Temperature field control type conductivity change device

Abstract

To provide thermal field controlled electrical conductivity change devices and applications therefor.SOLUTION: In some embodiments, a thermal switch comprises: a metal-insulator-transition (MIT) material; first and second terminals electrically coupled to the MIT material; and a heater disposed near the MIT material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 809,434, entitled "THERMAL FIELD CONTROLLED ELECTRICAL CONDUCTIVITY CHANGE DEVICE", filed on February 22, 2019, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] This disclosure generally relates to computer technology, and more particularly, to switching elements for computer systems.

Background Art

[0003] Some materials exhibit two conductive states. In one state, the material has metallic conductive properties, and in the other state, the material has insulating conductive properties. Thus, this class of materials is called metal - insulator - transition (MIT) materials. These MIT materials are the subject of intensive research and development to find practical applications.

Summary of the Invention

[0004] Generally, one aspect disclosed features a thermal switch that includes an MIT material, a first terminal and a second terminal electrically coupled to the MIT material, and a heater disposed near the MIT material.

[0005] Embodiments of the thermal switch can include one or more of the following features. Some embodiments include an electrical insulator disposed between the MIT material and the heater. In some embodiments, the heater comprises a Joule heater. Some embodiments include third and fourth terminals electrically coupled to the heater, and the Joule heater generates heat when current is passed through the Joule heater and the third and fourth terminals. In some embodiments, the Joule heater comprises at least one constriction in a nanowire, or a nanopore in a nanowire. In some embodiments, the state of the MIT material can be sensed at the first and second terminals, and the state comprises a metallic state and an insulator state. In some embodiments, the state of the MIT material can be changed at the first and second terminals, and the state comprises a metallic state and an insulator state.

[0006] Generally, one aspect disclosed features a memory device comprising a memory and a memory selector electrically coupled to the memory, the memory selector comprising an MIT material and a heater disposed near the MIT material.

[0007] Embodiments of the memory device can include one or more of the following features. Some embodiments include an electrical insulator disposed between the MIT material and the heater. In some embodiments, the heater comprises a Joule heater. In some embodiments, the Joule heater comprises at least one constriction in a nanowire or a nanopore in a nanowire. Some embodiments include a first terminal and a second terminal electrically coupled to the heater, and the Joule heater generates heat when current is passed through the Joule heater and the first and second terminals. Some embodiments include a first terminal electrically coupled to the MIT material and a second terminal electrically coupled to the memory, and the state of the MIT material can be changed at the first and second terminals. The state of the MIT material comprises a metallic state and an insulator state, and the state of the memory can be changed and detected at the first and second terminals. Some embodiments include an electrical insulator disposed between the heater and the first terminal. Some embodiments include one or more electrical insulators disposed between the heater and at least one of the MIT material, the memory, the first terminal, or the second terminal.

[0008] Generally, one aspect disclosed features a cross-point memory array, the cross-point memory array being an array of memory elements arranged in rows and columns, each memory element comprising a memory and a memory selector electrically coupled to the memory, the memory selector comprising an MIT material and a Joule heater disposed near the MIT material. The cross-point memory array further comprises a plurality of first metal lines each electrically coupled to the memory of the memory elements within each column, and a plurality of second metal lines each electrically coupled to the memory of the memory elements within each row.

[0009] Embodiments of the cross-point memory array can include one or more of the following features. Some embodiments include a plurality of thermal isolators disposed between memory elements. In some embodiments, each of the memory elements further includes an electrical insulator disposed between a Joule heater and a respective second metal line. In some embodiments, each of the memory elements further includes one or more electrical insulators disposed between a Joule heater and at least one of an MIT material, a memory, a respective first metal line, or a respective second metal line. In some embodiments, each of the Joule heaters includes at least one constriction in a nanowire or a nanopore in a nanowire.

[0010] The accompanying drawings, which form a part of this disclosure, illustrate several non-limiting embodiments and, together with the description, serve to explain the principles disclosed.

