sridhar chandrasekaran
@citchennai.edu.in
Assistant Professor, Department of ECE
Chennai Institute of Technology
RESEARCH INTERESTS
Emerging Memories, Nanoscale devices, Resistive switching memories, Semiconductor devices, Smart Process development, Sustainable manufacturing process, Semiconductor process
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Natesan Thirumalaivasan, Kuppusamy Kanagaraj, Kamaraj Logesh, Sridhar Chandrasekaran, Sandeep Kumar, Raghunandhakumar Subramanian, Nangan Senthilkumar, Ashok Kumar, V. Jagadeesha Angadi, and Abdullah A. Al-Kahtani
Elsevier BV
Nadhiya Dakshina Murthy, Kala Arumugam, Thirunavukkarasu Palaniyandi, Sridhar Chandrasekaran, and Karnan Chandran
Springer Science and Business Media LLC
S. Nishanth, S. Nivithaa, C. Sridhar, K.S. Nagaraja, and C. Karnan
Elsevier BV
Chia-Cheng Hsu, Saransh Shrivastava, Sparsh Pratik, Sridhar Chandrasekaran, and Tseung-Yuen Tseng
Institute of Electrical and Electronics Engineers (IEEE)
Om Kumar Prasad, Sridhar Chandrasekaran, Chin-Han Chung, Kow-Ming Chang, and Firman Mangasa Simanjuntak
AIP Publishing
The effect of annealing on the switching characteristics of memristor devices cannot be overlooked because the thermal process can exhibit both positive and negative effects on the performance of the devices. We investigated the switching behavior of TaOx-based memristors (electrochemical metallization cell type, ECM) that were Ar-ambient annealed under two conditions, with and without the active electrode. We found a high concentration of metal species in the TaOx films, even in the device where the TaOx was annealed without the active top electrode. This indicates that the properties of the annealed films encourage the diffusion of metal species in the oxide. We suggest that the increase in non-lattice oxygen (by 4.1%, indicating a higher concentration of Vo defects) after the annealing process plays a role in this phenomenon. In addition, the concentration of metal species that exist prior to the switching activation as well as the structure of the conducting bridge determines the switching stability of the devices. The device that annealed before top electrode deposition shows the worst stability; conversely, the device that annealed after top electrode deposition has the best coefficient of variation of the LRS and HRS which is 4.69% and 78.8%, respectively. Electrical and materials analyses were conducted to understand this phenomenon. This study provides insight into the compatibility of ECM in CMOS post-processing.
Sridhar Chandrasekaran, Arunkumar Jayakumar, and Rajkumar Velu
MDPI AG
Printable electronics is emerging as one of the fast-growing engineering fields with a higher degree of customization and reliability. Ironically, sustainable printing technology is essential because of the minimal waste to the environment. To move forward, we need to harness the fabrication technology with the potential to support traditional process. In this review, we have systematically discussed in detail the various manufacturing materials and processing technologies. The selection criteria for the assessment are conducted systematically on the manuscript published in the last 10 years (2012–2022) in peer-reviewed journals. We have discussed the various kinds of printable ink which are used for fabrication based on nanoparticles, nanosheets, nanowires, molecular formulation, and resin. The printing methods and technologies used for printing for each technology are also reviewed in detail. Despite the major development in printing technology some critical challenges needed to be addressed and critically assessed. One such challenge is the coffee ring effect, the possible methods to reduce the effect on modulating the ink environmental condition are also indicated. Finally, a summary of printable electronics for various applications across the diverse industrial manufacturing sector is presented.
