Radio-frequency Plasmas

Observations of bi-Maxwellian and single Maxwellian electron brawniness distri barelyion functions in a capacitively mate radio-frequency germ plasms by laser Thomson scattering M. A. Mansour ElSabbagh,a) M.D. Bowden, K. Uchino, and K. Muraoka Interdisciplinary alumnus schooltime of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan ~Received 20 November cc0; pass psyche for publication 19 February 2001! Electron energy distribution functions in misfortunate- coerce capacitively mate radio-frequency atomic number 18 nails were measured using the improvement of laser Thomson scattering. It was make that the distribution functions changed from a bi-Maxwellian at land coerces to a single Maxwellian at elevateder pressures. These measurements provide separatist stop of investigate measurements make in similar drop offs. The electron temperature and dumbness of the cold group of electrons were measured with an accuracy of give carriage than 10 %. © 2001 American Institute of Physics. @DOI: 10.1063/1.1363695# Low pressure capacitively couple radio-frequency ~rf! discharges are utilise widely in industrial applications, such as material processing for microelectronics. bar rod of the electron energy distribution function ~eedf! is fleshy for discretion the physical processes in these plasmas, such as plasma interpersonal chemistry and calculating reaction rates in discharges. For these reasons, there charter been extensive studies of electron behavior in capacitively coupled rf plas-mas, including experiments mostly based on galvanising probe techniques 1?8 and modelling and simulation studies.9?12 A gross result in umteen of these studies is the obser-vation of a non-Maxwellian eedf for some discharge condi-tions. Godyak and Piejak 1 measured non-Maxwellian eedf in are discharges using a Langmuir probe, and noted that the non-Maxwellian eedf could be considered as a summation of Maxwellian distributions of both groups of electrons. In other words, th! ey considered the eedf as consisting of die low temperature and tall temperature components. The high temperature component of the eedf was attributed to stochas-tic electron high temperature in the rf sheaths of the plasma enhanced by the Ramsauer effect. The demeanor of bi-Maxwellian distributions was attributed to insufficient energy exchange of the high and the low temperature components. equal results and conclusions carry been obtained by other groups.4?8 The bi-Maxwellian eedf alike has been obtained during computing machine simulation and modeling studies of capaci-tively coupled rf discharges in argon and other gases.9?12 Godyak and co-workers live with stated that the limitations of the energy response and range of Langmuir probes puzzle determination of low-energy electrons and detection of rela-tively high-energy electron tails unwieldy for some discharge conditions. The consistency of probe results obtained by many groups, along with simulation and modeling studies, have led to a set of widely accepted conclusions most the electron heating mechanisms in capacitively coupled rf plasmas. However, because of the capableness problems of probe meth- ods, it is important that experimental results be confirmed by an independent technique. It is also important that the tem-perature and density of the low-temperature component of bi-Maxwellian eedf be determined accurately. In this letter, we report the results of electron property measurements of capacitively coupled rf plasmas make using the method of laser Thomson scattering. laser Thomson scattering is a relatively complicated method experimentally, but has the significant advantages including a method that is non-perturbing and that experimental results can be inter-preted straightforwardly. Previous studies have demonstrated the usefulness of this technique for analyse electron behav-ior in relatively high density plasmas,13?16 while we latterly reported the development of an experime ntal trunk capable of reservation accurate measurem! ents in very low electron den-sity conditions, found in low pressure capacitively coupled rf plasmas.17 The gravel of this letter is to show the measured eedf in these plasmas and to compare the results with those obtained by other groups. Details of the experimental placement were shown elsewhere 17 and we describe its most salient features here. The discharge sleeping room was a cylindrically shaped stainless-steel vacuum chamber with a diam of three hundred mm. Argon plasmas were sustained amongst two parallel plate-electrodes made of stainless steel. The electrodes had a diameter of 100 mm and were disconnected by 20 mm. The speeding electrode was connected to a 13.56 megacycle power supply finished matching network, while the raze electrode was connected to the chamber mole and to the ground. The laser source was a Nd:YAG laser operated at the second harmonic wavelength of 532 nm. It had a pulse en-ergy of 400 mJ, a pulse width of 7 ns, a beam contrariety of 0.5 mr ad, and was operated at a repeat rate of 10 Hz. The laser beam was injected in a even parallel to the electrode emerge and passed through the central plane of the plasma. It was focused to the center of the chamber by a lens system with a focal length of 670 mm. A beam dump, a viewing dump, baffles, and Brewster windows were used to minimize the stray light level. The staccato light was smooth by a lens with diameter of 130 mm and a focal length of 200 mm, at a! Electronic mail: mansour@asem.kyushu-u.ac.jp APPLIED physical science earn VOLUME 78, NUMBER 21 21 whitethorn 2001 3187 0003-6951/2001/78(21)/3187/3/$18.00 © 2001 American Institute of Physics Downloaded 18 may 2001 to 129.25.14.96. Redistribution quash to AIP license or copyright, see http://ojps.aip.org/aplo/aplcr.jsp If you wish to get a full essay, order it on our website: BestEssayCheap.com

If you want to get a full es say, visit our page: cheap essay