Modeling and laboratory scale proof of concept of the horizontal ribbon growth process: Application to silicon wafer manufacturing
In this work we focus on the development of the Horizontal Ribbon Growth technique to produce highly pure silicon wafers for use in solar cells. We divide this preliminary work in two parts: a small scale experiment and the development of mathematical models to describe the crystallization phenomena. We begin by constructing a laboratory scale experiment to demonstrate the HRG concept using water as the working fluid. We made use of the fact that ice floats on water just like silicon would float on top of its melt. Therefore it is possible to conveniently test and analyze the operability of this technique. We find that the initial seeding process needs to be carefully controlled in order to extract a uniform wafer. Appropriate surface cooling and wall heating are necessary to guarantee the continuous formation of an ice film. We then develop simple mathematical models to predict the crystallization rate and thermal profiles of the system. We state that the driving force for crystallization is convective cooling and the film grows in one direction (downwards). Finally we propose how to validate the model using experimental data and how to extend the work to grow silicon ribbons.
Modeling and Analysis of Novel Horizontal Ribbon Growth of Silicon Crystal
We present a novel horizontal ribbon growth (HRG) process and a theoretical analysis of this method. Assuming that the existence of the meniscus is defined by diffuse growth, we determine analytically the thickness and height of the meniscus and an explicit expression for the performance of meniscus under different conditions. We then calculate the thermal profile in melt part, as well as the conditions under which the undercooling is sufficient around the solidification point. We find that diffuse growth is more sensitive to small initial thickness, and find the minimum length of the melt part to obtain undercooling. Finally, we calculate the change rule of solidification position by a variational approach, as well as the stability of the process under different conditions. We also give an expression to the instability of past HRG methods.
Untersuchungen an Metallkristallen. I
ZusammenfassungDurch Messung des Dehnungs- und Drillungsmoduls einer größeren Anzahl von Einkristallstäbchen aus Zn und Cd mit verschiedener kristallographischer Orientierung werden die Grundlagen gewonnen, um die fünf elastischen Konstanten, die dem hexagonalen Kristallsystem eigentümlich sind, sowie die drei elastischen Wellenflächen (longitudinale und zwei transversale Schallgeschwindigkeiten als Funktionen der räumlichen Richtung) zu berechnen. — Zink und Cadmium zeigen, wahrscheinlich infolge ihres großen Achsenverhältnisses, eine auffallend starke elastische Anisotropie, welche hinreichend erklärt, warum bei früheren Untersuchungen der elastischen Konstanten polykristalliner Proben so schwankende Zahlen gefunden worden sind.