Investigation on the Effect of Crystal Orientation Dependence of Pulse Porous Silicon for White Light Emission

2016 ◽  
Vol 701 ◽  
pp. 164-176 ◽  
Author(s):  
Nurul Hanida Abd Wahab ◽  
Alhan Farhanah Abd Rahim ◽  
Fatin Izzanis Mohamad Latar ◽  
Ainorkhilah Mahmood
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Visible Spectrum ◽  
Orientation Dependence ◽  
Etching Time ◽  
No Emission ◽  
Etching Technique ◽  
Three Samples ◽  
A Current

Porous silicon (PS) was formed by using an electrochemical pulse etching (PC) and conventional direct current (DC) etching techniques. The study aims to compare the effect of crystal orientations (n-type (100) and n-type (111)) on the formation of the PS under various conditions. For DC etching technique, the silicon wafers were etched in Hydrofluoric (HF) based solution with a current density of J=10 mA/cm2 for 30 minutes. While for the PC process, an electroless chemical etching with a different delay time (Td) of 0 min and 2 min were imposed before PC process starts. After that, the pulse current of J=10 mA/cm2 with the cycle time (T) of 10 ms and pause time (Toff) of 4ms were supplied in 30 min etching time in HF based electrolyte. Three samples from n-type (100) are DC1, PC1 and PC2 while the three samples from n-type (111) are DC2, PC3, and PC4 respectively. Field Emission Scanning Electron Microscopy (FESEM) images showed that the samples from n-type (100) produce more uniform circular structures and dense compared to n-type (111). The introduction of 2 minutes delay during PC process resulted in better structural of PS formation and also the optical properties shown by the Raman and Photoluminescence (PL) spectroscopies. For PL observation, the as grown Si shows no emission at the visible spectrum while all the PS samples (DC and PC techniques) exhibited significant broad spectrum between 500 nm to 900 nm respectively. It can be seen that the uniform circular pore of n-type (100) enhanced the PL emission indicated by the higher PL intensity (PC1 and PC2) compared to PC3 and PC4 from n-type (111). Raman spectroscopy showed that an improvement in the crystalline quality of PS in PC technique compared to DC indicated by the reduction of full width at half maximum (FWHM).

Effect of Electrolyte Volume Ratio on Electroluminescence of Porous Silicon Nanostructures (PSiNs) Intensity

2013 ◽  
Vol 686 ◽  
pp. 49-55
Author(s):  
M. Ain Zubaidah ◽  
N.A. Asli ◽  
Mohamad Rusop ◽  
Saifollah Abdullah
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Volume Ratio ◽  
Visible Range ◽  
Silicon Nanostructures ◽  
Etching Time ◽  
Light Emitting ◽  
Flat Screen ◽  
P Type

For this experiment, the main purpose of this experiment is to determine the electroluminescence of PSiNs samples with optimum electrolyte volume ratio of photo-electrochemical anodisation. PSiNs samples were prepared by photo-electrochemical anodisation by using p-type silicon substrate. For the formation of PSiNs on the silicon surface, a fixed current density (J=20 mA/cm2) and 30 minutes etching time were applied for the various electrolyte volume ratio. Volume ratio of hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), HF48%:C2H5OH was used for sample A (3:1), sample B (2:1), sample C (1:1), sample D (1:2) and sample E (1:3). The light emission can be observed at visible range. The effective electroluminescence was observed for sample C. Porous silicon nanostructures light–emitting diode (PSiNs-LED) has high-potential device for future flat screen display and can be high in demand.

Structural and Morphological Properties of Nano Photonic Silicon Structure for Photonics Applications

2020 ◽  
Vol 398 ◽  
pp. 29-33 ◽  
Author(s):  
Mariam M. Hassan ◽  
Makram A. Fakhri ◽  
Salah Aldeen Adnan
Keyword(s):  
Porous Silicon ◽  
Surface Morphology ◽  
Pore Diameter ◽  
Electrochemical Etching ◽  
Morphological Properties ◽  
Etching Time ◽  
Silicon Structure ◽  
Si Substrate ◽  
Etching Technique ◽  
Structure Surface

Porous silicon (n-PS) with diverse morphologies was prepared on silicon (Si) substrate via photo-electrochemical etching technique. We studies the structure, surface morphology, pore diameter, roughness, based on (XRD), (AFM), (SEM) at different etching time (5, 10 min) and current (10mA/cm2).

