Ultrathin Slices of Ferroelectric Domain-Patterned Lithium Niobate by Crystal Ion Slicing
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Ultrathin Slices of Ferroelectric Domain-Patterned Lithium Niobate by Crystal Ion Slicing David A. Scrymgeour1 and Venkat Gopalan1, Tony E. Haynes2, and Miguel Levy3 Materials Research Laboratory, Pennsylvania State University, University Park, PA 16802; 2 Solid State Division, Oak Ridge National Laboratory, Bldg. 3003, MS-6048, P. O. Box 2008, Oak Ridge, TN 37831 3 Physics Department Michigan Technological University, Houghton, MI 49931
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ABSTRACT We report the successful fabrication of 6 µm thick slices from a ferroelectric domain microengineered LiNbO3 wafer device using the crystal ion slicing technique. The device was created by micropatterning ferroelectric domains in a bulk 0.3 mm thick wafer of z-cut LiNbO3, followed by ion-implanting with 3.8 MeV He+ ions to a fluence 5 x 10+16 ions/cm2 to create a damage layer at a well defined depth from the surface. Etching away this damaged layer in dilute hydrofluoric acid results in a liftoff of the top slice in which the ferroelectric domain patterns are left intact. The influence of annealing conditions on liftoff time and depth of etch lines was studied. Helium-Neon laser light was successfully coupled into the device. Due to unintentional breakage of the polished input and output faces, the electro-optic scanning performance has not been characterized so far. INTRODUCTION The ability to control the angular position of a laser beam with high speed is of interest in many applications including optical communications, optical data storage, laser printing, and display technologies. Active solid-state electro-optic scanners based on micro-patterned LiNbO3 have several advantages over mechanical and other systems including small device size and high operating speed (intrinsic response frequencies >100GHz). However, widespread application of these devices is currently limited because of the large voltage required to operate devices fabricated in single crystal wafers. A solution to this problem is to make the devices thinner, thereby reducing the operating voltage for a fixed driving electric field. However, the fabrication of high-quality thin films of LiNbO3 has so far been elusive. Techniques such as pulsed laser deposition[1] and chemical vapor deposition[2] yield polycrystalline films, which have electrooptic responses much smaller than single crystal bulk LiNbO3. Further, the light propagation losses in thin films are still high, which makes them unsuitable for optical devices.[3] Recently, an ion-implantation-based technique called crystal ion slicing (CIS), has been reported for making thin slices of ferroelectric lithium niobate.[4,5] CIS allows a free standing micron-thick single crystal film to be fabricated from a bulk crystal. In CIS, ion implantation is used to define a damaged sacrificial layer several microns below the surface. This sacrificial layer is then etched away by immersion in a dilute hydrofluoric acid solution. The large etch selectivity of the damage layer over the rest of the crystal allows for the lifting off of a thin film, whose thicknes
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