Clicker Question11: Solids and MaterialsBand Gaps in SemiconductorsSilicon & the ChipSilicon & the ChipSilicon & the ChipSilicon & the ChipPhotovoltaic CellsSilicon & the ChipSolar-to-Electrical Energy ConversionClickerQuantum DotsApplications of Quantum DotsApplications of Quantum DotsCement, Ceramics & GlassesCement, Ceramics & GlassesCement, Ceramics & GlassesCement, Ceramics & GlassesClicker QuestionA composite material is one whichA. Is either plastic or brittle and does not conduct heat or electricityB. Has a shiny surface and is a good conductor of heat or electrcityC. Occurs naturally and can be purified to use in manufacturing alloysD. Is brittle, nonmetallic, resistant to heat and chemically unreactiveE. Combines properties of metals, polymers, and ceramic to performed a special function11: Solids and Materials11.5 Types of Solids11.6 Crystalline Solids11.7 Network Solids11.8 Materials Science11.9 Metals, Semiconductors, and Insulators11.10 Silicon and the Chip11.11 Cement, Ceramics and GlassMonday, October 27, 2014Read: Sections 11.10 and 11.11 for MondayEnd of Chapter 11 Problems: 59, 61, 63, 65, 72, 75, 77, 84, 86, 88, 90, 92, 93, 108Monday, October 27, 2014Read: Sections 11.10 and 11.11 for MondayEnd of Chapter 11 Problems: 59, 61, 63, 65, 72, 75, 77, 84, 86, 88, 90, 92, 93, 108Band Gaps in SemiconductorsControl of the band gap size determines how much energy is needed to “turn on” a semiconductorSilicon & the ChipControlled addition of another element.Silicon & the ChipUltra-pure Si is prepared by zone refining.•Impurities are more soluble in Si(ℓ) than in Si(s). •A molten zone is moved through a sample.•Impurities move along in the liquefied portion.Silicon & the ChipA p-n junction.Charge carriers: holes (p-type) and e– (n-type)Silicon & the ChipSmart chips:•Can we diagnose a disease with a single chip?•Example: Systemic Lupus Erythematosus (SLE)•May provide in situ disease diagnosis and observation in real-timeNature Medcine. 2012; 18 (9): 1434Photovoltaic CellsBased on photosynthesisH2O + CO2 + solar energy → C(H2O) + O2chlorophyllhvCO2 e– AcceptorC(H2O)e–H2O e– DonorO2Silicon & the ChipA photovoltaic cell. nnppSolar-to-Electrical Energy ConversionnpEnergyCBCBVBVBnnppClickerWhat must silicon be doped with to make a p-type semiconductor?1. P2. As3. B needs to have a lower # of valence electrons than silicon 4. TeQuantum DotsNanocrystals made out of semiconducting materials•Exhibit properties between bulk semi conductors and individual molecules•Band gap is inversely related to sizeApplications of Quantum DotsBiology•Organic dyes are traditionally used•Quantum dots have begun to fill in the deficiencies of organic dyesApplications of Quantum DotsBiology•Tumor targeting•Potential toxic side effectsPhotovoltaic cells•Cheaper to manufacture•Can excite more than 1 electron per photonCement, Ceramics & GlassesAmorphous solids:Concrete = a mix of cement, sand and gravelCementTiny metal-oxide particles (CaO, SiO2, Al2O3 & SiO2). They crystallize irregularly when hydrated.Made by heating limestone, sand, clay and iron oxide High compressive, but low tensile strengthCement, Ceramics & GlassesCeramics – made from clay or other natural earths.Silicate ceramics – from clays. China clay (kaolin) is white and used for table china. Red clay contains Fe.Oxide ceramics – from metal oxides at high P and T. Used in high-T applications. Incredibly good insulatorNonoxide ceramics – include Si3N2, SiC, and BN. High P, T preparation. (all amorphous), hard and brittle,Cement, Ceramics & GlassesGlasses – optically transparent amorphous solids.Simplest: vitreous silica = SiO2 in a 3d-lattice.No long range order. (mp = around 1800°C) ultimately over a large range (b.c of amorphous)Soda lime glass, a SiO2, Na2O, CaO and MgO mix.More inert and easier to make (mp ~800°C).Cement, Ceramics & GlassesGlass can be colored: Substance ColorCalcium fluoride Milky whiteCobalt(II) oxide BlueCopper(I) oxide Red, green, blueGold (finely divided) Red, purple, blueIron(II) compounds GreenIron(III) compounds YellowManganese(IV) oxide VioletTin(IV) oxide OpaqueUranium compounds Yellow,