Study Of Orientation Process Of Piezoelectric Ba₂Si₂TiO₈ Thin Films

The mineral named Fresnoite was discovered by Alfors et al. in 1965. Fresnoite (Ba2TiSi2O8, BTS), has been believed structurally to be a piezoelectric for its noncentrosymmetric tetragonal crystal with lattice parameters a=b=0.852nm and c=0.521nm in space P4bm. Besides of its large tetragonality (c/a) of 0.61 and a unit-cell spontaneous dipole moment of 1.14×10-26C·m, piezoelectric Fresnoite possesses a high electronmechanical coupling constant, a small temperature coefficient of delay (TCD), and a low phase velocity. Moreover, Yamauchi reported the calculated TCD of Fresnoite crystal that is nearly equal to zero. Thus, it is potentially applicable for surface acoustic wave(SAW) devices. It is reported that Fresnoite has a strong optical SHG, and the Fresnoite glass ceramics give up a significant optical SHG. Those nonlinear optical properties in Fresno8ite attract more attention. Efforts have been made to prepare the Fresnorte thin film by various methods.In this paper, it is concluded that the Ba2TiSi2O8 thin films were obtained by magnetron rf sputter, PLD and Sol-Gel techniques. 1. The rf-sputter techniques prepared the Fresnoite thin film is a simple method. The compositions of thin films sputter deposited from near-stoichiometric ceramic targets of Fresnoite (Ba2TiSi2O8) were shifted so that less barium and less titanium were contained in the films. A Ba2TiSi2O8 thin film deposited at a substrate temperature of 600℃ and subsequently annealed at special degrees of temperature for 60min had characteristic of polycrystals.2. Fresnoite (Ba2TiSi2O8) piezoelectric thin films were prepared by Sol-Gel processing using Si(100) substrates. Polycrystalling Ba2TiSi2O8 thin films were obtained at relatively annealing temperatures at 750~900oC.Fresnoite (Ba2TiSi2O8) piezoelectric thin films were deposited on Si(100)3. substrates by pulsed laser deposition(PLD). Successively depositing polycrystalling Ba2TiSi2O8 thin films were obtained at relatively annealing temperatures at 750~800oC.