Browsing by Author "Utkarsh Pandey"

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Application of a microwave synthesized ultra-smooth a-C thin film for the reduction of dielectric/semiconductor interface trap states of anoxide thin film transistor
(Royal Society of Chemistry, 2022) Nila Pal; Baishali Thakurta; Rajarshi Chakraborty; Utkarsh Pandey; Vishwas Acharya; Sajal Biring; Monalisa Pal; Bhola N. Pal
In high-κ dielectric-based thin-film transistors (TFTs), tailoring the surface of the gate dielectric layer is a crucial issue for the improvement of the device performance. Herein, a simple solution-processed ultra-smooth amorphous-carbon (a-C) film is applied as a surface modification layer on the top of the high-κ ion-conducting Li-Al2O3 dielectric of a bottom gated SnO2 TFT. The a-C film minimizes the surface roughness of the gate dielectric and forms a strong coordination bond between the doped nitrogen of the a-C film and tin (Sn) of the upper lying SnO2 semiconducting channel, which lowers the gate leakage current, carrier scattering and trap state density at the dielectric/semiconductor interface successfully. As a consequence, the TFT with an a-C interface shows an improvement in the carrier mobility by 6.7 times with a higher ON/OFF ratio and a lower subthreshold swing (SS) by 3.8 times. An optimized device with an a-C gate interface shows a saturation carrier mobility, ON/OFF ratio and SS value of 21.1 cm2 V−1 s−1, 7.0 × 104, and 147 mV dec−1, respectively. Moreover, a significant improvement in the cycling electrical stability has been observed which is an outcome of a reduced trap state of an a-C modified TFT. © 2022 The Royal Society of Chemistry.
Enhancement in photo-response of CuZnS nanocrystals-based photodetector using asymmetric work function electrodes
(Elsevier B.V., 2024) Sandeep Dahiya; Sobhan Hazra; Utkarsh Pandey; Subarna Pramanik; Pardeep Dahiya; Satya Veer Singh; Nikita Kumari; Bhola Nath Pal
In this study, an efficient visible light photodetector has been fabricated by using heavy metal-free CuZnS Nanocrystals with average particle size of 13 ± 1 nm and has been synthesized by a microwave (MW) assisted synthesis technique. The optical band gap of this nanocrytstal is ∼1.7 eV and has an absorbance spectra ranging from 300 to700 nm. This low bandgap nanocrystals has been used to fabricate a photoconductor device with a CuZnS/ZnO bilayer structure. Besides, the device performance has been enhanced by using an asymmetric work-function lateral electrodes. The work-function difference between the electrodes gives a driven voltage between the electrodes, which allows faster collection of charge carriers from the device. As a consequence, a significant photocurrent is generated by the device even without any external bias. The self-biased (at 0 V) external quantum efficiency (EQE) of this device is ∼ 4 % (at 430 nm) whereas this value reaches ∼ 20 % under 2 V external bias. The device possesses the responsivity (Rλ) and detectivity (D) of 8.8 A/W and 3.8 × 1012 Jones at 320 nm respectively under 2 V external bias. © 2024 Elsevier B.V.
Enhancement of Photosensitivity in a Low-Operating-Voltage Organic-Inorganic Bilayer Thin-Film Transistor by Using an Asymmetric Source-Drain Electrode
(American Chemical Society, 2024) Pijush Kanti Aich; Zewdneh Genene; Utkarsh Pandey; Akhilesh Kumar Yadav; Ergang Wang; Bhola Nath Pal
A solution-processed inorganic-organic bilayer semiconductor channel-based red-light-sensitive thin-film transistor (TFT) has been fabricated by using an ion-conducting Li-Al2O3 gate dielectric that limits the operating voltage of this TFT within 2 V. In this device, a high-electron-mobility inorganic metal-oxide semiconductor (SnO2) was used as the primary charge transport layer, whereas the polymer (PIDT-2TPD) was used as the photoactive layer. To improve its red photosensitivity, an asymmetric work function source-drain (S-D) electrode was fabricated, which allows a selective carrier (electron or hole) injection and collection from the channel. Besides, the work function difference of this asymmetric S-D electrode generates a potential difference between electrodes that allows faster charge collection from the channel. As a consequence, the photosensitivity of this asymmetric S-D electrode TFT enhanced by ∼103 times under red illumination with respect to the symmetric S-D electrode TFT and the detectivity of this device increased ∼20 times. In addition, the on/off ratio of asymmetric TFT is 4 times greater than that of the symmetric TFT, whereas the subthreshold swing (SS) of this TFT is reduced from 200 to 144 mV/decade. © 2024 American Chemical Society.
Role of ultrathin Ti3C2Tx MXene layer for developing solution-processed high-performance low voltage metal oxide transistors
(American Institute of Physics, 2024) Ankita Rawat; Utkarsh Pandey; Ritesh Kumar Chourasia; Gaurav Rajput; Bhola Nath Pal; Nitesh K. Chourasia; Pawan Kumar Kulriya
Metal oxide transistors have garnered substantial attention for their potential in low-power electronics, yet challenges remain in achieving both high performance and low operating voltages through solution-based fabrication methods. Optimizing interfacial engineering at the dielectric/semiconductor interface is of utmost importance in the fabrication of high-performance thin film transistors (TFTs). In the present article, a bilayer Ti3C2Tx-MXene/SnO2-semiconductor (Tx stands for surface termination) configuration is used to fabricate a high-performance n-type thin film transistor by using an ion-conducting Li-Al2O3 gate dielectric on a p+-Si substrate, where electrical charges are formed and modulated at the Li-Al2O3/SnO2 interface, and Ti3C2Tx-MXene nanosheets serve as the primary electrical charge channel due to their long lateral size and high mobility. A comparative characterization of two distinct TFTs is conducted, one featuring Ti3C2Tx MXene and SnO2 semiconductor layer and the other with SnO2 only. Notably, the TFT with the Ti3C2Tx MXene layer has shown a significant boost in the carrier mobility (10.6 cm2/V s), leading to remarkable improvements in the on/off ratio (1.3 × 105) and subthreshold swing (194 mV/decade), whereas the SnO2 TFT without the Ti3C2Tx MXene layer shows a mobility of 1.17 cm2/V s with 8.1 × 102 on/off ratio and 387 mV/decade subthreshold swing. This investigation provides a possible way toward the development of high-performance, low-voltage TFT fabrication with the MXene/semiconductor combination. © 2024 Author(s).