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Prof. ABU UL HASSAN SARWAR RANA
Department of Intelligent Mechatronics Engineering, Sejong University, Seoul 05006, Korea

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Journal article
Published: 24 February 2021 in Sensors
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Cloud computing offers the services to access, manipulate and configure data online over the web. The cloud term refers to an internet network which is remotely available and accessible at anytime from anywhere. Cloud computing is undoubtedly an innovation as the investment in the real and physical infrastructure is much greater than the cloud technology investment. The present work addresses the issue of power consumption done by cloud infrastructure. As there is a need for algorithms and techniques that can reduce energy consumption and schedule resource for the effectiveness of servers. Load balancing is also a significant part of cloud technology that enables the balanced distribution of load among multiple servers to fulfill users’ growing demand. The present work used various optimization algorithms such as particle swarm optimization (PSO), cat swarm optimization (CSO), BAT, cuckoo search algorithm (CSA) optimization algorithm and the whale optimization algorithm (WOA) for balancing the load, energy efficiency, and better resource scheduling to make an efficient cloud environment. In the case of seven servers and eight server’s settings, the results revealed that whale optimization algorithm outperformed other algorithms in terms of response time, energy consumption, execution time and throughput.

ACS Style

Shanky Goyal; Shashi Bhushan; Yogesh Kumar; Abu Rana; Muhammad Bhutta; Muhammad Ijaz; YoungDoo Son. An Optimized Framework for Energy-Resource Allocation in a Cloud Environment based on the Whale Optimization Algorithm. Sensors 2021, 21, 1583 .

AMA Style

Shanky Goyal, Shashi Bhushan, Yogesh Kumar, Abu Rana, Muhammad Bhutta, Muhammad Ijaz, YoungDoo Son. An Optimized Framework for Energy-Resource Allocation in a Cloud Environment based on the Whale Optimization Algorithm. Sensors. 2021; 21 (5):1583.

Chicago/Turabian Style

Shanky Goyal; Shashi Bhushan; Yogesh Kumar; Abu Rana; Muhammad Bhutta; Muhammad Ijaz; YoungDoo Son. 2021. "An Optimized Framework for Energy-Resource Allocation in a Cloud Environment based on the Whale Optimization Algorithm." Sensors 21, no. 5: 1583.

Journal article
Published: 30 November 2020 in Nanomaterials
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Low-cost, vanadium-based mixed metal oxides mostly have a layered crystal structure with excellent kinetics for lithium-ion batteries, providing high energy density. The existence of multiple oxidation states and the coordination chemistry of vanadium require cost-effective, robust techniques to synthesize the scaling up of their morphology and surface properties. Hydrothermal synthesis is one of the most suitable techniques to achieve pure phase and multiple morphologies under various conditions of temperature and pressure. We attained a simple one-step hydrothermal approach to synthesize the reduced graphene oxide coated Nickel Vanadate ([email protected]) composite with interconnected hollow microspheres. The self-assembly route produced microspheres, which were interconnected under hydrothermal treatment. Cyclic performance determined the initial discharge/charge capacities of 1209.76/839.85 mAh g−1 at the current density of 200 mA g−1 with a columbic efficiency of 69.42%, which improved to 99.64% after 100 cycles. High electrochemical performance was observed due to high surface area, the porous nature of the interconnected hollow microspheres, and rGO induction. These properties increased the contact area between electrode and electrolyte, the active surface of the electrodes, and enhanced electrolyte penetration, which improved Li-ion diffusivity and electronic conductivity.

ACS Style

Faizan Ghani; In Wook Nah; Hyung-Seok Kim; JongChoo Lim; Afifa Marium; Muhammad Fazal Ijaz; Abu Ul Hassan S. Rana. Facile One-Step Hydrothermal Synthesis of the [email protected]2O8 Interconnected Hollow Microspheres Composite for Lithium-Ion Batteries. Nanomaterials 2020, 10, 2389 .

AMA Style

Faizan Ghani, In Wook Nah, Hyung-Seok Kim, JongChoo Lim, Afifa Marium, Muhammad Fazal Ijaz, Abu Ul Hassan S. Rana. Facile One-Step Hydrothermal Synthesis of the [email protected]2O8 Interconnected Hollow Microspheres Composite for Lithium-Ion Batteries. Nanomaterials. 2020; 10 (12):2389.

