Research Project

Interested research area

  • Semiconductor (Si, GaAs) device fabrication and characterization
  • Graphene-based devices (transistor, sensor etc)
  • Graphene film growth and synthesis

Formation and Characterization of Molybdenum Disulfide/Reduced Graphene Oxide Heterostructure on Paper Substrate [On going]

Grant type: UTM GUP (Transdisciplinary Research Grant)

Duration: 2 years (Dec 2018 - Nov 2020)

In recent years, there are many efforts to demonstrate the formation of heterostructure made from 2D materials such as graphene and molybdenum disulfide (MoS2). The heterostructure is expected to be useful for for rectifier, photodetector and sensors. While these 2D materials are mainly prepared using expensive and complicated process like chemical vapor deposition, solution-phase process is regarded as a viable alternative that offers simplicity, low setup cost and large-scale production. In this work, a heterostucture consists of reduced graphene oxide (rGO) and MoS2 is fabricated using solution phase process, namely screen printing and spin coating, on paper substrate. The morphological and electrical properties of rGO and MoS2 thin films are characterized. Electrical characterization of the formed heterostructure is also analyzed in order to understand its operation. This information is important when designing electronic device using rGO/MoS2 heterostructure on flexible paper substrate. The finding from this project is expected to have significant contribution towards the realization of 2D material-based flexible electronics.

Reduced Graphene Oxide-based Schottky junction for Chamical Sensor application [Completed]

Grant type: FRGS

(Original title: Investigation of charge carrier modulation in aluminium gallium arsenide/gallium arsenide nanochannel array structure by graphene-wrap-gate)

Duration: 2014-2017

Graphene and its derivatives are promising materials for chemical sensors application. This research work started with motivation to develop a sensor that incorporates reduce graphene oxide (RGO) onto alluminium gallium arsenide (AlGaAs)/gallium arsenide (GaAs) channel. RGO/GaAs junction formed a Schottky junction which can control the current flow along GaAs channel. RGO's sensitive interaction with various types of adsorbates enables the modulation of AlGaAs/GaAs conductivity, thus open up the possibility for sensor operation.

In the early stage of the project, the fabrication of the RGO-gated GaAs transistor was demonstrated. However, difficulty in obtaining good ohmic contact for source and drain electrodes impeded the progress of the project. Device structure was revised to a simpler configuration called back-to-back Schottky diode (BBSD). Due to time constraint, the project scope of was limited to the development of Graphene oxide film The fabricated device fabrication process and the fundamental analysis on junction properties of the RGO/semiconductor Schottky junction. The device was fabricated through vacuum filtration of graphene oxide dispersion and reduction via ascorbic acid. Effect of process parameters to the properties of the formed RGO film was investigated. RGO film characterization was done using atomic force microscopy, optical microscope, fourpoint probe, Raman spectroscopy and surface profiler.

The fabricated RGO/GaAs BBSD showed nonlinear current-voltage (I-V) characteristics, confirming the formation of Schottky junction at the interface. The Schottky barrier was calculated to be around 0.8 eV. To validate the obtained result, analysis was performed to RGO/Silicon BBSD device. Temperature dependence I-V characteristics were measured to analyse the actual barrier height and its inhomogeneity. The average barrier height was found to be 1.2 eV with standard deviation of 0.15 eV. The relatively high barrier height value could be explained by the formation of thin insulator layer at interface possibly during the RGO film transfer process.

Information on the basic properties of the RGO/semiconductor junction is significance when designing the Schottky based sensor. Fabrication techniques utilized in this research works did not use sophisticated setup/equipment. Therefore, the fabrication procedure is favourable for low-cost chemical sensor.

Past projects:

  1. Graphene-based three-branch nanojunction device
  2. Fast and simple Graphene layer number identification using optical contrast method
  3. GaAs-based rectenna device
  4. GaAs-based three-branch nanojunction device