A micro-Raman spectroscopic investigation of He^+-irradiation damage in LiNbO_3

Abstract

Imaging micro-Raman spectroscopy is used to investigate the materials physics of radiation damage in congruent LiNbO 3 as a result of high-energy (~MeV) He + irradiation. This study uses a scanning confocal microscope for high-resolution three-dimensional micro-Raman imaging along with reflection optical microscopy (OM), and scanning electron microscopy (SEM). The tight optical excitation beam in the Raman system allows spatial mapping of the Raman spectra both laterally and normal to the irradiation axis with ≤1 μm resolution. Point defects and compositional changes after irradiation and surface deformation including blistering and microstress are observed in the stopping region. We demonstrate that the probed area of the damaged region is effectively "expanded" by a beveled geometry, formed through off-angle polishing of a crystal facet; this technique enables higher-resolution probing of the ion-induced changes in the Raman spectra and imaging of dislocation line defects that are otherwise inaccessible by conventional probing (depth and edge scan). Twodimensional (2D) Raman imaging is also used to determine the defect uniformity across an irradiated sample and to examine the damage on a sample with patterned implantation. The effects of different He + doses and energies, together with post-irradiation treatments such as annealing, are also discussed.

Influence of annealing on the photodeposition of silver on periodically poled lithium niobate

“…The peak around 732 cm À1 is ascribed to defects representing ilmenite-like stacking faults that originate from the presence of Nb Li and involve a change in the cation sequence. 46,47 Similar to the E(TO 7 ) band, this defect peak shows contrast between domains on the unannealed sample but only varies at domain walls on the annealed sample (Fig. 5(h)).…”

“…Apart from the A(LO) and E(TO) modes, a weak peak around 615 cm À1 , which according to previous reports, originates from forbidden A(TO 4 ) oscillations due to symmetry breaking, was also detected. 45,46 This band originates from Nb octahedron related structural damage, which is most pronounced at domain walls on both samples (Fig. 5(g)).…”

Comparison of waveguide properties and Raman spectroscopic visualization of C and O ion implantation on LaAlO_3 crystals

“…As reported in [15], if a point and extended defects are generated in a crystal, there is a change in the Raman spectra. The micro-Raman spectra of a C implanted is given in Fig.…”

“…This technique is a powerful, nondestructive approach for examining lattice modifications and local microstructural changes. There is a lot of similar work in this area [14,15].…”

Investigation of proton damage in III-V semiconductors by optical spectroscopy

“…In the setup geometry proposed in this work, micro-Raman spectroscopy allows for an accurate non-destructive measure of the vacancy profile [17,18], whereas PL spectroscopy gives insight into the defect levels and their relation to changes in absorption and emission rates. We compare the experimental results with SRIM simulations and found a very good agreement on the proton range in GaAs, but a considerable disagreement for InGaP.…”