Preface
Work function is one of the important physical quantities of materials that is related to
various phenomena. However, systematic discussion on the work function is limited
possibly because of the following two reasons. One is that the work function is
not a quantity that is specific to a bulk material such as dielectric constant, elastic
modulus, density, and magnetic susceptibility. Even one single crystalline material
has different work function values, depending on the crystal plane. This means that
work function values are influenced not only by bulk materials but also by surface
conditions. The other is that the measurement of work function values of an intended
surface of materials is not easy. The difficulty comes from the fact that work function
values are surface sensitive as mentioned above. Surface is very reactive in general,
and it is rather difficult to prepare and maintain a surface as intended states.
Basic experimental researches on the work function had progressed upon the
development of commercially available vacuum instruments in the 1960s–1970s,
which provided tools to maintain surface conditions and observe surface compositions and structures. Most of fundamental issues were established during this time.
Then, theoretical calculations of the work function have complimented experimental
researches thanks to the development of first-principles calculations in the 1990s.
Emergence of electronic devices had required the control of band alignment via
work function control at the interface, and the origins of the deviation from ideal
Schottky relation were rigorously discussed in the 1980s and later.
v
Work function is one of the important physical quantities of materials that is related to
various phenomena. However, systematic discussion on the work function is limited
possibly because of the following two reasons. One is that the work function is
not a quantity that is specific to a bulk material such as dielectric constant, elastic
modulus, density, and magnetic susceptibility. Even one single crystalline material
has different work function values, depending on the crystal plane. This means that
work function values are influenced not only by bulk materials but also by surface
conditions. The other is that the measurement of work function values of an intended
surface of materials is not easy. The difficulty comes from the fact that work function
values are surface sensitive as mentioned above. Surface is very reactive in general,
and it is rather difficult to prepare and maintain a surface as intended states.
Basic experimental researches on the work function had progressed upon the
development of commercially available vacuum instruments in the 1960s–1970s,
which provided tools to maintain surface conditions and observe surface compositions and structures. Most of fundamental issues were established during this time.
Then, theoretical calculations of the work function have complimented experimental
researches thanks to the development of first-principles calculations in the 1990s.
Emergence of electronic devices had required the control of band alignment via
work function control at the interface, and the origins of the deviation from ideal
Schottky relation were rigorously discussed in the 1980s and later.
v