CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

CHAPTER 5. DIRECT LIQUID INJECTION CHEMICAL VAPOR DEPOSITION OF
5.1 Introduction
FERROELECTRIC BARIUM TITANATE FILMS
As previously introduced, barium titanate (BaTiO3) possesses excellent properties (high
dielectric constants, ferroelectric, optoelectronic, etc.,) for application in certain advanced
electronic devices, and great efforts have been dedicated to the deposition of high quality single
crystal barium titanate thin films in the past decades.[113-115] Among these studies, chemical
vapor deposition is uniquely preferred due to its capability of large area and conformal
deposition. One challenge for CVD growth of barium titanate thin film is the availability of
volatile and thermally stable barium precursor. The use of metal organic β-diketonate barium
precursor Ba(thd)2 {bis(2,2,6,6-tetramethyl-3,5-heptanedionato) barium (II)} has been widely
studied in CVD method, but the high temperature (~250˚C) needed to vaporize the solid
precursor would result in precursor degradation (sintering effect) and thus affect run to run
repeatability.[135,138,139] Besides, the precise control of rate of introduction of barium
precursor into the reaction chamber is almost impossible. In this chapter, DLICVD technique as
used in the deposition of nickel ferrite is used for deposition of barium titanate films. For this
technique, by dissolving metal organic precursors into an appropriate solvent, few advantages
can be achieved over direct vaporization of the solid phase precursors. For example, low
vaporization temperature, accurate control of liquid flow rate, and minimization of precursor
oligomerization effect, etc.. In our work, Ba(hfa)2•tetraglyme {Ba(C5HF6O2)•(C10H22O5)} and
Ti(thd)2(OPr i )2 {Ti(C11H19O2)2(C3H7O)2} are dissolved in toluene as the precursor source. The
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