Chicago/Turabian Style

Faizan Ghani; In Wook Nah; Hyung-Seok Kim; JongChoo Lim; Afifa Marium; Muhammad Fazal Ijaz; Abu Ul Hassan S. Rana. 2020. "Facile One-Step Hydrothermal Synthesis of the [email protected]2O8 Interconnected Hollow Microspheres Composite for Lithium-Ion Batteries." Nanomaterials 10, no. 12: 2389.

Journal article
Published: 26 August 2020 in Nanomaterials
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Memristive systems can provide a novel strategy to conquer the von Neumann bottleneck by evaluating information where data are located in situ. To meet the rising of artificial neural network (ANN) demand, the implementation of memristor arrays capable of performing matrix multiplication requires highly reproducible devices with low variability and high reliability. Hence, we present an Ag/CuO/SiO2/p-Si heterostructure device that exhibits both resistive switching (RS) and negative differential resistance (NDR). The memristor device was fabricated on p-Si and Indium Tin Oxide (ITO) substrates via cost-effective ultra-spray pyrolysis (USP) method. The quality of CuO nanoparticles was recognized by studying Raman spectroscopy. The topology information was obtained by scanning electron microscopy. The resistive switching and negative differential resistance were measured from current–voltage characteristics. The results were then compared with the Ag/CuO/ITO device to understand the role of native oxide. The interface barrier and traps associated with the defects in the native silicon oxide limited the current in the negative cycle. The barrier confined the filament rupture and reduced the reset variability. Reset was primarily influenced by the filament rupture and detrapping in the native oxide that facilitated smooth reset and NDR in the device. The resistive switching originated from traps in the localized states of amorphous CuO. The set process was mainly dominated by the trap-controlled space-charge-limited; this led to a transition into a Poole–Frenkel conduction. This research opens up new possibilities to improve the switching parameters and promote the application of RS along with NDR.

ACS Style

Pundalik D. Walke; Abu Ul Hassan Sarwar Rana; Shavkat U. Yuldashev; Verjesh Kumar Magotra; Dong Jin Lee; Shovkat Abdullaev; Tae Won Kang; Hee Chang Jeon. Memristive Devices from CuO Nanoparticles. Nanomaterials 2020, 10, 1677 .

AMA Style

Pundalik D. Walke, Abu Ul Hassan Sarwar Rana, Shavkat U. Yuldashev, Verjesh Kumar Magotra, Dong Jin Lee, Shovkat Abdullaev, Tae Won Kang, Hee Chang Jeon. Memristive Devices from CuO Nanoparticles. Nanomaterials. 2020; 10 (9):1677.

Chicago/Turabian Style

Pundalik D. Walke; Abu Ul Hassan Sarwar Rana; Shavkat U. Yuldashev; Verjesh Kumar Magotra; Dong Jin Lee; Shovkat Abdullaev; Tae Won Kang; Hee Chang Jeon. 2020. "Memristive Devices from CuO Nanoparticles." Nanomaterials 10, no. 9: 1677.

Paper
Published: 14 April 2020 in RSC Advances
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The crystal architecture of TiO2 was successfully tailored via a low-temperature (≤200 °C) hydrothermal process in the presence of d-mannitol for feasible applications in dye-sensitized solar cells (DSSCs) and heterogeneous catalysis.

ACS Style

Abdullah M. Al-Enizi; T. A. J. Siddiqui; ShoyebMohamad F. Shaikh; Mohd Ubaidullah; Ayman Yousef; Rajaram S. Mane; Abu Ul Hassan Sarwar Rana. Phase controlled synthesis of bifunctional TiO2 nanocrystallites viad-mannitol for dye-sensitized solar cells and heterogeneous catalysis. RSC Advances 2020, 10, 14826 -14836.

AMA Style

Abdullah M. Al-Enizi, T. A. J. Siddiqui, ShoyebMohamad F. Shaikh, Mohd Ubaidullah, Ayman Yousef, Rajaram S. Mane, Abu Ul Hassan Sarwar Rana. Phase controlled synthesis of bifunctional TiO2 nanocrystallites viad-mannitol for dye-sensitized solar cells and heterogeneous catalysis. RSC Advances. 2020; 10 (25):14826-14836.

Chicago/Turabian Style

Abdullah M. Al-Enizi; T. A. J. Siddiqui; ShoyebMohamad F. Shaikh; Mohd Ubaidullah; Ayman Yousef; Rajaram S. Mane; Abu Ul Hassan Sarwar Rana. 2020. "Phase controlled synthesis of bifunctional TiO2 nanocrystallites viad-mannitol for dye-sensitized solar cells and heterogeneous catalysis." RSC Advances 10, no. 25: 14826-14836.

