What makes you think we haven't started to hit physical limits of physics? A 4nm transistor is 7 atoms wide. Obviously, a one atom transistor is pretty much the absolute smallest possible, which would be about .5nm. Anything less than 7nm experiences quantum tunneling, which is going to really mess things up, and will get worse the smaller the size. [1] I imagine the interference between transistors will be fun...
Next, how exactly are you going to make these atom-sized objects in quantity? You can't be manually placing atoms. But lithography has a hard physical diffraction limit, forcing the use of higher frequency light. The higher the frequency, the greater the energy. Etching single-atom features will require hard x-rays, which we may not even have technology to generate. Even if we do, focusing x-rays is not trivial, as you can't just slap in a glass lens. Plus, the focal lengths may be rather long. And what kind of photoresist do you use? Hard x-rays are likely to blast pretty much anything, and the etching characteristics are probably not neat little troughs. How do you ensure you have your one atom stay put when everything around it is being blasted by high-energy x-rays?
I think the physical limits are looming pretty large.
Maybe but (and I could be way off I'm a programmer not a physicist) those limits are pretty much the limits on our current technology, it's a bit like saying "well we've reached the point of diminishing returns with this steam engine, that's it no more progress" and over in a shed somewhere else someone is inventing the AC electric motor.
I'm optimistic because I've seen "end of progress" reports on computing power since I was a kid in the 80's.
We've known for ages that Germanium and similar offer better characteristics than Silicon but the cost to improve silicon has stayed below the cost to retool for Germanium til now, if we do hit the limit at 5nm silicon then the cost equation changes and alternate materials become worth the investment.
They already use germanium in their manufacturing processes. It's not all germanium because there are challenges that would create. There are also benefits to mixing a different sized atoms into the same lattice to affect the speed in which the electrons travel so modern manufacturing often implants germanium atoms into the silicon lattices. I do agree that material improvements can change everything so the often spouted doom and gloom of stagnation is often unfounded.
Mostly agree with what you said, but just throwing this fun tidbit out there. The stated nm "size" of transistors are no longer accurate (and haven't been for some time). For example, when a company says it's manufacturing at 16nm or 14nm...that is the size in which the chip designs are drawn and planned, but the physical size dimensions are closer to 20nm. Same will be true when they go down to 10 and 7nm, it wont actually be a 7nm transistor in physical dimensions. And as far as lithography, right now they're mostly looking at "extreme" ultraviolet wavelengths but the problem is mass producing is not currently feasible with with how long it takes the photoresist to react. That being said things like quadruple patterning allow them to get pretty small with EUV wavelengths.
Next, how exactly are you going to make these atom-sized objects in quantity? You can't be manually placing atoms. But lithography has a hard physical diffraction limit, forcing the use of higher frequency light. The higher the frequency, the greater the energy. Etching single-atom features will require hard x-rays, which we may not even have technology to generate. Even if we do, focusing x-rays is not trivial, as you can't just slap in a glass lens. Plus, the focal lengths may be rather long. And what kind of photoresist do you use? Hard x-rays are likely to blast pretty much anything, and the etching characteristics are probably not neat little troughs. How do you ensure you have your one atom stay put when everything around it is being blasted by high-energy x-rays?
I think the physical limits are looming pretty large.
[1] https://en.m.wikipedia.org/wiki/5_nanometer