Sailesh Rajasekaran, Firman Mangasa Simanjuntak, Sridhar Chandrasekaran, Debashis Panda, Aftab Saleem, and Tseung-Yuen Tseng
Institute of Electrical and Electronics Engineers (IEEE)
In this letter, Ta<sub>2</sub>O<sub>5</sub>/WO<sub>3</sub> double-layer wearable memristor synapse has excellent recognition accuracy (97%) for just 12 epochs compared to the single-layer device (83%). The insertion of an ultra-thin WO<sub>3</sub> layer modulates the oxygen vacancy distribution in Ta<sub>2</sub>O<sub>5</sub> and induces digital-to-analog switching behavior. Excellent AC endurance of (>10<sup>9</sup> cycles) under 2 mm extreme bending, a rapid speed (25 ns), reliable bending endurance for 10<sup>4</sup> cycles with 4 mm bending, stable retention (>10<sup>6</sup> s) up to 200°C, and water-resistant behavior are achieved. The potentiation, and depression having outstanding nonlinearity (0.64) is obtained. The Ta<sub>2</sub>O<sub>5</sub>/WO<sub>3</sub> design is a promising candidate for wearable neuromorphic applications due to its wearability, flexibility, lightweight, low cost and environmental friendly fabrication.
Firman Mangasa Simanjuntak, Sridhar Chandrasekaran, Debashis Panda, Sailesh Rajasekaran, Cut Rullyani, Govindasamy Madhaiyan, Themistoklis Prodromakis, and Tseung-Yuen Tseng
AIP Publishing
An excessive unintentional out-diffused In atom into the switching layer is a potential threat to the switching stability of memristor devices having indium tin oxide (ITO) as the electrode. We suggest that the physical factor (bombardment of Ar ions and bombardment-induced localized heat during ZnO deposition) and chemical factor (bonding dissociation energy, point defects, and bond length of atoms) are responsible for promoting the out-diffusion. The In atom acts as dopant in the ZnO lattice that degenerates the ZnO insulative behavior. Furthermore, the In ions take part in the conduction mechanism where they may compete with other mobile species to form and rupture the filament, and hence, deteriorate the switching performance. We propose a facile UV/O3 (UVO) treatment to mitigate such damaging effects. The device fabricated on the UVO-treated ITO substrate exhibits significant switching parameter improvement than that of the device manufactured on untreated ITO. This work delivers an insight into the damaging effect of out-diffusion and auto-doping processes on the reliability of memristor devices.
Aftab Saleem, Firman Mangasa Simanjuntak, Sridhar Chandrasekaran, Sailesh Rajasekaran, Tseung-Yuen Tseng, and Themis Prodromakis
AIP Publishing
An oxidizable metal diffusion barrier inserted between the active metal electrode and the switching layer decreases the electroforming voltage and enhances the switching stability and synaptic performances in TaOx-based conducting bridge memristor devices. The TiW barrier layer avoids an excessive metal ion diffusion into the switching layer, while the TiWOx interfacial layer is formed between the barrier and the switching layer. It modulates the oxygen vacancy distribution at the top interface and contributes to the formation and rupture of the metal ion-oxygen vacancy hybrid conducting bridge. We observe that the device that relies upon non-hybrid (metal ions only) conducting bridge suffers from poor analogous performance. Meanwhile, the device made with the barrier layer is capable of providing 2-bit memory and robust 50 stable epochs. TaOx also acts as resistance for suppressing and a thermal enhancement layer, which helps to minimize overshooting current. The enhanced analog device with high linear weight update shows multilevel cell characteristics and stable 50 epochs. To validate the neuromorphic characteristic of the devices, a simulated neural network of 100 synapses is used to recognize 10 × 10 pixel images.
Firman Mangasa Simanjuntak, Debashis Panda, Sridhar Chandrasekaran, Rakesh Aluguri, Chun-Chieh Lin, and Tseung-Yuen Tseng
Springer Science and Business Media LLC
V. Sathya, Kirankumar Manivannan, V. Vani, and Sridhar Chandrasekaran
Springer International Publishing
Sailesh Rajasekaran, Firman Mangasa Simanjuntak, Debashis Panda, Sridhar Chandrasekaran, Rakesh Aluguri, Aftab Saleem, and Tseung-Yuen Tseng
American Chemical Society (ACS)
Memristor devices that can operate at high speed with high density and nonvolatile capabilities have great potential for the development of high data storage and robust wearable devices. However, i...
