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

MOCVD工艺存在金属有机原料在腔室和管材内相互反应，原料沉积在基体上反应复杂的问题。本研究旨在以氧化铁电薄膜为模型材料，阐明MOCVD法中氧化薄膜的沉积机理。此外，利用透射电镜（TEM）研究了在硅衬底上MOCVD沉积外延铁电薄膜所需的PLD缓冲层。将原位FTIR机理引入冷壁型MOCVD室。研究了TiO_2在Ti(O-i-C_3H_7)_4 （TTIP）基体上的气相分解和沉积机理。TiO_2薄膜的组成、结晶度和微观结构随衬底温度的变化而变化。在低温下（300℃），薄膜的微观结构与高温下沉积的薄膜相比较为粗糙。这是由底物中残留的C-H片段引起的，FTIR光谱检测到更多。由于MO原料源的分解速率与环境温度有关，TTIP在600℃时也不能完全分解。分解和未充分分解的原料到达基材上，基材表面起催化剂作用，增强氧化作用。用Pb(DPM)_2作为Pb源，用TTIP作为Ti源，在MgO衬底上沉积PbTiO_3。当初始气体的标称成分Pb/Ti= 1或更高时，所得薄膜的化学计量量为PbTiO_3。多余的铅被蒸发掉了。Pb(DPM)_2与TTIP在同一腔室中加热，Pb(DPM)_2在1600cm^<-1>处的吸光度峰消失，在1260cm^<-1>处产生新的吸光度峰。这表明存在具有Pb-O-C-Ti键的中间化合物。采用脉冲源MOCVD法制备了4种不同供酸方式的PZT薄膜。通过控制PZT/MgO和PZT/Pt/Ti/Si的脉冲宽度来确定最佳条件。与Ar交替供应PbTiO_3和PbZrO_3可获得最光滑的表面。少

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