X-ray radiation is widely used in medical and industrial applications. The basic design of the x-ray tube has not changed significantly in the last century. In this paper, we demonstrate that medical diagnostic x-ray radiation can be generated using a carbon nanotube (CNT) based field-emission cathode. The device can readily produce both continuous and pulsed x-ray with a programmable waveform and repetition rate. A total emission current of 28 mA was obtained from a 0.2 cm 2 area CNT cathode. The x-ray intensity is sufficient to image human extremity at 14 kVp and 180 mAs. Pulsed x-ray with a repetition rate greater than 100 kHz was readily achieved by programming the gate voltage. The CNT-based cold-cathode x-ray technology can potentially lead to portable and miniature x-ray sources for industrial and medical applications.

Uniform carbon nanotube films (see Figure) can be readily formed by electrophoretic deposition, as is presented in this communication. By varying deposition current and time, films with thicknesses in the range between several tens of nanometers and a few micrometers can be fabricated. The macroscopic nanotube films also show excellent electron field emission characteristics.

In this Account, we summarize some of our recent studies on the materials properties of the carbon nanotubes (CNTs). The focus is on single-wall carbon nanotubes (SWNTs). We describe experiments on synthesis of SWNTs with controlled molecular structures and assembly of functional macroscopic structures. In addition, we present results on the electron field emission properties of macroscopic CNT cathodes.