Journal article
Published: 13 January 2020 in Nanomaterials
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Hitherto, most research has primarily focused on improving the UV sensor efficiency via surface treatments and by stimulating the ZnO nanorod (ZNR) surface Schottky barriers. However, to the best of our knowledge, no study has yet probed the intrinsic crystal defect generation and its effects on UV sensor efficiency. In this study, we undertake this task by fabricating an intrinsic defect-prone hydrothermally grown ZNRs (S1), Ga-doped ZNRs (S2), and defect-free microwave-assisted grown ZNRs (S3). The defect states were recognized by studying X-ray diffraction and photoluminescence characteristics. The large number of crystal defects in S1 and S2 had two pronged disadvantages. (1) Most of the UV light was absorbed by the defect traps and the e–h pair generation was compromised. (2) Mobility was directly affected by the carrier–carrier scattering and phonon scattering processes. Hence, the overall UV sensor efficiency was compromised based on the defect-induced mobility-response model. Considering the facts, defect-free S3 exhibited the best UV sensor performance with the highest on/off ratio, the least impulse response time, the highest recombination time, and highest gain-induced responsivity to 368 nm UV light, which was desired of an efficient passive metal oxide-based UV sensor. Our results were compared with the recently published results.

ACS Style

Abu Ul Hassan Sarwar Rana; ShoyebMohamad F. Shaikh; Abdullah M. Al-Enizi; Daniel Adjei Agyeman; Faizan Ghani; In Wook Nah; Areej Shahid. Intrinsic Control in Defects Density for Improved ZnO Nanorod-Based UV Sensor Performance. Nanomaterials 2020, 10, 142 .

AMA Style

Abu Ul Hassan Sarwar Rana, ShoyebMohamad F. Shaikh, Abdullah M. Al-Enizi, Daniel Adjei Agyeman, Faizan Ghani, In Wook Nah, Areej Shahid. Intrinsic Control in Defects Density for Improved ZnO Nanorod-Based UV Sensor Performance. Nanomaterials. 2020; 10 (1):142.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; ShoyebMohamad F. Shaikh; Abdullah M. Al-Enizi; Daniel Adjei Agyeman; Faizan Ghani; In Wook Nah; Areej Shahid. 2020. "Intrinsic Control in Defects Density for Improved ZnO Nanorod-Based UV Sensor Performance." Nanomaterials 10, no. 1: 142.

Communication
Published: 27 November 2018 in Nanomaterials
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ZnO has the built-in characteristics of both ionic and covalent compound semiconductors, which makes the metal–ZnO carrier transport mechanism quite intricate. The growth mechanism-centric change in ZnO defect density and carrier concentration also makes the contact formation and behavior unpredictable. This study investigates the uncertainty in Au–ZnO contact behavior for application-oriented research and the development on ZnO nanostructures. Herein, we explain the phenomenon for how Au–ZnO contact could be rectifying or non-rectifying. Growth method-dependent defect engineering was exploited to explain the change in Schottky barrier heights at the Au–ZnO interface, and the change in device characteristics from Schottky to Ohmic and vice versa. The ZnO nanorods were fabricated via aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. For further investigations, one ACG sample was doped with Ga, and another was subjected to oxygen plasma treatment (OPT). The ACG and Ga-doped ACG samples showed a quasi-Ohmic and Ohmic behavior, respectively, because of a high surface and subsurface level donor defect-centric Schottky barrier pinning at the Au–ZnO interface. However, the ACG-OPT and MAG samples showed a more pronounced Schottky contact because of the presence of low defect-centric carrier concentration via MAG, and the removal of the surface accumulation layer via the OPT process.

ACS Style

Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa. Nanomaterials 2018, 8, 980 .

AMA Style

Abu Ul Hassan Sarwar Rana, Hyun-Seok Kim. Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa. Nanomaterials. 2018; 8 (12):980.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. 2018. "Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa." Nanomaterials 8, no. 12: 980.

Journal article
Published: 06 May 2018 in Sensors
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Over the last few decades, the development of the electronic nose (E-nose) for detection and quantification of dangerous and odorless gases, such as methane (CH4) and carbon monoxide (CO), using an array of SnO2 gas sensors has attracted considerable attention. This paper addresses sensor cross sensitivity by developing a classifier and estimator using an artificial neural network (ANN) and least squares regression (LSR), respectively. Initially, the ANN was implemented using a feedforward pattern recognition algorithm to learn the collective behavior of an array as the signature of a particular gas. In the second phase, the classified gas was quantified by minimizing the mean square error using LSR. The combined approach produced 98.7% recognition probability, with 95.5 and 94.4% estimated gas concentration accuracies for CH4 and CO, respectively. The classifier and estimator parameters were deployed in a remote microcontroller for the actualization of a wireless E-nose system.

