Preparation of BaTiO₃ Thin Films by Metalorganic Chemical Vapor Deposition Using Ultrasonic Spraying

Abstract

Ferroelectric BaTiO3 thin films were fabricated by metalorganic chemical vapor deposition (MOCVD) at atmospheric pressure. The ultrasonic spraying technique has been used to carry the source materials. The common solutions of barium-diethylhexanoate and diisopropoxy-titanium-bis-acetylacetonate in n-butanol were used as the starting materials. Since the concentration of sources can be controlled in the common solution, this method is more simple and precise than other CVD processes. The films had (110) preferred orientation with increasing temperature. The dielectric constant (ε) and the loss factor (tan δ) of thin film deposited at 550° C were about 250 and 0.1, respectively. The leakage current density was 10-5 A/cm2 at 0.1 MV/cm.

Microstructure and Dielectric Properties of Barium Titanate Film Prepared by MOCVD

“…The deposition rates at T dep = 873 K were 0.16 to 0.21 nm·s −1 almost independent of P O 2 , while those at T dep = 973 K showed the maximum of 0.22 nm·s −1 at P O 2 = 70 Pa. The deposition rates of BaTiO 3 films by MOCVD on literatures [11][12][13][14][15] have ranged from 0.02 to 0.4 nm which were close to those of this study. Figure 7 shows the frequency dependence of relative dielectric constant (ε ) and loss tangent (tan δ) of the BaTiO 3 film prepared at T dep = 873 K and P O 2 = 13 Pa.…”

“…1,2) Several methods such as rf-magnetron sputtering, 3,4) reactive evaporation, 5) laser deposition, 6) chemical solution deposition, 7) sol-gel. [8][9][10] and metal-organic chemical vapor deposition (MOCVD) [11][12][13][14][15] have been applied to prepare BaTiO 3 films. BaTiO 3 films generally consisted of fine grains ranging from several tens to hundreds of nanometers in size, whose dielectric constant might change from several tens to thousands decreasing with decreasing the grain size.…”

“…BaTiO 3 films generally consisted of fine grains ranging from several tens to hundreds of nanometers in size, whose dielectric constant might change from several tens to thousands decreasing with decreasing the grain size. 3,7,10,14) However, the relationship between dielectric properties and microstructure of BaTiO 3 films has not been well understood.…”

“…Many papers have been published on the preparation of BaTiO 3 films by MOCVD, and reported that the dielectric properties were significantly affected by deposition conditions and microstructure. [11][12][13][14][15] In the MOCVD process, many deposition conditions such as partial pressure of source gases, deposition temperature and total pressure should be controlled to obtain high-quality BaTiO 3 films. In published papers, however, the effect of oxygen partial pressure on the dielectric properties has not been reported.…”

(Ba,Sr)TiO3 Thin Films for Dram’s

“…Efforts have been made to improve the volatility of these precursors (without using halogens) by adding adducts such as B(thd)2-tegraglyme [59,60], or Sr(thd)-trien2 [57] or by trying alternatives to thd ligands such as (bis(pentamethylcyclopentadienyl-barium tetrahydrofuran adduct (Ba(Me5C5)2 THF2» [61]. Flash vaporization schemes either from a liquid [52,55,[62][63][64][65] or solid [66] source have been used, because the precursors are not thermally stable. Flash vaporization minimizes problems with thermal decomposition, because only the precursor that is needed at a given time is heated, unlike the mor~ typical bubbler approach.…”