Ultrasonic nanowelding technique was used to improve the field emission properties of carbon nanotube (CNT) cathodes. Two kinds of welding heads were used and the effects of the head on the emission properties were Studied. The results show that cathodes welded by Al(2)O(3) flat head demonstrate excellent field emission Properties with high emission current density and good current stability. The improved held emission performance is attributed to the reliable and low resistance contact between CNTs and metal substrates. Cathodes welded by steel matrix head show a lower turn-on electric field due to the protruding CNTs at the edge of the welded pits. (C) 2008 Elsevier B.V. All rights reserved.