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WARNING: This post contains some spoilers for the anime/manga Dr.Stone.

As I'm watching Dr.Stone, I see Senku and the gang trying to make vacuum tubes for their circuits. The vacuum tube is an ancestor to the transistor. It is quite hard to make and is fragile because glass is used to enclose a vacuum and the metal (Tungsten) inside has to get quite hot. Transistors, however, can be tiny and easy to use. I know enough Physics and Electrical Engineering to know pretty well how transistors work but I'm not sure how they can be made.

The environment and circumstances in the world of Dr. Stone:

  • There's a single (genius) scientist from the modern world (everyone in the world got turned into stone and some got unpetrified after some thousands of years)
  • They can do metal work and smithing
  • They have a water wheel that can generate some electricity
  • They also have some batteries
  • They're making wires out of gold
  • A furnace is available but runs on either manual pumping or on the water wheel
  • Many common metals are available

Can they make transistors in such a world? If yes, about how small can the transistors be?

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    $\begingroup$ Unless you're interested in high speed switching, simple reed switch relays should be far more effective than hand made vacuum tubes. $\endgroup$ – nzaman Dec 11 '19 at 11:34
  • $\begingroup$ Transistor is semiconductor technology, if Dr Stone can find a stone that could allow electricity to flow when certain conditions are met at room temp without considering tunneling then by all means... $\endgroup$ – user6760 Dec 11 '19 at 11:56
  • $\begingroup$ You mean transistor as in logic gate? Bet that could be achieved by mechanical means and probably has. Logic gates don’t necessarily go hand in hand with electricity. Why not use water channels? Or metal cogs? $\endgroup$ – Darius Arcturus Dec 11 '19 at 13:18
  • $\begingroup$ They're trying to make cell phones (somehow) in the anime... $\endgroup$ – John Zhau Dec 11 '19 at 14:34
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    $\begingroup$ @JohnZhau most likely it will be some sort of walkie talkie, not an actual phone. $\endgroup$ – beppe9000 Dec 11 '19 at 18:03
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No, they can't.

To make a transistor you need to be able to smelt and refine to high levels of purity specific materials like Silicon, Germanium, Boron, Phosphorus and the like, and for some of them you even need a specific crystallographic set up.

While Silicon and Phosphorus are easily found in their bound state, refining them is beyond the capabilities of stone age, even your stone age + furnaces. Let alone controlling the crystallographic orientation of Silicon.

The Czochralski process is simply too complex for stone age,

High-purity, semiconductor-grade silicon (only a few parts per million of impurities) is melted in a crucible at 1,425 °C (2,597 °F; 1,698 K), usually made of quartz. Dopant impurity atoms such as boron or phosphorus can be added to the molten silicon in precise amounts to dope the silicon, thus changing it into p-type or n-type silicon, with different electronic properties. A precisely oriented rod-mounted seed crystal is dipped into the molten silicon. The seed crystal's rod is slowly pulled upwards and rotated simultaneously. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. Occurrence of unwanted instabilities in the melt can be avoided by investigating and visualizing the temperature and velocity fields during the crystal growth process. This process is normally performed in an inert atmosphere, such as argon, in an inert chamber, such as quartz.

like also zone refining

Zone melting (or zone refining or floating zone process or travelling melting zone) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot.

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