ACS Style

Areej Shahid; Jong-Hyeok Choi; Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. Least Squares Neural Network-Based Wireless E-Nose System Using an SnO2 Sensor Array. Sensors 2018, 18, 1446 .

AMA Style

Areej Shahid, Jong-Hyeok Choi, Abu Ul Hassan Sarwar Rana, Hyun-Seok Kim. Least Squares Neural Network-Based Wireless E-Nose System Using an SnO2 Sensor Array. Sensors. 2018; 18 (5):1446.

Chicago/Turabian Style

Areej Shahid; Jong-Hyeok Choi; Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. 2018. "Least Squares Neural Network-Based Wireless E-Nose System Using an SnO2 Sensor Array." Sensors 18, no. 5: 1446.

Journal article
Published: 27 April 2018 in Coatings
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Tin-doped cadmium oxide (Sn:CdO) transparent thin films with different Sn concentrations were deposited on glass and p-silicon substrates by the chemical spray method at 250 °C. Different concentrations of stannic chloride were used to prepare Sn:CdO thin films. The prepared doped and un-doped CdO films were subjected to X-ray diffraction (XRD), scanning electron microscopy and atomic force microscopy, optical absorption, and electrical analyses to characterize their structural, morphological, optical, and electrical properties, respectively. XRD analysis demonstrated the growth of polycrystalline and cubic CdO with preferential orientation along the (111) plane. Sn-doping shifted the XRD peaks slightly towards a higher Bragg angle and increased the band gap of CdO thin films. Variation in doping concentration also affected the morphology of the films. Optimum Sn-doping increased the electrical conductivity of CdO thin films. Furthermore, to the best of our knowledge, the photoresponse analyses of the fabricated un-doped and doped n-CdO/p-Si heterostructures were performed for the first time in this study.

ACS Style

A. Kathalingam; K. Kesavan; Abu Ul Hassan Sarwar Rana; Joonhyeon Jeon; Hyun-Seok Kim. Analysis of Sn Concentration Effect on Morphological, Optical, Electrical and Photonic Properties of Spray-Coated Sn-Doped CdO Thin Films. Coatings 2018, 8, 167 .

AMA Style

A. Kathalingam, K. Kesavan, Abu Ul Hassan Sarwar Rana, Joonhyeon Jeon, Hyun-Seok Kim. Analysis of Sn Concentration Effect on Morphological, Optical, Electrical and Photonic Properties of Spray-Coated Sn-Doped CdO Thin Films. Coatings. 2018; 8 (5):167.

Chicago/Turabian Style

A. Kathalingam; K. Kesavan; Abu Ul Hassan Sarwar Rana; Joonhyeon Jeon; Hyun-Seok Kim. 2018. "Analysis of Sn Concentration Effect on Morphological, Optical, Electrical and Photonic Properties of Spray-Coated Sn-Doped CdO Thin Films." Coatings 8, no. 5: 167.

Review
Published: 19 April 2018 in Nanomaterials
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Supercapacitors (SCs) have received a great deal of attention and play an important role for future self-powered devices, mainly owing to their higher power density. Among all types of electrical energy storage devices, electrochemical supercapacitors are considered to be the most promising because of their superior performance characteristics, including short charging time, high power density, safety, easy fabrication procedures, and long operational life. An SC consists of two foremost components, namely electrode materials, and electrolyte. The selection of appropriate electrode materials with rational nanostructured designs has resulted in improved electrochemical properties for high performance and has reduced the cost of SCs. In this review, we mainly spotlight the non-metallic oxide, especially metal chalcogenides (MX; X = S, Se) based nanostructured electrode materials for electrochemical SCs. Different non-metallic oxide materials are highlighted in various categories, such as transition metal sulfides and selenides materials. Finally, the designing strategy and future improvements on metal chalcogenide materials for the application of electrochemical SCs are also discussed.

ACS Style

Jayaraman Theerthagiri; K. Karuppasamy; Govindarajan Durai; Abu Ul Hassan Sarwar Rana; Prabhakarn Arunachalam; Kirubanandam Sangeetha; Parasuraman Kuppusami; Hyun-Seok Kim. Recent Advances in Metal Chalcogenides (MX; X = S, Se) Nanostructures for Electrochemical Supercapacitor Applications: A Brief Review. Nanomaterials 2018, 8, 256 .