Brief Description of the Drawings

[0011]

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Best Mode for Carrying Out the Invention

[0012] Next, refer in detail to the exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, where like or similar elements in different drawings are represented by the same number unless otherwise indicated. The implementations described in the following description of exemplary embodiments consistent with the present invention do not represent all implementations consistent with the present invention. Rather, they are merely examples of systems and methods consistent with aspects related to the present invention.

[0013] Thermal control is a current area of research and development in semiconductor devices and other devices. In some applications, it is desirable to operate different devices, and different parts of different devices, at different temperatures, even when the devices share a wafer or the like. The inventors have recognized that certain physical effects can be used to solve this problem.

[0014] FIG. 1 shows an assembly having a device with a device heater and a device cooler, according to one embodiment of the disclosed technology. Referring to FIG. 1, assembly 100 can include a circuit board, a wafer, or the like 102, as well as devices 104, 106, and 108. Devices 104, 106, and 108 can be implemented as any device, such as, for example, an integrated circuit, a transistor, a non-volatile memory device, other devices that can be included in an integrated circuit, and the like. In some embodiments, the non-volatile memory device can include a resistive random access memory device, a phase change memory device, a spin transfer torque magnetic random access memory device, and the like.

[0015] In the example of FIG. 1, devices 104, 106, and 108 can have different thermal requirements. In this example, it is desirable for device 106 to operate at ambient temperature, device 104 to operate at a temperature higher than ambient temperature, and device 108 to operate at a temperature lower than ambient temperature.

[0016] To control the operating temperature of each device without affecting the operating temperature of adjacent devices, a thermal control device can be implemented within each device. In the example of FIG. 1, device heater 110 can be implemented within device 104, and device cooler 112 can be implemented within device 108. In some embodiments, device heater 110 is implemented as a Joule heater. A Joule heater is a device that generates heat when current is passed through the device. In other embodiments, device heater 110 can be implemented using other physical effects. For example, other device heaters can use the Peltier effect, the photonic effect, plasmonic heat transfer, or any other effect that can transfer or deliver heat to device 104. Different heating effects can be used alone or in combination.

[0017] The device cooler 112 can be implemented in a complementary manner. For example, the device cooler can be implemented as a thermoelectric cooler based on the Peltier effect. In some embodiments, microfluidic pipes can be used to circulate a coolant through the device 112. Different cooling effects can be used alone or in combination.

[0018] The assembly 100 can include a thermal controller 114 to control the device heater 110 and the device cooler 112. The thermal controller 114 can be implemented as a processor or the like. In some embodiments, the thermal controller 114 can be implemented external to the assembly 100.

[0019] In some embodiments, the devices to be heated and cooled can include thermal sensors. In the example of FIG. 1, the device 110 to be heated can include a thermal sensor 116, and the device 112 to be cooled can include a thermal sensor 118. The thermal sensors 116, 118 can detect the temperatures of the devices 104, 108 and supply this information to the thermal controller 114. In some embodiments, the thermal sensors can be located at other locations within the assembly 100. In the example of FIG. 1, the thermal sensor 120 is located within the device 106, and the thermal sensor 122 is disposed on the wafer 102. The thermal controller 114 can use this information to control the device heater 110 and the device cooler 112.

[0020] In some embodiments, it may be desirable for different regions of a single device to operate at different temperatures. In such embodiments, a single device can include a device cooler and a device heater. Referring again to FIG. 1, the assembly 100 includes a device 128 that includes a device heater 130, a device cooler 132, and one or more thermal sensors 134. These elements can operate under the control of the thermal controller 114 as described above.

