Czochralski Process / Technique

 Czochralski Process Crystal Growth method :

This Method is Adopted to Grow III - IV Compound Seniconductors.

Working :

The Material to be Grown is taken in a Crucible(non-reacting container), and Heated Under a Controlled Atmosphere Above the Melting Point. A Rod with a Chuck Which can be Pulled Contains A Seed Crystal and the Lower End is Kept Above the Crucible. The seed is Dipped into the Melt and the Temperature is Adjusted Until a Meniscus Can be Supported by the Crystal. Then the Rod is Rotated and Lifted Slowly.

Crystal of Desired Diameter is grown by Adjusting the Power Supplied to the Melt. The Crystal can be Visually Observed by Placing the Whole Setup in an Envelope With Ambient Gas Atmosphere.

The Crystal Shape is Free from defects Because of the Shape of the Crucible. The Rate of Pulling Depends on Latent Heat of Fusion of Charge, Thermal Conductivity, and Rate of Cooling of Pulling Rod.  By adjusting the Pull and Rotation Rate a Good and Uniform Crystal can be Obtained.

LEC - Liquid Encapsulated Czochralski Technique

LEC is a Technique by Which a Single Crystal of Components That Produces High Vapour Pressure at the melting point can be Grown.

Advantages :

• The Crystal Without any Stress can be Obtained by this Method, Since there is No Direct Contact Between the Crucible Walls and Crystal.
• At Any Stage of Growth Crystal can be Extracted From the Melt and Investigatiom on The Study of Growing Condition can be Done.

Disadvantages :

• It is Difficult to Maintain Thermodynamic Equlibrium Between the Vapour and the Melt.
• Engineering Problems Like Rotating and Pulling the Crystal also to be Considered.

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