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Article

Karel Král and Miroslav Menšík

In this work the experimental effect of a slow decay of the photoluminescence is studied theoretically in the case of quantum dots with an indirect energy band gap. The…

Abstract

In this work the experimental effect of a slow decay of the photoluminescence is studied theoretically in the case of quantum dots with an indirect energy band gap. The slow decay of the photoluminescence is considered as decay in time of the luminescence intensity, following the excitation of the quantum dot sample electronic system by a short optical pulse. In the presented theoretical treatment the process is studied as a single dot property. The inter-valley deformation potential interaction of the excited conduction band electrons with lattice vibrations is considered in the self-consistent Born approximation to the electronic self-energy. The theory is built on the non-equilibrium electronic quantum transport theory. The time dependence of the photoluminescence decay is estimated upon using a simple effective mass model. The numerical calculation of the considered model shows the power-law time characteristics of the photoluminescence decay in the long-time limit of the decay. We demonstrate that the nonadiabatic influence of the interaction of the conduction band electrons with the lattice vibrations provides a mechanism giving us the power-law time dependence of the photoluminescence intensity signal. This theoretical result emphasizes the role of the electron-phonon interaction in the nanostructures.

Details

World Journal of Engineering, vol. 11 no. 5
Type: Research Article
ISSN: 1708-5284

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Article

Asmiet Ramizy, Khalid Omar and Z. Hassan

The purpose of this paper is to synthesize Si (porous silicon (PS)) by laser‐induced etching (LIE) technique. The LIE process has the added advantage of a controlling size…

Abstract

Purpose

The purpose of this paper is to synthesize Si (porous silicon (PS)) by laser‐induced etching (LIE) technique. The LIE process has the added advantage of a controlling size and optical properties without using of electrodes. The LIE process is a promising technique for fabricating many optoelectronic devices including: light‐emitting devices, detectors, sensors and large‐scale integrated circuits.

Design/methodology/approach

PS has been fabricated by LIE technique. Surface morphology and structural properties of nanostructures are characterized by using scanning electron microscopy and X‐ray diffraction (XRD). Photoluminescence (PL) measurement is also performed at room temperature by using He‐Cd laser (λ=325 nm) and Raman scattering has been investigated using Ar+ laser (λ=514 nm).

Findings

Surface morphology indicated that chemical reaction has been initiated with laser power density of 12 W/cm2, resulting in irregular structure. Micro‐columns are structured on surface with laser power density of 25 W/cm2. The pores structures are confined to smaller size, and the walls between the pore become extremely thin and shorter at 64 W/cm2 power density and 120 min irradiation time. PL spectra at room temperature for PS prepared at power density of 64 W/cm2 and irradiation time of 120 min shows the blue shift of PL at 400 nm and the full‐width and half maximum is about 60 nm. The broadening of the band gap energy occurs with a decrease of the crystallite size. The average diameter of nanosize Si crystallites is about 6‐10 nm. XRD indicated that the broadening in spectrum is due to the small size crystallites.

Originality/value

LIE processes have been used to produce high‐luminescent nanocrystallites with small size and size distribution, which is due to the quantum confinement effect.

Details

Microelectronics International, vol. 27 no. 1
Type: Research Article
ISSN: 1356-5362

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Article

M.A. Abid, H. Abu Hassan, Z. Hassan, S.S. Ng, S.K. Mohd Bakhori and N.H. Abd Raof

The purpose of this paper is to study the structural and optical characterization of Alx Iny Ga1−xy N quaternary epilayers, which were grown on c‐plane (0001) sapphire…

Abstract

Purpose

The purpose of this paper is to study the structural and optical characterization of Alx Iny Ga1−xy N quaternary epilayers, which were grown on c‐plane (0001) sapphire substrates with AlN as buffer layers using plasma assisted molecular beam epitaxy technique with indium (In) mole fraction y ranging from 0.0 to 0.1 and constant aluminum (Al) mole fraction x=0.06.

Design/methodology/approach

High‐resolution X‐ray diffraction rocking curve (HRXRD‐RC), scanning electron microscopy (SEM), energy dispersive X‐ray spectrometry (EDX), and photoluminescence (PL) spectroscopy have been measured on quaternary Alx Iny Ga1−xy N thin films at room temperature.