[0021] As described above, a class of materials called metal-insulator transition (MIT) materials have two conductive states, a metallic state and an insulator state. This transition can be controlled using an electric field. The electrical control of MIT material transitions has been investigated for use, for example, in selector applications in cross-point memory arrays. However, due to the nature of the electrically induced transitions, there is a trade-off between the threshold voltage and the leakage current, which makes the selector characteristics less than ideal for high-capacity memory device applications. Further, the coupling between electrical and thermal effects causes reliability degradation. The current overshoot after the selector turns on can cause an increase in the number of defects. That is, the defects generate heat, which generates more defects. Further, the current and voltage coupling between the selector and the memory device makes it difficult to design an accurate control circuit. For example, variations in the distribution of defects in the device cause large variations in the turn-on voltage between different devices.

[0022] For some MIT materials, the transition between the metallic state and the insulator state can be controlled using a temperature field. One such class of materials is vanadium oxide. FIG. 2 shows the metal-insulator transition for some vanadium oxides as a function of temperature. FIG. 3 shows the resistivity along the c-axis of some VO2 single crystals as a function of the reciprocal temperature. Among vanadium oxides, VO2 in particular exhibits a thermally driven metal-insulator transition at about 67° C. (340 K). As can be seen from FIGS. 2 and 3, the resistivity of vanadium oxide is reduced by several orders of magnitude (usually 10 3 ~10 5 orders of change) at the transition, along with changes in other properties including the crystal structure, light absorption, reflectivity, etc.

[0023] Another class of MIT materials that exhibit thermally controlled transitions is niobium oxide. FIG. 4 shows VO2 and NbO2 (and, for comparison, TaO which does not exhibit MIT) x) shows the low-field conductivity as a function of temperature. As can be seen from FIG. 4, NbO2 exhibits a thermally driven metal-insulator transition at about 807 °C (1080 K). Even below this temperature, NbO2 shows a resistivity change greater than six orders of magnitude from 300 K to 1000 K. FIG. 5 shows the electrical resistivity of some common MIT materials as a function of temperature.

[0024] The inventors recognized that this thermally driven metal-insulator transition can be utilized to implement a thermal switch, for example, for use in integrated circuits. According to various embodiments, the MIT material is combined with an on-chip heating element, such as a Joule heating element, to create a new type of thermal switch. Various embodiments of these switches exhibit a fast ramp-up time, for example, on the order of a few nanoseconds. Various embodiments also exhibit precise temperature control and low-power operation through localized heating.

[0025] Furthermore, many existing semiconductor devices, including transistors, memristors, phase change memories, and the like, exhibit different behaviors at different temperatures. The on-chip Joule heating element can be used not only to control the thermal switch but also to control the characteristics of these semiconductor devices. The disclosed thermal switches and on-chip heaters can be applied to a wide range of applications, including computing, memory, power management, photonic circuits, and the like.

[0026] Next, some thermal switches according to various embodiments are described. FIG. 6 shows a thermal switch according to one embodiment. Referring to FIG. 6, the thermal switch 600 includes an MIT material 602. The MIT material 602 can be any MIT material that exhibits a thermally driven conductivity change, or a combination of such materials. For example, the MIT material 602 can be fabricated from VO2, and NbO2, or a combination thereof. The switch terminals 608a, b are electrically coupled to both ends of the MIT material 602 such that a change in the conductivity of the MIT material 602 can be detected at those switch terminals 608.

[0027] The Joule heater 604 is disposed near the MIT material between two electrical terminals 610a, b. The Joule heater 604 can be fabricated from any material that experiences a temperature increase in response to the passage of an electric current through the material. The isolator 606 is disposed between the Joule heater 604 and the MIT material 602. The isolator 606 is fabricated from a material that acts as an electrical insulator between the Joule heater 604 and the MIT material 602 while allowing heat transfer from the Joule heater 604 to the MIT material 602. In some other embodiments, the isolator 606 is not essential and may be removed. When the terminals 610a, b are used to pass an electric current through the Joule heater 604, the temperature of the Joule heater 604 rises and heats the MIT material 602. When the temperature of the MIT material 602 reaches its transition temperature, the conductivity of the MIT material 602 changes. This change in conductivity can be detected at the terminals 608a, b. The terminals 608a, b can also be used to detect changes in other physical properties of the MIT material 602, such as reflectivity and the like.

