Thursday, March 13, 2014

Rapid formation of transparent CuAlO2 thin film by thermal annealing of Cu on Al2O3


Abstract

An 850-nm-thick CuAlO2 film was formed by solid state reaction of evaporated thin film Cu on c-cut Al2O3 (sapphire) at 1200 °C for reaction times as short as 10 min. X-ray diffractogram confirms the formation of (0 0 l) CuAlO2, indicating oriented growth of CuAlO2 on c-cut Al2O3. Fourier transformation infra-red (FTIR) spectra showed peaks corresponding to Cu–O, Al–O and O–Cu–O bonds, confirming further the CuAlO2 phase formation. UV–visible spectrum measurement showed high transparency of the film in the visible region with a direct band gap of 3.25 eV. The mechanism of the formation of the film is discussed.

Keywords

  • CuAlO2;
  • Solid-state reaction;
  • P-type;
  • Transparent conducting oxides

Characterization of anodic SiO2 films on P-type 4H-SiC


Abstract

The physical and electronic properties of 100–120-nm thick anodic silicon dioxide film grown on p-type 4H-SiC wafer and annealed at different temperatures (500, 600, 700, and 800 °C) have been investigated and reported. Chemical bonding of the films has been analyzed by Fourier transform infra red spectroscopy. Smooth and defect-free film surface has been revealed under field emission scanning electron microscope. Atomic force microscope has been used to study topography and surface roughness of the films. Electronic properties of the film have been investigated by high frequency capacitance–voltage and current–voltage measurements. As the annealing temperature increased, refractive index, dielectric constant, film density, SiC surface roughness, effective oxide charge, and leakage current density have been reduced until 700 °C. An increment of these parameters has been observed after this temperature. However, a reversed trend has been demonstrated in porosity of the film and barrier height between conduction band edge of SiO2 and SiC.

Keyword

  • Anodic oxidation;
  • Atomic force microscope;
  • Annealing;
  • Silicon carbide

Oxide-assisted growth of silicon nanowires by carbothermal evaporation


Abstract

Silicon nanowires (SiNWs) have successfully been synthesized by carbothermal evaporation method. By ramping-up the furnace system at 20 °C min−1 to 1100 °C for 6 h, the vertically aligned coexist with crooked SiNWs were achieved on the silicon substrate located at 12 cm from source material. The processing parameters such as temperature, heating rate, duration, substrate position and location are very important to produce SiNWs. Morphology and chemical composition of deposited products were investigated by field-emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray analysis (EDX). The existence of small sphere silicon oxide capped nanowires suggested that the formation of SiNWs was governed by oxide-assisted growth (OAG) mechanism.

Keywords

  • Evaporation and sublimation;
  • Silicon;
  • Carbon;
  • Silicon oxides;
  • Nanostructures

Microstructure and dielectric properties of CaCu3Ti4O12 ceramic


Abstract

CaCu3Ti4O12 (CCTO) was prepared by the solid state technique. The sample was calcined at 900 °C/12 h and sintered at 1050 °C/24 h, then subjected to XRD to ensure CCTO formation. The microstructure was observed by SEM. XRD results identified both samples as single phase CCTO, whereas the microstructure shows abnormal grain growth and large pores. Sintering was studied in the temperature range of 950–1050 °C for 3–12 h. Increasing sintering temperature enhances the density and secondary formation of Cu2O. A clear grain boundary and dense microstructure were observed. The results show that the sample sintered at 1040 °C/10 h yields a clearly uniform grain size with the highest εr (33,210).

Keywords

  • Sintering;
  • Microstructure;
  • Dielectric;
  • CCTO

Fabrication of BaTiO3 thin films through ink-jet printing


Abstract

BaTiO3 thin films were prepared by ink-jet printing aqueous solutions of TiO2 sol and soluble Ba salts. Higher pH values (pH > 13) as well as higher than stoichiometric Ba (Ba:Ti = 1.1:1) salt additions were required to compensate for the different aqueous solubilities of the Ba and the Ti. Impedance spectroscopy of the samples shows the thin film samples to have similar activation energy with bulk samples prepared through low temperature aqueous synthesis. The relative permittivity of the thin films (∼ 280) was lower than the bulk pellets (∼ 2750) which was attributed to the lower temperature heat treatment for the thin films.

