Loucas G. Christophorou

Electron Interactions with CHF3

In this paper we assess and synthesize the available information on the cross sections and the rate coefficients for collisional interactions of trifluoromethane (CHF3) with electrons in an effort to build a database on electronic and ionic collision processes that will aid the understanding of the behavior of CHF3 in its use in manufacturing semiconductor devices and other applications. The limited data on the total and partial electron impact ionization cross sections, total and partial cross sections for electron impact dissociation of CHF3 into neutral species, electron-impact induced line and continuous light emission from CHF3, negative ion states of CHF3, and the energetics of ionization, dissociation, and attachment are summarized and discussed. Besides some recent unpublished measurements of the total electron scattering cross section below 20 eV, to our knowledge no measurements are available of the cross sections of any of the electron scattering processes (elastic, momentum, vibrational, inela...

Values of Society and Science

We hold the view that in a world dominated by facts there is a place for values. A place for a system of common, shared values based on the demonstrated likeness among the values of the peoples of the world, and on the realization, that even in today’s world of extreme diversity and individuality, the seemingly conflicting values of national and local cultures are but complementary. We are also convinced that by fostering a dialogue among civilizations, among national and local cultures, among the humanities, the religions and the sciences, and by looking at values from different perspectives, we will be able to better understand, identify, and safeguard humanity’s common heritage of values and make it valuable.

Boundaries of Science

The power of modern science to answer questions which can be defined scientifically is almost without limits (Chap. 3). Limitless also seems to be the spectrum of scientific questions to which scientific answers are sought; it stretches from the normally simple questions aimed at verification and systematization of scientific knowledge, to fundamental new questions of the scientific frontier where normally the answers are difficult and the scientific method is often at the limits of its capability. Scientific answers are also searched for fundamental questions that are generally assumed to have already been answered, as for instance, “Is the speed of light in vacuum the maximum possible speed, the unsurpassable constant of nature?” Questions and searches which largely demonstrate the way science works and evolves; the validity of scientific knowledge and the validation process by which it is established.

Scientific and Technological Frontiers

No one really knows what science is doing today. What we do know is that increasingly scientific questions are becoming more difficult, in need of new scientific instruments, methods and facilities; better information technology and advanced computation; new concepts and constructs and new mathematics to enable better understanding of higher levels of abstraction in basic science, and of complex systems, foremost biological; new initiatives to expand the scientific frontier further into space and time at both ends of the time and space scales. How then can anyone predict what would be frontier science and scientific technology in the future, say, by the end of this century and even beyond? Despite the difficulty, attempts have been made.,,,,,,

Arrows of Time

Much has been said, conjectured, speculated and dreamed about the origin and evolution of the universe, by scientists and non-scientists alike. Any system of thought claiming to provide an understanding of the physical world, made some statement about the origin and evolution of the universe.

Distinct Characteristics of Modern Civilization

Modern civilization’s most distinct characteristics are due to science and science-based technology. In this Chapter, we exemplify these characteristics focusing on the prevalent impact of science and science-based technology on man, society, the environment and climate change, and on the fundamental role of energy in both science and society.

The Future: QUO VADIS HOMO SAPIENS?

Change is what we cannot stop, and science is the prime facilitator of change. Man’s unique ability to cope with and adapt to change may be enhanced or diminished by whatever we will do to ourselves in the future. Let us, then, look at some of the changes we discussed in this book and ponder over their expected challenges.

Scientists and society: needs and responsibilities

The recent advancement of science has been spectacular and the scientific frontier potentially endless. Similarly profound has been the impact of modern science on society and on man himself. And yet, the universal acceptance of science by society is still limited and in need of a more effective transmission of the intellectual and cultural value of science, and a meaningful discussion of the fears and suspicions of science by society. In this paper, I first comment on scientists in modern society and then focus on some areas of stress between scientists and society where lay mutual responsibilities and needs. I conclude by emphasizing the need for mutual accommodation, common action, and continuous dialogue.

Assessed Total and Partial Ionization Cross Sections for CF4, C2F6, C3F8, CHF3, CF3I, c-C4F8, Cl2, CCl2F2, BCl3, SF6, and Fragments of CF4 and SF6

We have recently completed an updated review, synthesis, assessment, and discussion of low-energy electron interactions with the plasma processing gases CF4, C2F6, C3F8, CHF3, CF3I, c-C4F8, Cl2, CCl2F2, BCl3, SF6. This work, along with fundamental knowledge on electron-molecule collision processes, the definition of the various electron collision cross sections and rate coefficients, and the experimental and theoretical methods used for their determination have been described in Christophorou and Olthoff.1 It has been shown in this reference, that reliable data on the electron transport, electron attachment, and electron-impact ionization coefficients generally exist for most of these molecules, except for electron transport in strongly electronegative gases. Also, reliable data exist on the collision cross sections for most of these molecules, but this knowledge depends on the collision process and the molecule under consideration. The cross sections and coefficients that have been recommended or suggested1 were based on experimental measurements. This work1 has shown that while a great deal of quantitative data have become available, especially recently, for the molecules under consideration, there is still a pressing need for quantitative measurements of the cross sections for electron-impact dissociation into neutral fragments, direct and indirect vibrational (and electronic) excitation, and electron interaction processes involving excited and transient (radical) species.