Method for depositing crystalline titania nanoparticles and films

Abstract

A one-step and room-temperature process for depositing nanoparticles or nanocomposite (nanoparticle-assembled) films of metal oxides such as crystalline titanium dioxide (TiO 2 ) onto a substrate surface using ultrafast pulsed laser ablation of Titania or metal titanium target. The system includes a pulsed laser with a pulse duration ranging from a few femtoseconds to a few tens of picoseconds, an optical setup for processing the laser beam such that the beam is focused onto the target surface with an appropriate average energy density and an appropriate energy density distribution, and a vacuum chamber in which the target and the substrate are installed and background gases and their pressures are appropriately adjusted.

We claim: 
     
         1 . An article of manufacturing comprising: a substrate comprising a heat-sensitive material having nanoparticles or nanocomposite films of crystalline metal oxide deposited thereon. 
     
     
         2 . The article of  claim 1 , wherein said article comprises: functional nanoparticles or functional nanocomposite films of crystalline Ti 02 . 
     
     
         3 . The article of  claim 1  wherein said nanoparticles or nanocomposite films of crystalline metal oxide are characterized by exhibiting a thermally stable rutile phase subsequent to deposition onto said substrate at said temperature and said background pressure. 
     
     
         4 . An article of manufacturing comprising: a substrate comprising a heat-sensitive material having nanoparticles or nanocomposite films of crystalline metal oxide deposited thereon, where said article is made by a method comprising providing a target comprised of a metal or metal-oxide material; providing a substrate to support the deposited nanoparticles of crystalline metal oxide or films of crystalline metal oxide; and ablating regions of said target with ultrafast laser pulses to create a plume of particles directed toward said substrate , and thereby depositing said nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxide onto said substrate, wherein said depositing step is performed in the absence of substrate heating , at approximately room temperature, and at a pressure of about 100 Pa or less. 
     
     
         5 . The article of  claim 3 , wherein said substrate comprises at least one of glass, plastic, paper, and a polymer film. 
     
     
         6 . A system for depositing nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxide onto a substrate, said system comprising:
 a source of ultrafast laser pulses;   a target comprised of a metal or metal-oxide material;   a substrate to support the deposited nanoparticles of crystalline metal oxide or films of crystalline metal oxide, wherein said nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxides comprise: titanium oxides, nickel oxides, zinc oxides, tin oxides, cobalt oxides, or copper oxides; and   wherein ablated regions of said target with said ultrafast laser pulses creates a plume of particles directed toward said substrate to deposit said nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxide onto said substrate, wherein said deposit onto said substrate is absent substrate heating, at approximately room temperature, and at a low pressure of about 100 Pa or less.   
     
     
         7 . The system of  claim 6 , wherein crystallinity of said nanoparticles of crystalline TiO 2  or nanocomposite films of crystalline TiO 2  formed at ambient or room temperature is characterized by having one or more referenced peaks in an detectable by X-ray diffraction (XRD) pattern or electron diffraction pattern. 
     
     
         8 . The system of  claim 6 , further comprising:
 a target manipulator to position at least one target comprised of a metal or metal-oxide material;   a substrate manipulator to position at least one substrate provided to support said deposited nanoparticles or films; and   an optical system to focus and deliver said pulses to said at least one target.   
     
     
         9 . The system of  claim 6  wherein an ultrafast pulse width is in the range of about 10 fs to 100 ps, and a fluence of an ultrafast pulse at a surface of said target is in the range of about 0.01 J/cm 2  to 2 J/cm 2 . 
     
     
         10 . The system of  claim 6 , wherein said depositing is performed at a substrate temperature lower than 300° C. 
     
     
         11 . The system of  claim 6 , wherein the ultrafast pulses each have a pulse width of 10 fs-100 ps. 
     
     
         12 . The system of  claim 6 , wherein the ultrafast pulses each have a pulse energy of 100 nJ-10 mJ. 
     
     
         13 . The system of  claim 6 , wherein the ultrafast laser and the optical system provide laser fluence in the range of 10 mJ/cm 2 -100 J/cm 2 , at the target surface. 
     
