Majumdar Sayani, Grochowska Katarzyna, Sawczak Miroslaw, Śliwiński Gerard, Huhtinen Hannu, Dahl Johnny, Tuominen Marjukka, Laukkanen Pekka, Majumdar Himadri S
Department of Applied Physics, Aalto University School of Science , FI-00076 Aalto, Finland.
Photophysics Department, The Szewalski Institute, Polish Academy of Sciences , 80-231 Gdansk, Poland.
ACS Appl Mater Interfaces. 2015 Oct 14;7(40):22228-37. doi: 10.1021/acsami.5b04840. Epub 2015 Oct 1.
We report fabrication of a hybrid organic semiconductor-inorganic complex oxide interface of rubrene and La0.67Sr0.33MnO3 (LSMO) for spintronic devices using pulsed laser deposition (PLD) and investigate the interface structure and chemical bonding-dependent magnetic properties. Our results demonstrate that with proper control of growth parameters, thin films of organic semiconductor rubrene can be deposited without any damage to the molecular structure. Rubrene, a widely used organic semiconductor with high charge-carrier mobility and spin diffusion length, when grown as thin films on amorphous and crystalline substrates such as SiO2-glass, indium-tin oxide (ITO), and LSMO by PLD at room temperature and a laser fluence of 0.19 J/cm2, reveals amorphous structure. The Raman spectra verify the signatures of both Ag and Bg Raman active modes of rubrene molecules. X-ray reflectivity measurements indicate a well-defined interface formation between surface-treated LSMO and rubrene, whereas X-ray photoelectron spectra indicate the signature of hybridization of the electronic states at this interface. Magnetic measurements show that the ferromagnetic property of the rubrene-LSMO interface improves by >230% compared to the pristine LSMO surface due to this proposed hybridization. Intentional disruption of the direct contact between LSMO and rubrene by insertion of a dielectric AlOx layer results in an observably decreased ferromagnetism. These experimental results demonstrate that by controlling the interface formation between organic semiconductor and half-metallic oxide thin films, it is possible to engineer the interface spin polarization properties. Results also confirm that by using PLD for consecutive growth of different layers, contamination-free interfaces can be obtained, and this finding is significant for the well-controlled and reproducible design of spin-polarized interfaces for future hybrid spintronics devices.
我们报告了使用脉冲激光沉积（PLD）制备用于自旋电子器件的红荧烯与La0.67Sr0.33MnO3（LSMO）的有机半导体 - 无机复合氧化物混合界面，并研究了界面结构和化学键相关的磁性。我们的结果表明，通过适当控制生长参数，可以沉积有机半导体红荧烯薄膜而不会对分子结构造成任何损害。红荧烯是一种广泛使用的有机半导体，具有高电荷载流子迁移率和自旋扩散长度，当在室温下以0.19 J/cm2的激光能量密度通过PLD在诸如SiO2 - 玻璃、氧化铟锡（ITO）和LSMO等非晶和晶体衬底上生长为薄膜时，呈现非晶结构。拉曼光谱验证了红荧烯分子的Ag和Bg拉曼活性模式的特征。X射线反射率测量表明在表面处理的LSMO和红荧烯之间形成了明确的界面，而X射线光电子能谱表明该界面处电子态杂化的特征。磁性测量表明，由于这种提议的杂化作用，红荧烯 - LSMO界面的铁磁性能比原始LSMO表面提高了>230%。通过插入介电AlOx层有意破坏LSMO和红荧烯之间的直接接触会导致铁磁性明显降低。这些实验结果表明，通过控制有机半导体和半金属氧化物薄膜之间的界面形成，可以设计界面自旋极化特性。结果还证实，通过使用PLD连续生长不同层，可以获得无污染的界面，这一发现对于未来混合自旋电子器件的自旋极化界面的良好控制和可重复设计具有重要意义。
