1. A direct detector for terahertz radiation, comprising:
a field-effect transistor formed in a semiconductor substrate, comprising a heterostructure that provides a two-dimensional electron gas in the channel region between the source and the drain of the field-effect transistor, and a periodic split-grating gate comprising a plurality of fingers on a front surface above the channel region, wherein at least one of the fingers of the grating gate is individually biased, to modulate the electron density in the two-dimensional electron gas;
means for applying a gate voltage to the periodic grating gate and a independent gate voltage to the at least one individually biased finger; and
means for detecting an output signal from the field-effect transistor when the front surface is irradiated with terahertz radiation.
2. The direct detector of claim 1, wherein the at least one individually biased finger is biased to near the pinch-off voltage of the channel.
3. The direct detector of claim 1, wherein the heterostructure comprises one or more quantum wells.
4. The direct detector of claim 3, wherein the heterostructure comprises a single quantum well.
5. The direct detector of claim 1, wherein the heterostructure comprises dissimilar II-V compound semiconductors, II-VI compound semiconductors, or Ge\u2014Si alloys.
6. The direct detector of claim 5, wherein the dissimilar III-V compound semiconductors comprise GaAs and AlGaAs.
7. The direct detector of claim 1, wherein the terahertz radiation has a frequency of greater than 100 GHz.
8. The direct detector of claim 1, wherein the detecting means comprises measuring the photoconductive response of the field-effect transistor.
9. The direct detector of claim 1, wherein the detecting means comprises measuring the photovoltaic response of the field-effect transistor.
10. The direct detector of claim 1, further comprising a back gate on the opposite side of the channel region from the grating gate.
11. The direct detector of claim 1, further comprising a transparent front gate on the front surface above the channel region.
12. The direct detector of claim 1, wherein the substrate comprises a thinned substrate.
13. The direct detector of claim 1, further comprising a resistive shunt that connects the fingers of the grating gate in parallel and means for applying a shunt voltage to the resistive shunt.
14. The direct detector of claim 13, wherein the shunt voltage is approximately equal to the source-drain voltage.
15. A direct detector for terahertz radiation, comprising:
a field-effect transistor formed in a semiconductor substrate, comprising a single quantum well that provides a two-dimensional electron gas in the channel region between the source and the drain of the field-effect transistor, and a periodic grating gate comprising a plurality of fingers on a front surface above the channel region to modulate the electron density in the two-dimensional electron gas;
means for applying a gate voltage to the periodic grating gate; and
means for detecting an output signal from the field-effect transistor when the front surface is irradiated with terahertz radiation.
16. The direct detector of claim 15, wherein the single quantum well comprises dissimilar II-V compound semiconductors, II-VI compound semiconductors, or Ge\u2014Si alloys.
17. The direct detector of claim 16, wherein the dissimilar III-V compound semiconductors comprise GaAs and AlGaAs.
18. The direct detector of claim 16, wherein the detecting means comprises measuring the photoconductive response of the field-effect transistor.
19. The direct detector of claim 16, wherein the detecting means comprises measuring the photovoltaic response of the field-effect transistor.
20. The direct detector of claim 16, further comprising a back gate on the opposite side of the channel region from the grating gate.
21. The direct detector of claim 16, further comprising a transparent front gate on the front surface above the channel region.
22. The direct detector of claim 16, wherein the substrate comprises a thinned substrate.
23. The direct detector of claim 16, further comprising a resistive shunt that connects the fingers of the grating gate in parallel and means for applying a shunt voltage to the resistive shunt.
24. A direct detector for terahertz radiation, comprising:
a field-effect transistor formed in a semiconductor substrate, comprising a heterostructure that provides a two-dimensional electron gas in the channel region between the source and the drain of the field-effect transistor, and a periodic grating gate comprising a plurality of fingers on a front surface above the channel region to modulate the electron density in the two-dimensional electron gas;
a resistive shunt that connects the fingers of the grating gate in parallel;
means for applying a shunt voltage to the resistive shunt; and
means for detecting an output signal from the field-effect transistor when the front surface is irradiated with terahertz radiation.
25. The direct detector of claim 24, wherein the shunt voltage is approximately equal to the source-drain voltage.
26. The direct detector of claim 24, wherein the heterostructure comprises one or more quantum wells.
27. The direct detector of claim 24, wherein the detecting means comprises measuring the photoconductive response of the field-effect transistor.
28. The direct detector of claim 24, wherein the detecting means comprises measuring the photovoltaic response of the field-effect transistor.
29. The direct detector of claim 24, further comprising a back gate on the opposite side of the channel region from the grating gate.
30. The direct detector of claim 24, further comprising a transparent front gate on the front surface above the channel region.
