Our research is focused on the effects of fluid flow, heat and mass transfer on the growth of single crystals from the melt. The crystal growth processes used in our laboratory include:

1. The Czochralski (CZ) Processes

2. The Vertical Bridgman (VB) Processes and Bridgman Processes with Baffle (BB)

The thermally-driven natural convection in the melt is unavoidable. Typically, it is characterized by complex periodic/oscillatory flows which cause uneven growth rate, radial and micro segregation, nucleation of disoriented crystals, etc. [1]. Therefore, thermally-driven flows are widely considered to be detrimental to the growth process.

There are ways however, to prevent or subdue these flows:

1. Reducing Natural Convection The techniques used diminish convection include growing crystals in space laboratories in the near-earth orbit, using static magnetic fields and baffles (link to NASA sponsored Present Projects and SUBSA and [2], [3])

2. Imposing Forced convection (FC) is preferred in various heat and mass transfer devices, because it is steady and easy to control. In melt growth, the forced convection is a practical alternative to the more difficult and less reliable options of completely eliminating natural convection in order to achieve steady state growth [3, 5-7]. Using forced convection it becomes easier to:

• keep steady the velocity, temperature, concentration fields and growth rate 

• control the solid-liquid interface shape

• establish thin and uniform boundary layers

3. Using a disk shaped baffle to reduce NC and impose FC (link to) [5,7]

• Status

The first milestone is to conduct finite element simulations, to optimize the geometry and procedures to for the ground based experiments, including:

1.  direct measurement in capillaries of diffusion coefficients of dopants in Ge and Si. The goal is to 

i optimize the diameter, length and duration of the capillaries;

ii) the benefits of using transverse magnetic fields.

2. Indirect measurements by 

i) growing doped single crystals, and 

ii) by measuring and fitting the axial distribution profiles of the dopants in the crystals. 

The crystal will be grown using the CZ process, as in the BPS experiments [] and by using the rotating baffle process [].

At present, we are conducting experiments, to optimize the geometry and procedures of the ground-based experiments.

The flight experiments in the LGF furnace at ISS are planned for 2024.