2D MoO3 synthesis and its application in electronic devices

Rahman, F 2018, 2D MoO3 synthesis and its application in electronic devices, Doctor of Philosophy (PhD), Engineering, RMIT University.

Document type: Thesis
Collection: Theses

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Title 2D MoO3 synthesis and its application in electronic devices
Author(s) Rahman, F
Year 2018
Abstract Two-dimensional (2D) materials have significant technological importance due to their exceptional electronic and mechanical properties, which stem from the quantum confinement of charge carriers along a single plane. Their thin atomic nature and large surface-to-volume ratio offer an opportunity to tailor their properties, making them suitable candidates for next-generation electronic devices.

Molybdenum trioxide (MoO3) is a wide bandgap and high dielectric material that can be obtained in 2D structure. The bandgap of the material can be readily tuned using ion intercalation method. Consequently, carrier mobility can be enhanced by increasing the charge carriers density near the Fermi level. As such, reliable production of few atoms thick 2D material is essential for translating their properties into electronic applications. However, obtaining the desired thickness of uniform 2D MoO3 crystal is challenging, as the existing exfoliation technique do not produce crystals of uniform thickness efficiently. A new chemical route has been developed to thin down bulk crystals of MoO3 in order to obtain them in 2D form. The viability and reliability of the etching process has been established via detail characterisation of the material pre- and post-etching. The electrical characterisation of the 2D MoO3 crystals based field effect transistors show high switching ratios.

Non-volatile resistive memory devices are theorised to be the most promising pathway towards analogue memory and neuromorphic computing. Metal oxides are widely used as channel material in such memory devices. High dielectric constant and thermal stability of MoO3 renders it ideal for resistive memory applications as high dielectric nature suppresses the undesirable parasitic effects during resistive switching performance. The reversible and non-volatile resistive switching behaviour of planar MoO3 crystals has been investigated. The room temperature memory retention shows high on/off ratio of >103 for 104 s duration and endurance of > 6,000 cycles, and low power consumption. This study demonstrates the viability of MoO3 as a resistive memory element and paves the way for future 2D resistive memory technologies.

Furthermore, conductometric gas sensors have been developed based on the 2D crystals of non-stoichiometric MoO3. Thermodynamically stable MoO3 shows excellent electron affinity towards various gaseous elements. In addition, 2D structure endows them with an ultrahigh surface area that contains an extremely large proportion of surface atoms. These surface atoms serve as active sites to effectively react with gas molecules for gas sensing applications. Detail characterisations of the sensors show excellent selectivity and high sensitivity towards toxic and health hazard gases such as, H2S and NO2. The cyclic repeatability shows a negligible variation in sensitivity that establishes the viability of a high responsive gas sensor based on 2D MoO3.

Hence, thermally stable and high dielectric 2D MoO3 has the potential to offer a new-generation of nano-electronic applications with excellent performance.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Engineering
Subjects Functional Materials
Microelectronics and Integrated Circuits
Keyword(s) 2D materials
resistive memory
chemical vapour deposition
chemical etching
nano electronics
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Created: Thu, 01 Aug 2019, 10:30:56 EST by Keely Chapman
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