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The Hang Seng Index (HSI) is a freefloat-adjusted market-capitalization-weighted stock-market index in Hong Kong. It is used to record and monitor daily changes of the largest companies of the Hong Kong stock market and is the main indicator of ...
- Physics of Semiconductors
- Early History of Semiconductors
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- Further Reading
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Variable electrical conductivity
Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, and semiconductors have their valence bands filled, preventing the entire flow of new electrons. Several developed techniques allow semiconducting materials to behave like conducting materials, such as doping or gating. These modifications have two outcomes: n-type and p-type. These refer to the excess or shortage of electrons, respectively. An unbalanced number of electrons would cause...
Heterojunctions occur when two differently doped semiconducting materials are joined together. For example, a configuration could consist of p-doped and n-doped germanium. This results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until an equilibrium is reached by a process called recombination, which causes the...
A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion. Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes. Such disruptions can occur as a result of a temperature difference or photons, which can enter the system and create electrons...
A large number of elements and compounds have semiconducting properties, including: 1. Certain pure elements are found in Group 14 of the periodic table; the most commercially important of these elements are silicon and germanium. Silicon and germanium are used here effectively because they have 4 valence electrons in their outermost shell which gives them the ability to gain or lose electrons equally at the same time. 2. Binary compounds, particularly between elements in Groups 13 and 15, such as gallium arsenide, Groups 12 and 16, groups 14 and 16, and between different group 14 elements, e.g. silicon carbide. 3. Certain ternary compounds, oxides, and alloys. 4. Organic semiconductors, made of organic compounds. 5. Semiconducting Metal-organic frameworks. The most common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of...
Energy bands and electrical conduction
Semiconductors are defined by their unique electric conductive behavior, somewhere between that of a conductor and an insulator. The differences between these materials can be understood in terms of the quantum states for electrons, each of which may contain zero or one electron (by the Pauli exclusion principle). These states are associated with the electronic band structure of the material. Electrical conductivity arises due to the presence of electrons in states that are delocalized (exten...
The partial filling of the states at the bottom of the conduction band can be understood as adding electrons to that band. The electrons do not stay indefinitely (due to the natural thermal recombination) but they can move around for some time. The actual concentration of electrons is typically very dilute, and so (unlike in metals) it is possible to think of the electrons in the conduction band of a semiconductor as a sort of classical ideal gas, where the electrons fly around freely without...
The conductivity of semiconductors may easily be modified by introducing impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is known as doping. The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are referred to as extrinsic.By adding impurity to the pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions. A 1 cm3 specim...
The history of the understanding of semiconductors begins with experiments on the electrical properties of materials. The properties of the time-temperature coefficient of resistance, rectification, and light-sensitivity were observed starting in the early 19th century. Thomas Johann Seebeck was the first to notice an effect due to semiconductors, in 1821. In 1833, Michael Faraday reported that the resistance of specimens of silver sulfide decreases, when they are heated. This is contrary to the behavior of metallic substances such as copper. In 1839, Alexandre Edmond Becquerel reported observation of a voltage between a solid and a liquid electrolyte, when struck by light, the photovoltaic effect. In 1873, Willoughby Smith observed that selenium resistors exhibit decreasing resistance, when light falls on them. In 1874, Karl Ferdinand Braun observed conduction and rectification in metallic sulfides, although this effect had been discovered much earlier by Peter Munck af Rosenschold...A. A. Balandin & K. L. Wang (2006). Handbook of Semiconductor Nanostructures and Nanodevices (5-Volume Set). American Scientific Publishers. ISBN 978-1-58883-073-9.Sze, Simon M. (1981). Physics of Semiconductor Devices (2nd ed.). John Wiley and Sons (WIE). ISBN 978-0-471-05661-4.Turley, Jim (2002). The Essential Guide to Semiconductors. Prentice Hall PTR. ISBN 978-0-13-046404-0.Yu, Peter Y.; Cardona, Manuel (2004). Fundamentals of Semiconductors : Physics and Materials Properties. Springer. ISBN 978-3-540-41323-3.
Machine capable of carrying out a complex series of actions automatically. This article is about mechanical robots. For software agents, see Bot. For other uses of the term, see Robot (disambiguation). ASIMO (2000) at the Expo 2005. Articulated ...
