Browsing by Author "Adachi, Michael M."

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2D MoSe2 Geometrically Asymmetric Schottky Photodiodes
(Wiley, 2024-09) Ghanbari, Hamidreza; Abnavi, Amin; Ahmadi, Ribwar; Reza Mohammadzadeh, Mohammad; Fawzy, Mirette; Hasani, Amirhossein; Adachi, Michael M.
Optoelectronic devices based on geometrically asymmetric architecture have recently attracted attention due to their high performance as photodetectors and simple fabrication process. Herein, a p-type 2D MoSe2 photodetector based on geometrically asymmetric contacts is reported for the first time. The device exhibits a high current rectification ratio of ≈104 and a large self-powered photovoltage responsivity of ≈4.38 × 107 V W−1, as well as a maximum photocurrent responsivity of ≈430 mA W−1 along with a response time of ≈2.3 ms under 470 nm wavelength at 3 V bias voltage. The photocurrent responsivity is further enhanced to an ultrahigh responsivity of ≈1615 mA W−1 by applying a gate bias voltage due to the electrostatic modulation of carrier concentration in the MoSe2 channel. The simple fabrication process of the geometrically asymmetric MoSe2 diodes along with their high photodetection and diode rectifying performance make them excellent candidates for electronic and optoelectronic applications.
A Photovoltaic Self-Powered Volatile Organic Compounds Sensor Based on Asymmetric Geometry 2D MoS2 Diodes
(The Electrochemical Society, 2024-09) Fawzy, Mirette; Reza Mohammadzadeh, Mohammad; Abnavi, Amin; De Silva, Thushani; Ahmadi, Ribwar; Ghanbari, Hamidreza; Kabir, Fahmid; Kavanagh, Karen L.; Hasani, Amirhossein; Adachi, Michael M.
Transition metal dichalcogenides have gained considerable interest for vapour sensing applications due to their large surface-to-volume ratio and high sensitivity. Herein, we demonstrate a new self-powered volatile organic compounds (VOC) sensor based on asymmetric geometry multi-layer molybdenum disulfide (MoS2) diode. The asymmetric contact geometry of the MoS2 diode induces an internal built-in electric field resulting in self-powering via a photovoltaic response. While illuminated by UV-light, the sensor exhibited a high responsivity of ∼60% with a relatively fast response time of ∼10 sec to 200 ppm of acetone, without an external bias voltage. The MoS2 VOC diode sensor is a promising candidate for self-powered, fast, portable, and highly sensitive VOC sensor applications.
Enhanced Sensitivity in Photovoltaic 2D MoS2/Te Heterojunction VOC Sensors
(Wiley, 2024-07) Reza Mohammadzadeh, Mohammad; Hasani, Amirhossein; Hussain, Tanveer; Ghanbari, Hamidreza; Fawzy, Mirette; Abnavi, Amin; Ahmadi, Ribwar; Kabir, Fahmid; De Silba, Thushani; Rajapakse, R. K. N. D.; Adachi, Michael M.
Volatile organic compound (VOC) sensors have a broad range of applications including healthcare monitoring, product quality control, and air quality management. However, many such applications are demanding, requiring sensors with high sensitivity and selectivity. 2D materials are extensively used in many VOC sensing devices due to their large surface-to-volume ratio and fascinating electronic properties. These properties, along with their exceptional flexibility, low power consumption, room-temperature operation, chemical functionalization potential, and defect engineering capabilities, make 2D materials ideal for high-performance VOC sensing. Here, a 2D MoS2/Te heterojunction is reported that significantly improves the VOC detection compared to MoS2 and Te sensors on their own. Density functional theory (DFT) analysis shows that the MoS2/Te heterojunction significantly enhances the adsorption energy and therefore sensing sensitivity of the sensor. The sensor response, which denotes the percentage change in the sensor's conductance upon VOC exposure, is further enhanced under photo-illumination and zero-bias conditions to values up to ≈7000% when exposed to butanone. The MoS2/Te heterojunction is therefore a promising device architecture for portable and wearable sensing applications.