Arrays of entangled carbon nanotube (CNT) columns on patterned n-Si substrates were fabricated by an atmospheric chemical vapor deposition with a ferrocene/xylene mixture. Preferential CNT growth in the opened Si windows of a 300 nm thick SiO2 layer was achieved by adjusting the parameters of the synthesis process. The resulting multiwalled CNT formed vertically aligned columns up to 50 mu m net height in four arrays of 10, 30, or 50 mu m patch diameter and 100 or 160 mu m pitch. The field emission (FE) properties of such structured cathodes were measured by a FE scanning microscope using tip anodes of adjusted size. Well-aligned FE from nearly 100% of the patches at electric field lower than 10 V/mu m was observed, but less pronounced FE occurred between the arrays too. High current capability of most patches up to milliamperes, suggesting multiple CNT emitters per patch, was achieved. Integral FE measurements in the diode configuration with luminescence screen and processing under N-2 and O-2 exposures of up to 3x10(-5) mbar demonstrated fairly homogeneous current distribution and long-term stability of the CNT cathodes.