Multiferroic materials have attracted significant attention due to their potential to revolutionize logic and memory devices by reducing energy consumption or increasing information density. Barium monoferrite (γ-BaFeO or BaFeO) is a promising lead- and bismuth-free multiferroic material with a stuffed tridymite-like structure, exhibiting both ferroelectricity and antiferromagnetism at room temperature. BaFeO thin films with engineered grain orientation, composition, elastic strain, and magnetic interlayer couplings could open new avenues for novel devices. However, synthesizing the stoichiometric "1–2–4" phase in the BaO-FeO system remains a challenge. This study focuses on the deposition of pure and crystalline γ-BaFeO thin films using the Pulsed Electron Deposition (PED) method. An analysis of the plasma plume revealed that two main mechanisms govern the dynamics of BaFeO deposition: a congruent ablation process occurring far from thermodynamic equilibrium and an incongruent low-energy evaporation process. The regions of the film with maximized ablative/evaporative ratios are free from the secondary BaFeO phase, suggesting that the thermal evaporative contribution is the primary factor responsible for the out-of-stoichiometry composition. The influence of the substrate type on the structural properties of BaFeO films was also evaluated. It was confirmed that (h00)-oriented BaFeO tends to grow on amorphous quartz and polycrystalline Pt-coated quartz in the 700–800°C temperature range. Conversely, the growth on SiO/Si leads to the preferential grain orientation along the (0k0) and (0kl) directions by increasing the temperature. These findings demonstrate the potential of PED for producing high-quality γ-BaFeO polycrystalline thin films. A fully heteroepitaxial (h00)-BaFeO/(111)-MgO system was even achieved by depositing on a single-crystal MgO substrate. This unprecedented result paves the way for utilizing such thin films in multiferroic applications, where phase purity, structural orientation, and defect-free structures can be exploited to enhance the magnetoelectric properties of the device.

中文翻译：

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脉冲电子沉积技术生长多铁性 γ-BaFe2O4 薄膜

多铁性材料因其通过降低能耗或增加信息密度而彻底改变逻辑和存储设备的潜力而引起了广泛关注。单铁酸钡（γ-BaFeO或BaFeO）是一种有前途的无铅和铋多铁材料，具有填充鳞石英结构，在室温下表现出铁电性和反铁磁性。具有工程晶粒取向、成分、弹性应变和磁性层间耦合的 BaFeO 薄膜可以为新型器件开辟新途径。然而，在 BaO-FeO 体系中合成化学计量的“1-2-4”相仍然是一个挑战。本研究重点是使用脉冲电子沉积 (PED) 方法沉积纯晶体 γ-BaFeO 薄膜。对等离子体羽流的分析表明，有两种主要机制控制 BaFeO 沉积的动力学：远离热力学平衡发生的一致烧蚀过程和不一致的低能蒸发过程。具有最大烧蚀/蒸发比的薄膜区域不含二次 BaFeO 相，这表明热蒸发贡献是造成化学计量成分外的主要因素。还评估了基底类型对 BaFeO 薄膜结构性能的影响。已证实，在 700-800°C 的温度范围内，(h00) 取向的 BaFeO 倾向于在非晶石英和多晶 Pt 涂层石英上生长。相反，通过升高温度，SiO/Si 上的生长导致沿 (0k0) 和 (0kl) 方向的择优晶粒取向。这些发现证明了 PED 生产高质量 γ-BaFeO 多晶薄膜的潜力。完全异质外延的 (h00)-BaFeO/(111)-MgO 系统甚至可以通过在单晶 MgO 基底上沉积来实现。这一前所未有的结果为在多铁性应用中使用此类薄膜铺平了道路，其中可以利用相纯度、结构取向和无缺陷结构来增强器件的磁电性能。