[0028] FIG. 7 shows a thermal switch according to another embodiment. Referring to FIG. 7, the thermal switch 700 includes a pair of electrical terminals 708a, b and a Joule heater 704 encapsulated by an isolator 706 disposed near the MIT material 702. These elements can be fabricated as described above. In the thermal switch 700 of FIG. 7, in response to the passage of an electric current through the Joule heater 704 in a direction orthogonal to the plane of the drawing, the temperature of the Joule heater 704 rises and heats the MIT material 702. The direction of the electric current flowing through the Joule heater in the described embodiments can be arbitrary as long as the current heats the MIT material to its conductivity transition temperature. When the temperature of the MIT material 702 reaches its transition temperature, the conductivity of the MIT material 702 changes. This change in conductivity can be detected at the terminals 708a, b. The terminals 708a, b can also be used to detect changes in other physical properties of the MIT material 702, such as reflectivity and the like.

[0029] The disclosed thermal switch can be used to implement a cross-point memory array. Next, several such cross-point memory arrays are described. FIG. 8 shows a memory element for a cross-point memory array according to one embodiment. Referring to FIG. 8, the memory element 800 includes a memory 820 near the MIT material 802. The metal contact 808 is disposed near the memory 820. The metal line 810 is disposed near the MIT material 802. The Joule heater 804 is disposed within the metal line 810 and can be separated from the metal line 810 by adding an isolator 806. The isolator 806 is optional and not essential. When the isolator 806 is removed, the heater 804 and the metal line 810 can be combined by using the same single metal line. The memory 820 can be fabricated as a transistor, a memristor, a phase change memory, or the like. The remaining elements can be fabricated as described above.

[0030] During operation, the MIT material 802 acts as a selector for the memory 820 in response to the heat generated by the Joule heater 804. Specifically, changing the conductivity of the MIT material 802 using the Joule heater 804 can be used to sense or change the state of the memory 820. In this way, the disclosed thermal switch can be used to perform a memory selection operation on the memory array, for example, between read operations, write operations, and the like.

[0031] FIG. 9 shows a memory element for a cross-point memory array according to another embodiment. Referring to FIG. 9, the memory element 900 includes a memory 920 near an MIT material 902. A metal contact 908 is disposed near the memory 920. A metal line 910 is disposed near the MIT material 902. A Joule heater 904 surrounds the memory 920 and the MIT material 902, but is separated from those elements by an isolator 906a. The Joule heater 904 is separated from the metal line 910 by another isolator 906b. The elements of the memory element 900 can be fabricated as described above.

[0032] During operation, the MIT material 902 acts as a selector for the memory 920 in response to heat generated by the Joule heater 904. Specifically, changing the conductivity of the MIT material 902 using the Joule heater 904 can be used to sense or change the state of the memory 920.

[0033] FIG. 10 shows a memory element for a 3D vertical memory array according to one embodiment. Referring to FIG. 10, the memory element 1000 includes an MIT material 1002 separated from a Joule heater 1004 by an insulator 1006a. A memory 1020 is disposed between the MIT material 1002 and a metal line 1008. The metal line 1008 and the memory 1020 are separated from adjacent metal lines and memories by isolators 1006b, c. Of the isolators, the isolator 1006a is not essential and may be removed or omitted. These elements can be fabricated as described above. When included in a 3D vertical memory array, the MIT material 1002 can act as a vertical electrode.

[0034] During operation, the MIT material 1002 acts as a selector for the memory 1020 in response to heat generated by the Joule heater 1004. Specifically, changing the conductivity of the MIT material 1002 using the Joule heater 1004 can be used to sense and change the state of the memory.

[0035] FIG. 11 shows a portion of a cross-point memory array fabricated using the memory element 800 of FIG. 8. Referring to FIG. 11, the cross-point memory array 1100 includes six memory elements 800a, b, c, d, e, f. Pairs of metal contacts 808 of the memory element 800 are joined to form three bit lines 1108a, b, c. The metal lines 810 of the memory element 800 intersect and are joined to form two word lines 1110a, b. By manipulating the voltage / current in the bit lines 1108 and the word lines 1110, the thermal switch of the array 1100 can be used to perform a memory operation on the memory element 800 within the array 1100.

