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Deepak Bharti

Bio: Deepak Bharti is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topic(s): Pentacene & Field-effect transistor. The author has an hindex of 9, co-authored 36 publication(s) receiving 237 citation(s). Previous affiliations of Deepak Bharti include Malaviya National Institute of Technology, Jaipur & Birla Institute of Technology and Science.
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Journal ArticleDOI
Ajay Kumar Mahato1, Deepak Bharti2, Ishan Varun1, Pulkit Saxena1  +2 moreInstitutions (2)
Abstract: In this report, we have demonstrated the optical non-volatile memory characteristics using CuPc OFET. The memory operation was comprehensively demonstrated with different programming conditions. It was found that the programming of CuPc OFET with an electric pulse at the gate terminal under UV-light photo-illumination compared to other programming conditions, could substantially increase the memory window due to massive charge trapping in the polymer electret layer, which causes shift in the device transfer characteristics from low-conduction state (“OFF state”, or logic 0) to high conduction state (“ON state”, or logic 1) at VGS = 0V. From device operation at −50V, a memory window of greater than 45V could be achieved by applying a programming voltage of +70 V at the gate terminal under UV-light photo-illumination. Moreover, it was completely erased by applying −100 V at the gate terminal in dark.

1 citations

Journal ArticleDOI
14 May 2021-Polymer
Abstract: The crucial role of molecular weight of the polymer dielectric in regulating the electrical performance and photo-response of TIPS-pentacene OFETs has been explored using poly(vinyl alcohol) (PVA) as the polymer dielectric layer. With increasing molecular weight of PVA, a degradation in the electrical and photo-response was observed. Atomic-force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD) studies revealed that with increase in PVA molecular weight, polarizability of PVA dielectric layer and thus strength of the OFET channel reduced due to decreased hydroxyl group concentration oriented perpendicular to the PVA-semiconductor interface. Further, due to rising surface roughness of underlying PVA film with its molecular weight, macroscopic irregularities and therefore trap density in the active layer grown over it also increases. Therefore, both of these molecular weight dependent factors influence overall device performance and photo-response of OFETs in a critical way.

1 citations

Journal ArticleDOI
Abstract: Physics-based two-dimensional numerical simulations are performed to analyze the device characteristics of tri-isopropylsilylethynyl (TIPS)-pentacene organic thin-film transistor (OTFT) fabricated using drop-casting technique. Further, using simulation technique enabling calibration this paper also presents the systematic study of the impact of active layer (TIPS-pentacene) thickness on device characteristics. The extracted parameters such as electric field intensity, current density, current On/Off ratio, and mobility exhibit variation with scaling down in active layer thickness from 500 to 100 nm. The study also revealed that Off current and On/Off current ratio (IOn/IOff) is highly dependent on the thickness of the semiconductor layer. Furthermore, the highest value of IOn/IOff is obtained at 100-nm thickness of TIPS-pentacene, which can be used for various fast-switching applications in digital circuits. Simulated results are not only reasonably matching with experimental results but also provide insight on charge transportation at the semiconductor-dielectric interface and in the bulk of TIPS-pentacene layer.

Proceedings ArticleDOI
Ishan Varun1, Deepak Bharti1, Ajay Kumar Mahato1, Vivek Raghuwanshi1  +1 moreInstitutions (1)
01 Apr 2020
Abstract: Flexible devices have been in focus for their applications in wearable electronics, displays, sensors, and memory. $\mathrm{PVP}/\mathrm{HfO}_{\mathrm{x}}$ based hybrid resistive random access memory devices were demonstrated on flexible PET substrates to study their resistive switching characteristics and memory application. These RRAM devices exhibited decent repeatability of more than 100 cycles with excellent $I_{\mathrm{o}\mathrm{n}}/I_{\mathrm{off}}$ of ~106 at 0.2 V as read voltage. With retention time of more than 6000 s and reliable switching operation, the fabricated devices have potential to be embedded in flexible electronic applications. Moreover, conduction mechanism in devices was found to be ohmic at lower voltage levels in high resistance state (HRS) and space charge limited conduction at higher voltage levels, occurring mainly due to traps sites available in PVP and $\mathrm{HfO}_{\mathrm{x}}$ . The AFM image confirms the presence of pinholes at PVP surface which will eventually assist in filament formation.

