Lutetium Bisphthalocyanine: The First Molecular Semiconductor

Abstract

Berzelius, in 1823, isolated silicon, the first inorganic semiconductor. This material showed unusual conduction properties. The electrical conduction is thermally activated with an activation energy of 1.12 eV, the density of intrinsic carriers is low, of the order of 7.1 10⁹/cm³, approximately one carrier per 10¹³ atoms. However, the corresponding mobilities are high:

$$ {\mu_e} = 1350 c{m^2}/V.s.,\quad {\mu_n} = 480 c{m^2}/V.s. $$

([1,2])

The intrinsic conductivity of silicon is therefore around 10^-6 Ω^-1 cm^-1. This latter value may be reached only for extremely pure materials because of the very low concentration of intrinsic carriers. Ti, Zr or V for example affect the electrical properties of silicon for concentrations exceeding 0.001 ppm [2]. This ensemble of electrical properties leads to the definition of a class of materials whose conduction is situated between those of insulators (inferior to 10^-7–10^-8 Ω^-1 cm^-1) and those of metals (10² Ω^-1 cm^-1 or higher). It is worth pointing out that the criterion of overall conductivity for defining an inorganic semiconductor in fact reflects a low density of charge carriers associated with a high mobility. In 1948, Bardeen, Schockley and Brattain opened the field of microelectronics by fabricating the first transistor based on another semiconductor: a single crystal of germanium. The material, the semiconductor, had found its main function, the fabrication of devices associated with electronics finalities.

Une vision moléculaire du monde ... Démocrite prétend que les atomes se repoussent ou s’attirent, Empédocle dirait plutôt qu’ils s’aiment ou qu’ils se haïssent. Le résultat serait le même mais la Chimie y gagnerait ... peut être.