Mohd Asyadi Azam Mohd Abid

Electrical characterization of reduced graphene oxide deposited on interdigitated electrodes

Nowadays, reduced graphene oxide (rGO) has been used in many applications because the surface defect density can be controlled compared to pristine graphene. It has a band gap which make it easier to integrate with existing technologies. Though, a simple process and large scale device fabrication is needed to align the rGO during fabrication of device. In this work, dielectrophoresis (DEP) technique has been used to align the rGO on a substrate with interdigitated electrodes. First, the rGO was drop-casted on sample with interdigitated electrodes. Followed by DEP process to align the deposited rGO. Electrical measurement has been done. It shows that the conductivity and current increases with the increased number of drops for rGO solution. SEM image shows a distribution pattern which forms percolation network pathway of rGO. Raman spectroscopy confirmed the presence of rGO in between the channel of electrodes. This simple technique has the potential to be used for future large scale device fabrication.

Structural analysis of graphene growth on interdigital electrodes micro supercapacitor by PECVD at various temperatures

Planar interdigital micro supercapacitor with the graphene growth via Plasma Enhanced Chemical Vapor Deposition (PECVD) with the different temperatures has been investigated in this works. The structure of the micro supercapacitor consists of SiO2 substrate, graphene growth on Nickel (Ni) electrodes coated with Polypyrrole (Ppy) and Polyvinyl Alcohol (PVA) layers as solid state electrolyte. A single layer of graphene which has sp2 hybridized carbon atoms is one of the promising material that has been used for micro supercapacitor electrodes due to several advantages such as high specific surface area, high thermal conductivity and high electron mobility. PECVD method is a main method for graphene growth due to the advantages such as high growth selectivity and good control in nanostructure patterning. In this works, the graphene growth on the interdigital electrodes was investigated in various temperatures from 400°C to 1000°C. The graphene growth structure on the interdigital electrodes of micro supercapacitor was characterized by Raman Spectroscopy. Raman Spectroscopy was carried out using a 532 nm laser excitation. A Raman spectrum of graphene was observed on interdigital electrode have identified three peaks which is D band, G band and 2D band. Raman spectra show that the intensity ratio of the 2D band and G band at 1000°C of 0.43 indicating a good quality of multilayer graphene growth.

A Study on (K, Na) NbO3 Thin Films with Optimized Layer: Effect on Physical and Electrical Properties

(K, Na)NbO3 (KNN) thin films were prepared by sol-gel technique. Spin coating deposition and rapid thermal annealing (RTP) process were applied to produce the KNN thin films. The films obtained demonstrated that highly crystallographic orientation was produced at five layer deposition with increase (preferred orientation) peak at (1 1 1). The thickness of five layers thin films observed by field emission scanning electron microscopy (FE-SEM) was determined to be ~200nm. However, the inhomogeneous distribution of KNN particles was detected in KNN thin films. The distribution of KNN elements was confirmed by energy-dispersive X-ray (EDX) spectra. Improvement was observed in resistivity (2.71-7.81x106 Ω.cm) and dielectric loss (0.35%-0.21%) following the increasing number of layers.

Facile Surface Modification of Graphene Nanoplatelets (GNPs) Using Covalent ATPS-Dehydration (GNPs-ATPS) and Non-Covalent Polyetherimide Adsorption (GNPs-PEI) Method

Graphene nanoplatelets (GNPs), a newly discovered nanomaterial, promise a great potential in many technological applications. However, the direct usage of GNPs was limited due to several surface property factors that require innovative modifications and treatments. In this study, the GNPs surface treatment is carried out by using a covalent and non-covalent approach. The success of the treatment was determined and evaluated through the Raman and FTIR spectroscopy analysis, FESEM, TEM and XRD morphological observation. A strong vibration of Raman peak at 2081.11 cm-1 represent a possible covalent bonding of C=C due to the ATPS-silane treatment, while the characteristic peak at 1013.82 cm-1 indicates the aromatic ring nature of polyimide that non-covalently associated with C-H and C-C, as well as C-O-C linkage from the polyether. From the IR spectroscopy, the covalent treatment on GNPs was occurred through the dehydration mechanism while hydrogen bonding in the multiple structures of –OH that associated to the carboxylic acids was obviously involved for non-covalent treatment of GNPs. TEM observation of GNPs-PEI (polyetherimide) revealed a unique phenomenon of a polymeric adsorption as represented by a nanosize gray dot morphology in between of the GNPs platelets. In overall, the facile procedure of the surface treatment that was applied in this study is reliable to yield a different type of GNPs characteristic of covalent and non-covalent surface active, which may open up broad possibilities for various cutting edges applications.