The formation and thermodynamic stability of silicon‐vacancy (Si‐V) color centers, intensively emitting at a wavelength of 738 nm, are demonstrated for the first time in nanodiamonds less than 10 nm in size. These findings open prospects for the production of stable and efficient optical nanoemitters (single‐photon emitters) based on nanodiamond.

Ultrananocrystalline diamond films (UNCD) grown in an Ar‐rich microwave plasma with nitrogen gas added in amounts of 0–25% were studied by Raman spectroscopy using 514.5 and 413.1 nm laser excitation. Besides the Raman spectra of diamond, the first and second order Raman scattering of disordered graphite and polyacetylene were detected and analyzed for samples with different nitrogen content. With surface enhanced Raman scattering (SERS) a variety of surface vibrational modes was observed: (i) CHx stretching vibrations of sp3 and sp2 hybridized carbon in the range of 2800–3100 cm–1; (ii) the sp2 and sp1 hybridized CC(CN) stretching modes in the range of 1600–2300 cm–1; and (iii) lines in the range of 200–1250 cm–1 related to different kinds of vibrations of substituted aromatic rings. These results indicate that in N‐doped UNCD films the intergrain material is a well connected mixture of predominantly sp2 phase with some amount of sp1 phase of carbon and nitrogen that is suggested to provide high electrical conductivity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Application of diamond, which is a broadband semiconductor with unique properties, in electronics [1] faces a number of problems, including difficulties of doping for obtaining the n type conductivity. In par ticular, it is very difficult to avoid the appearance of structural defects of a lattice upon doping with phos phorus. In addition, phosphorus has too deep a level with an activation energy of 0.6 eV. The n type con ductivity was found [2] in an interesting kind of dia mond, ultrananocrystalline diamond (UNCD) films consisting of diamond grains smaller than 10 nm.Ultrananocrystalline diamond films are synthe sized by chemical deposition of carbon from a gas phase (CVD method) in an argon (or another inert gas) plasma with addition of 1-2% of carbon in the form of C 60 or CH 4 molecules [3,4]. The addition of nitrogen to the plasma is accompanied by the transi tion of films from a dielectric state to a well conduct ing state. When the concentration of N 2 exceeds a cer tain critical value (10-15%) in the gas, such a transi tion is accompanied by an increase in the conductivity by 10-12 orders of magnitude to about 100 Ω -1 cm -1 [2, 5] with an activation energy of <10 meV [6]. It was found that the conductivity of nitrided UNCD films is due to the electron transport [2,6]. It cannot be explained by the volume doping of diamond with nitrogen, although a substituting nitrogen atom in the diamond lattice is a donor. Since the activation energy of the nitrogen donor is high (1.7 eV), the high con centration of free electrons (10 21 cm -3 ) that is observed in nitrided UNCD films [6] cannot be reached.It is commonly accepted that conduction in UNCD films is not attributed to the bulk of nanodia mond grains. It was assumed that conductivity is due to structural defects of intergrain boundaries. Early attempts to describe the appearance of conductivity were based on the theory of the electron density func tional under the assumption of tight binding (Density Functional based Tight Binding (DFTB) method) for simulating the structure of defects created at intercrys tallite boundaries by the introduced nitrogen [7]. However, the simulation results were contradictory. According to some DFTB calculations [7], nitrogen at grain boundaries leads to an increase in the number of structural defects with weakly localized electrons. According to other DFTB calculations [8], nitrogen stimulates the formation of acceptor defects. However, it was found in more recent experiments that a con ductivity jump correlates with the fundamental rear rangement of the structure of a film [9, 10] that is manifested in the appearance of diamond nanorods with a length of hundreds of nanometers in a conduct ing carbon shell.In this work, the features and evolution of the microstructure of UNCD films upon their nitriding (addition of nitrogen in the plasma) are studied using transmission electron microscopy and small angle X ray scattering. Using the percolation model, we quantitatively consider an insulator-conductor tran sition in these films, ...

The diamond phase precursor, viz., poly(naphthalenehydrocarbyne) (1), was prepared. Its disordered structure is built of CH fragments with sp 3 hybridized carbon atoms, and arene fragments are inserted in the structure. The use of 1 in the process of diamond layer deposition makes it possible to prepare highly qualitative thin diamond coatings with low roughness and good optical properties.Uniform thin diamond films (DFs) with low surface roughness and nanocrystalline internal structure are de manded for planar electronic devices, protective optical coatings, and micro and nanoelectromechanical sys tems. 2 The most important condition for preparation of such DFs is efficient nucleation, for which the method with ultradispersed diamond (UDD) deposition (usual for thick (>1 μm) 3 DFs) is inappropriate because of low den sity and nonuniform nuclei distribution on the substrate. It is known that the efficiency of UDD application can be enhanced by deposition of a layer of carbon 4 and ceramics SiC, SiN x , and TiSiN (see Ref. 5). However, nuclei gener ation from an appropriate precursor can serve as a radical method for nucleation improvement. Poly(phenylcarbyne) has been used earlier 6-9 for this purpose. However, thus obtained films consisted of diamond like carbon with dia mond inclusions. In the present study, we describe the synthesis of poly(naphthalenehydrocarbyne) (1), viz., a new precursor combining the aliphatic framework and aromatic fragments in its structure. Its structure and po tential for using in diamond layer deposition on a silicon substrate were studied. Results and DiscussionSynthesis of polymer 1. The general method for pre paration of polymers of the poly[(R )carbyne] series (R = Ar, Alk, H), in particular, polymers 2 and 3, is the condensation of heme trihalides by the action of a KNa alloy in the ultrasonic field 10,11 (Scheme 1, reaction a) or by electrolysis 12,13 (Scheme 1, reaction b). Note that these methods have several substantial drawbacks. For exam ple, the use of an explosive KNa alloy in reaction a makes the latter almost impracticable. Reaction b is also very difficult in methodical respect (anaerobic electrolysis ac companied by Cl 2 evolution is required, the product needs purification by prolonged heating with LiAlH 4 , etc. 12,13 ). The product yield in procedures a and b is low, and a strong dependence of the properties of the polymers on many random factors is observed. Thus, search for convenient methods of synthesis of poly(carbynes) and, first of all, poly(hydrocarbyne) (3) as the most promising of them, remains topical. Scheme 1 a. Ultrasonication. b. Electrolysis. R = Ph (2), H (3)