High Aspect Ratio Microstructures in LiNbO₃ Produced by Ion Beam Enhanced Etching

Abstract

This work presents data on damage evolution, volume expansion and etching behavior of LiNbO3 irradiated with Ar+-ions as a function of irradiation and etching conditions. Single crystals of x- and z-cut LiNbO3 were irradiated at room temperature and 15 K using Ar-ions with energies between 60 and 600 keV and ion fluences between 5 × 1012 and 1 × 1015 cm-2. The damage formation investigated with RBS channeling analysis depends on the crystal cut as well as on the irradiation temperature. Irradiation of z-cut material at 300 K causes complete amorphization at 0.4 dpa (displacements per target atom). In contrast 0.27 dpa are sufficient to amorphize the x-cut LiNbO3. Irradiation at 15 K reduces the number of displacements per atom necessary for amorphization to 0.18 dpa. To study the etching behavior ∼500 nm thick amorphous layers were generated via multiple irradiations with Ar+-ions. Etching was performed in HF-solution of different concentration and at different temperatures. The influence of the irradiation and etching conditions on damage formation and etching of LiNbO3 is discussed. In conclusion, negligible etching of the perfect crystal, high etching rates and high contrast of Ion Beam Enhanced Etching (IBEE) allow the realization of high aspect ratio microstructures in LiNbO3.

A coupled effect of nuclear and electronic energy loss on ion irradiation damage in lithium niobate

“…As shown in Fig. 1(a), the nuclear and electronic energy loss profile induced by 0.9 MeV Si + or 21 MeV Si 7+ ions in LiNbO 3 are determined through SRIM 2012 full-cascade simulation code [32,33], in which the density of 4.65 g cm -3 and threshold displacement energies of 25 eV for Li, 25 eV for Nb and 28 eV for O sublattices were used [34]. The SRIM-predicted damage profile is determined from the sum of the predicted Li, Nb and O vacancy concentrations and the replacement events.…”

Ion-beam induced effects at 15K in LiNbO3

“…A very interesting material for optical applications is lithium niobate ðLiNbO 3 Þ because it possesses large electro-optical, piezoelectric and nonlinear optical coefficients. The ion irradiation changes for example the refractive index and the chemical resistance due to the generated defects [1][2][3]. But for a successful application of this method for the fabrication of optical devices, the formation of irradiation induced defects has to be understood.…”

“…But for a successful application of this method for the fabrication of optical devices, the formation of irradiation induced defects has to be understood. To study the primary effects of damage production and accumulation in LiNbO 3 , experiments have to be carried out at very low temperatures to avoid thermally induced annealing of defects. However investigations of the defect formation in sapphire at 15 K showed damage annealing during the Rutherford backscattering spectrometry (RBS) [4].…”

Radiation loss reduction of membrane photonic crystal waveguides

“…[5]). The hexagonal lattice of cylindrical air holes of radius and pitch is patterned into a membrane of height .…”

“…We assume a refractive index of , corresponding roughly to lithium niobate (neglecting the birefringence), a common quadratically nonlinear and electrooptic material (on its patterning see, e.g. [5]). The hexagonal lattice of cylindrical air holes of radius and pitch is patterned into a membrane of height .…”