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The development of a stable, non‐toxic material that emits electrons following absorption of visible light may have a major impact on the solar photocatalysis of difficult reactions such as CO2 and N2 reduction, as well as for targeted chemical transformations in general. Diamond is a good candidate, however it is a wide bandgap material requiring deep UV photons ( λ ${{\rm{{\rm \lambda} }}}$ <227 nm) to promote electrons from the valence band into the conduction band. Embedding silver nanoparticles under the diamond surface allows the photoconductivity of the diamond in the spectral region of the surface plasmon resonance to be increased, while also leading to an enhancement of visible light photoemission. Considering the low intensity of the light sources used in this work and the spectral properties of the enhanced photoconductivity and photoemission a mechanism based on plasmonically enhanced photoconductivity which in turn allows surface states emptied by photoemission to be recharged thus leading to enhanced photoemission in the visible range is proposed. [ABSTRACT FROM AUTHOR]

Orthorhombic κ-Ga2O3 thin films were grown for the first time on polycrystalline diamond free-standing substrates by metal-organic vapor phase epitaxy at a temperature of 650 °C. Structural, morphological, electrical, and photoelectronic properties of the obtained heterostructures were evaluated by optical microscopy, X-ray diffraction, current-voltage measurements, and spectral photoconductivity, respectively. Results show that a very slow cooling, performed at low pressure (100 mbar) under a controlled He flow soon after the growth process, is mandatory to improve the quality of the κ-Ga2O3 epitaxial thin film, ensuring a good adhesion to the diamond substrate, an optimal morphology, and a lower density of electrically active defects. This paves the way for the future development of novel hybrid architectures for UV and ionizing radiation detection, exploiting the unique features of gallium oxide and diamond as wide-bandgap semiconductors. [ABSTRACT FROM AUTHOR]

A recent innovation in diamond technology has been the development of the "black diamond" (BD), a material with very high optical absorption generated by processing the diamond surface with a femtosecond laser. In this work, we investigate the optical behavior of the BD samples to prove a near to zero dielectric permittivity in the high electric field condition, where the Frenkel-Poole (FP) effect takes place. Zero-epsilon materials (ENZ), which represent a singularity in optical materials, are expected to lead to remarkable developments in the fields of integrated photonic devices and optical interconnections. Such a result opens the route to the development of BD-based, novel, functional photonic devices. [ABSTRACT FROM AUTHOR]

Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power electronic devices. The use of nanosecond pulse excimer lasers enabled the microstructuring of diamond surfaces, and refined techniques such as controlled ablation through graphitization and etching by two-photon surface excitation are being exploited for the nanostructuring of diamond. On the other hand, ultrashort pulse lasers paved the way for a more accurate diamond microstructuring, due to reduced thermal effects, as well as an effective surface nanostructuring, based on the formation of periodic structures at the nanoscale. It resulted in drastic modifications of the optical and electronic properties of diamond, of which "black diamond" films are an example for future high-temperature solar cells as well as for advanced optoelectronic platforms. Although experiments on diamond nanostructuring started almost 20 years ago, real applications are only today under implementation. [ABSTRACT FROM AUTHOR]

An array of 2500 vertical graphitic microwires was fabricated within a single-crystal diamond plate with the purpose of creating distributed electrically conductive structures intended for the development of electronic devices operating at high temperatures. To this end, the structural, morphological, and electrical properties of the diamond/graphite system were investigated as a function of temperature up to 550 °C, by means of optical and secondary electron microscopy (SEM), micro-Raman spectroscopy and current-voltage measurements. The vertical microstructuring of the diamond bulk was obtained by a laser-induced phase transition from diamond to graphite by means of ultra-short laser pulses (100 fs duration, 800 nm wavelength, 1 kHz repetition rate). As inferred from SEM micrographs, the graphitic wires display a high-aspect-ratio with length of approximately 200 μm and diameter of about 10 μm. The electrical resistivity of the single microwire is estimated to be 0.49 ± 0.15 Ω cm at room temperature, then decreasing linearly with temperature with a coefficient of approximately −1 × 10−2 K−1. Raman spectroscopy results point out the absence of structural alterations after high-temperature operations. [Display omitted] • Graphitic microwires were fabricated within a diamond plate by laser-induced phase transition. • The microwires display a high-aspect-ratio. Length of 200 μm and diameter of 10 μm. • Electrical resistivity of the microwire is estimated to be 0.49 ± 0.15 Ω cm at RT. • Plate bulk resistance plate is 10 orders of magnitude lower than pristine system. • Ageing processes did not induce structural or electrical alterations on the system. [ABSTRACT FROM AUTHOR]

Irradiation of diamond with femtosecond (fs) laser pulses in ultra-high vacuum (UHV) conditions results in the formation of surface periodic nanostructures able to strongly interact with visible and infrared light. As a result, native transparent diamond turns into a completely different material, namely "black" diamond, with outstanding absorptance properties in the solar radiation wavelength range, which can be efficiently exploited in innovative solar energy converters. Of course, even if extremely effective, the use of UHV strongly complicates the fabrication process. In this work, in order to pave the way to an easier and more cost-effective manufacturing workflow of black diamond, we demonstrate that it is possible to ensure the same optical properties as those of UHV-fabricated films by performing an fs-laser nanostructuring at ambient conditions (i.e., room temperature and atmospheric pressure) under a constant He flow, as inferred from the combined use of scanning electron microscopy, Raman spectroscopy, and spectrophotometry analysis. Conversely, if the laser treatment is performed under a compressed air flow, or a N2 flow, the optical properties of black diamond films are not comparable to those of their UHV-fabricated counterparts. [ABSTRACT FROM AUTHOR]

The inclusion of aluminium (Al) nanoparticles (NPs) in chemical vapor deposition (CVD) diamond structures was achieved by depositing Al thin films on commercial CVD single-crystal diamond plates, and then covering them by a CVD diamond thin film to encapsulate the metal NPs formed by the dewetting occurring during the CVD process. Morphology and composition are investigated, showing a peculiar structure formed by an Al/diamond composite with both Al NPs and Al 2 O 3 islands included and surrounded in the diamond matrix, respectively. A mosaic-patterned homoepitaxial growth occurs for the capping diamond layer. The experimentally measured reflectivity matches the simulation of a system where the thickness of the Al/diamond composite layer is 1.80 ± 0.05 μm and the composition is 95 ± 2 % diamond and 5 ± 2 % Al. Simulations of the plasmonic response of Al NPs embedded in the diamond layer suggest that the decrease in transmission of the sample in the blue region of the spectrum is unlikely to be due to plasmonic absorption by the NPs. It is concluded that the shape of the transmission spectrum follows a Rayleigh-like scattering induced by the nanoporous diamond film. Ultrafast transient absorption measurements allow us to identify a sharp feature at 700 nm which can be associated with a modification of an interband transition in Al due to heating after photon absorption at 380 nm. [Display omitted] • Al nanoparticles were embedded in diamond to study the plasmonic response. • Despite a large increase in visible absorption, no plasmonic behavior was found. • Rayleigh like scattering is considered to explain the induced optical properties. • The formed structure can be applied in diamond systems to exploit visible light. [ABSTRACT FROM AUTHOR]