Keywords

  • Sol–gel preparation;
  • Dielectrics;
  • Thin films

Microwave assisted sintering of CaCu3Ti4O12


Abstract

CaCu3Ti4O12 electroceramic was prepared by a microwave assisted solid-state reaction technique from CaCO3, CuO and TiO2 powders. Processing involved the preparation of raw material, mixing and milling, calcination, pellet forming and sintering processes. Conventional furnace and microwave assisted sintering processes were employed in order to improve phase structures, morphology and dielectric properties of CaCu3Ti4O12 ceramics. Surface and fracture FESEM analysis showed that the microwave assisted sintered CaCu3Ti4O12 produced better densification and more uniform grain size compared to the conventional sintered sample.

Keywords

  • A. Microwave processing;
  • B. Grain boundaries;
  • C. Dielectric properties;
  • D. Perovskites


The role of tin oxide addition on the properties of microwave treated CaCu3Ti4O12


Abstract

A microwave (MW) irradiation process was performed to pre-sintered CaCu3Ti4O12. A conventional furnace was used for calcination as well as for the sintering processes, whilst a domestic microwave oven was employed for MW irradiation in order to produce better morphology, improved phase structures and dielectric properties of CaCu3Ti4O12 products. SEM analysis shows that the microstructures of MW irradiated samples are denser, with larger grain size if compared to the untreated samples. Dielectric properties also have been improved by MW treatment with higher dielectric constant and lower dielectric loss. Meanwhile, the addition of tin oxide (SnO2) to CaCu3Ti4O12 provides strong effects on the dielectric constant of both without and with MW irradiated samples. It was found that the dielectric constant of CaCu3Ti4O12 decreases exponentially with mole percentages of SnO2. However, the addition of SnO2 shows better dielectric loss properties of CaCu3Ti4O12.

Keywords

  • Ceramics;
  • Heat treatment;
  • Electron microscopy;
  • Dielectric properties

Dielectric properties of Nb-doped CaCu3Ti4O12 electroceramics measured at high frequencies


Abstract

In this work, Nb dopant was introduced into CaCu3Ti4O12 (CCTO) electroceramic in order to improve the dielectric properties. The CCTO electroceramic was prepared using the solid state reaction method. An X-ray diffractometer (XRD) analysis proved the formation of a single CCTO phase after sintering at 1040 °C for 10 h. Abnormal grain growth was observed in undoped CCTO and 1 mol% Nb-doped CCTO. Normal grain growth was produced at Nb dopant levels higher than 3 mol%. Dielectric properties were measured at a frequency range of 1 MHz to 1 GHz. It was found that CCTO doped with 1 mol% Nb gave the highest dielectric constant of 18,000 at 1 MHz. Meanwhile, the lowest dielectric loss (0.31) at 1 MHz was given by CCTO doped with 10 mol% Nb. The dielectric constant between 10 MHz and 1 GHz was almost stable with values at around 500.

Keywords

  • Ceramics;
  • Solid state reaction;
  • Sintering;
  • Dielectric response;
  • Scanning electron microscopy;
  • X-ray diffraction

Improvement in dielectric properties of Zn-doped CaCu3Ti4O12


Abstract

A single-phase of calcium copper titanate (CaCu3Ti4O12) was produced at lower temperature and shorter calcination time via a combination of solid state reaction and mechanical alloying techniques. The raw materials mixture was subjected to fast ball-milling for 5 h. The mixture was calcined at 750 °C for 9 h to form a single-phase CaCu3Ti4O12. Effect of zinc dopant to the dielectric properties of CaCu3Ti4O12 had been studied. At lower frequencies, it was found that the dielectric constants had a minimum value at 1.5 mol% Zn. The minimum dielectric loss was observed at 5 mol% Zn. At 1 kHz, the dielectric loss decreases from 30% (undoped) to a minimum value of 18% at 5 mol% Zn dopant. This result indicates that certain Zn dopant can be used to improve the dielectric loss properties of CaCu3Ti4O12.

Keywords

  • Ceramics;
  • Mechanical alloying;
  • Dielectric response;
  • Microstructure;
  • Scanning electron microscopy

Electromagnetic interference shielding properties of sintered cement-based ceramics


Abstract

Cement-based ceramic pellets were prepared and their properties were studied for electromagnetic interference (EMI) shielding applications. The shielding materials were made of Portland cement with the addition of different concentrations of manganese oxide (MnO2) up to 10 wt%. The pellets were sintered at 850 °C for 5 h and then polished prior to characterizations of density, porosity, microstructures, dielectric properties, and EMI shielding effectiveness (SE). Results show that the MnO2–cement pellets have good dielectric properties, i.e. high dielectric constant (∼300) and low dielectric loss (<0 .3="" constant="" dielectric="" increased="" increasing="" mno="" sub="" the="" with="">2
content in the cement matrix. The SE values of the MnO2–cements fluctuated between 2 dB and 9 dB in the frequency range of 8–13 GHz. The sample with 10 wt% MnO2 additive had SE values of up to 9 dB. Most of the samples with high additive concentrations produced SE exceeding 7 dB.

