X-ray diffraction using focused-ion-beam-prepared single crystals

Abstract

High-quality single-crystal X-ray diffraction measurements are a prerequisite for obtaining precise and reliable structure data and electron densities. The single crystal should therefore fulfill several conditions, of which a regular defined shape is of particularly high importance for compounds consisting of heavy elements with high X-ray absorption coefficients. The absorption of X-rays passing through a 50 mm-thick LiNbO 3 crystal can reduce the transmission of Mo K radiation by several tens of percent, which makes an absorption correction of the reflection intensities necessary. In order to reduce ambiguities concerning the shape of a crystal, used for the necessary absorption correction, a method for preparation of regularly shaped single crystals out of large samples is presented and evaluated. This method utilizes a focused ion beam to cut crystals with defined size and shape reproducibly and carefully without splintering. For evaluation, a single-crystal X-ray diffraction study using a laboratory diffractometer is presented, comparing differently prepared LiNbO 3 crystals originating from the same macroscopic crystal plate. Results of the data reduction, structure refinement and electron density reconstruction indicate qualitatively similar values for all prepared crystals. Thus, the different preparation techniques have a smaller impact than expected. However, the atomic coordinates, electron densities and atomic charges are supposed to be more reliable since the focused-ion-beam-prepared crystal exhibits the smallest extinction influences. This preparation technique is especially recommended for susceptible samples, for cases where a minimal invasive preparation procedure is needed, and for the preparation of crystals from specific areas, complex material architectures and materials that cannot be prepared with common methods (breaking or grinding).

Direct graphene synthesis on LiNbO3 substrate by C implantation on Cu covering layer

“…Although both Cu and Ni are face-centered cubic structures, as shown in figure 2, their (111) faces have lattice constants of 5.112 Å and 4.984 Å, respectively. When combined with a Z-cut LiNbO 3 substrate with a lattice constant of 5.152 Å [37], the Cu/LiNbO 3 structure has a small lattice mismatch and is more likely to form flat and stably bonded metal film, which is essential for the formation of graphene.…”

Thermodynamic Study of Adsorption Capacity between Metal Film and Optical Crystal: Adsorption Energy of Ni Films on LiNbO3 Substrates

“…LiNbO 3 (PDF#: 20-0631) crystal is a ferroelectric crystal that belongs to the R3c space group at temperatures below 1210 • C. When represented by a hexagonal coordinate system, the lattice parameters of LiNbO 3 crystal measured by experiments are a = b = 5.1516 Å, c = 13.869 Å, α = β = 90 • , γ = 120 • [34], and the coordinates of the atoms are shown in Table 1. A LiNbO 3 unit cell was built with the above parameters, and then the geometry optimization of the LiNbO 3 unit cell was performed using the ultrasoft pseudopotential of the planewave, to obtain a more stable crystal structure.…”

Geometrical prediction of cleavage planes in crystal structures

“…The structure of LiNbO 3 used for the calculations (Weigel et al, 2020 (organized in the same way as Figs. 7 and 8) illustrate the output for the case of ( 011) planes in quartz.…”

“…LiNbO 3 crystallizes in the space group type R3c (Weis & Gaylord, 1985;Weigel et al, 2020), Laue class " 3 3m. Table 6 summarizes the relevant structural information.…”