Facile construction of vertically aligned ZnO nanorod / PEDOT : PSS hybrid heterojunction based ultraviolet light sensors : efficient performance and mechanism
The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency ... more The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confir...
ZnMgO-nanorod-based Schottky Light-emitting Diode Fabricated on n-SiC Substrate Using Low-temperature Method
Silicon
We fabricated a ZnMgOnanorodbased Schottky lightemitting diode (LED) on an n-SiC substrate using ... more We fabricated a ZnMgOnanorodbased Schottky lightemitting diode (LED) on an n-SiC substrate using a lowtemperature growth method. Study about structural properties of ZnMgO nanorods was carried out by field emission scanning electron microscopy (FE-SEM) and fourier-transforms infrared spectroscopy (FTIR). The electrooptical properties of the ZnMgO nanorods were investigated using photoluminescence (PL), electroluminescence (EL) and current–voltage measurements. The values of ideality factor, barrier height and series resistance were calculated 3.22 1.1eV and 187Ω, respectively. The understanding of the optical properties and luminescence performance of the ZnMgO-nanorod based Schottky LED is important for applications in optical nanodevices. The PL measurements of the ZnMgO nanorods revealed a blueshift of the ultraviolet (UV) emission peak, which suggests their potentials for the development of tunable optical nanodevices. The blueshift of the UV emission was attributed to the diffusion of Mg and formation of the ternary ZnMgO alloy. The EL spectra exhibited an emission band covering the visible range from 40 nm to 700 nm. Gaussian functions were employed to simulate the experimental data, which revealed that the emission band can be regarded as a superposition of violet, blue, green and yellow emissions.
Enhancement of external quantum efficiency and quality of heterojunction white LEDs by varying the size of ZnO nanorods
Nanotechnology
The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency ... more The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confirming that the quality of light generated by LEDs can be tuned by varying the length of the ZnO NRs. These results suggest that the EQE and visible deep band emission from n-ZnONRs/p-GaN heterojunction LEDs can be effectively controlled by adjusting the length of the ZnO NRs, which can be useful for realizing tunable white LEDs.
Influence of High Nitrogen Flux on Crystal Quality of Plasma-Assisted MBE Grown GaN Layers Using Raman Spectroscopy: Part-II
We have investigated lattice properties of plasma assisted MBE grown hexagonal GaN layers at vary... more We have investigated lattice properties of plasma assisted MBE grown hexagonal GaN layers at varying nitrogen and gallium fluxes using Raman spectroscopy. Room temperature Raman spectra of Ga-rich layers and stoichiometric GaN are similar showing excitation modes at 434 cm-1, 567 cm-1 and 729 cm-1 identified as residual laser line, E2H and A1(LO) mode, respectively. Similarity of Ga-rich and stoichiometric GaN layers is interpreted as the indication of comparable crystal quality of both GaN layers. In contrast, Raman scattering associated with N-rich GaN samples mere exhibit a broad band of excitations in the range of 250-650cm-1 leaving out A1(LO) mode. This typical observation along with intensity distribution of the peaks, is correlated with rough surface, bad crystal quality and high concentration of defects. Based on atomic displacement scheme, the broad band is identified as Ga- vacancies.
Summarization of Energy-Efficient Communication Protocols for smart grid
… Journal of Research and Reviews in …, 2012
... 1561 Summarization of Energy-Efficient Communication Protocols for Smart Grid Ayesha Afzaal, ... more ... 1561 Summarization of Energy-Efficient Communication Protocols for Smart Grid Ayesha Afzaal, Maria Saleemi, Mohsin Nazir, and Farhat Saleemi Department of Computer Science, Lahore College for Women University, Lahore, Pakistan Email: [email protected] ...
A partial-wave analysis of the (K+ K-[pi]-) system produced in [pi]-p--> K+ K-[pi]-p at 16 GeV/c
Nuclear Physics B, 1982
... FRENCH 4, SHP GEER6, P. GIRTLER, B. GHIDINI2, IS HUGHES5, JN JACKSON 6, JG LYNCH5, L. MANDELL... more ... FRENCH 4, SHP GEER6, P. GIRTLER, B. GHIDINI2, IS HUGHES5, JN JACKSON 6, JG LYNCH5, L. MANDELLI7, PW MINTO5, WA MITAROFF', K. MULLER3, G. OTTER, A. PALAN02 , L. PERINI 7, J. PINFOLD6, WH RANGE 6, JA RICHARDSON 6, G. RUDOLPH , F. SALEEMI5 ...
