for further accumulation of implants as in nanoparticles. Contributions from various radiation-induced processes (sputtering, radiation-induced diffusion, atomic collisions, electronic excitations, etc.) to formation of nanocomposites were evaluated.

Electronic excitation and optical responses of metal-nanoparticle composites under heavy-ion implantation

Measurements of optical transmission and ion-induced photon emission (IIPE) during implantation of copper ions into silica glass (a-SiO2) have been combined in order to study formation of Cu nanoparticles. It has been shown that in situ measurements are more advantageous than conventional experimental approaches of examining the properties of ion-implanted nanocomposites solely after implantation. Series of experiments have been done to prove that the band of IIPE at 545–550 nm originates from Cu+ solutes in a-SiO2. The combination of in situ optical techniques provides means of monitoring Cu nanoparticles and Cu solutes via the optical absorption in the range of the surface-plasmon resonance (SPR) of nanoparticles and the IIPE of Cu+ solutes. It has been shown that a simple linear approximation can be used to separate optical bands of defects, Cu solutes, and nanoparticles. Ion-induced transient optical absorption has been found in the ranges of SPR and defect bands. The transient optical response in the range of SPR has been tentatively attributed to a thermomodulation effect. We analyze relationships between electronic excitation, radiation-induced optical responses, and kinetics of nanoparticle formation. Several stages of nanoparticle formation have been distinguished: accumulation of Cu solutes, precipitation of Cu atoms, coalescence, growth of nanoparticles, and saturation of nanocomposites.

Heavy-ion-induced luminescence of amorphous SiO2 during nanoparticle formation

Silica glass was implanted with negative 60keV Cu ions at an ion flux from 5 to 75μA/cm2 up to a fluence of 1×1017ions/cm2 at initial sample temperatures of 300, 573 and 773K. Spectra of ion-induced photon emission (IIPE) were collected in situ in the range from 250 to 850nm. Optical absorption spectra of implanted specimens were ex situ measured in the range from 190 to 2500nm.IIPE spectra showed a broad band centered around 560nm (2.2eV) that was assigned to Cu+ solutes. The band appeared at the onset of irradiation, increased in intensity up to a fluence of about 5×1015ions/cm2 and then gradually decreased indicating three stage of the ion beam synthesis of nanoclusters: accumulation of implants, nucleation and growth nanoclusters. The IIPE intensity normalized on the ion flux is independent on the ion flux below 20μA/cm2 at higher fluences. The intensity of the band increased with increasing samples temperature, when optical absorption spectra reveal the increase of Cu nanoparticles size.

Optical effects in silica glass during implantation of 60 keV Cu − ions

Spectra of the optical transmission and ion-induced photon emission (IIPE) of silica glass were measured during implantation of 60 keV Cu − ions at ion fluxes from 1 to 75 μA/cm 2 up to a fluence of 2 × 10 17 ions/cm 2, aimed at monitoring the formation of Cu nanoparticles. The precipitation threshold of Cu atoms is flux-dependent. At fluxes from 1 to 10 μA/cm 2, the formation of nanoparticles is efficient up to fluences of 2 × 10 17 ions/cm 2. The efficiency of IIPE of Cu + solutes in silica glass (band at 2.25 eV) is proportional to a total concentration of Cu solutes. In a single-phase region (solid solution of Cu atoms), the efficiency of IIPE of Cu + solutes is flux-independent. In a two-phase region (solid solution and Cu nanoparticles), the dynamic balance between the nanoparticles and Cu solutes determines the flux-dependent behavior of the efficiency of IIPE.

Optical monitoring of nanoparticle formation during negative 60 keV Cu ion implantation into LiNbO 3

Spectra of the optical transmission and ion-induced photon emission (IIPE) of LiNbO 3 were measured during implantation of 60 keV Cu − ions at ion fluxes from 1 to 50 μA/cm 2 up to a fluence of 2 × 10 17 ions/cm 2. The optical transmission in the range of surface plasmon resonance (SPR) and the IIPE are good monitors of the nanocomposite formation and the chemical composition change, respectively. Copper atoms precipitate at fluences lower than 6 × 10 15 ions/cm 2. Further formation of nanocomposite comprises two easily distinguishable stages: the slope of fluence dependencies of SPR abruptly decreases at about 10 17 ions/cm 2. Lithium-depleted regions are created in the substrates, and concentration of Nb increases. The formation of nanocomposite is most efficient at a flux of 1 μA/cm 2.

