Bagchi Sharmistha, Lalla N P
UGC-DAE Consortium for Scientific Research, University Campus, Khandwa road, Indore-452001, India.
J Phys Condens Matter. 2008 Jun 11;20(23):235202. doi: 10.1088/0953-8984/20/23/235202. Epub 2008 Apr 30.
The present study reports the cross-sectional transmission electron microscopic investigations of swift heavy ion-irradiation induced nano-size recrystallization of Ni in a nearly immiscible W/Ni multilayer structure. Multilayer structures (MLS) of W(25 Å)/Ni(25 Å) were grown on Si-(100) substrate by the ion-beam sputtering technique. The as-synthesized MLS were subjected to 120 MeV-Au(9+) ion-irradiation to a fluence of ∼5 × 10(13) ions cm(-2). Wide-angle x-ray diffraction studies of pristine as well as irradiated W/Ni multilayers show deterioration of the superlattice structure, whereas x-ray reflectivity (XRR) measurement reveals a nearly unaffected microstructure after irradiation. Analysis of the XRR data using 'Parratt's formalism' does show a significant increase of W/Ni interface roughness. Cross-sectional transmission electron microscopy (TEM) studies carried out in diffraction and imaging modes (including bright-field and dark-field imaging), show that at high irradiation dose the intralayer microstructure of Ni becomes nano-crystalline (1-2 nm). During these irradiation induced changes of the intralayer microstructure, the interlayer definition of the W and Ni layers still remains intact. The observed nano-recrystallization of Ni has been attributed to competition between low miscibility of the W/Ni interface and the ion-beam induced mixing kinetics.
本研究报告了在几乎不互溶的W/Ni多层结构中，快重离子辐照诱导Ni发生纳米尺寸再结晶的横截面透射电子显微镜研究。通过离子束溅射技术在Si-(100)衬底上生长W(25 Å)/Ni(25 Å)多层结构。将合成后的多层结构用120 MeV-Au(9+)离子辐照，注量约为5×10¹³ 离子/cm²。对原始以及辐照后的W/Ni多层结构进行的广角x射线衍射研究表明超晶格结构恶化，而x射线反射率(XRR)测量显示辐照后微观结构几乎未受影响。使用“帕拉特形式”对XRR数据进行分析确实显示W/Ni界面粗糙度显著增加。在衍射和成像模式(包括明场和暗场成像)下进行的横截面透射电子显微镜(TEM)研究表明，在高辐照剂量下，Ni的层内微观结构变成纳米晶(1 - 2 nm)。在这些辐照诱导的层内微观结构变化过程中，W层和Ni层的层间清晰度仍然保持完整。观察到的Ni的纳米再结晶归因于W/Ni界面的低互溶性与离子束诱导的混合动力学之间的竞争。
