Preparation Of Oxide Buffer Layer Material And Influence On Structure And Dielectric Property Of BST Thin Film

La_1-xSr_xCoO₃ (LSCO), Gd₂CuO₄ perovskite oxide films, which were used as buffer layers on BST ferroelectric films, became research highlight recently, and the BST film was widely used in microelectronics and optoelectronics. The LSCO and Gd₂CuO₄ thin films were prepared by the Sol-gel method. It made a study of the influence of factors like sol process, raw material component (La/Sr ratio), heating processing technology on performance of buffer layers. And then with the LSCO, Gd₂CuO₄ films as buffer layers of the BST films, the research of influence of the LSCO, Gd₂CuO₄ films on the structure and dielectric properties of the BST films was studied.The effect of La/Sr ratios on the La_1-xSr_xCoO₃ fabricated by sol-gel process was studied. It was found that with the increase of Sr content, the resistance of the LSCO was reduced until the La/Sr=1, so when the Sr content was 50%, the smallest resistance of LSCO (2.5×10-2??cm) was obtained. The effect of gel proportion on the La0.5Sr0.5CoO3 resistance was investigated further, it found that the resistance of the La0.5Sr0.5CoO3 become smaller (2.16×10-2??cm) when the H2O dosage was 6mL, ethanol/acetic-acid was 3, and the diacetone was 2 mL. The effect of regularity of resistance caused by heat-treatment process was investigated by orthogonal test. Results showed that, the lower resistivity (3.29×10-2??cm) of the La0.5Sr0.5CoO3 was obtained at the pretreatment temperature of 300℃, preheated time of 600s and annealing temperature of 750℃. The research of annealing temperature influence on the La0.5Sr0.5CoO3 resistance showed that the best annealing temperature was 750℃, having a resistance value of 2.3×10-2??cm. The La0.5Sr0.5CoO3 film crystallized well, with perovskite structure obviously, the film surface was dense, and grain size was homogeneous.Gd₂CuO₄ film was prepared by sol-gel process, and the influence of heating processing technology on resistivity of the Gd₂CuO₄ film was studied. It showed that the optimum annealing factors were the pretreatment temperature of 300℃, the preheated time of 600s and the annealing temperature of 750℃, having the value of 3.1097?·cm. The influence of annealing temperature on resistivity of the Gd₂CuO₄ film was discussed, and the optimum annealing temperature of Gd₂CuO₄ was 750℃, the minimal Gd₂CuO₄ film resistivity of 0.2990 ??cm was got at this time. The Gd₂CuO₄ film deposited on Pt has the largest dielectric constant of 146.33 at the frequency of 1 kHz, and annealing temperature of 750℃. The dielectric loss was 4.26 in the same condition. The Gd₂CuO₄ film crystallized well, with perovskite structure obviously, the film surface was dense, and grain size was homogeneous, but had vary slightly defect as crack so on.The affect of Sr- doping on the dielectric property of the Gd₂CuO₄ film was studied. The dielectric constant and the loss of the film increased first then decreased with the Sr- doping ratio changing. When the doping ratio was 0.2, the dielectric constant of the film had a value of 211.94 at the frequency of 1 kHz. But compared with the un-doped Gd₂CuO₄ film, the loss of the doped-film decreased. That was, Sr-doping (0.2) not only raised dielectric constant of the Gd₂CuO₄ film, but also decreased the loss.The affect of La- doping on the dielectric property of the Gd₂CuO₄ film was studied. The dielectric constant of La-doped film decreased, and this trend became smaller and smaller as the La-doping ratio increased. The dielectric constant of Gd₂CuO₄ film was 140.83 at the ratio of 0.4 and the frequency of 1 kHz. With the La-doping ratio increased, dielectric loss decreased first then increased, and reached to the maximum at the ratio of 0.4. However, compared with the un-doped Gd₂CuO₄ film, the loss of the doped-film decreased. That was, La-doping decreased the dielectric constant and the loss of Gd₂CuO₄.The Ba_1-xSr_xTiO₃ film deposited on Pt had the largest dielectric constant, the least loss at the x of 0.5. The BST film was perovskite structure, crystallized well,and without cavity and crack. The Ba0.5Sr0.5TiO₃ films deposited on La0.5Sr0.5CoO3/ SiO2/Si, La0.5Sr0.5CoO3/Pt /SiO2/Si, Pt/La0.5Sr0.5CoO3/SiO2/Si respectively with the La0.5Sr0.5CoO3 as buffer layers, results showed that the BST film had higher dielectric constant and smaller loss at the value of 92.13 and 0.66 with the LSCO/SiO2/Si as buffer laver at the annealing temperature of 750℃and the frequency of 1kHz. The Ba0.5Sr0.5TiO₃ films deposited on Gd₂CuO₄/SiO2/Si, Gd₂CuO₄/Pt/SiO2/Si, Pt/Gd₂CuO₄/SiO2/Si respectively with the Gd₂CuO₄ as buffer layers, results showed that the BST film deposited on Pt/GCO /SiO2/Si had higher dielectric constant and the smallest loss at the value of 120.64 and 0.09.