What is claimed is:
1. A method of applying a decorative wheel cover to a wheel rim, comprising the steps of:
a) providing an uncured precursor composition, said precursor composition having a quantity of spacer particles dispersed therein;
b) applying said precursor composition to a rear face of said wheel cover or to an outboard surface of said wheel rim, or both;
c) applying said wheel cover to said wheel rim such that a layer of said precursor composition is sandwiched in a gap between said wheel cover and said wheel rim;
d) press-fitting said wheel cover to said wheel rim until said gap therebetween is reduced to substantially the diameter of said spacer particles, said precursor composition layer thereby being reduced to a final thickness substantially equal to the diameter of said spacer particles; and
e) curing said precursor composition layer to form a cured adhesive layer disposed between said wheel rim and said wheel cover.
2. A method according to claim 1, said cured adhesive layer having a substantially uniform thickness that is substantially equal to the diameter of said spacer particles.
3. A method according to claim 1, wherein further reduction of said gap in step (d) is inhibited by the presence of said spacer particles.
4. A method according to claim 1, said rear face of said wheel cover having a surface contour that is complementary to a surface contour of at least a portion of said outboard surface of said wheel rim.
5. A method according to claim 1, said wheel cover having a configuration substantially conforming to the shape and contour of said outboard surface of said wheel rim.
6. A method according to claim 5, said wheel rim having a plurality of openings therein, said wheel rim being provided with corresponding openings that are substantially in register with said openings in said wheel rim when the wheel cover is applied to said wheel rim.
7. A method according to claim 1, said adhesive layer comprising a silicone material, said precursor composition being moisture-cured and comprising a silicone material.
8. A method according to claim 7, said adhesive layer comprising oxime silicone rubber, said precursor composition being a single component, moisture-cured composition that comprises oxime silicone.
9. A method according to claim 1, said precursor composition having sufficient green strength to retain said wheel cover on said wheel rim following said press-fitting step until said precursor composition has fully cured to form said adhesive layer.
10. A method according to claim 1, said precursor composition having a viscosity of 20,000-50,000 cps.
11. A method according to claim 1, said precursor composition having a through cure time of about 24 hours or less for a layer that is inch thick at 50% R.H. and 77 F.
12. A method according to claim 1, said spacer particles having a particle diameter of about 0.01 inch to about 0.125 inch.
13. A method according to claim 12, said spacer particles having a particle diameter of 0.02-0.1 inch.
14. A method according to claim 12, said spacer particles having a particle diameter of about 0.03 inches.
15. A method according to claim 1, said spacer particles having a specific gravity substantially equal to the specific gravity of said uncured precursor composition.
16. A method according to claim 1, said spacer particles having a particle size distribution not more than 0.02 inch.
17. A method according to claim 1, said precursor composition comprising 0.01-5 weight percent spacer particles.
18. A method according to claim 1, said precursor composition comprising a weight percent of spacer particles that is adjusted to accommodate the weight of said wheel cover andor the stresses that said wheel cover will encounter.
19. A method according to claim 1, said precursor composition layer having about one spacer particle per square inch of said precursor composition layer at said final thickness thereof, said cured adhesive layer correspondingly having about one spacer particle per square inch thereof.
20. A method according to claim 1, said spacer particles being selected from the group consisting of silica gel beads, polypropylene copolymer particles, ethylene vinyl acetate particles and particles of other resins.
21. A method according to claim 1, said wheel cover being made from metal or plastic.
22. A method according to claim 1, wherein at least one of said steps (b), (c) and (d) is performed by automated equipment.
23. A kit comprising a decorative wheel cover and an uncured precursor composition, said decorative wheel cover being adapted to be applied to a wheel rim, said uncured precursor composition having a quantity of spacer particles dispersed therein, said uncured precursor composition being curable to form a cured adhesive layer between said decorative wheel cover and said wheel rim, said cured adhesive layer being effective to retain said wheel cover on said wheel rim.
