Pulse Biasing Scheme for the Fast Recovery of FET-Type Gas Sensors for Reducing Gases

Wu, Meile,Shin, Jongmin,Hong, Yoonki,Jin, Xiaoshi,Lee, Jong-Ho IEEE 2017 IEEE electron device letters Vol.38 No.7

<P>The promotive effect of a pre-bias condition on the recovery speed of a field-effect transistor-type gas sensor, which has a horizontal controlgate (CG) and floating gate (FG), is investigated in this letter. To verify the pre-bias effect in the recovery phase after the detection of H2S gas, a type of reducing gas, a 200-nm-thick layer of SnOx is deposited on top of the interdigitated CG and FG as a sensing material. A pulse measurement method is proposed to improve the recovery speed of the sensor for H2S gas sensing by applying a negative pre-bias condition to the CG before the read operation of the sensor. This method greatly accelerates the recovery and reduces the recovery time by 74% with a pre-bias of -3 V at 180 degrees C. The mechanism is explained in terms of energy band theory. The pre-biasing method used with our gas sensor is beneficial for the continuous monitoring and for the rapid detection of various gases.</P>

The Optimal Design of Junctionless Transistors with Double-Gate Structure for reducing the Effect of Band-to-Band Tunneling

Wu, Meile,Jin, Xiaoshi,Kwon, Hyuck-In,Chuai, Rongyan,Liu, Xi,Lee, Jong-Ho The Institute of Electronics and Information Engin 2013 Journal of semiconductor technology and science Vol.13 No.3

The effect of band-to-band tunneling (BTBT) leads to an obvious increase of the leakage current of junctionless (JL) transistors in the OFF state. In this paper, we propose an effective method to decline the influence of BTBT with the example of n-type double gate (DG) JL metal-oxide-semiconductor field-effect transistors (MOSFETs). The leakage current is restrained by changing the geometrical shape and the physical dimension of the gate of the device. The optimal design of the JL MOSFET is indicated for reducing the effect of BTBT through simulation and analysis.

An FET-Type Gas Sensor for CO₂ Detection at Room Temperature using PEI-Coated SWNT

Meile Wu,Yoonki Hong,Dongkyu Jang,Xiaoshi Jin,Jong-Ho Lee 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.2

An FET-type CO₂ sensor using polyethylenimine (PEI) coated single-walled carbon nanotube (SWNT) is investigated. The sensor has a floating-gate (FG) and a control-gate (CG) formed in an interdigitated form in a horizontal direction. SWNT and PEI are sequentially printed on the platform by inkjet printing process. PEI coating reduces the I-V hysteresis of the FET platform and improves the CO₂ sensing properties. Since the sensor has an FG that can store the charge, the threshold voltage of the sensor can be tuned and its calibration is possible. When sensing 2000 ppm of CO₂ gas at room temperature, the DC read bias applied to CG showed very low sensitivity and significant drift characteristics. However, by applying a pulse bias, a response of ~16%, a response time of ~80 s, and a recovery time of ~200 s were obtained.

An FET-type gas sensor with a sodium ion conducting solid electrolyte for CO₂ detection

Wu, Meile,Shin, Jongmin,Hong, Yoonki,Jang, Dongkyu,Jin, Xiaoshi,Kwon, Hyuck-In,Lee, Jong-Ho Elsevier 2018 Sensors and actuators. B, Chemical Vol.259 No.-

