Abstract: A gas monitoring system includes at least one sensor device that detects gas and outputs a detection result; and a gateway that receives the detection result. The at least one sensor device includes a sensor module having a gas sensor that detects gas; an analog-to-digital (A/D) converter that processes the detection result outputted from the gas sensor; a communication module that communicates with the sensor module and transmits information processed by the A/D converter exteriorly of the at least one sensor device; a power source that is an electric power source of the sensor module; and a power source that is an electric power source of the communication module.

Abstract: Provided is a gas detection device that includes a gas sensor, a power supply circuit that applies voltage to the gas sensor, and a control circuit that determines whether a leak of gas is present. The power supply circuit includes a reset power source that generates a first voltage, and a detection power source that generates a detection voltage for measuring resistance of a metal-oxide layer of the gas sensor. When a value of a current flowing through the metal-oxide layer is a predetermined value ITH or greater, the reset power source applies the first voltage to the gas sensor to perform a reset of resetting the metal-oxide layer of the gas sensor to a high-resistance state, and the control circuit determines that a leak of gas is present, depending on a state in which the reset is performed after the reset is performed for the first time.

Abstract: A gas sensor driving method for a gas sensor that (i) includes: a first electrode including a first principal surface; a second electrode including a second principal surface; a metal-oxide layer interposed between the first principal surface and the second principal surface that face each other; and an insulating film covering the first electrode, the metal-oxide layer, and the second electrode, and exposing at least a part of a third principal surface of the second electrode, the third principal surface being disposed on an opposite side of the second principal surface, and (ii) detects hydrogen in accordance with a change in a resistance value of the metal-oxide layer. The gas sensor driving method includes repeatedly applying a positive voltage and a negative voltage across the first electrode and the second electrode.

Abstract: A gas sensor includes: a first electrode; a metal oxide layer that is on the first electrode and has a resistance value that changes when the metal oxide layer contacts hydrogen atoms; a second electrode on the metal oxide layer; and an insulating film that covers at least a part of side surfaces of the first electrode, the metal oxide layer, and the second electrode. In the metal oxide layer, a part of a first interface between the first electrode and the metal oxide layer is not covered by the insulating film and is exposed to a gas.

Abstract: A gas monitoring system includes at least one sensor device that detects gas and outputs a detection result; and a gateway that receives the detection result. The at least one sensor device includes a sensor module having a gas sensor that detects gas; an analog-to-digital (A/D) converter that processes the detection result outputted from the gas sensor; a communication module that communicates with the sensor module and transmits information processed by the A/D converter exteriorly of the at least one sensor device; a power source that is an electric power source of the sensor module; and a power source that is an electric power source of the communication module.

Abstract: Provided is a gas detection device that includes a gas sensor, a power supply circuit that applies voltage to the gas sensor, and a control circuit that determines whether a leak of gas is present. The power supply circuit includes a reset power source that generates a first voltage, and a detection power source that generates a detection voltage for measuring resistance of a metal-oxide layer of the gas sensor. When a value of a current flowing through the metal-oxide layer is a predetermined value ITH or greater, the reset power source applies the first voltage to the gas sensor to perform a reset of resetting the metal-oxide layer of the gas sensor to a high-resistance state, and the control circuit determines that a leak of gas is present, depending on a state in which the reset is performed after the reset is performed for the first time.

Abstract: A gas-detecting apparatus includes a measurement circuit including a gas sensor and a measurement instrument and a decision circuit. Detection cells, included in the gas sensor, each include a first electrode, a second electrode having a surface exposed from an insulation layer, and a metal oxide layer disposed between the first electrode and the second electrode. The resistance values of the detection cells are each allowed to decrease by a contact of gas containing hydrogen atoms with the second electrode. The measurement instrument monitors the resistance values of the detection cells. The decision circuit decides whether the gas is detected or not based on at least one change of the resistance values.

