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LED's   rely  on a series of layers that form "quantum wells" that trap electrons and ensure efficient light generation. These layers are 3 nm or 10  atoms  thick. These are deposited over over a 150 mm wafer. If a golf ball represents an atom, this is equivalent to  layer 1 ft thick over the US.  

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IC's remarkably small transistors with features 100 atoms (30nm) wide - over a 10 tera  of transistors (10^ 13) made simultaneously  on a single wafer with next to no defects, larger than 30 atoms. A brain in another 50 years.  Scale is brain numbing -  if a golf ball  is an atom, a feature is a street (10 yds) wide and  a wafer covers the earth (7000 miles). A typical chip is a city from Austin to Dallas 200x200 miles.   15 pattern layers of roads are needed to connect all the houses without wasting space. To yield a working device with 30 layers, each layer must be almost perfect. A wafer has zero defects of 30 atoms, or the earth covered with roads and every road is perfect !. 


FPD have a different challenge, we like large displays. To make your TV cost competitive, they are made at least 6 at time, so for a 85" diagonal TV, this means a sheet of glass around 3 meters on a side ( about 2 humans high and wide). Each pixel in a display requires a transistor, each TV has large 100M (10^8) transistors. There can be no (as in zero) defects larger than the wavelength of light.  What you get is a cinema in your home, if you sit   2x screen width away. 12 ft away from 6 ft wide (85" diagonal) screen.


If the smallest feature in a display (1 um) is represented by a street (10 yds) then the glass sheet is 20,000 Miles on a side. and a pixel is 3 miles on a side. 


Solar cells very large area diodes to collect limited energy.  beneficiaries of all the process developments - remarkably cheap - Cost must be less than $500 m-2, $10 for each 6x6" cell.  The cells are 80% of theoretical max, but only 25% of the suns energy is trapped because the band gap in silicon only collects a single photon for all wavelengths shorter that 1um. That means that all the  high energy short wavelengths in the sun, only contribute the energy of a 1 um photon.   


Cameras - diode light collectors linked to storage memory cell, and are remarkable sensitive. Recently I was able to  get an estimate of the efficiency of a camera from a clear image of Rhea (Saturn moon) at ISO 3200 exp 1 sec.  The Sun has an apparent magnitude - 27, Rhea is magnitude 10 so  relative to sun, rhea is 4 E-15 less intense. The Sun produces 1000 W m-2, or 250 W m-2 seen by Si detector. Therefore, Rhea produces 1E-12 watts m-2 seen by Si detector. Incident on a 70 mm lens aperture with area 0.006 m-2 with a 1 sec exposure = 6e-15 joules.  A 2 eV photon is worth 4e-19 joules, so the number of photons on 1 pixel in the camera in 1 sec = 6E-15/4E-19 = 1E4  = 10,000 photons gets an image. My Sony 7aS full frame can just function at  ISO 400K, so it is imaging at 100 photons.  

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