V.V. Bandourko

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-SiO2 under implantation with negative Cu ions of 60 keV, up to a dose rate of 100 μA/cm2. 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 MgAl2O3 and LiNbO3 detected by ion-induced photon spectroscopy

Abstract Ion-induced photon emission under 60 keV Cu − implantation into the insulators of MgAl 2 O 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

Abstract 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(Al2O3) with n=2.4 was irradiated with 60 keV Cu− at dose rates of 10, 50 or 100 μA/cm2 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(Al2O3) with those obtained for amorphous (a-)SiO2 substrate revealed the good correlation of Cu I line intensity with nanoparticle formation detected by optical absorbance measurement.

Picosecond dynamics of Cu nanoparticle composites embedded in insulators by 60-keV negative-ion implantation

Steady-state and laser-induced transient absorption around the surface plasmon resonance of copper nanoparticle composites, fabricated by ion implantation, have been studied by optical measurements. Negative ion implantation has been applied to generate the Cu nanoparticles in amorphous SiO2, crystalline MgOn(Al2O3), LiNbO3, SrTiO3 and TiO2 with various refractive indices and optical energy gaps. The surface plasmon resonance in the steady-state absorption resulted from formation of nanoparticles in the substrates and shifted to red with increasing refractive index of the matrix. The nanoparticle fabrication by the negative ion implantation was succeeded in all the insulating substrates used, and it is capable to tune the resonance band to 1.7 - 2.2 eV (730 - 560 nm) by selecting of the matrix. However, there remained a problem that the plasmon band in LiNbO3, SrTiO3 and TiO2 with narrow energy gap overlapped radiation-induced defect band. Laser-induced transient absorption was measured with a technique of pump-probe femtosecond spectroscopy. The bleaching plasmon band recovered in several picoseconds due to energy transfer from the excited electron system to the phonon system via the electron-phonon interaction. The transient absorption is also affected by radiation damage in the matrices with the narrow energy gap.

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 Cuions of 60 keV irradiated the polymers at a dose rate of 1 lA/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. 2002 Elsevier Science B.V. All rights reserved.

Ion-induced photon emission under nanoparticle fabrication

Abstract 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 2 O 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.