Czochralski growth of lithium tetraborate single crystals (original) (raw)
Related papers
Longitudinal horizontally polarized leaky and non-leaky SAW in lithium tetraborate
Physics Letters A, 1994
Unknown LH type leaky and non-leaky waves were theoretically found and examined in lithium tetraborate. The waves have very promising parameters: high velocity, strong piezoelectric coupling, zero power flow angle and small temperature coefficients of delay. The theory of exceptional waves proved to be very useful to investigate the acoustic anisotropy and to search for the cuts where leaky and non-leaky SAW can exist. 0375-9601/94/$07.00
Journal of Crystal Growth, 1981
The liquid phase epitaxy technique has been shown to be successful for developing Nb 5~-richand Na*~modifiedLiNbO 3 films using various flux systems. X-ray diffraction studies showed that the films had a high single crystallinity, and the unit cell aĩ ncreased from 5.143 A for the Li~-richLiNbO3 to 5.155 A for Nat-modified LiNbO3 films. Nat-modified LiNbO3 films, ranging from 10 to 30 pm thickness, showed a reduction in the temperature coefficient of surface acoustic wave (SAW) velocity; the improvement is almost 40%.
Advanced Photonics Research, 2021
Lithium niobate (LiNbO 3 , LNO) is an interesting material exhibiting a range of exotic multifunctionalities, including piezoelectric, pyroelectric, ferroelectric, photoelastic, birefringent, photorefractive, and other properties. These functional properties make it an attractive and important material for exciting applications, including waveguides, [1] surface acoustic wave (SAW) devices, [2] acoustic and electrooptic modulators, [2,3] and second harmonic generators. [4] Currently, high-quality mature growth technologies produce LNO bulk using the Czochralski method, [5] whereby bulk crystals are produced and LNO wafers are cut through the ion-slicing methods. However, ion-slicing can only cut films to around 500 nm and require a secondary annealing step and surface polish to produce usable films for electro and acousto applications. [6] As an alternative, devices based on integrated, epitaxial LNO thin films offer a benefit over bulk material devices, including direct photonic integration in complex devices and heterojunctions, index mismatch waveguides, lower losses, and potential for tunability due to engineering of properties by doping and strain. [7] In the past, research into direct methods of growth for LNO thin films was mostly abandoned in the early 2000s due to the successful ion-slicing method. The literature for developing epitaxial LNO thin films exists for a wide range of different deposition techniques, including metal-organic chemical vapor deposition (MOCVD), [8,9] molecular beam epitaxy (MBE), [7] pulsed laser deposition (PLD), [9-15] sputtering, [16,17] and liquid phase epitaxy (LPE). [18] Growth is performed on a selection of substrates, including lithium tantalate (LiTaO 3 or LTO), LNO, SiO 2 , and c-plane sapphire (Al 2 O 3). C-plane sapphire is the most promising substrate for effective device growth due to its lower cost and well-matched lattice compared with other substrates. Both sapphire and LNO belong to the trigonal crystal system and have threefold symmetry in their unit cells. One of the major hurdles to overcome to develop device quality epitaxial LNO is to grow it without twin rotations. The previously mentioned literature reports usually produce films with 60 in-plane rotated twin
Lithium niobate phononic crystal for surface acoustic waves - art. no. 61281A
2006
The recent theoretical and experimental demonstrations of stop bands for surface acoustic waves have greatly enlarged the potential application field for phononic crystals. The possibility of a direct excitation of these surface waves on a piezoelectric material, and their already extensive use in ultrasonics make them an interesting basis for phononic crystal based, acoustic signal processing devices. In this paper, we report on the demonstration of the existence of an absolute band gap for surface waves in a piezoelectric phononic crystal. The Surface Acoustic Wave propagation in a square lattice, two-dimensional lithium niobate phononic crystal is both theoretically and experimentally studied. A plane wave expansion method is used to predict the band gap position and width. The crystal was then fabricated by reactive ion etching of a bulk lithium niobate substrate. Standard interdigital transducers were used to characterize the phononic structure by direct electrical generation and detection of surface waves. A full band gap around 200 MHz was experimentally demonstrated, and close agreement is found with theoretical predictions.
