Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Deposition of Homogeneous Films from Alloy Sources

IP.com Disclosure Number: IPCOM000082392D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Taylor, RC: AUTHOR

Abstract

When an alloy of two metals is evaporated, the composition of the deposited film is usually very different from that of the source, due to preferential evaporation of one of the alloy components. Therefore, the composition of the source and of the film change with time, and the resulting film is nonhomogeneous in depth. The film composition and degree of inhomogeneity is dependent not only on source composition but also on source temperature, since the vapor pressures of the alloy components change relative to each other with temperature. For component A, the rate of evaporation is given by the following equation: dn(A) over dt = 0.0583 over square root of M(A)T f(A)X(A)P(A) where M is the atomic weight, f the activity coefficient, X the atom fraction, and P the pressure of pure A at temperature T.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Deposition of Homogeneous Films from Alloy Sources

When an alloy of two metals is evaporated, the composition of the deposited film is usually very different from that of the source, due to preferential evaporation of one of the alloy components. Therefore, the composition of the source and of the film change with time, and the resulting film is nonhomogeneous in depth. The film composition and degree of inhomogeneity is dependent not only on source composition but also on source temperature, since the vapor pressures of the alloy components change relative to each other with temperature. For component A, the rate of evaporation is given by the following equation: dn(A) over dt = 0.0583 over square root of M(A)T f(A)X(A)P(A) where M is the atomic weight, f the activity coefficient, X the atom fraction, and P the pressure of pure A at temperature T.

The same equation is used for component B with the appropriate substitutions.

For the alloy illustrated by the figure, Cd(40)Co(60), assuming f = 1, the equations at each of the noted temperatures are: at 2100 degrees K dn(Co) over dt = 5.97x10/-5/X(Co), dn(Gd) over dt dt = 1.52x10/-5/Gd) at 2000 degrees K, dn(Co) over dt = 1.70x10/-5/X(Co), dn(Gd) over dt = 5.2x10/-6/X(Gd) at 1800 degrees K, dn(Co) over dt = 1.34x10/-6/X(Co), dn(Gd) over dt = 4.71x10/- 7/X(Gd).

The only condition under which congruent evaporation takes place that is the vapor composition is the same as the source composition, is when fA over fB PA over PB (MB over MB)/1/2/ = 1. Assuming fA/fB = 1, congruent evaporation for Gd-Co alloys will occur with a source temperature of 1230 degrees K, Which will give a film deposition rate of 1A/10/6/ sec.

It is apparent from the calculated curves in the fi...