Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States.
ACS Appl Mater Interfaces. 2016 Aug 24;8(33):21446-53. doi: 10.1021/acsami.6b05700. Epub 2016 Aug 15.
Two-dimensional (2D) ferroelectric films have vast applications due to their dielectric, ferroelectric, and piezoelectric properties that meet the requirements of sensors, nonvolatile ferroelectric random access memory (NVFeRAM) devices, and micro-electromechanical systems (MEMS). However, the small surface area of these 2D ferroelectric films has limited their ability to achieve higher memory storage density in NVFeRAM devices and more sensitive sensors and transducer. Thus, conformally deposited ferroelectric films have been actively studied for these applications in order to create three-dimensional (3D) structures, which lead to a larger surface area. Most of the current methods developed for the conformal deposition of ferroelectric films, such as metal-organic chemical vapor deposition (MOCVD) and plasma-enhanced vapor deposition (PECVD), are limited by high temperatures and unstable and toxic organic precursors. In this paper, an innovative fabrication method for barium titanate (BaTiO3) textured films with 3D architectures is introduced to alleviate these issues. This fabrication method is based on converting conformally grown rutile TiO2 nanowire arrays into BaTiO3 textured films using a simple two-step hydrothermal process which allows for thickness-controlled growth of conformal films on patterned silicon wafers coated with fluorine-doped tin oxide (FTO). Moreover, the processing parameters have been optimized to achieve a high piezoelectric coupling coefficient of 100 pm/V. This high piezoelectric response along with high relative dielectric constant (εr = 1600) of the conformally grown textured BaTiO3 films demonstrates their potential application in sensors, NVFeRAM, and MEMS.
二维（2D）铁电薄膜由于其介电、铁电和压电性能满足传感器、非易失性铁电随机存取存储器（NVFeRAM）器件和微机电系统（MEMS）的要求，因此具有广泛的应用。然而，这些 2D 铁电薄膜的小表面积限制了它们在 NVFeRAM 器件中实现更高存储密度和更灵敏的传感器和换能器的能力。因此，为了创建更大的表面积，已经积极研究了用于这些应用的共形沉积铁电薄膜。大多数目前开发的用于共形沉积铁电薄膜的方法，如金属有机化学气相沉积（MOCVD）和等离子体增强化学气相沉积（PECVD），都受到高温和不稳定、有毒的有机前体的限制。本文介绍了一种用于具有 3D 结构的钛酸钡（BaTiO3）织构化薄膜的创新制造方法，以缓解这些问题。该制造方法基于使用简单的两步水热工艺将共形生长的金红石 TiO2 纳米线阵列转化为 BaTiO3 织构化薄膜，该工艺允许在涂有掺氟氧化锡（FTO）的图案化硅片上进行厚度可控的共形薄膜生长。此外，优化了处理参数以实现 100 pm/V 的高压电耦合系数。这种高压电响应以及共形生长的织构化 BaTiO3 薄膜的高相对介电常数（εr = 1600）表明它们在传感器、NVFeRAM 和 MEMS 中有潜在的应用。