<P><B>Abstract</B></P> <P>In this paper, a Field-Effect-Transistor (FET)-type gas sensor using the composite of Na<SUB>2</SUB>CO<SUB>3</SUB> and NaNO<SUB>2</SUB> as the sensing material is investigated. The sensor has a floating gate (FG) passivated by an insulator stack and a control gate (CG), which are formed in an interdigitated form in a horizontal direction. The inkjet printing process forms the sensing material on the interdigitated FG and CG. Just before forming the sensing material, a (3-aminopropyl) triethoxysilane (APTES) monolayer is formed to prevent diffusion of Na<SUP>+</SUP> ions contained in the sensing material through the insulator layer. The sensor can be electrically programmed like a typical memory device due to the FG, which makes the calibration of the sensor possible. CO<SUB>2</SUB> gas sensing properties of the sensor are characterized at an operating temperature of 160 °C. The results indicate that the proposed sensor produces a reasonable and repeatable response to a certain concentration of CO<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A programmable FET-type CO<SUB>2</SUB> sensor with a Na+ solid electrolyte is proposed. </LI> <LI> The proposed sensor has reasonable and repeatable response to CO<SUB>2</SUB> at 160 °C. </LI> <LI> An APTES monolayer effectively prevents Na+ ions diffusing through insulators. </LI> <LI> The sensing principle is explained and modeled based on electrochemical theory. </LI> </UL> </P>

Effect of a pre-bias on the adsorption and desorption of oxidizing gases in FET-type sensor

Wu, Meile,Kim, Chang-Hee,Shin, Jongmin,Hong, Yoonki,Jin, Xiaoshi,Lee, Jong-Ho Elsevier 2017 Sensors and actuators. B Chemical Vol.245 No.-

<P><B>Abstract</B></P> <P>An efficient pre-bias method is proposed in the reading operation of a Field-Effect-Transistor(FET)-type gas sensor which utilizes flatband voltage change of the sensing material formed between the control-gate (CG) and floating-gate (FG) of the FET. The proposed method improves greatly recovery speed and shortens recovery time by more than 10 times at 180°C, which can reduce the power consumed by heater. Since the polarity of the pre-bias affects response, sensing and recovery speeds, it is possible to identify the redox characteristics of the detected gas. To verify experimentally the pre-bias effect, we apply pulses for the pre-biasing and reading to the sensor with a sensing material of 200-nm-thick SnO<SUB>x</SUB> layer to detect NO<SUB>2</SUB> gas as an example. The mechanism is explained theoretically by energy band theory. The pre-biasing method is expected to open a new biasing scheme which improves significantly sensing characteristics, gas identification, and power dissipation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pulse measurement method including pre-bias before reading operation was proposed. </LI> <LI> The polarity of the pre-bias affects response, sensing and recovery speeds. </LI> <LI> Principle responsible for the effect was explained by using energy band diagrams. </LI> <LI> A pulse cycle to enhance both response and recovery properties was provided. </LI> </UL> </P>

The Optimal Design of Junctionless Transistors with Double-Gate Structure for reducing the Effect of Band-to-Band Tunneling

Meile Wu,Xiaoshi Jin,Hyuck-In Kwon,Rongyan Chuai,Xi Liu,Jong-Ho Lee 대한전자공학회 2013 Journal of semiconductor technology and science Vol.13 No.3

The effect of band-to-band tunneling (BTBT) leads to an obvious increase of the leakage current of junctionless (JL) transistors in the OFF state. In this paper, we propose an effective method to decline the influence of BTBT with the example of ntype double gate (DG) JL metal-oxide-semiconductor field-effect transistors (MOSFETs). The leakage current is restrained by changing the geometrical shape and the physical dimension of the gate of the device. The optimal design of the JL MOSFET is indicated for reducing the effect of BTBT through simulation and analysis.

AI-Driven Innovation: Transforming the Visual Design Landscape through Generative Tools

Yuanchen Wu,Jidong Liu,Meile Le 한국HCI학회 2024 한국HCI학회 학술대회 Vol.2024 No.1

This study delves into the transformative effects of integrating generative Artificial Intelligence (AI) tools in the visual design process, aiming to enhance design methodologies. Through in-depth expert interviews, it underscores AIs significant role in three critical phases: the problem identification and definition phase, and the ideation phase. The findings reveal that AI not only elevates the efficiency and fidelity of the design process but also significantly improves communication between designers and clients. This underscores the potential of AI in fostering a novel, innovative design approach, one that is adaptive and responsive to the evolving trends in the market, thereby setting a new standard in the realm of visual design.