Keywords

  • A. Sintering;
  • B. Composites;
  • C. Dielectric properties;
  • E. Functional applications;
  • Electromagnetic interference shielding;
  • Manganese oxide

High frequency response to the impedance complex properties of Nb-doped CaCu3Ti4O12 electroceramics


Abstract

Impedance analyses was performed on undoped and Nb-doped CaCu3Ti4O12 (CaCu3Ti4−xNbxO12+x/2; x = 0, 0.01, 0.03, 0.05, 0.1) to investigate their electrical properties. The pellet samples were prepared using the solid state reaction method. Silver electrode was deposited on both pellets’ surfaces for electrical measurement. The thermally etched samples showed tiny bumped domains within the grains. The existence of both domain and grain boundaries are believed to strongly influence the dielectric constant of CaCu3Ti4O12 (CCTO). Undoped CCTO showed two arcs of impedance complex plane while Nb-doped samples have three arcs. Each arc represents the constituent elements of the CCTO. The highest frequency arc is evidence that CCTO consists of conductive domains which measure about 1 Ω and are insulated by two types of barriers, i.e. domain boundary and grain boundary.

Highlights

► The thermally etched samples show tiny bumped domains within grain. ► The existence of both domain and grain boundaries are believed to strongly influence the dielectric constant of CCTO. ► Nb-doped CCTO give three arcs of impedance complex plane measured in the range frequency of 1 Hz to 1 GHz. ► Each arc represents the constituent elements of the CCTO. ► The highest frequency arc is evidence that CCTO consists of conductive domains which about 1 Ω and are insulated by two types of barrier, i.e. domain boundary and grain boundary.

Keywords

  • Powders-solid state reaction;
  • Grain boundaries;
  • Dielectric properties;
  • Impedance;
  • Perovskites


Influence of sintering parameters on melting CuO phase in CaCu3Ti4O12


Abstract

Dielectric material CaCu3Ti4O12 (CCTO) was prepared by solid state technique. CaCO3, TiO2, and CuO powders were mixed thoroughly in a ball mill for an hour and were calcined at 900 °C for 12 h. This is followed by sintering at a defined standard temperature for this work (1050 °C for 24 h). Other samples were prepared in a similar manner but with different sintering durations. Each of the sample’s microstructure was observed by a Scanning Electron Microscope (SEM). Meanwhile, Energy-dispersive X-ray Spectroscopy (EDX) analysis was done on fracture surfaces in order to examine the elements present at grain boundaries. Microstructure observations show the melting and abnormal grain growth with large pores. The solidified liquid at grain boundaries was verified as Cu rich region, as confirmed by EDX analysis. By using the SEM, microstructure of small grains with clear grain boundaries were obtained when sintering was done at temperatures lower than 1050 °C. The microstructure of CCTO was very sensitive to sintering parameters.

Keywords

  • CuO melt phase;
  • Microstructure;
  • CCTO

The sensing mechanism and detection of low concentration acetone using chitosan-based sensors

 

Abstract

This paper aims to discuss the usage of chitosan film sensors to detect acetone concentrations in human breath, in order to precisely diagnose diabetes mellitus in patients. Acetone concentration in the breath varies from 0.3 to 0.9 ppm in healthy people to more than 1.8 ppm for diabetics. This makes acetone a suitable chemical marker for diabetes diagnosis. Therefore, the preliminary study on the electrical laboratory testing of the chitosan film sensor properties to acetone vapor-contaminated air in range of 0.1–100 ppm was carried out at room temperature (∼25–30 °C) in normal air. Our results suggested that the proposed acetone-based gas sensor can operate at room temperature with a high performance demonstrated by good response, recovery, stability and repeatability. This trouble free, painless and steadfast technique will improve the current gold standard in diagnosing diabetes, enabling quick and early detection.

