Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : porous silicon

Study of the Influence of Incorporation of Gold Nanoparticles on the Modified Porous Silicon Sensor for Petroleum Gas Detection

A.M. Alwan; A.B. Dheyab; A.J. Allaa

Engineering and Technology Journal, 2017, Volume 35, Issue 8, Pages 811-815

In this work, the influence of alloying the porous surface with uniform distributed gold nanoparticles on the characteristic porous silicon gas sensors for petroleum gas detection has been fabricated and studied extensively. Well-controlled gold nanoparticles were prepared by employing the simple dipping process of the macro porous silicon surface in diluted concentrations of HAuCl4 salt aqueous solution. The sensing properties of the prepared porous silicon-based sensors, sensitivity response and recovery times at room temperature operating in CO gas were studied. The sensitivity of alloyed porous silicon increased from 38% to about 82% incorporation of gold nanoparticles. The lowest gas pressure detection process of CO molecules was improved from 1 mbar to 0.5 mbar. The surface alloying with rounded gold nanoparticles improved the integrated specific surface area of the alloyed porous silicon/gold nanoparticles structure, so efficient gas developed with the low-cost process.

Gradient-Porosity Porous Silicon (GPSi) as Anti-reflection Coating in Solar Cells Applications

Alwan M. Alwan; Suaad M. Ali

Engineering and Technology Journal, 2015, Volume 33, Issue 1, Pages 152-159

Laser Assisted Etching (LAE) technique with short laser wavelength was used to provide a gradient-porosity porous silicon (GPSi) layer. Morphological aspects, reflectivity and photoelectric properties of (GPSi) layer were studied based on a bare solar cell substrate (p-n). The results show that the (GPSi) layer has a lower reflectivity of about (1.3%) comparing with bulk silicon (reference sample 50%) and single layer PSi of about (10.5%) at wavelength regime (400 nm). The surface morphology and x-section images present the formation of (GPSi) with layer thickness of about (400 nm) less than the junction depth. The photoelectrical properties of (GPSi) layer shows an increase of short circuit current density of (2.8 mA/cm2) compared with the ordinary solar cell of (2.15 mA/cm2) while for single layer PSi is about (2.05 mA/cm2).

Enhancement of Porous Silicon Formation by Using Laser Irradiation

Aseel A. Hadi

Engineering and Technology Journal, 2013, Volume 31, Issue 3, Pages 348-356

In this work porous silicon where prepared by chemical etching assisted with laser. The structural and optical properties of porous silicon are investigated using atomic force microscopy (AFM) and FTIR spectroscope. FTIR spectrum exhibit the formation of SiHx (x=1,2) and Si-O bonds. The atomic force microscopy AFM investigation shows the surface roughness (RMS observed was 1.52nm with laser and 1. 86 nm without laser ) and pyramid like hillocks surface on entire surface which can be regarded as a condensation point to form small skeleton clusters which plays an important role for the strong visible luminescence.

I-V and C-V Characteristics of Porous Silicon Nanostructures by Electrochemical Etching

Fatima I. Sultan; Amna A. Slman; Uday M. Nayef

Engineering and Technology Journal, 2013, Volume 31, Issue 3, Pages 332-338

Porous silicon (PS) layers has been prepared in this work by electrochemical etching (ECE) technique of a p-type silicon wafer with resistivity (1.5-4 Ω.cm) in hydrofluoric (HF) acid of 20% concentration. Various affecting studied etching time (10, 30, and 45 min) and current density (15 mA/cm2). We have study the morphological properties (AFM) and the electrical properties (I-V and C-V).
The atomic force microscopy investigation shows the rough silicon surface, with increasing etching process (etching time) porous structure nucleates which leads to an increase in the depth and width (diameter) of surface pits. Consequently, the surface roughness also increases.
The electrical properties of prepared PS; namely current density-voltage characteristics under dark, show that the pass current through the PS layer decreased by increasing the etching time, due to increase the resistivity of PS layer. The PS layer shows a rectifying behaviour with different rectification ratio. C-V measurements shows that the increase of the etching time decreases the capacitance of the PS layer. This behavior was attributed to the increasing in the depletion region width which leading to the increasing of built-in potential.

The Photoluminescence Characteristics of Partially and Fully (P-N) Porous Silicon

Alwan M. Alwan; Muna. S. M. Jawad

Engineering and Technology Journal, 2013, Volume 31, Issue 3, Pages 391-399

In this work, we present results of photoluminescence (PL) properties of fully (p-n) porous silicon device. Porous silicon layer has been prepared by Photo-electrochemical etching under different etching time of abrupt (p-n) silicon junction. The photoluminescence spectra, it is found that the formation of fully penetrate porous silicon layer can lead to decrease in the photoluminescence intensity. The reduction of the PL intensity is referred to the increase of non- radiative recombination process between the electron and hole. The obtained fully porous silicon layer in high etching time regime and this layer cannot be used for perpetration of light emitting devices, while the partially (p-n) porous silicon layer in the PL intensity has a higher value and good characteristics, this layer is suitable for (LED).

Characteristics of Nanostructure Porous Silicon Prepared by Anodization Technique

Ayoub H. Jaafar; Uday M. Nayef

Engineering and Technology Journal, 2013, Volume 31, Issue 3, Pages 339-347

Porous silicon (PS) layers are prepared by anodization for different current densities. The samples are then characterized the nanocrystalline porous silicon layer by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR), Reflectivity and Raman. PS layers were formed on a p-type Si wafer. anodized electrically with a 10 and 40 mA/cm2 current density for fixed 20 min etching times.
We have estimated crystallites size from X-Ray diffraction about nanoscale for porous silicon and AFM confirms the nanometric size and therefore optical properties about nanocrystalline silicon yields a Raman spectrum showing a broadened peak shifted below 520 cm-1.

