The negatively charged Nitrogen-vacancy (NV-) color center in diamond is widely studied because of numerous applications of this unique quantum system in sensing and quantum information sciences. While substitutional nitrogen is required to form NV- centers, it also yields other paramagnetic defects - primarily the neutrally charged substitutional nitrogen centers (P1) - that decrease NV- spin coherence which in turn degrades performance in applications. Herein, we investigate high-pressure high-temperature synthesized diamond microparticles (ca. 140-185 μm) having lower - ranging from 3 to 38 ppm - than the typical nitrogen content of type 1b diamond (ca. 100 ppm and higher) typically used for production of fluorescent diamond particles with NV- centers. A suite of electron paramagnetic resonance, optically detected magnetic resonance, and nuclear magnetic resonance methods are used to characterize spin properties of P1 and NV- centers in the particles. Upon decreasing the nitrogen content from 29 ppm to 3 ppm, the ensemble NV- T 2 relaxation time increased by about 3-fold as measured directly in the Hahn Echo experiment at 1.2 Tesla. Analysis of electronic relaxation of P1 centers revealed the existence of at least two distinct populations of P1 centers, consisting of fast and slower relaxing spins. Even with <10 ppm nitrogen contents, the analysis indicated a highly heterogenous distribution of P1 centers, suggesting the possibility of P1 spin clustering in even at low concentrations. The combined data demonstrate that the particles prepared from HPHT diamond with a low nitrogen content offer improved spin properties that are beneficial for NV- sensing applications.

Color centers in diamond are promising platforms for quantum technologies. Most color centers in diamond discovered thus far emit in the visible or near-infrared wavelength range, which are incompatible with long-distance fiber communication and unfavorable for imaging in biological tissues. Here, we report the experimental observation of a new color center that emits in the telecom O-band, which we observe in silicon-doped bulk single crystal diamonds and microdiamonds. Combining absorption and photoluminescence measurements, we identify a zero-phonon line at 1221 nm and phonon replicas separated by 42 meV. Using transient absorption spectroscopy, we measure an excited state lifetime of around 270 ps and observe a long-lived baseline that may arise from intersystem crossing to another spin manifold.

Fluorescent nanodiamonds made from high-pressure high-temperature diamond are increasingly used in biological imaging and sensing applications. To date, only red and green fluorescent nanodiamonds are widely available, severely limiting nanodiamond-based multiplexed imaging. Here, we report on recent progress in the fabrication and characterization of fluorescent nanodiamonds with fluorescence colors from 450 nm to 900 nm. The fluorescence originates from a range of fluorescent color centers based on nitrogen, silicon, nickel and vacancy defects in the diamond lattice. The optical properties of these color centers in diamond nanoparticles are discussed in detail and the utility of nanodiamond-based multiplexed bioimaging demonstrated in experiments in-vitro.

Micron-sized samples of Ib type high-pressure-high-temperature diamonds synthesized with low and high substitutional nitrogen content and high energy e-beam irradiated to form luminescent negatively charged nitrogen-vacancy (NV-) centers are studied by X-band electron paramagnetic resonance (EPR), photoluminescence (PL), and Raman techniques. High nitrogen doping leads to the appearance of paramagnetic centers characterized by strong interactions between unpaired spins of substitutional nitrogen defects. Actual concentrations of paramagnetic substitutional nitrogen and NV- centers were obtained by EPR. The intensity of the PL emission from NV- centers was analyzed as a function of the content of NV- centers. We report that the NV-PL intensity is controlled by both the content of NV-centers and the presence of nitrogen-related crystal defects/ imperfections. Increasing the nitrogen content increases the structural imperfections, which are responsible for the appearance of additional nonradiative recombination centers and significant intensification of PL quenching.

Two key process features that are used to make 45 nm generation metal gate + high-k gate dielectric CMOS transistors are highlighted in this paper. The first feature is the integration of stress-enhancement techniques with the dual metal-gate + high-k transistors. The second feature is the extension of 193 nm dry lithography to the 45 nm technology node pitches. Use of these features has enabled industry-leading transistor performance and the first high volume 45 nm high-k + metal gate technology.