Abstract: A gas sensor includes: a first electrode; a metal oxide layer that is on the first electrode and has a resistance value that changes when the metal oxide layer contacts hydrogen atoms; a second electrode on the metal oxide layer; and an insulating film that covers at least a part of side surfaces of the first electrode, the metal oxide layer, and the second electrode. In the metal oxide layer, a part of a first interface between the first electrode and the metal oxide layer is not covered by the insulating film and is exposed to a gas.

Abstract: A gas-detecting apparatus includes a gas sensor and a power supply circuit. The gas sensor includes: a first electrode; a second electrode; a metal oxide layer disposed between the first electrode and the second electrode; and an insulation film covering the first electrode, the second electrode, and the metal oxide layer. The insulation file having an opening from which a surface of the second electrode is exposed. The resistance value of the metal oxide layer decreases when gas containing hydrogen atoms comes into contact with the second electrode. The power supply circuit applies a predetermined voltage between the first electrode and the second electrode to increase the resistance value of the metal oxide layer before and/or after the decrease in the resistance value of the metal oxide layer.

Abstract: An estimation method for a variable resistance element including (i) a first electrode, (ii) a second electrode, and therebetween (iii) a variable resistance layer in which a local region is formed which has resistive status that reversibly changes according to an electric pulse applied between the first electrode and the second electrode, the estimation method including: obtaining, when changes are made to the resistive status of the local region, measurement values each indicating a resistance state after one of the changes; and determining, based on a distribution of the obtained measurement values, an estimated amount of a physical parameter regarding structural characteristics of the local region by a calculation.

Abstract: A gas-detecting apparatus includes a gas sensor and a power supply circuit. The gas sensor includes: a first electrode; a second electrode; a metal oxide layer disposed between the first electrode and the second electrode; and an insulation film covering the first electrode, the second electrode, and the metal oxide layer. The insulation file having an opening from which a surface of the second electrode is exposed. The resistance value of the metal oxide layer decreases when gas containing hydrogen atoms comes into contact with the second electrode. The power supply circuit applies a predetermined voltage between the first electrode and the second electrode to increase the resistance value of the metal oxide layer before and/or after the decrease in the resistance value of the metal oxide layer.

Abstract: A gas-detecting apparatus includes a measurement circuit including a gas sensor and a measurement instrument and a decision circuit. Detection cells, included in the gas sensor, each include a first electrode, a second electrode having a surface exposed from an insulation layer, and a metal oxide layer disposed between the first electrode and the second electrode. The resistance values of the detection cells are each allowed to decrease by a contact of gas containing hydrogen atoms with the second electrode. The measurement instrument monitors the resistance values of the detection cells. The decision circuit decides whether the gas is detected or not based on at least one change of the resistance values.

Abstract: A method of driving a variable resistance element comprises: before a first write step is performed, applying an initial voltage pulse of a first polarity to change a resistance value of a metal oxide layer from a resistance value corresponding to an initial state of the metal oxide layer to another resistance value; wherein when the resistance value corresponding to the initial state is R0, the resistance value corresponding to a write state is RL, the resistance value corresponding to an erase state is RH, another resistance value is R2, a maximum value of the current flowing when the initial voltage pulse is applied is IbRL, a maximum value of the current flowing when the write voltage pulse is applied is IRL, and a maximum value of the current flowing when the erase voltage pulse is applied is IRH, R0>RH>R2?RL, and |IRL|>|IbRL| are satisfied.

Abstract: A variable resistance nonvolatile memory device includes: a nonvolatile memory element; an NMOS transistor connected to the nonvolatile memory element; a source line connected to the NMOS transistor; a bit line connected to the nonvolatile memory element. When a control circuit causes the nonvolatile memory element to be in the low resistance state, the control circuit controls to flow a first current from a first voltage source to a reference potential point, and applies a first gate voltage to a gate of a NMOS transistor, and when the control circuit causes the nonvolatile memory element to be in the high resistance state, the control circuit controls to flow a second current from a second voltage source to the reference potential point, and applies a second gate voltage to the gate of the NMOS transistor, the second gate voltage being lower than the first gate voltage.

