Ashraf Eldakrouri | University of Alberta (original) (raw)

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Papers by Ashraf Eldakrouri

As the semiconductor industry pushes toward ever smaller chip feature sizes (< 100 nm), ever s... more As the semiconductor industry pushes toward ever smaller chip feature sizes (< 100 nm), ever shorter wavelengths are sought for the photolithographic process used in their fabrication. We investigated two plasma-based light sources for the generation of near-monochromatic vacuum ultraviolet atomic hydrogen (121.6 nm) and oxygen (130.6 nm) line emissions, (i) a variant of a dielectric barrier discharge and (ii)

IEEE Conference Record - Abstracts. 2002 IEEE International Conference on Plasma Science (Cat. No.02CH37340), 2002

... Laroussi, M.; Gupta, MC; El Dakroury, A.; Yan, J.; Becker, KH; Martus, K.; Old Dominion Univ.... more ... Laroussi, M.; Gupta, MC; El Dakroury, A.; Yan, J.; Becker, KH; Martus, K.; Old Dominion Univ., Norfolk, VA, USA. ... The hydrogen Lyman-α line at 121.6 nm was emitted via near-resonant energy transfer between neon excimers and H 2 , which leads to the dissociation of H 2 and ...

Modern Trends in Physics Research, 2013

A vacuum ultraviolet ͑VUV͒ light source based on a high-pressure cylindrical dielectric barrier d... more A vacuum ultraviolet ͑VUV͒ light source based on a high-pressure cylindrical dielectric barrier discharge ͑DBD͒ has been developed. Intense and spectrally clean Lyman-␣ line at 121.6 nm was obtained by operating a DBD discharge in neon with a small admixture of hydrogen. The spectrum, optical power, stability, and efficiency of the source were measured. The influence of the gas mixture and total gas pressure on the VUV intensity has been investigated. Maximum optical power of 3.2 W and spectral width Ͻ0.03 nm was achieved. Power stability of Ϯ2% for 100 h of operation has also been obtained. The newly developed Lyman-␣ line source at 121.6 nm appears very promising for advanced lithography and other applications.

In all previous works on the dielectric barrier discharge (DBD), the authors used two electrodes ... more In all previous works on the dielectric barrier discharge (DBD), the authors used two electrodes separated by one or more dielectric layers and a gas-filled gap between them. In this work a new DBD design is investigated, using ring electrodes (two or four) on the outside of a dielectric tube. The discharge inside the tube occurs as a result of the application of RF power (13.56 MHz). The VUV emission under high-pressure conditions for different gas mixtures is studied.

In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-... more In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-line at 636.23 nm utilizing the optical emission spectroscopy (OES) technique, taking into consideration the possibility of existence of self absorption. This method is standing on comparison of the Lorentzian FWHM and spectral line intensity of the unknown Stark broadening parameter line (Zn I-636.23 nm-in our case) to a well known Stark parameter line (e.g. Zn I-lines at 472.2, 481 and 468 nm) at a reference electron density of 2.7 × 10 17 cm −3 and temperature of 1 eV. We have utilized the emission spectral data acquired from well diagnosed plasma produced by the interaction of Nd: YAG laser at wavelength of 1064 nm with ZnO nanomaterial target in open air. The results indicates that the Stark broadening of the Zn I-line at 636.23 nm is centered at 5.06 ± 0.03 Å with a 25% uncertainty at the given reference plasma parameters. The knowledge of the Stark broadening parameter of the 636.23 nm line may be important in the diagnostics of the laser plasma experiments especially in the absence of the H α -line.

The elemental content of the superficial and inner enamel as well as that of dentin was analyzed ... more The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all the different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin. V C 2013 AIP Publishing LLC. [http://dx.

