The Experts below are selected from a list of 80235 Experts worldwide ranked by ideXlab platform
Noboru Yamazoe - One of the best experts on this subject based on the ideXlab platform.
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Theory of power laws for semiconductor Gas sensors
Sensors and Actuators B: Chemical, 2008Co-Authors: Noboru Yamazoe, Kengo ShimanoeAbstract:It has long been known empirically that the electric resistance of a semiconductor Gas sensor under exposure to a Target Gas (partial pressure P) is proportional to Pn where n is a constant fairly specific to the kind of Target Gas (power law). This paper aims at providing a theoretical basis to such power laws. It is shown that the laws can be derived by combining a depletion theory of semiconductor, which deals with the distribution of electrons between surface state (surface charge) and bulk, with the dynamics of adsorption and/or reactions of Gases on the surface, which is responsible for accumulation or reduction of surface charges. The resulting laws describe well sensor response behavior to oxygen, reducing Gases and oxidizing Gases.
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formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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Formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction–diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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theory of Gas diffusion controlled sensitivity for thin film semiconductor Gas sensor
Sensors and Actuators B-chemical, 2001Co-Authors: Go Sakai, Naoki Matsunaga, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract Influences of Gas transport phenomena on the sensitivity of a thin film semiconductor Gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable Gas (Target Gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the Target Gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The Gas concentration profile thus obtained allowed to estimate the Gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the Gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L k/D K . Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation.
Kengo Shimanoe - One of the best experts on this subject based on the ideXlab platform.
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Theory of power laws for semiconductor Gas sensors
Sensors and Actuators B: Chemical, 2008Co-Authors: Noboru Yamazoe, Kengo ShimanoeAbstract:It has long been known empirically that the electric resistance of a semiconductor Gas sensor under exposure to a Target Gas (partial pressure P) is proportional to Pn where n is a constant fairly specific to the kind of Target Gas (power law). This paper aims at providing a theoretical basis to such power laws. It is shown that the laws can be derived by combining a depletion theory of semiconductor, which deals with the distribution of electrons between surface state (surface charge) and bulk, with the dynamics of adsorption and/or reactions of Gases on the surface, which is responsible for accumulation or reduction of surface charges. The resulting laws describe well sensor response behavior to oxygen, reducing Gases and oxidizing Gases.
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formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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Formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction–diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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theory of Gas diffusion controlled sensitivity for thin film semiconductor Gas sensor
Sensors and Actuators B-chemical, 2001Co-Authors: Go Sakai, Naoki Matsunaga, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract Influences of Gas transport phenomena on the sensitivity of a thin film semiconductor Gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable Gas (Target Gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the Target Gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The Gas concentration profile thus obtained allowed to estimate the Gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the Gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L k/D K . Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation.
Naoki Matsunaga - One of the best experts on this subject based on the ideXlab platform.
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formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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Formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction–diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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theory of Gas diffusion controlled sensitivity for thin film semiconductor Gas sensor
Sensors and Actuators B-chemical, 2001Co-Authors: Go Sakai, Naoki Matsunaga, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract Influences of Gas transport phenomena on the sensitivity of a thin film semiconductor Gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable Gas (Target Gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the Target Gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The Gas concentration profile thus obtained allowed to estimate the Gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the Gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L k/D K . Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation.
Go Sakai - One of the best experts on this subject based on the ideXlab platform.
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formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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Formulation of Gas diffusion dynamics for thin film semiconductor Gas sensor based on simple reaction–diffusion equation
Sensors and Actuators B-chemical, 2003Co-Authors: Naoki Matsunaga, Go Sakai, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract In response and recovery steps of a thin film semiconductor Gas sensor, Target Gas molecules diffuse in and out of the thin film. The Gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction–diffusion equation assuming a first-order reaction of Target Gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction–diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D , rate constant k , film thickness L , depth x and time t , are shown to express well how Target Gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively.
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theory of Gas diffusion controlled sensitivity for thin film semiconductor Gas sensor
Sensors and Actuators B-chemical, 2001Co-Authors: Go Sakai, Naoki Matsunaga, Kengo Shimanoe, Noboru YamazoeAbstract:Abstract Influences of Gas transport phenomena on the sensitivity of a thin film semiconductor Gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable Gas (Target Gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the Target Gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The Gas concentration profile thus obtained allowed to estimate the Gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the Gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L k/D K . Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation.
Luigi Sangaletti - One of the best experts on this subject based on the ideXlab platform.
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Enhanced selectivity of Target Gas molecules through a minimal array of Gas sensors based on nanoparticle-decorated SWCNTs
The Analyst, 2019Co-Authors: Sonia Freddi, Giovanni Drera, Stefania Pagliara, Andrea Goldoni, Luigi SangalettiAbstract:An array of five sensors, based on carbon nanotubes (CNT) functionalized with nanoparticles of Au, TiO2, ITO, and Si has been fabricated and exposed to a selected series of Target Gas molecules (NH3, NO2, H2S, H2O, benzene, ethanol, acetone, 2-propanol, sodium hypochlorite, and several combinations of two Gases). The results of principal component analysis (PCA) of the experimental data show that this array of sensors is able to detect different Target Gas and to discriminate each molecule in the 2D PCA parameters space. In particular, the possibility to include in the array a humidity sensor significantly increases the capability to discriminate the response to volatile organic compounds (VOCs), even though VOCs usually react with CNTs less than NO2 or NH3. This leads to an improvement in selectivity that could meet the requirements for Gas detection applications in the field of environmental monitoring and breathomics, where sensors are exposed to a variety of different molecules and where the humidity can severely affect the overall response of the sensor. Finally, we demonstrate that the ability to test multiple sensors simultaneously can reveal a specific sensor sensitivity, addressing the best functionalization choice to improve the response of new sensors based on decorated CNT layers. In particular, our study shows the better capability of the ITO-decorated sensor to detect H2S and benzene.