AMA Style

Jayaraman Theerthagiri, K. Karuppasamy, Govindarajan Durai, Abu Ul Hassan Sarwar Rana, Prabhakarn Arunachalam, Kirubanandam Sangeetha, Parasuraman Kuppusami, Hyun-Seok Kim. Recent Advances in Metal Chalcogenides (MX; X = S, Se) Nanostructures for Electrochemical Supercapacitor Applications: A Brief Review. Nanomaterials. 2018; 8 (4):256.

Chicago/Turabian Style

Jayaraman Theerthagiri; K. Karuppasamy; Govindarajan Durai; Abu Ul Hassan Sarwar Rana; Prabhakarn Arunachalam; Kirubanandam Sangeetha; Parasuraman Kuppusami; Hyun-Seok Kim. 2018. "Recent Advances in Metal Chalcogenides (MX; X = S, Se) Nanostructures for Electrochemical Supercapacitor Applications: A Brief Review." Nanomaterials 8, no. 4: 256.

Journal article
Published: 01 March 2018 in Journal of Nanoscience and Nanotechnology
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We proffer NH4OH-oriented and pH-dependent growth of ZnO nanostructures via a microwaveassisted growth method. The fabrication of ZnO nanorods (ZNRs), nanoflowers (ZNFs), nanostars (ZNSs), and nanotetrapods (ZNTs) is presented. NH4OH was used as a mineralizer to change the solution pH for nanostructure growth, where temperature and other variables were fixed. Because of an efficient heat transfer and facile growth of nanostructures, a domestic microwave oven was used to facilitate the nanostructure growth in the span of just 10–15 min. The results showed that the growth of ZnO nanostructures was dependent upon the number of growth units and ZnO nuclei present in the solution, which ultimately depend upon the pH of the solution. At the outset, without the addition of NH4OH, the pH of the solution was ~6.8 and the ZNRs were formed in the solution or on a seeded substrate which persisted in the pH range of ~6.8–9. An abrupt change in the shapes and the types of the nanostructures was observed when the pH was boosted beyond 10. A transition from ZNRs to ZNFs was observed at pH 10 and ZNFs were formed at pH 11. The solution gave birth to ZNSs and ZNTs when the pH was further raised to 12 and 13, respectively.

ACS Style

Abu Ul Hassan Sarwar Rana; Seung-Bo Chang; Hyun-Seok Kim. NH4OH-Oriented and pH-Dependent Growth of ZnO Nanostructures via Microwave-Assisted Growth Method. Journal of Nanoscience and Nanotechnology 2018, 18, 2125 -2127.

AMA Style

Abu Ul Hassan Sarwar Rana, Seung-Bo Chang, Hyun-Seok Kim. NH4OH-Oriented and pH-Dependent Growth of ZnO Nanostructures via Microwave-Assisted Growth Method. Journal of Nanoscience and Nanotechnology. 2018; 18 (3):2125-2127.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Seung-Bo Chang; Hyun-Seok Kim. 2018. "NH4OH-Oriented and pH-Dependent Growth of ZnO Nanostructures via Microwave-Assisted Growth Method." Journal of Nanoscience and Nanotechnology 18, no. 3: 2125-2127.

Journal article
Published: 01 March 2018 in Journal of Nanoscience and Nanotechnology
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In this study, we present the microwave-assisted growth (MAG) of ZnO nanorods (ZNRs) using a preheating hydrothermal method under tailored preheating and postheating growth conditions. The perimeters such as solution concentration, preheating time, and postheating time, were changedto optimize ZNR growth and the growth was carried out in a domestic 850 watt microwave oven. Preheated solution was utilized as an accelerator to increase the aspect ratio of the ZNRs and reduce the fabrication time. Because of a long fabrication time and limited length in the conventionalMAG method, preheating condition was used for efficient growth of nanorods through homogeneous nucleation in the solution and then heterogeneous nucleation of the formed ZNRs on seeded substrate during postheating process. The nanostructures were characterized with scanning electron microscopyto look at the morphology and dimensions. Dimensions of ZNRs kept on increasing as the molar concentration went higher. Preheating time highly affected the morphology, dimensions, and aspect ratio of ZNRs and postheating time not only ensured the stability of ZNRs with substrate due to heterogeneousnucleation process but also influenced the morphology of ZNRs.

