Mr. Chintan P. Chavda Profile

Chintan P. Chavda

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Proceedings Article | 18 April 2022 Presentation + Paper

Design of a hybrid SET-TFET nanoscale IC for RF and microwave frequencies

Naheem Adesina, Fawwaz Hazzazi, Chintan Chavda, Georgios Veronis, Theda Daniels-Race, Jian Xu

Proceedings Volume 12045, 120450B (2022) https://doi.org/10.1117/12.2628189

KEYWORDS: Transistors, Analog filtering, Analog electronics, Linear filtering, Integrated circuits, Graphene, Integrated circuit design, Field effect transistors, Microwave radiation, Instrument modeling

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Device size has now reached the nanoscale range due to advancements in technology and scaling in the fields of very large-scale integration. The single-electron transistor (SET) is a promising solid-state device that can provide an extension for Moore’s law and is suitable for next-generation nanoelectronics design and application. Due to the Coulomb oscillation properties of the SET in addition to the high gain and ultra-low power consumption of the tunnel field effect transistor (TFET), the implementation of the hybrid SET/TFET will primarily benefit high density (nanoscale), low-power integrated circuits (ICs), and fast switching devices. In this study, we present a hybrid model of a graphene-based single electron transistor [1] with an n-type double-gate graphene nanoribbon TFET structure [2] utilized as an integrator. For simplicity, the TFET is used in the shorted gate configuration by connecting both the front and back gates. Following this, we design a fourth order analog low pass filter using the integrator circuit of SET/TFET. With the implementation in SPICE and Matlab, we analyze the transfer function of our proposed filter from its frequency characteristics (Bode plot). Our findings reveal significant roll-off and, as a consequence, increased filtering functions with low power consumption. This study adds to the realization and implementation of SET/TFET into applications where high frequency contributes to the reliability, performance, and low power required for nanoscale devices and designs.

Proceedings Article | 22 March 2021 Presentation + Paper

Gamma irradiation effect studies on monolayer molybdenum disulfide on metallic substrates

Chintan Chavda, Georgios Veronis, Ashok Srivastava, Erin Vaughan

Proceedings Volume 11590, 115900I (2021) https://doi.org/10.1117/12.2583155

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Molybdenum disulfide (MoS₂) is a two-dimensional material which has demonstrated semiconducting behavior [1]. Different kinds of irradiations create the defects in molybdenum disulfide (MoS₂) structure, different types of irradiations modulate the density of sulfur vacancies in MoS₂[1]. MoS₂based and other 2-D materials-based devices and sensors are used in harsh environments [1]. In [2] authors have demonstrated studies of gamma irradiation on mono layer graphene. To develop and fabricate the MoS₂-based devices and sensors, nanoelectronics instrumentation such as Transmission Electron Spectroscopy (TEM), Scanning Electron Microscopy (SEM), Raman Spectroscopy, X-ray Photo-Electron Diffraction (XPS) techniques are required for characterization of MoS₂. Moreover, these radiation techniques, have huge impacts on electronic and optical properties of MoS₂ [3]. So, it is important to study irradiation effects on the crystal structure and properties of MoS₂. In this work, Co-60 source was used for the irradiation, which has nominal irradiation dose 2.07 Gy/min (207 rad/Min) (±5%). We have irradiated gamma-rays on four samples of single-layer molybdenum disulfide over copper substrate. We exposed the irradiation dose of 1.0 kGy (100 krad), 1.75 kGy (175 krad), 2.65 kGy (265 krad) and 3.0 kGy (300 krad) of irradiations on sample number one, two, three and four respectively. Through the Raman Spectroscopy, we studied E¹_2g, A_1g peaks. A_1g peak is at 403.6 cm^-1 and E¹_2gpeak is at 384.7 cm^-1 in pristine MoS₂ Raman spectroscopy. Raman spectroscopy is nondestructive tool for characterization of S vacancies in MoS₂.

Proceedings Article | 22 April 2020 Presentation + Paper

Gamma irradiation effect studies on monolayer CVD grown graphene on metallic substrates

Chintan Chavda, Ashok Srivastava, Sangram Pradhan, Messaoud Bahoura

Proceedings Volume 11378, 113780E (2020) https://doi.org/10.1117/12.2556096

KEYWORDS: Graphene, Raman spectroscopy, Nickel, Chemical vapor deposition, Copper, Carbon, X-rays

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Graphene is a two-dimensional material and has demonstrated an exceptional electronic and photonic properties for unlimited applications including its use in extreme environments of the space. There are several known techniques of formation of graphene onto different types of substrates such as the substrate transfer process and direct deposition. In this work, we deposited monolayer graphene over copper and nickel substrates in NanoCVD-8G Graphene reactor using argon plasma, and methane as a carbon source and studied effects of gamma irradiation using Cobalt-60 source. Radiation effects on crystalline structure of graphene is examined using Raman Spectroscopy and X-ray Photo Electron Spectroscopy (XPS). In our experiment, we used irradiation dose from 1 kGy to 2.65 kGy for different samples of graphene over copper and nickel substrates. For the graphene grown on the nickel substrates, we exposed the irradiation dose of 1.0 kGy and 2.5 kGy on two samples, respectively. For the graphene grown on the copper substrates, we exposed 1.25 kGy, 1.75 kGy, and 2.65 kGy irradiation dose on three samples, respectively. We observed D-peak in graphene deposited over nickel and copper substrates caused by disordered structure of graphene after Co-60 exposure. After the Raman spectroscopy and XPS studies, same amount of irradiation was used for second set of irradiation dose experiment. XPS data on Co-60 exposed samples showed four peaks positioned at 284.8eV, 285.3eV, 286.0 eV and 288.5 eV for C-C, C-OH, C-O-C and COOH bonds, respectively. Analysis of the results shows weakening of C-C bonds and formation of C-OH, C-O-C and COOH bonds implying reduced electrical conductivity of graphene.

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