Findings

HRXRD‐RC measurements confirmed that the Alx Iny Ga1−xy N alloys had wurtzite structure. SEM images, element composition analysis by EDX, provided the evidence to show the existence of defects inside the samples contaminated by silicon from previous growth leading to nonuniformity of the epilayers, which caused decreased in the quality of the samples. PL spectra show reducing of the integrated intensity and an increasing red shift with increasing in content with reference to the ternary sample Al0.06Ga0.94N. The existence of a large amount of nonradiative recombination centers are responsible for the reduced the luminescence and the red shift provided evidence to an increase in composition inside the Alx Iny Ga1−xy N quaternary alloys. Photoluminescence is used to determine the behavior of the near band edge emission represent the energy band gap of the quaternary films. The energy band gap decreases with increasing In composition from 0.01 to 0.1 mole fraction. This trend is expected since the incorporation of in reduced the energy band gap of ternary Al0.06Ga0.94N (3.529 eV). We have also investigated the bowing parameter of the variation of energy band gaps and found it to be very sensitive on in composition. A value of b=10.95 have been obtain for our quaternary Alx Iny Ga1−xy N alloys.

Originality/value

This study on quaternary samples described in this paper, clearly indicates that the present of defects due to impurity contaminations has a dominant role in determining the structural and optical properties of Alx Iny Ga1−xy N quaternary alloys.

Details

Microelectronics International, vol. 27 no. 3
Type: Research Article
ISSN: 1356-5362

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Article

Alhan Farhanah Abd Rahim, Aida Azrenda Mustakim, Nurul Syuhadah Mohd Razali, Ainorkhilah Mahmood, Rosfariza Radzali, Ahmad Sabirin Zoolfakar and Yusnita Mohd Ali

Porous silicon (PS) was successfully fabricated using an alternating current photo-assisted electrochemical etching (ACPEC) technique. This study aims to compare the…

Abstract

Purpose

Porous silicon (PS) was successfully fabricated using an alternating current photo-assisted electrochemical etching (ACPEC) technique. This study aims to compare the effect of different crystal orientation of Si n(100) and n(111) on the structural and optical characteristics of the PS.

Design/methodology/approach

PS was fabricated using ACPEC etching with a current density of J = 10 mA/cm2 and etching time of 30 min. The PS samples denoted by PS100 and PS111 were etched using HF-based solution under the illumination of an incandescent white light.

Findings

FESEM images showed that the porous structure of PS100 was a uniform circular shape with higher density and porosity than PS111. In addition, the AFM indicated that the surface roughness of porous n(100) was less than porous n(111). Raman spectra of the PS samples showed a stronger peak with FWHM of 4.211 cm−1 and redshift of 1.093 cm−1. High resolution X-ray diffraction revealed cubic Si phases in the PS samples with tensile strain for porous n(100) and compressive strain for porous n(111). Photoluminescence observation of porous n(100) and porous n(111) displayed significant visible emissions at 651.97 nm (Eg = 190eV) and 640.89 nm (Eg = 1.93 eV) which was because of the nano-structure size of silicon through the quantum confinement effect. The size of Si nanostructures was approximately 8 nm from a quantized state effective mass theory.

Originality/value

The work presented crystal orientation dependence of Si n(100) and n(111) for the formation of uniform and denser PS using new ACPEC technique for potential visible optoelectronic application. The ACPEC technique has effectively formed good structural and optical characteristics of PS.

Details

Microelectronics International, vol. 37 no. 1
Type: Research Article
ISSN: 1356-5362

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Article

Sharul Ashikin Kamaruddin, Mohd Zainizan Sahdan, Kah‐Yoong Chan, Mohamad Rusop and Hashim Saim

Zinc oxide (ZnO) is an emerging optoelectronic material due to its various functional behaviors. The purpose of this paper is to report on the fabrication and…

Abstract

Purpose

Zinc oxide (ZnO) is an emerging optoelectronic material due to its various functional behaviors. The purpose of this paper is to report on the fabrication and characterizations of ZnO microrods.

Design/methodology/approach

ZnO microrods were synthesized using sol‐gel immerse technique on oxidized silicon (Si) substrates. The oxidized Si substrates were immersed in ZnO aqueous solution for different times ranging from three to five hours. The surface morphologies of the ZnO microrods were examined using scanning electron microscope (SEM). In order to investigate the structural properties, the ZnO microrods were measured using an X‐ray diffractometer (XRD). The optical properties were measured using a photoluminescence (PL) spectrophotometer.

Findings

Characterization from SEM shows an enhanced growth of the ZnO rods with increasing immerse time. XRD characterizations demonstrate sharp and narrow diffraction peaks peculiar to ZnO, which implies that the rod is of high crystallinity. Based on the PL spectra, long immerse time results in the high peak in the UV region.

Originality/value

This paper concludes that the immerse time exerts an influence on the ZnO microrods. A longer immerse duration is preferred in the fabrication of the ZnO microrod, which is considered an emerging material for many advanced electronic and optoelectronic applications.

