Methods and apparatus for selective, oxidative patterning of a surface

Abstract

The present invention provides methods and apparatus for selectively patterning surfaces using radical species generated with a photocatalyst. The photocatalyst may comprise a photocatalytic semiconductor or a photosensitizer. The radical species are brought into contact with an oxidizable coating disposed on the surface, thereby locally oxidizing and selectively patterning the surface. The photocatalyst is preferably disposed on a delivery device, such as a stamp, mask, or scanning probe, that is brought into close proximity or contact with the coated surface. The photocatalyst is then excited in a manner capable of generating radical species, for example, oxygen-containing radical species, in appropriate media. It is expected that these radical species will be transferred to the coated surface along a substantially shortest distance path, thereby locally oxidizing and patterning the surface.

What is claimed is:  
     
         1 . Apparatus for selectively patterning an oxidizable surface, the apparatus comprising: 
 a photocatalyst;    a medium in communication with the photocatalyst and the oxidizable surface; and    an energy source adapted to excite the photocatalyst,    wherein the photocatalyst generates radical species in the medium upon excitation by the energy source.    
     
     
         2 . The apparatus of  claim 1 , wherein the oxidizable surface comprises an oxidizable coating disposed on the surface.  
     
     
         3 . The apparatus of  claim 1 , wherein the photocatalyst comprises a photocatalytic semiconductor adapted to generate electron hole pairs upon excitation by the energy source, and wherein the electron hole pairs generate the radical species in the medium.  
     
     
         4 . The apparatus of  claim 1 , wherein the medium is adapted to transport the radical species from the photocatalyst to the oxidizable surface.  
     
     
         5 . The apparatus of  claim 1 , wherein the radical species are adapted to locally oxidize the the oxidizable surface at points where the radical species contact the surface.  
     
     
         6 . The apparatus of  claim 5 , wherein locally oxidizing the oxidizable surface comprises locally pattering the surface.  
     
     
         7 . The apparatus of  claim 3 , wherein excitation of the photocatalytic semiconductor by the energy source comprises excitation above a band gap of the photocatalytic semiconductor.  
     
     
         8 . The apparatus of  claim 1 , wherein the photocatalyst is chosen from the group consisting of photocatalytic semiconductors, TiO 2 , SnO 2 , compounds of InTaO 4  doped with Ni, photosensitizers, photofrins, texaphyrins, metallotexaphyrins, porphyrins, hematoporphyrins, chlorins, bacteriochlorins, phthalocyanines, purpurins, and combinations thereof.  
     
     
         9 . The apparatus of  claim 1  further comprising a delivery device on which the photocatalyst is disposed.  
     
     
         10 . The apparatus of  claim 9 , wherein the delivery device is chosen from the group consisting of stamps, masks, probes, scanning probes, and combinations thereof.  
     
     
         11 . The apparatus of  claim 9 , wherein the photocatalyst is disposed on the delivery device in a specified pattern.  
     
     
         12 . The apparatus of  claim 11 , wherein the specified pattern comprises a pattern chosen from the group consisting of an entirety of the delivery device, a 2-dimensionally patterned section of the delivery device, a 3-dimensionally patterned section of the delivery device, a tip of a scanning probe, a localized region of the delivery device, and combinations thereof.  
     
     
         13 . The apparatus of  claim 11 , wherein the specified pattern is fabricated using e-beam lithography.  
     
     
         14 . The apparatus of  claim 1 , wherein the energy source is chosen from the group consisting of visible light sources, UV sources, x-ray sources, visible light lamps, UV lamps, x-ray lamps, mercury lamps, visible light lasers, HeNe lasers, UV lasers, x-ray lasers, pulsed lamps, pulsed lasers, and combinations thereof.  
     
     
         15 . The apparatus of  claim 1 , wherein the oxidizable surface comprises a surface chosen from the group consisting of alkane thiols, thioethers, unsaturated materials, saturated materials, bare metal surfaces, metal oxides, and combinations thereof.  
     
