Publications Archives &#8211; Page 12 of 13 &#8211; Institute of Nano Electronic Engineering

New optical features to enhance solar cell performance based on porous silicon surfaces

April 18, 2013 By Editor

Abstract – Electrochemical etching is used to fabricate porous silicon (PS) surfaces for both sides of the Si wafer. The effect of PS on performance of Si solar cells is investigated and the reflected mirrors are manipulated to enhance solar cell efficiency. The process is promising for solar cell manufacturing due to its simplicity, lower cost and suitability for mass production. The PS surface has discrete pores and short-branched pores on the polished wafer side. In contrast, the etched backside of the wafer has smaller pore size, with random pores. PS formed on both sides has lower reflectivity value compared with results in other works. Solar cell efficiency is increased to 15.4% with PS formed on both sides compared with the unetched sample and other results. Using empirical models, the optical properties of the refractive index and the optical dielectric constant are investigated. The porous surface texturing properties could enhance and increase the conversion efficiency of porous Si solar cells. The obtained results are in agreement with experimental and other data.

Keywords – Porous silicon, Solar cell, Crystalline silicon, Refractive index

Corresponding Author: Prof. Dr. Yarub Al-Douri
Corresponding Author’s Email: yarub@unimap.edu.my

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Preparation of iron oxide nanoparticles supported on magnesium oxide for producing high-quality single-walled carbon nanotubes

November 22, 2012 By Editor

Abstract – Fe3O4 nanoparticles with a narrow diameter distribution having an average diameter of 10.33 nm ± 2.99 nm (average diameter ± standard deviation) were prepared by a precipitation method. The Fe3O4 nanoparticles were supported on MgO by mixing the MgO nanopowder with the required amount of Fe3O4 nanoparticles in water under extensive sonication. Single-walled carbon nanotubes (SWCNTs) were synthesized by the chemical vapor deposition (CVD) of methane over the Fe3O4/MgO catalyst. Transmission electron microscopy showed that a large number of SWCNT bundles of nearly uniform diameter were produced by the CVD method. The average diameter of the produced SWCNTs was ca. 1.22 nm. Thermogravimetric analysis showed that the weight loss was approximately 19% by oxidation of carbon in the temperature range of 400-680 oC. The ratio of the intensity of the D-band to the G-band was 0.03, indicating that the SWCNTs were well-graphitized.

Keywords – Single-walled carbon nanotubes, Chemical vapor deposition, Electron microscopy, Raman spectroscopy

Corresponding Author: Liu Wei Wen
Corresponding Author’s Email: wwliu@unimap.edu.my

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Fabrication and Characterization of 50 nm Silicon Nano-Gap Structures

October 24, 2012 By Editor

Abstract – A simple method for the fabrication of nano-gaps less than 50 nm by using conventional photolithography combined with patterned-size reduction techniques is presented. Silicon material is used to fabricate the nano-gap structure and gold is used for the electrode. Two chrome masks are proposed to complete this work, the first mask for the nano-gap pattern and a second mask for the electrode. The method is based on the control of the coefficients (temperature and time) with an improved pattern size resolution by thermal oxidation. With this technique, there are no principal limitations to fabricating anostructures with different layouts down to several nanometers in dimension. In this work, the proposed method is experimentally demonstrated by preparing the nano-gaps on a Si–SiO2 substrate down to dimensions of 50 nm. The optical characterization that is applied to check the nano-gap structure is by using the scanning electron microscope (SEM).

Keywords – Nano-Gap, Pattern-Size Reduction, Nanostructure, Optical Characterization, Photolithography.

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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Carbon nano dots scale by focused ion beam system for MIS diode nano devices

October 3, 2012 By Editor

Abstract – Metal-insulator-semiconductor (MIS) structures with a nanocrystal carbon (nc-C) embedded in SiO2 thin films were fabricated using a focused ion beam (FIB) system with a precursor of low-energy Ga+ ion and carbon source. The crystallinity of nc-C was investigated by Raman spectroscopy and atomic force microscopy (AFM). Raman spectra indicate the evidence of crystallization of nc-C after annealed at 600˚C by the sharp peak at 1565 cm-1 in graphite (sp2), while no peak of diamond (sp3) could be seen at 1333 cm-1. The AFM images showed the nc-C dots controlled with diameter of 100 nm, 200 nm and 300 nm, respectively. The above results revealed that the nc-C dots had sufficiently stuck onto SiO2 films. The hysterisis loop in the capacitance–voltage characteristics appeared in the MIS device with SiO2/nc-C/SiO2 structure in which voltage shift is 0.32 V for radical oxidation and 0.14 V for dry oxidation, respectively.

Keywords – Carbon; Nanocrystal; Memory device; Focused ion beam; Raman spectroscopy; Atomic force microscopy

Corresponding Author: Ruslinda Abdul Rahim
Corresponding Author’s Email: ruslinda@unimap.edu.my

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The Alignment of Carbon Nano Tube between Aluminum Electrodes using AC Dielectrophoresis Method

September 26, 2012 By Editor

Abstract – This paper presents the recent development and fabrication of carbon nanotubes (CNT) based on electrical devices. The silicon oxide is formed by dry oxidation and the Aluminum (Al) layer is deposited using Thermal Evaporator. The electrodes pad act as a bridge for CNT alignment. Then, this single-walled carbon nanotubes (SWNTs) was suspended in isopropyl alcohol (IPA) and Dichloromethane (DCM) solution in ultrasonic condition around 1 hour continuously. Then, the aligment of the CNT was carried out using AC dielectrophoresis and DC electrophoresis method.

Keywords – CNT, DC electrophoresis method, AC dielectrophoresis method

Corresponding Author: Nur Hamidah Abdul Halim
Corresponding Author’s Email: nurhamidah@unimap.edu.my

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