Gold-semiconductor phase change memory for archival data storage

Abstract

A structure for storing digital data is provided, with a high reflectance layer comprising a gold film formed over a semiconductor layer, and a plurality of low reflectance portions comprising a mixture of a gold material and a semiconductor material. The plurality of low reflectance portions have top surfaces comprising more semiconductor material than the gold material. The invention also provides a method of changing reflectance on a data storage disk, comprising irradiating a laser light beam onto a gold film formed over a semiconductor layer, and raising the temperature of the gold film above a eutectic temperature for a mixture of gold and the semiconductor layer.

1 . A data storage medium comprising: 
 a first material layer; and    a second light reflective material layer formed over said first material layer and having a first light reflectance property, said first and second material layers having a property that a light beam applied to a region of said second material layer heats said first and second material layers at said region to cause a mixture of materials from said first and second material layers and a second light reflectance property for said region which is different from said first light reflectance property.    
   
   
       2 . The data storage medium of  claim 1 , wherein said second light reflective material layer is a gold containing film formed to a thickness of about 50 Å to about 300 Å.  
   
   
       3 . The data storage medium of  claim 1 , wherein said first material layer is a semiconductor layer formed to a thickness of about 200 Å to about 2000 Å.  
   
   
       4 . The data storage medium of  claim 1 , wherein said first light reflectance property is higher than said second light reflectance property.  
   
   
       5 . The data storage medium of  claim 1 , further comprising a dielectric layer under said first material layer.  
   
   
       6 . The data storage medium of  claim 1 , further comprising a protective layer over said second light reflective material layer.  
   
   
       7 . The data storage medium of  claim 6 , wherein said protective layer comprises a silicon dioxide layer formed to a thickness of about 300 Å to about 1000 Å.  
   
   
       8 . The data storage medium of  claim 1 , further comprising a substrate over said second light reflective material layer.  
   
   
       9 . The data storage medium of  claim 1 , wherein said first material layer comprises a silicon layer.  
   
   
       10 . The data storage medium of  claim 1 , wherein said first material layer comprises a silicon material and said second light reflective material layer comprises a gold material, and said mixture of materials comprises more of said silicon material than said gold material.  
   
   
       11 . The data storage medium of  claim 1 , wherein said first material layer comprises a germanium layer.  
   
   
       12 . The data storage medium of  claim 1 , wherein said first material layer comprises a germanium material and said second light reflective material layer comprises a gold material, and said mixture of materials comprises more of said germanium material than said gold material.  
   
   
       13 . The data storage medium of  claim 1 , wherein said mixture of materials is in a meta-stable phase.  
   
   
       14 . The data storage medium of  claim 1 , wherein said medium is a disk.  
   
   
       15 . A data storage medium comprising: 
 a first dielectric layer;    a semiconductor layer formed over said first dielectric layer;    a gold containing film formed over said semiconductor layer; and    a mixed material portion in said gold containing film and said semiconductor layer, said mixed material portion comprising a mixture of gold material and semiconductor material.    
   
   
       16 . The data storage medium of  claim 15 , wherein said gold containing film is formed to a thickness of about 50 Å to about 300 Å.  
   
   
       17 . The data storage medium of  claim 15 , wherein said semiconductor layer is formed to a thickness of about 200 Å to about 2000 Å.  
   
   
       18 . The data storage medium of  claim 15 , wherein said mixed material portion has a first reflectance value and said gold containing film has a second reflectance value higher than said first reflectance value.  
   
   
       19 . The data storage medium of  claim 15 , wherein said first dielectric layer has a first thermal conductivity and said semiconductor layer has a second thermal conductivity higher than said first thermal conductivity.  
   
   
       20 . The data storage medium of  claim 15 , wherein said first dielectric layer comprises a silicon dioxide layer.  
   
   
       21 . The data storage medium of  claim 15 , further comprising a second dielectric layer over said gold containing film.  
   
   
       22 . The data storage medium of  claim 21 , wherein said second dielectric layer comprises a silicon dioxide layer.  
   