ACS Style

Hyun Uk Chae; Abu Ul Hassan Sarwar Rana; Ye-Jin Park; Hyun-Seok Kim. High-Speed Growth of ZnO Nanorods in Preheating Condition Using Microwave-Assisted Growth Method. Journal of Nanoscience and Nanotechnology 2018, 18, 2041 -2044.

AMA Style

Hyun Uk Chae, Abu Ul Hassan Sarwar Rana, Ye-Jin Park, Hyun-Seok Kim. High-Speed Growth of ZnO Nanorods in Preheating Condition Using Microwave-Assisted Growth Method. Journal of Nanoscience and Nanotechnology. 2018; 18 (3):2041-2044.

Chicago/Turabian Style

Hyun Uk Chae; Abu Ul Hassan Sarwar Rana; Ye-Jin Park; Hyun-Seok Kim. 2018. "High-Speed Growth of ZnO Nanorods in Preheating Condition Using Microwave-Assisted Growth Method." Journal of Nanoscience and Nanotechnology 18, no. 3: 2041-2044.

Article
Published: 10 January 2018 in physica status solidi (a)
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High-power microwave-assisted gallium (Ga) -doped ZnO nanorods (MGZRs) are grown on p-Si substrates, and their optoelectronic characteristics are reported. Gallium nitrate hydrate is mixed with zinc nitrate hexahydrate and hexamethylenetetramine to make 1, 2, and 5% MGZRs in a domestic microwave oven. The MGZR diameter decreased when doping increased from 1 to 2%, but the diameter of the highly doped (5%) sample significantly increased. The EDS results confirm the incorporation of Ga atoms in the ZnO crystal lattice, where an increase in the dopant concentration in growth solution increase the probability of Ga ion incorporation into ZnO crystal lattice. However, exact values for EDS quantification are not found because of Si peaks from the substrate. The high-intensity photoluminescence UV peaks associated to exciton recombination are blue-shifted, and some defects are incorporated by Ga, which respond to the visible and near-IR regions in MGZRs. Furthermore, the n-MGZR/p-Si heterostructures show a diode-like I–V response, where the current levels increase when the doping concentration increase because of an increase in carrier concentration in MGZRs, which is confirmed by Hall-effect measurements. The MGZRs address the low carrier transport issues in undoped microwave-assisted nanorods and are notably effective in altering their optoelectronic characteristics.

ACS Style

Abu Ul Hassan Sarwar Rana; Areej Shahid; Ji Young Lee; Hyun-Seok Kim. High-Power Microwave-Assisted Ga Doping, an Effective Method to Tailor n-ZnO/p-Si Heterostructure Optoelectronic Characteristics. physica status solidi (a) 2018, 215, 1 .

AMA Style

Abu Ul Hassan Sarwar Rana, Areej Shahid, Ji Young Lee, Hyun-Seok Kim. High-Power Microwave-Assisted Ga Doping, an Effective Method to Tailor n-ZnO/p-Si Heterostructure Optoelectronic Characteristics. physica status solidi (a). 2018; 215 (5):1.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Areej Shahid; Ji Young Lee; Hyun-Seok Kim. 2018. "High-Power Microwave-Assisted Ga Doping, an Effective Method to Tailor n-ZnO/p-Si Heterostructure Optoelectronic Characteristics." physica status solidi (a) 215, no. 5: 1.

Journal article
Published: 27 December 2017 in Materials
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Previous studies on Ga-doped ZnO nanorods (GZRs) have failed to address the change in GZR morphology with increased doping concentration. The morphology-change affects the GZR surface-to-volume ratio and the real essence of doping is not exploited for heterostructure optoelectronic characteristics. We present NH4OH treatment to provide an optimum morphological trade-off to n-GZR/p-Si heterostructure characteristics. The GZRs were grown via one of the most eminent and facile hydrothermal method with an increase in Ga concentration from 1% to 5%. The supplementary OH− ion concentration was effectively controlled by the addition of an optimum amount of NH4OH to synchronize GZR aspect and surface-to-volume ratio. Hence, the probed results show only the effects of Ga-doping, rather than the changed morphology, on the optoelectronic characteristics of n-GZR/p-Si heterostructures. The doped nanostructures were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence, Hall-effect measurement, and Keithley 2410 measurement systems. GZRs had identical morphology and dimensions with a typical wurtzite phase. As the GZR carrier concentration increased, the PL response showed a blue shift because of Burstein-Moss effect. Also, the heterostructure current levels increased linearly with doping concentration. We believe that the presented GZRs with optimized morphology have great potential for field-effect transistors, light-emitting diodes, ultraviolet sensors, and laser diodes.

