Photoluminescence of Oxygen Implanted Silica
David Coss
April 23, 2004
Abstract:
To determine the effects of oxygen implantation on silica optical properties, the photoluminescence(PL) of oxygen
implanted silica has been studied. Silica samples implanted at energy of 300keV were used, with varying oxygen
implantation doses ranging from 1x1014ions/cm2 to 5x1015ions/cm2. PL was preformed on the samples with
excitation wavelengths of 240nm, 248nm, and 257nm, with excitation and emission slit widths of 2.5nm. The PL,
measured from 260nm to 350nm, had a magnitude related to the dosage of implanted oxygen ions, inversely in one
case and directly in another. The effects of varying doses on PL will be discussed further.
Introduction:
Defects in silica have a noticeable effect on devices that utilize their optical properties, such as fiber optics
and Bragg Gratings. A better understanding of the cause and effect of these defects can lead to an
improvement of optical devices.
When ions are implanted on the surface of silica, defects are created. A defect is any change in the
arrangements of the atoms in silica. For example, an implanted ion can eject an atom in silica from its place
in the crystal lattice, causing a deficiency.
Experimentation:
The photoluminescence(PL) of oxygen implanted samples of silica was recorded on samples of
implantation dosages of 1x1014ions/cm2, 5x1014ions/cm2, 1x1015ions/cm2, 3x1015ions/cm2, 1x1015ions/cm2.
Each sample was implanted with energy of 300keV. PL was measured for each sample at excitation
energies of 4.83eV(257nm), 5.01eV(248nm), and 5.17eV(240nm). The emitted wavelengths recorded
ranged from 260nm to 350nm, with both emission and excitation slit widths of 2.5nm. Once the data was
collected, graphs were made for each dosage, plotting PL intensity, in arbitrary units(a.u.), versus emission
wavelength, in nanometers. These graphs are shown as Figures 1-5. Figures 6-8 plot similar graphs except
lines of same excitation energies are plotting on individual graphs for each of the three excitation energies.
Results:
The 4.83eV band re-emitted with a peak at 4.4eV. The intensity of the 4.83eV increased directly
proportional to increasing oxygen dosage, until the 3x10 15ions/cm2 sample. This is shown in Figure 8. The
5.01eV band re-emitted with a peak at 4.3eV. According to the data shown in Figure 7, PL intensity of the
5.01eV band is inversely proportional to oxygen dosage, with the exception of the 1x10 14ions/cm2 sample.
The 5.17eV band re-emitted with a peak at 4.4eV, similar to the 4.83eV band. The difference, as shown in
Figure 6, is the 5.17eV has to groups of similar PL intensities, where the relation of intensity to oxygen
dosage is less clear.
Conclusion:
Based on the data collected, some conclusion can be made about the effects of oxygen implantation of
silica. There exists three distinct photoluminescence bands, 4.83eV, 5.01eV, and 5.17eV. The direct
relationship of PL intensity with oxygen dosage in the 4.83eV sample seems to imply that this band is due
to oxygen excess. This may be due to the fact that the oxygen ions are displacing the oxygen atoms in the
silica lattice, only to replace them. Oxygen excess is further supported by the point in which the direct
Coss 2
relation ends, with the 3x1015ions/cm2. It may be that at this point the silica becomes saturated and no more
peroxy centers are being formed.
The 5.01eV samples are believed to be due to Oxygen vacancy. The inverse relation of PL intensity and
oxygen dosage supports this hypothesis.
The question prompting further study is the cause of the 5.17eV band. It may be that the 5.17eV band is
excited at 5.01eV and therefore emits 280nm radiation. However, there is less data to support the cause of
this band. Further study most be conducted, and currently is on going.
Data:
Figure 1, 1x1014ions/cm2
Coss 3
Figure 2, 5x1014ions/cm2
Figure 3, 1x1015ions/cm2
Figure 4, 3x1015ions/cm2
Coss 4
Figure 5, 5x1015ions/cm2
Figure 6, All samples with excitation of 240nm(5.17eV)
Coss 5
Figure 7, All samples with an excitation of 248nm(5.01eV)
Figure 8, All samples with an excitation of 257nm(4.83eV)
Coss 6
References:
[1] R. H. Magruder III, R.A. Weeks, R.A. Weller, Non-Crystalline Solids, 322 (2003) 58-67