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Home > Fabrication and Characterization of Ii-Vi Semiconductor Thin Films and the Study of Post Doping Effects

Fabrication and Characterization of Ii-Vi Semiconductor Thin Films and the Study of Post Doping Effects

Thesis Info

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Author

Mahmood, Waqar

Program

PhD

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/778

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726182908

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Fabrication and Characterization of II-VI Semiconductor Thin Films and the Study of Post Doping Effects II-VI semiconductors have great importance in solar cell applications due to their excellent optical and electrical properties. This thesis is mainly concerned with the study of II-VI semiconductor thin films with a particular interest in their potential application in solar cells. A coating system based on close spaced sublimation (CSS) has been developed and thin films of zinc telluride (ZnTe), Zn and Te enriched ZnTe, cadmium sulfide (CdS) and cadmium zinc sulfide (CdZnS) were fabricated. CdS is transparent to electromagnetic radiations; in particular to the visible and infra-red regions and are highly resistive materials. This research work pertained to improve CdS thin films as window materials using close spaced sublimation technique. The optimization of deposition parameters including vacuum in the chamber, distance between source-substrate, source and substrate temperatures are all investigated. ZnTe has been used as a buffer layer between CdTe and the metal back contact in II-VI semiconductor solar cells due to its compatibility with p-type cadmium telluride (CdTe). The purpose of the buffer layer is to help CdTe form a good Ohmic contact with the metal back contact, however, ZnTe itself is highly resistive. The main goal is to reduce electrical resistivity of ZnTe for its use as buffer layer in the back contact. The resistivity of the ZnTe thin film is modified by doping with silver (Ag) and/or copper (Cu). The compositions of zinc (Zn) and tellurium (Te) in the enriched (Zn or Te) ZnTe thin film is also explored to lower the resistivity of ZnTe film, which has not been reported earlier using CSS technique. In all these processes, the structural, surface, electrical and optical properties are studied for strong correlation. Ion exchange process is adopted for Ag and Cu doping in as-deposited ZnTe thin films with subsequent annealing. CdS is a potential candidate for window layer due to its suitable and tunable energy band gap (2.42 eV). Effects of doping are investigated on the structural, electrical and optical properties of CdS thin films fabricated by the CSS technique. These properties of fabricated CdS thin films are found to be suitable for solar cell applications. To enhance band gap, CdS and Zn powder are mixed mechanically with different weight percentages to deposit thin films CZS fabricated by CSS technique that has not been documented earlier. The increased energy band gap for CZS is 2.57 eV, which has improved the window region.
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مولوی محبوب عالم

مولوی محبوب عالم
اس ماہ کے شذرات کا صفحہ وفات نامہ ہوا چاہتا ہے، مگر احسان فراموشی ہوگی اگر ملک کے سب سے بوڑھے صحیفۂ نگار مولوی محبوب عالم اڈیٹر پیسہ اخبار لاہور کا ماتم نہ کیا جائے، ۲۸؍ مئی کو انہوں نے اس دارِ فانی کو الوداع کہا، وہ اردو کے سب سے پہلے روزنامہ اخبار (پیسہ) کے اڈیٹر تھے، انہوں نے صرف اپنی محنت و کوشش سے سرمایہ حاصل کیا اور ملک میں تاریخ اور سیاحت ناموں کے پڑھنے کا ذوق پیدا کیا اور خود بھی یورپ اور ممالک اسلامیہ کے دوسفر کئے اور سیاحت نامے لکھے، مگر افسوس کہ اب ان کو وہ سفر پیش آیا جس کا سفرنامہ انسانوں کے ہاتھ نہیں، فرشتوں کے ہاتھ لکھتے ہیں، اس ان دیکھی منزل کے بوڑھے مسافر پر اﷲ تعالیٰ کی رحمت ہو۔
مرحوم نے ۷۴ برس کی عمر پائی۔ (سید سلیمان ندوی، جولائی ۱۹۳۳ء)
تصحیح: منشی محبوب عالم مرحوم کے تذکرہ میں یہ لکھا گیا ہے کہ وہ اردو کے پہلے روزانہ اخبار کے بانی اور اڈیٹر تھے، اس سے مراد مسلمانوں میں تھی، یعنی اردو کے پہلے اسلامی روزانہ اخبار کے وہ بانی اور اڈیٹر تھے، اردو میں منشی نولکشور لکھنو کا اودھ اخبار ان کے اخبار سے پہلے نکلا تھا اور اب تک نکل رہا ہے۔ (سید سلیمان ندوی، اگست ۱۹۳۳ء)

