Domain inversion in LiNbO 3 and Zn-doped LiNbO 3 crystals by the electron-beam irradiation of the nonpolar Y -surface
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Domain inversion in LiNbO3 and Zn-doped LiNbO3 crystals by the electron-beam irradiation of the nonpolar Y-surface L. S. Kokhanchik • T. R. Volk
Received: 25 April 2012 / Revised: 5 September 2012 / Published online: 21 November 2012 Ó Springer-Verlag Berlin Heidelberg 2012
Abstract Individual domains and domain gratings were fabricated on nonpolar Y-cuts of LiNbO3 and LiNbO3-Zn crystals by electron beam irradiation. The domains which nucleated in the irradiation points are frontally growing along the direction ?Z within a thin (of about several microns) surface layer. The regularities of this motion are discussed in the framework of the approach to formation of space-charge fields under e-beam charging of insulators. The obtained dependency of the domain length on the exposure time permits us to propose the viscous-friction mechanism for the observed frontal domain growth. The velocity of the frontal growth in LiNbO3-Zn is higher than in LiNbO3 obviously due to a decreased number of pinning centers at the Nb-antisites. In LiNbO3-4 %Zn crystals planar domain gratings were fabricated by means of pointto-point irradiations along the X- and Z-directions with specified distances between the irradiation points. It is shown that the domain gratings are generated by a total P field of point charges ~ E ¼ ni¼1 ~ Ei , where Ei is the spacecharge field induced in any irradiation point, and n is the number of points. Some preliminary estimates indicate that the frontal growth of domains under e-beam irradiation occurs at fields E \ Ec.
L. S. Kokhanchik Institute of Microelectronics Technology and High Purity Materials of the Russian Academy of Sciences, Chernogolovka, 142432 Moscow, Russia T. R. Volk (&) Institute of Crystallography Russian Academy of Sciences, Leninski prospect 59, 119333 Moscow, Russia e-mail: [email protected]
1 Introduction Ferroelectric domain structures with specified design are of particular interest for optical frequency conversion. The most prominent material for these aims is lithium niobate due to the large quadratic nonlinear susceptibility and a high stability of the regular domain structures (RDS) fabricated by various methods. One of the topical problems is the frequency conversion in optical waveguides based on LiNbO3. Certain future applications, such as nonlinear photonic crystals or optical schemes with semiconductor laser diodes require RDS periods of about 2–4 lm or even of submicron range. The preparation of so small-scaled RDS in LiNbO3 with the aid of the field method (by means of applying high voltages to a patterned electrode deposited on the polar surface) meets certain technological and fundamental problems. Additionally, the field method does not allow to produce RDS on the nonpolar (X- or Y-) surfaces which sometimes are more preferable for producing optical waveguides than the polar Z-cut. The most promising methods for the creation of microdomain arrays use local poling with the help of electron-beams in a scanning electron microscope (SEM) or applying dc-voltages to an AFM ti
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