Method for depositing crystalline titania nanoparticles and films

Abstract

The present invention provides a one-step and room-temperature process for depositing nanoparticles or nanocomposite (nanoparticle-assembled) films of 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.

1 . A method for depositing nanoparticles or nanocomposite films of crystalline TiO 2 , comprising:
 providing a target comprised of a titanium-containing material;   providing a substrate to support the deposited particles or films; and   ablating regions of said target with ultrafast laser pulses to create a plume of particles directed toward said substrate.   
     
     
         2 . The method of  claim 1 , wherein the said nanoparticles have sizes of less than 1 micron. 
     
     
         3 . The method of  claim 1 , wherein the said nanocomposite films are films assembled of nanoparticles of crystalline TiO 2 . 
     
     
         4 . The method of  claim 1 , wherein the said nanocomposite films are composed of a host material embedded with nanoparticles of crystalline TiO 2 . 
     
     
         5 . The method of  claim 1 , wherein the said crystalline TiO 2  is in anatase phase or rutile phase or brookite phase or a mixture of any two or all three phases. 
     
     
         6 . The method of  claim 1 , wherein said target includes elemental titanium, and said ablation takes place in an oxygenated atmosphere so that said crystalline TiO 2  is formed subsequent to said ablation. 
     
     
         7 . The method of  claim 1 , further comprising the steps of:
 providing a vacuum chamber containing said target and said substrate, and wherein said ablation step comprises irradiating the target with a laser beam generated by an ultrafast pulsed laser, the said laser beam being processed and focused onto the target by an optical system.   
     
     
         8 . The method of  claim 1  or  7 , wherein the said deposition is performed at a substrate temperature lower than 300° C. 
     
     
         9 . The method of  claim 8 , wherein the said deposition is performed at room temperature. 
     
     
         10 . The method of  claim 1  or  7 , wherein the said substrate is a heat sensitive material, including one of glass, paper, plastic and polymer. 
     
     
         11 . The method of  claim 1  or  7 , wherein the ultrafast pulses have a pulse width of 10 fs-100 ps. 
     
     
         12 . The method of  claim 1  or  7 , wherein the ultrafast pulses each have a pulse energy of 100 nJ-10 mJ. 
     
     
         13 . The method of  claim 7 , wherein the ultrafast pulsed laser has a repetition rate of 1 kHz-100 MHz. 
     
     
         14 . The method of  claim 7 , wherein the ultrafast pulsed laser and the optical system enable a laser fluence in the range of 10 mJ/cm 2 -100 J/cm 2 , at the target surface. 
     
     
         15 . The method of  claim 7 , wherein the optical system processes the intensity distribution of the laser beam from a Gaussian profile to a ‘flat-top’ profile. 
     
     
         16 . The method of  claim 1  or  7 , wherein the said target is a metal containing titanium or an oxide containing titanium oxide. 
     
     
         17 . The method of  claim 1  or  7 , wherein said target includes titanium oxide and deposition onto said substrate takes place in vacuum or in background gas(es) containing oxygen. 
     
     
         18 . The method of  claim 7 , wherein said target includes elemental titanium and the step of performing laser ablation takes place within background gas(es) containing oxygen.