At the risk of being too simplistic to make silicon wafers, which is what you use to make computer chips and solar cells, you take a great big ingot of very pure silicon metal and then slice it very thinly.
The calculations indicate that the formation of longer chain hydrocarbons can happen in pure methane but the process is accelerated when the methane molecules are in contact with metal or carbon surfaces, e.g. diamond which act as catalysts for the methane-polymerisation to occur.