Keywords

  • Chitosan-based acetone sensor;
  • Diabetes mellitus;
  • Acetone vapor;
  • Electrical properties;
  • Electrochemical deposition

Volume 177, February 2013, Pages 522–52

A novel 5.8 GHz quasi-lumped element resonator antenna

 

Abstract

In this paper, a novel quasi-lumped element resonator antenna is presented. The proposed antenna consists of the interdigital capacitor in parallel with a straight line inductor and is fabricated on Duroid RC4003C circuit board. The entire arrangement was fed by a coaxial feed at a frequency of 5.8 GHz. The size, bandwidth and radiation patterns were studied. The proposed antenna exhibits better impedance bandwidth and significant size reduction in comparison with similar results obtained from the conventional microstrip patch antenna with similar feeding technique and resonant frequency. The size of the proposed antenna structure is 5.8 × 5.6 mm2 and experimental results are shown to be in good agreement with the design simulation.

Keywords

  • Quasi-lumped element;
  • Patch antenna;
  • Coaxial feed;
  • Resonator;
  • Antenna real estate

Volume 67, Issue 7, July 2013, Pages 557–563

Monday, October 21, 2013

Just Testing....
Absent for a long time, now I'm thinking to activate again this blog!

Saturday, October 9, 2010

My new website

Please visit my website at www.sdhutagalung.com

Thank you
.

Thursday, November 19, 2009

Silicon Nanowire Transistor (SiNWT)


Silicon Nanowire Transistor Fabricated by AFM Nanolithography

by

Sabar D. Hutagalung, Zainovia Lockman, Lew Kam Chung, A. Makarimi Abdullah

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Silicon nanowire transistor (SiNWT) is a new promising alternative architecture to the conventional planar technology for electronic device fabrication. In this invention, SiNWT is fabricated via formation of a nanoscale silicon oxide pattern on silicon-on-insulator (SOI) wafer using an atomic force microscopy (AFM) nanolithography. The AFM nanolithography technique is advantageous due to the imaging capability of AFM and the ability to write various patterns by controlling the probe movement over the sample surface. In AFM nanolithography, the force between the tip and sample surface is held constant while a fixed voltage bias is applied to generate the field-emitted current. To fabricate SiNWT pattern by AFM nanolithography, applied voltage between tip and sample surface, tip writing speed and environment humidity are controlled. Our SiNWT is consisted of a silicon nanowire as a channel with a set of source (S) and drain (D) pads. A lateral gate (G) pad is connected by another nanowire made to be as close as possible to the channel in the transistor structure. The fabrication process steps are including a SOI wafer preparation, patterning of a silicon nanowire transistor structure on SOI wafer by AFM nanolithography, and the etching processes of silicon layer and oxide patterns.


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dah bersara ke?

dah bersara ke blog ni?
not really yet! but why is static for so long time? busy.... busy and busy is a good reason. actually malas aje! bosan pun juga.

But

Currently, I'm setting up a new blog at http://sdhutagalung.com/. It still under development. Please visit it later. sabar ya......

<>

Thursday, April 30, 2009

FYP 2009 dinner: 28 April 2009








Gathering.... with my FYP and Postgraduate students
at Seafood Restaurant, Kuala Juru, Penang
28 April 2009


Thursday, April 9, 2009

Kabinet Rakyat

10/04/2009 9:49am

KUALA LUMPUR 10 April — Timbalan Perdana Menteri Tan Sri Muhyiddin Yassin hari ini mengetuai barisan menteri dan timbalan menteri yang dilantik semalam mengangkat sumpah jawatan dan taat setia serta sumpah simpan rahsia di hadapan Yang di-Pertuan Agong Tuanku Mizan Zainal Abidin di Istana Negara.

Upacara penuh adat istiadat itu disaksikan oleh Pemaisuri Agong Tuanku Nur Zahirah dan Perdana Menteri Datuk Seri Najib Tun Razak serta bekas perdana menteri Tun Abdullah Ahmad Badawi dan Tun Dr Mahathir Mohamad.

Upacara itu yang diadakan di Balairong Seri Istana Negara bermula tepat 9.30 pagi dengan penerimaan surat cara pelantikan oleh Muhyiddin selaku Timbalan Perdana Menteri.

Beliau melafazkan ikrar sumpah jawatan dan taat setia dan kemudian menandatangani dokumen rasmi pelantikan disaksikan oleh Presiden Mahkamah Rayuan Tan Sri Alauddin Mohd Sheriff dan Ketua Setiausaha Negara Tan Sri Mohd Sidek Hassan. - Bernama