Page 16 - Electrical Properties of Materials

Introduction

Till now man has been up against Nature;
from now on he will be up against his own nature.
Dennis Gabor Inventing the future
It is a good thing for an uneducated man to read books of quotations.
W.S. Churchill Roving commission in my early life (1930)

Engineering used to be a down-to-earth profession. The Roman engineers, who
provided civilized Europe with bridges and roads, did a job comprehensible to
all. And this is still true in most branches of engineering today. Bridge-building
has become a sophisticated science, the mathematics of optimum structures
is formidable; nevertheless, the basic relationships are not far removed from
common sense. A heavier load is more likely to cause a bridge to collapse, and
the use of steel instead of wood will improve the load-carrying capacity.
Solid state electronic devices are in a different category. In order to under-
stand their behaviour, you need to delve into quantum mechanics. Is quantum
mechanics far removed from common sense? Yes, for the time being, it is. We
live in a classical world. The phenomena we meet every day are classical phe-
nomena. The fine details represented by quantum mechanics are averaged out;
we have no first-hand experience of the laws of quantum mechanics; we can
only infer the existence of certain relationships from the final outcome. Will it
always be this way? Not necessarily. There are quantum phenomena known to
exist on a macroscopic scale as, for example, superconductivity, and it is quite
likely that certain biological processes will be found to represent macroscopic
quantum phenomena. So, a ten-year-old might be able to give a summary of
the laws of quantum mechanics—half a century hence. For the time being there
is no easy way to quantum mechanics; no short cuts and no broad highways.
We just have to struggle through. I believe it will be worth the effort. It will
be your first opportunity to glance behind the scenes, to pierce the surface and
find the grandiose logic of a hidden world.
Should engineers be interested at all in hidden mysteries? Isn’t that the duty
and privilege of the physicists? I do not think so. If you want to invent new
electronic devices, you must be able to understand the operation of the exist-
ing ones. And perhaps you need to more than merely understand the physical
mechanism. You need to grow familiar with the world of atoms and electrons,
to feel at home among them, to appreciate their habits and characters.
We shall not be able to go very deeply into the subject. Time is short, and
few of you will have the mathematical apparatus for the frontal assault. So
we shall approach the subject in carefully planned steps. First, we shall try
to deduce as much information as possible on the basis of the classical pic-
ture. Then, we shall talk about a number of phenomena that are clearly in
contrast with classical ideas and introduce quantum mechanics, starting with
Schrödinger’s equation. You will become acquainted with the properties of in-
dividual atoms and what happens when they conglomerate and take the form of