I'm not really a "button guy", so didn't really have much to offer -- and didn't want to suggest an "ID" of a nickel just to be a smartazz.
I also have a Samsung Galaxy (S5). Decent camera, (decent phone too!) but like SteelHead, I much prefer to use a "real" camera whenever I can.
That said, photography is all about light. Use good light and the camera won't have to work as hard, even the S5.
For something small like a button, you really want to make sure the lighting is nice and even - ideally lighted from all sides.
It's important to remember that with light, the angle of incidence equals the angle of reflection.
If you light from above (i.e., the LED on the S5 phone), the light is just going to bounce back up into the lens and mess things up.
You want to position your light(s) so that their reflections are not in a direct line with the lens. (By the way, this is the same root cause for "red-eye" images of people!)
Side-lighting also helps with contrast.
There's more to it, (such as backing off a bit as SteelHead suggests), but getting the light right helps the focus; getting the focus right makes the image!
Wish I could help you out on the button...