44 results on '"Surani, Bin Dolmanan"'
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2. Patterning at the Resolution Limit of Commercial Electron Beam Lithography
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Mohammad S. M. Saifullah, Mohamed Asbahi, Darren C. J. Neo, Zackaria Mahfoud, Hui Ru Tan, Son Tung Ha, Neeraj Dwivedi, Tanmay Dutta, Surani bin Dolmanan, Zainul Aabdin, Michel Bosman, Ramakrishnan Ganesan, Sudhiranjan Tripathy, David G. Hasko, and Suresh Valiyaveettil
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Mechanical Engineering ,General Materials Science ,Bioengineering ,General Chemistry ,Condensed Matter Physics - Abstract
It has been long known that low molecular weight resists can achieve a very high resolution, theoretically close to the probe diameter of the electron beam lithography (EBL) system. Despite technological improvements in EBL systems, the advances in resists have lagged behind. Here we demonstrate that a low-molecular-mass single-source precursor resist (based on cadmium(II) ethylxanthate complexed with pyridine) is capable of a achieving resolution (4 nm) that closely matches the measured probe diameter (∼3.8 nm). Energetic electrons enable the top-down radiolysis of the resist, while they provide the energy to construct the functional material from the bottom-up─unit cell by unit cell. Since this occurs only within the volume of resist exposed to primary electrons, the minimum size of the patterned features is close to the beam diameter. We speculate that angstrom-scale patterning of functional materials is possible with single-source precursor resists using an aberration-corrected electron beam writer with a spot size of ∼1 Å.
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- 2022
3. Effect of self-heating on electrical characteristics of AlGaN/ GaN HEMT on Si (111) substrate
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Adarsh Nigam, Thirumaleshwara N. Bhat, Saravanan Rajamani, Surani Bin Dolmanan, Sudhiranjan Tripathy, and Mahesh Kumar
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Physics ,QC1-999 - Abstract
In order to study the effect of self-heating of AlGaN/ GaN high electron mobility transistors (HEMTs) characteristics fabricated on Si(111) substrate, simulations of 2DEG temperature on different drain voltages have been carried out by Sentaurus TCAD simulator tool. Prior to the electrical direct-current (DC) characteristics studies, structural properties of the HEMT structures were examined by scanning transmission electron microscopy. The comparative analysis of simulation and experimental data provided sheet carrier concentration, mobility, surface traps, electron density at 2DEG by considering factors such as high field saturation, tunneling and recombination models. Mobility, surface trap concentration and contact resistance were obtained by TCAD simulation and found out to be ∼1270cm2/Vs, ∼2×1013 cm-2 and ∼0.2 Ω.mm, respectively, which are in agreement with the experimental results. Consequently, simulated current-voltage characteristics of HEMTs are in good agreement with experimental results. The present simulator tool can be used to design new device structures for III-nitride technology.
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- 2017
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4. Fabrication and Modeling-Based Performance Analysis of Circular GaN MOSHEMT-Based Electrochemical Sensors
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Lava Bhargava, Arathy Varghese, Sukant K. Tripathy, Surani Bin Dolmanan, and Chinnamuthan Periasamy
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Fabrication ,Materials science ,Passivation ,business.industry ,010401 analytical chemistry ,Charge density ,High-electron-mobility transistor ,01 natural sciences ,0104 chemical sciences ,Atomic layer deposition ,Gate oxide ,Logic gate ,Optoelectronics ,Sensitivity (control systems) ,Electrical and Electronic Engineering ,business ,Instrumentation - Abstract
C-MOSHEMT (Circular-Metal Oxide Semiconductor High Electron Mobility Transistor) has been modeled, fabricated and sensitivity analysis has been done for pH detection application for the first time. Prototype model of the sensor has been developed considering a ring gate structure. The perimeter of the gate inner ring is taken as the gate length and a gate width of $100~\mu \text{m}$ has been used to plot normalized device characteristics. Advantage of C-MOSHEMT over L-MOSHEMT (linear MOSHEMT) is that the area available for sensing increases and process cost and complexity involved remains low from the fabrication point of view. The overall fabrication cost and process overheads reduce with elimination of the mesa isolation etch. ALD (Atomic Layer Deposition) deposited Al2O3 used as the gate oxide and passivation scheme in the device design ensures higher sensitivities along with current collapse free device operation. Analytical model along with experimental analysis have been done using 3 standard buffer pH samples, pH=4, 7, and 9.2. The devices fabricated showcase a maximum sensitivity of 1.74 mA/pH and 1.86 mA/pH when gate lengths ( $\text{L}_{G}$ ) of $3~\mu \text{m}$ and $5\mu \text{m}$ are considered. Further, the model and the physical detection results are compared and contrasted to study the strengths and weaknesses of the model developed. It has been observed that as sensing area is doubled, the sensitivity increases by 41% which can be attributed to the discreteness of charge distribution on the sensing surface.
