Random access memory including nanotube switching elements
View Patent ↗Random access memory including nanotube switching elements. A memory cell includes first and second nanotube switching elements and an electronic memory. Each nanotube switching element includes conductive terminals, a nanotube article and control circuitry capable of controllably form and unform an electrically conductive channel between the conductive terminals. The electronic memory is a volatile storage device capable of storing a logic state in response to electrical stimulus. In certain embodiment the electronic memory has cross-coupled first and second inverters in electrical communication with the first and second nanotube switching elements. The cell can operate as a normal electronic memory, or can operate in a shadow memory or store mode (e.g., when power is interrupted) to transfer the electronic memory state to the nanotube switching elements. The device may later be operated in a recall mode where the state of the nanotube switching elements may be transferred to the electronic memory.
1. A memory cell, comprising
first and second nanotube switching elements, each nanotube switching element capable of at least two memory states and each nanotube switching element comprising:
first and second conductive terminals;
a nanotube article having at least one electrically conductive nanotube, said article physically disposed between and capable of electrical communication with the first and second conductive terminals;
control structure capable of controllably forming and unforming an electrically conductive channel between said first and second conductive terminals wherein said channel includes said nanotube article; and
an electronic memory element capable of at least two memory states and having cross-coupled first and second inverters wherein an input node of the first inverter is coupled to an output node of the second inverter and an input node of the second inverter is coupled to an output node of the first inverter;
wherein the input node of the first inverter is coupled to the control structure of the first nanotube switching element and to the second conductive terminal of the second nanotube switching element; and
wherein the input node of the second inverter is coupled to the control structure of the second nanotube switching element and to the second conductive terminal of the first nanotube switching element; and
wherein the control circuitry selectively transfers the state of the electronic memory to the state of the nanotube switching elements and selectively transfers the state of the nanotube switching elements to the state of the electronic memory.
2. The memory cell of claim 1 wherein the control circuitry includes a pair of electrodes disposed on opposite sides of the nanotube article, capable of electromechanically deflecting the nanotube article to controllably form and unform the conductive channel.
3. The memory cell of claim 1 wherein the control circuitry includes a channel voltage line and wherein the first conductive terminal of the second nanotube switching element and the first conductive terminal of the first nanotube switching element are coupled to the channel voltage line.
4. The memory cell of claim 1 wherein the first and second nanotube switching elements comprise nonvolatile state devices.