1. A method of implanting a workpiece comprising:
implanting a workpiece such that said workpiece has a dose at a center different from a dose at a periphery; and
growing a compound semiconductor on said workpiece after said implanting.
2. The method of claim 1, wherein said implanting uses ions comprising oxygen, silicon, nitrogen, germanium, or carbon.
3. The method of claim 1, wherein said dose at said center is higher than said dose at said periphery.
4. The method of claim 1, wherein said dose at said center is lower than said dose at said periphery.
5. The method of claim 1, wherein said implanting comprises:
performing a first ion implant into said workpiece to form a first plurality of lines;
rotating said workpiece; and
performing a second ion implant into said workpiece to form a second plurality of lines thereby forming a grid with said first plurality of lines and said second plurality of lines.
6. A method of implanting a workpiece comprising:
implanting a workpiece to form at least three implanted regions that are adjacent, wherein a first distance between a first implanted region and a second implanted region is different from a second distance between said second implanted region and a third implanted region; and
growing a compound semiconductor on said workpiece after said implanting.
7. The method of claim 6, wherein said implanting comprises:
performing a first ion implant into said workpiece to form a first plurality of lines;
rotating said workpiece; and
performing a second ion implant into said workpiece to form a second plurality of lines thereby forming a grid with said first plurality of lines and said second plurality of lines.
8. The method of claim 6, wherein said implanted regions are lines.
9. The method claim 8, wherein said lines form a grid.
10. The method of claim 6, wherein said implanted regions are circles.
11. The method of claim 6, wherein said implanting use ions comprising oxygen, silicon, nitrogen, germanium, or carbon.
12. An implanted workpiece comprising:
a workpiece with a plurality of implanted regions, said implanted regions forming a plurality of discrete regions between said implanted regions that are surrounded by said implanted regions; and
a compound semiconductor layer disposed on said workpiece.
13. The implanted workpiece of claim 12, wherein said implanted regions have a dose at a center of said workpiece and a dose at a periphery of said workpiece, said dose at said center of said workpiece being higher than said dose at said periphery of said workpiece.
14. The implanted workpiece of claim 12, wherein said implanted regions have a dose at a center of said workpiece and a dose at a periphery of said workpiece, said dose at said center of said workpiece being lower than said dose at said periphery of said workpiece.
15. The implanted workpiece of claim 12, wherein said implanted regions are lines that form a grid across a surface of said workpiece.
16. The implanted workpiece of claim 12, wherein said implanted regions are circles across a surface of said workpiece.
17. The implanted workpiece of claim 12, wherein said implanted regions comprise at least a first implanted region, second implanted region, and third implanted region that are adjacent, wherein a first distance between said first implanted region and said second implanted region is different from a second distance between said second implanted region and said third implanted region.
18. The implanted workpiece of claim 12, wherein said implanted regions comprise oxygen, silicon, nitrogen, germanium, or carbon.
19. The implanted workpiece of claim 12, wherein said workpiece comprises silicon, sapphire, or SiC.
20. The implanted workpiece of claim 12, wherein said compound semiconductor comprises GaN.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of casting metal strip comprising introducing molten metal between a pair of chilled casting rolls forming a nip between them to form a casting pool of molten metal supported on the rolls and confined at the ends of the nip by pool confining end closures, rotating the rolls so as to cast a solidified strip delivered downwardly from the nip, transporting the strip away from the nip, inspecting the strip as it is transported away from the nip to determine a pattern of thickness variations along the strip due to eccentricities of the casting roll surfaces, and imposing a pattern of speed variation on the rotation of the casting rolls determined by said pattern of thickness variations so as to reduce the amplitude of the thickness variations.
2. A method as claimed in claim 1, wherein said pattern of thickness variations is a regularly repeating pattern.
3. A method as claimed in claim 2, wherein the strip is inspected by an inspection means which produces signals indicative of the frequency and amplitude of repeating thickness variations and the speed of the casting rolls is varied in accordance with those signals.
4. A method as claimed in claim 2, wherein the pattern of imposed speed variations comprises a single variation for each revolution of the casting rolls.
5. A method as claimed in claim 2, wherein the pattern of imposed speed variations includes more than one variation for each revolution of the casting rolls.
6. A method as claimed in claim 1, wherein the rolls are rotated by electric drive motor means and the pattern of imposed speed variations is imposed by feeding said signals directly to the drive motor means.
7. A method as claimed in claim 2, wherein the imposed speed variation is applied at an initial timing phase relative to the rotation of the rolls and the phase is then varied to minimise the amplitude of the thickness variations.
8. A method as claimed claim 1 which further includes the step of varying the average speed of rotation of the rolls throughout the cast to maintain a constant average thickness of the strip.
9. A method as claimed in claim 3, wherein the rolls are rotated by electric drive motor means and the pattern of imposed speed variations is imposed by feeding said signals directly to the drive motor means at an initial timing phase relative to the rotation of the rolls and the phase is then varied to minimise the amplitude of the thickness variations.
10. A method as claimed in claim 9, which includes the step of varying the average speed of rotation of the rolls throughout the cast to maintain a constant average thickness of the strip.
11. Apparatus for casting metal strip comprising a pair of parallel casting rolls forming a nip between them;
a metal delivery system for delivering molten metal into the nip to form a casting pool of molten metal supported above the nip;
a pair of pool confining end closures disposed one at each end of the pair of casting rolls;
roll drive means to rotate the rolls in opposite directions to deliver a cast strip downwardly from the nip;
strip transport means to transport the strip away from the nip;
strip inspection means to inspect the strip as it is transported away from the nip to determine a pattern of thickness variations along the strip due to eccentricities of the casting roll surfaces; and
control means to impose a pattern of speed variations on the rotation of the casting rolls determined by said pattern of thickness variations so as to reduce the amplitude of the thickness variations.
12. Apparatus as claimed in claim 11, wherein the inspection means is operable to generate signals indicative of the frequency and amplitude of the thickness variations and the control means is effective to control operation of the roll drive means in response to those signals.
13. Apparatus as claimed in claim 11, wherein the roll drive means comprises electric motor means and the control means is effective to feed said signals to the electric motor means.
14. Apparatus as claimed in claim 12, wherein the control means is operable to vary the timing phase of the imposed speed variations relative to the rotation of the rolls.
15. Apparatus as claimed in claim 14, wherein the control means is operable to vary the timing phase of the imposed speed variations relative to the rotation of the rolls.