We synthesized carbon nanowalls (CNWs) using radical injection plasma-enhanced chemical vapor deposition. The initial growth process of CNWs was investigated with and without O2 gas addition to a C2F6 capacitively coupled plasma with H radical injection. In the case of the CNW synthesis without the addition of O2 gas, scanning electron microscopy (SEM), transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy revealed that a 10-nm-thick interface layer composed of nanoislands was formed on a Si substrate approximately 1 min prior to CNW formation. In contrast, with O2 gas addition, SEM and XPS revealed that an interface layer was not formed and that CNWs were grown directly from nanoislands. Moreover, Raman spectroscopy suggested that the interface layer was composed of amorphous carbon and that O2 gas addition during CNW growth is effective for achieving a high graphitization of CNWs. Therefore, O2 gas addition has the effect of reducing the amorphicity and disorder of CNWs and controlling CNW nucleation.

Two-dimensional carbon nanostructures, carbon nanowalls (CNWs), were fabricated on a Si substrate using radical injection plasma-enhanced chemical vapor deposition, employing fluorocarbon (C2F6) and hydrogen (H2) mixtures. The influence of the surface conditions of the chamber wall on CNW growth was investigated in order to determine the optimum conditions for CNW growth with high stability and reproducibility. In order to monitor the surface conditions of the chamber wall, optical emission spectroscopy in the plasma was measured, and the correlation between CNW growth and the surface conditions in the chamber wall was investigated. The growth rate and morphology of grown CNWs were determined to be influenced by the surface conditions of the chamber wall. Furthermore, O2 plasma chamber cleaning followed by predeposition for passivation was found to be effective for maintaining steady conditions to attain CNWs with high reproducibility.

The key issue in GaN growth by radio‐frequency plasma‐assisted molecular beam epitaxy is the low growth rate compared with that obtained using an ammonia source. To reduce the processing time and to improve the crystalline quality of the epilayer, a high‐density radical source (HDRS) with high stability has been developed. The growth rate of the GaN epilayer was improved using the HDRS rather than a conventional radical source. During the growth, a sharp streak pattern obtained by reflection high‐energy electron diffraction was maintained. An atomically smooth surface was confirmed by atomic force microscopy observation (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Parameters have been specified for electron beams with energies 5-45 MeV from a Brown Boveri betatron for use in computerised dosimetry calculations. A semi-empirical equation is given for the dose a t any point at various depths in water. This equation is a modification to Kawachi's predictive model which was based on solutions of a general age-diffusion equation. The depth doses and isodose curves are predicted as a function of the practical range, source skin distance (SSD) and field size. Depth dose accuracy requirements of f 2y0 above 50% depth dose and +_5% at lower doses, relative to maximum dose, have been set and achieved. Also, the shape of the isodose curves with the constrictions at higher doses and bulging a t lower values are accurately predicted. Computer calculated beams have been used to generate summed isodose distributions for certain clinical situations.

Articles you may be interested inThe multipole resonance probe: A concept for simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure plasmas Appl. Phys. Lett. 93, 051502 (2008); 10.1063/1.2966351Floating probe for electron temperature and ion density measurement applicable to processing plasmas Electrostatic probe diagnostics of a planar-type radio-frequency inductively coupled oxygen plasma Atomic radicals such as hydrogen ͑H͒ and oxygen ͑O͒ play important roles in process plasmas. In a previous study, we developed a system for measuring the absolute density of H, O, nitrogen, and carbon atoms in plasmas using vacuum ultraviolet absorption spectroscopy ͑VUVAS͒ with a compact light source using an atmospheric pressure microplasma ͓microdischarge hollow cathode lamp ͑MHCL͔͒. In this study, we developed a monitoring probe for atomic radicals employing the VUVAS with the MHCL. The probe size was 2.7 mm in diameter. Using this probe, only a single port needs to be accessed for radical density measurements. We successfully measured the spatial distribution of the absolute densities of H and O atomic radicals in a radical-based plasma processing system by moving the probe along the radial direction of the chamber. This probe allows convenient analysis of atomic radical densities to be carried out for any type of process plasma at any time. We refer to this probe as a ubiquitous monitoring probe for atomic radicals.