Diamond with nitrogen: states, control, and applications

The burgeoning multi-field applications of diamond concurrently bring up a foremost consideration associated with nitrogen. Ubiquitous nitrogen in both natural and artificial diamond in most cases as disruptive impurity is undesirable for diamond material properties, eg deterioration in electrical performance. However, the feat of this most common element-nitrogen, can change diamond growth evolution, endow diamond fancy colors and even give quantum technology a solid boost. This perspective reviews the understanding and progress of nitrogen in diamond including natural occurring gemstones and their synthetic counterparts formed by high temperature high pressure (HPHT) and chemical vapor deposition (CVD) methods. The review paper covers a variety of topics ranging from the basis of physical state of nitrogen and its related defects as well as the resulting effects in diamond (including nitrogen termination on diamond surface), to precise control of nitrogen incorporation associated with selective post-treatments and finally to the practical utilization. Among the multitudinous potential nitrogen related centers, the nitrogen-vacancy (NV) defects in diamond have attracted particular interest and are still ceaselessly drawing extensive attentions for quantum frontiers advance.</p

Doomed Couple of Diamond with Terahertz Frequency: Hyperfine Quality Discrimination and Complex Dielectric Responses of Diamond in the Terahertz Waveband

The technology age of terahertz (THz) frequency is coming with tremendous features and astonishing applications in various fields of science. Using THz time domain spectroscopy, we demonstrate experimentally, for the first time, the fingerprint absorption peaks and the complex dielectric response trends in 0.1-3 THz frequency waveband, on intentionally synthesized and processed chemical vapour deposition (CVD) polycrystalline and single-crystal diamond films with systematic quality-difference. The two absorption signatures within the 0.1-3 THz frequency band, in which the atomic vibration is materials-independent, are attributed to the sp2 phonon vibration modes of as-grown graphitic phases and/or defects. Regarding the complex dielectric responses of diamond in THz waveband, scattering effect resulting from the extended grain boundaries associated with concomitant pores (even gaps) (and/or extended crystal cleavage faults associated with amorphous carbon), as well as intrinsic lattice absorption resulting from increased sp2 impurities, have been taken into account. Especially the defect size comparable with the wavelength is also found to play a significant effect on the loss at higher-frequency electromagnetic wave. These findings are expected to promote not only ultra-sensitive quality diagnose for diamond but verification of an ideal transmission material for THz waveband applications

Smoothing of single crystal diamond by high-speed three-dimensional dynamic friction polishing: Optimization and surface bonds evolution mechanism

The high-speed three-dimensional movement dynamic friction polishing (3DM-DFP) has been recognized as an efficient approach for ultra-smoothing single crystal diamond (SCD) surface. Continuing from the previous works focusing on the subsurface cleavage of diamond after 3DM-DFP, process optimization and surface reaction evolution mechanism as a fundamental building block is investigated, for the first time, for comprehensively understanding this fast-smoothing manner. By systematically adjusting the controlling factor, stronger load (0.3 MPa) and appropriate duration (0.5 h) as well as moderate sliding speed (in the range of 30 to 45 m s−1) is found to be able to obtain the smooth surface of SCD without uncontacted traces or break-surface cleavage. Subtle residual clues on SCD surface as a function of progressive DFP procedure indicate that Fe catalytic oxidation mainly produce Fe2O3 and partial intermediate oxides Fe1-yO. Meanwhile, the activated oxygen inserts sp3 Csingle bondC bonds could form Csingle bondO or Cdouble bondO and C-O-V (vacancy) at existing reactive surface sites. The (100) favorable Cdouble bondO bonds can be rebuilt if (100) surface is reformed, although the Csingle bondO bonds associated with non-(100) rough surface would replace them during DFP procedure. The formed Csingle bondOsingle bondC and concomitant C-O-V as well as the oxidized graphite give rise to the increase of Csingle bondO proportion, and finally the covered defective graphitic phase has an approximate Csingle bondO/Cdouble bondO ratio of 1.25. All these are endowed potential value for future upgrading of DFP technique for diamond surface smoothing.</div

Evolutionary features of subsurface defects of single crystal diamond after dynamic friction polishing

Due to the fatigue and continuous energy input during high-speed dynamic friction polishing (DFP), the diamond crystal beneath the polished surface (roughness 50 nm) and even preferential crystal cleavage with the non-diamond phase (distributing at the position in micrometers range).</p

Evolutionary features of subsurface defects of single crystal diamond after dynamic friction polishing

Due to the fatigue and continuous energy input during high-speed dynamic friction polishing (DFP), the diamond crystal beneath the polished surface (roughness 50 nm) and even preferential crystal cleavage with the non-diamond phase (distributing at the position in micrometers range).</p

Additional file 1: Table S1. of Clinical significance of CDH13 promoter methylation as a biomarker for bladder cancer: a meta-analysis

Egger’s funnel plot of the publication bias test for CDH13 methylation. (DOCX 21 kb