[0036] FIG. 12 shows a portion of a cross-point memory array fabricated using the memory element 900 of FIG. 9. Referring to FIG. 12, the cross-point memory array 1200 includes six memory elements 900a, b, c, d, e, f. Pairs of metal contacts 908 of the memory element 900 are joined to form three bit lines 1208a, b, c. The metal lines 910 of the memory element 900 intersect and are joined to form two word lines 1210a, b. By manipulating the voltage / current in the bit lines 1208 and the word lines 1210, the thermal switch of the array 1200 can be used to perform a memory operation on the memory element 900 within the array 1200.

[0037] In some embodiments of the disclosed memory arrays, a temperature field fringing effect may occur. That is, the joule heater of one memory element may affect one or more adjacent memory elements. FIG. 13 shows the temperature field fringing effect. Referring to FIG. 13, two memory elements 1340a, b connected by bit line 1308 are shown. When word line 1310a of memory element 1340a is selected, the temperature of joule heater 1304a of that memory element 1340a increases. Without proper thermal isolation, the joule heater 1304a in the selected word line 1310a may heat the MIT material 1302b in the non - selected word line 1310a above its transition temperature, unexpectedly changing the state of the associated memory 1320b and thereby introducing an error into the array 1300. To prevent this temperature fringing effect, as shown in FIG. 13, a thermal isolator 1330 having a low thermal conductivity can be placed between the memory elements 1340. This configuration prevents the temperature field fringing effect and thereby improves the performance and reliability of the array 1300. The joule heaters 1304a, b are each disposed within metal lines 1310a, b and can be separated from the metal lines 1310a, b by adding isolators 1306a, b. However, the isolators 1306a, b are optional and not essential and may be omitted or removed. If the isolators 1306a, b are omitted or removed, each heater 1304a, b and its respective metal line 1310a, b can be combined by using the same single metal line.

[0038] To improve power efficiency, constriction techniques can be used to concentrate Joule heating near the thermal switch. Due to current continuity, the constricted section of the Joule heater will have a higher current density, and thus a higher density of heat generation, and a higher temperature. In this way, high temperatures are generated only where needed. This technique also helps to control the thermal budget of the integrated circuit in which the thermal switch is implemented and to improve reliability.

[0039] FIG. 14 shows the nanowire constriction technique. Referring to FIG. 14, the nanowire 1404 is constricted at 1408 near the MIT material 1402, thereby creating a Joule heater for the MIT material 1402.

[0040] FIG. 15 shows the nanopore constriction technique. Referring to FIG. 15, the nanopore 1510 is created within a nanowire near the MIT material 1502, thereby creating a Joule heater for the MIT material 1502.

[0041] In addition to the selector for the cross-point or 3D vertical memory array described, the disclosed thermal switch has numerous other applications. For example, the disclosed thermal switch can be used for the high-temperature formation and cycling of resistive memory devices to achieve better overall performance.

[0042] The disclosed thermal switch can be used as an on-chip heater to enable block erasure of memory cells at high temperatures. Memories such as phase change memories and resistive memories are generally erased at a temperature of 100 °C. The heater implemented using the disclosed thermal switch can raise the temperature of such memories to 400 °C or higher, ensuring that they are erased. One application of this technology is for systems that require secure self-destruction.

[0043] The disclosed thermal switch can be used as a temperature surge protector for integrated circuits.

[0044] The disclosed thermal switch can be used as a block activation and deactivation switch in an integrated circuit to achieve low-power operation.

[0045] The disclosed thermal switch can be used as a reliable optical switch in a photonic circuit.

