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1 – 10 of 276Alireza Erfanian, Hamed Mehrara, Mahdi Khaje and Ahmad Afifi
– The purpose of this paper is to demonstrate a successful fabrication of 2 × 128 linear array of typical infrared (IR) detectors made of p-type tSi/porous Si Schottky barrier.
Abstract
Purpose
The purpose of this paper is to demonstrate a successful fabrication of 2 × 128 linear array of typical infrared (IR) detectors made of p-type tSi/porous Si Schottky barrier.
Design/methodology/approach
Using metal-assisted chemical etching (MaCE) as a unique approach, a sample definition of a porous Si nanostructure region for fabricating of any high-density photodetectors array has been formulated. Besides, the uniformity of pixels at different position along the array has been confirmed by optical images and measurements of photocurrent in IR regime at room temperature.
Findings
The experimental result illustrates the existence of an open-circuit voltage up to 30 mV at 1.5-μm wavelength for an area of 50 × 50 μm2. Additionally, this behavior is almost the same at different pixels of fabricated array.
Research limitations/implications
The uniformity of pixels and definition of nanostructure region are two most important challenges in fabrication of any high-density photodetectors array.
Practical implications
MaCE guarantees formation of reproducible, high-fidelity and controllable nanometer-size porous Si with well-defined and sharp edges of the patterned areas.
Originality/value
The proposed method offers a low-cost and simple process to fabricate high-density arrays of Schottky detectors which are compatible with the complementary metal-oxide semiconductor process.
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A.F. Abd Rahim, M.R. Hashim and N.K. Ali
The purpose of this paper is to describe a very low‐cost way to prepare Ge nano/microstructures by means of filling the material inside porous silicon (PS) using a conventional…
Abstract
Purpose
The purpose of this paper is to describe a very low‐cost way to prepare Ge nano/microstructures by means of filling the material inside porous silicon (PS) using a conventional and cost effective technique in which thermal evaporator with PS acts as patterned substrate. Also, the potential metal‐semiconductor‐metal (MSM) photodetector IV characteristics of the structure are demonstrated.
Design/methodology/approach
PS was prepared by anodization of Si wafer in ethanoic hydrofluoric acid. The Ge layer was then deposited onto the PS by thermal evaporation. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400°C for 10 min. Structural analysis of the samples was performed using energy dispersive X‐ray analysis (EDX), scanning electron microscope (SEM), X‐ray diffraction (XRD) and Raman spectroscopy.
Findings
A uniform circular network distribution of pores is observed with sizes estimation of 100 nm to 2.5 μm by SEM. Also observed are clusters with near spherical shape clinging around the pores believed to be Ge or GeO2. The EDX spectrum suggests the presence of Ge or GeO2 on and inside the pore structure. Raman spectrum showed that good crystalline structure of the Ge can be produced inside the silicon pores. XRD showed the presence of a Ge phase with the diamond structure by (111), (220), and (400) reflections. Finally, current‐voltage (I‐V) measurement of the Si/Ge/PS MSM photodetector was carried out. It showed lower dark currents compared to control device of Si. The device showed enhanced current gain compared to conventional Si device which can be associated with the presence of Ge nanostructures in the PS.
Originality/value
This paper shows that it is possible to grow Ge nano/microstructure on PS by using a simple and low‐cost method of thermal evaporation and thermal annealing and demonstrates potential MSM photodetector IV characteristics from the device.
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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 effect of…
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.
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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 porosity…
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).
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Fatimah Zulkifli, Rosfariza Radzali, Alhan Farhanah Abd Rahim, Ainorkhilah Mahmood, Nurul Syuhadah Mohd Razali and Aslina Abu Bakar
Porous silicon (Si) was fabricated by using three different wet etching methods, namely, direct current photo-assisted electrochemical (DCPEC), alternating CPEC (ACPEC) and…
Abstract
Purpose
Porous silicon (Si) was fabricated by using three different wet etching methods, namely, direct current photo-assisted electrochemical (DCPEC), alternating CPEC (ACPEC) and two-step ACPEC etching. This study aims to investigate the structural properties of porous structures formed by using these etching methods and to identify which etching method works best.
