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

Thesis Info

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External Link

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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در د کو در د نہیں میں نے دوا مان لیا

درد کو درد نہیں میں نے دوا مان لیا
زہر کو زہر نہیں میں نے شفا مان لیا

تو نے جو مجھ کو محبت میں سزائیں دی ہیں
میں نے ایک ایک سزا کو بھی جزا مان لیا

کفر اسلام میں انسان کو سجدہ کرنا
مذہبِ عشق نے اس کو بھی بجا مان لیا

ہے یہ کیا مجھ کو بتائیں گے فتاویٰ والے؟
سنتے ہیں قیس نے لیلیٰ کو خدا مان لیا

تیرے ہر درد کو سمجھا ہے عنایت تیری
تیرے ہر زخم کو تائب نے عطا مان لیا

Excellence of the Holy Qur’an in the Science of Human Behaviour, Psychology

The Science of Human Behavior (Psychology) governs every facet of our lifespan. The scope of psychology is so vast that it touches all major disciplines of medical science, social science, cultural studies and humanities. It does not just connect with subjects ranging from mathematics and biology to sociology and philosophy, but its methods and discoveries help other disciplines as well. Psychology influences legal affairs and national policies, yet it primarily deals with the cognition of human nature and its relevance to the respective domain. The article is aimed to elaborate that the comprehension of human behaviour in the illumination of the Holy Qur’an is an essential need in every aspect of life such as; educational activities, social and political institutions, ethical reflection or societal choice and the method of preaching.  

Genetics of Drought Tolerance Indices in Gossypium Hirsutum L.

The potential for breeding Gossypium hirsulum L. for drought stress tolerance was investigated in the present studies. For this purpose, a sample of 40 cotton varieties/lines was screened in greenhouse as well as in field condition. In glasshouse, drought stress was applied at 50%, 75% and 100% field capacity. The performance of theses genotypes was compared using data on shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, relative water content and excised leaf water loss through biplot analysis. In field condition, genotypes were screened in two irrigation regimes (normal and drought stress). Drought tolerance indices i.e. stress tolerance index, stress susceptible index, mean productivity, relative decrease in yield index, yield stability index, yield index were calculated on the basis of seed cotton yield. Ten highly drought tolerant (VH-144, IUB-212, MNH-886, VH-295, IR-3701, AA-802, NIAB-111, NS-121, FH-113, FH-142) and five drought sensitive (IR-3, CIM-443, FH-1000, MNH-147, S-12) genotypes/cultivars were selected on the basis of biplot analysis. In order to make F1 crosses in the glasshouse, drought tolerant genotypes were kept as lines and drought sensitive genotypes as testers by using line × tester mating design. Genetic material was field planted under two irrigation regimes (normal and drought stress). At maturity data was recorded for plant height, number of monopodial branches, number of sympodial branches, number of bolls per plant, boll weight, seed cotton yield, seed index, lint percentage (GOT %), fiber length, fiber strength, fiber fineness and fiber uniformity. The analysis of F1 and parental data revealed that there were preponderance of non-additive gene action for all the traits under normal and drought condition. The line VH-295 was a good general combiner followed by FH-142 among the traits. Among testers, CIM-443 appeared to be good general combiner for most of the traits. Comparison of crosses showed that FH-142 × IR-3 was the best combinations for plant height, boll weightseed cotton yield, yield index and relative drought index. The cross combinations NS-121 × CIM-443 and IUB-212 × CIM-443 exhibited good mid parent and better parent heterosis for seed cotton yield related traits under normal and drought conditions. The cross VH-144 × MNH-147 showed good mid parent heterosis for fiber length and fiber strength while the cross FH-113 × IR-3 showed good better parent heterosis for fiber strength and fiber fineness under normal and drought conditions. The cross combination IUB-212 × CIM-443 exhibited good mid parent and better parent heterosis effect for most of drought tolerance indices. The lines × testers’ interaction contributed more to expression of most of traits under normal and drought condition except fiber uniformity for tester under normal and drought condition and GOT% for tester under normal condition. The crosses VH-144 × S-12, FH-142 × IR-3 and NIAB-111 × IR-3 can be used in variety development program for drought pruned areas of Pakistan with high specific combining ability for most of traits under drought condition. Non additive gene action for most of traits suggests the possibility of using this material in the hybrid development programme in cotton.