Performance of a hybrid pyroelectric LiNbO3 and TiO2 nanotubes X-ray source

Effects of crystal length and temperature on performance and degradation properties of LiNbO3∕TiO2 pyroelectric∕nanotube X-ray source were studied. Such hybrid LiNbO3∕TiO2 X-ray source was fabricated by bonding electrochemically grown TiO2 nanotubes on -z face of pyroelectric LiNbO3 crystal. In particular, it was found that maximum accelerated electron energy increased with height for both pure and hybrid LiNbO3∕TiO2 system for both heating and cooling cycles. For example, for 2 cm long hybrid structure the resulting maximum energy during heating cycle was 97 keV as compared to 74 keV for 1 cm long structure. The maximum energy for the pure sample without nanotubes increased from 45 keV to 66 keV. Increased endpoint energy of nanotube based X-ray source is attributed to electric field amplification on nanotube tips increasing the efficiency of residual gas ionization, leading to improved charge carrier transmission efficiency. The degradation properties were studied by performing multiple thermal cycles and results revealed that cluster nanotips erode over time. After 20 cycles they become flat as was evidenced from scanning electron microscope analysis.