【作者】 谢建平；

【导师】 叶高翔；

【作者基本信息】 浙江大学 ， 凝聚态物理， 2009， 博士

【摘要】 自液相材料成功地被用作薄膜生长的基底以来,液相基底表面金属以及有机晶体薄膜在成膜机理、微观结构和物理特性等方面的研究已经引起了人们广泛的关注和重视。本论文采用热蒸发方法在液相(硅油)基底表面成功制备了非磁性(金Au、银Ag、铜Cu)和磁性(铁Fe)金属薄膜,系统研究了该自由支撑薄膜系统的成膜机理、微观结构、薄膜特征内应力和磁特性等,得到以下结果：(1)液相(硅油)基底表面磁性(Fe)和非磁性(Cu、Ag、Au)的金属薄膜的生长机理均近似服从二阶段生长模型：沉积原子在基底表面首先扩散、成核并凝聚成尺寸为微米量级的准圆形原子团簇；然后沉积原子和原子团簇继续经过无规扩散和旋转,逐渐凝聚成分枝状凝聚体,随着名义膜厚的增加,分枝状凝聚体不断生长和相互连接,最终形成致密的连续薄膜。在连续铜薄膜系统中,发现了准周期的带状有序结构。(2)液相(硅油)基底表面金属原子团簇和分枝状凝聚体存在边缘扩散现象,且随着基底温度的升高,扩散现象逐渐明显。实验结果显示,在银薄膜系统中,随着硅油基底温度升高,原子团簇和凝聚体不断向样品边缘定向扩散,样品中心区域的团簇或凝聚体的覆盖率比边缘的相应值小；对于一定的薄膜名义厚度,硅油基底温度越高,中心区域的凝聚体覆盖率越小。(3)原子力显微镜(AFM)表面分析结果显示：液相(硅油)基底表面金属原子团簇、分枝状凝聚体和连续薄膜均是由101纳米量级的原子颗粒所组成的,颗粒尺寸服从高斯分布。同一实验条件下,不同金属材料对应不同的颗粒尺寸分布。液相基底表面金属薄膜的上表面、下表面形貌和微观结构并不相同,并且依赖于薄膜名义厚度d的变化而变化。(4)利用磁力显微镜(MFM)首次观察了液相(硅油)基底表面磁性铁薄膜中的磁畴结构。铁原子分枝状凝聚体中没有观察到磁力信号；连续薄膜中的磁畴结构分布杂乱无规；磁畴尺寸和相图磁力信号均随薄膜厚度增加而增加；即当10.0nm≤d≤80.0nm时,记录磁力变化信号变化的振动相移Δθ从0.29°变化到0.81°,相对应的磁力梯度从1.4×10-3N／m变化到4.0x10-N／m。与此相比,沉积在玻璃基底上铁薄膜样品中,发现了明显的十字畴壁结构(Cross-tie wall).本文各章节内容安排如下：第一章：综述了固体和液体基底表面薄膜的制备方法、成膜机理、微观机构及其计算机模拟结果等；详细介绍了磁畴理论、观测磁畴的主要方法和磁性薄膜的研究现状；最后给出原子力显微镜和磁性显微镜的工作原理。第二章：系统研究了硅油基底表面铜薄膜的成膜机理、微观结构及连续铜薄膜中由于特征内应力释放而产生的带状有序结构的生长规律和形成机理。第三章：给出了银原子及其团簇在硅油基底表面的凝聚特性及其受温度的影响规律；利用原子力显微镜对金和银分枝状凝聚体以及金连续薄膜正反表面的微观结构进行了细致的研究。第四章：利用磁力显微镜观察和分析了液相(硅油)基底表面铁分枝状凝聚体和连续薄膜的磁畴结构,并与玻璃基底表面铁薄膜的磁畴结构进行了对比。第五章：研究结论与后续展望。这一部分梳理和总结了全文的主要观点和研究结论,并展望了未来有待进一步研究的问题。更多还原

【Abstract】 Since the fact that liquid materials can truly employed as thin film substrates was discovered in 1990’s, it has attracted increasing interest in studying the formation mechanism, microstructures and physical properties of the metallic and organic crystals thin films on the liquid substrates because of their different behaviors from that on solid surfaces.Nonmagnetic [Silver (Ag), Gold (Au), Copper (Cu)] and magnetic [Iron (Fe)] film systems, deposited on liquid (silicone oil) substrates by thermal evaporation method, have been fabricated successfully and the growth mechanism, microstructures, internal stress patterns as well as magnetic domains in the magnetic films are studied systematically in this dissertation. The major results are summarized as follows:(1) It is found that the growth mechanism of both the nonmagnetic and magnetic thin films on liquid surfaces approximately obey the two-stage growth model. The first stage involves nucleation and growth of atomic compact and ramified clusters; the subsequent stage includes random diffusion of the clusters and formation of the large ramified aggregates on the liquid surfaces. In the continuous copper films, band-shaped ordered patterns with macroscopical length scale and with quasi-periodic characteristics are observed.(2) An obvious edge diffusion phenomenon of the metallic atomic clusters and ramified aggregates is observed in our Ag film system. The experiment shows:the Ag atomic clusters and ramified aggregates diffuse toward the edge of the oil substrate during and after the deposition, therefore, the coverage of the Ag clusters in the central area of the sample is smaller than that on the sample edge. This phenomenon is more obvious with the increase of the substrate temperature; for a fixed film thickness, as the oil temperature increases, the coverage decreases.(3) Further study on the Cu, Ag and Au film systems by atomic force microscopy (AFM) are presented. It is found that the metallic atomic ramified aggregates and continuous films exhibit a granular structure. The size of the granularities exhibits the Gaussian distribution. The size distributions of the granularities in both the aggregates and films depend on the nature of the materials apparently. In the Au films system, we study the morphologies of the down surface and up surface of the film and it shows different morphologies and exhibit different structures.(4) Magnetic domain structures are newly observed in the continuous Fe films while no magnetic signal is detected in the Fe ramified aggregates. MFM studies for the Fe films (10.0 nm≤d≤80.0 nm) show that the domain wall structure is widespread and irregularly shaped and the oscillation phase shift△θ, which records as the magnetic force image, changes from 0.29°to 0.81°with the increase of the film thickness, corresponding to the magnetic force gradient from 1.4×10-3 to 4.0×10-3 N/m, respectively. Finally, we perform MFM measurement on Fe/glass samples and the cross-tie walls of various sizes confined in the Fe film system are observed experimentally.This dissertation is organized as following:In chapterⅠ, firstly, a brief introduction on the fabrication method, formation mechanism, as well as computer simulation of the thin film systems on solid and liquid substrates is given. And then, the magnetic domain theory and the observation methods for the magnetic domain structures are introduced. At last, the principle of the AFM and MFM are also presented.In chapterⅡ, the formation mechanism, microstructures and the band-shaped ordered patterns in the Cu film system on silicone oil surfaces are studied systematically.In chapterⅢ, the influences of the liquid substrate temperature on the formation mechanism of Ag clusters are studied. AFM studies on the microstructures of the Ag and Au ramified aggregates as well as the up and down surfaces of the Au continuous films are presented.In chapterⅣ, we research the characteristic microstructures and magnetic properties of the rough Fe film system deposited on silicone oil and glass surfaces.In chapterⅤ, main conclusions and prospect are presented.更多还原