Breast cancer, or malignant breast neoplasm, is a type of cancer that originates from breast tiss... more Breast cancer, or malignant breast neoplasm, is a type of cancer that originates from breast tissue, most commonly from the inner lining of the milk ducts or the lobules that supply the ducts with milk. It is one of the most widespread diseases, especially in women. Thus far, large efforts have been towards the early diagnosis of cancer in general, and breast cancer specifically. Most of these techniques deal with malignant tissues without inducing or increasing pathological tissue changes or causing major side effects for the patient. This paper proposes a new technique for diagnosing the presence or occurrence of cancer and assessing its grade early, accurately, and safely. The presented technique depends on the interaction between the laser and the soft tissue in order to induce plasma, and allows us to classify the cancer by studying the difference in the intensity ratio of the trace elements in normal and malignant tissues. The results presented here are show that only four patients out of the total sample of 30 have erroneous trace elements and that this does not affect the overall decision. Hence, the performance of LIPS can be measured as 87%, while retaining 100% accuracy. Furthermore, LIPS technique is a simple and promising technique that is capable of diagnosing malignant cells and tissues.

In this article, we will report an experimental evidence of enhanced LIBS emission upon replacing... more In this article, we will report an experimental evidence of enhanced LIBS emission upon replacing a Bulk-Based ZnO target by the corresponding Nano-Based target. The plasma was initiated via interaction of a Nd:YAG laser at the fundamental wavelength with both targets in open air under the same experimental conditions. The measurements show an enhanced emission from the Zn I-lines at the wavelengths of 328. 26, 330.29, 334.55, 468.06, 472.2, 481.01, 636.38 nm. The measurements were repeated at different delay times in the range from 1 to 5 μs at constant irradiation level and fixed gate time of 1 μs. The average enhancement over the different Zn I-lines was found increases exponentially up to 8-fold with delay time. The electron density to each plasma was measured utilizing the H α -line appeared in the emitted spectra from each plasma and was found to give similar values. The electron temperatures were measured via Boltzmann plot method utilizing the relative intensities of the Zn I-lines and were found to give very close values. Moreover, the relative population density of the ground state of the zinc atoms (relative concentration) was measured spectroscopically utilizing the Boltzmann plot method and was found to increase in a very similar trend to that of enhancement. The results of the spectroscopic analysis conclude that these signal enhancements can be attributed to the higher concentration of neutral atoms in the Nano-Based material plasma with respect to the corresponding Bulk-based ZnO material.

As the semiconductor industry pushes toward ever smaller chip feature sizes (< 100 nm), ever s... more As the semiconductor industry pushes toward ever smaller chip feature sizes (< 100 nm), ever shorter wavelengths are sought for the photolithographic process used in their fabrication. We investigated two plasma-based light sources for the generation of near-monochromatic vacuum ultraviolet atomic hydrogen (121.6 nm) and oxygen (130.6 nm) line emissions, (i) a variant of a dielectric barrier discharge and (ii)

IEEE Conference Record - Abstracts. 2002 IEEE International Conference on Plasma Science (Cat. No.02CH37340), 2002

... Laroussi, M.; Gupta, MC; El Dakroury, A.; Yan, J.; Becker, KH; Martus, K.; Old Dominion Univ.... more ... Laroussi, M.; Gupta, MC; El Dakroury, A.; Yan, J.; Becker, KH; Martus, K.; Old Dominion Univ., Norfolk, VA, USA. ... The hydrogen Lyman-α line at 121.6 nm was emitted via near-resonant energy transfer between neon excimers and H 2 , which leads to the dissociation of H 2 and ...

Modern Trends in Physics Research, 2013

A vacuum ultraviolet ͑VUV͒ light source based on a high-pressure cylindrical dielectric barrier d... more A vacuum ultraviolet ͑VUV͒ light source based on a high-pressure cylindrical dielectric barrier discharge ͑DBD͒ has been developed. Intense and spectrally clean Lyman-␣ line at 121.6 nm was obtained by operating a DBD discharge in neon with a small admixture of hydrogen. The spectrum, optical power, stability, and efficiency of the source were measured. The influence of the gas mixture and total gas pressure on the VUV intensity has been investigated. Maximum optical power of 3.2 W and spectral width Ͻ0.03 nm was achieved. Power stability of Ϯ2% for 100 h of operation has also been obtained. The newly developed Lyman-␣ line source at 121.6 nm appears very promising for advanced lithography and other applications.

