Low-Temperature Preparation and Properties of Ferroelectric Thin Films Using Excimer UV Irradiation

铁电Bi_4Ti_3O_<12> (BIT)薄膜在非易失性铁电随机存取存储器（NvFRAM）中的应用得到了广泛的研究。与SrBi_2Ta_2O_9（SBT）及其相关材料相比，BIT薄膜具有加工温度低、结晶度高、剩余极化（P_r）大、矫顽力场（E_c）小、居里温度（T_c）高的特点。而多晶BIT薄膜的P_r值低至约7 ~ 10 μC/cm^2。近年来，稀土（Ln=La, Pr， Nd和Sm）掺杂BIT （BLnT）薄膜得到了广泛的研究。特别是Bi_<4-x>Nd_xTi_3O_<12> (BNT)薄膜因其优于其他稀土掺杂BIT薄膜的铁电性能而备受关注。本文利用准分子紫外灯，采用化学溶液沉积法（CSD）研究了铁电（Bi, Nd）_4Ti_3O_<12> (BIT)薄膜的化学溶液处理和性能。准分子紫外线照射对沉积BNT前驱体膜结晶、微观结构的影响。利用金属有机溶液，采用自旋镀膜技术在Pt(200nm)/TiO_x(50nm)/SiO_2/Si基底上沉积了BNT前驱体膜。在O2气氛下，准分子紫外照射沉积BNT前驱体膜，可以有效去除BNT薄膜中的有机物，提高其铁电性能。准分子紫外辐照合成的BNT薄膜取向随机，具有强（117）反射，微观结构均匀，晶粒尺寸在100 ~ 150 nm之间，表面光滑。在准分子紫外辐照下，BNT薄膜在550℃低温下结晶，P-E滞回线饱和，P_r为12.7 μC/cm^2， E_c为88 kV/cm。他们的薄膜具有10^9次循环的相对良好的疲劳耐久性和小于3 × 10^<-7>的良好泄漏电流特性。少

Ferroelectric Bi_4Ti_3O_<12> (BIT) thin films are extensively investigated for applications in nonvolatile ferroelectric random access memories (NvFRAM). Compared with SrBi_2Ta_2O_9(SBT) and its related materials, BIT thin films are known to crystallize at low processing temperature with a high crystallinity and to have a large remanent polarization (P_r), a small coercive field (E_c) and a high Curie temperature (T_c). However, P_r values of polycrystalline BIT thin films were seen to be as low as approximately 7-10 μC/cm^2. Recently, rare-earth (Ln=La, Pr, Nd and Sm)-doped BIT (BLnT) thin films have been intensively investigated. In particular, Bi_<4-x>Nd_xTi_3O_<12> (BNT) thin films have been attacting great attention for their ferroelectric properties which are superior to other rare earth-doped BIT thin films.In this work, chemical solution processing and properties of ferroelectric (Bi, Nd)_4Ti_3O_<12> (BIT) thin films were investigated by the chemical solution deposition (CSD) m … More ethod using excimer UV lamp. The effects of excimer UV irradiation to as-deposited BNT precurosor films on crystallization, microstructure.BNT precursor films were deposited on Pt(200nm)/TiO_x(50nm)/SiO_2/Si substrates by the spin-coating technique using metal-organic solutions. The excimer UV irradiation onto as-deposited BNT precursor films in O2 atmosphere was greatly effective in removing organic species of the BNT thin films and improving the ferroelectric properties. The synthesized BNT thin films using excimer UV irradiation showed a random orientation with a strong (117) reflection and a homogeneous microstructure consisting f grain sizes of 100-150 nm with a smooth surface. BNT thin films crystallized at a low temperature of 550℃ through the excimer UV irradiation process and showed a well-saturated P-E hysteresis loop with a P_r of 12.7 μC/cm^2 and E_c of 88 kV/cm.Their films exhibited a relatively good fatigue endurance up to 10^9 cycles and a good leakage current property with less than 3 x 10^<-7>. Less