Wireless networks are one of the most essential components of the communication networks. In cont... more Wireless networks are one of the most essential components of the communication networks. In contrast to the wired networks, the inherent broadcast nature of wireless networks provides a breeding ground for both opportunities and challenges ranging from security to reliability. Moreover, energy is a fundamental design constraint in wireless networks. The boom of wireless network is closely coupled with the schemes that can reduce energy consumption. Network coding for the wireless networks is seen as a potential candidate scheme that can help overcome the energy and security challenges while providing significant benefits. This paper presents a basic model for formulating network coding problem in wireless setting. Since the optimal solution to wireless network coding is NP (nondeterministic polynomial-time)-hard, we intend to explore the impact of different parameters with random and non-random solutions. We present extensive simulation to show the strength of random network coding scheme in general wireless network scenarios. This study provide a comprehensive insight into the limits of wireless network coding.
ISAST Transactions on No. 1, Vol. 1, 2007 (ISSN 1797-1152) Computers and Software Engineering Reg... more ISAST Transactions on No. 1, Vol. 1, 2007 (ISSN 1797-1152) Computers and Software Engineering Regular Papers Marium Jalal Chaundry, Farhat Saleemi, M. Imran Shahid, and Fatima Jalal Chaudhry: A Comparison of Networking Features of Windows Vista, Free BSD, Sun ...
Synthesis and evaluation of factors affecting thein vitrobioactivity and antibacterial activity of bioactive glass ceramics
International Journal of Modern Physics B, 2016
In the present study, two novel silicate glass-ceramics having chemical composition 38SiO2–41CaO–... more In the present study, two novel silicate glass-ceramics having chemical composition 38SiO2–41CaO–6P2O5–([Formula: see text])Na2O–[Formula: see text]CaF2 ([Formula: see text], 0.43 mol%) were synthesized. These glass derivatives were subjected to stimulated body fluid for 24 days in SBF under static condition at [Formula: see text]C in order to evaluate the bioactive properties of specimens. The antibacterial activity of glass ceramics against three pathogenic bacteria was determined using the modified Kirby Bauer method. It was found that the antibacterial activity primarily depends on the dissolution rate; faster release of ions caused rapid increase in the pH of the solution. Antibacterial properties were found to be strongly affected by changes in the pH of supernatant. The in vitro bioactivity assays showed that both glass derivatives were capable of bonding with bone and secondly effectively inhibit bacteria. However, the glass ceramic without CaF2 (B2) showed high dissolution ...
Effect of Ti+4 on in vitro bioactivity and antibacterial activity of silicate glass-ceramics
Materials Science and Engineering: C, 2016
A novel glass-ceramic series in (48-x) SiO2-36 CaO-4 P2O5-12 Na2O-xTiO2 (where x=0, 3.5, 7, 10.5 ... more A novel glass-ceramic series in (48-x) SiO2-36 CaO-4 P2O5-12 Na2O-xTiO2 (where x=0, 3.5, 7, 10.5 and 14mol %) system was synthesized by crystallization of glass powders, obtained by melt quenching technique. The differential scanning calorimetric analysis (DSC) was used to study the non-isothermal crystallization kinetics of the as prepared glasses. The crystallization behaviour of glasses was analyzed under non-isothermal conditions, and qualitative phase analysis of glass-ceramics was made by X-ray diffraction. The in vitro bioactivity of synthesized glass-ceramics was studied in stimulated body fluid at 37°C under static condition for 24days. The formation of hydroxyl-carbonated apatite layer; evident of bioactivity of the material, was elucidated by XRD, FTIR, AAS, SEM and EDX analysis. The result showed that partial substitution of TiO2 with SiO2 negatively influenced bioactivity; it decreased with increase in concentration of TiO2. As Ti(+4) having stronger field strength as compared to Si(+4) so its replacement became the cause for reduction in degradation that in turn improved the chemical stability. The compressive strength was also enhanced with progress addition of TiO2 in the system. The antibacterial properties were examined against Staphylococcus Epidermidis. Strong antibacterial efficacy was observed with the addition of TiO2 in the system.
Structural and Optoelectrical Properties of ZnTe Thin Films Prepared by E-Beam Evaporation
Journal of Electronic Materials, 2016
ZnTe thin films have been prepared by an electron-beam evaporation technique on glass substrates,... more ZnTe thin films have been prepared by an electron-beam evaporation technique on glass substrates, changing the accelerating voltage and the substrate temperature at accelerating voltage of 2 kV. Structural analysis showed that all the films had cubic structure with preferential orientation along (111) direction, though (220) and (311) orientations were also present. The (111) peak intensity increased with increasing film thickness. The crystallite size increased with increasing film thickness. Conductivity measurements showed that the films were p-type. Films prepared at accelerating voltage of 2 kV exhibited minimum resistivity. Optical characterization indicated that both absorbing and transparent thin films can be achieved by using different deposition conditions. The optical bandgap value was found to vary with substrate temperature.
