Computer Microprocessor "Heart of the computer" Does the "thinking"
Making Small Smaller An Example: Electronics-Microprocessors ibm.com macroscale microscale nanoscale
Nanofilms (making thin objects, controlling the thickness)
A monolayer NANOFILM (single layer of molecules) ~1 nm thick Langmuir film An example of a FILM This is an example of SELF-ASSEMBLY
Nanofilm by Electrodeposition V I Cu e - –> Cu (0) "reduction" CuSO 4 dissolved in water Cu (0) –> Cu e - "oxidation" anodecathode If using an inert Pt electrode: 2 H 2 O –> O 2 + 4H + + 4e - Working Electrode (WE) Counter Electrode (CE) ("electroplating")
A nanofilm method, Thermal Evaporation Vaporization or sublimation of a heated material onto a substrate in a vacuum chamber vacuum ~10 -7 torr sample source film vacuum pump QCM vapor resistive, e-beam, rf or laser heat source Pressure must be held low to prevent contamination! Au, Cr, Al, Ag, Cu, SiO, others There are many other thin film manufacturing techniques
Nanofilms (making thin objects)
A Few Nanostructures Made at UMass 100 nm dots 70 nm nanowires200 nm rings 12 nm pores14 nm dots 13 nm rings25 nm honeycomb 14 nm nanowires 18 nm pores 150 nm holes
Lithography (controlling width and depth, by using stencils, masks, & templates)
Lithography Nanoscience Rocks Nanoscience Rocks Nanoscience Rocks! (Using a stencil or mask)
Lithography: Basic concepts Some possible desired features narrow line narrow trench modified substrate Photolithography Electron-Beam Lithography X-ray Lithography Focused Ion-Beam Lithography Block Copolymer Lithography Nano Imprint Lithography Dip Pen Lithography Interference Lithography Contact Lithography Others
Photolithography for Deposition substrate process recipe spin on resist resist expose mask (reticle) develop deposit liftoff narrow line applyspinbake spin coating exposed unexposed "scission"
Lithography IBM Copper Wiring On a Computer Chip Patterned Several Times
Other Uses spin on resist resist expose mask develop etch lift off dopant ions (e.g., B +, P + ) after lift off Ion implantation substrate silicon silicon oxide Patterned Oxide narrow trench Etching
Positive and Negative Resists resist expose develop Positive Resist resist expose develop Negative Resist scission cross-linking deposit & liftoff exposed region results in presence of structure exposed region results in absence of structure (generally poorer resolution)
Several Types of Lithography contactproximityprojection lens high resolutionextends mask lifeenables "stepping"
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 sensitivity depth of focus purity of light source numerical aperture of lens minimum pitch
Resolution in Projection Lithography k 1 ~ (depends on materials, optics and conditions) is wavelength of light used NA ~ is the numerical aperture of the lens system Rayleigh diffraction criterion> 2b min = 0.61 /NA is part of the underlying reason With careful engineering, R ~ /2 can be achieved Contact Lithography z is resist thickness Down to 45 nm
Silicon crystal Polymer film Electron Beam Nanoscopic Mask ! Down to 10 nm
CORE CONCEPT FOR NANOFABRICATION Deposition Template Etching Mask Nanoporous Membrane Remove polymer block within cylinders (expose and develop) (physical or electrochemical) Down to 3 nm
Benefit: Sun is an unlimited source of electronic energy. Solar Cells Konarka
Electric Solar Cells Made from single-crystal silicon wafers (conventionally) cross-sectional view n-type silicon p-type silicon + - Sunlight Voltage load + - Current The load can be a lamp, an electric motor, a CD player, a toaster, etc wires
Nanostructured Solar Cells + - Sunlight Voltage load Current More interface area - More power!