Best John C. Bean WeCanFigureThisOut.org Podcasts (2025)

1
Let's go inside an Intel 4004 microprocessor to see an individual transistor 0:13

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Do you know how Van de Graaff generators work? Let's turn it on. 0:14

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Turn it off and the charge stays on the dome. 0:03

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To make this transistor, first oxide then nitride layers are grown 0:11

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To understand what is going on, let's look inside. 0:11

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A shadow mask then exposes a photographic emulsion 0:12

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There is only a motor, powering a pulley, connected to a belt, almost touched by a copper comb. 0:21

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Exposed nitride is then etched away 0:07

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Oxygen reacts with the Si to grow more oxide 0:12

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The pulley is made of a special plastic. Let's fade away all but a few (exaggerated) plastic atoms. 0:15

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The pulley's plastic atoms will transfer electrons to the inside of the belt (it's just "static electricity"). 0:16

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By heating in silane, polycrystal Si is then grown 0:04

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A stripe is exposed in a second photographic emulsion 0:10

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The inside of the belt becomes more and more negative. 0:16

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Exposed polycrystal Si is etched away leaving the transistor gate 0:09

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But now let's go back and figure out what the bottom copper comb does. 0:09

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Phosphorus ions then penetrate thin oxide to create the source and drain 0:12

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Electrons jump from the comb trying to reach the increasingly positive pulley. 0:14

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Heating in oxygen grows an insulating coat on the gate 0:06

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But these electrons cannot penetrate the belt and are carried away. 0:11

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0:11

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This is an electron's worst nightmare as both sides of the belt are now negative! 0:19

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0:19

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A third photographic emulsion defines windows above the source and drain 0:10

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But as they reach the top, the outer electrons can jump onto a second comb ... 0:18

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Openings are then etched in the exposed oxide 0:07

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and then spread out on the metal dome. 0:18

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Metal is sprayed on to the surface 0:03

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0:03

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A fourth photographic emulsion is patterned 0:10

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0:10

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So the Van de Graaff uses the motor's work pushing electrons upward to build up "electrostatic energy." 0:30

8y ago0:30

0:30

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Unwanted metal is etched away completing the transistor 0:09

8y ago0:09

0:09

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And finally, here is the circuit symbol for the transistor 0:08

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0:08

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This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

8y ago0:33

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This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

8y ago0:33

0:33

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All of the scenes together 4:18

8y ago4:18

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All of the scenes together 3:09

8y ago3:09

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John C. Bean WeCanFigureThisOut.org Podcasts

1
Making an Integrated Circuit

John C. Bean - WeCanFigureThisOut.org

1
How Van de Graaff Generators Work

John C. Bean - WeCanFigureThisOut.org

1
Let's go inside an Intel 4004 microprocessor to see an individual transistor 0:13

1
Do you know how Van de Graaff generators work? Let's turn it on. 0:14

1
Turn it off and the charge stays on the dome. 0:03

1
To make this transistor, first oxide then nitride layers are grown 0:11

1
To understand what is going on, let's look inside. 0:11

1
A shadow mask then exposes a photographic emulsion 0:12

1
There is only a motor, powering a pulley, connected to a belt, almost touched by a copper comb. 0:21

1
Exposed nitride is then etched away 0:07

1
Oxygen reacts with the Si to grow more oxide 0:12

1
The pulley is made of a special plastic. Let's fade away all but a few (exaggerated) plastic atoms. 0:15

1
The pulley's plastic atoms will transfer electrons to the inside of the belt (it's just "static electricity"). 0:16

1
By heating in silane, polycrystal Si is then grown 0:04

1
A stripe is exposed in a second photographic emulsion 0:10

1
The inside of the belt becomes more and more negative. 0:16

1
Exposed polycrystal Si is etched away leaving the transistor gate 0:09

1
But now let's go back and figure out what the bottom copper comb does. 0:09

1
Phosphorus ions then penetrate thin oxide to create the source and drain 0:12

1
Electrons jump from the comb trying to reach the increasingly positive pulley. 0:14

1
Heating in oxygen grows an insulating coat on the gate 0:06

1
But these electrons cannot penetrate the belt and are carried away. 0:11

1
This is an electron's worst nightmare as both sides of the belt are now negative! 0:19

1
A third photographic emulsion defines windows above the source and drain 0:10

1
But as they reach the top, the outer electrons can jump onto a second comb ... 0:18

1
Openings are then etched in the exposed oxide 0:07

1
and then spread out on the metal dome. 0:18

1
Metal is sprayed on to the surface 0:03

1
A fourth photographic emulsion is patterned 0:10

1
So the Van de Graaff uses the motor's work pushing electrons upward to build up "electrostatic energy." 0:30

1
Unwanted metal is etched away completing the transistor 0:09

1
And finally, here is the circuit symbol for the transistor 0:08

1
This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

1
This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

1
All of the scenes together 4:18

1
All of the scenes together 3:09