Search

Distributions of structural and refractive index changes of silica irradiated by H + microbeam were studied by optical and atomic force microscopes (AFM). The AFM measurements on the microbeam irradiated area show the formation of a groove on the surface. In addition, a cross sectional observation on the surface parallel to the incident plane reveals surface deformation along the ion tracks, which is deepest at the projected range of ions. Taking into account the possible structural changes of silica induced by energy deposition calculated by TRIM, the measured topological changes at the front and side surfaces result from internal compaction of silica glass. Refractive index changes were estimated from the Lorentz–Lorenz relationship using the distribution of the internal compaction estimated by the AFM measurements.

We evaluated structural changes in silica glass induced by ion microbeam using microscopic photoluminescence (PL) and Raman scattering measurements. Microbeams (1.7 MeV H+) were scanned over the sharp right-edges of the silica substrates with a fluence of 1×1017 cm−2, then two PL bands of silica at 540 and 650 nm were observed at the irradiated region. The PL bands show different lateral and depth distributions. The distribution of the 540 nm PL is in good agreement with that of the refractive index changed region. The lateral distribution of the 650 nm band is broader by 1.5 times than those of the 540 nm PL and the refractive index changed region. The microscopic Raman scattering measurements show an increased intensity of 606 cm−1 peak associated with compaction at the microbeam irradiated regions.

Weinvestigatethemechanismsofdefectformationandopticalabsorptioninducedbyionimplantation,forfab-rication of optical devices by radiation effects. High-purity silica implanted by H þ or He 2þ was characterized usingvacuum-ultraviolet spectroscopy and electron-spin-resonance measurement. Defect formation is suppressed by OHgroups,possiblybythereleaseofatomichydrogen.TheE 0 centerandnonbridgingoxygenholecenterwerecreatedthroughpairgenerationfromthenormalSiAOASibond.TheperoxyradicalwasgeneratedthroughthereactionoftheE 0 center with interstitial oxygen, which is a Frenkel-defect pair with an oxygen vacancy. By the Kramers–Kroniganalysis on the MeV-ion implantation-induced defects, a refractive index increase of the order of 10 4 was esti-mated. 2002ElsevierScienceB.V.Allrightsreserved. Keywords:Silicaglass;Ionimplantation;Vacuumultraviolet;Electronspinresonance 1. IntroductionFabrication of optical devices such as opticalfibergratingshasbeenreportedbyourgroupus-ing mega-electron-volt-order ion implantation onsilica-coreopticalfibers[1].Inordertoextendthistechniqueforthefabricationofsilica-basedplanaroptical devices, it is important to understand themechanismsbywhichchangesinopticalpropertiessuch as refractive index are induced by the im-plantedions.Attentionisfocusedontheelectronicstopping energy loss, since it accounts for morethan 99% of the total loss and most defects areinducedthroughthisprocessinthecaseofMeV-orderionimplantation.2. Experimental proceduresSamplesaretwotypesofhigh-puritysilicaglas-ses containing different OH contents, EDC (OHcontent

Radiation effects induced by ion microbeam were studied by a confocal microspectroscopy and an atomic force microscopy (AFM). We investigate two significant radiation effects, defect generation and compaction, which were ascribed to electronic (Eelec) and nuclear stopping powers (Enucl), respectively. Photoluminescence mapping of nonbridging oxygen hole centers at 650 nm reveals the defect formation along the tracks of ions. The surface deformation measured by AFM depends on the width of irradiated by microbeam. Confinement effects from the interface of irradiated and nonirradiated regions are taken into account for the understanding of the correlation between the surface deformations and internal compactions.

In this study, defects induced by ion implantation were investigated by a photoluminescence (PL) microspectroscopy. When H + or He 2+ with high energy (∼MeV) were implanted into silica, two PL bands at 290 and 650 nm were observed under 244 nm excitation. The PL bands at 290 and 650 nm were ascribed to oxygen deficient centers and nonbridging oxygen hole centers, respectively. The PL depth profile analysis shows that these PL centers are distributed throughout the tracks of ions, while they are quenched in the proximity of their projected ranges. Based on the observation on the PL profiles, the formation of the PL centers was ascribed to the energy deposition by electronic stopping power. The role of nuclear stopping power on the defect formation is also discussed.