Crystal Growth晶体生长英文版.doc

Microelectronic Technology English Crystal Growth Written by: Z Guevara Electronic technology science Class Two Number: 2011221105200198I.About the Concept A crystal is a material whose constituent atoms, molecules,or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a major stage of a crystallization process, and consists in the addition of new atoms,ions, or polymer strings into the characteristic arrangement of a crystalline Bravais lattice. So a crystal is characterized by regular arrangement of atoms or molecules. Single Crystals ,in one type, is macroscopic samples with long-range alignment of periodic atomic structure, or Polycrystalline crystals ,often nicknamed“powder”samples many randomly oriented microscopic.The growth typically follows an initial stage of either homogeneous or heterogeneous nucleation,purposely added to start the growth. II.Process and mechanism of Crystal Growth The action of crystal growth yields a crystalline solid whose atoms or molecules are typically close packed,with fixed position in space relative to each other. Experimental and theoretical contributions are published in the following fields: theory of nucleation and growth, molecular kinetics and transport phenomena, crystallization in viscous media such as polymers and glasses;crystal growth of metals, minerals, semiconductors, superconductors, magnetics, inorganic, organic and biological substances in bulk or as thin films; molecular beam epitaxy, chemical vapor deposition. The Laser is numbered among the most miraculous gifts of nature and lends itself to a variety of applications.laser system based on optically active centers or ions in insulator host materials,as its optical spectroscopic properties are vital to its performance. Material properties are determined by the properties of the host material, the properties of the optically active ions,and the mutual interaction between the host and the dopant ions.The most fundamental requirement for a laser material is that it can be easily and economically produced with high quality in large amounts and different sizes. Stability with respect to local environmental changes such as temperature,humidity,stress,thermal effects, and thermal lensing.It is possible to put 2 types of ions in the same host material Non-radiative energy transfer from the sensitizers to the activators. In principle,silicon crystals can be grown in much the same manager as sugar crystals.In practice,no suitable solvent exist for silicon,and the crystals must be the grown from the molten element at temperatures in excess of 1400.The basic process flow is from starting materials to polished wafers.The starting materials silicon dioxide for a silicon wafer) are chemically processed to form a high-purity polycrystalline semiconductor from which single crystals are grown.The single-crystal ingots are shaped to define the diameter of material and sawed into wafers. These wafers are etched and polished to provide smooth, specular surfaces on which devices will be made.A technology closely related to crystal growth involves the growth of single-crystal semiconductor layers upon a single-crystal semiconductor substrate,which is called epitaxy, from the Greek words epi (meaning “on”) and taxis (meaning “arrangement”). There are basically two techniques for crystal growth from the melt (i.e., material in liquid form): the Czochralski techniques and the Bridgman technique.A substantial percentage (-90%) of the silicon crystals for the semiconductor industry are prepared by the Czochralski technique; virtually all the silicon used for fabrication integrated circuits is prepared by this technique. III.The Development Tendency The field of crystal growth can be divided into fundamentals and growth techniques. Fundamentals address the underlying scientific principles relevant to all the techniques of crystal growth and to all materials. For many decades, artificial crystals, especially semiconductor crystals have been the core in applications such as electronics and optoelectronics. New artificial crystals with unprecedented physical and chemical properties will continuously allow us to envision a new paradigm in a wide range of technological fields, therefore developing capability of growing new crystals that have desirable physical and chemical properties is the key to further advancement,and thats for what t