But it is usually governments that create a monopoly.
Very true.
Monopolies cannot exist in a free market.
I think they can. Each company has some quantity limits. If you cannot sell more, sell more expensive and discuss with the neighbor company that could be the competition to keep up the price and don't interfere with you so both will earn more with less effort.
The real problem is patents. Patents should not exist, at all, ever. If multiple people come to the same idea at once then patents are not at all fair, so the idea of patents is broken in its core.