RESUMEN
Nanostructuring of a bulk material is used to change its mechanical, optical, and electronic properties and to enable many new applications. We present a scalable fabrication technique that enables the creation of densely packed diamond nanopillars for quantum technology applications. The process yields tunable feature sizes without the employment of lithographic techniques. High-aspect-ratio pillars are created through oxygen-plasma etching of diamond with a dewetted palladium film as an etch mask. We demonstrate an iterative renewal of the palladium etch mask, by which the initial mask thickness is not the limiting factor for the etch depth. Following the process, 300-400 million densely packed 100 nm wide and 1 µm tall diamond pillars were created on a 3 × 3 mm2 diamond sample. The fabrication technique is tailored specifically to enable applications and research involving quantum coherent defect center spins in diamond, such as nitrogen-vacancy (NV) centers, which are widely used in quantum science and engineering. To demonstrate the compatibility of our technique with quantum sensing, NV centers are created in the nanopillar sidewalls and are used to sense 1H nuclei in liquid wetting the nanostructured surface. This nanostructuring process is an important element for enabling the wide-scale implementation of NV-driven magnetic resonance imaging or NV-driven NMR.
RESUMEN
The negatively charged nitrogen-vacancy (NV) center in diamond has been shown recently as an excellent sensor for external spins. Nevertheless, their optimum engineering in the near-surface region still requires quantitative knowledge in regard to their activation by vacancy capture during thermal annealing. To this aim, we report on the depth profiles of near-surface helium-induced NV centers (and related helium defects) by step-etching with nanometer resolution. This provides insights into the efficiency of vacancy diffusion and recombination paths concurrent to the formation of NV centers. It was found that the range of efficient formation of NV centers is limited only to approximately 10 to 15 nm (radius) around the initial ion track of irradiating helium atoms. Using this information we demonstrate the fabrication of nanometric-thin (δ) profiles of NV centers for sensing external spins at the diamond surface based on a three-step approach, which comprises (i) nitrogen-doped epitaxial CVD diamond overgrowth, (ii) activation of NV centers by low-energy helium irradiation and thermal annealing, and (iii) controlled layer thinning by low-damage plasma etching. Spin coherence times (Hahn echo) ranging up to 50 µs are demonstrated at depths of less than 5 nm in material with 1.1% of (13)C (depth estimated by spin relaxation (T1) measurements). At the end, the limits of the helium irradiation technique at high ion fluences are also experimentally investigated.
RESUMEN
A novel analytical platform combining infrared attenuated total reflection (IR-ATR) spectroelectrochemistry (SE) with atomic force microscopy (AFM) using a boron-doped diamond (BDD)-modified ATR crystal is presented. The utility of this combination is demonstrated investigating the electrodeposition of a polymer film via IR spectroscopy, while the surface modification is simultaneously imaged by AFM. The ATR waveguide consists of a single-crystal intrinsic diamond overgrown with a homoepitaxial BDD layer (thickness: â¼100 nm, boron content: â¼5 × 10(20) cm(-3)) to provide electric conductivity. The diamond ATR crystal is shaped in the form of a hemisphere with a beveled top and an octahedronal surface area of approximately 400 µm(2). To demonstrate combined IR-ATR-SE-AFM measurements, the electro-polymerization of 3,4-ethylenedioxothiophene (EDOT) was selected as a model system. Depositions were obtained from aqueous solutions, while changes in IR signature, topography, and electrochemical behavior were recorded in situ and simultaneously during the polymerization process.