Phase transition devices and smart capacitive devices

Abstract

Phase transition devices may include a functional layer made of functional material that can undergo a change in conductance in response to an external stimulus such as an electric or magnetic or optical field, or heat. The functional material transitions between a conducting state and a non-conducting state, upon application of the external stimulus. A capacitive device may include a functional layer between a top electrode and a bottom electrode, and a dielectric layer between the functional layer and the top electrode. A three terminal phase transition switch may include a functional layer, for example a conductive oxide channel, deposited between a source and a drain, and a gate dielectric layer and a gate electrode deposited on the functional layer. An array of phase transition switches and/or capacitive devices may be formed on a substrate, which may be made of inexpensive flexible material.

1 . A device comprising:
 a substrate;   a first contact disposed on the substrate;   a second contact disposed on the substrate; and   a layer of a functional material deposited on the substrate;   wherein the functional material is adapted to undergo a conductance transition between a conducting state and a non-conducting state, upon application of an external stimulus to the functional material.   
     
     
         2 . The device of  claim 1 , wherein the functional material comprises one of:
 vanadium oxide; titanate; and doped titanate.   
     
     
         3 . The device of  claim 2 , wherein the first contact and the second contact comprises one of:
 a metallic contact; a magnetic contact; an oxide conductor; and a magnetic oxide.   
     
     
         4 . The device of  claim 1 , further comprising an insulating layer between the substrate and the layer of the functional material. 
     
     
         5 . The device of  claim 1 , wherein the external stimulus comprises at least one of:
 a temperature change; a magnetic field; an electric field; and light.   
     
     
         6 . The device of  claim 1 , wherein the substrate comprises a semiconductor material, and wherein the semiconductor material comprises one of:
 single crystal silicon; polycrystal silicon; InAs; Ge; InP; ZnO; a group III-V semiconductor; a group II-VI semiconductor; a group IV semiconductor; and an organic semiconductor.   
     
     
         7 . The device of  claim 1 , wherein the substrate comprises a flexible material, and wherein the flexible material comprises one of: a plastic material; a polymer; and a polyimide. 
     
     
         8 . A phase transition switch comprising:
 a substrate;   a source and a drain disposed on the substrate;   a conductive oxide channel deposited on the substrate between the source and the drain;   a layer of gate dielectric material deposited on the oxide channel; and   a gate electrode disposed on the gate dielectric layer;   wherein the oxide channel includes a functional material whose conductance is adapted to be modulated upon application of an external stimulus to the oxide channel.   
     
     
         9 . The switch of  claim 8 , wherein the external stimulus comprises at least one of: an electric field; a magnetic field; an optical field; and heat. 
     
     
         10 . The switch of  claim 8 , wherein the oxide channel, upon conductance modulation, is adapted to cause a current flowing through the device to be controlled, so that the current is transmitted through the device when the oxide channel is in a conducting state, and flow of the current through the device is impeded when the oxide channel is in a non-conducting state. 
     
     
         11 . The switch of  claim 8 , wherein the gate dielectric material comprises: an insulator; and a ferroelectric oxide. 
     
     
         12 . The switch of  claim 8 , wherein the source and the drain comprises one of: a highly doped semiconductor; and a metal. 
     
     
         13 . The switch of  claim 8 , further comprising a controller configured to control current flow across the device by controlling the external stimulus and the transition of the functional material between the conducting state and the non-conducting state. 
     
     
         14 . A device comprising:
 a substrate;   a first electrode layer disposed on the substrate; and   a functional layer disposed on the first electrode layer, the functional layer including a functional material having a resistance that can be modulated in response to an external stimulus; and   a second electrode layer disposed over the functional layer.   
     
     
         15 . The device of  claim 14 , wherein in response to the external stimulus, the functional material is configured to transition between a conducting state in which the functional material transmits electricity, and a non-conducting state in which the functional material stores charge; and wherein the functional layer when in the conducting state is configured to permit flow of a current in a direction substantially perpendicular to the plane of the substrate. 
     
     
         16 . The device of  claim 14 , wherein the functional material comprises one of vanadium oxide and vanadium dioxide, and wherein in response to the external stimulus, the functional material is configured to transition between a conducting state and a non-conducting state, with a change in resistance of at least four orders of magnitude. 
     
     
         17 . The device of  claim 15 , wherein the functional layer when in the non-conducting state causes storage of charge, and when in the conducting state causes a discharge of stored charge, so that the conducting and non-conducting state of the functional layer can be used as a memory bit. 
     
     
         18 . The device of  claim 14 , further comprising an oxide dielectric layer deposited between the functional layer and the second electrode layer to provide a capacitance; wherein the functional layer when in the non-conducting state adds to the capacitance of the oxide dielectric layer, and the functional layer when in the conducting state does not contribute any capacitance so that the capacitance of the memory device results only from the oxide dielectric layer. 
     
     
         19 . The device of  claim 14 , wherein the functional material comprises a functional oxide, and wherein the functional oxide comprises one of:
 vanadium oxide;   titanium oxide; and   a doped multi-component oxide.   
     
     
         20 . An array of interconnected devices, wherein each one of the devices includes a functional material adapted to undergo a conductance transition between a conducting state and a non-conducting state upon application of an external stimulus thereto. 
     
     
         21 . The array of  claim 20 , wherein at least one of the devices is a phase transition switch comprising:
 a functional layer deposited between a source and a drain, the functional layer including a functional material;   a gate disposed over the functional layer and between the source and the drain;   
       wherein the conductance of the functional material is adapted to be modulated upon application of an external stimulus to the gate. 
     
     
         22 . The array of  claim 20 , wherein at least one of the devices is a capacitive device comprising:
 a functional layer deposited on a bottom electrode;   a layer of a dielectric deposited on the functional layer;   a top electrode disposed on the layer of the dielectric;   
       wherein the functional layer includes a functional material having a resistance that can be modulated in response to an external stimulus. 
     
     
         23 . A method of controlling flow of a current through a system, the method comprising:
 connecting a phase transition device to the system, wherein the phase transition device includes a layer of a functional material deposited on a substrate;   applying one or more external stimuli onto the layer of functional material in the phase transition device, so as to cause the functional material to undergo a conductance transition between a non-conducting state in which the functional material transmits electricity and allows the current to flow through the system, and a non-conducting state in which the functional material does not transmit electricity and blocks the flow of the current through the system.   
     
     
         24 . A method of fabricating a device, comprising:
 depositing a layer of a functional material onto a substrate; and   depositing an electrode onto the layer of functional material;   wherein the material is adapted to undergo a conductance transition between a conducting state and a non-conducting state, upon application of an external stimulus to the material.   
     
     
         25 . The method of  claim 24 , wherein the act of depositing the layer of the material onto the substrate comprises at least one of:
 performing an atomic layer deposition;   performing a physical vapor deposition; and   performing a chemical vapor deposition.   
     
     
         26 . The method of  claim 25 , wherein the physical vapor deposition comprises at least one of:
 sputtering; evaporation; and molecular beam synthesis.