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- 2021
5. Room-Temperature Patterning of Nanoscale MoS2 under an Electron Beam
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Mohamed Asbahi, Karen S. L. Chong, Asadullah Ibn Saifullah, Sing Shy Liow, Mohammad S. M. Saifullah, Maryam Binti-Kamran Kiyani, Tanmay Dutta, Sukant K. Tripathy, Anna Marie Yong, Hui Ru Tan, Surani Bin Dolmanan, Neeraj Dwivedi, Ramakrishnan Ganesan, Esther A. H. Ong, and Suresh Valiyaveettil
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inorganic chemicals ,Chemical substance ,Materials science ,business.industry ,macromolecular substances ,chemistry.chemical_compound ,Nanolithography ,Resist ,chemistry ,Cathode ray ,bacteria ,Optoelectronics ,General Materials Science ,business ,Science, technology and society ,Nanoscopic scale ,Molybdenum disulfide ,Electron-beam lithography - Abstract
Molybdenum disulfide (MoS2) is traditionally grown at a high temperature and subsequently patterned to study its electronic properties or make devices. This method imposes severe limitations on the...
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- 2020
6. Sensitive and Selective Detection of Pb2+ Ions Using 2,5-Dimercapto-1,3,4-Thiadiazole Functionalized AlGaN/GaN High Electron Mobility Transistor
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Mahesh Kumar, Adarsh Nigam, Thirumaleshwara N. Bhat, Sukant K. Tripathy, Vijendra Singh Bhati, and Surani Bin Dolmanan
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010302 applied physics ,Detection limit ,Materials science ,Wide-bandgap semiconductor ,Analytical chemistry ,Gallium nitride ,High-electron-mobility transistor ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Sensitivity (control systems) ,Electrical and Electronic Engineering ,Selectivity ,Fermi gas - Abstract
We report sensitive and selective AlGaN/GaN High Electron Mobility Transistor (HEMT)-based sensor for Lead ion (Pb2+) detection. The gate region of the HEMT was functionalized by 2,5-dimercapto-1,3,4-thiadiazole (DMTD). The response of the sensor is observed by monitoring drain to source current ( $\text{I}_{\textsf {DS}}$ ) for different concentrations of Pb2+ ions at a fixed drain to source voltage ( $\text{V}_{\textsf {DS}}$ ). Our sensor reaches the lower detection limit of 0.018 ppb, which is much lower than the standard detection limit recommended by the World Health Organization (WHO) for drinking water. Furthermore, the sensor exhibited a rapid response time of ~4 seconds and high sensitivity of $0.607~\mu \text{A}$ /ppb. Moreover, the selectivity analysis was performed and found that the sensor was highly selective towards Pb2+ ions. The change in electron concentration at 2-dimensional electron gas (2DEG) upon the capture of Pb2+ ions at gate region by DMTD, causes a change in the $\text{I}_{\textsf {DS}}$ , which showed excellent sensing response towards Pb2+ ions. The highly sensitive, selective, and rapid detection of Pb2+ ions paves the way for stable sensing performance based on DMTD functionalized AlGaN/GaN HEMT sensor.
