Two Terminal Re Writeable Non Volatile Ion Transport Memory Device

Abstract

A memory using mixed valence conductive oxides is disclosed. The memory includes a mixed valence conductive oxide that is less conductive in its oxygen deficient state and a mixed electronic ionic conductor that is an electrolyte to oxygen and promotes an electric field effective to cause oxygen ionic motion.

1 . A memory device, comprising:
 a re-writeable non-volatile memory element (ME) having exactly two-terminals and including electrically in series with the two terminals
 a tunnel barrier having a first conductivity, 
 an ion reservoir including mobile oxygen ions and having a second conductivity that is higher than the first conductivity, the ion reservoir and the tunnel barrier are in contact with each other and are electrically in series with each other. 
   
     
     
         2 . The memory device of  claim 1 , wherein the ion reservoir includes a substantially crystalline structure. 
     
     
         3 . The memory device of  claim 2 , wherein the ion reservoir retains the substantially crystalline structure when the ion reservoir is in an oxygen deficient state. 
     
     
         4 . The memory device of  claim 2 , wherein the ion reservoir retains the substantially crystalline structure when a write voltage or a read voltage is applied across the two terminals of the ME. 
     
     
         5 . The memory device of  claim 1 , wherein less than an entire portion of the ion reservoir is placed in an oxygen deficient state by a write operation on the ME. 
     
     
         6 . The memory device of  claim 1 , wherein strata of the ion reservoir positioned closer to the tunnel barrier are placed in a more oxygen deficient state after a write operation on the ME than strata in the ion reservoir that are positioned further away from the tunnel barrier. 
     
     
         7 . The memory device of  claim 1 , wherein strata of the ion reservoir positioned closer to the tunnel barrier exhibit a larger change in valence state after a write operation on the ME than strata in the ion reservoir that are further away from the tunnel barrier. 
     
     
         8 . The memory device of  claim 1 , wherein a conductivity of the ME is indicative of a resistive state and the resistive state can be non-destructively determined by applying a read voltage across the two terminals of the ME. 
     
     
         9 . The memory device of  claim 1 , wherein a conductivity of the ME is indicative of a resistive state and the resistive state can be reversibly written to different values by applying write voltage across the two terminals of the ME. 
     
     
         10 . The memory device of  claim 1 , wherein application of a write voltage across the two terminals of the ME is operative to transport at least a portion of the mobile oxygen ions between the ion reservoir and the tunnel barrier. 
     
     
         11 . The memory device of  claim 1 , wherein the ME is configured to store at least one bit of non-volatile data and the data is retained in the absence of electrical power. 
     
     
         12 . The memory device of  claim 1 , wherein the ion reservoir includes a polycrystalline structure. 
     
     
         13 . The memory device of  claim 1 , wherein the tunnel barrier has a thickness of less than approximately 50 angstroms. 
     
     
         14 . The memory device of  claim 1 , wherein the tunnel barrier is made from a material that is an electrolyte to the mobile oxygen ions. 
     
     
         15 . The memory device of  claim 1 , wherein the tunnel barrier is permeable to the mobile oxygen ions only when a write voltage is being applied across the two terminals of the ME, and transport of a portion of the mobile oxygen ions into or our out of the tunnel barrier occurs only when the write voltage is being applied. 
     
     
         16 . A memory device, comprising:
 a re-writeable non-volatile memory element (ME) having exactly two-terminals and including electrically in series with the two terminals
 a tunnel barrier having a first conductivity, the tunnel barrier having a tunnel barrier width, a tunnel barrier height, or both, 
 an ion reservoir including mobile oxygen ions and having a second conductivity that is higher than the first conductivity, 
 the ion reservoir and the tunnel barrier are in contact with each other and are electrically in series with each other, 
 the ion reservoir including a low conductivity region positioned adjacent to the tunnel barrier and responsive to a write voltage applied across the two terminals of the ME, and 
 the low conductivity region operative to form an effective tunnel barrier width that is greater than the tunnel barrier width of the tunnel barrier. 
   
     
     
         17 . The memory device, of  claim 16 , wherein a conductivity of the ME is indicative of a resistive state and the resistive state can be non-destructively determined by applying a read voltage across the two terminals of the ME. 
     