Study of Characteristics of Porous Silicon by Electrochemical Etching

Hasan Hadi Hussein

Engineering and Technology Journal, 2013, Volume 31, Issue 1, Pages 34-38

In this work, the nanocrystalline porous silicon layer is prepared by electrochemical etching of p-type silicon wafer. The morphological films characterized have been studied of the by atomic force microscopy, XRD and FTIR spectroscopy.
The atomic force microscopy investigation shows the average diameter pore is increasing with increase of etching time.
The X-ray diffraction investigates of the porous silicon layer is shown the broadening the width of the peak compare with the bulk silicon is directly correlated to the size of the nano-scale. The FTIR spectra for porous silicon are shown that the dominant bonds being Si-H groups.

Enhancement of Porous Silicon Formation by Using Ultrasonic Vibrations

Ali H. Al-Hamdani

Engineering and Technology Journal, 2012, Volume 30, Issue 5, Pages 849-854

Anodic electrochemical etching enhanced by ultrasonically is developed to fabricate luminescent porous silicon (PS) material. The samples prepared by the new etching method exhibit superior characteristics to those prepared by conventional direct current etching. By applying ultrasonically enhanced etching, PS microcavities with much higher quality factors can be fabricated. The improved quality induced by
ultrasonic etching can be ascribed to increased rates of escape of hydrogen bubbles and other etched chemical species from the porous silicon pores surface.

Carrier Life Time, Time Constant, And Other Related Detector Parameter For Porous Silicon /Silicon Heterojunction Detector

Evan T. Salem

Engineering and Technology Journal, 2010, Volume 28, Issue 18, Pages 5660-5673

In the present work, Porous silicon constituting silicon nanostructures layer
have been produce on crystal silicon using different preparation condition in laser
induced electrical etching process. Were a (800 nm) , (1watt) semiconductor laser
has been used with the electrochemical etching process to prepare the porous layer
on the surface of (111) n- type silicon substrate. Two different Silicon resistivities
of (0.564,4.29) was employed to prepared (Ps/ Si) heterojunction at different
preparation condition. The characteristic of the prepared device has been found to
depend directly on the formation current density and substrate resistivity. The
obtained device has good parameter to work as a detector in the (V- NIR) region .

Surface Area of Porous Silicon

Mayasa AbdulWahid Shanon; Mayada.H.Mouhsen; Bassam.G.Rasheed

Engineering and Technology Journal, 2010, Volume 28, Issue 9, Pages 1728-1734

The surface area of porous silicon layers produced by different methods has
been measured in this work. It is found that the surface area of the porous silicon
is optimum when high laser power density is used to etch n –type silicon wafer via
the laser induced etching process compared with that for porous silicon produced
by lower laser power density or by electrochemical etching process. A scanning
electron microscope (SEM) micrographs were used to estimate the surface area.
The surface area of the porous layer is strongly dependent on the porous layer
geometry and its depth.

Formation and Characteristics Study of Nanostractured Solar Cell

Yasmeen Z. Dawood; Bassam G. Rasheed; Ali H. Al-Hamdani

Engineering and Technology Journal, 2009, Volume 27, Issue 15, Pages 2844-2852

Electrochemical and photoelectrochemical etching technique have been
employed to produce nanostructured solar cell. Various preparation conditions were examined. The I-V characteristics measurements were adopted to study effects of these parameters on the solar cell efficiency. We found that when shorter laser wavelength used to illuminate the porous layer during the etching process, the conversion efficiency of the solar cell increases . While doping the porous layer with phosphorous increases the nanostructured solar cell efficiency
by 30 %

Physical Properties of MOS Porous Silicon Detector Fabricated under RTO Method

Narges Z. Abdulzahra; Wafaa K. Khalaf; Alwan M. Alwan

Engineering and Technology Journal, 2009, Volume 27, Issue 11, Pages 2286-2291

In this research we studying the sensitivity of a porous silicon photo detector, we
found it improved through rapid thermal oxidation processes. Under our optimum
preparation conditions, photocurrent can reach about 3408 μA (under power density 100
mW/cm2 tungsten lamp illumination) and dark current is about 300μA
(at reverse bias of 5V).

The Effect Of Thermal Oxidation Time On The Structure And Influence On Optical Properties For Porous Silicon Prepared By Photo Electrochemical Etching

Narges Z.Abd alzahra; Alwan M.Alwan

Engineering and Technology Journal, 2009, Volume 27, Issue 4, Pages 727-735

The morphological properties of the freshly and oxidized porous silicon at
oxidation time (60, 90) sec were studied. A blue emission from PSi can be seen with
eyes after thermal oxidation because the increasing of energy gab due to decreased
silicon column (nano particles).Pore size and shape of n-type wafers are estimate and
correlated with optical properties before and after rapid thermal oxidation (RTO).

Organic Vapors Sensor Based on Dangling Bonds of Porous Silicon

Alwan M. Alwan

Engineering and Technology Journal, 2007, Volume 25, Issue 8, Pages 1023-1027

In this paper, a porous silicon (PS) layer is investigated as a sensing material
to detect the organic vapors with low concentration. The structure of the
prepared sensor consists of thin Au /PS/n-Si/Au thick where the PS is etched
photo -chemically. The current response of the sensor is governed by the
partial depletion of silicon located between two adjacent (porous
regions).This depletion is due to the charges trapped on dangling bonds
associated with the silicon – porous silicon interface .