Surface alterations of SiO2 optics by 9.8 and 8.5 eV laser photons

Optical nonlinearity in glasses: the origin and photo-excitation effects

“…Second, bandgap excitations (Fig. 4(i)) at room temperature seem to produce markedly different effects on SiO 2 and As 2 S 3 , i.e., defect formation [23] and photodarkening (PD), respectively [24]. Hosono et al suggest for SiO 2 that bandgap photons excite unstrained normal bonds (≡Si-O-Si≡), creating Si wrong bonds and interstitial oxygen as forms of peroxy-radicals (PORs, ·O-O-Si≡) and O 2 [31].…”

“…super-gap (ћω > E g ) Si-Si [20], small ring [21] photodecomposition [22] bandgap (ћω ≃ E g ) Si-Si [23] PD, +ΔV, +Δn (D 0 at low T) [24] sub-gap (ћω < E g ) -ΔV and +Δn [25] by 7.9eV 2S excitation [26], E' centers and NBOHCs by 2P [27] PD, +ΔV, +Δn by 2.0eV 1P excitation [28] half-gap (ћω ≃ E g /2) E', -ΔV and +Δn by 6.4eV photons [25] PORs destruction by 5.0eV photons [29] 1P excitation gives no effects 2P excitation gives +Δn and As-As, but no PD [30] Although research trends in SiO 2 and As 2 S 3 are substantially different, reflecting different bandgap energies of ~9 eV and 2.4 eV, we can point out several interesting features. First, responses to super-gap excitations appear to resemble.…”

Removal of Carbon Contamination on Si Wafers with an Excimer Lamp

“…Actually, an argon excimer laser light has the ability to convert quartz glass or silicon nitride into elemental silicon without any chemical assist. [4,8] In this case, the intense laser light formidably raises the material temperature at the same time. Fortunately, for the wafer cleaning, the excimer lamp provides light with a moderate power.…”

“…Takigawa et al demonstrated experimentally that an Ar excimer laser is capable of the dissociation of SiO 2 only by the irradiation. [4] This is because the photon energy (9.8 eV) is larger than the binding energy of Si-O bonds. Hence, a light source of high photon energy has the possibility to realize a new process technology.…”

Crucial dependence of excimer laser toughness of “wet” silica on excess oxygen

“…The microscopic processes which occur in Si-O network under VUV excitation by high energy photons are still far from completely understood. VUV or multiphoton UV irradiation is capable of inflicting a massive damage to SiO 2 network, as illustrated by recently observed steady desorption of Si-O molecules and Si and O atoms or positive ions from the surface of F 2 -laser irradiated a-SiO 2 [20] or formation of elemental Si on Ar 2 (ħω = 9.8 eV) laser-irradiated surfaces of SiO 2 [21]. Another interesting recent finding is the creation of NBOHC in very large concentrations in surface layer by far VUV synchrotron irradiation [22].…”