[0046] The disclosed thermal switch can be used in place of a transistor in a thermocomputing (phonon) system. The disclosed thermal switch is not limited to having a positive correlation between conductivity and temperature, and can also be used with a thermal switch having a negative correlation to create a complementary thermal logic circuit.

[0047] Examples and features of the disclosed principles have been described herein, but modifications, adaptations, and other implementations are possible without departing from the spirit and scope of the disclosed embodiments. Also, the terms "comprising", "having", "containing", and "including", and other similar forms, are equivalent in meaning in that one or more items following any one of these terms do not comprehensively enumerate such one or more items, nor are they limited to only the one or more items listed, and are intended to be open-ended. Also, it should be noted that the singular forms "a", "an", and "the" used in this specification and the appended "claims" include plural references unless the context clearly indicates a different interpretation.

[0048] It will be understood that the present invention is not limited to the exact configuration described above and shown in the accompanying drawings, and various changes and modifications can be made without departing from its scope. The invention disclosed herein includes the following. [Aspect 1] A thermal switch, A metal-insulator transition (MIT) material, and a first terminal and a second terminal electrically coupled to the MIT material, and a heater disposed near the MIT material, and A thermal switch comprising the above. [Aspect 2] The thermal switch according to aspect 1, further comprising an electrical insulator disposed between the MIT material and the heater. [Aspect 3] The heater The thermal switch according to aspect 1, comprising a Joule heater. [Aspect 4] The thermal switch according to aspect 3, further comprising third and fourth terminals electrically coupled to the heater, wherein the Joule heater generates heat when current passes through the Joule heater and the third and fourth terminals. [Aspect 5] The thermal switch according to aspect 3, wherein the Joule heater comprises at least one of a constriction in a nanowire or a nanopore in a nanowire. [Aspect 6] The state of the MIT material can be detected at the first terminal and the second terminal, and the state comprises a metallic state and an insulating state. The thermal switch according to aspect 1. [Aspect 7] The state of the MIT material can be changed at the first terminal and the second terminal, and the state comprises a metallic state and an insulating state. The thermal switch according to aspect 1. [Aspect 8] A memory device, comprising a memory, and a memory selector electrically coupled to the memory, and The memory selector comprises a metal-insulator transition (MIT) material, and a heater disposed near the MIT material, and A memory device comprising the above. [Aspect 9] The memory device according to aspect 8, further comprising an electrical insulator disposed between the MIT material and the heater. [Aspect 10] The memory device according to aspect 8, wherein the heater comprises a Joule heater. [Aspect 11] The memory device according to aspect 10, wherein the Joule heater comprises at least one constriction in a nanowire or a nanopore in a nanowire. [Aspect 12] The memory device according to aspect 10, further comprising a first terminal and a second terminal electrically coupled to the Joule heater, wherein the Joule heater generates heat when current passes through the Joule heater and the first terminal and the second terminal. [Aspect 13] A first terminal electrically coupled to the MIT material, A second terminal electrically coupled to the memory, and further comprising wherein the state of the MIT material can be changed at the first terminal and the second terminal, and the state of the MIT material comprises a metallic state and an insulator state, The memory device according to aspect 8, wherein the state of the memory can be changed and detected at the first terminal and the second terminal. [Aspect 14] The memory device according to aspect 13, further comprising an electrical insulator disposed between the heater and the first terminal. [Aspect 15] The memory device according to aspect 13, further comprising one or more electrical insulators disposed between the heater and at least one of the MIT material, the memory, the first terminal, or the second terminal. [Aspect 16] A cross-point memory array, an array of memory elements arranged in rows and columns, wherein each memory element comprises a memory, a memory selector electrically coupled to the memory, A metal-insulator transition (MIT) material, and a Joule heater disposed near the MIT material, and a memory selector comprising the same, and an array of memory elements comprising the same, and a plurality of first metal lines each electrically coupled to the memory of the memory elements within each column, and a plurality of second metal lines each electrically coupled to the memory of the memory elements within each row, and A cross-point memory array comprising the same. [Aspect 17] The cross-point memory array according to Aspect 16, further comprising a plurality of thermal isolators disposed between the memory elements. [Aspect 18] Each of the memory elements further comprises an electrical insulator disposed between the Joule heater and each of the second metal lines, in the cross-point memory array according to Aspect 16. [Aspect 19] Each of the memory elements further comprises one or more electrical insulators disposed between the Joule heater and at least one of the MIT material, the memory, each of the first metal lines, or each of the second metal lines, in the cross-point memory array according to Aspect 16. [Aspect 20] Each of the Joule heaters comprises at least one of a constriction in a nanowire or a nanopore in a nanowire, in the cross-point memory array according to Aspect 16.

