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991.
Optical and microstructural properties of diamond-like carbon films grown by pulsed laser deposition
《Diamond and Related Materials》2007,16(1):149-154
Diamond-like carbon films have been fabricated using 308 nm excimer laser ablation in vacuum followed by deposition at temperatures between 77 K and 573 K. Optical band gap energies are obtained from UV/optical spectroscopy. Raman spectra and X-ray photoelectron spectra (XPS) show that the sp3/(sp2 + sp3) ratio in these films is in excess of 0.7 in films deposited at 77 K and 300 K. This ratio decreases to 0.2 in films deposited at 573 K. It is found that films deposited at cryogenic temperatures consist of a matrix structure assembled from embedded nanometer clusters, while films deposited at 300 K or higher temperature are amorphous and atomically flat. Microstructural features in cryogenic films are discussed in relation to the mechanism of deposition and possible phase transitions during assembly of these films. 相似文献
992.
993.
994.
A study of dislocation configurations in superconducting oxide BiSrCaCuO has been made by transmission electron microscopy. Evidence was found for the presence of dislocation pairs composed of two parallel single dislocations holding together with the same Burgers vectors. The pair can further dissociate into partials, giving rise to a four-fold ribbon. Networks consisting of dislocation pairs were also observed. These phenomena are attributed to the possible ordering of strontium and calcium ions and the existence of some oxygen sheet of the Aurivillius type in the oxide crystal. Schemes to illustrate the configurations are suggested and discussed. 相似文献
995.
Sherif Sedky 《Microelectronic Engineering》2007,84(11):2491-2500
This work gives an overview of the different developments for silicon germanium (Si1−xGex) from a MEMS post-processing perspective. First, the maximum processing temperature that does not introduce any damage or degradation into the standard characteristics of the CMOS driving electronics is specified. Then, the optimal type of silicon and germanium gas sources and deposition technique that results in an economical process are identified. Next, the selection criteria for a low thermal budget doping method and doping species are discussed. Finally, the advantage and disadvantage for the different approaches implemented for enhancing the physical properties of poly Si1−xGex at a CMOS backend compatible temperature are highlighted. It is shown that the optimal method depends on the application requirements and the CMOS technology used for realizing the driving electronics. 相似文献
996.
《钢铁研究学报(英文版)》2006
The time dependence of magnetization is usually expressed as M(t)=M0-SInt [see Proc. Phys. Soc. 62, 562 (1949)] for magnetic viscosity experiments. Considering magnetic interaction during the thermal activation process, a form as M(t)=M0-SIn(t+t0) is deduced. The dipolar interaction and exchange coupling in a magnet can lead to positive and nonpositive t0, respectively. In the experiments of the magnetic viscosity for nanocrystalline Pr2Fe14B ribbons, the existence of positive t0 is confirmed. 相似文献
997.
《Diamond and Related Materials》2007,16(4-7):836-839
We report experimental evidence of a substantial reduction of the sheet resistance of a commercially available (110) oriented natural diamond surface after exposure not to atomic but to molecular hydrogen. In a conventional CVD reactor, we have merely exposed the sample to high purity molecular hydrogen fluxes at 800 °C. After exposure to air, the surface conductivity increased several orders of magnitude as measured by a professional collinear four-point probe head with tungsten carbide tips. After annealing at 900 °C in vacuum (P < 10− 5 Pa) the conductivity dropped at least 4 orders of magnitude; repeatability tests on the measurements of the surface conductivity after thermal hydrogenation and subsequent air exposure were conducted in order to avoid systematic errors. Similar experiments were conducted at different process temperatures in order to evaluate the best process conditions. Thermal hydrogenation appears to be ineffective at increasing the surface conductivity of (100) homoepitaxial CVD diamonds. 相似文献
998.
The granular ceramic materials corundum and mullite are potential filter bed materials for electrically enhanced filtration
at elevated temperatures. The dielectric response of the granular ceramics has been determined at temperatures between 420
and 920 K. It is shown that the response of these materials can be described by one equivalent circuit over the whole temperature
and frequency (0.1 Hz–10 kHz) range. Thermally activated conduction in parallel with a dipole relaxation with a symmetrical
logarithmic distribution of relaxation times (Cole-Cole relaxation) is the mechanism which determines the response at not
too low frequencies. 相似文献
999.
A direct measurement of the dynamics of electrons in the X6 valley for a GaAs crystal by time-resolved absorption spectroscopy is reported for the first time. IR picosecond probe pulses were used to monitor the growth and decay of the population in the X6 valley subsequent to excitation by a 527 nm pump pulse. The intervalley X6→Γ6, L6 scattering time tx of 0.70 ± 0.50 ps is determined and the crossection for the X6→X7 transition is estimated to be 1.8 × 10−16 cm2. 相似文献
1000.
The costs of remedial work, and the radon level reduction achieved, have been studied in a series of domestic properties in Northamptonshire, which is a radon affected area. The cost-effectiveness of the series is similar to published theoretical estimates for proposed national remediation programmes, and five times more effective than our similar analysis for the National Health Service workplace, if it is assumed that 100% of householders discovering levels above 300 Bq m-3 implement remediation. In practice, in the UK, far fewer of those who arrange an initial radon test proceed to remediation, but this domestic programme could be cost effective if more than 5% carry out remediation. Our series confirms that a considerable number of householders with radon levels in the 200 to 300 Bq m-3 range do not seek or implement remediation work. 相似文献