Browsing by Author "Salleh, Muhamad Mat"

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A rapid responding ultraviolet sensor based on multi-parallel aligned ZnO nanowires field effect transistor
(2017-06-15)
Tiong, Teck-Yaw
;
Dee, Chang-Fu
;
Hamzah, Azrul Azlan
;
Goh, Boon Tong
;
Wong, Yuan-Yee
One-dimensional zinc oxide nanowires (ZnO NWs) have been reported to be suitable for UV sensing, but their applications are limited due to restricted surface area which restrains the performance especially in term of response and recovery. In this paper, we fabricate a UV sensor using multi-parallel aligned ZnO NWs based FET in order to overcome the mentioned drawbacks. The sensing characteristics of multi parallel aligned ZnO NWs based FET toward 0.44 mW/cm(2) UV illumination has been examined under depletion and enhancement modes, at ambient conditions. The fabricated UV sensor was found to possess the ability to differentiate UV with different intensity, improved sensitivity (in depletion mode), short response and recovery time (< 1 s), and with high stability. Our paper reports a simple and effective approach for UV sensor fabrication with high responsivity, sensitivity and reproducibility. (C) 2017 Elsevier B.V. All rights reserved.
Formation of a Multi-Arm Branched Nanorod of ZnO on the Si Surface via a Nanoseed-Induced Polytypic Crystal Growth Using the Hydrothermal Method
(2013-07-01)
Tan, Sin Tee
;
Umar, Akrajas Ali
;
Yahaya, Muhammad
;
Salleh, Muhamad Mat
;
Yap, Chi Chin
A branched nanorod of ZnO composed of multiple branches that projects from a single nanorod backbone can be realized by using a hydrothermal approach in the presence of a nanoseed with a special structure, namely multi-faceted orthorhombic Zn2SiO4. Orthorhombic Zn2SiO4 was prepared by annealing the ZnO nanoseed of size ca. 15 nnn on a Si substrate at a temperature of 900 degrees C in air for one hour. A typical branched nanorod was constructed by a hexagonal-and rectangular-shaped nanorod arm. HRTEM analysis on the branched structure indicated that the branches exhibited a different crystal growth direction [002] and [100], reflecting the presence of a polytypic growth process in the formation of the branched nanorod structure. The branched nanorod of ZnO and its feature-rich faceted property appears promising for solar cell, catalytic and sensing applications.
Porous (001)-faceted Zn-doped anatase TiO2 nanowalls and their heterogeneous photocatalytic characterization
(2014-01-01)
Saad, Siti Khatijah Md
;
Umar, Akrajas Ali
;
Hong Quan Nguyen
;
Dee, Chang Fu
;
Salleh, Muhamad Mat
The synthesis of a poriferous and high energy (001) faceted anatase Zn-doped TiO2 nanowall (ZnTNW), vertically grown on an indium tin oxide substrate, is presented. The ZnTNW was prepared using a modified liquid phase deposition method using zinc nitrate (Zn(NO3)(2)center dot xH(2)O) as a fluoride scavenger in the presence of hexamethylenetetramine. In a typical procedure, the ZnTNW nanowall with length and thickness of approximately 2 mu m and 60 nm, respectively, can be obtained from the reaction during a 5 h growth process. X-ray diffraction analysis shows that the nanowall has an anatase structure with a dominant high energy (001) basal plane. Meanwhile, the X-ray energy dispersive analysis confirms the presence of Zn in the TiO2 nanowall. High resolution transmission electron microscopy analysis results reveal, surprisingly, that the ZnTNW is single crystalline in nature although it has a highly porous (surface and bulk) structure. Photocatalytic properties of the ZnTNW were examined in the degradation of methylene blue. It was found that the ZnTNW exhibits excellent photocatalytic efficiency with kinetic reaction rate, turnover number and turnover frequency as high as 0.004 min(-1), 760 and 11 min(-1), respectively. The photocatalytic performance of the ZnTW was found to be higher for about 10% and 50% than the pristine TiO2 nanowalls and (001) faceted poriferous TiO2 microtablet, which reflected the effective effect of the Zn doping. The ZnTNW may find potentially use in photocatalytic heterogeneous applications.
Reliability study of high-k La2O3/HfO2 and HfO2/La2O3 stacking layers on n-In0.53Ga0.47As metal-oxide-semiconductor capacitor
(2016-02)
Chu, Chung-Ming
;
Lin, Yueh-Chin
;
Lee, Wei-I
;
Dee, Chang Fu
;
Wong, Yuen-Yee
This study investigates the time-dependent dielectric breakdown (TDDB) characteristics of La2O3/HfO2 and HfO2/La2O3 stacking layers on an n-In0.53Ga0.47As metal-oxide-semiconductor capacitor. Both designs improved the reliability compared with a single layer of HfO2. The TDDB followed the thermochemical E model. The current transportation mechanism changed from thermionic emission to Frenkel-Poole emission because of the traps creation under voltage stress. Both designs resulted in similar lifespans and voltage accelerating factors. However, the La2O3/HfO2 design had a longer lifespan because of the lower interface trap density and insertion of the HfO2 diffusion barrier layer between La2O3 and n-In0.53Ga0.47As. The oxide stacks exhibited excellent reliability and achieved a lifespan of 28.4 years. (C) 2016 The Japan Society of Applied Physics
The growth of pine-leaf-like hierarchical SnO2 nanostructures
(2014-01-01)
Dee, Chang Fu
;
Tiong, Teck Yaw
;
Varghese, Binni
;
Sow, Chorng-Haur
;
Wong, Yuan-Yee
Pine-leaf-like SnO2 hierarchical nanostructures (NSs) were grown by a two-step vapour transport deposition process with a combination of vapour-solid and vapour-liquid-solid mechanisms at the primary and secondary processes, respectively. This type of hierarchical structure consisted of SnO2 trunk with homo-branching nanowires (NWs). The branched NWs connected the trunk NWs at included angles of 56 degrees and 90 degrees for two different types of hierarchical NSs. Based on the thermodynamic calculation, the formation of branched NWs at those angles are all energetically favourable.
The growth of pine-leaf-like hierarchical SnO2 nanostructures
(2014-01-01)
Dee, Chang Fu
;
Tiong, Teck Yaw
;
Varghese, Binni
;
Sow, Chorng-Haur
;
Wong, Yuan-Yee
Pine-leaf-like SnO2 hierarchical nanostructures (NSs) were grown by a two-step vapour transport deposition process with a combination of vapour-solid and vapour-liquid-solid mechanisms at the primary and secondary processes, respectively. This type of hierarchical structure consisted of SnO2 trunk with homo-branching nanowires (NWs). The branched NWs connected the trunk NWs at included angles of 56 degrees and 90 degrees for two different types of hierarchical NSs. Based on the thermodynamic calculation, the formation of branched NWs at those angles are all energetically favourable.