Details

Microelectronics International, vol. 27 no. 3
Type: Research Article
ISSN: 1356-5362

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Article

Asmiet Ramizy, Wisam J. Aziz, Z. Hassan, Khalid Omar and K. Ibrahim

The purpose of this paper is to describe how fabricate solar cell based‐on porous silicon (PS) prepared by electrochemical etching process is fabricated and the effect of…

Abstract

Purpose

The purpose of this paper is to describe how fabricate solar cell based‐on porous silicon (PS) prepared by electrochemical etching process is fabricated and the effect of porosity layer on the solar cell performance is investigated.

Design/methodology/approach

The techniques used include SiO2 thermal oxidation, ZnO/TiO2 sputtering deposition and PS prepared by electrochemical etching. Surface morphology and structural properties of porous Si were characterized by using scanning electron microscopy. Photoluminescence and Raman spectroscopy measurements were also performed at room temperature. Current‐voltage measurements of the fabricated solar cell were taken under 80 mW/cm2 illumination conditions. Optical reflectance was obtained by using optical reflectometer (Filmetrics‐F20).

Findings

Pore diameter and microstructure are dependent on anodization condition such as HF: ethanol concentration, duration time, temperature, and current density. On other hand, a much more homogeneous and uniform distribution of pores is obtained when compared with other wafer prepared with different electrolyte composition.

Originality/value

PS is found to be an excellent anti‐reflection coating against incident light when it is compared with another anti‐reflection coating and exhibits good light‐trapping of a wide wavelength spectrum which produce high efficiency solar cells (11.23 per cent).

Details

Microelectronics International, vol. 27 no. 2
Type: Research Article
ISSN: 1356-5362

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Article

Yi Xin, Zijiang Jiang, Wenwen Li, Zonghao Huang and Cheng Wang

This paper aimed to prepare a kind of ZnS nanoparticles/poly(phenylene vinylene) (PPV) nanofibre and investigate its properties. Because the ZnS nanoparticles are…

Abstract

Purpose

This paper aimed to prepare a kind of ZnS nanoparticles/poly(phenylene vinylene) (PPV) nanofibre and investigate its properties. Because the ZnS nanoparticles are important optoelectronic materials, their incorporation into one-dimensional (1D) nanoscale polymer matrices should be a meaningful subject for electrospinning.

Design/methodology/approach

ZnS/PPV composite nanofibres with an average diameter of 600 nm were successfully prepared by a combination of the in situ method and electrospinning technique. The nanofibres were electrospun from Zn(CH3COO)2·2H2O and PPV precursor composite solution, and the ZnS/PPV fibres were obtained by exposure of the electrospun fibres to H2S gas to prepare ZnS nanoparticles in situ. Such fibres were characterised using X-ray Diffraction (XRD), Fourier transform infrared, transmission electron microscope (TEM), scanning electron microscope and photoluminescence (PL). The photoelectric properties of the fibres obtained were also investigated.

Findings

XRD patterns proved that ZnS nanocrystals generated in the composite nanofibres. The TEM image showed that the nanocrystals were homogeneously dispersed in the nanofibres. The PL spectrum of ZnS/PPV composite nanofibres exhibited a blue shift relative to the PPV nanofibres. I-V curve of the single nanofibre device under 5.76 mW/cm2 light illumination showed that the composite nanofibres have good photoelectric properties.

Research limitations/implications

The comparisons of advantages between ZnS/PPV nanofibres with similar nanofibres will be further expanded in a later research.

Practical implications

Results demonstrate the promise of these novel nanostructures as ultraminiature photodetectors with the potential for integration into future hybrid nanophotonic devices and systems.

Originality/value

The integration of inorganic semiconductor nanoparticles into organic conjugated polymers leads to composite materials with unique physical properties and important application potential. In this work, ZnS nanoparticles were introduced into PPV by an in situ method, so as to obtain a kind of novel 1D nanomaterials with good photoelectric properties.

Details

Pigment & Resin Technology, vol. 44 no. 2
Type: Research Article
ISSN: 0369-9420

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Article

L.S. Chuah, Z. Hassan, S.S. Tneh, M.A. Ahmad, S.K. Mohd Bakhori and Y. Yusof

The purpose of this paper is to propose a simple physical evaporation route in which catalyst‐free zinc oxide (ZnO) nanoscrewdrivers were deposited on silicon (Si) (111…

Abstract

Purpose

The purpose of this paper is to propose a simple physical evaporation route in which catalyst‐free zinc oxide (ZnO) nanoscrewdrivers were deposited on silicon (Si) (111) substrates.

Design/methodology/approach

Prior to the deposition, the Si (111) wafer was cut into pieces of 2×2 cm2. Then, the wafers were dipped for 1 min into mixture buffered oxide etchant to remove native oxide. Then, the samples were rinsed in an ultrasonic bath cleaned with boiling acetone, ethanol, and de‐ionized (DI) water for 10 min. Lastly, the wafers were rinsed in 25 ml DI water in stirred and then were blown dry with nitrogen. In this technique, the starting material is high‐purity metallic zinc (Zn) powder (99.99 per cent pure). Following, the Zn films were then annealed under air environment in the furnace at 500°C for 1 h deprived of any catalysts.