Cliff I. Davidson, Daniel P. Y. Chang, Adam Dalis, Sheryl H. Ehrman, Steven L. Heisler, George M. Hidy, Anshuman A. Lall, Thomas Lesniewski, Peter H. McMurry, Sotiris E. Pratsinis, Daryl L. Roberts, Paul T. Roberts, Weizhi Rong, Patrick Sislian, Chandra Venkataraman, Chiu-Sen Wang, Robert S. Windeler, and Cheng Xiong 1 Department of Civil & Environmental Engineering and Engineering & Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA 2 Department of Civil & Environmental Engineering, University of California—Davis, Davis, California, USA 3 Intel Corporation, Portland Technology Department, Hillsboro, Oregon, USA 4 Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, USA 5 ENSR Corporation, Camarillo, California, USA 6 Envair/Aerochem, Placitas, New Mexico, USA 7 Department of Mechanical Engineering, University of Maryland, College Park, Maryland, USA 8 Northrup Grumman Corporation, San Diego, California, USA 9 Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA 10 Particle Technology Laboratory, Swiss Federal Institute of Technology, Zurich, Switzerland 11 MSP Corporation, Shoreview, Minnesota, USA 12 Sonoma Technology, Inc., Petaluma, California, USA 13 UCLA BH5531, Los Angeles, California, USA 14 Department of Chemical and Biomolecular Engineering, University of California—Los Angeles, Los Angeles, California, USA 15 Department of Chemical Engineering, India Institute of Technology—Bombay, Powai, Mumbai, India 16 124 Idaho Avenue, Unit 304, Santa Monica, CA, USA 17 OFS Laboratories, Murray Hill, New Jersey, USA 18 Intel Corporation, DC1 Lithography, RA2, Hillsboro, Oregon, USA

Previous studies in our laboratory have shown that individual nanoparticle chain aggregates (NCAs) exhibit unusual mechanical behaviour when under strain inside the transmission electron microscope. NCAs made of various materials (e.g. carbon, metal oxides and metals) were strained by as much as 100% under tension. The nanoparticles that compose the chains were 5-10 nm in diameter and the chains of the order of 1 mu m in length. Such aggregates are of technological importance in the manufacture of nanocomposite materials (e.g. rubber), aggregate break-up (e.g. sampling diesel emissions) and chemical-mechanical planarization. The goal of this study was to simulate the mechanical behaviour of chain aggregates with morphological properties similar to those of technological interest. Molecular dynamics (MD) and energy minimization computer simulations are employed to investigate, at the atomic scale, the behaviour of short nanoparticle aggregates under strain and to obtain quantitative information on the forces involved in aggregate straining and fracturing. The interaction potential used is that of copper obtained with the embedded atom method (EAM). Two seven-nanoparticle aggregates are studied, one linear and the other kinked. The seven nanoparticles in both aggregates are single crystals and about 2.5 nm in diameter each. The aggregates are strained along their longest dimension, to the breaking point, at strain rates spanning from 2.5 x 10(7) to 8.0 x 10(8) s(-1) (MD simulations). The linear aggregate yield strain is about 0.1. The kinked aggregate elastic limit is also about 0.1, but only one-third of the stress develops along the straining direction compared to the linear aggregate. The kinked aggregate breaks at a strain of about 0.5, five times higher than the breaking strain of the linear aggregate. The ability of the kinked aggregate to straighten through combined nanoparticle interface sliding and rotation accounts for the extra strain accommodation. Simulation strain rates are orders of magnitude higher than the experimental ones. However, aggregate behaviour is independent of strain rates over the range studied here. The MD and energy minimization straining gave very similar results. In the elastic regime, the I,S-11 modulus for the seven-nanoparticle kinked aggregate is about one-fifth of the bulk value. This is due to a combined effect of the small primary particle diameter and the aggregate kinked structure. If this softening behaviour also occurs for nanoparticle aggregates of other materials (e.g. carbon, silica), nanoparticle aggregates, in some cases, may be strained along with the nanocomposite they reinforce.

