Faculty Publications
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Publications by NITK Faculty
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Item Dual band operation using metamaterial structure for Radio Frequency Identification (RFID) system(IEEE Computer Society help@computer.org, 2014) Saha, R.; Bhattacharjee, S.; Bhunia, C.T.; Maity, S.The important functions of Radio Frequency Identification (RFID) technology are radiation and detection. So efficient antenna design and fabrication is the unique solution which perform a very crucial role for many applications. The reader and tag intense are component of the RFID system. In this paper designed has done on RFID antenna for tag and reader application, which also includes the different types of antenna (UHF application, wideband, multiband antenna) and the general consideration for design, them which are currently used for tag and reader application. In this paper we proposed a rectangular patch antenna and then designed a metamaterial structure on the patch to improve the antenna performance. © 2014 IEEE.Item A Time Series Forecasting Approach to Minimize Cold Start Time in Cloud-Serverless Platform(Institute of Electrical and Electronics Engineers Inc., 2022) Jegannathan, A.P.; Saha, R.; Addya, S.K.Serverless computing is a buzzword that is being used commonly in the world of technology and among developers and businesses. Using the Function-As-A-Service (FaaS) model of serverless, one can easily deploy their applications to the cloud and go live in a matter of days, it facilitates the developers to focus on their core business logic and the backend process such as managing the infrastructure, scaling of the application, updation of software and other dependencies is handled by the Cloud Service Provider. One of the features of serverless computing is ability to scale the containers to zero, which results in a problem called cold start. The challenging part is to reduce the cold start latency without the consumption of extra resources. In this paper, we use SARIMA (Seasonal Auto Regressive Integrated Moving Average), one of the classical time series forecasting models to predict the time at which the incoming request comes, and accordingly increase or decrease the amount of required containers to minimize the resource wastage, thus reducing the function launching time. Finally, we implement PBA (Prediction Based Autoscaler) and compare it with the default HPA (Horizontal Pod Autoscaler), which comes inbuilt with kubernetes. The results showed that PBA performs fairly better than the default HPA, while reducing the wastage of resources. © 2022 IEEE.Item A Preliminary Study of Serverless Platforms for Latency Sensitive Applications(Institute of Electrical and Electronics Engineers Inc., 2022) Sarathi, T.V.; Sai Nischal Reddy, J.; Shiva, P.; Saha, R.; Satpathy, A.; Addya, S.K.Serverless computing is the new-age cloud delivery model wherein resources are provisioned only during event-triggered functions. It dramatically improves the flexibility and scalability of applications compared to virtual machine (VM)/container-based service delivery models. As serverless computing is gaining significant impetus, major cloud providers such as Amazon, Microsoft Azure, and Google have launched their respective serverless computing platforms. However, for a user selecting an appropriate service provider (SP), meeting its desired quality-of-services (QoS) is challenging. Moreover, there is not enough public information available to assist the users in making such accurate decisions. Hence, we provide preliminary analysis via real-time experimentation for the users in this work, acting as a stepping stone in selecting an appropriate SP. To evaluate, we consider execution time and execution cost as evaluation metrics to assess different real-world SPs' performance by considering different workloads. Experimental results show that Azure functions achieved lower execution times than AWS Lambda and Google Cloud Functions, but in terms of execution cost, AWS Lambda costs much lower than the other two platforms. © 2022 IEEE.Item Effect of post-deposition annealing ambient on Gallium Oxide (Ga2O3) films(SPIE, 2022) Mishra, M.; Saha, R.; Bhowmick, S.; Pandey, S.K.; Chakrabarti, S.Gallium Oxide (Ga2O3) is an emerging wideband semiconductor which can be utilize in solar-blind photodetector and high power electronics application. Having a large bandgap and high breakdown field makes Ga2O3 material suitable for these device applications. However, the physical and the optical properties of Ga2O3 can be tailored by changing the annealing ambient and temperature, and understanding how the annealing atmosphere can affect these properties is crucial for designing a next generation optoelectronic devices. Moreover, the presence of defects and impurities can also affect the device parameters. Thus, in this work, we have investigated the influence of post deposition annealing atmosphere on the morphological, structural, and optical properties of Ga2O3 films. The prepared samples were further went through thermal annealing at 800℃ for 30 mins in Nitrogen (N2), and Oxygen (O2) ambient to achieve β-phase of Ga2O3. The structural properties of all the samples were studied by Atomic force microscopy, and X-ray diffraction while the optical properties were studies by UV-Visible, and photoluminescence spectroscopy. We have found monoclinic β-phase in the polycrystalline annealed Ga2O3 samples. The optical band gap of films were increased after annealing and highest band gap is obtained to 5.44eV in N2 annealed sample as