Facile construction of vertically aligned ZnO nanorod / PEDOT : PSS hybrid heterojunction based ultraviolet light sensors : efficient performance and mechanism
The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency ... more The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confir...
ZnMgO-nanorod-based Schottky Light-emitting Diode Fabricated on n-SiC Substrate Using Low-temperature Method
Silicon
We fabricated a ZnMgOnanorodbased Schottky lightemitting diode (LED) on an n-SiC substrate using ... more We fabricated a ZnMgOnanorodbased Schottky lightemitting diode (LED) on an n-SiC substrate using a lowtemperature growth method. Study about structural properties of ZnMgO nanorods was carried out by field emission scanning electron microscopy (FE-SEM) and fourier-transforms infrared spectroscopy (FTIR). The electrooptical properties of the ZnMgO nanorods were investigated using photoluminescence (PL), electroluminescence (EL) and current–voltage measurements. The values of ideality factor, barrier height and series resistance were calculated 3.22 1.1eV and 187Ω, respectively. The understanding of the optical properties and luminescence performance of the ZnMgO-nanorod based Schottky LED is important for applications in optical nanodevices. The PL measurements of the ZnMgO nanorods revealed a blueshift of the ultraviolet (UV) emission peak, which suggests their potentials for the development of tunable optical nanodevices. The blueshift of the UV emission was attributed to the diffusion of Mg and formation of the ternary ZnMgO alloy. The EL spectra exhibited an emission band covering the visible range from 40 nm to 700 nm. Gaussian functions were employed to simulate the experimental data, which revealed that the emission band can be regarded as a superposition of violet, blue, green and yellow emissions.
Enhancement of external quantum efficiency and quality of heterojunction white LEDs by varying the size of ZnO nanorods
Nanotechnology
The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency ... more The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confirming that the quality of light generated by LEDs can be tuned by varying the length of the ZnO NRs. These results suggest that the EQE and visible deep band emission from n-ZnONRs/p-GaN heterojunction LEDs can be effectively controlled by adjusting the length of the ZnO NRs, which can be useful for realizing tunable white LEDs.
Influence of High Nitrogen Flux on Crystal Quality of Plasma-Assisted MBE Grown GaN Layers Using Raman Spectroscopy: Part-II
We have investigated lattice properties of plasma assisted MBE grown hexagonal GaN layers at vary... more We have investigated lattice properties of plasma assisted MBE grown hexagonal GaN layers at varying nitrogen and gallium fluxes using Raman spectroscopy. Room temperature Raman spectra of Ga-rich layers and stoichiometric GaN are similar showing excitation modes at 434 cm-1, 567 cm-1 and 729 cm-1 identified as residual laser line, E2H and A1(LO) mode, respectively. Similarity of Ga-rich and stoichiometric GaN layers is interpreted as the indication of comparable crystal quality of both GaN layers. In contrast, Raman scattering associated with N-rich GaN samples mere exhibit a broad band of excitations in the range of 250-650cm-1 leaving out A1(LO) mode. This typical observation along with intensity distribution of the peaks, is correlated with rough surface, bad crystal quality and high concentration of defects. Based on atomic displacement scheme, the broad band is identified as Ga- vacancies.
Summarization of Energy-Efficient Communication Protocols for smart grid
… Journal of Research and Reviews in …, 2012
... 1561 Summarization of Energy-Efficient Communication Protocols for Smart Grid Ayesha Afzaal, ... more ... 1561 Summarization of Energy-Efficient Communication Protocols for Smart Grid Ayesha Afzaal, Maria Saleemi, Mohsin Nazir, and Farhat Saleemi Department of Computer Science, Lahore College for Women University, Lahore, Pakistan Email: [email protected] ...
A partial-wave analysis of the (K+ K-[pi]-) system produced in [pi]-p--> K+ K-[pi]-p at 16 GeV/c
Nuclear Physics B, 1982
... FRENCH 4, SHP GEER6, P. GIRTLER, B. GHIDINI2, IS HUGHES5, JN JACKSON 6, JG LYNCH5, L. MANDELL... more ... FRENCH 4, SHP GEER6, P. GIRTLER, B. GHIDINI2, IS HUGHES5, JN JACKSON 6, JG LYNCH5, L. MANDELLI7, PW MINTO5, WA MITAROFF', K. MULLER3, G. OTTER, A. PALAN02 , L. PERINI 7, J. PINFOLD6, WH RANGE 6, JA RICHARDSON 6, G. RUDOLPH , F. SALEEMI5 ...
