Self-assembly and electrical characteristics of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles on SiO2/n-Si

• Main Authors: Baharuddin, A.A., Ang, B.C., Wong, Y.H.
• Format: Article
• Published: Elsevier 2017
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://eprints.um.edu.my/17541/; https://doi.org/10.1016/j.apsusc.2017.06.155

A novel investigation on a relationship between temperature-influential self-assembly (70–300 °C) of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles (NPs) on SiO2/n-Si with electrical properties was reported with the interests for metal-oxide-semiconductor applications. X-ray diffractometer (XRD) analysis conveyed that 8 ± 1 nm of the NPs were assembled. Increasing heating temperature induced growth of native oxide (SiO2). Raman analysis confirmed the coexistence of Fe3O4-γ-Fe2O3. Attenuated Total Reflectance Infrared (ATR-IR) spectra showed that self-assembly occurred via Si–O–C linkages. While Si–O–C linkages were broken down at elevated temperatures, formations of Si-OH defects were amplified; a consequence of physisorbed surfactants disintegration. Atomic force microscopy (AFM) showed that sample with more physisorbed surfactants exhibited the highest root-mean-square (RMS) roughness (18.12 ± 7.13 nm) whereas sample with lesser physisorbed surfactants displayed otherwise (12.99 ± 4.39 nm RMS roughness). Field Emission Scanning Electron Microscope (FE-SEM) analysis showed non-uniform aggregation of the NPs, deposited as film (12.6 μm thickness). The increased saturation magnetization (71.527 A m2/kg) and coercivity (929.942 A/m) acquired by vibrating sample magnetometer (VSM) of the sample heated at 300 °C verified the surfactants’ disintegration. Leakage current density-electric field (J-E) characteristics showed that sample heated at 150 °C with the most aggregated NPs as well as the most developed Si–O–C linkages demonstrated the highest breakdown field and barrier height at 2.58 × 10−3 MV/cm and 0.38 eV respectively. Whereas sample heated at 300 °C with the least Si–O–C linkages as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08 × 10−3 MV/cm and 0.19 eV respectively. This study opens up better understandings on how formation and breaking down of covalent linkages as well as accumulation of defects, particularly prior temperature influential self-assembly at the interfaces, affected electrical breakdown field and barrier height. Hence, possible future development of self-assembly silicon-based metal-oxide-semiconductor (MOS) structure particularly in the presence of SiO2 can be deliberated.