conductors insulators and semiconductors wikipedia

... Inc. 3 StimulatedEmissionandOptical GaininSemiconductors Thischapterpresentsthebasictheoryandcharacteristicsofstimulated emissionandopticalamplificationgaininsemiconductors.Theformeristhe mostimportantprinciplethatenablessemiconductorlaserstobeimplemented, andthelatteristhemostimportantparameterforanalysisofthelaser performances.First,stimulatedemissioninsemiconductorsisexplained ,and thenquantumtheoryanalysisandstatisticanalysisusingthedensitymatrix oftheopticalamplificationgainaregiven.Stimulatedemissionandoptical gaininsemiconductorquantumwellstructureswillbepresentedinthenext chapter. 3.1BANDSTRUCTUREOFSEMICONDUCTORSAND STIMULATEDEMISSION 3.1.1BandStructureofDirect-TransitionBandgap Semiconductors Semiconductorlasersutilizetheinterbandopticaltransitionsofcarriersina semiconductorhavingadirect-transitionbandgap.Asiswellknowninthe electrontheoryofsolids[1],thewavefunctionofanelectronofwavevector k(momentumhh k )inanidealsemiconductorcrystalcanbewrittenasa Blochfunction j ... Dekker, Inc. 3 StimulatedEmissionandOptical GaininSemiconductors Thischapterpresentsthebasictheoryandcharacteristicsofstimulated emissionandopticalamplificationgaininsemiconductors.Theformeristhe mostimportantprinciplethatenablessemiconductorlaserstobeimplemented, andthelatteristhemostimportantparameterforanalysisofthelaser performances.First,stimulatedemissioninsemiconductorsisexplained ,and thenquantumtheoryanalysisandstatisticanalysisusingthedensitymatrix oftheopticalamplificationgainaregiven.Stimulatedemissionandoptical gaininsemiconductorquantumwellstructureswillbepresentedinthenext chapter. 3.1BANDSTRUCTUREOFSEMICONDUCTORSAND STIMULATEDEMISSION 3.1.1BandStructureofDirect-TransitionBandgap Semiconductors Semiconductorlasersutilizetheinterbandopticaltransitionsofcarriersina semiconductorhavingadirect-transitionbandgap.Asiswellknowninthe electrontheoryofsolids[1],thewavefunctionofanelectronofwavevector k(momentumhh k )inanidealsemiconductorcrystalcanbewrittenasa Blochfunction j ... Inc. ThematrixelementjMj 2 forthetransitionswherewavevectorconservation doesnotnecessarilyholdisgivenbytheproductofEq.(3.29)andEq.(3.34). Equation(3.34)indicatesthatjMj 2 islargeintheregionofkwherea 2 k 2 issmall. AlthoughEq.(3.34)iseffectivefortransitionsbetweenthebandtail andaextendedband,itdoesnotapplyfortransitionsbetweenparabolic bandswithlargerenergiesandthosebetweenbandtails.Tosolvethe difficulty,Sternexpressedeachconduction-bandelectronandeachvalence- bandelectronintheformofEqs.(3.30 )and( 3.31).Thevaluesofawere determinedbyfittingtheeffectiveenergyreductionduetothelocalizationto theeffectiveenergyreductioncalculatedfromthedensityofstatesinthe GHLBTmodel.ThevalueofjM env j 2 wascalculatedbyusingthesevaluesin Eq.(3.33)andaveragingoverallkdirectionsandthelocalizationsitesr i [11].Theresultiswrittenas jM env j 2 ¼ 64pb 3 ðt 4 Àq 4 Þ À5 ½ðb 4 À5b 2 B 2 þ5B 4 Þð3t 4 þq 4 Þðt 4 Àq 4 Þ 2 þ8b 2 B 2 t 2 ð3b 2 À10B 2 Þðt 8 Àq 8 Þ þ16b 4 B 4 ð5t 8 þ10t 4 q 4 þq 8 Þð3:35Þ B 2 ¼ 1 a c a v ;b¼ 1 a c þ 1 a v ;t 2 ¼b 2 þk 2 c þk 2 v ;q 2 ¼2k c k v wherek c andk v arethewavenumbersofvalence-bandandconduction- bandelectronswiththeeffectiveenergyreductiontakenintoaccount.The matrixelementjMj 2 ¼jM(E 1 ,E 2 )j 2 ¼jM B j 2 jM env j 2 usingthisjM env j 2 is calledtheSternenergy-dependentmatrixelement(SME). Figure3.6showsanexampleofjM env j 2 calculated...

Ngày tải lên: 23/10/2013, 20:15

... approach cov- ers the entire Wikipedia and thus as many domains as are in Wikipedia. 7 Conclusions We have described a hedge detection system based on word frequency measures and syntactic pat- terns. ... articles containing the string {{weasel with 328 weasel 2 http://en .wikipedia. org/wiki/ Wikipedia: Avoid_weasel_words 3 http://download .wikipedia. org/ S M C K 0.45 0.71 0.6 S 0.78 0.6 M 0.8 Table 1: ... Linguistics, 22(2):249–254. Hyland, Ken (1998). Hedging in scientific research articles. Amsterdam, The Netherlands: John Benjamins. Lakoff, George (1973). Hedges: A study in meaning criteria and the logic of...

Ngày tải lên: 20/02/2014, 09:20

... NER models learned from Wikipedia- derived and gold-standard data. Our results are given as micro-averaged precision, recall and F - scores both in terms of MUC-style and CoNLL-style (exact-match) ... 2009. c 2009 Association for Computational Linguistics Analysing Wikipedia and Gold-Standard Corpora for NER Training Joel Nothman and Tara Murphy and James R. Curran School of Information Technologies University ... the gold-standard corpora and our new Wikipedia- derived training data, we eval- uate the usefulness of the latter and explore the nature of the training corpus as a variable in NER. Our Wikipedia- derived...

