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Growing Low Defect Bubble Material Substrates

IP.com Disclosure Number: IPCOM000082717D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Blum, SE: AUTHOR [+2]

Abstract

Presently, single crystals of rare earth garnets that are used as substrates in bubble film technology, are prepared by the Czochralski pulling technique from iridium crucibles. Appreciable developmental work and crystal growing "artistry" are required in order to obtain the needed defect-free materials.

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Growing Low Defect Bubble Material Substrates

Presently, single crystals of rare earth garnets that are used as substrates in bubble film technology, are prepared by the Czochralski pulling technique from iridium crucibles. Appreciable developmental work and crystal growing "artistry" are required in order to obtain the needed defect-free materials.

It has been discovered that garnet crystals of good crystal quality can be better grown by a simple modification of the Czochralski method. In general, the garnet crystal is pulled from the molten garnet contained in an iridium crucible that is directly heated by RF coupling. This method is modified by containing the melt in a thin-metal liner within the iridium susceptor. By so doing, the convective action in the molten garnet melt is greatly reduced, thereby facilitating the controlled growth of the crystal. This is because the turbulence of the melt as well as the thermal convective currents are minimized. This quiescent condition is especially advantageous when the crystal is being "necked in" in order to eliminate dislocations.

As an example, neodymium gallium garnet (NdCG) is pulled from a platinum liner within an iridium susceptor. A schematic diagram of the apparatus used is shown in the figure. The actual pulling operation is performed in the usual manner. However, in this case, the garnet is grown at about twice the normal speed (10mm/hr). When NdCG is grown directly from iridium crucibles, the crystal obtai...