Etching of Ion Irradiated LiNbO[sub 3] in Aqueous Hydrofluoric Solutions

Abstract

Homogeneously damaged surface layers of a thickness of 400 nm were generated in x-cut LiNbO 3 single crystals using multipleenergy Ar + -irradiation to study the etching behavior in aqueous HF solutions. Rutherford backscattering/channeling analysis was applied to investigate the damage formation. Different acid temperatures and concentrations were used, showing that the etching rate can be increased by increasing the temperature from 24 to 55°C maintaining the high contrast of the technique. The dissociation of HF in aqueous solution is discussed, and reaction kinetics well established for the HF etching of SiO 2 are then applied to obtain information on the etching mechanism. Therefore, the concentration dependence of the etching rate is analyzed and it is found that the etching process can be described as an attack of either HF or HF 2 − , which is catalytically supported by the presence of H + ions.

Characterization of selective etching and patterning by sequential light- and heavy-ion irradiation of LiNbO3

“…In fact, Schrempel et al showed that [3] in Ar + -irradiated X-cut LiNbO 3 , the etching rate using 3.7% HF saturates when the damage reaches $0.4 dpa. In addition, it has been found that the etching rate of this Ar + -irradiated X-cut LiNbO 3 is dependent on the acid temperature [17]. In particular, in Ref.…”

“…In particular, in Ref. 17, it was determined that the etching rate in such ion-irradiated sample can be increased from $20 nm/min to $200 nm/min when the temperature was raised from 24°C to 55°C. Note that prior literature results also suggest that the involvement of different defect-generation mechanisms such as using light-ion or swift heavy-ion irradiation may result in somewhat different etching results.…”

Photonic microstructures in lithium niobate by potassium hydroxide-assisted ion beam-enhanced etching

“…To quantify this behavior, etch rates are measured for a series of samples that are treated with different normalized fluences. 11 for HF. The resulting etch rate is below 0.006 nm/min and can be neglected, which is an important prerequisite for highly selective etching.…”

“…11 Because a defect concentration of 0.4 displacements per atom (dpa) corresponds to a complete amorphization of the material, 6 the experiments were carried out between 0.1 and 0.6 dpa. For all of the experiments in this work, argon ions with energies of 60, 150, 360, and 600 keV were used, where the energies and fluences were designed to result in a homogeneously damaged layer of 450 nm in thickness.…”

“…3 Another approach, and the focus of the presented work, is ion beam-enhanced etching (IBEE) 4,5 that can be described conceptually as follows: Ion beam irradiation causes modifications of the crystal structure that depend upon ion species, fluence, and energy. 11 While preceding investigations have exclusively report on wet etching based on HF acid, 11 we study the etching mechanism of ion beam-irradiated LN in potassium hydroxide (KOH) solutions for the first time. 6 The etch rates of irradiated and virgin LN are very different because unprocessed LN possesses a high chemical stability and a negligible etch rate.…”