Proton beam micromachining dose normalization for SU-8 using ionoluminescence detection

Proton beam micromachining (PBM) allows the production of small, intricate, high aspect ratio structures with smooth sidewalls by direct writing MeV protons beams in resist materials such as SU-8 and PMMA. The process depends on the correct incident dose of protons, and conventional normalizing methods using RBS have been utilized previously. However for accelerated (sensitive) resists such as SU-8, the yield of backscattered ions, particularly for small structures, is insufficient for accurate dose measurement. We have used the more prolific ion induced photon emission from SU-8 as a dose normalizing signal for PBM. The SU-8 emits radiation at a wavelength of 560 nm under proton irradiation, and the yield per incident proton depends on the thickness of the resist layer. The photon yield per incident proton has a maximum value at a dose of 25 nC mm −2. The photon normalization method has been used to good effect to micromachine a complex shape with resulting good edge definition.

Ion-induced photon emission under nanoparticle fabrication

Metal-ion implantation is well established as a suitable technique for fabrication of nanoparticles embedded in insulators. Photon emission induced by 60 keV Cu − incident ion was in situ measured over a wavelength range from 200 to 900 nm. Special attention was paid to the behavior of the Cu I atomic line emission related to the mass transport of implants. Based on comparison of experimental results for the wide band gap materials (SiO 2 and MgAl 2O 4) with those for metals (W, Mo, Al), it is concluded that, at the beginning of ion bombardment, the radiation is mostly emitted by backscattered atoms. The causes of this are different for the different groups of materials: the high backscattering yield in the case of metals and the high survival probability of the excited backscattered atoms in the case of insulators, when the excitation levels lie below the conduction band edge and the radiative decay is only the available channel for deexcitation. Significant contribution in the Cu I line intensity was observed with increasing dose due to sputtered Cu atoms.

In situ photon-emission spectroscopy and ex situ surface analyses of polymers irradiated with 60 keV Cu − ions

Ion-induced surface modification processes of polystyrene (PS) and high-density polyethylene (HDPE) have been studied by either in situ photon-emission spectroscopy or ex situ surface analyses. Heavy Cu − ions of 60 keV irradiated the polymers at a dose rate of 1 μA/cm 2 and ion-induced photon emission was in situ measured in a spectral region of 250–850 nm. Ion-induced chemical reactions of the surface layers were ex situ evaluated by X-ray photoelectron spectroscopy (XPS). Intensity, spectral shape and dose dependence of the photon emission were significantly different between aromatic-containing polymers (PS) and linear polymers (HDPE) in the same irradiation condition. The emission spectrum of HDPE represented a broad band with a maximum at about 595 nm, while that of PS showed a sharp peak around 656 nm. The total emission yield observed for PS was much lower than that of HDPE, and the decay rates of emission intensity for PS were different from that of HDPE in a dose region less than 10 14 ions/cm 2. The XPS analyses showed chemical change of the surface bonding. These results suggested that ion-induced processes caused hydrogen extraction, crosslinking and bond scission of the matrix.

Ion-induced photon spectroscopy of insulators and application to in-situ diagnostics of nanoparticle formation processes

Ion-induced photon emission under heavy-ion bombardment has been studied over an energy range from near-infrared to vacuum-ultraviolet. Time-resolved optical devices with fast-response CCD cameras detected photons from a-SiO 2 under implantation with negative Cu ions of 60 keV, up to a dose rate of 100 μA/cm 2. The ion-induced photon spectra consisted of sharp line spectra due to isolated atoms of Si, Cu and a broad band of visible light. The line spectra resulted from an ion-induced glow above the surface and indicated pronounced outward transport of Cu atoms to the vacuum. Intensity of the line spectra and the broad band varied non-linearly with dose and dose rate. The in-situ spectroscopy provided diagnostic information of surface- and intra-solid processes associated with nanoparticle formation at high dose rates. The Cu sublimation reflected from presence of a Cu-depleted zone beneath the surface, which is one of the important factors to form a two-dimensional arrangement of nanoparticles.

Real-time evolution of ion–surface interactions of MgAl 2O 3 and LiNbO 3 detected by ion-induced photon spectroscopy

Ion-induced photon emission under 60 keV Cu − implantation into the insulators of MgAl 2O 4 and LiNbO 3 was in situ measured over a wide wavelength range from 200 to 900 nm. The formation of the Mg and Li deficient layers for the respective insulator was detected based on the dose dependence of the Al, Mg and Li atomic line intensities. The Al I and Mg I line intensities from spinel exhibit different behaviors depending on irradiation temperatures: they gradually decrease while the (Al I)/(Mg I) ratio increases up to dose of 3×10 17 ions/cm 2 at room temperature or exhibits a steady-state tendency at high temperature. Sharp decrease of Li I line intensity from LiNbO 3 under high dose rate bombardment indicates drastic changes of surface layer that may alter the phase stability and optical performance of insulators.

