We present a novel method for the direct metal-free growth of graphene on sapphire that yields high quality films comparable to that of graphene grown on SiC by sublimation. Graphene is synthesized on sapphire via the simple decomposition of methane at 1425-1600 °C. Film quality was found to be a strong function of growth temperature. The thickness, structure, interface characteristics, and electrical transport properties were characterized in order to understand the utility of this material for electronic devices. Graphene synthesized on sapphire is found to be strain relieved, with no evidence of an interfacial buffer layer. There is a strong correlation between the graphene structural quality and carrier mobility. Room temperature Hall effect mobility values were as high as 3000 cm(2)/(V s), while measurements at 2 K reached values of 10,500 cm(2)/(V s). These films also display evidence of the quantum Hall effect. Field effect transistors fabricated from this material had a typical current density of 200 mA/mm and transconductance of 40 mS/mm indicating that material performance may be comparable to graphene on SiC.

We report a direct correlation between carrier mobility and Raman topography of epitaxial graphene (EG) grown on silicon carbide (SiC). We show the Hall mobility of material on the Si-face of SiC [SiC(0001)] is not only highly dependent on thickness uniformity but also on monolayer s st tr ra ai in n uniformity. Only when both thickness and strain are uniform over a significant fraction (> 40%) of the device active area does the mobility exceed 1000 cm 2 /V-s. Additionally, we achieve high mobility epitaxial graphene (18,100 cm 2 /V-s at room temperature) on the C-face of SiC [SiC(000-1)] and show that carrier mobility depends strongly on the graphene layer stacking. These findings provide a means to rapidly estimate carrier mobility and provide a guide to achieve very high mobility in epitaxial graphene. Our results suggest that ultra-high mobilities (>50,000 cm 2 /V-s) are achievable via the controlled formation of uniform, rotationally faulted epitaxial graphene.The recent success of graphene transistor operation in the giga-hertz range has solidified the potential of this material for high speed electronic applications. 1,2 Realization of graphene technologies at commercial scales, however, necessitates large-area graphene production, as well as the ability to rapidly characterize its structural and electronic quality. Graphene films can be produced by mechanical exfoliation from bulk graphite, 3,4 reduction of graphite-oxide, 5,6 chemical vapor deposition on catalytic films, 7 or via Si-sublimation from bulk SiC substrates. 8 9, -10,11, 12 The last technique currently appears to hold the most promise for large-area electronic grade graphene, and already shows tremendous potential for high-frequency device technologies. 2 Nevertheless, precise control of the graphene electronic properties (i.e. mobility) over large areas is necessary to enable graphene-based technological applications. Realization of such control will come through an intimate understanding of the process-propertyperformance relationship and the role that graphene thickness, strain, and layer stacking plays in this relationship over very large areas up to full wafers. Of the characterization techniques used for layer thickness determination, 13 ,14,15, -16,17,18, 19 Raman spectroscopy is arguably the simplest and fastest, especially for exploring monolayer EG on SiC(0001) (referred to as EG Si )and EG layer stacking on SiC(000-1) (referred to as EG c ). [15][16][17][18][19] Characterization of EG via Raman spectroscopy requires fitting the 2D Raman peak. 15,16,20 Raman spectra of EG Si fit by one or four Lorentzian functions are characteristic of monolayer or bilayer graphene, respectively. 15 Figure 1a demonstrates layer thickness evaluation for monolayer and bilayer EG Si via Lorentzian fitting of the 2D Raman spectra. To further validate these thickness measurements, cross-sectional transmission electron microscopy (TEM) was performed (Fig. 1b,c). The TEM micrographs in Fig.1b,c include a transition layer (Layer 0), which is in dire...

It is increasingly recognized that macro-organisms (corals, insects, plants, vertebrates) consist of both host tissues and multiple microbial symbionts that play essential roles in their host's ecological and evolutionary success. Consequently, identifying benefits and costs of symbioses, as well as mechanisms underlying them are research priorities. All plants surveyed under natural conditions harbor foliar endophytic fungi (FEF) in their leaf tissues, often at high densities. Despite producing no visible effects on their hosts, experiments have nonetheless shown that FEF reduce pathogen and herbivore damage. Here, combining results from three genomic, and two physiological experiments, we demonstrate pervasive genetic and phenotypic effects of the apparently asymptomatic endophytes on their hosts. Specifically, inoculation of endophyte-free (E−) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant FEF species in healthy T. cacao, induces consistent changes in the expression of hundreds of host genes, including many with known defensive functions. Further, E+ plants exhibited increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes. These phenotypic changes observed in E+ plants correspond to changes in expression of specific functional genes in related pathways. Moreover, a cacao gene (Tc00g04254) highly up-regulated by C. tropicale also confers resistance to pathogen damage in the absence of endophytes or their products in host tissues. Thus, the benefits of increased pathogen resistance in E+ plants are derived in part from up-regulation of intrinsic host defense responses, and appear to be offset by potential costs including reduced photosynthesis, altered host nitrogen metabolism, and endophyte heterotrophy of host tissues. Similar effects are likely in most plant-endophyte interactions, and should be recognized in the design and interpretation of genetic and phenotypic studies of plants.