     
         14 . The system of  claim 6 , wherein said target material is ablated without forced condensation of the ablated vapor and without a high pressure background gas. 
     
     
         15 . A method for depositing nanoparticles or nanocomposite films of crystalline metal oxide onto a substrate, said method comprising:
 providing a target comprised of a metal or metal-oxide material;   providing a substrate to support the deposited particles or films of crystalline metal oxide; and   ablating regions of said target with ultrafast laser pulses to create a plume of particles directed toward said substrate, wherein:   said substrate comprises a heat sensitive material, and said step of ablating produces a temperature at the substrate sufficiently low to substantially avoid thermal induced alteration of a substrate property, such that a film is formable on the heat sensitive material;   said temperature is approximately room temperature;   said nanoparticles or nanocomposite films of crystalline metal oxides comprise:   titanium oxides, nickel oxides, zinc oxides, tin oxides, cobalt oxides, or copper oxides; and   an ultrafast pulse width is in the range of about 10 fs to 100 ps, and a fluence of an ultrafast pulse at a surface of said target is in the range of about 0.01 J/cm 2  to 2 J/cm 2 .   
     
     
         16 . The method of  claim 15 , wherein the said nanocomposite films are films assembled of nanoparticles of crystalline TiO 2 . 
     
     
         17 . The method of  claim 15 , wherein the said nanocomposite films are composed of a host material embedded with nanoparticles of crystalline TiO 2 . 
     
     
         18 . The method of  claim 15 , wherein crystallinity of said nanoparticles or nanocomposite films formed at room temperature is detectable by X-ray diffraction (XRD) or electron diffraction. 
     
     
         19 . The method of  claim 15 , wherein the said substrate is a heat sensitive material, including one of glass, paper, plastic and polymer. 
     
     
         20 . The method of  claim 15  wherein said substrate comprises a heat sensitive material, and said step of ablating produces a temperature at the substrate sufficiently low to avoid thermal induced alteration of a substrate property, such that a film is formable on the heat sensitive material. 
     
     
         21 . The method of  claim 15 , wherein crystallinity of said nanoparticles or nanocomposite films formed at room temperature is characterized by having one or more referenced peaks in an X-ray diffraction (XRD) pattern or electron diffraction pattern. 
     
     
         22 . The method of  claim 15 , wherein said method is performed in the absence of substrate heating, and at a background pressure of about 100 Pa or less and, at said room temperature and at said background pressure of about 100 Pa or less, said method can produce functional nanoparticles or functional nanocomposite films of crystalline TiO2 which exhibit a thermally stable rutile phase subsequent to deposition onto said substrate at said temperature and said background pressure. 
     
     
         23 . The method of  claim 22 , wherein said functional nanoparticles or films produced with said method are characterized by having catalytic activity associated with the crystallinity of individual nanoparticles. 
     
     
         24 . The method of  claim 23 , wherein said functional nanoparticles or films produced with said method form a portion of a photocatalyst. 
     
     
         25 . The method of  claim 24 , wherein said functional nanoparticles or films produced with said method are configured as a portion of a gas sensor, an electrochromic device, a solar cell, and/or a photocatalyst. 
     
     
         26 . An ultrashort laser based method for depositing nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxide, comprising:
 ablating regions of a target with ultrashort laser pulses, wherein an ultrashort pulse width is in the range of about 10 fs to 100 ps, and a fluence of an ultrashort pulse at a surface of said target is in the range of about 0.01 J/cm 2  to 2 J/cm 2 , to create a plume of particles directed toward a substrate, and   depositing said nanoparticles of crystalline metal oxide or nan composite films of crystalline metal oxide onto said substrate, wherein:   said depositing step is performed in the absence of substrate heating, at approximately room temperature, and at a background pressure of about 100 Pa or less, at said room temperature and at said background pressure of about 100 Pa or less, said method can produce functional nanoparticles or functional nanocomposite films of crystalline metal oxide which exhibit a thermally stable rutile phase subsequent to deposition at said temperature and said background pressure.   
     
     
         27 . The method of  claim 26 , wherein said nanoparticles of crystalline metal oxide or nanocomposite films of crystalline metal oxide comprise TiO 2 .