Ion-induced photon emission of magnesium aluminate spinel during 60 keV Cu − implantation

The beam–solid interaction during high flux heavy-ion implantation has been studied by the in situ detection of photon emission. A spinel of MgO· n(Al 2O 3) with n=2.4 was irradiated with 60 keV Cu − at dose rates of 10, 50 or 100 μA/cm 2 to a dose of 1.5×10 17 ions/cm 2 . Under the implantation, photon emission ranging from 1.4 to 6.2 eV was detected by a time-resolved optical device based on a fast-response CCD (Princeton Instruments: IMAX-512). Emission lines of sputtered Mg, Al and Cu atoms were observed. A comparison of the dose and dose rate dependence of the Cu I line intensity from MgO· n(Al 2O 3) with those obtained for amorphous (a-)SiO 2 substrate revealed the good correlation of Cu I line intensity with nanoparticle formation detected by optical absorbance measurement.

In-Situ Spectroscopy of Ion-Induced Photon Emission During Metal Nanoparticle Formation in Silica Glass with High-Flux Cu Implantation

ABSTRACTIon-induced photon emission from a silica glass irradiated with high-flux Cu ions was measured in a wavelength range from 450 nm to 800 nm, while nanoyarticles spontaneously formed in the silica glass. Current density was varied up to 100 µA/cm2 at a constant total dose of 3×106ions/cm2. The photon emission primarily arose from the vicinity of the substrate surface and consisted of sharp peaks due to neutral and singly-ionized species, Cu(I), Cu(II) and Si(II) ions, as well as a broad-band background. Intensity of Si(II) and Cu(I) increased with increasing current density. On the other hand, Cu(II) did not show a monotonic increase, decreasing around 100 µA/cm2. Measurements of in-situ EDX and ex-situ RBS were also conducted to study the relevant mechanisms. The ion-induced photon emission was attributed to recombination processes of sputtered ions and electrons in the plasma, induced by the high-flux Cu beam.

Detection limits in ion induced photon emission measurements achieved by an intensity optimized optical system

A measurement system for ion induced photon emission (IIPE) measurements has been established and optimized for maximum light collection and detection efficiency. This is achieved by a special imaging system and a liquid nitrogen cooled CCD camera as the detector. The performance of the imaging system has been evaluated by ray tracing calculations. In sputter depth profiling, which is the most important application of IIPE, the detection limit does not depend on the available primary ion current. Detection limits are strongly element dependent and reach about 1 ppm for alkali metals in depth profiling. Detection limits for bulk concentrations can be up to three orders of magnitude less than detection limits for depth profiling. Compared to previously published values a significant improvement has been achieved.

Fast heavy ion induced photon emission from organic solids and plasma desorption mass spectrometry

Fission fragments from a 252Cf source have been used to study fast heavy ion induced desorption of ions and luminescence in the wavelength region 200–680 nm from samples of Csl, the amino acids valine, isoleucine and tyrosine, and of the peptide substance P. All samples emit photons under fast heavy ion bombardment. Most of the emission is confined to the near-UV region and within narrow time profiles. Analysis of the fast decay regions of the time profiles show that all the compounds have at least a fast and a slow decay component, both in the nanosecond region. The use of such narrow photon signals as start time markers for time-of-flight measurements (TOF) has been demonstrated. As the photon signal is derived directly from the desorption event it gives the true number of starts for a secondary ion TOF spectrum. Characteristics of the photon emission from a CsI target together with correlation studies between the desorbed secondary ions and the photon signal indicate that the light emission is from the bulk of the material and not correlated with the secondary ions.

Spectroscopic study of ion-induced photon emission under D + and He + bombardment

In order to investigate the interaction of energetic ions with a solid surface, we have performed a spectroscopic study of the ion-induced photon emission under D + or He + bombardment with incident energies ranging from 10 to 25 keV. The line spectra of D α (656.10 nm) and HeI (578.76 nm) emitted from the reflected particles in excited states were analyzed in terms of incident ion energy, target material and residual gas pressure. With increasing incident ion energy, both the D α and HeI spectra shifted to a shorter wavelength and broadened, while the photon intensities of both the D α and HeI emission decreased. The intensities also grew with the Z number of the target materials showing a very similar relation to that reported between the reflection coefficients and the Z number. Oxygen at the surface significantly enhanced the HeI emission, whereas the D α emission was hardly influenced. Compared with oxygen, the effects of hydrogen and nitrogen on the intensity were very small. The difference could be attributed to a resonance excitation of the electrons of reflected neutrals.

Ion-photon emission of CuZn alloy

Some CuZn alloy targets of different known concentrations were investigated using the ion-induced photon emission (IIPE) technique. The influence of the projectile energy and incidence angle on the ratio of the intensities of CuI (324.7 nm) and ZnI (481.1 nm) emission lines was measured. The theory of the quantitative analysis of two-component alloys based on standards and taking into consideration the matrix effects is discussed.