31. The direct detector of claim 24, wherein the substrate comprises a thinned substrate.
32. A direct detector for terahertz radiation, comprising:
a field-effect transistor formed in a semiconductor substrate, comprising a heterostructure that provides a two-dimensional electron gas in the channel region between the source and the drain of the field-effect transistor, and a periodic grating gate comprising a plurality of fingers on a front surface above the channel region to modulate the electron density in the two-dimensional electron gas;
means for applying a gate voltage to the periodic grating gate; and
means for detecting a photovoltaic response of the field-effect transistor when the front surface is irradiated with terahertz radiation.
33. The direct detector of claim 32, wherein the heterostructure comprises one or more quantum wells.
34. The direct detector of claim 33, wherein the heterostructure comprises a single quantum well.
35. The direct detector of claim 31, further comprising a back gate on the opposite side of the channel region from the grating gate.
36. The direct detector of claim 31, further comprising a transparent front gate on the front surface above the channel region.
37. The direct detector of claim 31, wherein the substrate comprises a thinned substrate.
38. A direct detector for terahertz radiation, comprising:
a field-effect transistor formed in a thin semiconductor substrate, comprising a heterostructure that provides a two-dimensional electron gas in the channel region between the source and the drain of the field-effect transistor, and a periodic grating gate comprising a plurality of fingers on a front surface above the channel region to modulate the electron density in the two-dimensional electron gas;
means for applying a gate voltage to the periodic grating gate; and
means for detecting an output signal from the field-effect transistor when the front surface is irradiated with terahertz radiation.
39. The direct detector of claim 38, wherein the thickness of the substrate is less than 10 microns.
40. The direct detector of claim 38, wherein the thin semiconductor substrate is suspended by a plurality of legs from an unthinned portion of the substrate.
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 for manufacturing an embossed sheet, in which irregularities on a surface of an emboss roller are formed by transfer on a surface of a sheet-like material, comprising the steps of:
continuously running a flexible strip-shaped sheet-like material, on which a resin solution layer is formed by coating the sheet-like material with a resin solution which is diluted with an organic solvent;
evaporating the organic solvent which is contained in the resin solution layer;
winding the sheet-like material after dried around the emboss roller which is rotating, and then transferring the irregularities of the surface of the emboss roller to the resin solution layer; and
curing the resin solution layer while the sheet-like material is wound around the emboss roller.
2. The method for manufacturing an embossed sheet according to claim 1, wherein
the resin solution is a radiation curable resin solution, and that the resin solution layer is cured by exposing the resin solution layer to a radiation.
3. The method for manufacturing an embossed sheet according to claim 1, wherein
the resin solution contains 10% by weight or more of the organic solvent.
4. The method for manufacturing an embossed sheet according to claim 1, wherein
the resin solution is coated by a die coater, a bar coater, a roll coater, or a gravure coater.
5. The method for manufacturing an embossed sheet according to claim 1, wherein
the resin solution comprises at least the following compounds (A) and (B):
(A) a compound containing a polymerizable group such as an acroyl group andor a vinyl group; and
(B) a compound which generates an active species capable of polymerizing the compound (A) by radiation exposure.
6. The method for manufacturing an embossed sheet according to claim 1, wherein
the resin solution has a viscosity of 100 mPa\xb7s or less when the solution is coated.
7. A method for manufacturing an embossed sheet, in which irregularities on a surface of an emboss roller are formed by transfer on a surface of a sheet-like material, comprising the steps of:
continuously running a flexible strip-shaped sheet-like material, on which a resin solution layer is formed by coating the material with a resin solution which is diluted with an organic solvent;
winding the sheet-like material around the emboss roller which is rotating, and then transferring the irregularities of the surface of the emboss roller to the resin solution layer in which the organic solvent remains; and
curing the resin solution layer while the sheet-like material is wound around the emboss roller.
8. The method for manufacturing an embossed sheet according to claim 7, wherein
the resin solution is a radiation curable resin solution, and that the resin solution layer is cured by exposing the resin solution layer to a radiation.
9. The method for manufacturing an embossed sheet according to claim 7, wherein
the resin solution layer is cured such a state that the resin solution layer contains 1 to 10% by weight of the organic solvent.
10. The method for manufacturing an embossed sheet according to claim 7, wherein
the concentration of the organic solvent is controlled by evaporating the organic solvent within the resin solution, before winding the sheet-like material around the emboss roller which is rotating.
11. The method for manufacturing an embossed sheet according to claim 7, wherein
the concentration of the organic solvent is controlled by evaporating the organic solvent within the resin solution, after releasing the sheet-like material from the emboss roller.
12. The method for manufacturing an embossed sheet according to claim 7, wherein
an irregular pattern which is formed by transfer on the sheet-like material has a pitch of 100 \u03bcm or less.
