Method of crystallizing amorphous material with a moving energy beam

DETAILED DESCRIPTION We claim: 1.
A method of converting solid amorphous material to a more crystalline state comprising the steps of: (a) heating a portion of said material with energy from an energy beam to bring such portion to its crystallization temperature while maintaining the temperature below the melting temperature of the crystalline state of the material; and (b) moving said energy beam in relation to said material at a velocity V, which is less than or equal to V.
sub.
ac but fast enough to provide continuous controlled motion of the crystallization front; wherein V.
sub.
ac is the normalized boundary velocity of the transformation of the amorphous material to crystalline.
2.
The method of claim 1 wherein said material comprises a semiconductor film.
3.
The method of claim 2 wherein said energy beam is a laser beam, electron beam, ion beam, train of electrical pulses, or a combination thereof.
4.
The method of claim 3 wherein said beam is shaped to a focused image having a large aspect ratio.
5.
The method of claim 2 wherein said energy beam comprises a focused, shaped laser beam.
6.
The method of claim 5 wherein said laser beam has an aspect ratio of greater than about 10.
7.
The method of claim 6 wherein said semiconductor film comprises a germanium film and the laser beam employed originates from a continuous wave Nd:YAG laser.
8.
The method of claim 5 wherein said laser beam is modulated spatially and temporally.
9.
The method of claim 8 wherein said laser beam is focused to a slit image.
10.
The method of claim 2 wherein said film is preheated with a source of heat other than said laser beam.
11.
The method of claim 10 wherein said semiconductor film is supported on a substrate.
12.
In the method of crystallizing an amorphous material by scanning it with an energy beam: providing continuous controlled motion of the crystallization front by (a) maintaining the background temperature of the amorphous material at a value which is between the temperature at which periodic structure occurs and the temperature which produces runaway crystallization and (b) modulating the beam and scanning a surface of the material with the beam at a rate less than or equal to the normalized boundary velocity of the crystallization front