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- 2019
7. 1T and 2H heterophase MoS
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Nipun, Sharma, Adarsh, Nigam, Surani, Bin Dolmanan, Ankur, Gupta, Sudhiranjan, Tripathy, and Mahesh, Kumar
- Abstract
We report significantly enhanced sensitivity of AlGaN/GaN-based high electron mobility transistor (HEMT) sensor by the targeted synthesis of IT and 2H coexisting phase MoS
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- 2021
8. MPA-GSH Functionalized AlGaN/GaN High-Electron Mobility Transistor-Based Sensor for Cadmium Ion Detection
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Mahesh Kumar, Sukant K. Tripathy, Thirumaleshwara N. Bhat, Adarsh Nigam, Vijendra Singh Bhati, and Surani Bin Dolmanan
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Detection limit ,Materials science ,Metal ions in aqueous solution ,010401 analytical chemistry ,Transistor ,Analytical chemistry ,Wide-bandgap semiconductor ,High-electron-mobility transistor ,01 natural sciences ,0104 chemical sciences ,Ion ,law.invention ,law ,Surface modification ,Electrical and Electronic Engineering ,Selectivity ,Instrumentation - Abstract
This paper demonstrates a novel AlGaN/GaN high-electron mobility transistor (HEMT)-based cadmium ion (Cd2+) sensor with mercaptopropionic acid (MPA) and glutathione (GSH) functionalization. The sensing response of the sensor was analyzed by detecting Cd2+ ions at different concentrations. The AlGaN/GaN HEMT sensor exhibits excellent response with the sensitivity of $0.241~\mu \text{A}$ /ppb, a fast response time of ~ 3 s, and a lower detection limit of 0.255 ppb. The observed lower detection limit is significantly lower than the World Health Organization (WHO) standard recommended limit for Cd2+ ions in drinking water. Furthermore, the sensor showed good selectivity of Cd2+ ions toward other heavy metal ions. The results indicate that the binding properties of GSH to Cd and the sensitivity of 2-D electron gas toward the variation of charges at the gate region make the device highly sensitive with rapid detection of Cd2+ ions.
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- 2019
9. Linear and Circular AlGaN/AlN/GaN MOS-HEMT-based pH Sensor on Si Substrate: A Comparative Analysis
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Sukant K. Tripathy, Surani Bin Dolmanan, Lava Bhargava, Arathy Varghese, and Chinnamuthan Periasamy
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Materials science ,business.industry ,010401 analytical chemistry ,Conductance ,02 engineering and technology ,Dielectric ,High-electron-mobility transistor ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Si substrate ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Drain current ,Instrumentation ,Sensitivity (electronics) - Abstract
In this article, sensitivity enhancement of undoped AlGaN/AlN/GaN HEMT for pH detection by using dielectric (10 nm Al 2 O 3 )-based MOS-gated structure is demonstrated. Linear and circular MOS-HEMT (L-MOSHEMT and C-MOSHEMT, respectively) with similar dimensions are fabricated on Si substrate. Novel sensing metric gd/IDS (drain conductance to current ratio) is introduced, and C-MOSHEMT attains the highest sensitivity of 1.74 mA/pH and 58 mV -1 /pH when change in drain current (IDS) and gd/IDS are taken as the sensing metrics, respectively.
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- 2019
10. Investigation of Ta2O5 as an Alternative High- <tex-math notation='LaTeX'>${k}$ </tex-math> Dielectric for InAlN/GaN MOS-HEMT on Si
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Sandeep Vura, Sandeep Kumar, Digbijoy N. Nath, Vanjari Sai Charan, Surani Bin Dolmanan, Anamika Singh Pratiyush, Sukant K. Tripathy, Himanshu Kumar, and Rangarajan Muralidharan
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010302 applied physics ,Materials science ,Annealing (metallurgy) ,Analytical chemistry ,High-electron-mobility transistor ,Dielectric ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,X-ray photoelectron spectroscopy ,Sputtering ,0103 physical sciences ,Electrical and Electronic Engineering ,Electronic band structure ,High-κ dielectric - Abstract
We report on the demonstration and investigation of Ta2O5 as high-k dielectric for InAlN/GaN-MOS high-electron mobility transistor (HEMT)-on-Si. Ta2O5 of thickness 24 nm and dielectric constant ~30 was sputter deposited on InAlN/GaN HEMT and was investigated for different post deposition anneal (PDA) conditions. The gate leakage was 16 nA/mm at −15 V which was ~five orders of magnitude lower compared to reference HEMT. The 2-D electron gas (2-DEG) density was found to vary with annealing temperature suggesting the presence of net charge at the Ta2O5/InAlN interface. Dispersion in the capacitance–voltage ( ${C}$ – ${V}$ ) characteristics was used to estimate the frequency-dependent interface charge, while energy band diagrams under flat band conditions were investigated to estimate fixed charge. The optimum anneal condition was found to be 500 °C which has resulted into a flat band voltage spread ( $\Delta {V}_{\text {FB}}$ ) of 0.4 V and interface fix charge ( ${Q} _{\text {f}}$ ) of ${3.98} \times {10}^{{13}}$ cm $^{-2}$ . X-ray photoelectron spectroscopy spectra of as-deposited and annealed Ta2O5film were analyzed for Ta and O compositions in the film. The sample annealed at 500 °C has shown Ta:O ratio of 0.41. X-ray diffraction analysis was done to check the crystallization of amorphous Ta2O5 film at higher annealing temperatures.
