As mentioned, the built-in mics aren't very good. However they'll at least do a better job image-wise if you place a folded piece of cardboard or something else in such a way that it acts like a baffle between the two microphones.
Get some better mics and a battery box or external preamp as soon as you are able. If you plan to use internal mics frequently, a different recorder would be a better option, but the original R-09 can make great recordings using an external preamp and mics. That will make a massive difference. Far, far, far, far, far, far more than recording at 96kHz instead of 44.1 or 48, which I doubt you would notice at all. Although it doesn't hurt other than doubling the storage space requirements, personally I don't bother recording at rates above 48kHz even when I pull out the fancy mics, preamps and recorders.