We report results from two-dimensional Raman spectroscopy studies of large-area epitaxial graphene grown on SiC. Our work reveals unexpectedly large variation in Raman peak position across the sample resulting from inhomogeneity in the strain of the graphene film, which we show to be correlated with physical topography by coupling Raman spectroscopy with atomic force microscopy.We report that essentially strain free graphene is possible even for epitaxial graphene.Graphene exhibits extraordinary electronic properties including an unusually high mobility of the charge carriers. 1 While significant progress toward understanding the properties of graphene has resulted from studying graphene flakes mechanically exfoliated from bulk graphite, 2 these small flakes (< 100 µm 2 ) are most suited for studying the fundamental science of graphene, and are not practical for the development of graphene-based technologies. Alternatively, the sublimation of silicon (Si) from silicon carbide (SiC) to form epitaxial graphene is a promising route for the production of wafer size graphene films. 3 -45678 9 However, rapid characterization and precise control of properties of epitaxial graphene over a wafer-size area are yet to be achieved. Micro-Raman spectroscopy is a rapid, highresolution optical characterization technique that yields important information on the thickness, the charge carrier density, and the strain of epitaxial graphene. 10,11,12,13 However, no studies of Raman topography, the two-dimensional mapping of Raman spectrum over large-area epitaxial graphene, have been carried out to date.

The aim of this study was to compare three methods of adjusting skeletal data for body size and examine their use in QTL analyses. It was found that dividing skeletal phenotypes by body mass index induced erroneous QTL results. The preferred method of body size adjustment was multiple regression.Introduction: Many skeletal studies have reported strong correlations between phenotypes for muscle, bone, and body size, and these correlations add to the difficulty in identifying genetic influence on skeletal traits that are not mediated through overall body size. Quantitative trait loci (QTL) identified for skeletal phenotypes often map to the same chromosome regions as QTLs for body size. The actions of a QTL identified as influencing BMD could therefore be mediated through the generalized actions of growth on body size or muscle mass. Materials and Methods: Three methods of adjusting skeletal phenotypes to body size were performed on morphologic, structural, and compositional measurements of the femur and tibia in 200-day-old C57BL/6J × DBA/2 (BXD) second generation (F 2 ) mice (n ‫ס‬ 400). A common method of removing the size effect has been through the use of ratios. This technique and two alternative techniques using simple and multiple regression were performed on muscle and skeletal data before QTL analyses, and the differences in QTL results were examined. Results and Conclusions:The use of ratios to remove the size effect was shown to increase the size effect by inducing spurious correlations, thereby leading to inaccurate QTL results. Adjustments for body size using multiple regression eliminated these problems. Multiple regression should be used to remove the variance of co-factors related to skeletal phenotypes to allow for the study of genetic influence independent of correlated phenotypes. However, to better understand the genetic influence, adjusted and unadjusted skeletal QTL results should be compared. Additional insight can be gained by observing the difference in LOD score between the adjusted and nonadjusted phenotypes. Identifying QTLs that exert their effects on skeletal phenotypes through body size-related pathways as well as those having a more direct and independent influence on bone are equally important in deciphering the complex physiologic pathways responsible for the maintenance of bone health.

Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, we show direct evidence of inhomogeneous Nd(3+) distribution across grain boundaries (GBs) in Nd(3+):YAG laser ceramics. It is clearly shown that Nd(3+) segregation takes place at GBs leading to self-fluorescence quenching which affects a volume fraction as high as 20%. In addition, we show a clear trend of increasing spatial inhomogeneities in Nd(3+) concentration when the doping levels exceeds 3 at%, which is not detected by standard spectrometry techniques. These results could point the way to further improvements in what is already an impressive class of ceramic laser materials.

A single beam laser interferometer based on a modified Mirau detection scheme with a vertical resolution of 5 pm was developed for localized d33 measurements on patterned piezoelectric films. The tool provides high spatial resolution (2 lm), essential for understanding scaling and processing effects in piezoelectric materials. This approach enables quantitative information on d33, currently difficult in local measurement techniques such as piezoresponse force microscopy. The interferometer is built in a custom microscope and employs a phase lock-in technique in order to detect sub-Angstrom displacements. d33 measurements on single crystal 0.67PbMg0.33Nb0.67O3-0.33PbTiO3 and bulk PbZrTiO3-5A ceramics demonstrated agreement within <3% with measurements using a double beam laser interferometer. Substrate bending contributions to out-of-plane strain, observed in thin continuous PbZr0.52Ti0.48O3 films grown on Si substrates is reduced for electrode diameters smaller than 100 lm. Direct scanning across room temperature and 150 C poled 5 lm and 10 lm features etched in 0.5 lm thick PbZr0.52Ti0.48O3 films doped with 1% Nb confirmed minimal substrate contributions to the effective d33,f. Furthermore, enhanced d33,f values were observed along the feature edges due to partial declamping from the substrate, thus validating the application of single beam interferometry on finely patterned electrodes.

Sufficient variation exists in how people smoke each cigarette that the number of cigarettes smoked daily and the years of smoking represent only crude measures of exposure to the toxins in tobacco smoke. Previous research has shown that spent cigarette filters can provide information about how individuals smoke cigarettes. Digital image analysis has been used to identify filter vent blocking and may also provide an inexpensive, unobtrusive index of overall smoke exposure. A total of 1,124 cigarette butts smoked by 53 participants in a smoking topography study were imaged and analyzed. Imaging showed test-retest reliability of more than 95% among those smoking their own brand. Mean color scores (CIELAB system) showed acceptable stability (>.60) across days, paralleling the basic stability of smoking topography measures across waves. A principal components scoring showed that center tar staining, edge tar staining, and their interaction were significantly related to total smoke volume, accounting for 73% of the variation. Estimated smoke volume was a significant predictor of salivary cotinine when accounting for cigarettes smoked per day. These data suggest that digital image analysis of spent cigarette butts can serve as a reliable proxy measure of total smoke volume.