ACS Style

Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. NH4OH Treatment for an Optimum Morphological Trade-off to Hydrothermal Ga-Doped n-ZnO/p-Si Heterostructure Characteristics. Materials 2017, 11, 37 .

AMA Style

Abu Ul Hassan Sarwar Rana, Hyun-Seok Kim. NH4OH Treatment for an Optimum Morphological Trade-off to Hydrothermal Ga-Doped n-ZnO/p-Si Heterostructure Characteristics. Materials. 2017; 11 (1):37.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. 2017. "NH4OH Treatment for an Optimum Morphological Trade-off to Hydrothermal Ga-Doped n-ZnO/p-Si Heterostructure Characteristics." Materials 11, no. 1: 37.

Journal article
Published: 10 September 2017 in Nanomaterials
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It is time for industry to pay a serious heed to the application and quality-dependent research on the most important solution growth methods for ZnO, namely, aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. This study proffers a critical analysis on how the defect density and formation behavior of ZnO nanostructures (ZNSs) are growth method-dependent. Both antithetical and facile methods are exploited to control the ZnO defect density and the growth mechanism. In this context, the growth of ZnO nanorods (ZNRs), nanoflowers, and nanotubes (ZNTs) are considered. The aforementioned growth methods directly stimulate the nanostructure crystal growth and, depending upon the defect density, ZNSs show different trends in structural, optical, etching, and conductive properties. The defect density of MAG ZNRs is the least because of an ample amount of thermal energy catered by high-power microwaves to the atoms to grow on appropriate crystallographic planes, which is not the case in faulty convective ACG ZNSs. Defect-centric etching of ZNRs into ZNTs is also probed and methodological constraints are proposed. ZNS optical properties are different in the visible region, which are quite peculiar, but outstanding for ZNRs. Hall effect measurements illustrate incongruent conductive trends in both samples.

ACS Style

Abu Ul Hassan Sarwar Rana; Ji Young Lee; Areej Shahid; Hyun-Seok Kim. Growth Method-Dependent and Defect Density-Oriented Structural, Optical, Conductive, and Physical Properties of Solution-Grown ZnO Nanostructures. Nanomaterials 2017, 7, 266 .

AMA Style

Abu Ul Hassan Sarwar Rana, Ji Young Lee, Areej Shahid, Hyun-Seok Kim. Growth Method-Dependent and Defect Density-Oriented Structural, Optical, Conductive, and Physical Properties of Solution-Grown ZnO Nanostructures. Nanomaterials. 2017; 7 (9):266.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Ji Young Lee; Areej Shahid; Hyun-Seok Kim. 2017. "Growth Method-Dependent and Defect Density-Oriented Structural, Optical, Conductive, and Physical Properties of Solution-Grown ZnO Nanostructures." Nanomaterials 7, no. 9: 266.

Journal article
Published: 01 June 2017 in Journal of Nanoscience and Nanotechnology
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Surface acoustic wave (SAW) sensors have been emerged as alluring candidates with myriads of applications in the realm of gas sensors, biosensors, and UV light detecting technology. In this study, SAW thermoelectric sensor, with the center frequency of ~80 MHz, was fabricated by a vertical growth of ZnO nanorods on ST-X cut quartz substrate by dint of aqueous chemical growth method. The SAW device properties were estimated by glancing at the transmission spectrum characteristics like the shift in frequency and the decrease in signal amplitude. In the temperature range of 20 °C to 160 °C, frequency shift of ~40 kHz, with ~1 dB descent for each 20 °C period, was observed in the negative direction. Also, when the sensor was exposed to 365 nm UV light, an additional negative frequency shift of ~11.6 kHz was realized for each 20 °C period. The frequency shift and the decrease in the signal amplitude were caused by an increment in the surface conductivity of SAW sensor because of thermal and photo-generated carriers.

ACS Style

Mingi Kang; Abu Ul Hassan Sarwar Rana; Eun-Seon Jeong; Hyun-Seok Kim. Direct Observation of Thermally Generated Electron–Hole Pairs in ZnO Nanorods With Surface Acoustic Wave. Journal of Nanoscience and Nanotechnology 2017, 17, 4141 -4144.