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Book ChapterDOI
01 Jan 2022
Abstract: Flexible electronics offers advantages over conventional electronics on this aspect with the possibility of fabrication on unconventional and biodegradable substrates. Organic field-effect transistors (OFETs) receive significant attention because of their potential use in flexible electronics, specifically for circuit and sensing applications. These devices can be used as a building block for applications in electronic skin (E-skin), health monitoring, and biomimetic applications due to flexibility or stretchability. However, during the operation, these devices are encountered with various electrical, mechanical, and thermal stimulations. Thus, for reliable operation in practical applications, OFETs must be operationally stable. In this chapter, firstly, the area of flexible electronics is introduced and the historical perspective along with various potential applications are summarized. The structure and operation of OFETs are discussed along with some crucial aspects. OFETs on various flexible substrates including plastic and paper are discussed. High performing OFET devices fabricated on unconventional substrates such as paper can pave the way toward biodegradable or green electronics. In addition, these devices have shown the potential to be used for real-time health monitoring and e-skin applications. OFETs with biodegradable gelatin dielectric had shown the possibility to be used as a breath rate analyzer. These devices will eventually be useful for low-cost self-health monitoring systems.

Journal ArticleDOI
Abstract: The 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) is a promisor p-type solution-processable molecular semiconductor whose electrical properties are highly dependent on its morphology. Unfortunately, there is a great difficulty in controlling the TIPS-pentacene crystallization because it is extremely affected by many factors, as the deposition method, the solvent type, and others. Here, we studied thin-films of TIPS-pentacene blending with poly(3-hexylthiophene-2,5-diyl) (P3HT:TP blend) in different ratios, aiming to improve TIPS-pentacene morphology. The surface of each film was very dependent on the deposition method and the blend morphology exhibited a high variation with the ratio. The different crystallinities achieved lead to dramatic changes in the charge carrier transport properties throughout the film. The impedance spectroscopy indicated that the small addition of P3HT in the TIPS-pentacene greatly improves its conductivity, however, the TIPS-pentacene forms crystallite agglomerates that did not percolate, prevailing the P3HT conductivities.

Journal ArticleDOI
Abstract: Interest in the use of organic electronic devices in radiation sensing applications has grown in recent years. The numerous device configurations (e.g., diodes, thin film transistors) and potential for improved tissue equivalence compared to their silicon-based analogues make them attractive candidates for various radiation dosimetry measurements. In this work, a variation of the organic thin film transistor (OTFT) is studied, in which a polymer electret is added. An OTFT electret design can be used in either a wired or wireless configuration for in vivo dosimetry with the possibility of real-time detection. The linearity, reproducibility, and dependence on energy of these devices were measured through exposure to 100 kVp photons from an orthovoltage treatment unit (Xstrahl 300) and 6 MV photons from a Varian TrueBeam medical linear accelerator. Prior to irradiation, all transistors were programmed with a −80 V bias applied to the Gate electrode (Vg) for 3 s. In the wireless configuration, after each delivered dose, the transfer characteristic was scanned to readout the amount of erased charges by monitoring the drain current change. When the programmed charge was sufficiently depleted by radiation, transistors were reprogrammed for repeated use. The real-time readout in a wired configuration was performed by measuring the drain current with Vg = −15 V; Vd = −15 V. The 6 MV photon beam was turned on and off at different dose rates of 600, 400, 300, 200, and 60 cGy/min to quantify the sensitivity of the device to changes in dose rate. The wireless transistors showed a linear increase in current with increasing dose. The sensitivities for different energies were 60 ± 5 nA/Gy at 6 MV at a dose rate of 600 cGy/min and 80 ± 10 nA/Gy at 100 kVp at a dose rate of 200 cGy/min. The sensitivity of detectors tested in a wired configuration at Vd = −15 V; Vg = −15 V was 8.1 nA/s at a dose rate of 600 cGy/min. The principle of pentacene OTFTs with polymer electret as radiation detectors was demonstrated. Devices had excellent linearity, reproducibility, and were able to be reprogrammed for multiple uses as wireless detectors. The wired transistors demonstrated an effective response as real-time detectors.

Journal ArticleDOI
Anil Kumar Chauhan1, Anil Kumar Chauhan2, P. Jha1, P. Jha2  +3 moreInstitutions (2)
Abstract: The low cost of organic starting materials and ease of their fabrication processes have propelled the development of various organic devices and have also generated a considerable research interest in the scientific community. These devices make use of organic materials in the form of dielectrics, conductive polymers, or small organic molecules deposited mainly on flexible substrates to bring about the advantages of stretchability and moldability. Focussed and dedicated R&D activities conducted in this field during the last few decades have led to the development of novel and efficient organic devices that hold tremendous promise of a highly optimistic future. This review provides an insight into the area of organic devices with a particular emphasis on organic light emitting diodes, organic field effect transistors, organic solar cells, and organic thermoelectric devices. It presents a comprehensive survey that includes important milestones, fabrication processes, and applications of these devices. New materials and processes that enabled the recent technological advancements have been highlighted and discussed for each device category. The current challenges of the field are also discussed with a glance at the future prospects and directions for this emerging field.

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Author's H-index: 9

No. of papers from the Author in previous years