tunable thermal conductivity of si1 xgex nanowires

... Dynamics 69 Tunable Thermal Conductivity of Si1 x Gex Nanowires 75 3.1 76 3.2 Si/Ge Randomly Doped Nanowires 77 3.3 Si/Ge Superlattice Nanowires ... demonstrate that thermal conductivity of SiNWs can be effectively reduced by randomly doping Ge atoms The composition dependence of thermal conductivity in Si-Ge nanowires is explained in terms of localization ... 052301 (2009) xi List of Tables 2.1 EMD simulation results for thermal conductivity of crystalline silicon at 1000 K 62 3.1 The fitting parameters of thermal conductivity for...

Ngày tải lên: 10/09/2015, 08:38

... the synthesis and luminescence of Si nanowires obtained by a simple thermal evaporation of molybdenum disilicide (MoSi2 ) heating rods Each nanowires consists of a single crystalline core covered ... peripheries of the nanowire, which leads to the coaxial core-shell structure TEM observation of several tens of such nanowires reveal that the diameter of the core and the thickness of the shell ... of the nanowires The morphology and structure of the as-prepared products have been characterized in detail using TEM and selected area electron diffraction (SAED) Two major forms of silicon nanowires...

Ngày tải lên: 16/03/2014, 15:08

... size of the H bubbles to the critical value for their explosion and formation of craters The results of this study would confirm that the origin of the structural degradation of the MLs of a-Si/a-Ge ... Hungarian Academy of Sciences, P.O Box 49, H-1525 Budapest, Hungary 3Institute of Nuclear Research of the Hungarian Academy of Sciences, P.O Box 51, H4001 Debrecen, Hungary 4Department of Solid State ... obtained for a-Ge By using the simulation program of ref [11], the calibration curves of Figure 2b giving the incorporated at.% of H as a function of the H flow rate were obtained The increase in...

Ngày tải lên: 21/06/2014, 05:20

Ngày tải lên: 21/06/2014, 06:20

... stages of growth with a rate of -10°C/sec, and then transferred under UHV to the attached STM chamber Imaging was performed at tunneling currents of around 0.1 nA and applied sample bias of 2–4 ... have been found to be one of the major low-energy surfaces of silicon [21, 22], meaning that the sidewall facettation leads to a lowering of the total surface energy of the system After 20 nm ... depicted below the ridges and filling of the grooves (see STM image of Fig 3), which decreases the amount of (001) surface area on the stripes Toward the end of buffer growth at 520°C, however,...

Ngày tải lên: 21/06/2014, 08:20

... number of atoms of core–shell nanowires are fixed to be 2524 The ˚ unit of the length is in a Table The optimal structural parameters of Si-core/Ge-shell nanowires Radius of core Outer radius of shell ... case of ZnO nanowires in experiment [15] Although there have been an increasing work devoted to Young’s modulus of nanowires [16–18], there are few studies on Young’s modulus of core–shell nanowires ... work is partially supported by the Fund of University of Science and Technology of China, the Fund of Chinese Academy of Science, and by NSFC with code number of 50121202, 60444005, 10574115 and...

Ngày tải lên: 16/03/2014, 15:22

... Page of case of Si and to the value of 1.5 × 1014 cm-2 s-1 in the case of Ge, to obtain the same velocity of growth of the planar films, set at a constant value of 0.05 nm s-1 The evaporated fluence ... SEM images of Si NWs and Ge NWs (a) Lowmagnification SEM images of sample of Si NWs The bottom inset shows a higher magnification of a Si NW The top inset is a crosssectional SEM image of the sample ... presence of a dip around the NWs Page of clearly demonstrates that the atoms missing from the planar layer act as a sort of reservoir contributing to the axial growth of the NWs The surface area of...

Ngày tải lên: 21/06/2014, 05:20

Ngày tải lên: 14/03/2014, 13:20

... not be formed very well on the surface of nanowires because of both the volume change of the nanowires and breaking of the carbon network sheathed on the nanowires When the substrate temperature ... image of a nanowire consisting of a crystalline Si core and a sheath of multi-walled CNTs; (b) a nanowire with a part of the core transformed into b-SiC and coated with a sheath of CNTs b-SiC nanowires ... image of the nanowires with carbon deposition at $1300°C and the higher magni®cation image of a part of the sample in the upper image feather-like carbon sheets sprouting from the surface of the nanowires...

Ngày tải lên: 16/03/2014, 15:04

... very difficult The objectives of this work, after getting a mount of nanowires by thermal physical evaporation, are to study the IR absorption characteristics of SiO2 /Si nanowires and the nanostructural ... growth of silicon nanowires After being ground in a mortar, the Si powder was pre-sintered at 1150 °C for h in a vacuum of 10À5 Pa The growth of silicon nanowires was conducted by a modified thermal ... 0.5 cmÀ1 in the range of 400–4000 cmÀ1 Results and discussion After the fabrication of silicon nanowires by the thermal evaporation method, products with different sizes of nanowires and surface...

Ngày tải lên: 16/03/2014, 15:05

... 9308C After 12 h of thermal evaporation, Si Fig Ža TEM image showing the morphology of Si nanowires synthesized by the evaporation method Žb – Žd Nucleation stage of the Si nanowires N Wang ... the appearance of Ä 1114 surfaces of the Si crystals parallel to the axes of the nanowires reduces the system energy Combined, these factors determine the growth direction of Si nanowires to be ... Letters 299 (1999) 237–242 bulk-quantity Si nanowires were synthesized by thermal evaporation of a highly pure Si powder mixed with SiO Observations of Si nanowire nucleation and growth morphology...