 

صحیح بخاری کی کتاب التفسیر کے فنی مباحث کا اختصاصی مطالعہ

The book of tafseer of Sahi Bukhari is most comprehensive book among the books of Hadith and on the basis of many features, it is considered superior to many other books of Hadith. Imam Bukhari annotates each surah one by one in his book of tafseer and constructs 114 chapters equal to the number of surah and these chapters carry 548 hadith of Zikr in which 465 are Mosool and remaining are mualaq and 100 hadith are not described before and remaining are repetitive. Imam Bukhari implements both style of description that is tafseer bil masaur and tafseer bil rai which proves the fact that Imam Bukhari supports the style of tafseer bil rai mehmood. Many Quranic information can be collected from book of tafseer for example: sabub nazool, makki & madni, ilmul qirat, ghareebul quran etc. The derivation of these features the book of tafseer of Sahi Bukhari is not the end but it is a starting point for new study.

Development of Information Security Threat Detection System Using Knowledge Discovery Techniques

Network Anomaly detection is rapidly growing field of information security due to its importance for protection of information networks. Being the first line of defense for network infrastructure, intrusion detection systems are expected to dynamically adapt with changing threat landscape. Deep learning is an evolving sub-discipline of machine learning which has delivered breakthroughs in different disciplines including natural language processing, computer vision and image processing to name a few. The successes of deep learning in aforementioned disciplines condone investigation of its application for solution of information security problems.This research aims at investigating deep learning approaches for anomaly-based intrusion detection system. In this study we propose, implement, evaluate and compare the use of Deep learning both as a refined representation learning mechanism as well as a new supervised classification mechanism for enhanced anomaly detection. Contributions of this research include Deep Supervised Learning and Deep Representation Learning for Network anomaly detection systems. For Deep Supervised Learning, anomaly detection models were developed by employing well-known deep neural network structures on both balanced and imbalanced datasets. For balanced Datasets we used four partitions of NSLKDD dataset while UNSWNB15 and ISCX2012 were employed as imbalanced datasets both of which contain 4.9% anomalous sample on average. For comparisons, conventional machine learning-based anomaly detection models were developed using well-known classification techniques. Both deep and conventional machine learning models were evaluated using standard model evaluation metrics. Results showed that DNN based anomaly detectors showed comparable or better results for detection of network anomalies. Deep Representation Learning involves using Deep learning to create efficient and effective Data representations from raw and high-dimensional network traffic data for developing anomaly detectors. Creating efficient representations from large volumes of network traffic to develop anomaly detection models is a time consuming and resource intensive task. Deep learning is proposed to automate feature extraction task in collaboration with learning subsystem to learn hierarchical representations which can be used to develop enhanced data driven anomaly detection systems. Four representation learning models were trained using well-known Deep Neural Network architectures to extract Deep representations from ISCX 2012 traffic flows. Each of these Deep representations is used to train anomaly detection models using twelve conventional Machine Learning algorithms to compare the performance of aforementioned deep representations with that of a human-engineered representation. The comparisons were performed using well known classification quality metrics. Results showed that Deep Representations perform comparable or better than human-engineered representations but require fraction of cost as compared to human-engineered representations due to inherent support of GPUs. Hyperparameter optimization of deep neural network used for current study is performed using Randomized Search. Experimental results of current research showed that Deep Neural Networks are an effective alternative for both representation learning and classification of network traffic for developing contemporary anomaly detection systems.