Abstract:
This invention is a new class of materials having altered properties. In particular, materials having a surface structure causing electron De Broglie wave interference are described which result in a change in distribution of quantum states within the materials. The materials of the present invention have at least one surface having at least one indent or protrusion to cause electron De Broglie wave interference within the material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part application of application Ser. No. 10/508,914 filed Sep. 22, 2004, which is a U.S. national stage application of International Application PCT/US03/08907, filed Mar. 24, 2003, which international application was published on Oct. 9, 2003, as International Publication WO03083177 in the English language. The International Application claims the benefit of U.S. Provisional Application No. 60/366,563, filed Mar. 22, 2002, U.S. Provisional Application No. 60/366,564, filed Mar. 22, 2002, and U.S. Provisional Application No. 60/373,508, filed Apr. 17, 2002. This application is also a continuation-in-part application of application Ser. No. 10/760,697 filed Jan. 19, 2004 which is a divisional application of application Ser. No. 09/634,615, filed Aug. 5, 2000, now U.S. Pat. No. 6,680,214, which claims the benefit of U.S. Provisional Application No. 60/149,805, filed on Aug. 18, 1999, and is a continuation application of application Ser. No. 09/093,652, filed Jun. 8, 1998, now abandoned, and is related to application Ser. No. 09/020,654, filed Feb. 9, 1998, now U.S. Pat. No. 6,281,514. The above-mentioned patent applications are assigned to the assignee of the present application and are herein incorporated in their entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to methods for altering the distribution of quantum states within a volume limited by a potential energy barrier and for promoting the transfer of elementary particles across a potential energy barrier.  
         [0003]     U.S. Pat. No. 6,281,514, U.S. Pat. No. 6,117,344, U.S. Pat. No. 6,531,703 and U.S. Pat. No. 6,495,843 disclose a method for promoting the passage of elementary particles through a potential barrier comprising providing a potential barrier having a geometrical shape for causing de Broglie interference between said elementary particles. Also disclosed is an elementary particle-emitting surface having a series of indents. The depth of the indents is chosen so that the probability wave of the elementary particle reflected from the bottom of the indent interferes destructively with the probability wave of the elementary particle reflected from the surface. This results in the increase of tunneling through the potential barrier. When the elementary particle is an electron, then electrons tunnel through the potential barrier, thereby leading to a reduction in the effective work function of the material.  
         [0004]     WO03083177 discloses modification of a metal surface with patterned indents to increase the Fermi energy level inside the metal, leading to a decrease in electron work function. Also disclosed is a method for making nanostructured surfaces having perpendicular features with sharp edges.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In broad terms, this invention is a new class of materials having altered properties. In particular, it relates to materials having a surface structure causing electron wave interference resulting in a change in the way electron energy levels within the materials are distributed. The materials of the present invention have at least one surface having at least one indent or protrusion to cause electron wave interference within the material.  
         [0006]     In a first embodiment the materials of the invention take the form of a substrate surface having at least one indent or protrusion to cause electron wave interference within the substrate. The substrate may be a metal or non-metal.  
         [0007]     In a second embodiment the materials of the invention take the form of a thin layer of a substance on a substrate surface having at least one indent or protrusion to cause electron wave interference within the substance. The substance may be a metal or non-metal 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0008]     For a more complete explanation of the present invention and the technical advantages thereof, reference is now made to the following description and the accompanying drawing in which:  
         [0009]      FIG. 1  shows a material of the present invention in the form of a substrate surface; and  
         [0010]      FIG. 2  shows a material of the present invention in the form of a thin layer of a substance on a substrate surface. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     Embodiments of the present invention and their technical advantages may be better understood by referring to  FIG. 1  which shows a substrate  104 . The substrate has an indent  106  on one surface. Whilst the structure shown in  FIG. 1  is a single indented region, this should not be considered to limit the scope of the invention, and dotted lines have been drawn to indicate that in further embodiments the structure shown may be extended in one or both directions (i.e. to the left and/or to the right) to form features on the surface of the substrate that have a repeating, or periodic, nature.  
         [0012]     The configuration of the surface may resemble a corrugated pattern of squared-off, “u”-shaped ridges and/or valleys. Alternatively, the pattern may be a regular pattern of rectangular “plateaus” or “holes,” where the pattern resembles a checkerboard. The walls of said indents should be substantially perpendicular to one another, and the edges of the indents should be substantially sharp. Further, one of ordinary skill in the art will recognize that other configurations are possible that may produce the desired interference of wave functions. The surface configuration may be achieved using conventional approaches known in the art, including without limitation lithography and e-beam milling.  
         [0013]     Substrate  104  is comprised of any material that can have its surface modified to form the indented structure illustrated in  FIG. 1 . Preferably the material is one that, under stable conditions, will not form an oxide layer, or will form an oxide layer of a known and reliable thickness. In any case, the thickness of an oxide layer formed on the material should be much less than the depth of the indent. Preferred materials include, but are not restricted to, metals such as gold and chrome, and materials that under stable conditions form an oxide layer preferably of less than about ten nanometers, and more preferably of less than about five nanometers. Other preferred materials include non-metals such as silica and silicon. In a preferred embodiment the material is substantially homogenous and has no internal atomic or molecular structure likely to interfere with electron De Broglie waves, and most preferably is monocrystalline or amorphous.  
         [0014]     Indent  106  has a width  108  and a depth  112  and the separation between the indents is  110 . Preferably distances  108  and  110  are substantially equal. Preferably distance  108  is of the order of 1 μm or less. Experimental observations using a Kelvin probe indicate that the magnitude of a reduction in an apparent work function increases as distance  112  is reduced. Utilization of e-beam lithography to create structures of the kind shown in  FIG. 1  may allow indents to be formed in which distance  108  is 100 nm or less. Distance  112  is of the order of 10 nm or less, and is preferably of the order of 5 nm.  
         [0015]     Referring now to  FIG. 2 , substrate  204  is the modified insulator substrate having geometry described above and shown in  FIG. 1 . Thin film  202  is formed on the indented surface as shown in  FIG. 2 . Thin film  202  may be deposited onto the surface of substrate  204  by any conventional means of deposition. Preferably film  202  is formed on substrate  204  by a process that does not lead to the formation of any internal atomic or molecular structure likely to interfere with electron waves, and most preferably film  202  is monocrystalline or amorphous. Film  202  is sufficiently thin that the structure of the substrate is maintained on the surface of the film. Thus distances  208 ,  210 , and  212  are substantially similar to distances  108 ,  110 , and  112 . Distance  214  is typically of the order of  100  nm, and is preferably comparable to the ballistic range of an electron inside material  202 . Film  202  is comprised of any material that can be formed on substrate  204  as illustrated in  FIG. 2 . Preferably the material is one that, under stable conditions, will not form an oxide layer, or will form an oxide layer of a known and reliable thickness. Preferred materials include, but are not restricted to, metals such as gold and chrome, and materials that under stable conditions form an oxide layer preferably of less than about ten nanometers, and more preferably of less than about five nanometers. Preliminary measurements show that using gold as the material may allow the apparent work function to be reduced to as little as 0.6 eV. Using calcium may allow a substantially greater reduction of work function. Other preferred materials include non-metals.