4 ComputerMicroprocessor"Heart of the computer"Does the "thinking"
5 Making Small Smaller An Example: Electronics-Microprocessors microscalenanoscalemacroscaleibm.com
6 Nanofilms (making thin objects, controlling the thickness)
7 An example of a FILM A monolayer NANOFILM (single layer of molecules) ~1 nm thickLangmuir filmThis is an example of SELF-ASSEMBLY
8 Nanofilm by Electrodeposition ("electroplating")IVcathodeanodeCuSO4 dissolved in waterWorkingElectrode(WE)Counter(CE)Cu(0) –> Cu2+ + 2e-"oxidation"If using an inert Pt electrode:2 H2O –>O2 + 4H+ + 4e-"reduction"Cu2+ + 2e- –> Cu(0)
9 A nanofilm method, Thermal Evaporation sampleQCMVaporization or sublimation of a heated material onto a substrate in a vacuum chamberfilmvaporAu, Cr, Al, Ag, Cu, SiO, othersPressure must be held lowto prevent contamination!vacuum~10-7 torrsourceThere are many otherthin film manufacturingtechniquesresistive, e-beam, rf or laserheat sourcevacuumpump
17 Photolithography for Deposition process recipeapplyspinbakespin coatingsubstratespin on resistresistexposemask (reticle)exposedunexposed"scission"developnarrow linedepositliftoff
18 Lithography Patterned Several IBM Times Copper Wiring On a Computer Chip
19 Other Uses Patterned Oxide Ion implantation Etching narrow trench substratesiliconsilicon oxidePatternedOxideOther Usesspin on resistresistIon implantationdopant ions (e.g., B+, P+)Etchingexposemaskdevelopafteretchlift offnarrow trenchlift off
20 Positive and Negative Resists Positive ResistNegative Resistresistresistexposeexposescissioncross-linkingdevelopdevelopdeposit & liftoffexposed region results in presence of structureexposed region results in absence of structure(generally poorer resolution)
21 Several Types of Lithography lenscontactproximityprojectionhigh resolutionextends mask lifeenables "stepping"
22 Resolution Limit of PL How low can you go? minimum linewidth There are actually many contributing factors that limit the minimum linewidth:optical diffraction ()resist sensitivitydepth of focuspurity of light sourcenumerical aperture of lensminimum pitch
23 Resolution in Projection Lithography k1 ~ (depends on materials, optics and conditions)is wavelength of light usedNA ~ is the numerical aperture of the lens systemRayleigh diffraction criterion—> 2bmin = 0.61/NAis part of the underlying reasonWith careful engineering, R ~/2 can be achievedContact Lithographyz is resist thicknessDown to 45 nm
26 CORE CONCEPT FOR NANOFABRICATION Deposition Template Etching Mask NanoporousMembrane(physical orelectrochemical)Remove polymerblock within cylinders(expose and develop)Down to 3 nm
27 Solar Cells Benefit: Sun is an unlimited source of electronic energy. Konarka
28 Electric Solar Cells Sunlight - + + - Made from single-crystal silicon wafers (conventionally)Sunlightwires-cross-sectional view“load”n-type siliconVoltagep-type silicon++-CurrentThe load can be a lamp, an electric motor, a CD player, a toaster, etc
29 Nanostructured Solar Cells Sunlight-“load”Voltage+CurrentMore interface area - More power!
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