   
       23 . The data storage medium of  claim 15 , further comprising a substrate over said gold containing film.  
   
   
       24 . The data storage medium of  claim 15 , wherein said semiconductor layer comprises a silicon layer.  
   
   
       25 . The data storage medium of  claim 15 , wherein said semiconductor material comprises a silicon material, and said mixed material portion comprises more of said silicon material than said gold material.  
   
   
       26 . The data storage medium of  claim 15 , wherein said semiconductor layer comprises a germanium layer.  
   
   
       27 . The data storage medium of  claim 15 , wherein said semiconductor material comprises a germanium material, and said mixed material portion comprises more of said germanium material than said gold material.  
   
   
       28 . The data storage medium of  claim 15 , wherein said mixed material portion is in a meta-stable phase.  
   
   
       29 . The data storage medium of  claim 15 , wherein said medium is a disk.  
   
   
       30 . A data storage medium, comprising: 
 a high reflectance layer comprising a gold film formed over a semiconductor layer; and    a plurality of low reflectance portions comprising a mixture of a gold material and a semiconductor material.    
   
   
       31 . The data storage medium according to  claim 30 , wherein said plurality of low reflectance portions have top surfaces comprising more semiconductor material than said gold material.  
   
   
       32 . The data storage medium according to  claim 30 , wherein said semiconductor material comprises a silicon material.  
   
   
       33 . The data storage medium according to  claim 30 , wherein said semiconductor material comprises a germanium material.  
   
   
       34 . The data storage medium according to  claim 30 , wherein said semiconductor layer is a silicon layer.  
   
   
       35 . The data storage medium according to  claim 30 , wherein said semiconductor layer is a germanium layer.  
   
   
       36 . The data storage medium according to  claim 30 , wherein said high reflectance layer is between about 50 Å to about 300 Å thick.  
   
   
       37 . The data storage medium according to  claim 30 , further comprising a dielectric layer underneath said semiconductor layer and another dielectric layer over said high reflectance layer.  
   
   
       38 . The data storage medium according to  claim 30 , further comprising a dielectric layer underneath said semiconductor layer and a substrate over said high reflectance layer.  
   
   
       39 . The data storage medium according to  claim 30 , wherein said medium is a disk.  
   
   
       40 . A data storage medium comprising: 
 a first dielectric layer;    a semiconductor layer formed over said first dielectric layer; and    a gold containing film formed over said semiconductor layer.    
   
   
       41 . The data storage medium of  claim 40 , wherein said gold containing film is formed to a thickness of about 50 Å to about 300 Å.  
   
   
       42 . The data storage medium of  claim 40 , wherein said semiconductor layer is formed to a thickness of about 200 Å to about 2000 Å.  
   
   
       43 . The data storage medium of  claim 40 , wherein said first dielectric layer has a first thermal conductivity and said semiconductor layer has a second thermal conductivity higher than said first thermal conductivity.  
   
   
       44 . The data storage medium of  claim 40 , wherein said first dielectric layer comprises a silicon dioxide layer formed to a thickness of about 300 Å to about 1000 Å.  
   
   
       45 . The data storage medium of  claim 40 , further comprising a second dielectric layer over said gold film.  
   
   
       46 . The data storage medium of  claim 45 , wherein said second dielectric layer comprises a silicon dioxide layer.  
   
   
       47 . The data storage medium of  claim 40 , further comprising a polycarbonate substrate over said gold film.  
   
   
       48 . The data storage medium of  claim 40 , wherein said semiconductor layer comprises a silicon layer.  
   
   
       49 . The data storage medium of  claim 40 , wherein said semiconductor layer comprises a germanium layer.  
   
   
       50 . The data storage medium of  claim 40 , wherein said medium is a disk.  
   
   
       51 . A system for writing data to a recording medium, comprising: 
 an optical recording medium comprising a first dielectric layer, a semiconductor layer formed over said first dielectric layer, and a gold containing film formed over said semiconductor layer; and    a device capable of irradiating a laser beam onto the medium, and producing regions in said medium containing a mixture of material from said gold containing film and said semiconductor layer.    
   