Ngày tải lên: 16/03/2014, 15:08

... typical morphology of the materials in the yellow web It can be seen that the product consists of nanowires with an average diameter of 14 nm Most of the SiNWs are consist of straight and smoothly ... morphology is a common characteristic of various nanowires, such as SiC nanowires w15x and carbon nanowires w16x Although the nanowires have a high ratio of length to diameter, the diameter remains ... diagram of the laser ablation apparatus Fig Morphology of Si nanowires taken from the yellow product Ža Low-magnitude TEM image of Si nanowires The inset is SAED pattern Žb HRTEM image of a typical...

Ngày tải lên: 16/03/2014, 15:08

... formation of cavities with lowest energy {1 1} symmetry planes Extrusion of material during such collapse of the Si(1 0) surface lattice seems to be the process leading to nucleation of Si nanowires ... along the {1 1} plane walls Disproportionation of Si monoxide seems to be the key reaction for the formation of Si nanowires by thermal evaporation of pure SiO [23] or mixed Si–SiO2 [24] powders ... inside one of the ÔsquaresÕ in Fig and is shown for the sake of comparison SiC/Si interfaces revealed mostly smooth walls without any evidence of nanosized structures protruding out of the surface...

Ngày tải lên: 16/03/2014, 15:08

... surface of the Si wafer changed to light yellow SEM image (Fig 2d) of the after-grown Si wafer demonstrates that there are many thin and straight nanowires covering the surface of the Si wafer The nanowires ... the concentration is supersaturated The diameter of the Si nanowires is similar to the size of the CuSi alloy nanoparticles So the tip of the Si nanowires is polyhedron, not the ball-like tip with ... for the formation of Si nanowires The cheap Cu catalyst and the low growth temperature are favorable to the mass synthesis of the Si nanowires Conclusion Acknowledgements The Si nanowires could...

Ngày tải lên: 16/03/2014, 15:12

... image of Si nanoparticles after heat treatment at 980 °C without Fe catalysts and (b) nanowires with Fe, (c) TEM image showing nanopartical catalysts at the end of nanowires (d) TEM image of an ... showing catalysts at the end of nanotubes, (b) TEM image of an individual nanotube and SAED pattern investigate the structure and morphology of the Si nanoparticles and nanowires Results and discussion ... transformed into nanowires if there was no iron catalysts as shown in Fig 3(a) When introduced iron catalysts, Si nanowires came out Fig 3(b) shows the TEM images of SiNWs with tens of nanometer...

Ngày tải lên: 16/03/2014, 15:13

... morphology of SiOx nanowires (Arrow 1: helical nanowires or nanosprings; Arrow 2: nanoparticles) The lower right inset of (a) is the SAED pattern of SiOx nanowires (c) HRTEM image of a single ... consists of aggregates of nanowires Although most nanowires have straight or smoothly curved morphology, some nanowires indicated by arrow exhibit the helical structure (Fig 2a) The similar helical nanowires ... indicate that the nanowires have diameters in the range of 20–80 nm XRD, SAED, and EDX analyses reveal that the nanowires are amorphous and consist only of silicon oxide The growth of SiOx nanowires...

Ngày tải lên: 16/03/2014, 15:14

... bright tips of the NWs seem to be Au–Si droplets in Fig 1(d) The diameters of the NWs are similar to those of the Au–Si droplets The existence of a critical Au film thickness for initiation of NW nucleation ... nucleation of the NWs [10] For the 2.0 nm film, similar NP structures were observed However, for the 3.0 nm film we observed the nucleation of the Si-NWs with average diameter of 60 nm and length of 350 ... transformation of the liquid into Au–Si alloy droplet structures, whose shape is determined by minimization of the surface and interface energy of the liquid/substrate Also, the composition of the Au–Si...

Ngày tải lên: 16/03/2014, 15:15

... supersaturation of the liquid Au–Si eutectic droplets by the continuous supply of Si atoms from the substrate results in the formation of SiOx nanowires, instead of Si nanowires, due to the lack of vacuum ... formation of nanowires Fig shows FE-SEM images revealing the general morphologies of SiOx nanowires grown on Au/Si and Pd–Au/Si substrates at 1050 1C As shown in the FE-SEM images, a large number of nanowires ... nanowires with lengths of tens of 159 micrometers and diameters around 100 nm were formed on the Pd–Au/Si substrate surface, while a small number of nanowires with lengths of a few micrometers...

Ngày tải lên: 16/03/2014, 15:16

... works on the growth of silicon nanowires from indium by means of PVD were found In our case, the growth of nanowires from indium seems to be rather insensitive to change of parameters like substrate ... distribution by annealing nm of indium at a growth temperature of 570 1C He did not get any nanowires after flooding the chamber with diluted silane and explained the absence of nanowires by considering ... effects of different diffusion coefficients of gold and indium on silicon, the solubility of substrate atoms in the two metals, the surface tension of gold and indium and the surface energy of silicon...

Ngày tải lên: 16/03/2014, 15:17

... other parts of a nano-object, here most intensive decomposition of an active gas takes place and the highest concentration of mobile silicon atoms or dopants is maintained The control of further ... simulation by numerical solution of the rate equations, (ii) to reproduce some key stages of a real physical experiment Besides, we will demonstrate a number of advantages of ‘‘the multilevel simulation’’ ... case (iii) We simulated the behavior of a system consisting of two kinds of atoms with strongly differing mobilities We observed a non-steady-state kinetics of mobile atoms, which left the catalyst...

Ngày tải lên: 16/03/2014, 15:18