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- 2019
11. 1T and 2H heterophase MoS2 for enhanced sensitivity of GaN transistor-based mercury ions sensor
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Nipun Sharma, Adarsh Nigam, Surani Bin Dolmanan, Ankur Gupta, Sudhiranjan Tripathy, and Mahesh Kumar
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Bioengineering ,General Chemistry ,Electrical and Electronic Engineering - Abstract
We report significantly enhanced sensitivity of AlGaN/GaN-based high electron mobility transistor (HEMT) sensor by the targeted synthesis of IT and 2H coexisting phase MoS2 and applying the gate bias voltage. The HEMT structures on Si (111) substrates were used for the detection of Hg2+ ions. The optimum sensitive regime in terms of V GS and V DS of the sensor was investigated by keeping the drain source voltage V DS constant at 2 V and by only varying the gate bias voltage V GS from 0 to 3 V. The strongest sensing response obtained from the device was around 0.547 mA ppb−1 at V GS = 3 V, which is 63.7% higher in comparison to the response achieved at 0 V which shows a sensing response of around 0.334 mA ppb−1. The current response depicts that the fabricated device is very sensitive and selective towards Hg2+ ions. Moreover, the detection limit of our sensor at 3 V was calculated around 6.21 ppt, which attributes to the strong field created between the gate electrode and the HEMT channel due to the presence of 1T metallic phase in synthesized MoS2, indicating that the lower detection limits are achievable in adequate strong fields.
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- 2022
12. Mos2 Functionalized Algan/Gan Transistor Based Room Temperature No2 Gas Sensor
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Nipun Sharma, Sumit Kumar, Ankur Gupta, Surani Bin Dolmanan, Dharmraj Subhash Kotekar Patil, Swee Tiam Tan, Sudhiranjan Tripathy, and Mahesh Kumar
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Metals and Alloys ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Instrumentation ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2021
13. Room-Temperature Patterning of Nanoscale MoS
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Mohammad S M, Saifullah, Mohamed, Asbahi, Maryam, Binti-Kamran Kiyani, Sing Shy, Liow, Surani, Bin Dolmanan, Anna Marie, Yong, Esther A H, Ong, Asadullah, Ibn Saifullah, Hui Ru, Tan, Neeraj, Dwivedi, Tanmay, Dutta, Ramakrishnan, Ganesan, Suresh, Valiyaveettil, Karen S L, Chong, and Sudhiranjan, Tripathy
- Abstract
Molybdenum disulfide (MoS
- Published
- 2020
14. Dielectric Engineering of HfO2 Gate-Stacks for Normally-ON GaN HEMTs on 200-mm Silicon Substrates
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Digbijoy N. Nath, Shreesha Prabhu, Sandeep Kumar, Sangeneni Mohan, Kolla Lakshmi Ganapathi, K. N. Bhat, Rangarajan Muralidharan, Navakanta Bhat, Surani Bin Dolmanan, Sukant K. Tripathy, Srinivasan Raghavan, and Hareesh Chandrasekar
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010302 applied physics ,Materials science ,Condensed matter physics ,Silicon ,Wide-bandgap semiconductor ,chemistry.chemical_element ,Conductance ,Gallium nitride ,02 engineering and technology ,Dielectric ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,01 natural sciences ,Band offset ,Electronic, Optical and Magnetic Materials ,Threshold voltage ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Electrical and Electronic Engineering ,0210 nano-technology - Abstract
