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Novel Nanoscale Electronic Devices For Metrology.

Rajkumar, RavishKrishnan. (2015) Novel Nanoscale Electronic Devices For Metrology. Doctoral thesis, University of Surrey (United Kingdom)..

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Recent advancements in novel materials has opened many interesting science applications which have led to new technologies. Graphene is one such material, with its extraordinary electronic, optical and mechanical properties, has gained much attention from industry as well as academia. Graphene science is still in its infant stage and has not revealed its full potential to reach the consumer industry yet. One of the most significant challenges remaining is developing understanding of the properties of graphene, its derivatives and other emerging 2D materials. The need to examine properties on different length scales and establishing the correlation between the structure, physical characteristics and the material performance is a key necessity. Due to the low dimensionality, new measurement platforms and advancements in the state-of-the-art metrology are required to study the property of these materials. In this work we have developed a prototype metrological tool based on a scanning platform which is ideal for the study of fundamental properties of materials like graphene at the nano- to micro-scale. A functionalised scanning probe microscope based on tuning fork (TF) force sensors has been designed and developed which performs a complete ‘dark’ measurement of the surface and electronic properties of the graphene. The hardware and software for the operation of the microscope has been designed, manufactured and tested. An innovative approach to attaching probes onto the tuning fork using Focused Ion Beam has been developed. The method has enabled us to achieve substantially higher Q-factor for the TF than the conventional methods discussed in the literature. Functional modes such as electrostatic force microscopy and magnetic force microscopy has been developed and experiments were conducted on epitaxial graphene on SiC substrate for determining the work function of the single layer graphene. In the second half of the thesis, we have used the tuning fork microscope system to calibrate the room temperature response of epitaxial graphene based Hall devices. Magnetic scanning gate microscopy has been employed to investigate the position-dependent sensitivity of the graphene Hall bar and the independent contribution of local electric and magnetic fields while varying the bias current direction, the orientation of the tip magnetization and bias potential of the tip. We demonstrate that the strong signal with the two-fold symmetry observed at the device comers has an electrostatic origin, whereas the response in the middle of the cross is mainly determined by the magnetic field. We have complimented the scanning gate microscopy (SGM) study with electrostatic force spectroscopy and Kelvin probe force microscopy (KPFM) measurements and have proposed an innovative combination of SGM-KPFM for optimizing the performance of Hall devices for specific industrial applications such as bead detection. Finally, using the technique we have provided solution to a long-standing problem of calibrating the stray fields produced from a magnetic probe. This opens up a route towards quantitative magnetic measurements using magnetic force microscopy.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Rajkumar, RavishKrishnan.
Date : 2015
Additional Information : Thesis (Eng.D.)--University of Surrey (United Kingdom), 2015.
Depositing User : EPrints Services
Date Deposited : 06 May 2020 14:37
Last Modified : 06 May 2020 14:45

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