I mean it is estimated that there is roughly 10^57 atoms in our solar system bodies not including the sun. Thats all types of atoms (including argon, helium etc) -- but lets assume they are all of the most optimal material to make a 1 atom thick sphere at a distance from the sun that would not collapse or blow apart from gravitational forces or solar winds. You would run out of atoms before completing half of such a sphere. And to what end? The sphere would not do anything nor would you have a planet to power as you just used all of the available atoms to construct your partial sphere..