24. A kit according to claim 23, further comprising said wheel rim.
25. A kit according to claim 23, said uncured precursor composition being a moisture-cured precursor composition.
26. A kit according to claim 23, said cured adhesive layer comprising silicone, said uncured precursor composition being a moisture-cured composition that comprises silicone.
27. A kit according to claim 26, said adhesive layer comprising an oxime silicone material, said uncured precursor composition comprising an oxime silicone material.
28. A kit according to claim 23, said spacer particles having a particle diameter of about 0.01 inch to about 0.125 inch.
29. A kit according to claim 23, said spacer particles having a particle diameter of 0.02-0.1 inch.
30. A kit according to claim 23, said spacer particles having a particle diameter of about 0.03 inches.
31. A kit according to claim 23, said spacer particles having a specific gravity substantially equal to the specific gravity of said uncured precursor composition.
32. A kit according to claim 23, said spacer particles having a particle size distribution not more than 0.02 inch.
33. A kit according to claim 23, said uncured precursor composition having 0.01-5 weight percent spacer particles.
34. A kit according to claim 23, said spacer particles being selected from the group consisting of silica gel beads, polypropylene copolymer particles, ethylene vinyl acetate particles and particles of other resins.
35. A kit according to claim 23, said uncured precursor composition being provided in a squeezable tube.
36. An automobile wheel comprising a wheel rim and a decorative wheel cover adhered to said wheel rim via a cured adhesive layer disposed therebetween, said cured adhesive layer having a quantity of spacer particles therein, said adhesive layer having an adhesive layer thickness that is substantially equal to a diameter of said spacer particles.
37. An automobile wheel according to claim 36, said adhesive layer thickness being substantially uniform throughout said cured adhesive layer.
38. An automobile wheel according to claim 36, said spacer particles having a particle diameter of about 0.01 inch to about 0.125 and a particle size distribution not more than 0.02 inch.
39. A method of applying a decorative wheel cover to a wheel rim via a foam adhesive layer, comprising the steps of:
a) providing an uncured silicone precursor composition, said precursor composition having a quantity of spacer particles dispersed therein;
b) applying said precursor composition to a rear face of said wheel cover or to an outboard surface of said wheel rim, or both, said precursor composition being applied in a bead surrounding an opening or structure into or adjacent to which foam expansion is to be avoided;
c) applying said wheel cover to said wheel rim such that said bead of precursor composition is sandwiched in a gap between said wheel cover and said wheel rim;
d) press-fitting said wheel cover to said wheel rim until said gap therebetween is reduced to substantially the diameter of said spacer particles, said bead of precursor composition thereby being reduced to a final thickness substantially equal to the diameter of said spacer particles;
e) curing said bead of precursor composition to form a cured silicone barrier surrounding said opening or structure, said silicone barrier being disposed between said wheel rim and said wheel cover; and
f) providing a foaming composition in said gap between said wheel cover and said wheel rim, wherein said foaming composition reacts to form a foam adhesive layer within said gap, said cured silicone barrier effectively preventing expansion of said foam into or adjacent said opening or structure that is surrounded by said cured silicone barrier.
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 semiconductor material comprising:
a silicon substrate;
a compositionally-graded transition layer formed over the silicon substrate; and
a gallium nitride material layer formed over the transition layer.
2. The semiconductor material of claim 1, wherein the composition of the transition layer is graded continuously across the thickness of the layer.
3. The semiconductor material of claim 1, wherein the composition of the transition layer is graded discontinuously across the thickness of the layer.
4. The semiconductor material of claim 1, wherein the transition layer comprises an alloy of gallium nitride selected from the group consisting of AlxInyGa(1-x-y)N, InyGa(1-y)N, and AlxGa(1-x)N.
5. The semiconductor material of claim 4, wherein the concentration of gallium in the transition layer is graded.
6. The semiconductor material of claim 4, wherein x andor y is varied from a first value at a back surface of the transition layer to a second value at a front surface of the transition layer, wherein the back surface is closer to the substrate than the front surface.
7. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the back surface is greater than 0.4.
8. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the back surface is greater than 0.8.
9. The semiconductor material of claim 6, wherein the transition layer comprises AlxIn(1-x)N at the back surface of the transition layer in contact with the silicon substrate.
10. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the front surface is less than 0.3.
11. The semiconductor material of claim 6, wherein the transition layer comprises GaN at a front surface of the transition layer in contact with the gallium nitride material layer and is free of gallium at a back surface of the transition layer in contact with the substrate.
12. The semiconductor material of claim 4, wherein the transition layer comprises AlxGa(1-x)N.
13. The semiconductor material of claim 4, wherein the value of x decreases in a direction away from the silicon substrate.
14. The semiconductor material of claim 4, wherein the value of y remains constant across the transition layer.
15. The semiconductor material of claim 1, wherein the transition layer comprises a superlattice.
16. The semiconductor material of claim 15, wherein the superlattice includes a series of alternating AlxInyGa(1-x-y)N and AlaInbGa(1-a-b)N layers.
17. The semiconductor material of claim 16, wherein the of value of x, y, a, and b are constant across respective layers and the thickness of the respective layers is varied across the transition layer.
18. The semiconductor material of claim 1, wherein the transition layer has a thickness between about 0.03 micron and about 20 microns.
19. The semiconductor material of claim 1, wherein the gallium nitride material layer comprises GaN.
20. The semiconductor material of claim 1, wherein the gallium nitride material layer comprises AlxInyGa(1-x-y)N.
21. The semiconductor material of claim 1, wherein the gallium nitride material layer has a thickness of greater than 0.75 micron.
22. The semiconductor material of claim 1, wherein the semiconductor material forms a semiconductor device.
23. The semiconductor material of claim 22, wherein the semiconductor material forms an LED.
24. The semiconductor material of claim 22, wherein the semiconductor material forms a laser diode.
25. The semiconductor material of claim 22, wherein the semiconductor material forms a FET.
26. The semiconductor material of claim 1, wherein the gallium nitride material layer has a crack level of less than 0.005 mm2.
27. The semiconductor material of claim 1, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
28. The semiconductor material of claim 1, wherein the gallium nitride material layer is substantially free of cracks.
29. The semiconductor material of claim 1, wherein the gallium nitride material layer is monocrystalline.
30. The semiconductor material of claim 1, wherein the silicon substrate has a thickness of greater than 250 micron.
31. The semiconductor material of claim 1, wherein the silicon substrate is textured.
32. The semiconductor material of claim 1, further comprising an intermediate layer formed over the silicon substrate and under the transition layer.
33. The semiconductor material of claim 1, wherein the intermediate layer has a constant composition.
34. The semiconductor material of claim 1, wherein the intermediate layer comprises an alloy of gallium nitride selected from the group consisting of AlxInyGa1-x-y)N, InyGa(1-y)N, and AlxGa(1-x)N.
35. The semiconductor material of claim 1, wherein the silicon substrate comprises a silicon wafer.
36. A semiconductor material comprising:
a silicon substrate;
a gallium nitride material layer formed over the silicon substrate, the gallium nitride material layer having a crack level of less than 0.005 mm2.
37. The semiconductor material of claim 36, wherein the gallium nitride material layer comprises GaN.
38. The semiconductor material of claim 36, wherein the gallium nitride material layer comprises an alloy of gallium nitride selected from the group consisting of AlxInyGa(1-x-y)N, InyGa(1-y)N, and AlxGa(1-x)N.
39. The semiconductor material of claim 36, wherein the gallium nitride material layer has a thickness of greater than 0.5 micron.
40. The semiconductor material of claim 36, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.
41. The semiconductor material of claim 36, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
42. The semiconductor material of claim 36, wherein the gallium nitride material layer is substantially free of cracks.
43. The semiconductor material of claim 36, wherein the gallium nitride material layer is monocrystalline.
44. The semiconductor material of claim 36, wherein the silicon substrate comprises a silicon wafer.
45. A semiconductor structure comprising:
a silicon substrate; and
a gallium nitride material layer formed over the silicon substrate and having a thickness of greater than 0.5 micron,
wherein the semiconductor structure forms a semiconductor device.
46. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.
47. The semiconductor material of claim 45, wherein the silicon substrate comprises a silicon wafer.
48. The semiconductor structure of claim 45, wherein the semiconductor structure forms an LED.
49. The semiconductor structure of claim 45, wherein the semiconductor structure forms a laser diode.
50. The semiconductor structure of claim 45, wherein the semiconductor structure forms a FET.
51. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a crack level of less than 0.005 mm2.
52. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
53. The semiconductor structure of claim 45, wherein the gallium nitride material layer is substantially free of cracks.
54. A method of producing a semiconductor material comprising:
forming a compositionally-graded transition layer over a silicon substrate; and
forming a gallium nitride material layer over the transition layer.
55. The method of claim 54, wherein the composition of the transition layer is graded continuously across the thickness of the layer.
56. The method of claim 54, wherein the transition layer comprises an alloy of gallium nitride selected from the group consisting of AlxInyGa(1-x-y)N, InyGa(1-y)N, and AlxGa(1-x)N.
57. The method of claim 54, wherein the concentration of gallium in the transition layer is graded.
58. The method of claim 56, wherein the value of x decreases in a direction away from the silicon substrate.
59. The method of claim 56, wherein the transition layer comprises AlxGa(1-x)N.
60. The method of claim 54, wherein the transition layer comprises a superlattice including a series of alternating AlxInyGa(1-x-y)NAlaInbGa(1-a-b)N layers.
61. The method of claim 54, wherein the gallium nitride material layer comprises GaN.
62. The method of claim 54, wherein the gallium nitride material layer comprises AlxInyGa(1-x-y)N.
63. The method of claim 54, further comprising processing the semiconductor material to form at least one semiconductor device.
64. The method of claim 54, wherein the gallium nitride material layer has a crack level of less than 0.005 mm2.
65. The method of claim 54, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
66. The method of claim 54, wherein the gallium nitride material layer is substantially free of cracks.
67. The method of claim 54, wherein the gallium nitride material layer is monocrystalline.
68. The method of claim 54, further comprising forming an intermediate layer over the silicon substrate and under the transition layer.
69. A method of producing a semiconductor material comprising:
forming a gallium nitride material layer formed over a silicon substrate, the gallium nitride material layer having a crack level of less than 0.005 mm2.
70. The method of claim 69, wherein the gallium nitride material layer comprises GaN.
71. The method of claim 69, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.
72. The method of claim 69, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
73. The method of claim 69, wherein the gallium nitride material layer is substantially free of cracks.
74. The method of claim 69, wherein the gallium nitride material layer is monocrystalline.
75. A method of forming a semiconductor structure comprising:
forming a semiconductor structure comprising a silicon substrate, and a gallium nitride material layer formed over the silicon substrate and having a thickness of greater than 0.5 micron.
76. The method of claim 75, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.
77. The method of claim 75, wherein the gallium nitride material layer has a thickness of greater than 2.0 microns.
78. The method of claim 75, wherein the semiconductor structure forms an LED.
79. The method of claim 75, wherein the semiconductor structure forms a laser diode.
80. The method of claim 75, wherein the semiconductor structure forms a FET.
81. The method of claim 75, wherein the gallium nitride material layer has a crack level of less than 0.005 mm2.
82. The method of claim 75, wherein the gallium nitride material layer has a crack level of less than 0.001 mm2.
83. The method of claim 75, wherein the gallium nitride material layer is substantially free of cracks.
84. A semiconductor material comprising:
a silicon (100) substrate; and
a gallium nitride material layer having a Wurtzite structure formed over the silicon substrate.
85. The semiconductor material of claim 84, further comprising a compositionally-graded transition layer formed between the silicon (100) substrate and the gallium nitride material layer.