Superconducting magnesium diboride thin film and method and apparatus for fabricating the same

Abstract

A superconducting magnesium diboride (MgB 2 ) thin film having c-axial orientation and a method and apparatus for fabricating the same are provided. The fabrication method includes forming a boron thin film on a substrate and thermally processing the substrate on which the boron thin film is formed along with a magnesium source and cooling the resulting structure. The superconducting magnesium diboride thin film can be used in a variety of electronic devices employing superconducting thin films, such as precision medical diagnosis equipment using superconducting quantum interface devices (SQUIDs) capable of sensing weak magnetic fields, microwave communications equipment used for satellite communications, and Josephson devices. Computer systems with 100 times greater computing speed can be implemented with the superconducting magnesium diboride thin film.

What is claimed is:  
     
         1 . A method for forming a superconducting magnesium diboride (MgB 2 ) thin film, the method comprising: 
 (a) forming a boron thin film on a substrate; and    (b) thermally processing the substrate on which the boron thin film is formed along with a magnesium source and cooling the resulting structure.    
     
     
         2 . The method of  claim 1 , wherein, in step (a), the boron thin film is formed by pulsed laser deposition, sputtering deposition, electron beam evaporation, metallorganic chemical vapor deposition, or chemical vapor deposition.  
     
     
         3 . The method of  claim 1 , wherein, in step (b), the substrate with the boron thin film and the magnesium source are heated at a temperature of 600-1000° C. in the absence of air.  
     
     
         4 . The method of  claim 1 , wherein step (b) is carried out in a state where the substrate with the boron thin film and the magnesium source are double sealed with a container made of tantalum or niobium inside and a container made of quartz outside.  
     
     
         5 . The method of  claim 4 , wherein both ends of the container made of tantalum or niobium are sealed in an inert gas atmosphere, and both ends of the container made of quartz are sealed in a vacuum.  
     
     
         6 . The method of  claim 1 , wherein, in step (b), a temperature of a heat source is raised to 600-1000° C., and the substrate with the boron thin film and the magnesium source are placed inside the heat source, rapidly heated at the temperature of 600-1000° C. for 10-60 minutes, and cooled.  
     
     
         7 . The method of  claim 1 , wherein the substrate on which the boron thin film is formed is a monocrystalline sapphire substrate or a monocrystalline strontium titanate substrate.  
     
     
         8 . A superconducting magnesium diboride thin film formed by the method of  claim 1  with the c-axial crystal orientation.  
     
     
         9 . The superconducting magnesium diboride thin film of  claim 8 , wherein the boron thin film in step (a) is formed by pulsed laser deposition, sputtering deposition, electron beam evaporation, metallorganic chemical vapor deposition, or chemical vapor deposition.  
     
     
         10 . The superconducting magnesium diboride thin film of  claim 8 , wherein, in step (b), the substrate with the boron thin film and the magnesium source are heated at a temperature of 600-1000° C. in the absence of air.  
     
     
         11 . The superconducting magnesium diboride thin film of  claim 8 , wherein step (b) is carried out in a state where the substrate with the boron thin film and the magnesium source are double sealed with a container made of tantalum or niobium inside and a container made of quartz outside.  
     
     
         12 . The superconducting magnesium diboride thin film of  claim 11 , wherein both ends of the container made of tantalum or niobium are sealed in an inert gas atmosphere, and both ends of the container made of quartz are sealed in a vacuum.  
     
     
         13 . The superconducting magnesium diboride thin film of  claim 8 , wherein, in step (b), a temperature of a heat source is raised to 600-1000° C., and the substrate with the boron thin film and the magnesium source are placed inside the heat source, rapidly heated at the temperature of 600-1000° C. for 10-60 minutes, and cooled.  
     
     
         14 . The superconducting magnesium diboride thin film of  claim 8 , wherein the substrate on which the boron thin film is formed is a monocrystalline sapphire substrate or a monochrystalline strontium titanate substrate.  
     
     
         15 . An apparatus for fabricating a superconducting magnesium diboride thin film, the apparatus comprising: 
 a first protecting member receiving a substrate with a magnesium diboride thin film and a magnesium source for preventing the magnesium diboride thin film and the magnesium source from oxidizing in contact with the air;    a second protecting member receiving the first protecting member for preventing oxidization of the first protecting member; and    a heat source for thermally processing the substrate with the boron thin film and the magnesium source contained in the first protecting member and the second protecting member.    
     
     
         16 . The apparatus of  claim 15 , wherein the substrate with the boron thin film is a monocrystalline sapphire substrate or a monocrystalline strontium titanate substrate.  
     
     
         17 . The apparatus of  claim 15 , wherein the first protecting member is formed of tantalum or niobium and is filled with an inert gas.  
     
     
         18 . The apparatus of  claim 15 , wherein the second protecting member is formed of quartz and its inside is in a vacuum state.  
     
     
         19 . The apparatus of  claim 15 , wherein both ends of the first protecting member are sealed in an inert gas atmosphere, and both ends of the second protecting member are sealed in a vacuum.  
     
     
         20 . The apparatus of  claim 15 , wherein the heat source is a horizontal type electric furnace.