脉冲激光沉积Ba0.5Sr0.5TiO3、Pb0.5Ba0.5TiO3和Pb0.5Sr0.5TiO3薄膜及其介电性质

采用脉冲激光沉积法，在Pt／Ti／SiO2／Si基底上分剐制备厚度为350nm的Ba0.5Sr0.5TiO3(BST)、Pb0.5Ba0.5TiO3(PBT)和Pb0.5Sr0.5TiO3(PST)薄膜并研究了它们的介电性质。XRD显示，在相同的制备条件下三者具有不同的择优取向,PST具有(110)择优取向，PBT具有(111)择优取向，而BST则是混合取向。SEM显示三者样品表面均匀致密，颗粒尺寸大约在50nm至150nm之间。PST与BST、PBT相比有更高的介电常数，在频率为10kHz时，分别为874、334和355，而损耗都较低，分别为0．0378、0．0316和0．0423，同时PST漏电流也是最小的。测量薄膜的C-V特性扣铁电性能表明室温下BST呈现的是顺电相，PST和PBT则呈铁电相。本文也测量了薄膜在不同频率下的介电温度特性，BST、PBT和PST均表现出频率弥散现象，即随着频率的降低．居里温度降低而介电常数会升高。并测得BST和PST的居里温度分剐为-75和150℃。而PBT的居里温度在250℃以上。本文研究表明：与BST相比较，PBT的介电常数与之相近，漏电流较大；而PST具有高介电常数，较小的漏电流和较大的电容-电压调谐度，在相关半导体器件中的应用将有很大的潜力。

Pulsed-laser deposition of Ba0.5Sr0.5TiO3,Pb0.5Sr0.5TiO3 and Pb0.5Ba0.5TiO3 films and their dielectric properties

Ba_(0.5)Sr_(0.5)TiO_3 (BST), Pb_(0.5)Ba_(0.5)TiO_3 (PBT) and Pb_(0.5)Sr_(0.5)TiO_3 (PST) films have been deposited on Pt/Ti/SiO_2/Si substrates by pulsed-laser deposition technique. The X-ray diffraction (XRD) indicates that BST, PBT and PST films have different preferential orientation. The dielectric constant of PST film was significantly higher than those of PBT and BST, while the dielectric loss of the films are all below 0.05. The capacitance-voltage characteristics and ferroelectric properties of the three films have also been studied. Comparing with BST and PBT films, PST film has high dielectric constant, low leakage current and a large-scale variation of the dielectric constant by direct current biasing fields applied.