Grains are small groups of atoms built around nucleation sites, and are found mainly in metals. The perimeter of the grain is the grain boundary. Controlling grain size and boundary forces, you can alter the yield strength of a material. The smaller the grain size, the higher the force needed for dislocations, or shifting of the grains. This is controlled by many methods including cooling rate, temperature, heat-treatment, annealing, cold working, quenching and work hardening.
To make mono-silicon, you must go through a process. It involves heating and cooling and nucleation sites to control the growth of the silicon crystal structure. Three techniques are mentioned below:
"For monocrystalline processing, the most common method for manufacture involves the Czochralski process but other techniques include the Float-zone technique and the Bridgeman technique. The three techniques are used for crystal growth, but the Czochralski process is the most common as this process allows for large ingots of a semiconducting material (like silicon) to be produced at acceptable purity levels. The Float-zone and Bridgeman techniques offer very high purity levels but for most applications, such high purity levels are not required."
Source: http://www.energytrend.com/Monolike_Silicon_Processing
More information about mono-silicon manufacturing can be found here:
http://solarpvinvestor.com/news/spvi-news/90-polysilicon-production-process-and-quasi-mono-technology
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