We have grown vertically well-aligned multiwalled carbon nanotubes (CNT) on a large area of cobalt-nickel (Co-Ni) co-deposited silicon oxide substrate by thermal chemical vapor deposition using C2H2 gas, at 950 degrees C. The diameter of CNTs is in the range of 50-120 nm and the length is about 130 mu m. The grown CNTs have a bamboo structure and closed tip with no catalytic particles inside. As the particle size of Co-Ni catalyst decreases, the vertical alignment is enhanced. The CNTs exhibits a low turn-on voltage of 0.8 V/mu m with an emission current density of 0.1 mu A cm(-2).