A thermodynamical model of molecular beam epitaxy, application to the growth of II VI semiconductors
We present a model of molecular beam epitaxy based on thermodynamics. The equilibrium between a compound or a ternary alloy with the gas phase is illustrated in the case of HgTe and CdHgTe. The meaning of equilibrium pressure is analysed and we make the assumption that the fluxes leaving the actual growing compound are linked by the mass action law where the pressures are transformed into the equivalent fluxes. A detailed balance of the species leaving or arriving at the surface is then possible and leads to a set of equations which can be solved to predict the growth rate, the x value of a ternary alloy, the excess of one of the species, the incorporation coefficient. Examples of calculation are shown for CdTe and Cd x Hg 1−x Te and are compared with experimental results and show a good agreement. The main interest of this model resides in its ability to predict the effects of the modification of one of the growth parameter. Nevertheless it predicts only the limit conditions which are not necessary reach due to the kinetic of the reactions Presentation d'un modele thermodynamique de l'epitaxie par jets moleculaires. Illustration par les cas de HgTe et CdHgTe. La comparaison avec les resultats experimentaux montre la validite des previsions du modele, dont l'interet principal est de permettre d'evaluer l'influence de la modification d'un parametre de croissance. La validite de ce modele est cependant limitee si la cinetique des reactions ne permet pas d'atteindre l'equilibre; ce n'est pas le cas pour les alliages II-VI etudies ici
Arsenic incorporation during MBE growth of HgCdTe
We discuss the equilibrium model of the amphoteric behavior of arsenic in HgCdTe and its applicability to material grown by molecular beam epitaxy. Suggestions are made on how to achieve active incorporation by manipulating the surface orientation, or by using precursors that provide steric hindrance.
CNC Desktop Vertical Machining Bench Design and Cooling Fluid Application
Today's manufacturing technologies, the human work force is used and at least a minimum level of margin of error is used in CNC machines. Desktop CNC machine tools and CNC machine tools are developed in parallel with the development of personal computers. This study provides CNC training institutions for education, small and medium-sized enterprises for commercial purposes use the low-cost desktop machine has been designing and manufacturing of CNC vertical machining was carried out. Desktop CNC machine tools and production capacity to handle the kind of material was applied to increase the cooling fluid. Through A199 and Fe37 the cooling fluid application desktop CNC machine tools, such as processing of materials that are difficult to successfully processed. Keywords—CNC, Desktop CNC Machine, CNC Design