Mg3N2-Ga nanoscale semiconductor–liquid metal heterojunctions homogeneously coated with very thin graphitic carbon nanotube (GCNT) layers are fabricated (see figure). Most of the junctions have a uniform diameter of ca. 100–200 nm. GCNTs coated on the nanowire junctions are only several nanometers thick. A convergent electron beam generated in a transmission electron microscope is demonstrated to be an effective tool for delicate manipulation of a junction.