Temporal Characteristics of GaAs NEA and Alkali Metal Photocathodes

The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Based on the results, the time modulation transfer functions and temporal resolutions of the photocathodes are obtained. The results show that the response time and temporal resolution of alkali metal photocathode is in femitosecond order and those of GaAs NEA photocathode are in picosecond order.

Directing the photogenerated charge flow in a photocathodic metal protection system with single-domain ferroelectric PbTiO_(3)nanoplates

Photocathodic protection(PCP)is arguably an ideal alternative technology to the conventional electrochemical cathodic protection methods for corrosion mitigation of metallic infrastructure due to its eco-friendliness and low-energy-consumption,but the construction of highlyefficient PCP systems still remains challenging,caused primarily by the lack of driving force to guide the charge flow through the whole PCP photoanodes.Here,we tackle this key issue by equipping the PCP photoanode with ferroelectric single-domain PbTiO_(3)nanoplates,which can form a directional“macroscopic electric field”throughout the entire photoanode controllable by external polarization.The properly poled PCP photoanode allows the photogenerated electrons and holes to migrate in opposite directions,that is,electrons to the protected metal and holes to the photoanode/electrolyte interface,leading to largely suppressed charge annihilation and consequently a considerable boost in the overall solar energy conversion efficiency of the PCP system.The as-fabricated photoanode can not only supply sufficient photocurrent to 304 stainless steel to initiate cathodic protection,but also shift the metal potential to the corrosion-free range.Our findings provide a viable design strategy for future high-performance PCP systems based on ferroelectric nanomaterials with enhanced charge flow manipulation.

Characterisation of Photocathodes Based on Pb Thin Film Deposited by UV Pulsed Laser Ablation

This work deals with the deposition of lead （Pb） thin films by the UV pulsed laser ablation technique, for their further use as photocathode devices in superconducting radio frequency guns. Scanning electron microscopy and atomic force microscopy analyses were performed to study the morphological features of Pb thin films deposited on Si （100） and Nb substrates. The films showed a granular structure with a nearly fully covered surface only for that one deposited on Nb substrate. X-ray diffraction measurements indicate the growth of polycrystalline Pb thin films with a preferential orientation along （111） planes. Results of the photoemission performance of Pb thin film deposited on Nb substrate showed a very encouraging average value of quantum efficiency of 6 x 10-5 through a single-photon absorption process, promoting further studies in the realisation of Pb photocathodes by this technique.