Method for minimizing convection during crystal growth from solution

Disclosed is a method and apparatus for growing in a gravitational field a microscopic crystal from a solution. Solution is held in a vertical chamber which is relatively thin, the thin dimension being generally perpendicular to the vertical. There is a substrate crystal disposed at either the upper or lower end of the chamber and the crystal grows from this substrate crystal in one direction. In accordance with this invention, the temperature conditions of the solution are controlled so that as the crystal forms the effects of buoyant convection within the solution are minimized. This is accomplished in two different ways depending upon whether the crystal is grown from the upper or lower end of the chamber. When grown from the upper end of the chamber, the temperature of the solution is controlled so that it remains essentially isothermal so that there is essentially no heat loss from the solution. When the crystal is grown from the lower end of the chamber, the temperatures of the solution is controlled so that there is a differential in temperature throughout the solution which provides a positive thermal gradient within the chamber.