Lung-Yu Chang, Firman Mangasa Simanjuntak, Chun-Ling Hsu, Sridhar Chandrasekaran, and Tseung-Yuen Tseng
AIP Publishing
Oxidation of TiN is a diffusion-limited process due to the high stability of the TiN metallic state at the TiN/TiO2 junction. Hence, the TiN/TiO2/TiN device being the inability to form a suitable interfacial layer results in the exhibition of abrupt current (conductance) rise and fall during the set (potentiation) and reset (depression) processes, respectively. Interfacial engineering by depositing Ti film served as the oxygen gettering material on top of the TiO2 layer induces a spontaneous reaction to form a TiOx interfacial layer (due to the low Gibbs free energy of suboxide formation). Such an interface layer acts as an oxygen reservoir that promotes gradual oxidation and reduction during the set and reset processes. Consequently, an excellent analog behavior having a 2-bit per cell and robust epoch training can be achieved. However, a thick interfacial layer may degrade the switching behavior of the device due to the high internal resistance. This work suggests that interfacial engineering could be considered in designing high-performance analog memristor devices.
Firman Mangasa Simanjuntak, Takeo Ohno, Sridhar Chandrasekaran, Tseung-Yuen Tseng, and Seiji Samukawa
IOP Publishing
Surface oxidation employing neutral oxygen irradiation significantly improves the switching and synaptic performance of ZnO-based transparent memristor devices. The endurance of the as-irradiated device is increased by 100 times, and the operating current can be lowered by 10 times as compared with the as-deposited device. Moreover, the performance-enhanced device has an excellent analog behavior that can exhibit 3 bits per cell nonvolatile multistate characteristics and perform 15 stable epochs of synaptic operations with highly linear weight updates. A simulated artificial neural network comprising 1600 synapses confirms the superiority of the enhanced device in processing a 40 × 40 pixels grayscale image. The irradiation effectively decreases the concentration of oxygen vacancy donor defects and promotes oxygen interstitial acceptor defects on the surface of the ZnO films, which consequently modulate the redox process during rupture and rejuvenation of the filament. This work not only proposes the potential of ZnO-based memristor devices for high-density invisible data storage and in-memory computing application but also offers valuable insight in designing high-performance memristor devices, regardless of the oxide system used, by taking advantage of our neutral oxygen irradiation technique.
Debashis Panda, Firman M. Simanjuntak, Sridhar Chandrasekaran, Bhaskar Pattanayak, Pragya Singh, and Tseung-Yuen Tseng
Institute of Electrical and Electronics Engineers (IEEE)
The effect of the TiW barrier layer on the switching properties of Ga-doped ZnO (GZO) nanorods based on Electrochemical Metallization Memory is investigated. Vertically well-aligned and uniform GZO nanorods having a diameter of approximately 35 nm are hydrothermally grown on a seeding layer of ZnO deposited on indium tin oxide (ITO) coated glass substrate, to fabricate Cu/TiW/nanorods/ITO/Glass devices. The remarkable enhancement in the memory window (on/off ratio) is achieved in the 5 nm TiW barrier layer embedded device. This device exhibits endurance of more than 103 cycles and a large memory window of ∼103. The conduction mechanism at different current regions is studied, and it is found that Schottky emission is dominated in the low field region. The TiW barrier layer helps to retain the Cu ions and control the Cu ions diffusion, hence control the filament growth into the resistive layer, confirmed from the X-ray photoelectron spectroscopy (XPS) analysis. This device is suitable for the future low power non-volatile memory devices.
