Role of surface roughness in governing the mechanical, electrical, magnetic, and optical properties of amorphous Co40Fe40Gd20 thin films on flexible substrates

IF 5.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics Pub Date : 2026-02-01 Epub Date: 2025-12-06 DOI:10.1016/j.intermet.2025.109090

Shih-Hung Lin , Yung-Huang Chang , Yuan-Tsung Chen , Xuan-Ming Su , Wen Chang , Huang-Wei Chang

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Abstract

Amorphous cobalt-iron-gadolinium (Co₄₀Fe₄₀Gd₂₀) thin films with thicknesses of 10 nm–50 nm were deposited on flexible polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) substrates via direct-current (DC) magnetron sputtering and annealed at 40 °C and 80 °C to investigate the effects of film thickness, annealing temperature, and substrate type on structural, mechanical, electrical, magnetic, and optical properties. X-ray diffraction (XRD) confirmed the films remained amorphous under all conditions, due to the high gadolinium (Gd) content and limited thermal energy below the polymer glass transition temperatures. Atomic force microscopy (AFM) revealed substrate-dependent surface evolution, with PET films showing a decrease in roughness from 5.91 nm to 4.79 nm after 80 °C annealing, whereas PMMA films exhibited minimal roughness change. Surface energy increased with film thickness but decreased slightly upon annealing due to atomic rearrangement. Mechanical properties improved with both thickness and annealing. PET films reached a maximum Young's modulus of 22.58 GPa and hardness of 4.75 Gpa at 50 nm after 80 °C annealing, while PMMA films achieved 15.05 GPa modulus at 50 nm after 40 °C. Electrical measurements showed a significant reduction in sheet resistance from 7261 Ω/sq for as-deposited 10 nm films to 144 Ω/sq for 50 nm films annealed at 80 °C, with enhanced carrier mobility and concentration. Magnetic analysis confirmed in-plane soft magnetic behavior, with minor variations in coercivity (H_c) and saturation magnetization (M_s) influenced by stress relaxation and morphology-induced anisotropy. Magnetic force microscopy (MFM) indicated moderate annealing promoted ordered stripe domains, while higher temperatures induced domain coarsening. Optical characterization revealed transmittance decreased with thickness, reaching 40.68 % and 47.15 % at 10 nm on PET and PMMA at annealing 40 °C, whereas absorbance increased, indicating thickness-dominated optical behavior. These findings demonstrate that controlled annealing and thickness optimization enable precise tuning of surface roughness and multifunctional properties of CoFeGd amorphous films on flexible substrates, supporting their design for advanced flexible spintronic, electronic, and optoelectronic devices.

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柔性基板上非晶Co40Fe40Gd20薄膜的机械、电学、磁学和光学性能受表面粗糙度的影响

采用直流（DC）磁控溅射技术在柔性聚对苯二甲酸乙二醇酯（PET）和聚甲基丙烯酸甲酯（PMMA）衬底上沉积了厚度为10 nm - 50 nm的非晶钴铁钆（Co40Fe40Gd20）薄膜，并在40℃和80℃下退火，研究了薄膜厚度、退火温度和衬底类型对结构、机械、电学、磁学和光学性能的影响。x射线衍射（XRD）证实，由于钆（Gd）含量高，且低于聚合物玻璃化转变温度的热能有限，薄膜在所有条件下都保持无定形。原子力显微镜（AFM）显示，PET薄膜在80°C退火后，表面粗糙度从5.91 nm下降到4.79 nm，而PMMA薄膜的粗糙度变化很小。表面能随薄膜厚度的增加而增加，但退火后由于原子重排而略有下降。随着厚度和退火的增加，力学性能得到改善。PET薄膜经80℃退火后在50 nm处的最大杨氏模量为22.58 GPa，硬度为4.75 GPa， PMMA薄膜经40℃退火后在50 nm处的最大模量为15.05 GPa。电测量表明，在80°C退火的50 nm薄膜中，薄膜电阻从7261 Ω/sq显著降低到144 Ω/sq，载流子迁移率和浓度增强。磁性分析证实了面内软磁行为，矫顽力（Hc）和饱和磁化强度（Ms）受应力松弛和形态诱导的各向异性影响较小。磁力显微镜（MFM）显示，适度退火促进了有序条纹畴的形成，而高温则导致了条纹畴的粗化。光学特性表明，透射率随厚度的增加而降低，在PET和PMMA上，在40℃退火时，透射率在10 nm处分别达到40.68%和47.15%，而吸光度则增加，表明厚度主导光学行为。这些发现表明，控制退火和厚度优化可以精确调整柔性衬底上CoFeGd非晶膜的表面粗糙度和多功能特性，支持其设计先进的柔性自旋电子，电子和光电子器件。

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来源期刊

Intermetallics 工程技术-材料科学：综合

CiteScore

7.80

自引率

9.10%

发文量

291

审稿时长

37 days

期刊介绍： This journal is a platform for publishing innovative research and overviews for advancing our understanding of the structure, property, and functionality of complex metallic alloys, including intermetallics, metallic glasses, and high entropy alloys. The journal reports the science and engineering of metallic materials in the following aspects: Theories and experiments which address the relationship between property and structure in all length scales. Physical modeling and numerical simulations which provide a comprehensive understanding of experimental observations. Stimulated methodologies to characterize the structure and chemistry of materials that correlate the properties. Technological applications resulting from the understanding of property-structure relationship in materials. Novel and cutting-edge results warranting rapid communication. The journal also publishes special issues on selected topics and overviews by invitation only.