Phase transformation behavior of ultrathin Hf0.5Zr0.5O2 films investigated through wide range annealing experiments
Phase transformation behavior of ultrathin Hf0.5Zr0.5O2 films investigated through wide range annealing experiments
复制标题
DOI：
10.7567/1347-4065/ab00f6
复制
发表时间：
2019-03
影响因子：
1.5
通讯作者：
S. Migita;H. Ota;K. Shibuya;H. Yamada;A. Sawa;T. Matsukawa;A. Toriumi
中科院分区：
文献类型：
--
作者：
S. Migita;H. Ota;K. Shibuya;H. Yamada;A. Sawa;T. Matsukawa;A. Toriumi
Hf0.5Zr0.5O2 薄膜并不总是铁电性的。这项工作研究了退火温度和时间对 10 nm 厚 Hf0.5Zr0.5O2 薄膜晶体结构和介电性能的影响。研究发现，随着退火温度和时间的变化，非晶膜首先形成四方相晶体，然后转变为斜方晶系和单斜晶相。薄膜中的斜方相的体积分数被称为铁电性的起源，在一定的退火条件范围内变得占主导地位。因此，退火温度和时间决定了Hf0.5Zr0.5O2薄膜的反铁电、铁电和顺电特性。从伴随晶胞体积变化的各晶相的形成能的角度讨论该相变行为。四方晶系到斜方晶系以及斜方晶系到单斜晶系之间转变速率的竞争是铁电薄膜形成的关键。
Hf0.5Zr0.5O2 thin films are not always ferroelectric. This work investigates the impact of annealing temperature and time on the crystalline structures and dielectric properties of 10 nm thick Hf0.5Zr0.5O2 thin films. It is found that the tetragonal phase crystal is formed from the amorphous film firstly, then transforms to the orthorhombic and monoclinic phases, in accordance with the annealing temperature and time. The volume fraction of the orthorhombic phase in the film, which is known as the origin of ferroelectricity, becomes dominant in a certain range of the annealing condition. Thus, the annealing temperature and time are responsible for the anti-ferroelectric, ferroelectric, and paraelectric characteristics of Hf0.5Zr0.5O2 thin films. This phase transformation behavior is discussed from the viewpoint of formation energies of the respective crystal phases, which accompanies the changes of unit cell volumes. The competition of transformation rates between the tetragonal to orthorhombic and the orthorhombic to monoclinic is key for the formation of ferroelectric films.