Ngày tải lên: 22/02/2014, 02:20

... tsnl Synthesis and Application of Nanosize Semiconductors for Photoxidation of Toxic Organic Chemicals J.P. Wilcoxon, Nanostructures and Advanced Materials Chemistry Sandia National Laboratories Albuquerque, ... Photooxidation) •Photocatalysis using UV light and nanosize TiO 2 and SnO 2 . •Photocatalysis using visible light and MoS 2 nanoclusters.  Acknowledgement: Div. Of Materials Science and Engineering, Office of Science, ... Science/Environmental Research (ER/ES) Program. tsnl Light Absorbance and Redox Potentials- -1.0 0.0 1.0 2.0 3.0 Redox Potentials of Various Semiconductors at pH 7 Potental vs. NHE H 2 O/OH . potential TiO 2 MoS 2 (bulk) MoS 2 (d=4.5...

Ngày tải lên: 14/03/2014, 20:20

... to Wikipedia task (2007). They experimented with two methods: (a) the lexical overlap between the Wikipedia page of the candidate disambiguations and the context of the ambiguous mention, and ... between Wikipedia titles. We are aware of two previous methods for estimating the relatedness between two Wikipedia concepts: (Strube and Ponzetto, 2006), which uses category overlap, and (Milne and ... USA. ACM. David Milne and Ian H. Witten. 2008a. An effec- tive, low-cost measure of semantic relatedness ob- tained from wikipedia links. In In the Wikipedia and AI Workshop of AAAI. David Milne and Ian H....

Ngày tải lên: 17/03/2014, 00:20

... twentieth century. Semiconductors for Micro and Nanotechnology— An Introduction for Engineers Jan G. Korvink and Andreas Greiner Crystal Structure Semiconductors for Micro and Nanosystem Technology ... Definitions and Acronyms Semiconductors for Micro and Nanosystem Technology 19 1.2 Popular Definitions and Acronyms The microelectronic and microsystem world is replete with terminology and acronyms. ... almost have metal-like SiO 2 Semiconductors for Micro and Nanotechnology— An Introduction for Engineers Observed Lattice Property Data Semiconductors for Micro and Nanosystem Technology 35 Silicon...

Ngày tải lên: 17/03/2014, 14:59

... sentences based on Wikipedia metadata We followed the approach of Richman and Schone (2008) to derive named entity annotations of both English and foreign phrases in Wikipedia, using Wikipedia metadata. ... foreign languages: Korean and Bulgarian. The English and foreign language sentences that comprise our training and test data are extracted from Wikipedia (http://www .wikipedia. org). Cur- rently ... tagger. Note that these English candidate en- tities can be overlapping and inconsistent without harming the model. We link foreign candidate seg- ments with English candidate entities based on the projection...

Ngày tải lên: 23/03/2014, 14:20

... (54) \Ga:As t e+ k 'Ga-As 16 Electrochemistry of Semiconductors and Electronics 4.0 COMPOUND SEMICONDUCTORS Compound semiconductors can be chosen to match their optoelectronic properties ... difference in the dissolution behavior of metals and semiconductors lies in the concentration and type of charges responsible for surface reactions. In semiconductors, the concentration of charge carriers ... involving semiconductors and/ or electronics mentioned in this publication should satisfy himself as to such suitability, and that he can meet all applicable safety and health standards. We...

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Ngày tải lên: 13/05/2014, 09:08

... band and the bottom of the conduction band there is an energy gap, later called the bandgap (see Chap. 6). Fig. 2.5. Schematic of the origin of valence and conduction band from the atomic s and ... bonding and (b,d) antibinding sym- metric (a,b) and nonsymmetric (c,d)sp 3 orbitals 2.2.3 sp 2 Bond Organic semiconductors (see Chap. 16) are made up from carbon compounds. While for inorganic semiconductors ... OpticalProperties 353 14.4 Piezoelectricity 353 15 Magnetic Semiconductors 359 15.1 Introduction 359 15.2 Magnetic Semiconductors 359 15.3 Diluted Magnetic Semiconductors 361 15.4 Spintronics 365 15.4.1 SpinTransistor...

Ngày tải lên: 04/06/2014, 14:33

... Conductive Zinc Oxide Basics and Applications in Thin Film Solar Cells Editors: K. Ellmer, A. Klein, and B. Rech 105 Dilute III-V Nitride Semiconductors and Material Systems Physics and Technology Editor:A.Erol 106 ... Depla and S. Mahieu 110 The Physics of Organic Superconductors and Conductors Editor:A.Lebed 111 Molecular Catalysts for Energy Conversion Editors: T. Okada and M. Kaneko 112 Atomistic and Continuum ... Heywang, K. Lubitz, andW.Wersing 115 Lithium Niobate Defects, Photorefraction and Ferroelectric Switching ByT.VolkandM.W ¨ ohlecke 116 Einstein Relation in Compound Semiconductors and Their Nanostructures By...

Ngày tải lên: 04/06/2014, 14:44

... larger in size and thus ‘closer’ to bulk form than the 46.3-nm film. Also, Figures 9 and 10 show bulk and thin film values of γ as a function of temperature. By comparing Figures 9a and 10a, it ... increases. To help understand these relationships, a model is presented, and equations are obtained to help understand the mechanisms responsible for these properties and to give insight into ... J: Handbook of Modern Sensors: Physics, Designs, and Applications. New York: Springer-Verlag; 2004. 25. Lacy F: Evaluating the resistivity-temperature relationship for RTDs and other conductors. ...

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