Claims

1. A thermal switch comprising: a metal-insulator transition (MIT) material; a first terminal and a second terminal electrically coupled to the MIT material; a Joule heater comprising a constriction in a nanowire near the MIT material, wherein in a cross-sectional view taken in a direction in which current flows through the Joule heater, the top, bottom, left, and right of the Joule heater are surrounded by an isolator disposed near the MIT material, and the Joule heater generates heat when current passes through the Joule heater to change the state of the MIT material between a metallic state and an insulating state; A thermal switch.

2. The thermal switch according to claim 1, further comprising third and fourth terminals electrically coupled to the Joule heater, wherein the Joule heater generates heat when current passes through the Joule heater and the third and fourth terminals.

3. The thermal switch according to claim 1, wherein the state of the MIT material can be detected at the first terminal and the second terminal, and the state comprises a metallic state and an insulating state.

4. A memory device comprising: a memory; a memory selector electrically coupled to the memory; wherein the memory selector comprises: a metal-insulator transition (MIT) material; a Joule heater comprising a constriction in a nanowire near the MIT material, wherein in a cross-sectional view taken in a direction in which current flows through the Joule heater, the top, bottom, left, and right of the Joule heater are surrounded by an isolator disposed near the MIT material, and the Joule heater generates heat when current passes through the Joule heater to change the state of the MIT material between a metallic state and an insulating state; A memory device.

5. The memory device according to claim 4, further comprising a first terminal and a second terminal electrically coupled to the Joule heater, wherein the Joule heater generates heat when current passes through the Joule heater and the first terminal and the second terminal.

6. A first terminal electrically coupled to the MIT material; a second terminal electrically coupled to the memory; further comprising: The memory device according to claim 4, wherein the state of the memory can be detected at the first terminal and the second terminal.

7. The memory device according to claim 6, further comprising an electrical insulator disposed between the Joule heater and the first terminal.

8. The memory device according to claim 6, further comprising one or more electrical insulators disposed between the Joule heater and at least one of the MIT material, the memory, the first terminal, or the second terminal.

9. A cross-point memory array, An array of memory elements arranged in rows and columns, each memory element comprising A memory, A memory selector electrically coupled to the memory, A metal-insulator transition (MIT) material, A Joule heater comprising a constriction in a nanowire near the MIT material, wherein in a cross-sectional view in a cross-section taken in the direction in which current flows through the Joule heater, the top, bottom, left, and right of the Joule heater are surrounded by isolators disposed near the MIT material, and heat is generated when current passes through the Joule heater to change the state of the MIT material between a metallic state and an insulating state. A Joule heater, A memory selector comprising, An array of memory elements comprising, A plurality of first metal lines each electrically coupled to the memory of the memory elements within each column, A plurality of second metal lines each electrically coupled to the memory of the memory elements within each row, A cross-point memory array comprising.

10. The cross-point memory array according to claim 9, further comprising a plurality of thermal isolators disposed between the memory elements.

11. Each of the memory elements of the cross-point memory array according to claim 9 further comprises an electrical insulator disposed between the Joule heater and each of the second metal lines.

12. Each of the memory elements of the cross-point memory array according to claim 9 further comprises one or more electrical insulators disposed between the Joule heater and at least one of the MIT material, the memory, each of the first metal lines, or each of the second metal lines.

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