I prefer to stay in the same domain i.e. payment for a long period of time. There's a reason for this. First off, I will build a far better resume by showing that I am specializing in a niche (payment). Second, you will get to know almost everyone in the domain so you will have no issue in getting a job provided you're decent in what you do.
You can gather all your achievements and additional responsibilities that you have taken for the past year, and show it to your boss. It may help to also build a case by getting the market rate for your role. Bring it to your boss nicely and tell him that you like working here but you feel that you deserve a raise of x amount. Then let him respond.