Design/methodology/approach
Si n(100) was used to fabricate porous Si using three different etching methods (DCPEC, ACPEC and two-step ACPEC). All the samples were etched with the same current density and etching duration. The samples were etched by using hydrofluoric acid-based electrolytes under the illumination of an incandescent lamp.
Findings
Field emission scanning electron microscopy (FESEM) images showed that porous Si etched using the two-step ACPEC method has a higher porosity and density than porous Si etched using DCPEC and ACPEC. The atomic force microscopy results supported the FESEM results showing that porous Si etched using the two-step ACPEC method has the highest surface roughness relative to the samples produced using the other two methods. High resolution X-ray diffraction revealed that porous Si produced through two-step ACPEC has the highest peak intensity out of the three porous Si samples suggesting an improvement in pore uniformity with a better crystalline quality.
Originality/value
Two-step ACPEC method is a fairly new etching method and many of its fundamental properties are yet to be established. This work presents a comparison of the effect of these three different etching methods on the structural properties of Si. The results obtained indicated that the two-step ACPEC method produced an etched sample with a higher porosity, pore density, surface roughness, improvement in uniformity of pores and better crystalline quality than the other etching methods.
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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 and…
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.
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Amirul Syafiq, Farah Khaleda Mohd Zaini, Vengadaesvaran Balakrishnan and Nasrudin Abd. Rahim
The purpose of this paper is to introduce the simple synthesis process of thermal-insulation coating by using three different nanoparticles, namely, nano-zinc oxide (ZnO), nano…
Abstract
Purpose
The purpose of this paper is to introduce the simple synthesis process of thermal-insulation coating by using three different nanoparticles, namely, nano-zinc oxide (ZnO), nano-tin dioxide (SnO2) and nano-titanium dioxide (TiO2), which can reduce the temperature of solar cells.
Design/methodology/approach
The thermal-insulation coating is designed using sol-gel process. The aminopropyltriethoxysilane/methyltrimethoxysilane binder system improves the cross-linking between the hydroxyl groups, -OH of nanoparticles. The isopropyl alcohol is used as a solvent medium. The fabrication method is a dip-coating method.
Findings
The prepared S1B1 coating (20 Wt.% of SnO2) exhibits high transparency and great thermal insulation property where the surface temperature of solar cells has been reduced by 13°C under 1,000 W/m2 irradiation after 1 h. Meanwhile, the Z1B2 coating (20 Wt.% of ZnO) reduced the temperature of solar cells by 7°C. On the other hand, the embedded nanoparticles have improved the fill factor of solar cells by 0.2 or 33.33%.
Research limitations/implications
Findings provide a significant method for the development of thermal-insulation coating by a simple synthesis process and low-cost materials.
Practical implications
The thermal-insulation coating is proposed to prevent exterior heat energy to the inside solar panel glass. At the same time, it can prevent excessive heating on the solar cell’s surface, later improves the efficiency of solar cell.
Originality/value
This study presents a the novel method to develop and compare the thermal-insulation coating by using various nanoparticles, namely, nano-TiO2, nano-SnO2 and nano-ZnO at different weight percentage.
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Amirul Syafiq, Vengadaesvaran Balakrishnan and Nasrudin Abd. Rahim
This paper aims to design the nano-titanium dioxide (TiO2) coating system which has superhydrophilic property, self-cleaning mechanism and antifog property as well as strong…
Abstract
Purpose
This paper aims to design the nano-titanium dioxide (TiO2) coating system which has superhydrophilic property, self-cleaning mechanism and antifog property as well as strong adhesion on glass substrate.
Design/methodology/approach
Two hydrophilic materials have been used such as TiO2 nanoparticles as fillers and hydrophilic copolymer, Pluronic F-127 by using simple sol–gel approach. The prepared solution was applied onto glass through dip- and spray-coating techniques and then left for drying at ambient temperature.
