Development of a laser-triggered film switch for nanosecond rectangular pulse generator.

A rectangular pulse generator plays an important role in the calibration of impulse measurement as well as the investigation into electromagnetic pulse effect. In addition, the characteristics of an output switch have a direct impact on the generator's output waveform. Following the basic requirements for the switch in a rectangular generator, this paper proposes a new type of laser-triggered film switch with a compact structure and high repeatability. The mechanical structure and operating mechanism of this switch have been elaborated. To verify the feasibility of this switch model, the irradiation experiments were carried out to study the interaction between the laser and the film, and the inductance of the switch has been estimated. Then, to test the characteristics of the switch, a Blumlein rectangular pulse generator based on this switch has been constructed. The experiment results show that the generator worked well in consecutive jobs and had a wild adjustable amplitude range from 2 kV to 10 kV, with a minimum rise-time of less than 1 ns. The effect of the laser loophole and the thickness of the film on the switch have also been investigated. Finally, the plasma developing process of the laser-triggered film switch has been discussed.

Balancing Catalytic Activity and Interface Energetics of Electrocatalyst-Coated Photoanodes for Photoelectrochemical Water Splitting.

For photoelectrochemical (PEC) water splitting, the interface interactions among semiconductors, electrocatalysts, and electrolytes affect the charge separation and catalysis in turn. Here, through the changing of the bath temperature, Co-based oxygen evolution catalysts (OEC) with different crystallinities were electrochemically deposited on Ti-doped Fe2O3 (Ti-Fe2O3) photoanodes. We found: (1) the OEC with low crystallinity is highly ion-permeable, decreasing the interactions between OEC and photoanode due to the intimate interaction between semiconductor and electrolyte; (2) the OEC with high crystallinity is nearly ion-impermeable, is beneficial to form a constant buried junction with semiconductor, and exhibits the low OEC catalytic activity; and (3) the OEC with moderate crystallinity is partially electrolyte-screened, thus contributing to the formation of ideal band bending underneath surface of semiconductor for charge separation and the highly electrocatalytic activity of OEC for lowering over-potentials of water oxidation. Our results demonstrate that to balance the water oxidation activity of OEC and OEC-semiconductor interface energetics is crucial for highly efficient solar energy conversion; in particular, the energy transducer is a semiconductor with a shallow or moderate valence-band level.