Spectral changes in Er+- and Tb+-implanted fused silica

Ion beam synthesis can be used to produce glass of new types, the composition of which is beyond the boundaries of glass formation according to the diagrams of states of corresponding systems. The possibility of considerable widening of glass-forming regions is particularly significant for double-component silicate glasses that contain oxides of rare-earth elements, since strong phase separation and crystallization prevents such glasses being obtained by conventional synthesis. The object of our research was Herasil 1 quartz glass subjected to bombardment by Er+ and Tb+ ions (E=100 keV, D=1014–1017cm−2, j<1 μA cm−2). To obtain information on the presence of ions in the glass samples examined, we used spectroscopic methods. Reflection spectra were analyzed within a wide spectral region from 0.2 to 25 μm. The spatial position of ion-synthesized layers and the concentration of implanted impurities were determined by Rutherford backscattering spectroscopy (RBS). In the interval of 200–230 nm, an increase in dose from 1014 up to 1017 cm−2 leads to deterioration of the reflection intensity, and at λ=213 nm, a reflection minimum is observed in the spectrum. Infrared reflection spectroscopy (IRRS) analysis of glasses has revealed that Er+ and Tb+ implantation leads to significant spectral changes: (1) a shift of the maximum of the bands being analyzed (1120 and 475 cm−1) towards low wavenumber; and (2) a decrease in the reflection intensity at the maximum. Both reflection bands are very sensitive to any change in the environment of the atomic grouping Si–O–Si. As a measure of the chemical interaction of implanted dopant with the environment, the value of the frequency shift of the maximum of the band at 1120 cm−1 was used. In our opinion, the spectral peculiarities of the glasses under examination reflect a change in the degree of continual disorder in a modified layer within the structural glass network, as a result of the formation of new phases with the participation of implanted impurities. This process is facilitated by intense energy exchange of structural elements in the thermal spikes.