F2, H2O, and O2 etching rates of diamond and the effects of F2, HF and H2O on the molecular O2 etching of (110) diamond
TL;DR: In this article, Fizeau interferometry was used to investigate the second-order kinetics of the diamond etch with respect to O 2 pressure in the pressure range 0.04-10 Torr.
About: This article is published in Diamond and Related Materials.The article was published on 1995-11-01. It has received 27 citations till now. The article focuses on the topics: Diamond & Isotropic etching.
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TL;DR: A gas-phase method for raw nanotube material has been developed which incorporates a chlorine, water, and hydrogen chloride gas mixture to remove unwanted carbon as mentioned in this paper, which can be easily monitored by infrared spectroscopy to follow the cleaning process.
Abstract: A gas-phase purification method for raw nanotube material has been developed which incorporates a chlorine, water, and hydrogen chloride gas mixture to remove unwanted carbon. The evolved gases can be easily monitored by infrared spectroscopy to follow the cleaning process. The quality of the final material was verified by SEM (scanning electron microscopy), TGA (thermogravimetric analysis), and UV−vis (ultraviolet and visible absorption spectroscopy). The yield of ∼15 wt % indicates a uniquely selective carbon surface chemistry that prevents etching of the nanotubes, which are generally more reactive due to their larger curvature. Although the technique's usefulness for large-scale purification was not determined, the ability to purify single-wall nanotubes by a gas-phase method has been demonstrated, and a mechanism proposed.
160 citations
TL;DR: This work reports procedures of production and isolation of sub-20-nm FND particles utilizing He ion irradiation and differential centrifugation methods, and experiments demonstrating that they are useful as far-red fluorescent biolabels as well as FRET donors are presented.
Abstract: Adv. Mater. 2010, 22, 843–847 2010 WILEY-VCH Verlag Gm A current trend in fluorescent probe technology is to expand the role of fluorophores that emit light in the far red and near infrared region for biomedical use. The negatively charged nitrogenvacancy defect center, (N-V) , in type Ib diamond is one of such fluorophores and has drawn much attention in recent years. The center exhibits several distinct features such as extended red emission at 700 nm, near-unity fluorescence quantum yield, and ultrahigh photostability (neither photobleaching nor photoblinking). These characteristics, along with the diverse surface functionalizability and non-toxic nature of the material, have made fluorescent nanodiamond (FND) a promising candidate among other conventional markers and labels, for example, organic dyes, fluorescent proteins, and quantum dots, for bioimaging applications. Despite the unique photophysical and biochemical properties of FND, the size is an important parameter to characterize. Decreasing the size, clearly, will increase the mobility of the fluorescent nanoprobe inside a cell, avoid altering the properties of targeted molecules, and enhance its translocation into cell nuclei. Additionally, particles of size in the range of 10 nm are more suitable for biolabeling and fluorescence resonance energy transfer (FRET) applications. However, so far the sizecontrolled production of FNDs has not yet been so well developed as that of other probes and scale-up synthesis of smaller and brighter FNDs remains a challenging task. In this communication, we report procedures of production and isolation of sub-20-nm FND particles utilizing He ion irradiation and differential centrifugation methods, and experiments demonstrating that they are useful as far-red fluorescent biolabels as well as FRET donors are presented. Table 1 compares the optical properties between (N-V) and two representative red and far-red fluorescent proteins. The in vivo structure of the latter protein is in form of tetramer and, therefore, has a size close to 10 nm. A simple calculation based on the molar extinction coefficient and the fluorescence quantum yield indicates that the brightness of a single (N-V) center is 2-fold as high as that of this far-red fluorescent protein, owing to the superb quantum yield of the atom-like fluorophore. Moreover, the (N-V) center fluoresces in the farther red region, where both autofluorescence and light scattering from the active biological environment are reduced to a greater extent. While compared to the infrared dye (such as IRDye-800CW in Table 1), the (N-V) center is a factor of 5 lower in brightness, this deficit can be readily compensated if each FND particle contains multiple (N-V) centers. It is the aim of this work to produce FNDs with a size comparable to those of far-red fluorescent proteins and concurrently containing as many (N-V) centers as possible. A previous experiment has shown that FNDs can be mass-produced with 40-keV Heþ irradiation of synthetic type Ib diamond nanocrystallites, followed by thermal annealing at 800 8C. For diamond powders with amedian size of 35 nm from a commercial source (MSY; Microdiamant), they usually have a broad size distribution and 10% of the particles are smaller than 15 nm. By optimizing the experimental parameters in differential centrifugation, we extracted sub-20-nm FNDs from the 35-nm ensembles after theHeþ irradiation andmulti-step centrifugation procedures. The sizes of these particles were finally characterized with dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). As revealed by DLS (Fig. 1a), the average diameter of the smallest FNDs that we have been able to extract with use of a standard centrifuge (Model 3700; Kubota) is 11.5 nm, accompanied with a narrow size deviation from 10 to 14 nm. TEM and AFM (Figs. S1 and S2 in Supporting Information) also confirmed independently the size distribution centered in the range of 10 nm at the single particle level. To make a direct comparison of the optical properties between the 11-nm FNDs and monomeric red fluorescent proteins (recombinant DsRed; BioVision), we characterized both specimens in solution with fluorescence correlation spectroscopy (FCS).
