Efficient Thermoelectric Device and Associated Method

Abstract

A high efficiency thermo electric device and associated method of making, the device comprising a multilayer structure of alternating insulator and insulator/metal material that is irradiated across the plane of the layer structure with ionizing radiation. The ionizing radiation produces nanoclusters of the metal material in the layered structure that increase the electrical conductivity and decrease the thermal conductivity thereby increasing the thermoelectric figure of merit. Figures of merit as high as 2.5 have been achieved using layers of co-deposited gold and silicon dioxide interspersed with layers of silicon dioxide. The gold to silicon dioxide ratio was 0.04. 5 MeV silicon ions were used to irradiate the structure. Other metals and insulators may be substituted. Other ionizing radiation sources may be used. The structure tolerates a wide range of metal to insulator ratio.

1 . A method for making a thermoelectric device comprising:
 1) generating a periodic multilayer structure comprising the steps of repetitively,
 a) depositing a first layer comprising a first electrical insulating material, and 
 b) depositing a single composite layer comprising a co-deposited metal with a second electrical insulating material; and 
   2) irradiating said periodic multilayer structure with ionizing radiation to increase a thermoelectric figure of merit, said ionizing radiation having sufficient energy to produce nanoclusters of said metal within said single composite layer.   
   
   
       2 . The method of  claim 1 , further including the steps of:
 applying a first electrically conductive layer to a first side of said periodic multilayer structure for a first electrical connection to said periodic multilayer structure; and   applying a second electrically conductive layer to a side of said periodic multilayer structure opposite said first side of said periodic multilayer structure for a second electrical connection to said periodic multilayer structure.   
   
   
       3 . The method of  claim 2 , wherein the step of applying said first electrically conductive layer comprises depositing, painting, coating, or contacting said first electrically conductive layer to said first side of said periodic multilayer structure. 
   
   
       4 . The method of  claim 2 , further including the steps of:
 applying a temperature difference between said first electrically conductive layer and said second electrically conductive layer; and   connecting an electrical load between said first electrically conductive layer and said second electrically conductive layer to receive electrical energy produced as a result of said temperature difference.   
   
   
       5 . The method of  claim 2 , further including the steps of:
 connecting an electrical power source to said first electrically conductive layer and said second electrically conductive layer; and   utilizing a temperature difference between said first electrically conductive layer and said second electrically conductive layer resulting from thermal transport through said periodic multiple layer structure due to electrical power delivered from said electrical power source.   
   
   
       6 . The method of  claim 1 , wherein a thickness of the first insulating layer is less than three nanometers. 
   
   
       7 . The method of  claim 1 , wherein a thickness of the composite layer is less than twenty nanometers. 
   
   
       8 . The method of  claim 1 , wherein a thickness of the composite layer is less than one hundred nanometers. 
   
   
       9 . The method of  claim 1 , wherein the ionizing radiation comprises x-rays, gamma rays, electrons, protons, or ions. 
   
   
       10 . The method of  claim 9 , wherein the ionizing radiation comprises ions with initial energy greater than 3 MeV. 
   
   
       11 . The method of  claim 10 , wherein the ion initial energy is selected such that ion stopping power decreases through subsequent periods of the periodic multilayer structure. 
   
   
       12 . The method of  claim 10 , wherein the fluence is greater than 10 13  ions per square centimeter. 
   
   
       13 . The method of  claim 1 , wherein the first electrical insulating material and second electrical insulating material are the same material. 
   
   
       14 . The method of  claim 1 , wherein the ionizing radiation penetrates all layers of the periodic multilayer structure. 
   
   
       15 . The method of  claim 14 , wherein the number of periods in the periodic multilayer structure is greater than 40. 
   
   
       16 . The method of  claim 1 , wherein the first electrical insulating material is SiO 2 . 
   
   
       17 . The method of  claim 1 , wherein the first electrical insulating material is silicon monoxide, silicon nitride, aluminum oxides, vanadium oxides, magnesium fluoride, zinc sulphide, titanium dioxide, or calcium fluoride. 
   
   
       18 . The method of  claim 1 , wherein the metal material co-deposited with said second electrical insulating material is gold. 
   
   
       19 . The method of  claim 1 , wherein the metal material co-deposited with said second electrical insulating material is silver, copper, platinum, or aluminum. 
   
   
       20 . The method of  claim 1 , wherein the ionizing radiation is directed at a direction having a normal component to a plane of said periodic multilayer structure. 
   
   
       21 . The method of  claim 1 , wherein the step of depositing said single composite layer utilizes a molecular beam epitaxy deposition process. 
   
   
       22 . The method of  claim 1 , wherein the step of depositing said single composite layer utilizes an ion beam assisted deposition process. 
   
   
       23 . The method of  claim 1 , wherein said ionizing radiation forms a linear arrangement of nanoclusters along a track of said ionizing radiation. 
   
   
       24 . The method of  claim 1 , wherein the periodic multilayer structure has a gradient in nanocluster size as a function of distance through the thickness of the periodic multilayer structure. 
   
   
       25 . The method of  claim 24 , wherein the gradient in nanocluster size is produced by setting an initial energy of said ionizing radiation to produce a gradient in stopping power as the radiation progresses through the multilayer structure. 
   
   
       26 . The method of  claim 24 , wherein the gradient in nanocluster size is produced by varying a metal fraction with successive layers of the periodic multilayer structure. 
   
   
       27 . The method of  claim 24 , wherein the gradient in nanocluster size is produced by varying a thickness of said composite layer or a thickness of said first insulating layer with successive layers of said periodic multilayer structure.