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This paper presents a diamond gammavoltaic cell—a solid-state device that converts gamma radiation into electricity—with a novel design and promising capabilities. Gammavoltaics pose a unique challenge among radiovoltaics due to the highly penetrating nature of gamma rays. To adapt existing radiovoltaic and dosimeter designs by increasing their thickness risks throttling the flowing current due to an attendant increase in series resistance. The presented design partially decouples this relationship by creating a low-coverage hydrogen-terminated collection volume around the device, exploiting the transfer doping effect. This paper proves that hydrogen termination is necessary for the gammavoltaism exhibited. Data are then presented from current-voltage curves taken using synchrotron radiation over the range 50-150 keV. A drop in the series resistance over the range is discovered and linked to the transition from the photoelectric effect to Compton scattering. The cell produces an open-circuit voltage VOC = 0.8 V. Its short-circuit current ISC and maximum power Pmax are found to also depend on photon energy, reaching maxima at ∼150 keV, where ISC > 10 μA and Pmax > 3 μW, normalized in flux to 2 × 1011 γ.s−1. Groundwork is hence laid for developing this type of cell for micropower applications.

Thermionic emission relies on the low work function and negative electron affinity of the, often functionalized, surface of the emitting material. However, there is little understanding of the interplay between thermionic emission and temperature-driven dynamic surface transformation processes as these are not represented on the traditional Richardson-Dushman equation for thermionic emission. Here, we show a new model for thermionic emission that can reproduce the effect of dynamic surface changes on the electron emission and correlate the components of the thermionic emission with specific surface reconstruction phases on the surface of the emitter. We use hydrogenated100single-crystal and polycrystalline diamonds as thermionic emitters to validate our model, which shows excellent agreement with the experimental data and could be applicable to other emitting materials. Furthermore, we find that tailoring the coverage of specific structures of the C(100)-(2 × 1):H surface reconstruction could increase the thermionic emission of diamond by several orders of magnitude.

The aim of this work is to study the heating efficiency of refractory microstructures by excitation of surface plasmon polaritons in the far infrared that can be used for high-temperature applications. The work has designed metal grating couplers on molybdenum films to maximise the absorption of a 10.6 µm CO 2 laser light source. Molybdenum has been chosen since it is an industrial refractory metal combined with the fact that its optical properties in the far infrared are similar to gold but with stable high-temperature performance. Linear gratings have been used as plasmonic couplers on large area substrates produced by laser milling. Real-time absolute temperature measurements have been performed showing a 42% increase in the maximum achievable temperature from 702 to 985 K.

Thermionic emitting materials are relevant for several technological applications like electron guns, X-ray sources, or thermionic energy converters. As new materials and surface functionalisations that enable thermionic emission are developed, it is essential to be able to test them in a repeatable and reliable manner. Here, we present a CO 2 laser-heated system for thermionic tests that can be used to test the thermionic emission current of different materials regardless of the optical properties or form factor. Our system can reach sample temperatures of T ≈ 1000 °C and can follow pre-programmed heating profiles. Additionally, a double thermo-electrical decoupling provides a very low electrical noise environment while keeping the sample heat loss to a minimum. Experimental data on sample temperature and thermionic current from a hydrogen terminated single crystal diamond are presented and discussed.