Study on the Effect of Porous Silicon Sizes for Potential Visible Photodetector

2015 ◽  
Vol 815 ◽  
pp. 121-130 ◽  
Author(s):  
Alhan Farhanah Abd Rahim ◽  
N.M. Sah ◽  
I.H. Hamzah ◽  
Siti Noraini Sulaiman ◽  
Musa Mohamed Zahidi
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Spectral Response ◽  
Quantum Confinement Effect ◽  
Visible Spectrum ◽  
Current Gain ◽  
Energy Band Gap ◽  
Current Voltage ◽  
Process Simulator

In this work, the characterization of porous silicon (PS) for potential visible light emission was investigated by simulation. SILVACO TCAD simulator was used to simulate PS by using process simulator, ATHENA and device simulator, ATLAS. Different pore diameter sizes of the PS structures were constructed. The structural, optical and electrical characteristics of the structures PS were investigated by current-voltage (I-V), current gain, spectral response and the energy band gap. It was observed that PS enhances the current gain compare to bulk Si and exhibited photo emission in the visible spectrum which constitutes to the quantum confinement effect of the Si in the PS structures.

scholarly journals The Effect of Etching Time On Structural Properties of Porous Quaternary AlInGaN Thin Films

2021 ◽  
Vol 19 (50) ◽  
pp. 77-83
Author(s):  
Ghasaq Ali Tomaa ◽  
Alaa Jabbar Ghazai
Keyword(s):  
Porous Silicon ◽  
Crystal Size ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Etching Time ◽  
Etching Technique ◽  
Force Microscopy ◽  
Atomic Force ◽  
Homogeneous Pattern

Using photo electrochemical etching technique (PEC), porous silicon (PS) layers were produced on n-type silicon (Si) wafers to generate porous silicon for n-type with an orientation of (111) The results of etching time were investigated at: (5,10,15 min). X-ray diffraction experiments revealed differences between the surface of the sample sheet and the synthesized porous silicon. The largest crystal size is (30 nm) and the lowest crystal size is (28.6 nm) The analysis of Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM) were used to research the morphology of porous silicon layer. As etching time increased, AFM findings showed that root mean square (RMS) of roughness and porous silicon grain size decreased and FESEM showed a homogeneous pattern and verified the formation of uniform porous silicon.

Crystal orientation dependence of alternating current photo-assisted (ACPEC) porous silicon for potential optoelectronic application

2019 ◽  
Vol 37 (1) ◽  
pp. 46-53
Author(s):  
Alhan Farhanah Abd Rahim ◽  
Aida Azrenda Mustakim ◽  
Nurul Syuhadah Mohd Razali ◽  
Ainorkhilah Mahmood ◽  
Rosfariza Radzali ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Crystal Orientation ◽  
Quantum Confinement Effect ◽  
Compressive Strain ◽  
Alternating Current ◽  
Orientation Dependence ◽  
Optical Characteristics ◽  
Etching Time ◽  
Content Type ◽  
Optoelectronic Application

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.

scholarly journals The effect of current density on the structures and photoluminescence of n-type porous silicon

2019 ◽  
Vol 15 (34) ◽  
pp. 15-28
Author(s):  
Isam M. Ibrahim
Keyword(s):  
Porous Silicon ◽  
Band Gap ◽  
Current Density ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Etching Time ◽  
Etching Technique ◽  
Force Microscopy ◽  
Homogeneous Pattern

Porous silicon (PS) layers were formed on n-type silicon (Si) wafers using Photo- electrochemical Etching technique (PEC) was used to produce porous silicon for n-type with orientation of (111). The effects of current density were investigated at: (10, 20, 30, 40, and50) mA/cm2 with etching time: 10min. X-ray diffraction studies showed distinct variations between the fresh silicon surface and the synthesized porous silicon. The maximum crystal size of Porous Silicon is (33.9nm) and minimum is (2.6nm) The Atomic force microscopy (AFM) analysis and Field Emission Scanning Electron Microscope (FESEM) were used to study the morphology of porous silicon layer. AFM results showed that root mean square (RMS) of roughness and the grain size of porous silicon decreased as etching current density increased and FESEM showed that a homogeneous pattern and confirms the formation of uniform porous silicon. The chemical bonding and structure were investigated by using Fourier transformation infrared spectroscopy (FTIR). The band gap of the samples obtained from photoluminescence (PL). These results showed that the band gap of porous silicon increase with increasing porosity.

A Highly Crystalline Anthracene-Based MOF-74 Series Featuring Electrical Conductivity and Luminescence

2019 ◽  
Author(s):  
Patricia Scheurle ◽  
Andre Mähringer ◽  
Andreas Jakowetz ◽  
Pouya Hosseini ◽  
Alexander Richter ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Metal Ions ◽  
Light Emission ◽  
Block Design ◽  
High Surface ◽  
Visible Spectrum ◽  
Building Blocks ◽  
Divalent Metal Ions ◽  
Conductivity Enhancement ◽  
Surface Areas

Recently, a small group of metal-organic frameworks (MOFs) has been discovered featuring substantial charge transport properties and electrical conductivity, hence promising to broaden the scope of potential MOF applications in fields such as batteries, fuel cells and supercapacitors. In combination with light emission, electroactive MOFs are intriguing candidates for chemical sensing and optoelectronic applications. Here, we incorporated anthracene-based building blocks into the MOF-74 topology with five different divalent metal ions, that is, Zn2+, Mg2+, Ni2+, Co2+ and Mn2+, resulting in a series of highly crystalline MOFs, coined ANMOF-74(M). This series of MOFs features substantial photoluminescence, with ANMOF-74(Zn) emitting across the whole visible spectrum. The materials moreover combine this photoluminescence with high surface areas and electrical conductivity. Compared to the original MOF-74 materials constructed from 2,5-dihydroxy terephthalic acid and the same metal ions Zn2+, Mg2+, Ni2+, Co2+ and Mn2+, we observed a conductivity enhancement of up to six orders of magnitude. Our results point towards the importance of building block design and the careful choice of the embedded MOF topology for obtaining materials with desired properties such as photoluminescence and electrical conductivity.