We report on the band offset and interfacial electronic properties of e-beam evaporated HfO2 gate dielectrics on III-nitride device stacks on Si. A conduction band offset of 1.9 eV is extracted for HfO2/GaN along with a very low density of fixed bulk and interfacial charges for optimally annealed samples. Normally-ON HfO2/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors exhibit negligible shifts in threshold voltage, transconductances of 120 mS/mm for 3- $\mu \text{m}$ gate length devices, and three-terminal off-state gate leakage currents of 55 nA/mm at a ${V}_{D}$ of 100 V. Dynamic capacitance dispersion measurements in the temperature range of 25 °C–200 °C show two peaks at the AlGaN/GaN interface corresponding to slow and fast interface traps with a peak ${D}_{\text {it}}$ of ${5.5}\times {10}^{13}$ and ${1.5} \times {10}^{13}$ eV−1cm−2 respectively as a function of Fermi level position above ${E}_{C}$ . The HfO2/AlGaN interface exhibits a reasonably constant peak ${D}_{\text {it}}$ of ${2} \times {10}^{13}$ – ${4.4} \times {10}^{13}$ eV−1cm−2 at trap levels of 0.42–0.72 eV below ${E}_{\text {C}}$ . Hysteretic pulsed $I_{D}$ – $V_{G}$ measurements revealed a negative shift in threshold voltages indicative of unoccupied donor-like trap states at the HfO2/AlGaN interface and comparable ${D}_{\text {it}}$ to that inferred from conductance measurements.
- Published
- 2018
15. Ultrasmall Designed Plasmon Resonators by Fused Colloidal Nanopatterning
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Wen-Ya Wu, Mohamed Asbahi, Surani Bin Dolmanan, Zhaogang Dong, Mohammad S. M. Saifullah, Sukant K. Tripathy, Zackaria Mahfoud, Karen S. L. Chong, Michel Bosman, and FuKe Wang
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Materials science ,business.industry ,Electron energy loss spectroscopy ,Nanoparticle ,chemistry.chemical_compound ,chemistry ,Colloidal gold ,Scanning transmission electron microscopy ,Optoelectronics ,General Materials Science ,business ,Lithography ,Hydrogen silsesquioxane ,Plasmon ,Electron-beam lithography - Abstract
This work presents a procedure for large-area patterning of designed plasmon resonators that are much smaller than possible with conventional lithography techniques. Fused Colloidal Nanopatterning combines directed self-assembly and controlled fusing of spherical colloidal nanoparticles. The two-step approach first patterns a surface covered with hydrogen silsesquioxane, an electron beam resist, forming traps into which the colloidal gold nanoparticles self-assemble. Second, the patterned nanoparticles are controllably fused to form plasmon resonators of any 2D designed shape. The heights and widths of the plasmon resonators are determined by the diameter of the nanoparticle building blocks, which can be well below 10 nm. By performing the fusing step with UV ozone and heat exposure, we demonstrate that the process is easily scalable to cover large areas on silicon wafers with designed gold nanostructures. The procedure neither requires adhesion layers nor a lift-off process, making it ideally suited for plasmonics, in comparison with regular electron beam lithography. We use monochromated electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy and boundary element method simulations to demonstrate that the designed plasmon resonators are directly tunable via the pattern design. We foresee future expansion of this approach for applications such as plasmon-enhanced photocatalysis and for large-scale patterning where chemical, optical, or confinement properties require sub-10 nm metal lines.
