Volume 85, Issue 8, 15 April 1999
Index of content:
- CLASSICAL PHENOMENOLOGY: ELECTRICITY, MAGNETISM, OPTICS, ACOUSTICS, HEAT, MECHANICS (PACS 41-52)
85(1999); http://dx.doi.org/10.1063/1.370294View Description Hide Description
The spontaneous emission factor β is an important parameter for the characterization of semiconductorlight emitting devices. In the analysis of superluminescent diodes, especially in the calculation of the optical intensity using rate equations, most authors have used the estimated value of β taken from laser diodes, despite the conceptual difference involved in each device. In this article, the spontaneous emission factor β for superluminescent diodes is discussed in detail, and a new method in calculating the average value of β is introduced. Based on this method, the values of β for gain-guided and index-guided structures are obtained.
A theoretical model for neutral velocity distributions at a planar target in plasma source ion implantation85(1999); http://dx.doi.org/10.1063/1.370295View Description Hide Description
A theoreticalmodel is developed to study the velocity distributions of neutrals striking a planar target in plasma sourceion implantation (PSII) for the case in which the pressure of the gas is large enough that the fast neutrals can be produced in the sheath by ion-neutral charge exchangecollisions. An analytic expression for the neutral velocity distribution at the target is provided. The theoretic results agree with Monte Carlo simulations.
production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization85(1999); http://dx.doi.org/10.1063/1.370296View Description Hide Description
The study of CF and radical production and loss mechanisms in capacitively-coupled 13.56 MHz plasmas has been extended to plasmaswith an Si substrate, and to plasmas, conditions where the atomic fluorine concentration is lower and where more polymerdeposition occurs on the reactor surfaces. Processes in the gas phase and at the reactor surfaces were investigated by time resolved axial concentration profiles obtained by laser induced fluorescence, combined with absolute calibration techniques. The results for CF were similar to those observed in the fluorine rich case, whereas the results for were strikingly different and more complex. This paper focuses on the radical, which, under these conditions is produced at all of the surfaces of the reactor, apparently via a long-lived surface precursor. The results can only be explained if large polymeric ions and/or neutrals are produced by polymerization in the gas phase. The gas-phase concentration is high, causing the otherwise slow gas-phase concatenation reactions to occur. These processes produce high-mass neutrals (and ions) which are the real polymer precursors. The radical therefore circulates in a closed cycle between the surface and the gas phase. The degree of polymerization is controlled by the fluorine atom concentration, which simultaneously controls the concentrations of of chain initiating species such as and of dangling bonds on the growing oligomers. This model appears to apply to fluorocarbon discharges in general, and agrees well with other results presented in the literature.
85(1999); http://dx.doi.org/10.1063/1.370297View Description Hide Description
The speed of conversion of infrared (IR) images by a planar semiconductorgas discharge system into the visible range has been investigated. Argon or nitrogen are used in the discharge gap having an electrode distance of 100 m. Using pulse radiation from an IR laser to excite the system, we have shown that the characteristic response time of the device with the cryogenic discharge in the gap can lie in the submicrosecond range. This characteristic of the system can be applied for a fast IR imaging at a rate higher than frame/s.
Ion energy distributions and sheath voltages in a radio-frequency-biased, inductively coupled, high-density plasma reactor85(1999); http://dx.doi.org/10.1063/1.370298View Description Hide Description
Ion energy distributions were measured at a grounded surface in an inductively coupled, high-density plasma reactor for pure argon, argon–helium, and argon–xenon discharges at 1.33 Pa (10 mTorr), as a function of radio-frequency (rf) bias amplitude, rf bias frequency, radial position, inductive source power, and ion mass. The ground sheath voltage which accelerates the ions was also determined using capacitive probe measurements and Langmuir probe data. Together, the measurements provide a complete characterization of ion dynamics in the sheath, allowing ion transit time effects to be distinguished from sheath impedance effects. Models are presented which describe both effects and explain why they are observed in the same range of rf bias frequency.