Browsing by Author "Jaafar, Muhammad Musoddiq"

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Electrical bistabilities behaviour of all-solution-processed non-volatile memories based on graphene quantum dots embedded in graphene oxide layers
(2019-09-01)
Jaafar, Muhammad Musoddiq
;
Ooi, Poh Choon
;
Wee, M. F. Mohd. Razip
;
Haniff, Muhammad Aniq Shazni Mohammad
;
Mohamed, Mohd Ambri
This study demonstrates the feasibility of all-solution-processed mean to fabricate carbon-based non-volatile memory (NVM). The NVM devices were fabricated on polyethylene terephthalate (PET) substrate using spin-coating and spray-coating techniques in the structure of silver nanowires (AgNWs)/graphene oxide (GO)/graphene quantum dots (GQDs)/graphene oxide (GO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/PET. PEDOT:PSS was used as the bottom conductive layer and deposited by spin-coating method. GQDs were used as a charge trapping site in the structure and embedded in the two GO insulator layers. The AgNW metal electrode was formed on top of GO/GQDs/GO/PEDOT:PSS by the spray-coating method. The overall smooth surface morphology of the spray-coated films serves as good contact with the top metal electrode. The electrical characterization of the fabricated device shows the bistable current states with the ON/OFF ratio of 10(5). The NVM device can be programmed and erased multiple times. Various conduction mechanisms were proposed to describe the charge trapping process in GQD based on the obtained current-voltage measurement.
High-frequency Sezawa guided mode of GaN/sapphire using high aspect ratio electrode
(2019-11-01)
Jaafar, Muhammad Musoddiq
;
Wee, M. F. Mohd Razip
;
Dee, Chang Fu
;
Faiz, Mohd Syafiq
;
Chang, Edward Yi
The propagation of surface acoustic wave (SAW) on the piezoelectric substrate requires conventionally an interdigitated electrode structure to excite the mechanical displacement at resonance frequency. The control of the electrode thickness could be useful to manipulate the energy confinement and the band dispersion of the surface guided mode. It has been demonstrated recently that high aspect ratio (HAR) electrode could produce a dispersive shear horizontal and vertically polarized surface modes in the bulk piezoelectric substrate. In this theoretical study, we propose to employ a high aspect ratio electrode on top of the GaN/sapphire-layered substrate enabling the presence of Sezawa surface mode. Based from the dispersion band, we obtained a higher frequency of surface guided mode in the non-radiative zone in the GaN/sapphire heterostructure configuration compared to the bulk GaN substrate. Indeed, these guided modes are induced by the hybridization between Sezawa surface mode and the mechanical resonance of the HAR electrode producing nearly a flat band at the limit of First Brillouin Zone. Furthermore, the displacement of each guided modes indicates the confinement of energy mostly in the electrode with a slight amount of energy in the top layer of the substrate. We demonstrated also the frequency tuning of guided mode using diverse materials for the electrode but also the thickness of GaN layer. The obtained results could be useful for the development of high-frequency telecommunication and sensing device based on Sezawa surface acoustic wave.