Galvanic porous silocon composites for nanoenergetics and monolithically integrated ignitor

Abstract

Porous silicon (PS) films composed of pores with diameters less than 3 nm are fabricated using a galvanic etching approach that does not require an external power supply. A highly reactive, nanoenergetic composite is then created by impregnating the nanoscale pores with the strong oxidizer, sodium perchlorate (NaClO 4 ). The combustion propagation velocity of the energetic composite is measured using microfabricated diagnostic devices in conjunction with high-speed optical imaging up to 930,000 frames per second. Combustion velocities averaging 3,050 m/s are observed for PS films with specific areas of ˜840 m 2 /g and porosities of about 65-67%. Galvanic etching may also be used to fabricate other porous silicon morphologies and also strong oxidizers other than NaClO 4 could be used to create a nanoenergetic porous silicon composite.

What is claimed is: 
     
         1 . A method of making a nanoenergetic device with an integrated ignitor based on porous silicon formed by a galvanic cell comprising the steps of:
 coating a silicon wafer with low pressure LPCVD Si 3 N 4 ;   using standard microfabrication to remove a region of Si 3 N 4  on the silicon wafer to expose Si where either PS will be generated or a platinum cathode will be deposited;   depositing noble metal on side of wafer where Si 3 N 4  has been removed;   using galvanic etching to create a strip of PS having nanoscale pores;   depositing on said strip of PS an ignitor wire made up of a chrome/platinum/noble metal stack;   impregnating said strip of PS with a strong oxidizer; and   applying a voltage across said ignitor wire to heat the ignitor and ignite the PS.   
     
     
         2 . The method of  claim 1 , wherein a series of additional monitor wires are deposited on the strip of PS. 
     
     
         3 . The method of  claim 1 , wherein the combustion process is monitored by a high speed oscilloscope or video. 
     
     
         4 . The method of  claim 1 , wherein the galvanic etching step uses an electrolyte composition of HF in water and ethanol. 
     
     
         5 . The method of  claim 4 , wherein the electrolyte composition is HF in water and ethanol. 
     
     
         6 . The method of  claim 4 , wherein the galvanic etching step uses a solution of H 2 O 2  in water. 
     
     
         7 . The method of  claim 1 , wherein the strong oxidizer is NaClO 4 . 
     
     
         8 . The method of  claim 1 , wherein the noble metal is gold. 
     
     
         9 . The method of  claim 1 , wherein the method is a batch process. 
     
     
         10 . A nanoenergetic device with an integrated ignitor made up of a chrome/platinum/noble metal stack on PS formed by a galvanic cell. 
     
     
         11 . A nanoenergetic device of  claim 10 , which also contains a series of monitor wires made up of a chrome/platinum/noble metal stack on PS formed by a galvanic cell. 
     
     
         12 . A nanoenergetic device of  claim 11 , wherein the noble metal is gold.