CE750 Captain experiences a Nose Door Open EICAS message shortly after takeoff with no vibration and elects to return. Upon inspection one latch is found undone.

Narrative

I was Captain on this trip; sitting in the left seat; First Officer was Pilot Flying from the right seat. Shortly after liftoff; [we] got an amber EICAS 'Nose Door Open-R.' The door did NOT open; there was no vibration or visible indication the door was open; just the EICAS message. We were conducting a reposition flight; no passengers on board. I determined the most prudent course of action was to immediately return and verify door was not properly latched. I advised Tower that we needed to return to the airport; wished to keep our flight plan/clearance active; and that we needed no other assistance. Controller instructed us to fly a right downwind; sequenced us behind a G4 on final; and we subsequently landed. Taxied to ramp; First Officer; got out; checked right avionics compartment door and found a latch had come undone. He secured the door; message cleared as I was configuring cockpit for takeoff. Subsequently taxied; took off; and completed the trip.Tough call.....just need to insure; after preflighting avionics compartments; latches are properly secured. This type event has happened to me in the past. I now physically strike the area around each latch to insure it is secure. Preflight for this hop was conducted by the First Officer. I suggested he assume the same practice in the future.