The characteristics of pulse-modulated inductively coupled plasmas in argon and chlorine have been experimentally investigated. Measurements were performed for peak rf powers between 150 and 400 W at 13.56 MHz, duty cycles between 10 and 70%, and pulse repetition frequencies between 3 and 20 kHz. Over this parameter space, measurements were performed of the time dependent forward and reflected rf powers into the matching network, coil voltage, rf variation of the plasma potential, electron density, and Cl− density. These measurements indicated that for the first 5–30 rf cycles of each pulse, the discharges probably were operating in a capacitively coupled discharge mode with rf variations in the plasma potential of several hundreds of volts and relatively low electron density. Measurements of the electron density in pulse-modulated chlorine discharges indicated that the plateau electron density was a function of the duty cycle; the plateau electron density was lower for higher duty cycles. This may indicate that the ratio of Cl to Cl2was changing with duty cycle. In addition, a microwave radiometer was used to provide an indication of the time-dependent electron temperature. Large spikes in the microwave radiation temperature were noted at the turn-on of the rf power pulses and, in some cases, at the transition from a capacitively coupled to an inductively coupled plasma.
The use of ferroelectric (Pb,La)(Zr,Ti)O3 as a cathode material is investigated. It has been suggested in the literature that by rapidly changing or reversing the spontaneous polarization in the ferroelectric, a large charge imbalance can be produced at the surface of the material. The field from this charge imbalance extracts bound carriers from the cathode. An approach to achieving this polarization change by using a negative bias field to preset the material prior to switching is discussed in this letter. This bias field can also be used to control the bound surface charge on the material. Emission currents on the order of 100 mA are observed and the emitted charge is on the order of 30 nC. Measurable emission occurs only when the material is driven into saturation.
Rarely is electrical technology at the focus of the classic case studies used in engineering ethics courses and textbooks. This makes it sometimes difficult to excite and to motivate electrical and computer engineering students to study and discuss these cases. In teaching engineering ethics to these students, it can be valuable to employ case studies that involve technical issues that electrical and computer engineers have already studied in other courses. In this paper, four engineering ethics case studies covering topics that have been shown to interest electrical and computer engineering students are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.