A Wide Detection Range Mercury Ion Sensor Using Si MOSFET Having Single-Walled Carbon Nanotubes as a Sensing Layer

Shin, Jongmin,Hong, Yoonki,Wu, Meile,Lee, Jong-Ho IEEE 2017 IEEE electron device letters Vol.38 No.7

<P>This letter investigates the response of a wide detection range mercury ion sensor based on Si MOSFET having a floating-gate (FG) and a control-gate (CG) in horizontal direction. Single-walled carbon nanotubes (SWNTs) are formed between the FG and the CG by using an inkjet-printing method. The interaction between the mercury ions and SWNTs is studied by measuring transient current response (I-t). Conductance change is measured from 1 fM to similar to 10 mu M in saturated transient current region. The measured transient response shows that the drain current (I-D) is appreciably changed in pMOSFET sensor and almost not changed in nMOSFET sensor. By analyzing the conductance change of the pMOSFET sensor with the concentration of mercury ions, it is shown that the work-function of SWNTs increases due to hole doping and the I-D increases as a result.</P>

Research on Smart Home Interaction in Sleep Scenarios Based on User Needs

Jidong Liu,Yuanchen Wu,Meile Le 한국HCI학회 2024 한국HCI학회 학술대회 Vol.2024 No.1

This study explores the interaction methods of smart homes in sleep scenarios based on user needs, aiming to enhance user interaction experience with a user-centric interaction philosophy, and shift the development direction of smart homes from technologydriven to consumer needs-driven. The results indicate that in the sleep aid stage, Focused Interaction is the primary method, supported by Peripheral and Implicit Interactions. During the sleep stage, Implicit Interaction is the main method, supplemented by Peripheral and Focused Interactions. In the awakening stage, a foundation of Peripheral and Implicit Interactions with minimal Focused Interaction aligns more closely with consumer habits. This model can prevent the blind development of new interaction methods in smart homes within sleep scenarios, reducing the occurrence of unnecessary or unreasonable human-machine interactions.

An accurate and stable humidity sensing characteristic of Si FET-type humidity sensor with MoS₂ as a sensing layer by pulse measurement

Shin, Jongmin,Hong, Yoonki,Wu, Meile,Bae, Jong-Ho,Kwon, Hyuck-In,Park, Byung-Gook,Lee, Jong-Ho Elsevier 2018 Sensors and actuators. B Chemical Vol.258 No.-

<P><B>Abstract</B></P> <P>In this work, we demonstrate the pulse scheme to obtain stable humidity sensing characteristics in Si FET-type humidity sensor using MoS<SUB>2</SUB> film as a sensing layer. To investigate the reaction between H<SUB>2</SUB>O molecules and MoS<SUB>2</SUB> film, the transfer characteristics (<I>I</I> <SUB>D</SUB>-<I>V</I> <SUB>CG</SUB>) and transient drain current behaviors (<I>I</I> <SUB>D</SUB> <I>-t</I>) are measured in both <I>p</I>MOSFET and <I>n</I>MOSFET sensors by DC measurement. To verify the effect of the pulse scheme, the pulsed <I>I–V</I> (PIV) and the <I>I</I> <SUB>D</SUB> <I>-t</I> are measured as a parameter of relative humidity. The <I>I</I> <SUB>D</SUB> drift of the FET-type sensor is effectively eliminated by applying the pulse to the control-gate (CG) of the FET-type humidity sensor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB> as a sensing layer is formed on the FET type sensor. </LI> <LI> The humidity sensing characteristics are measured by DC and pulsed <I>I–V</I> method. </LI> <LI> The effectiveness of a pulse scheme to <I>I</I> <SUB>D</SUB> drift suppression has been demonstrated. </LI> <LI> Humidity characteristics with respect to the operation region of MOSFETs are investigated. </LI> </UL> </P>