Findings

These ZnO samples were studied by scanning electron microscopy, high‐resolution X‐ray diffraction (HR‐XRD), and photoluminescence (PL) spectroscopy. Atomic force microscope (AFM) images were applied to ascertain surface morphology of produced ZnO nanoscrewdrivers. XRD pattern confirmed that the ZnO nanoscrewdrivers were of polycrystalline structure in universe with a hexagonal close packed type and c‐axis is perpendicular to the substrate. The peak at 34° correspond to the reflection planes of ZnO(002) crystallographic plane is perceived. The AFM surface images disclosed that the surfaces of produced ZnO thin films are not smooth. The PL spectrum of as‐synthesized nanoscrewdrivers shows a UV emission peak at 380 nm and a broad green emission peak at 500 nm.

Originality/value

The paper reports on a simple physical evaporation route, ZnO nanoscrewdrivers were synthesized via the thermal evaporation of the high‐purity Zn powders and annealed at 500°C under air atmosphere without introducing any hetero‐metal catalysts or other carrier gases approach.

Details

Microelectronics International, vol. 28 no. 3
Type: Research Article
ISSN: 1356-5362

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Article

Sh. Fadaie, M.M. Kashani‐Motlagh, A. Maghsoudipour and B. Faridnia

The purpose of this paper is to evaluate the effect of copolymer and starting material concentrations in homogeneous precipitation synthesis of Yttria nanoparticles and…

Abstract

Purpose

The purpose of this paper is to evaluate the effect of copolymer and starting material concentrations in homogeneous precipitation synthesis of Yttria nanoparticles and red‐emitting nanophosphors Y2O3:Eu3+. N‐isopropylacrylamide and acrylic acid (NIPAM/AAc) and urea are used.

Design/methodology/approach

To optimise synthesis condition of Y2O3:Eu3+ nanophosphor NIPAM/AAc copolymer was used as a modifier and the effect of various concentration of yttrium ions, urea and precipitation time on size, morphology and emission spectra were investigated.

Findings

Using NIPAM/AAc copolymer shows significant improvement on size and dispersion of nanoparticles. It is found that yttrium concentration, varying between 0.006 and 0.03 M, has a profound impact on the average size of particles, which systematically increases from 65 to over 165 nm. The rate of precipitation reaction, however, is shown to be independent of yttrium concentration. In contrast, as urea concentration increases from 0.2 to 5 M, the average particle size exhibits a gradual decrease from 183 to 70 nm. At extremely high urea concentration such as 5 M, a significant level of inter‐particle agglomeration is observed.

Originality/value

Based on this paper, the authors have successfully prepared some promising nanophosphors. The nanoparticles are studied by X‐ray diffraction, transmission electronic microscopy, zeta sizer, Infra red and photoluminescence spectroscopy.

Details

Pigment & Resin Technology, vol. 39 no. 4
Type: Research Article
ISSN: 0369-9420

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Article

Morteza Enhessari

Inorganic pigments have been widely investigated due to their chemical stability such as resistance to chemical attacks by acids and alkalis, excellent hardness and high…

Abstract

Purpose

Inorganic pigments have been widely investigated due to their chemical stability such as resistance to chemical attacks by acids and alkalis, excellent hardness and high temperature stability. Cr1.3Fe0.7O3 which is considered as a ceramic nanopigment also seems to be a highly efficient photovoltaic material. The paper aims to discuss these issues.

Design/methodology/approach

In this work, the paper reports the synthesis of a novel and high purity Cr1.3Fe0.7O3 nanopigment via sol-gel process using stearic acid as complexing agent. The method includes formation of an organic precursor with metallic cations homogeneously distributed all over the matrix. Sample characterisations were performed by X-ray diffraction, electron microscopy, UV-vis diffused reflectance spectra and photoluminescence. The transport properties and colour characteristics were also investigated by spectroscopic and technological characterisation of the synthesised nanoparticles.

Findings

The prepared nanopigments were uniform in distribution and a spherical morphology with an average size of about 200 nm was observed. Cr1.3Fe0.7O3 nanoparticles showed a direct band gap value of 2.85 eV and the colour efficiency of the nanopigments evaluated by colourimetric analysis resulted characteristic values of L*=39.96, a*=3.67 and b*=3.12.

Originality/value

This method for synthesis of nanopigments is novel and could be employed for various applications in synthesis of wide variety of nanoceramics.

Details

Pigment & Resin Technology, vol. 42 no. 6
Type: Research Article
ISSN: 0369-9420

Keywords

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