Abstract: A nonvolatile memory element of the present invention comprises a first electrode (103), a second electrode (105), and a resistance variable layer (104) disposed between the first electrode (103) and the second electrode (104), a resistance value of the resistance variable layer varying reversibly according to an electric signal applied between the electrodes (103), (105), and the resistance variable layer (104) comprises at least a tantalum oxide, and is configured to satisfy 0<x<2.5 when the tantalum oxide is represented by TaOx.

Abstract: A variable resistance nonvolatile memory device includes: a nonvolatile memory element; an NMOS transistor connected to the nonvolatile memory element; a source line connected to the NMOS transistor; a bit line connected to the nonvolatile memory element. When a control circuit causes the nonvolatile memory element to be in the low resistance state, the control circuit controls to flow a first current from a first voltage source to a reference potential point, and applies a first gate voltage to a gate of a NMOS transistor, and when the control circuit causes the nonvolatile memory element to be in the high resistance state, the control circuit controls to flow a second current from a second voltage source to the reference potential point, and applies a second gate voltage to the gate of the NMOS transistor, the second gate voltage being lower than the first gate voltage.

Abstract: Provided is a method for driving a variable resistance nonvolatile storage element that can improve the information holding capability. The method includes: determining whether or not a current that flows through the nonvolatile storage element is larger than or equal to a first verify level IRL (Verify); determining whether or not a current that flows through the nonvolatile storage element is smaller than or equal to a second verify level IRH (Verify); and determining that the nonvolatile storage element is in the second resistance state when the current that flows through the nonvolatile storage element is smaller than a current reference level Iref, and determining that the nonvolatile storage element is in the first resistance state when the current is larger than the current reference level Iref, the current reference level Iref satisfying (IRL (Verify)+IRH (Verify))/2<Iref<IRL (Verify).

Abstract: A method for driving a nonvolatile memory element includes: a writing step of changing a variable resistance layer to a low resistance state, by applying a writing voltage pulse having a first polarity; and an erasing step of changing the variable resistance layer to a high resistance state, by applying an erasing voltage pulse having a second polarity different from the first polarity, wherein in the writing step, a first input and output terminal of a field effect transistor is a source terminal of the transistor, and when a pulse width of the writing voltage pulse is PWLR and a pulse width of the erasing voltage pulse is PWHR, PWLR and PWHR satisfy a relationship of PWLR<PWHR.

Abstract: A method of driving a nonvolatile memory element including a variable resistance element having a state reversibly changing between low and high resistance states by an applied electrical signal and a transistor serially connected to the variable resistance element. The method including: setting the variable resistance element to the low resistance state by applying a first gate voltage to a gate of the transistor and applying a first write voltage negative with respect to a first electrode; and changing a resistance value of the transistor obtained in a low-resistance write operation, when a value of current passing through the variable resistance element in the setting of the low resistance state or a resistance value of the nonvolatile memory element in the case where the variable resistance element is in the low resistance state is outside a predetermined range.

Abstract: In a nonvolatile memory element, when a voltage value of an electric pulse has a relationship of V2>V1>0 V>V3>V4 and a resistance value of a variable resistance layer has a relationship of R3>R2>R4>R1, the resistance value of the variable resistance layer becomes: R2, when the electric pulse having a voltage value of V2 or greater is applied between electrodes; R4, when the electric pulse having a voltage value of V4 or smaller is applied between the electrodes; R3, when the resistance value of the variable resistance layer is R2 and the electric pulse having a voltage value of V3 is applied between the electrodes; and R1, when the resistance value of the variable resistance layer is R4 and the electric pulse having a voltage value of V1 is applied between the electrodes.