13. The method for manufacturing an embossed sheet according to claim 7, wherein
the embossed sheet is used as an optical film.
14. An apparatus for manufacturing an embossed sheet, comprising:
a sheet-like material feeding device for feeding a flexible strip-shaped sheet-like material;
a coating device for coating a surface of the sheet-like material with a resin solution which is diluted with an organic solvent;
a drying device for evaporating the organic solvent contained in the resin solution layer;
a transferring device for forming by transfer irregularities of a surface of the emboss roller on the surface of the sheet-like material, while winding the sheet-like material which is continuously running around the emboss roller which is rotating; and
a resin solution curing device for curing the resin solution while the sheet-like material is wound around the emboss roller.
15. An apparatus for manufacturing an embossed sheet, comprising:
a sheet-like material feeding device for feeding a flexible strip-shaped sheet-like material;
a coating device for coating a surface of the sheet-like material with a resin solution which is diluted with an organic solvent;
a first drying device for evaporating the organic solvent contained in the resin solution layer;
a transferring device for forming by transfer irregularities of a surface of the emboss roller on the surface of the sheet-like material, while winding the sheet-like material which is continuously running around the emboss roller which is rotating;
a resin solution curing device for curing the resin solution while the sheet-like material is wound around the emboss roller; and
a second drying device for evaporating the organic solvent contained in the resin solution layer after the layer is cured.
16. The apparatus for manufacturing an embossed sheet according to claim 14, wherein
the resin solution curing device is irradiation device which is provided in proximity to the emboss roller.
17. A method for manufacturing a patterned sheet which has fine patterns, comprising the steps of:
in a situation in which a transfer-receiving material containing an organic solvent and a resin polymer is interposed between a mold for pattern transfer having a predetermined pattern formed thereon and a substrate, bringing the mold for pattern transfer into close contact with the substrate via the transfer-receiving material;
evaporating a portion of the organic solvent which is contained in the transfer-receiving material between the mold for pattern transfer and the substrate; and
releasing a transferred film from the mold for pattern transfer, the transferred film being made of the transfer-receiving material on which fine patterns are formed by transferring the predetermined pattern of the mold for pattern transfer,
wherein, in a case of releasing the transferred film from the mold for pattern transfer, the transferred film which contains the organic solvent is released from the mold for pattern transfer.
18. The method for manufacturing the patterned sheet according to claim 17, wherein,
the concentration of the organic solvent within the transferred film is 5 to 40% by weight ratio when the transferred film is released from the mold for pattern transfer.
19. The method for manufacturing the patterned sheet according to claim 17, wherein
at least one of polymers included in the substrate is soluble in the organic solvent.
20. The method for manufacturing the patterned sheet according to claim 17, wherein
the transfer-receiving material is interposed between the mold for pattern transfer and the substrate, by coating at least either one of the mold for pattern transfer and the substrate with the transfer-receiving material.
21. The method for manufacturing the patterned sheet according to claim 17, in which the transfer-receiving material is interposed between the mold for pattern transfer and the substrate by coating the mold for pattern transfer with the transfer-receiving material, wherein,
at least a periphery of an area on which the transfer-receiving material is coated among the mold for pattern transfer is depressurized when the mold for pattern transfer is coated with the transfer-receiving material.
22. The method for manufacturing the patterned sheet according to claim 17, in which the transfer-receiving material is interposed between the mold for pattern transfer and the substrate by coating the substrate with the transfer-receiving material, wherein
at least a periphery of the transfer-receiving material is depressurized when the mold for pattern transfer is brought into close contact with the substrate via the transfer-receiving material.
23. The method for manufacturing the patterned sheet according to claim 17, in which the transfer-receiving material is interposed between the mold for pattern transfer and the substrate by coating the substrate with the transfer-receiving material, wherein
the mold for pattern transfer is brought into close contact with the substrate via the transfer-receiving material while keeping them with a pressure applied thereon.
24. The method for manufacturing the patterned sheet according to claim 17, wherein
the mold for pattern transfer is a Si workpiece which is derived from a Si substrate processed by using a mask and an etching treatment, or is a replica which is derived from the Si workpiece subjected to electroforming.
25. The method for manufacturing the patterned sheet according to claim 17, wherein
an aspect ratio of a salient of the fine pattern which is formed on the transferred film satisfies the following relational expression: HeightWidth \u22672.
26. The method for manufacturing the patterned sheet according to claim 17, wherein
an area ratio of a salient to a recess of the fine pattern formed on the transferred film satisfies the following relational expression: an area of salientan area of recess \u22660.5.
27. A patterned sheet, wherein the patterned sheet is manufactured in accordance with the method for manufacturing the patterned sheet according to claim 17.