Modifying Spin Injection Characteristics in the Co/Alq3 System by Using a Molecular Self-Assembled Monolayer

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• 作者：Hyuk-Jae Jang ; Jun-Sik Lee ; Sujitra J. Pookpanratana ; Christina A. Hacker ; Ich C. Tran ; Curt A. Richter
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：June 11, 2015
• 年：2015
• 卷：119
• 期：23
• 页码：12949-12955
• 全文大小：313K
• ISSN：1932-7455

文摘

We present the results of experiments that explore the influence of molecular self-assembled monolayers (SAMs) on characteristics of spin injection into an organic semiconductor, Alq₃ [tris(8-hydroxyquinoline)aluminum], from a ferromagnetic metal, Co. Two different SAMs, MHA (16-mercaptohexadeconic acid, HS(CH₂)₁₅CO₂H) and ODT (1-octadecanethiol, CH₃(CH₂)₁₇SH), are inserted between Alq₃ and Co layers, and their effects on electronic structure hybridization and related changes in energy levels and spin-dependent properties at the interface are investigated. X-ray photoelectron measurements of the surface structure for the MHA, ODT, and Alq₃ organic layers provide bonding and chemical conformational information. Ultraviolet photoelectron spectroscopy (UPS) measurements reveal that both MHA and ODT treatments lower the work function of Co. X-ray magnetic circular dichroism (XMCD) spectra imply that SAMs reduce the hybridization between Co and Alq₃, and furthermore, they enhance the spin magnetic moment of Co.