The Science Citation Index (SCI) is a citation index originally produced by the Institute for Scientific Information (ISI) and created by Eugene Garfield.It was officially launched in 1964 and is now owned by Clarivate Analytics (previously the ...
Coca-Cola, or Coke, is a carbonated soft drink manufactured by The Coca-Cola Company.Originally marketed as a temperance drink and intended as a patent medicine, it was invented in the late 19th century by John Stith Pemberton and was bought out ...
Science fiction, whose roots go back to ancient times, is related to fantasy, horror, and superhero fiction, and contains many subgenres. Its exact definition has long been disputed among authors, critics, scholars, and readers. Science fiction ...
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Australian universities commonly have coursework or research-based Master of Science courses for graduate students. They typically run for 1–2 years full-time, with varying amounts of research involved.
All Bangladeshi private and public universities have Master of Science courses as postgraduate degree. These include most of the major state-owned colleges. A number of private colleges also do offer MS degrees. After passing Bachelor of Science, any student becomes eligible to study in this discipline.
In Canada, Master of Science (MSc) degrees may be entirely course-based, entirely research-based or (more typically) a mixture. Master's programs typically take one to three years to complete and the completion of a scientific thesisis often required. Admission to a master's program is contingent upon holding a four-year university bachelor's degree. Some universities require a master's degree in order to progress to a doctoral program (PhD).
Commonly the Chilean universities have used "Magíster" for a master degree, but other than that is similar to the rest of South America.
Like all EU member states, the Republic of Cyprus follow the Bologna Process. Universities in Cyprus have used either "Magíster Scientiae or Artium" or Master of Art/Science for a master's degree with 90 to 120 ECTS and duration of studies between 1, 2 and 5 years.
Like all EU member states, the Czech Republic and Slovakia follow the Bologna Process. The Czech Republic and Slovakia are using two master's degree systems. Both award a title of Mgr. or Ing. to be used before the name.The older system requires a 5-year program. The new system takes only 2 years but requires a previously completed 3-year bachelor program (a Bc.title). It is required to write a thesis (in both master and bachelor program) and also to pass final exams. It is mostly the case that the final exams cover the main study areas of the whole study program, i.e. a student is required to prove his/her knowledge in many subjects he attended during the 2 resp. 3 years.
The Master of Science (M.Sc.) is an academic degree for post-graduate candidates or researchers, it usually takes from 4 to 7 years after passing the Bachelor of Science (B.Sc.) degree. Master programs are awarded in many sciences in the Egyptian Universities. A completion of the degree requires finishing a pre-master studies followed by a scientific thesis or research. All M.Sc. degree holders are allowable to take a step forward in the academic track to get the PhDdegree.
Like all EU member states, Finland follows the Bologna Process. The Master of Science (M.Sc.) academic degree usually follows the Bachelor of Science (B.Sc.) studies which typically last five years. For the completion of both the bachelor and the master studies the student must accumulate a total of 300 ECTS credits, thus most Masters programs are two-year programs with 120 credits. The completion of a scientific thesisis required.
Like all EU member states, Germany follows the Bologna Process. The Master of Science (M.Sc.) academic degree replaces the once common Diplom or Magister programs that typically lasted four to five years. It is awarded in science-related studies with a high percentage of mathematics. For the completion the student must accumulate 300 ECTS Credits, thus most Masters programs are two-year programs with 120 credits. The completion of a scientific thesisis required.
In Slavic countries in European southeast (particularly former Yugoslavian republics), the education system was largely based on the German university system (largely due to the presence and influence of the Austria-Hungary Empire in the region). Prior to the implementation of the Bologna Process, academic university studies comprised a 4-5 year long graduate Diplom program, which could have been followed by a 2-4 year long Magister program and then later with 2-4 year long Doctoral studies. After the Bologna Process implementation, again based on the German implementation, Diplom titles and programs were replaced by the M.Sc. and M.A. programs (depending on the field of study). The studies are structured such that a Master program lasts long enough for the student to accumulate a total of 300 ECTS credits, so its duration would depend on a number of credits acquired during the Bachelor studies. Pre-Bologna Magister programs were abandoned - after earning an M.Sc/M.A. degree and sat...
Turkey is a regional power, and a newly industrialized and developing country, with a geopolitically strategic location. Its economy, which is classified among the emerging and growth-leading economies, is the twentieth-largest in the world by ...