     
         18 . The memory device of  claim 16 , wherein applying a write voltage across the two terminals of the ME is operative to transport at least a portion of the mobile oxygen ions between the ion reservoir and the tunnel barrier. 
     
     
         19 . The memory device of  claim 16 , wherein a first write voltage applied across the two terminals of the ME is operative to transport a first portion of the mobile oxygen ions from the ion reservoir into the tunnel barrier, and a second write voltage applied across the two terminals of the ME is operative to transport the first portion the mobile oxygen ions from the tunnel barrier into the ion reservoir, and wherein the second write voltage has a polarity opposite that of the first write voltage. 
     
     
         20 . The memory device of  claim 16 , wherein the ion reservoir includes a structure selected from the group consisting of a substantially crystalline structure and a polycrystalline structure. 
     
     
         21 . The memory device of  claim 16 , wherein the ion reservoir includes a substantially crystalline structure and retains the substantially crystalline structure when a write voltage or a read voltage is applied across the two terminals of the ME. 
     
     
         22 . The memory device of  claim 16 , wherein forming does not significantly contribute to an overall conductivity of the ME, whereby forming comprises localized filamentary movement of an anode material within the ion reservoir. 
     
     
         23 . A two terminal electrical device, comprising:
 a re-writeable non-volatile memory element (ME) having exactly two terminals and including electrically in series with the two terminals
 a tunnel barrier, 
 an ion reservoir including mobile oxygen ions, the ion reservoir in contact with and electrically in series with the tunnel barrier, 
 the tunnel barrier made from a material that is an electrolyte to the mobile oxygen ions and is permeable by at least a portion of the mobile oxygen ions only when a write voltage is applied across the two terminals of the ME, and 
 the ME has a first conductivity at a read voltage applied across the two terminals and a second conductivity at the read voltage after a write voltage has been applied across the two terminals. 
   
     
     
         24 . The two terminal electrical device of  claim 23 , wherein a conductivity of the ME is indicative of a resistive state and the resistive state can be non-destructively determined by applying the read voltage across the two terminals of the ME. 
     
     
         25 . The two terminal electrical device of  claim 23 , wherein application of the write voltage causes mobile oxygen ion transport between the ion reservoir and the tunnel barrier. 
     
     
         26 . The two terminal electrical device of  claim 23 , wherein the ion reservoir includes a structure selected from the group consisting of a substantially crystalline structure and a polycrystalline structure. 
     
     
         27 . The two terminal electrical device of  claim 23 , wherein the ion reservoir includes a substantially crystalline structure and retains the substantially crystalline structure when the write voltage or the read voltage is applied across the two terminals of the ME. 
     
     
         29 . The two terminal electrical device of  claim 23 , wherein forming does not significantly contribute to an overall conductivity of the ME, whereby forming comprises localized filamentary movement of an anode material within the ion reservoir. 
     
     
         30 . An electrical device having exactly two terminals, comprising:
 a tunnel barrier having a thickness of less than approximately 50 angstroms, the thickness configured for electron tunneling during both reading and writing; and   an ion reservoir including mobile oxygen ions, the ion reservoir in contact with the tunnel barrier, the tunnel barrier is made from a material that is an electrolyte to the mobile oxygen ions and is permeable to the mobile oxygen ions only during the writing, and   wherein the ion reservoir electrically in series with the tunnel barrier has a first conductivity at a read voltage and a second conductivity at the read voltage after applying a write voltage.   
     
     
         31 . The electrical device of  claim 30 , wherein a conductivity of the ion reservoir electrically in series with the tunnel barrier is indicative of a resistive state and the resistive state can be non-destructively determined during the reading. 
     
     
         32 . The electrical device of  claim 30 , wherein the writing causes mobile oxygen ion transport between the ion reservoir and the tunnel barrier. 
     
     
         33 . The two terminal electrical device of  claim 30 , wherein the ion reservoir includes a structure selected from the group consisting of a substantially crystalline structure and a polycrystalline structure. 
     
     
         34 . The two terminal electrical device of  claim 30 , wherein the ion reservoir includes a substantially crystalline structure and retains the substantially crystalline structure during the reading and the writing. 
     
     
         35 . The two terminal electrical device of  claim 30 , wherein forming does not significantly contribute to an overall conductivity of the ion reservoir electrically in series with the tunnel barrier, whereby forming comprises localized filamentary movement of an anode material within the ion reservoir.