126 citations
TL;DR: In this paper, the size reduction and effects on nitrogen-vacancy centers in nanodiamonds by air oxidation using a combined atomic force and confocal microscope were reported.
87 citations
TL;DR: The blinking mechanism of the NV centre in NDs is elucidated and a qualitative model proposed to explain this phenomenon in terms of the centre electron(s) tunnelling to acceptor site(s).
Abstract: Control over the quantum states of individual luminescent nitrogen-vacancy (NV) centres in nanodiamonds (NDs) is demonstrated by careful design of the crystal host: its size, surface functional groups, and interfacing substrate. By progressive etching of the ND host, the NV centres are induced to switch from latent, through continuous, to intermittent or "blinking" emission states. The blinking mechanism of the NV centre in NDs is elucidated and a qualitative model proposed to explain this phenomenon in terms of the centre electron(s) tunnelling to acceptor site(s). These measurements suggest that the substrate material and its proximity to the NV are responsible for the fluorescence intermittency.
80 citations
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TL;DR: In this article, the size reduction and effects on nitrogen-vacancy centers in nanodiamonds by air oxidation using a combined atomic force and confocal microscope were reported.
Abstract: Here we report the size reduction and effects on nitrogen-vacancy centres in nanodiamonds by air oxidation using a combined atomic force and confocal microscope. The average height reduction of individual crystals as measured by atomic force microscopy was 10.6 nm/h at 600 {\deg}C air oxidation at atmospheric pressure. The oxidation process modified the surface including removal of non-diamond carbon and organic material which also led to a decrease in background fluorescence. During the course of the nanodiamond size reduction, we observed the annihilation of nitrogen-vacancy centres which provided important insight into the formation of colour centres in small crystals. In these unirradiated samples, the smallest nanodiamond still hosting a stable nitrogen-vacancy centre observed was 8 nm.
75 citations
References
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TL;DR: In this paper, the mechanism of diamond growth by hot-filament chemical vapor deposition (CVD) was investigated on the (100, (111), and (110) crystal faces of natural diamond by competition studies using carbon-13labeled methane and carbon-12 acetylene.
Abstract: The mechanism of diamond growth by hot‐filament chemical vapor deposition (CVD) was investigated on the (100), (111), and (110) crystal faces of natural diamond by competition studies using carbon‐13‐labeled methane and carbon‐12 acetylene. Homoepitaxial growth rates of 0.4, 0.5, and 1.3 μm/h were obtained for growth on the (100), (111), and (110) faces, respectively. The (100)‐ and (111)‐oriented films were smooth initially, while films grown on (110) substrates quickly became rough. The (111) films had graphitic inclusions, as evidenced by the Raman spectrum, while the (100) and (110) films were graphite‐free. The (111) films also exhibited substantial tensile stress, as indicated by a shift in the Raman peak and by spontaneous cracking in films grown thicker than 3.5 μm. The carbon‐13 mole fraction of mixed 13C/12C diamond films grown on the diamond substrates was determined from the shift of the first‐order Raman frequency, after correction for the shift due to stress. The carbon‐13 mole fractions of ...