   
       52 . The system of  claim 51 , wherein said laser beam is capable of melting said gold layer and said semiconductor layer.  
   
   
       53 . The system of  claim 51 , wherein said laser beam is capable of reading written data from said medium.  
   
   
       54 . The system of  claim 51 , wherein said device is capable of detecting a difference in reflectance of said laser beam between said gold containing film and an area containing a mixture of said semiconductor layer and said gold containing film.  
   
   
       55 . The system of  claim 51 , wherein said medium is a disk.  
   
   
       56 . A method of writing data to a medium, comprising: 
 providing a disk having a dielectric layer, a semiconductor layer over said dielectric layer, and a gold film over said semiconductor layer having a predetermined reflectivity; and    irradiating a laser light beam onto said gold film with sufficient energy to diffuse said gold film into said semiconductor layer to create an area having a reflectivity lower than said predetermined reflectivity.    
   
   
       57 . The method of  claim 56 , wherein said semiconductor layer comprises a silicon semiconductor layer, and said act of irradiating said laser light beam comprises raising a temperature of said gold film and said silicon semiconductor layer above a eutectic temperature for a gold-silicon mixture.  
   
   
       58 . The method of  claim 56 , wherein said semiconductor layer comprises a germanium semiconductor layer, and said act of irradiating said laser light beam comprises raising a temperature of said gold film and said germanium semiconductor layer above a eutectic temperature for a gold-germanium mixture.  
   
   
       59 . The method of  claim 56 , wherein said gold film has a thickness of between about 50 Å to about 300 Å.  
   
   
       60 . The method of  claim 56 , wherein said semiconductor layer has a thickness of between about 200 Å to about 2000 Å.  
   
   
       61 . The method of  claim 56 , wherein said dielectric layer is a silicon dioxide layer having a thickness of between about 300 Å to about 1000 Å.  
   
   
       62 . The method of  claim 56 , wherein said act of irradiating said laser light beam comprises raising a temperature of said gold film to at least 400° C.  
   
   
       63 . The method of  claim 56 , wherein said act of irradiating said laser light beam comprises irradiating a light beam having a wavelength in the range of 405 nm and 480 nm.  
   
   
       64 . The method of  claim 56 , further comprising cooling said gold film and said semiconductor layer after said act of irradiating.  
   
   
       65 . The method of  claim 64 , wherein said act of cooling comprises cooling through dissipation of heat into material layers underneath said semiconductor layer.  
   
   
       66 . The method of  claim 65 , wherein said material layers underneath said semiconductor layer dissipate said heat such that a temperature of said gold film and said semiconductor layer is reduced to a temperature below a eutectic temperature in no longer than approximately 100 nanoseconds.  
   
   
       67 . The method of  claim 56  wherein said medium is a disk.  
   
   
       68 . The method of  claim 56  wherein said irradiating a laser light beam comprises irradiation a blue light laser beam.  
   
   
       69 . A method of changing reflectance on a data storage medium, comprising: 
 irradiating a laser light beam onto a gold film formed over a semiconductor layer to raise a temperature of said gold film above a eutectic temperature for a mixture of gold and said semiconductor layer, thereby creating a mixture of material from said gold film and material from said semiconductor layer; and    cooling said mixture;    whereby said irradiating and cooling acts to produce a top surface on said cooled mixture containing more of said material from said semiconductor layer than said material from said gold film.    
   
   
       70 . The method of  claim 69 , wherein said irradiating said laser light beam comprises irradiating a laser beam having a wave length in the range of approximately 405 nm to approximately 480 nm.  
   
   
       71 . The method of  claim 69 , wherein said semiconductor layer comprises a silicon layer.  
   
   
       72 . The method of  claim 69 , wherein said semiconductor layer comprises a germanium layer.  
   
   
       73 . The method of  claim 69 , wherein said data storage medium is a disk.  
   
   
       74 . The method of  claim 69 , wherein said irradiating a laser light beam comprises irradiating a blue laser light beam.