Pei-Yu Jung, Debashis Panda, Sridhar Chandrasekaran, Sailesh Rajasekaran, and Tseung-Yuen Tseng
Institute of Electrical and Electronics Engineers (IEEE)
To move towards a new generation powerful computing system, brain-inspired neuromorphic computing is expected to transform the architecture of the conventional computer, where memristors are considered to be potential solutions for synapses part. We propose and demonstrate a novel approach to achieve remarkable improvement of analog switching linearity in TaN/Ta/TaO<sub>x</sub>/Al<sub>2</sub>O<sub>3</sub>/Pt/Si memristors by varying Al<sub>2</sub>O<sub>3</sub> layer thickness. Presence of the Al<sub>2</sub>O<sub>3</sub> layer is confirmed from the Auger Electron Spectroscopy study. Good analog switching ratio of about <inline-formula> <tex-math notation="LaTeX">$100\\times $ </tex-math></inline-formula> and superior switching uniformity are observed for the 1 nm Al<sub>2</sub>O<sub>3</sub> based device. Multilevel capability of the memristive devices is also explored for prospective use as a synapse. More than 10<sup>4</sup> and <inline-formula> <tex-math notation="LaTeX">$4\\times 10^{4}$ </tex-math></inline-formula> cycles nondegradable dc and ac endurances, respectively, alongwith 10<sup>4</sup> second retention are achieved for the optimized device. Improved linearities of 2.41 and −2.77 for potentiation and depression, respectively are obtained for such 1 nm Al<sub>2</sub>O<sub>3</sub>-based devices. The property of gradual resistance changed by pulse amplitudes confirms that the TaO<sub>x</sub> memristors can be potentially used as an electronic synapse.
Sridhar Chandrasekaran, Firman Mangasa Simanjuntak, Debashis Panda, and Tseung-Yuen Tseng
Institute of Electrical and Electronics Engineers (IEEE)
The synaptic plasticity of indium tin oxide (ITO)/ZnO/ITO highly transparent (more than 88%) analog switching resistive memory device is investigated. Highly stable analog switching behavior for more than 2500 cycles with a good memory window of approximately two orders makes it suitable for synapse application. The synaptic response is investigated by applying identical electrical pulses. The potentiation and depression of the device used the conventional identical single-pulse scheme to perform high nonlinearity (0.83) and decaying training epochs. However, the linearity and the training epochs are improved to 0.44 by implementing the identical double-pulse scheme. The proposed double-pulse scheme offers a broad dynamic range (200) having 320 conductance states. This invisible structure and double-pulse scheme can be highly suitable for the neuromorphic computing devices.
Sridhar Chandrasekaran, Firman Mangasa Simanjuntak, R Saminathan, Debashis Panda, and Tseung-Yuen Tseng
IOP Publishing
Artificial synapse having good linearity is crucial to achieve an efficient learning process in 19 neuromorphic computing. It is found that the synaptic linearity can be enhanced by engineering 20 the doping region across the switching layer. The nonlinearity of potentiation and depression of 21 the pure device is 36% and 91%, respectively; meanwhile, the nonlinearity after doping can be 22 suppressed to be 22% (potentiation) and 60% (depression). Henceforth, the learning accuracy 23 of the doped device is 91% with only 13 iterations; meanwhile, the pure device is 78%. Detailed 24 conduction mechanism to understand this phenomenon is proposed.
Firman Mangasa Simanjuntak, Sridhar Chandrasekaran, Chun-Chieh Lin, and Tseung-Yuen Tseng
AIP Publishing
Hydrogen peroxide treatment induces the phase transformation of hexagonal ZnO to cubic ZnO2 on the surface of the ZnO switching memory film; this oxidation process effectively reduces the concentration of n-type donor defects (oxygen vacancies and zinc interstitials) in the switching film. The chemically oxidized ZnO2 layer not only lowers the operation current of the device but also can serve as an oxygen “bank” to improve the endurance of the memristor. The oxidation reaction of peroxide treatment can be easily controlled to achieve an analog behavior with good switching uniformity. The analog memristor device is able to perform two-bit per cell and synaptic operations. Based on the experimental synaptic data, an image processing of 7 × 9 pixels using a simulated artificial neural network comprises 63 synapses is evaluated to mimic the visual cortex function of the brain.Hydrogen peroxide treatment induces the phase transformation of hexagonal ZnO to cubic ZnO2 on the surface of the ZnO switching memory film; this oxidation process effectively reduces the concentration of n-type donor defects (oxygen vacancies and zinc interstitials) in the switching film. The chemically oxidized ZnO2 layer not only lowers the operation current of the device but also can serve as an oxygen “bank” to improve the endurance of the memristor. The oxidation reaction of peroxide treatment can be easily controlled to achieve an analog behavior with good switching uniformity. The analog memristor device is able to perform two-bit per cell and synaptic operations. Based on the experimental synaptic data, an image processing of 7 × 9 pixels using a simulated artificial neural network comprises 63 synapses is evaluated to mimic the visual cortex function of the brain.