127 citations
TL;DR: In this article, Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD) were used to study the properties of CH bonding on diamond surfaces.
Abstract: The chemisorbed species on diamond surfaces have been studied by Fourier-transform infrared (FTIR), temperature-programmed desorption (TPD) and laser Raman spectroscopy. Oxidized diamond powders were treated thermally in an H2 environment. IR spectral changes were followed during the hydrogenation of oxidized diamond powders. We observed CH bonding on diamond surfaces. The amount of CH bonding increased with the temperature of treatment below 900 °C. Above 900 °C, the amount of the CH bonding decreased. Thermally desorbed species were analysed by mass spectrometry. H2 was desorbed from hydrogenated diamond powders above ca. 800 °C. Close agreement between FTIR and TPD results was obtained. Raman spectra indicated that the disordered graphitic carbon phase was formed above 900 °C.
105 citations
TL;DR: In this paper, the diamond (100) and diamond (111) surfaces have been exposed to beams of atomic and molecular fluorine and chlorine in an ultrahigh-vacuum environment and X-ray photoelectron spectroscopy, low energy electron diffraction, and thermal desorption techniques have been used to elucidate the chemistry involved.
Abstract: Diamond (100) and (111) surfaces have been exposed to beams of atomic and molecular fluorine and chlorine in an ultrahigh‐vacuum environment. X‐ray photoelectron spectroscopy, low‐energy electron diffraction, and thermal desorption techniques have been used to elucidate the chemistry involved. F atoms add to both the diamond (100)‐(1×1) and (111)‐(2×1) surfaces to form a carbon‐monofluoride species which reaches a saturation level of approximately three‐quarters of a monolayer at 300 K. In other aspects of their behavior, the diamond surfaces differ. On the (111) surface, the rate of fluorine atom uptake is, to first order, proportional to the open site concentration. Adsorption produces a dimming of the half‐order electron‐diffraction spots, suggesting the breaking of surface π‐bonded chains to form regions of the bulk 1×1 reconstruction. The (100) surface uptake rate, though, is second order with respect to open site concentration and no electron‐diffraction pattern is observed. This difference in behavior between the two surfaces is ascribed to the difference in bonding geometry, leading to severe steric hindrance to ordered adsorption on the (100) surface. The thermal desorption data show fluorine desorption over a wide temperature range (500–1200 K) on both surfaces indicating binding sites with a range of energies.Limited mass spectrometric data indicates that atomic fluorine is the major desorption product. These results imply that atomic fluorine will act in a fashion similar to hydrogen atoms in that they will break surface dimer bonds, desorb from the surface at an appropriate temperature without etching diamond, and abstract any surface hydrogen in deposition systems utilizing halocarbon species. The much larger chlorine atoms weakly chemisorb on the diamond (100) surface, producing a saturation coverage of less than half a monolayer at 300 K. The adlayer neither shows a distinct C‐Cl peak in the x‐ray photoelectron spectra nor exhibits any electron‐diffraction pattern. In addition, thermal desorption studies indicate that the concentration of chlorine atoms monotonically decreases to virtually zero as the substrate is heated from 223 to 423 K. A small residual chlorine concentration remains up to 600 K, presumably due to binding at defect sites. This behavior implies that atomic chlorine will exhibit a less significant role in the surface chemistry of diamond deposition systems.
61 citations
TL;DR: The temperature and pressure variations of the refractive index for a Type IIa diamond have been measured at audio frequencies using capacitance techniques and the curvature in theRefractive index with temperature has been determined.
Abstract: The temperature and pressure variations of the refractive index for a Type IIa diamond have been measured at audio frequencies using capacitance techniques. Measurements have been made at zero pressure over the 5.5–340-K temperature range and at pressures up to 1.4 × 108 Pa (1.4 kbar) at room temperature. At room temperature, (1/n)(dn/dT)p = +4.04 × 10−6/K and (1/n)(dn/dp)T = −0.36 × 10−12/Pa. In addition, the curvature in the refractive index with temperature has been determined. The first-order derivatives are compared with previous experimental data and the recent theoretical calculations of Van Vechten and Yu and Cardona.
54 citations