Fluorescent Nanotechnology: An Evolution in Optical Sensors

2020 ◽  
Vol 17 ◽  
Author(s):  
Dilawar Hassan ◽  
Hadi Bakhsh ◽  
Asif M. Khurram ◽  
Shakeel A. Bhutto ◽  
Nida S. Jalbani ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Sensors ◽  
Light Emission ◽  
Environmental Contaminants ◽  
Fluorescent Nanoparticles ◽  
Sensing Applications ◽  
Properties Of Materials ◽  
Optical Properties Of Materials ◽  
Fluorescent Nanomaterials

Background: The optical properties of nanomaterials have evolved enormously with the introduction of nanotechnology. The property of materials to absorb and/or emit specific wavelength has turned them into one of the most favourite candidates to be effectively utilized in different sensing applications e.g organic light emission diodes (OLEDs) sensors, gas sensors, biosensors and fluorescent sensors. These materials have been reported as a sensor in the field of tissue and cell imaging, cancer detection and detection of environmental contaminants etc. Fluorescent nanomaterials are heling in rapid and timely detection of various contaminants that greatly impact the quality of life and food, that is exposed to these contaminants. Later, all the contaminants have been investigated to be most perilous entities that momentously affect the life span of the animals and humans who use those foods which have been contaminated. Objective: In this review, we will discuss about various methods and approaches to synthesize the fluorescent nanoparticles and quantum dots (QDs) and their applications in various fields. The application will include the detection of various environmental contaminants and bio-medical applications. We will discuss the possible mode of action of the nanoparticles when used as sensor for the environmental contaminants as well as the surface modification of some fluorescent nanomaterials with anti-body and enzyme for specific detection in animal kingdom. We will also describe some RAMAN based sensors as well as some optical sensing-based nanosensors. Conclusion: Nanotechnology has enabled to play with the size, shape and morphology of materials in the nanoscale. The physical, chemical and optical properties of materials change dramatically when they are reduced to nanoscale. The optical properties can become choosy in terms of emission or absorption of wavelength in the size range and can result in production of very sensitive optical sensor. The results show that the use of fluorescent nanomaterials for the sensing purposes are helping a great deal in the sensing field.

Audit Reviewers' Judgments in Multiple Client Audit Environments

2017 ◽  
Vol 29 (2) ◽  
pp. 1-9 ◽  
Author(s):  
Sudip Bhattacharjee ◽  
Mario J. Maletta ◽  
Kimberly K. Moreno
Keyword(s):  
Audit Quality ◽  
Internal Audit ◽  
Contrast Effects ◽  
Comparative Information ◽  
A Current

ABSTRACT This study replicates Bhattacharjee, Maletta, and Moreno (2007), who find that audit preparers are susceptible to contrast effects in a multi-client environment. We demonstrate that auditors in the role of reviewers are also susceptible to contrast effects from a prior client. Audit reviewers' assessments of internal audit quality of a current client were significantly affected by the quality of the internal audit group of a client they previously reviewed. Specifically, when auditors first reviewed a client with a weak internal audit group they assessed the subsequent moderate internal audit group as being of higher quality than when they first reviewed a prior client with a strong internal audit group or did not review a prior client. Reviewers' documentation of evidence was also influenced by comparative information from the prior client. These results corroborate the key findings of Bhattacharjee et al. (2007) and confirm audit reviewers' susceptibility to contrast effects.

Change to the Demands Made of the Teaching Profession and the Ambiguity of New Concepts

2012 ◽  
Vol 2 (1) ◽  
pp. 7-18
Author(s):  
Jana Kohnová
Keyword(s):  
Teaching Profession ◽  
Further Education ◽  
Career Progression ◽  
Quality Of Education ◽  
Ministry Of Education ◽  
The Czech Republic ◽  
New Concepts ◽  
Educational Programmes ◽  
A Current

This paper is concerned with concepts such as quality of education, evaluation of the standard of the work of the teacher and comparison of educational results. It points to the importance of standards and the difficulties involved in their implementation. It also discusses the concept of competence and its relevance to framework educational programmes and the further education of teachers. The paper also focuses on a number of trends in education that are less widely discussed: instability — permanent change, reduction of education, emphasis on topicality and practical applicability, underestimation of the system, etc. The final part of the paper presents a current project from the Ministry of Education, Youth and Sport of the Czech Republic — a proposal for career progression.

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