F M Simanjuntak, S Chandrasekaran, F Gapsari, and T Y Tseng
IOP Publishing
This paper reports the resistive switching and synaptic capability of AZO/ZnO/ITO transparent and flexiblevalence change memory device structure. The device performs stable endurance for more than 50 cycles with sufficient ON/OFF ratio of one order of magnitude; no intermediate state (data error) is observed during the cycle-to-cycle test. By exploiting the analog switching characteristic of the device and employing identical pulses to the top electrode, a synaptic behavior can be achieved. A low programming voltage of 1.5V is used to modulate the conductance during potentiation and depression which indicate that the device is a logic-compatible. The conduction mechanism during the switching processand the device performance is discussed.
Sridhar Chandrasekaran, Firman Mangasa Simanjuntak, Rakesh Aluguri, and Tseung-Yuen Tseng
Elsevier BV
Sridhar Chandrasekaran, Firman Mangasa Simanjuntak, and Tseung-Yuen Tseng
IOP Publishing
The effects of varying the thickness of the TiW barrier layer on the switching characteristics of a ZrO2-based electrochemical metallization memory (ECM) device were investigated. The thickness of the TiW barrier layer may alter the resistive switching characteristics of Cu/TiW/ZrO2/TiN ECM devices. Devices made without a TiW barrier layer exhibit unstable cycle-to-cycle behavior. The switching stability of ZrO2 devices improves after inserting a TiW layer. However, the insertion of TiW beyond critical thickness leads to switching degradation. We suggest that an appropriate TiW barrier layer thickness is necessary for achieving good switching performance.
Firman Mangasa Simanjuntak, Sridhar Chandrasekaran, Chun-Chieh Lin, and Tseung-Yuen Tseng
Springer Science and Business Media LLC
Firman Mangasa Simanjuntak, Pragya Singh, Sridhar Chandrasekaran, Franky Juanda Lumbantoruan, Chih-Chieh Yang, Chu-Jie Huang, Chun-Chieh Lin, and Tseung-Yuen Tseng
IOP Publishing
An engineering nanorod array in a ZnO-based electrochemical metallization device for nonvolatile memory applications was investigated. A hydrothermally synthesized nanorod layer was inserted into a Cu/ZnO/ITO device structure. Another device was fabricated without nanorods for comparison, and this device demonstrated a diode-like behavior with no switching behavior at a low current compliance (CC). The switching became clear only when the CC was increased to 75 mA. The insertion of a nanorods layer induced switching characteristics at a low operation current and improve the endurance and retention performances. The morphology of the nanorods may control the switching characteristics. A forming-free electrochemical metallization memory device having long switching cycles (>104 cycles) with a sufficient memory window (103 times) for data storage application, good switching stability and sufficient retention was successfully fabricated by adjusting the morphology and defect concentration of the inserted nanorod layer. The nanorod layer not only contributed to inducing resistive switching characteristics but also acted as both a switching layer and a cation diffusion control layer.
Sridhar Chandrasekaran, Firman Mangasa Simanjuntak, Tsung-Ling Tsai, Chun-An Lin, and Tseung-Yuen Tseng
AIP Publishing
In this study, metal diffusion barrier-dependent switching polarity in ZrO2-based conducting-bridge random access memory was investigated. The device without the barrier layer (BL) exhibited nonpolar switching characteristics. However, inserting TiW BL resulted in positive reset failure. This phenomenon depends on the size and shape of the conducting bridge and also on the defects that contribute to the formation and rupture of the bridge. Consequently, the properties of the conducting bridge govern the device switching performance. Cu- and oxygen vacancy-based conducting bridge during N-Set for a device with and without the BL was proposed. The effect of the insertion of BL on the switching performance was also discussed. The absence of BL resulted in switching instability and poor nonvolatility. By contrast, a device with BL exhibited enhanced uniformity and nonvolatility, and the retention was more than 105 s at 200 °C.