Previous studies in our laboratory have shown that individual nanoparticle chain aggregates (NCA) exhibit remarkable mechanical behavior when under strain inside the transmission electron microscope. NCA made of various materials (e.g. carbon, metal oxides, metals, etc.) were strained by as much as 100% when tension was applied to them. After breaking, the NCA rapidly contracted to form more compact structures. In this study, molecular dynamics (MD) computer simulations are employed to investigate, at the atomic scale, the behavior of short nanoparticle chains under strain and to obtain quantitative information of the forces involved in chain straining and fracturing. The interaction potential used is that of copper obtained with the embedded atom method (EAM). Although the methodology is generally applicable, copper was selected as a test material because reliable interatomic potentials are available. Seven single-crystal nanoparticles, each 2.452 nm in diameter, are placed in contact in two chain configurations, linear and kinked. The structures are initially relaxed adiabatically with MD steps for 225 ps, at a starting temperature of 300 K. The bonding energy between any two nanoparticles in contact ranges from about 20 eV to 30 eV at 0 K. The two relaxed chain configurations are strained along their longest dimension, to the breaking point, at strain rates spanning from 0.3 m/s to 10 m/s. We identify mechanisms of stress accommodation that lead to plastic deformation and eventually fracture for both chain configurations, linear and kinked, and we construct the corresponding stress-strain curves. The two chain configurations exhibit different mechanical behavior. Applications of our experimental and simulation studies on NCA are to the behavior of nanocomposite materials, including carbon black reinforced rubber, sampling of aggregates by high speed impactors and the formation of flexible coatings of nanoparticles.

Chain aggregates composed of nanoparticles of carbon black, silica, titania and other metal oxides are produced commercially using aerosol reactors. Properties of nanoparticle chain aggregates (NCA), such as restructuring when heated in gaseous suspension, may play an important role during synthesis. It is hypothesized that in some cases a separate step in NCA creation is the restructuring of the chains initially formed by rigid body addition processes, for example cluster–cluster aggregation. A model of a freely rotating bead chain (zero activation energy for particle rotation) is adapted here from the polymer literature to describe nanoparticle chain restructuring resulting from interaction with the surrounding gas. The link between the physical properties of the surrounding gas and the dynamics of the nanoparticle chain is provided through the diffusion coefficient of the chain center of mass. We have studied the restructuring dynamics for primary particles of various diameters, different chain lengths and at different temperatures, and the model predicts a fast transition from a non-equilibrium initial chain configuration to a relaxed state. For a stretched chain of 64 particles, each 35nm in diameter, in air at 1800K and atmospheric pressure, the characteristic time for relaxation was 0.34ms. This time is consistent with a 12ms upper limit in restructuring time for soot aggregates reported in the literature. It is possible that in practice the approach to equilibrium may be delayed by constraints on particle rotation.

Nanoparticle chain aggregates (NCA) serve as reinforcing fillers that are combined with molecular polymers to produce nano-composite materials, e.g. carbon black in rubber. The reinforcing mechanism due to the incorporation of nanoparticle aggregates is not well understood. Molecular dynamics (MD) computer simulations are employed to investigate the behavior of nanoparticle chain aggregates under strain. The interaction potential used is that of Cu obtained with the embedded atom method (EAM). Three single-crystal Cu nanoparticles are placed in contact in two different configurations (linear and kinked) and the structures are initially relaxed with MD steps for 300 ps. We observe plastic deformation during the sintering process for very small particles (∼2.5 nm in diameter) at temperatures as low as 300 K. The relaxed configurations are then strained to the breaking point at strain rates in the order of 1 m/s. We identify mechanisms of strain accommodation that lead to nanoparticle plastic deformation and eventually fracture. The linear and the kinked configurations break at strains of 0.263 and 0.344 respectively, while the maximum stress is close to 4 GPa (strain rate: 0.625 m/s). Both structures fail at the low-angle grain boundaries developed during the sintering process, while the higher strain for fracture for the kinked configuration is associated with interface sliding not observed in the linear case.