铁酸铋薄膜退火工艺研究进展

Research Progress of Annealing Process of Bismuth Ferrite Thin Films

铁酸铋(BFO)多铁性材料因具有丰富的物理性能,以及其在存储器、传感器、电容器、光伏器件等方面的广阔应用前景,在过去几十年一直受到广泛的关注。然而,由于Bi元素在高温下容易挥发,所以很难合成纯相的BFO薄膜。此外,因存在氧空位或由于Fe离子变价导致的非化学计量比等缺陷,使其漏电流密度较大,严重影响BFO薄膜的铁电性能及实际应用。退火工艺是影响材料微结构及宏观性能的重要因素,因此通过退火工艺来调控BFO薄膜的结构及性能是一种十分有效的手段。然而,退火工艺包括退火时间、退火气氛、退火温度以及退火方式等多种形式,究竟每一种退火形式如何影响BFO薄膜的结构及性能是值得探讨的问题。为此,综述了退火工艺(括退火时间、退火气氛、退火温度以及退火方式)对BFO薄膜的结构(晶粒尺寸、形状,电畴尺寸、类型,表面形貌)和性能(磁性、铁电性、介电性、漏电性、导电机制)的影响的研究进展,并提出了一些亟待解决的问题。

Bismuth ferrite （BFO） multiferroic material has attracted great attention in the past decades due to their profound physical properties and broad application prospects in the fields of memory, sensors, capacitors and photovoltaic device. However, it is very difficult to prepare pure-phase BFO thin films because of the volatilization of Bi element at high temperatures. In addition, the ferroelectric properties and the practical application of BFO thin films are severely restrained owing to the high leakage current density as a result of the possible defects, such as oxygen vacancies and the non-stoichiometry caused by the variable valency of ferric ions. It was well known that the annealing process was a very important factor that could affect the mi-crostructure and macro-properties of materials; therefore, it was a very effective method to control the structure and properties of BFO films through annealing process. Nevertheless, annealing process included various forms, such as annealing time, annealing atmosphere, annealing temperature and annealing mode. Thus, it was worthy to discuss how each annealing form influenced the structure and properties of BFO thin films. For this reason, the research progress of annealing process （including annealing time, annealing atmosphere, annealing temperature and annealing mode） on the structures （grain size, shape, electric domain size, domain type and surface topography） and properties （magnetic and ferroelectric properties, dielectric and leakage properties, conductive mechanism） of bismuth ferrite thin films is reviewed, and some imperative problems to be solved are proposed.