We present a search for the pair production of scalar top quarks (t~1), the lightest supersymmetric partners of the top quarks, in pp collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 fb-1} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino (?~). We investigate final states arising from t~1t~1?bbt?~?~ and t~1t~1?bbtt?~?~. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (mt~1,m?~) plane. Show Partial Abstract