In all previous works on the dielectric barrier discharge (DBD), the authors used two electrodes ... more In all previous works on the dielectric barrier discharge (DBD), the authors used two electrodes separated by one or more dielectric layers and a gas-filled gap between them. In this work a new DBD design is investigated, using ring electrodes (two or four) on the outside of a dielectric tube. The discharge inside the tube occurs as a result of the application of RF power (13.56 MHz). The VUV emission under high-pressure conditions for different gas mixtures is studied.

In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-... more In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-line at 636.23 nm utilizing the optical emission spectroscopy (OES) technique, taking into consideration the possibility of existence of self absorption. This method is standing on comparison of the Lorentzian FWHM and spectral line intensity of the unknown Stark broadening parameter line (Zn I-636.23 nm-in our case) to a well known Stark parameter line (e.g. Zn I-lines at 472.2, 481 and 468 nm) at a reference electron density of 2.7 × 10 17 cm −3 and temperature of 1 eV. We have utilized the emission spectral data acquired from well diagnosed plasma produced by the interaction of Nd: YAG laser at wavelength of 1064 nm with ZnO nanomaterial target in open air. The results indicates that the Stark broadening of the Zn I-line at 636.23 nm is centered at 5.06 ± 0.03 Å with a 25% uncertainty at the given reference plasma parameters. The knowledge of the Stark broadening parameter of the 636.23 nm line may be important in the diagnostics of the laser plasma experiments especially in the absence of the H α -line.

The elemental content of the superficial and inner enamel as well as that of dentin was analyzed ... more The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all the different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin. V C 2013 AIP Publishing LLC. [http://dx.

Breast cancer, or malignant breast neoplasm, is a type of cancer that originates from breast tiss... more Breast cancer, or malignant breast neoplasm, is a type of cancer that originates from breast tissue, most commonly from the inner lining of the milk ducts or the lobules that supply the ducts with milk. It is one of the most widespread diseases, especially in women. Thus far, large efforts have been towards the early diagnosis of cancer in general, and breast cancer specifically. Most of these techniques deal with malignant tissues without inducing or increasing pathological tissue changes or causing major side effects for the patient. This paper proposes a new technique for diagnosing the presence or occurrence of cancer and assessing its grade early, accurately, and safely. The presented technique depends on the interaction between the laser and the soft tissue in order to induce plasma, and allows us to classify the cancer by studying the difference in the intensity ratio of the trace elements in normal and malignant tissues. The results presented here are show that only four patients out of the total sample of 30 have erroneous trace elements and that this does not affect the overall decision. Hence, the performance of LIPS can be measured as 87%, while retaining 100% accuracy. Furthermore, LIPS technique is a simple and promising technique that is capable of diagnosing malignant cells and tissues.

In this article, we will report an experimental evidence of enhanced LIBS emission upon replacing... more In this article, we will report an experimental evidence of enhanced LIBS emission upon replacing a Bulk-Based ZnO target by the corresponding Nano-Based target. The plasma was initiated via interaction of a Nd:YAG laser at the fundamental wavelength with both targets in open air under the same experimental conditions. The measurements show an enhanced emission from the Zn I-lines at the wavelengths of 328. 26, 330.29, 334.55, 468.06, 472.2, 481.01, 636.38 nm. The measurements were repeated at different delay times in the range from 1 to 5 μs at constant irradiation level and fixed gate time of 1 μs. The average enhancement over the different Zn I-lines was found increases exponentially up to 8-fold with delay time. The electron density to each plasma was measured utilizing the H α -line appeared in the emitted spectra from each plasma and was found to give similar values. The electron temperatures were measured via Boltzmann plot method utilizing the relative intensities of the Zn I-lines and were found to give very close values. Moreover, the relative population density of the ground state of the zinc atoms (relative concentration) was measured spectroscopically utilizing the Boltzmann plot method and was found to increase in a very similar trend to that of enhancement. The results of the spectroscopic analysis conclude that these signal enhancements can be attributed to the higher concentration of neutral atoms in the Nano-Based material plasma with respect to the corresponding Bulk-based ZnO material.