Wireless networks are one of the most essential components of the communication networks. In cont... more Wireless networks are one of the most essential components of the communication networks. In contrast to the wired networks, the inherent broadcast nature of wireless networks provides a breeding ground for both opportunities and challenges ranging from security to reliability. Moreover, energy is a fundamental design constraint in wireless networks. The boom of wireless network is closely coupled with the schemes that can reduce energy consumption. Network coding for the wireless networks is seen as a potential candidate scheme that can help overcome the energy and security challenges while providing significant benefits. This paper presents a basic model for formulating network coding problem in wireless setting. Since the optimal solution to wireless network coding is NP (nondeterministic polynomial-time)-hard, we intend to explore the impact of different parameters with random and non-random solutions. We present extensive simulation to show the strength of random network coding scheme in general wireless network scenarios. This study provide a comprehensive insight into the limits of wireless network coding.
ISAST Transactions on No. 1, Vol. 1, 2007 (ISSN 1797-1152) Computers and Software Engineering Reg... more ISAST Transactions on No. 1, Vol. 1, 2007 (ISSN 1797-1152) Computers and Software Engineering Regular Papers Marium Jalal Chaundry, Farhat Saleemi, M. Imran Shahid, and Fatima Jalal Chaudhry: A Comparison of Networking Features of Windows Vista, Free BSD, Sun ...
Synthesis and evaluation of factors affecting thein vitrobioactivity and antibacterial activity of bioactive glass ceramics
International Journal of Modern Physics B, 2016
In the present study, two novel silicate glass-ceramics having chemical composition 38SiO2–41CaO–... more In the present study, two novel silicate glass-ceramics having chemical composition 38SiO2–41CaO–6P2O5–([Formula: see text])Na2O–[Formula: see text]CaF2 ([Formula: see text], 0.43 mol%) were synthesized. These glass derivatives were subjected to stimulated body fluid for 24 days in SBF under static condition at [Formula: see text]C in order to evaluate the bioactive properties of specimens. The antibacterial activity of glass ceramics against three pathogenic bacteria was determined using the modified Kirby Bauer method. It was found that the antibacterial activity primarily depends on the dissolution rate; faster release of ions caused rapid increase in the pH of the solution. Antibacterial properties were found to be strongly affected by changes in the pH of supernatant. The in vitro bioactivity assays showed that both glass derivatives were capable of bonding with bone and secondly effectively inhibit bacteria. However, the glass ceramic without CaF2 (B2) showed high dissolution ...
Effect of Ti+4 on in vitro bioactivity and antibacterial activity of silicate glass-ceramics
Materials Science and Engineering: C, 2016
A novel glass-ceramic series in (48-x) SiO2-36 CaO-4 P2O5-12 Na2O-xTiO2 (where x=0, 3.5, 7, 10.5 ... more A novel glass-ceramic series in (48-x) SiO2-36 CaO-4 P2O5-12 Na2O-xTiO2 (where x=0, 3.5, 7, 10.5 and 14mol %) system was synthesized by crystallization of glass powders, obtained by melt quenching technique. The differential scanning calorimetric analysis (DSC) was used to study the non-isothermal crystallization kinetics of the as prepared glasses. The crystallization behaviour of glasses was analyzed under non-isothermal conditions, and qualitative phase analysis of glass-ceramics was made by X-ray diffraction. The in vitro bioactivity of synthesized glass-ceramics was studied in stimulated body fluid at 37°C under static condition for 24days. The formation of hydroxyl-carbonated apatite layer; evident of bioactivity of the material, was elucidated by XRD, FTIR, AAS, SEM and EDX analysis. The result showed that partial substitution of TiO2 with SiO2 negatively influenced bioactivity; it decreased with increase in concentration of TiO2. As Ti(+4) having stronger field strength as compared to Si(+4) so its replacement became the cause for reduction in degradation that in turn improved the chemical stability. The compressive strength was also enhanced with progress addition of TiO2 in the system. The antibacterial properties were examined against Staphylococcus Epidermidis. Strong antibacterial efficacy was observed with the addition of TiO2 in the system.
Structural and Optoelectrical Properties of ZnTe Thin Films Prepared by E-Beam Evaporation
Journal of Electronic Materials, 2016
ZnTe thin films have been prepared by an electron-beam evaporation technique on glass substrates,... more ZnTe thin films have been prepared by an electron-beam evaporation technique on glass substrates, changing the accelerating voltage and the substrate temperature at accelerating voltage of 2 kV. Structural analysis showed that all the films had cubic structure with preferential orientation along (111) direction, though (220) and (311) orientations were also present. The (111) peak intensity increased with increasing film thickness. The crystallite size increased with increasing film thickness. Conductivity measurements showed that the films were p-type. Films prepared at accelerating voltage of 2 kV exhibited minimum resistivity. Optical characterization indicated that both absorbing and transparent thin films can be achieved by using different deposition conditions. The optical bandgap value was found to vary with substrate temperature.
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