This book presents a new approach to quantum mechanical tunnelling and its applications to various fields of physics. The conventional concepts of this phenomenon, which are based on a time-dependent or time-independent approach, are inadequate in providing explanations for 1) the limit of resolution of field-emission microscope, 2) the Esaki-Integral representation the tunnelling I-V characteristics of tunnel diodes, 3) the Josephson effect, 4) the tunnelling time, etc. The new theory presented here not only provides adequate explanation for all the above-mentioned effects but also gives an accurate expression for tunnelling current density which predicts results closer to the experimentally observed values. The new presentation also provides a more comprehensive description of the results obtained using older treatment.Contents:Quantum Mechanical Tunnelling:Conventional Formulations of the Tunnelling ProblemInadequacies of Conventional Tunnelling FormulationsA Recent Application of TunnellingThe New Tunnelling Theory:The Barrier Hamiltonian and the Wave FunctionThe Tunnelling Probability and Tunnelling TimeThe Tunnelling Current DensityThe Theory of Indirect TunnellingTunnelling in Rectangular Barrier Systems:Metal-Insulator-Metal (MIM) JunctionMetal-Insulator-Semiconductor (MIS) JunctionMetal-Insulator-Semiconductor Switch (MISS)Normal Metal-Insulator-Superconductor (NIS) JunctionSuperconductor-Insulator-Superconductor (S1-I-S2) JunctionJosephson EffectThe Semiconductor HeterostructuresTunnelling in Triangular Barrier Systems:Metal-Vacuum BoundaryMetal-Semiconductor Contact (Schottky Barrier)Semiconductor pn JunctionsSemiconductor HeterojunctionsSuper Schottky JunctionReadership: Solid state physicists and device engineers.Key Features: The book clarifies the relation between energy and mass The book stresses the key role of spin in physics The book introduces the concept of elementary quantum state whose properties are completely fixed by a few quantum numbers. It explains the probabilistic side of Quantum Mechanics by using the language of Feynman diagrams It is extremely important to distinguish between facts firmly established in certain fields of physics and hypothetical extrapolations to fields that await exploration