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Coherers, a Review COHERERS, A REVIEW A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN ENGINEERING at Temple University by Thomas Mark Cuff August 1993 Dr. Brian P. Butz Dr. Thomas E. Sullivan, Chairman, Electrical Electrical Engineering, Engineering Thesis Advisor Dr. Richard D. Klafter Dr. Vallorie Peridier, Director, Graduate Studies, Mechanical Engineering, Electrical Engineering Thesis Committee Member Dr. Thomas J. Ward Dr. Richard D. Klafter, Associate Dean of Electrical Engineering, Engineering Thesis Committee Member Dr. Charles K. Alexander Acting Dean of Engineering ii © by Thomas Mark Cuff 1993 All Rights Reserved iii ABSTRACT The first known radio frequency detector was the coherer, and even though this device has been around for over a century there is still no generally accepted explanation of how it works. A historical review of the different realizations of the coherer together with any investigations that might help illuminate its inner workings was under taken. As a result of the historical review, it became clear that the coherer evolved directly into the MOM (Metal-Oxide- Metal) ‘diode’ and, by only a slightly more circuitous route, it appeared as the forerunner to the STM (Scanning Tunneling Microscope). The MOM ‘diode’, besides being a progeny of the coherer, has something else in common with the coherer, no generally accepted explanation of how it works. Examining the history of the STM, from its nascent form (circa 1901) to its present day configuration, revealed along the way an explanation for bridge formation, i.e. cohering of coherers. In addition, in the course of reviewing some of the work done in the mid 1920s on coherer behavior, information surfaced that helps shed some light on the so-called positive and negative coherer behavior. iv Lastly, the approach taken in this thesis, wherein the coherer was related to the MOM ‘diode’ and the STM, was found to have been completely anticipated by three papers (circa 1918-1924) written by Angelika Maria Josefa Székely de Doba. v ACKNOWLEDGEMENTS No effort is ever truly an individual one. Even Sir Isaac Newton admitted as to how he had stood “…upon the shoulders of Giants.” If I have managed to accomplish anything intellectually worthwhile in this thesis, it was only because of my clambering onto various shoulders. I should now like to thank those who helped me. First, my mother and father, Camille and Howard Cuff, for their encouragement, support and for their providing a quiet place for me to study and write. Second, my advisor, Dr. Thomas E. Sullivan, who allowed me to choose ‘coherers’ as my thesis topic and who then suggested that there might be useful and revealing links between coherers and MOM (Metal-Oxide-Metal) ‘diodes’ and STMs (Scanning Tunneling Microscopes) - there indeed were. I also wish to thank him for the innumerable hours he spent listening to my verbal discourses on the subject of this thesis, and for providing me with much needed pep talks when I became discouraged. Third, I wish to thank the other members of my thesis committee, Dr. Vallorie Peridier and Dr. Richard D. Klafter, for having read the various drafts of my thesis - a not inconsiderable task considering its size - and vi for their comments and especially their criticisms; their criticisms improved the readability, organization and grammar of my thesis, but all the remaining deficiencies in these three areas clearly are my own doing. A penultimate thanks must also go out to the W. W. Smith Charitable Foundation for their funding of my Future Faculty Fellowship. And lastly, I must express my appreciation to Dr. Vivian J. Phillips, whose book, Early Radio Wave Detectors, provided me with the inspiration to choose the subject of coherers for my thesis - thanks for the memories. vii TABLE OF CONTENTS Abstract .................................................................................................. p. iii Acknowledgements .......................................................................... p. v Chapter 1 - Introduction .............................................................. p. 1 Chapter 2 - History ............................................................................. p. 5 Chapter 3 - Amorphous Materials ............................................... p. 26 Chapter 4 - What Is Known (pre-1970) .................................... p. 43 Chapter 5 - Resurrections .............................................................. p. 119 Chapter 6 - What Is Known .................................................... p. 144 Chapter 7 - Conclusions .................................................................. p. 158 Bibliography ......................................................................................... p. 164 Appendix A - MOM Devices .............................................................. p. 187 Appendix B - Passivation Layers of Noble Metals ................ p. 211 Appendix C - Literature Search Strategy .............................. p. 244 Appendix D - Beilby Layer ........................................................... p. 258 Appendix E - The STM (Scanning Tunneling Microscope) .... p. 278 Appendix F - ‘Vacuum Arc, Spark of Discharge’ Phenomena .. p. 349 Appendix G - The Copper Oxide Rectifier .............................. p. 365 viii LIST OF FIGURES Figure 1 - Marconi Type Radio Receiver (circa 1900) ............ p. 8 Figure 2 - Edison’s Chalk Receiver (Two Views) ..................... p. 32 Figure 3 - Equivalent Circuit of a Filings Coherer ................. p. 49 Figure 4 - a) Righi Oscillator, b) Bose Oscillator .................. p. 52 Figure 5 - Rossi & Todesco’s Apparatus ..................................... p. 79 Figure 6 - Eccles’ Sensitivity Curve, Fe-oxide-Hg ............... p. 95 Figure 7 - Eccles’ Sensitivity Curve, Fe-oxide-Fe ............... p. 96 Figure 8 - Faris’ Sensitivity Curve, Pt-oxide-W .................... p. 97 Figure 9 - Meyerhof’s Sensitivity Curve .................................... p. 99 Figure 10 - Faris’ Sensitivity Curve, Pt-oxide-W .................. p. 102 Figure 11 - a) First Transistor, b) Coaxial Transistor ........ p. 124 Figure 12 - H. Müller’s Circuit For Investigating Contact Behavior ................ ........................................................................................................ p. 150 Figure 13 - Coherer Applications, A Chronology ..................... p. 157 Figure B1 - The Electrolytic Detector and Circuitry ............. p. 219 Figure B2 - Austin’s Sensitivity Curve, Pt-solu.-Pt .............. p. 228 Figure B3 - Székely’s Sensitivity Curve, Pt-solu.-Pt ............. p. 228 Figure B4 - Székely’s Sensitivity Curve, Pt-solu.-Zn/Hg ..... p. 230 Figure B5 - Székely’s Sensitivity Curve, PbS-C ....................... p. 231 Figure B6 - Schuster’s Apparatus ................................................. p. 232 Figure B7 - Modified Schäfer Anticoherer ................................ p. 312 Figure E1 - Paschen Plot ................................................................... p. 283 Figure E2 - Critical Pressure Plots ............................................. p. 285 Figure E3 - An Earhart Plot ............................................................. p. 290 Figure E4 - Hoffmann’s Magnetic Apparatus ........................... p. 312 Figure G1 - Manufacturing A Copper Oxide Rectifier ................. p. 378 1 CHAPTER 1 - INTRODUCTION “The most beautiful thing in the world is, of course, the world itself.” - Wallace Stevens “The universe is not only queerer than we imagine, but it is queerer than we can imagine.” - J. B. S. Haldane “God is in the details.” -Ludwig Mies van der Rohe Electrical engineers, physicists and material scientists have spent a considerable amount of time studying and characterizing the bulk properties of certain industrially important materials. The fact that materials are so important not just for technology but human affairs in general is perhaps best acknowledged by the temporal classifications of Stone Age, Bronze Age, Iron Age and currently the Silicon Age. In tandem with the search for new materials or, what sometimes amounts to the same thing, better purification of preexisting materials, there is also the inexorable trend towards miniaturization. Because the surface-to-volume ratio goes as 1/L, where L is the characteristic length of a body, as electronic or for that matter mechanical devices become smaller, this ratio gets larger and larger. As the surface-to-volume ratio increases, the surface begins to exercise a more dominant rôle on the electrical and mechanical behavior of the device. An example of these so-called size effects is the increase in electrical and thermal resistance of very thin wires. 1 1 Kasturi L. Chopra; Thin Film Phenomena; McGraw-Hill; 1968; see the chapter entitled, Electron-Transport Phenomena in Metal Films. 2 It should be noted that while miniaturization implies that surface effects will be important, the converse is not true, i.e., significant surface effects do occur in macroscopic devices. Many times all it takes is for the macroscopic device to rely on current flow though an interface. Many macroscopic electrical devices are composed of mechanical junctions, e.g., mechanical switches, and in these devices, the surface takes on the rôle of an interface through which the electrons must pass, and so the condition of the surface is critical to the functioning of the device. This is especially true when the impressed voltage is small. In fact, coherer
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