Chemical interaction in gaseous phase of MOCVD raw materials and self-assembled ferroelectric thin films

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MOCVD process has a problem that the metalorganic raw materials react with each other in the chamber and tubing, moreover the raw material deposits on the substrate with complex reaction. This study aimed to clarify the deposition mechanism of the oxide thin film in the MOCVD method using oxide ferroelectric thin film as a model material. In addition, the appropriate buffer layers by PLD for depositing the epitaxial ferroelectric thin film on Si substrate by MOCVD were examined by TEM.In-situ FTIR mechanism was introduced into cold-wall type MOCVD chamber. Decomposition in gaseous phase and deposition mechanism of TiO_2 on the substrate of Ti(O-i-C_3H_7)_4 (TTIP) was examined. TiO_2 thin films were varied as composition, crystallinity and microstructures with substrate temperature. At low temperature (300℃), the microstructure of the thin film was rough compared with the thin film deposited on higher temperature. This was caused by the residual C-H fragments in the substrate, that was … More detected by the FTIR spectrum. As the decomposition rate of the raw MO source depends on the ambient temperature, the decomposition was not complete even at 600℃ in case of TTIP. Decomposed and insufficiently decomposed raw material is reached on the substrate, substrate surface acts as catalyst and oxidation are enhanced.Pb(DPM)_2 for a Pb source and TTIP for a Ti were used for deposition of PbTiO_3 on MgO substrate. When the nominal composition of the initial gas was Pb/Ti= 1 or higher, the obtained thin film showed stoichiometric PbTiO_3. The excess Pb was evaporated. Heating of Pb(DPM)_2 and TTIP in same chamber showed the extinction of the absorbance at 1600cm^<-1> peak and produce the new peak at 1260cm^<-1> in Pb(DPM)_2. This indicates the existence of intermediate compounds with Pb-O-C-Ti bond.Pulsed source MOCVD method was applied to make PZT thin film with 4 different sour supply methods. There were optimum conditions by controlling the pulse width for both PZT/MgO and PZT/Pt/Ti/Si. Alternate supply of PbTiO_3 and PbZrO_3 with Ar produced most smooth surface. Less