Synthesis and properties of two-dimensional ferrocene
Creators: name: LI, Zhipeng
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400909
subject: Photonic and electro-optical devices, sensors and systems (excl. communications)
classificationCode: 401605
subject: Functional materials

description: In last decade, two-dimensional (2D) material has been hailed as the most promising candidate in the development of high-performance electrical and magneto-electronic devices. Recently, numerous types of purpose novel 2D devices based on graphene-like structure such as transition metal dichalcogenide (TMDC) has been created to achieve high-tech transporting and signal processing devices. The reported benefits include high-efficiency, non-volatility and fast data processing speed.

The key reason of involving of 2D material is the surface effect, small-size effect and macroscopic quantum tunneling effect that triggered when materials are reduced to nano-scaled size. Applying of high-qualified 2D layer become a way to improve device performance of devices or systems. Likewise, importing high-range of performance modulation can also be achieved by simply modify the 2D surface.

To date, plenty of method has been applied for obtaining organic or metallic 2D structure including hexagonal boron nitride, black phosphorus, CrI3, Mxene and TMO. While there is complying need of effort to investigate novel method for achieving novel 2D material. Apart from that, 2D magnetism would also attract substantial attention from researchers who indicate new possibilities to produce novel spin logic devices with potentially non-volatility, low power consumption and fast data processing speed. high-qualified 2D materials are considered potential alternatives achieving high-efficient spin transport and receiving significant enhancement and multiple tunability under external magnetic field.

In order to enhance optoelectrical and magneto-electrical application, three primary areas of interest are to be investigated. Firstly, it is urgently needed to find more alternatives of new 2D materials allowing for realization and enhancement of properties. For instance, new 2D materials that combines molecular electronics, organic spintronics, and molecular magnetism are to be put into consideration. The second one is the finding of efficient and cheap method to obtained high qualified 2D materials or their heterostructure which is practically useful as basis of research to achieve high performance. Thirdly, it is remained to be determined how devices performance varies with as-grown materials when considering optoelectronic, magneto-electrical, spintronic and optical properties. 

This thesis explores optimized synthesis of novel finding of 2D organometallic compound ferrocene (FeCP2) made by Liquid interface penetration method (LIP). Those two methods above would be introduced and described to determine the improvement and contribution. Further, characterization and analysis via multiple facilities has been done to support the promised behaviors and design of proposed function.

As the one of most significant findings of this thesis, a newly found 2D organic metallocene semiconductor will be demonstrated at the first stage. Their bulk counterpart has been theoretically proved with attractive magnetic transport properties and simulation has shown that 2D ferrocene molecular layer possesses high spin-dependent characteristics. In our research, we successfully synthesis new 2D layered FeCP2 with drop casting of mixture prepared by LIP method. 

In the second stage of the thesis, multiple characterization methods are applied to those as-grown 2D materials to obtain their morphological, structural and basic optical behavior knowledge. Optical imaging, Raman, photoluminescence mapping and atomic force microscopy (AFM) were obtained to prove that it is atomically thin lateral material. Furthermore, high resolution transition electron microscope (HRTEM) is also applied to show Z-contrast image and atomic-resolution diffraction pattern.
Meanwhile, 2D layered FeCP2 is also synthesized and fabricated for spin-sensitive test. CAVIC optical transmittance test indicates its possible energy structure and Bader charge analysis shows that there is noticeable charge transfer under external electric field. Upward field tends to remove electrons from the molecule, and downward field tends to inject electrons into the molecule from the substrate. Therefore, we find that 2D FeCP2 contains extraordinary magnetoresistance.

Moreover, the optical anisotropy and birefringence have been measurement. Transmittance measurement was taken with polarized light and therefore we obtain cross-polarized light image. By two-frame calculation, we transfer the cross-polarized image to optical retardance and then get the relatively high birefringence results compared with many traditional and currently discovered nanoflake of birefringent material

Finally, we make final discussion about this thesis and make summary of the works. Also, we make some assumption about the future work of ferrocene research, such as chirality test, spintronic exam, optical anisotropy and birefringence.