Visible-Light Activation of Photocatalytic for Reduction of Nitrogen to Ammonia by Introducing Impurity Defect Levels into Nanocrystalline Diamond.

Nitrogen impurity has been introduced in diamond film to produce a nitrogen vacancy center (NV center) toward the solvated electron-initiated reduction of N2 to NH3 in liquids, giving rise to extend the wavelength region beyond the diamond's band. Scanning electron microscopy and X-ray diffraction demonstrate the formation of the nanocrystalline nitrogen-doped diamond with an average diameter of ten nanometers. Raman spectroscopy and PhotoLuminescence (PL) spectrum show characteristics of the NV0 and NV- charge states. Measurements of photocatalytic activity using supraband (λ < 225 nm) gap and sub-band gap (λ > 225 nm) excitation show the nitrogen-doped diamond significantly enhanced the ability to reduce N2 to NH3 compared to the polycrystalline diamond and single crystal diamond (SCD). Our results suggest an important process of internal photoemission, in which electrons are excited from negative charge states into conduction band edges, presenting remarkable photoinitiated electrons under ultraviolet and visible light. Other factors, including transitions between defect levels and processes of reaction, are also discussed. This approach can be especially advantageous to such as N2 and CO2 that bind only weakly to most surfaces and high energy conditions.

Fabrication of concave microlenses on a diamond by a spin coating process.

In this study, to fabricate diamond concave microlenses in a simple manner, an approach that combines a spin coating process with subsequent dry etching was demonstrated. First, photolithography was used to produce cylindrical holes in the photoresist layer on the diamond surface. Then, another photoresist was spin coated to fill the holes, and the concave structures with meniscus shapes were then obtained because of centrifugal force and interfacial tension. Finally, diamond concave microlenses were formed by transferring photoresist concave structures onto a diamond substrate using a dry etching technique. The fabricated diamond microlens exhibits a low surface roughness with nanometers as well as high-quality imaging and focusing performances, which is expected to have a wider range of potential applications under harsh and special conditions.

Characterization of UV photodetector based on ZnO/diamond film.

In this study, a ZnO/diamond structure ultraviolet (UV) photodetector was fabricated and investigated. ZnO films with thickness of 50 and 100 nm were deposited on half of diamond substrates by sputtering technique. Then, electrodes were patterned on ZnO and diamond areas to form photodetectors. The photocurrent gain in the UV region has been strongly influenced by ZnO film. ZnO films with thickness of 50 and 100 nm on diamond substrates reaches 14.3 and 308 A/W, respectively. Both of peak responsivities were located at 270 nm. Additionally, two shoulder peaks around 240 nm and 290 nm were observed for ZnO/diamond photodetector, which may stem from diamond and ZnO, respectively.