Findings
The nano-TiO2 superhydrophilic coating has achieved the water contact angle of 4.9° ± 0.5°. The superhydrophilic coating showed great self-cleaning effect against concentrated syrup and methylene blue where thin layer of water washes the dirt contaminants away. The nano-TiO2 coating exhibits great antifog performance that maintains high transparency of around 89% when the coated glass is placed above hot-fog vapor for 10 min. The fog droplets were condensed into water film which allowed the transmission of light through the glass. The strong adhesion of coated glass shows no total failure at scratch profile when impacted with scratch load of 500, 800 and 1,200 mN.
Research limitations/implications
Findings will be useful in the development of self-cleaning superhydrophilic coating that is applicable on building glass and photovoltaic panel.
Practical implications
The developed nano-TiO2 coating is developed by the combination of hydrophilic organic copolymer–inorganic TiO2 network to achieve great superhydrophilic property, optimum self-cleaning ability and supreme antifog performance.
Social implications
The findings will be useful for residents in building glass window where the application will reduce dust accumulation and keep the glass clean for longer period.
Originality/value
The synthesis of nano-TiO2 superhydrophilic coating which can be sprayed on large glass panel and cured at ambient temperature.
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Mica Grujicic, Ramin Yavari, Jennifer Snipes and S Ramaswami
In the present work, a new blast-/ballistic-impact mitigation concept is introduced and its efficacy analyzed using advanced computational methods and tools. The concept involves…
Abstract
Purpose
In the present work, a new blast-/ballistic-impact mitigation concept is introduced and its efficacy analyzed using advanced computational methods and tools. The concept involves the use of a zeolite protective layer separated by air from the structure being protected and in contact with a water layer in front. The paper aims to discuss these issues.
Design/methodology/approach
To properly capture the attendant nano-fluidics phenomena, all the calculations carried out in the present work involved the use of all-atom molecular-level equilibrium and non-equilibrium molecular-dynamics simulations.
Findings
Under high-rate loading, water molecules (treated as a nano-fluidic material) are forced to infiltrate zeolite nanopores wherein, due to complex interactions between the hydrophobic nanopore walls and the hydrogen bonds of the water molecules, water undergoes an ordering-type phase transition and acquires high density, while a significant portion of the kinetic energy of the water molecules is converted to potential energy. Concomitantly, a considerable portion of this kinetic energy is dissipated in the form of heat. As a result of these energy conversion/dissipation processes, the (conserved) linear momentum is transferred to the target structure over a longer time period, while the peak loading experienced by the structure is substantially reduced.
Originality/value
To the authors’ knowledge, the present work constitutes the first reported attempt to utilize pure SiO2 hydrophobic zeolites in blast-/ballistic-impact protection applications.
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P.M.Z. Hasan, Sheikh S. Islam, Tarikul Islam, Ameer Azam and Harsh
The purpose of this paper is to present the dependence of capacitive sensing of organic vapours by porous silicon (PS) on its molecular structure for the realization of a organic…
Abstract
Purpose
The purpose of this paper is to present the dependence of capacitive sensing of organic vapours by porous silicon (PS) on its molecular structure for the realization of a organic vapour sensor, compatible with existing silicon technology, with desired miniaturization and selectivity.
Design/methodology/approach
The method introduces large surface area of PS obtained by electrochemically etching of silicon wafer for characterization of organic vapours through capacitive sensing.
Findings
The method provides a comparative study of sensor response for organic vapour molecules of different structures and leads to an insight into the sensing mechanism.
Research limitations/implications
The surface of PS has been stabilized by thermal oxidation process.
Practical implications
The method is useful for the development of a simple, cost‐effective sensor for selective gas analysis.
Originality/value
The result is an outcome of regular experimental work carried out to observe the capacitive sensing behavior of PS for different organic vapours.
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