     
         16 . The apparatus of  claim 9  further comprising a second photocatalyst disposed on the delivery device.  
     
     
         17 . The apparatus of  claim 11 , wherein the delivery device inhibits transmission of excitation energy provided by the energy source outside of the specified pattern.  
     
     
         18 . The apparatus of  claim 1 , wherein the medium comprises a fluid medium.  
     
     
         19 . The apparatus of  claim 1 , wherein the medium comprises an oxidant chosen from the group consisting of oxygen, nitrogen, oxidizing ions, Redox species, Redox mediators, electron transfer agents, and combinations thereof.  
     
     
         20 . The apparatus of  claim 1 , wherein the medium comprises a medium chosen from the group consisting of gaseous mediums, liquid mediums, aqueous mediums, organic mediums, inorganic mediums, water, gels, air, oxygen-containing mediums, nitrogen-containing mediums, thiohexamic ester-containing mediums, Argon gas, vacuum, and combinations thereof.  
     
     
         21 . The apparatus of  claim 1  further comprising a stabilizing agent.  
     
     
         22 . The apparatus of  claim 21 , wherein the stabilizing agent is chosen from the group consisting of selenium, zinc, lipoic acid, methionine, cysteine, N,N Dimethyl glycine, and combinations thereof.  
     
     
         23 . A method for selectively patterning an oxidizable surface, the method comprising: 
 providing a photocatalyst in close proximity or contact to the surface;    exciting the photocatalyst;    generating radical species with the excited photocatalyst;    transferring the radical species to the surface; and    locally oxidizing the surface at points where the radical species contact the surface, thereby selectively patterning the surface.    
     
     
         24 . The method of  claim 23 , wherein the photocatalyst comprises a photocatalytic semiconductor, and wherein exciting the photocatalyst comprises forming electron hole pairs in or on the photocatalytic semiconductor.  
     
     
         25 . The method of  claim 24 , wherein forming electron hole pairs in or on the photocatalytic semiconductor comprises exciting the photocatalytic semiconductor above its band gap.  
     
     
         26 . The method of  claim 24 , wherein generating radical species with the excited photocatalyst comprises generating radical species with the electron hole pairs.  
     
     
         27 . The method of  claim 26 , wherein generating radical species with the electron hole pairs comprises generating species by contacting the electron hole pairs with a medium in communication with the photocatalytic semiconductor.  
     
     
         28 . The method of  claim 23 , wherein the photocatalyst comprises a photosensitizer.  
     
     
         29 . The method of  claim 23 , wherein transferring the radical species to the surface comprises transferring the radical species to the surface through a medium.  
     
     
         30 . The method of  claim 23 , wherein the medium comprises a fluid having an oxidant.  
     
     
         31 . The method of  claim 23 , wherein providing a photocatalyst comprises providing a photocatalyst chosen from the group consisting of photocatalytic semiconductors, TiO 2 , SnO 2 , compounds of InTaO 4  doped with Ni, photosensitizers, photofrins, texaphyrins, metallotexaphyrins, porphyrins, hematoporphyrins, chlorins, bacteriochlorins, phthalocyanines, purpurins, and combinations thereof.  
     
     
         32 . The method of  claim 23 , wherein providing a photocatalyst comprises providing a photocatalyst disposed on a delivery device.  
     
     
         33 . The method of  claim 32 , wherein providing a photocatalyst disposed on a delivery device comprises providing a photocatalyst disposed on a delivery device chosen from the group consisting of stamps, masks, probes, scanning probes, and combinations thereof.  
     
     
         34 . The method of  claim 23 , wherein locally oxidizing the surface comprises locally oxidizing a surface chosen from the group consisting of alkane thiols, thioethers, unsaturated materials, saturated materials, bare metal surfaces, metal oxides, and combinations thereof.  
     
