Materials used in electronics

Generally in the field of electronics, there are two types of material used for manufacturing the electronic devices. They are; vacuum tubes and semiconductor.

i) Vacuum tubes

During twentieth century the electronic devices were formed using tubes. The material used for manufacturing the tube was glass. The vacuum was created inside the glass and hence that device was generally called vacuum tubes in which the electrons flow through vacuum. These tubes have been finding wide applications in radio, telephones, sound motion pictures, televisions and industrials automation. A vacuum tube usually consists of a cathode for emitting electrons; an anode, for collecting electrons and one or more electrodes called grid for controlling flow of electrons cathode and anode.

According to the number of electrodes vacuum tubes are classified as;
    a. Vacuum diode
    b. Vacuum triode
    c. Vacuum tetrode
    d. Vacuum pentode

ii) Semiconductor material

A semiconductor is a material with electrical conductivity due to electron flow (as opposed to ionic conductivity) intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter. Semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, and many other devices. Such devices include transistors, solar cells, many kinds of diodes including the light-emitting diode, the silicon controlled rectifier, and digital and analog integrated circuits. In a metallic conductor, current is carried by the flow of electrons. In semiconductors, current is often schematized as being carried either by the flow of electrons or by the flow of positively charged "holes" in the electron structure of the material. Actually, however, in both cases only electron movements are involved.

Common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of proportions. Such compounds share with better known semiconductors intermediate conductivity and a rapid variation of conductivity with temperature, as well as occasional negative resistance. Such disordered materials lack the rigid crystalline structure of conventional semiconductors such as silicon and are generally used in thin film structures, which are less demanding for as concerns the electronic quality of the material and thus are relatively insensitive to impurities and radiation damage. Organic semiconductors, that is, organic materials with properties resembling conventional semiconductors, are also known.

References
Mehta V. K., Principles of Electronics, First Edition, S. Chand & Company LTD., [2002]
Sedra and Smith, Microelectronic Circuits, Fourth Edition, Oxford University Press Inc, UK, [1998]
IEEE Dictionary of Electrical and Electronics Terms ISBN 978-0-471-42806-0