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Confined Deposition of Chromium Oxide for High Density Magnetic Recording

IP.com Disclosure Number: IPCOM000036233D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+2]

Abstract

A technique is described whereby chemical vapor deposition (CVD) of CrO2 provides high density magnetic recording where the amount of CrO3 waste and cleanup is reduced. The process is an improvement over prior methods in that it is safer, uses less electricity and is suitable commercially.

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Confined Deposition of Chromium Oxide for High Density Magnetic Recording

A technique is described whereby chemical vapor deposition (CVD) of CrO2 provides high density magnetic recording where the amount of CrO3 waste and cleanup is reduced. The process is an improvement over prior methods in that it is safer, uses less electricity and is suitable commercially.

It is known that the favorable magnetic properties and high wear resistance of CrO2 provides an excellent media for thin film, high density magnetic recording
[*]. Thin films are generally prepared in a furnace, with CrO2 as the source, such that a flow of oxygen transports CrO3 to a substrate which is at a higher temperature than the CrO3 . The volatile CrO3 loses oxygen and becomes a stable ferromagnetic CrO2 . The large recording substrates require hot zone uniformity, thereby requiring large tube furnaces. For example, a three-inch substrate typically requires quartz furnace tubes that are four-feet long with associated long CrO3 diffusion distances. Much of this four-foot length becomes coated with CrO3, which is corrosive, toxic and a carcinogen, and requires extreme care in handling.

The concept described herein enables the CVD of CrO2 to be applied at atmospheric pressure, such that a flow of oxygen, or a tube furnace, is not required. It was found that it is not necessary to add oxygen so as to allow the CrO3->CrO2 + O conversion. It is only necessary to partly confine the CrO3 vapor from the source.

The process provides that enough oxygen will be evolved by the reduction of CrO3, in the vicinity of the reaction, so as to favor the conversion to CrO2 . The CrO2 formation does not depend on the rate of CrO3 arrival, such that each arriving CrO3 brings along enough oxygen to allow the conversion process to proceed. Since CrO3 is the only chrome oxide with a high enough vapor pressure to transport at one atmosphere, at high temperatures only CrO2 forms at the substrate regardless of the composition or the amount of the source.

The apparatus used quartz beaker 10, as shown in Fig. 1, with a flat top edge (no pour spout) and sits on hot plate 11. Recording substrate 12 (to be coated) rests on the top of beaker 10 with the nucleation side down. Substrate heater 13, consisting of a diffusi...