Electronic Materials and Devices
Electronic materials are the type of materials which are typically used as core elements in a variety of device applications. These elements can be, for example, memories, displays, LEDs and could be easily seen in daily electronic gadgets such as mobile phones, computers, laptops, tablets, GPS devices, LED bulbs, TVs and monitors. Changing dimensions and level of functionality requires continuous efforts to develop state of the art materials to meet the technological challenges associated with development of these devices. For example, transition from CRT based displays to LCD and then LED based displays could not have been possible without development of materials such as liquid crystals, organic semiconductors and electroluminescent materials. Similarly, high density storage capacity would not have been possible without development of materials with high permittivity and permeability in dielectrics and magnetic materials. Same can be said about the processor’s with every increasing data processing speed as the technology has progressed from 486 based platforms to quad core or octa core processors. All of the above has been possible because of continuous efforts to improve fundamental understanding about the electronic properties of various materials and at various length scales as well as forms. This is complemented by concurrent advances in the processing and fabrication technologies, in particular related to thin film and nanostructure processing. Electronic properties of a material are governed by the response of electrons and other charged entities to external stimulus such as electrical potential difference and its variation, incident electromagnetic radiation, magnetic field, heat, mechanical forces etc. The response to external stimulus is strongly correlated with the internal structure of material at different length-scales, chemical composition, both intrinsic and extrinsic defects, as well as dimensionality (zero, one, two or three dimensional) of the material. The field of Science and Technology of Electronic Materials involve understanding these correlations, as well as development of technologies for the synthesis/fabrication of materials with desired electronic properties.
Beginners can look at the following examples to appreciate the science of electronic materials: Example 1: Effect of differences in the arrangement of atoms (called crystal structure) for a particular element, in this case Carbon in diamond and graphite forms. Example 2: Effect of impurities on the electronic properties of a material
Semiconductor is a class of materials where one can change their electrical conductivity by orders of magnitude through introduction of controlled amounts of impurities. For example, when boron or phosphorous atoms, called as dopants, are introduced in silicon, its electrical conductivity (inverse of resistivity) and its type (whether due to hole or electron i.e. p-type or n-type) can change as shown in the plot, taken at room temperature. Note that at one end of impurity concentration, silicon behaves like an insulator, and at other end, it is a good conductor, spanning over eight orders of magnitude change in the electrical conductivity. Example 3: Interfacing of two or more different materials with different electronic properties for desired device application.
When two blocks of silicon having opposite type of conductivity, p-type and n-type, are placed together, the simplest device called as Diode is formed. One can think of these diode as ON-OFF switches. Such a diode is a basic building-block in many devices, for example, solar-cells, light emitting diodes, solid-state Lasers etc.