     
         35 . The method of  claim 23  further comprising: 
 providing a second photocatalyst in close proximity or contact to the surface;  
 exciting the second photocatalyst;  
 generating a second set of radical species with the second excited photocatalyst;  
 transferring the second set of radical species to the surface; and  
 locally oxidizing the surface at points where the second set of radical species contact the surface, thereby selectively patterning the surface with a second pattern.  
 
     
     
         36 . The method of  claim 35 , wherein the photocatalyst and the second photocatalyst comprise different photocatalysts.  
     
     
         37 . The method of  claim 23 , wherein selectively patterning the surface comprises selectively patterning the surface with a pattern chosen from the group consisting of positive patterns, negative patterns, continuous patterns, discontinuous patterns, multi-step patterns, one-dimensional patterns, two-dimensional patterns, three-dimensional patterns, and combinations thereof.  
     
     
         38 . The apparatus of  claim 1 , wherein a bias voltage is applied to the oxidizable surface.  
     
     
         39 . A patterned surface made by a process comprising: 
 generating radical species with a photocatalyst; and    locally oxidizing the surface with the radical species to pattern the surface.    
     
     
         40 . The patterned surface made by the process of  claim 39 , wherein generating radical species with the photocatalyst further comprises generating radical species with a photocatalytic semiconductor.  
     
     
         41 . The patterned surface made by the process of  claim 40 , wherein generating radical species with the photocatalytic semiconductor further comprises forming electron hole pairs in the photocatalytic semiconductor that form radical species upon exposure to appropriate media.  
     
     
         42 . The patterned surface made by the process of  claim 39 , wherein generating radical species with the photocatalyst further comprises generating radical species with a photosensitizer.  
     
     
         43 . The patterned surface made by the process of  claim 39 , wherein generating radical species with the photocatalyst further comprises exciting the photocatalyst with an energy source.  
     
     
         44 . The patterned surface made by the process of  claim 39 , wherein locally oxidizing the surface with the radical species to pattern the surface comprises patterning the surface with features having a size smaller than about 100 nm.  
     
     
         45 . The patterned surface made by the process of  claim 39 , wherein locally oxidizing the surface with the radical species to pattern the surface comprises patterning the surface with a resolution finer than about 100 nm.  
     
     
         46 . The patterned surface made by the process of  claim 39 , wherein generating radical species with the photocatalyst further comprises generating radical species with a photocatalyst disposed on a delivery device.  
     
     
         47 . The patterned surface made by the process of  claim 46 , wherein generating radical species with a photocatalyst disposed on a delivery device further comprises generating radical species with a photocatalyst disposed on a delivery device chosen from the group consisting of stamps, masks, probes, scanning probes, and combinations thereof.  
     
     
         48 . The patterned surface made by the process of  claim 46 , wherein generating radical species with a photocatalyst disposed on a delivery device further comprises generating radical species with a photocatalyst disposed on a delivery device in a specified pattern.  
     
     
         49 . The patterned surface made by the process of  claim 48 , wherein generating radical species with a photocatalyst disposed on a delivery device in a specified pattern further comprises generating radical species with a photocatalyst disposed on a delivery device in a specified pattern that has features with a size smaller than 100 nm.  
     
     
         50 . The patterned surface made by the process of  claim 48 , wherein locally oxidizing the surface with the radical species to pattern the surface comprises transferring the radical species from the specified pattern on the delivery device to the surface along a substantially shortest distance path.  
     
     
         51 . The patterned surface made by the process of  claim 39 , wherein generating radical species with a photocatalyst further comprises generating radical species with a photocatalyst chosen from the group consisting of photocatalytic semiconductors, TiO 2 , SnO 2 , compounds of InTaO 4  doped with Ni, photosensitizers, photofrins, texaphyrins, metallotexaphyrins, porphyrins, hematoporphyrins, chlorins, bacteriochlorins, phthalocyanines, purpurins, and combinations thereof.