AMA Style

Mingi Kang, Abu Ul Hassan Sarwar Rana, Eun-Seon Jeong, Hyun-Seok Kim. Direct Observation of Thermally Generated Electron–Hole Pairs in ZnO Nanorods With Surface Acoustic Wave. Journal of Nanoscience and Nanotechnology. 2017; 17 (6):4141-4144.

Chicago/Turabian Style

Mingi Kang; Abu Ul Hassan Sarwar Rana; Eun-Seon Jeong; Hyun-Seok Kim. 2017. "Direct Observation of Thermally Generated Electron–Hole Pairs in ZnO Nanorods With Surface Acoustic Wave." Journal of Nanoscience and Nanotechnology 17, no. 6: 4141-4144.

Journal article
Published: 01 October 2016 in Journal of Nanoscience and Nanotechnology
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In this study, we present the fabrication and transition between ZnO nanorods (ZNRs) and ZnO nanotubes (ZNTs) with their antithetical properties. We etch the aqueous chemically grown ZNRs into ZNTs via a chemical etching method in KCl solution without any surface and subsurface processing on ZNRs. In order to have a perfect transition, we change the parameters, such as KCl molar concentration, etching time, and catalyzing temperature. The SEM images show a perfect transition from ZNRs into ZNTs with almost the same diameter of around 60 nm, which is one of the smallest achieved for a transition at this time. The transition dependence of ZNRs into ZNTs on the diameter and the surface roughness of ZNRs is also substantiated by applying the etching on ZnO nanopyramids that are either not etched at the given etching time or started etching with the dissolution of lateral walls. The two different structures are characterized via a two-probe method to look at the antithetical electrical behavior of ZNRs and ZNTs. It is proved that ZNTs are more sensitive, have higher levels of current, and have lower turn-on voltages because ZNTs have a higher level of surface and subsurface oxygen vacancies with a higher surface-to-volume ratio as compared to ZNRs.

ACS Style

Abu Ul Hassan Sarwar Rana; Mingi Kang; Eun-Seon Jeong; Hyun-Seok Kim. Transition Between ZnO Nanorods and ZnO Nanotubes with Their Antithetical Properties. Journal of Nanoscience and Nanotechnology 2016, 16, 10772 -10776.

AMA Style

Abu Ul Hassan Sarwar Rana, Mingi Kang, Eun-Seon Jeong, Hyun-Seok Kim. Transition Between ZnO Nanorods and ZnO Nanotubes with Their Antithetical Properties. Journal of Nanoscience and Nanotechnology. 2016; 16 (10):10772-10776.

Chicago/Turabian Style

Abu Ul Hassan Sarwar Rana; Mingi Kang; Eun-Seon Jeong; Hyun-Seok Kim. 2016. "Transition Between ZnO Nanorods and ZnO Nanotubes with Their Antithetical Properties." Journal of Nanoscience and Nanotechnology 16, no. 10: 10772-10776.

Journal article
Published: 21 October 2014 in physica status solidi (a)
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We investigate the performance of hyperabrupt doping profile based GaAs varactor diodes. Epitaxially grown GaAs nn+ devices, having an intentionally graded n‐active layer doping concentration, exhibit significant improvements in the breakdown voltage and capacitance relative to flat n‐active layer devices. It is found that the varactor diodes with a hyperabrupt doping profile are effective in shifting the breakdown voltage. Moreover, the capacitance in the hyperabrupt graded junction is comparatively more dependent on the reverse‐bias voltage than that in the uniformly doped junction. Experimental results indicate a maximum reverse breakdown voltage of 40 V at a leakage current of 165 µA. Furthermore, the maximum and minimum capacitances are 3.88 and 0.72 pF, respectively, for an anode diameter of 70 µm, resulting in a Cmax/Cmin ratio of 5.39.

ACS Style

Jun-Woo Heo; SeJun Hong; Seok-Gyu Choi; Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. Characteristics of GaAs varactor diode with hyperabrupt doping profile. physica status solidi (a) 2014, 212, 612 -616.

AMA Style

Jun-Woo Heo, SeJun Hong, Seok-Gyu Choi, Abu Ul Hassan Sarwar Rana, Hyun-Seok Kim. Characteristics of GaAs varactor diode with hyperabrupt doping profile. physica status solidi (a). 2014; 212 (3):612-616.

Chicago/Turabian Style

Jun-Woo Heo; SeJun Hong; Seok-Gyu Choi; Abu Ul Hassan Sarwar Rana; Hyun-Seok Kim. 2014. "Characteristics of GaAs varactor diode with hyperabrupt doping profile." physica status solidi (a) 212, no. 3: 612-616.