Japanese Journal of Applied Physics, 2003
Lithium niobate (LiNbO 3) films have been grown at 490 C on diamond-coated silicon substrates by radio-frequency magnetron sputtering. A multi-step process was developed to produce thick layers on diamond with a good structure and a smooth morphology. To assess the structural quality of our films, we performed X-ray diffraction, transmission electron microscopy and atomic force microscopy of the films. The structure is conserved whatever the film thickness. A delay line structure of wavelength of 28 mm was realized and transducers were deposited on top of LiNbO 3. The objective was to verify the high velocity in such a multi-layered structure. The first results indicated a SAW velocity estimated of 8200 m/s and a coupling factor was k 2 around 1%. The film growth, the technology and the electrical measurements are described in this paper.
The anomalous elastic anisotropy of Li 2 B 4 O 7 and its influence on SAW properties
The anomalous elastic anisotropy of Li2B4O 7 caused by the “incorrect” relation between two elastic moduli, c33 and c44, is proved to be responsible for the existence of earlier found undamped longitudinal horizontally polarized (LH) type leaky waves. A simple proof is presented to show that “ray-polarized” quasilongitudinal bulk wave propagating in the plane of reflectional symmetry satisfies the stress-free
2006
If a number of experiments aiming at demonstrating fundamental properties of phononic crystals have been successfully implemented, a need for enlarging both the research and the application fields of these structures has more recently risen. Surface acoustic waves appear as appealing candidates to set a new ground for illustrative experiments involving some different physical concepts from those usually observed when dealing with bulk waves. The possibility of a direct excitation of these surface waves on a piezoelectric material, and their already extensive use in ultrasonics also make them an interesting basis for phononic crystal based, acoustic signal processing devices. In this work, wave propagation in a square lattice, piezoelectric phononic crystal consisting of air holes etched in a lithium niobate matrix is both theoretically and experimentally investigated. The crystal was fabricated by reactive ion etching of a bulk lithium niobate substrate. Standard interdigital transducers were used to characterize the phononic structure by direct electrical generation and detection of surface waves. A full band gap around 200 MHz was experimentally demonstrated, and close agreement is found with theoretical predictions.
The need for high-frequency, wide-band filters has instigated many developments based on combining thin piezoelectric films and high acoustic velocity materials (sapphire, diamond-like carbon, silicon, etc.) to ease the manufacture of devices operating above 2 GHz. In the present work, a technological process has been developed to achieve thin-oriented, single-crystal lithium niobate (LiNbO3) layers deposited on (100) silicon wafers for the fabrication of radio-frequency (RF) surface acoustic wave (SAW) devices. The use of such oriented thin films is expected to favor large coupling coefficients together with a good control of the layer properties, enabling one to chose the best combination of layer orientation to optimize the device. A theoretical analysis of the elastic wave assumed to propagate on such a combination of material is first exposed. Technological aspects then are described briefly. Experimental results are presented and compared to the state of art.
Plate Acoustic Waves in ZX-cut Lithium Niobate
Plate acoustic waves (PAW) propagating along X-axis in the Z-cut wafer of a single crystal of lithium niobate are considered theoretically and experimentally. For eight lowest PAW modes, the dispersion curves for wavenumber k(f) are calculated by the equations of motion and electrodynamics, by the Finite Element Method, and then measured experimentally. The spectra k(f) obtained by the numerical solution and FEM-simulation are in good agreement, and experimental measurements agree with theoretical predictions. The PAW modes are identified by the components of their total acoustic displacements and cutoff frequencies. Analysis of the longitudinal and normal acoustical displacements permits to find PAW mode capable for usage in ultrasonic actuators. The results obtained may be useful for ultrasonic transducers, acousto-electronic and acousto-optic applications, and ultrasonic motors/actuators fabricated in the Z-cut ferroelectric lithium niobate wafers including periodically poled wav...
Journal of Communications Technology and Electronics
The interaction of light with the bulk acoustic wave that is excited from the surface of the lithium niobate crystal is experimentally studied. A prototype of the acousto-optic device that employs the XY-cut crystal and the optimized (Y-13°)-cut crystal is presented. Diffraction efficiencies of 1 and 2 %/W are obtained for the first and second prototypes, respectively. It is demonstrated that the polarization characteristics of the device differ from the conventional characteristics by the dependence on the structure of the acoustic beam. An original method for the excitation of the ultrasonic beam can be used in the acousto-optic devices for light control.