compared to as-deposited sample (4.56eV). A broad photoluminescence spectrum ranged from 350 to 480 nm was observed, which further deconvoluted in three peaks at around 378 nm, 399 nm, and 422 nm in as-deposited sample. The same peaks with broad photoluminescence spectrum was found to be blue shifted for annealed samples as compared to the as-deposited. This study will open a new direction in future deep-UV photodetector fabrication. © 2022 SPIE.Item Reduction of oxygen vacancy related defects in RF sputtered deposited ZnO films by impurity (Phosphorus) incorporation(SPIE, 2022) Mishra, M.; Saha, R.; Bhowmick, S.; Pandey, S.K.; das Gupta, K.D.; Chakrabarti, S.ZnO is a fascinating wide gap (3.37 eV) semiconductor due to its tunable optical and electrical properties, which can be utilized for several nanodevices such as nanogenerators, photodetectors, sensors, lasers, and TFTs. In this study, we have investigated the effect of the incorporation of dopants on the native defects and corresponding optical properties of ZnO. We have prepared three samples for the current study and such samples are named samples Z-0, Z-1, and Z-2 for undoped ZnO film, undoped ZnO film annealed at 800°C, and phosphorus doped ZnO film by using spin-on dopant method at an elevated temperature of 800°C, respectively. The XRD results show a dominant peak along the (002) plane for all samples. The Room-temperature photoluminescence spectra reveal that the broad peak around 542 nm for sample Z-0 gradually shifts towards the UV region for samples Z-1 and Z-2 and appears around 509 nm and 413 nm, respectively. Significantly, such blue emission is associated with the transitions from oxygen vacancies to valence band or zinc interstitial to valance band. Also, relatively huge reductions in oxygen vacancies are observed in phosphorus doped ZnO films as compared with undoped and undoped-anneal films. Further, we have verified such reductions in oxygen vacancies with XPS O-1s spectra-related peaks (~531-532 eV) with high-temperature annealing and phosphorus doping. Therefore, such a type of oxygen vacancy reduction in ZnO films by cost-effective SOD doping technique is highly essential for developing several ZnObased functional devices. © 2022 SPIE.Item Temperature Induced Conductivity Reversal in ZnO Thin Films(SPIE, 2023) Mishra, M.; Bhowmick, S.; Saha, R.; Pandey, S.K.; Chakrabarti, S.ZnO is a fascinating large gap (3.37 eV) semiconductor, which exhibits intrinsically n-type conductive due to its native defects such as zinc interstitials and oxygen vacancies and such n-type related defects tend to compensate the p-type acceptor defects. However, the generation process of p-type defects is more challenging for developing a good quality homojunction optical device. Here we have studied the effect of ex-situ atmospheric annealing on conductivity of ZnO films. The ZnO films were deposited using RF sputtering on Si substrate temperature at 400°C substrate temperature and 2.2E-2 mbar gas pressure. The films were deposited in oxygen-rich ambient to achieve less oxygen vacancy defects in the film. The ex-situ atmospheric annealing is performed at higher temperature of 900 and 1000ºC. The effects of this post-deposition annealing on the electrical, structural, elemental and optical properties of ZnO thin films were investigated in detail. The X-ray Diffraction (XRD) results exhibited the hexagonal wurtzite structure (002) orientation. After annealing, the XRD peak is shifted at higher 2-thetha value, which indicates a reduction in lattice constant. Further, X-ray photoelectron spectroscopy (XPS) had been done and such XPS results confirmed that simultaneous generation of acceptor defects and reduction of oxygen vacancy related donor concentrations. The electrical properties of films were studied using hall measurement system. These electrical parameters were purposive to inspect the effect of ex-situ atmospheric annealing temperatures on conductivity of films. The Hall measurement confirmed that 1000ºC annealed films achieve p-type conductivity with high reproducibility and such p-type behavior exhibits high mobility. Thus, temperature induced conductivity reversal could be a potential and cost-effective technique to achieve highly stable p-type ZnO films. © 2023 SPIE.Item Performance Analysis of Disruptive Instances in Cloud Environment(Institute of Electrical and Electronics Engineers Inc., 2024) Nandy, P.; Saha, R.; Satpathy, A.; Chakraborty, S.; Addya, S.K.Virtualization enables the service providers (SPs) to logically partition the resources into virtual machines (VM) instances. Real-world SPs such as Amazon, Google, Microsoft Azure, IBM, and Oracle provide different flavors of VM instances, such as on-demand, reserved, and low-cost or spot, depending on the type of application hosted. The on-demand instances are short-term and typically incur a higher cost than reserved instances that are provisioned for a longer duration at a discounted rate. Low-cost or spot instances are cost-effective compared to on-demand but are reclaimable by the SPs. The SPs often claim that the on-demand and spot instances achieve similar performance, but it is far from that. This paper studies the performance of spot instances via rigorous experimentation over commercial SPs such as Amazon AWS and Microsoft Azure. Real-world evaluations affirm that spot instances perform poorly compared to their on-demand counterpart concerning memory, CPU, disk read, and write operations. We identify such instances as disruptive and name them so because it does not fulfill the performance, durability, and flexibility expectations like an on-demand instance having the same configuration. We also perform hypothesis testing over the experimental data obtained to corroborate our claim further. © 2024 IEEE.Item An Integrated Geohydrology and Geomorphology Based Subsurface Solid Modelling for Site Suitability of Artificial Groundwater Recharge: Bhalki Micro-watershed, Karnataka(Springer, 2020) Saicharan, V.S.; Naga Jyothi, B.; Saha, R.; Wankhede, T.; Das, I.C.; Venkatesh, J.The groundwater resources of basaltic terrains in peninsular India are decreasing rapidly, due to indiscriminate extraction without considering the recharge capabilities of an aquifer. The main focus of the present study is to develop a good perceptive of the groundwater recharge capabilities in basaltic terrains for long term groundwater sustainability. In the present study 3D aquifer solid model of the sub-surface was integrated with surface variables like geomorphology, lineament density, drainage density, slope, land use along with lithology and soil, derived from earth observation (EO) data. This gives a robust platform to find the complex geology of the study area for facilitating artificial groundwater recharge. The methodology adopted provides an opportunity to integrate all the groundwater-related data for a better understanding of the groundwater and surface water interplay in terms of recharge phenomena. The research signified three categories of recharge zones ‘highly-suitable’; ‘moderately-suitable’; and ‘unsuitable’. The recharge zones are found to be in accord with the observed pre and post-monsoon groundwater table signifying the validity of the model. This study would be helpful to delineate groundwater recharge plan in similar geological provinces for ensuring the balance of groundwater resources. © 2020, GEOL. SOC. INDIA.Item Unfolding the conductivity reversal n- to p-type in phosphorus-doped ZnO thin films by spin-on dopant (SOD) process(Institute of Physics, 2022) Mishra, M.; Saha, R.; Bhowmick, S.; Pandey, S.K.; Chakrabarti, S.Phosphorus doping induced p-type doping in ZnO thin films based on spin-on dopant (SOD) process is reported in this article. Owing to the reduced dependence on the conventional amenities for diffusion/ion-implantation doping, the SOD process provides a simple and cheap doping method. The effect of SOD process temperature on conductivity ZnO thin films is investigated by altering the temperature from 700°C to 1000°C. Systematic field emission scanning electron microscopy analysis demonstrates the impact of doping temperature on the morphological properties of SOD. The x-ray diffraction measurements reveal that the p-type ZnO thin films had (002) preferred crystal orientation. At the same time, x-ray photoelectron spectroscopy validated the formation of the PZn-2VZn complex, which was responsible for the acceptor behaviour of films. Moreover, the photoluminescence spectra tracked down that the origin of 3.35 and 3.31 eV emission peaks is due to the acceptor bound exciton and free-electron to acceptor level transitions, respectively. Finally, an elevated hole concentration of 2.09 × 1016 cm-3 is achieved with a resistivity of 1.14 ω-cm at 800°C doping temperature. However, the film doped at 900°C and 1000°C showed n-type behaviour due to the generation of high concentration donor defects. Here, we successfully demonstrate that the SOD process has great potential to produce high-quality p-type ZnO thin films suitable for optoelectronic devices applications. © 2022 IOP Publishing Ltd.Item Investigation of phosphorus-doping of MgZnO thin films using efficient spin-on dopant process(Elsevier B.V., 2023) Mishra, M.; Saha, R.; Tyagi, L.; Sushama, S.; Pandey, S.K.; Chakrabarti, S.Phosphorus doped MgZnO thin films were prepared using the RF sputtering technique on a Si wafer, followed by spin-on doping (SOD) and annealing. The SOD is a cheap and non-destructive process in which the dopant film is spun on a Si wafer and placed in the vicinity of deposited undoped MgZnO thin film at a high temperature to perform doping. After doping, the MgZnO thin films were annealed at temperatures such as 700, 800, and 900°C, which significantly improved morphological, structural, and optical properties. The atomic force microscopy and scanning electron microscopy measurements revealed that phosphorus-doped MgZnO thin films annealed at 800–900°C have good morphology and large grains. X-ray diffraction spectra demonstrated the (002) orientation of MgZnO thin films. The photoluminescence spectra measured at 20 K demonstrated the acceptor bound exciton peak at 3.47 eV and acceptor binding energy of around 64.34 meV, indicating the formation of shallow acceptor levels by phosphorus doping of MgZnO thin films using the SOD process. In Raman spectroscopy measurement, the peak of E2high phonons mode of MgZnO wurtzite structure was observed around 436 cm−1. The FWHM value of this peak reduces with augmentation annealing temperature, demonstrating improvement in crystallinity. X-ray photoelectron spectroscopy measurement demonstrated the presence of phosphorus atoms in the SOD processed MgZnO thin films, which is again verified by Fourier-transform infrared spectroscopy measurement showing vibration modes of P–O bonds. It was observed that the different properties of SOD-prepared phosphorus-doped MgZnO films were superior to the film prepared using the alternate costly and destructive ion-implantation technique. These findings have revealed that high-quality phosphorus-doped p-type MgZnO thin films by the SOD process are very suitable for UV optoelectronic device applications. © 2023 Elsevier B.V.