- Published
- 2019
16. Growth and in-plane undulations of GaAs/Ge superlattices on [001]-oriented Ge and GaAs substrates: formation of regular 3D island-in-network nanostructures
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Xizu Wang, Sukant K. Tripathy, Surani Bin Dolmanan, Ming Lin, Shifeng Guo, Anna Marie Yong, Hongfei Liu, and Yunjiang Jin
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010302 applied physics ,Diffraction ,Nanostructure ,Materials science ,Condensed matter physics ,Superlattice ,02 engineering and technology ,General Chemistry ,Chemical vapor deposition ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Condensed Matter::Materials Science ,Lattice constant ,0103 physical sciences ,Thermoelectric effect ,Materials Chemistry ,0210 nano-technology ,Spectroscopy - Abstract
Coherently strained pseudo-superlattices (PSLs) of 20-period GaAs/Ge have been epitaxially grown on [001]-oriented Ge and GaAs substrates by metalorganic chemical vapor deposition. High-resolution X-ray diffraction and dynamic simulation revealed an increase in the growth rate of Ge (RGe) and a decrease in that of GaAs (RGaAs) when GaAs is used, instead of Ge, as the substrate under otherwise the same growth conditions. They also revealed an increase in RGe while a decrease in RGaAs when the growth temperature is increased. These changes are related to atomic intermixing at the interfaces that resulted in interfacial (GaAs)1−xGex alloys with lattice constants larger than that calculated assuming Vegard's law. Cross-sectional transmission-electron microscopy revealed regular in-plane undulations of the PSLs and energy-dispersive X-ray spectroscopy provided evidence that the Ge sublayers were conformally grown on GaAs while the GaAs sublayers were grown in isolated islands that initiated in the valleys of the Ge sublayers. The growth mechanism was interpreted based on surface chemical potentials that depend on the balance between the surface-energy and the local strain-relaxation energy. The three-dimensional periodic island-in-network nanostructures, as well as their optical and lattice dynamical properties, are of great importance not only for fundamental studies but also for fabricating thermoelectric devices.
- Published
- 2018
17. Interface traps at Al 2 O 3 /InAlN/GaN MOS-HEMT -on- 200 mm Si
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Sukant K. Tripathy, Digbijoy N. Nath, Srinivasan Raghavan, Nayana Remesh, Surani Bin Dolmanan, Sandeep Kumar, and Rangarajan Muralidharan
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010302 applied physics ,Materials science ,Silicon ,business.industry ,Time constant ,Conductance ,chemistry.chemical_element ,02 engineering and technology ,High-electron-mobility transistor ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Acceptor ,Electronic, Optical and Magnetic Materials ,Threshold voltage ,chemistry ,0103 physical sciences ,Trap density ,Materials Chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Dispersion (chemistry) - Abstract
We report on the characterization of the interfaces of Al2O3/InAlN/GaN HEMT structure grown on 200 mm diameter silicon using conductance dispersion technique. Irreversible threshold voltage (VTH) shift of up to +similar to 2.5 V was observed due to the gate stress induced activation of acceptor states. Further, frequency dependent VTH shift during capacitance voltage measurements were also recorded due to the presence of slow traps at InAlN/GaN interface. The conductance dispersion indicated the presence of acceptor traps of the order of similar to 4 x 10(12) to 7 x 10(13) cm(-2) eV(-1) with a time constant of similar to 10 to 350 ls at the InAlN/GaN interface. Trap density at the Al2O3/InAlN was found to be in similar range but with a time constant of similar to 2 ms. The presence of high density of traps at InAlN/GaN interface is attributed to the unavoidable growth interruption before the start of InAlN growth. (C) 2017 Elsevier Ltd. All rights reserved.
- Published
- 2017
18. Temperature dependent lattice expansions of epitaxial GaN-on-Si heterostructures characterized by in- and ex-situ X-ray diffraction
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Suo Hon Lim, Surani Bin Dolmanan, Hongfei Liu, and Shi Wun Tong
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Materials science ,Mechanical Engineering ,Metals and Alloys ,Analytical chemistry ,Heterojunction ,02 engineering and technology ,Chemical vapor deposition ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Mechanics of Materials ,X-ray crystallography ,Materials Chemistry ,Wafer ,Metalorganic vapour phase epitaxy ,0210 nano-technology - Abstract
In-situ X-ray diffraction (XRD), with the sample temperature stepwise increased up to 900 °C, together with ex-situ high-resolution XRD (HRXRD), has been used to study the lattice expansion along the surface normal direction of GaN-on-Si heterostructures grown by metalorganic chemical vapor deposition (MOCVD). The thermal stabilities induced by step-graded (SG) AlxGa1−xN/AlN and multiple low-temperature (MLT) AlN buffer layers have been addressed for the heterostructures grown on 700 and 1500 µm thick Si (111) wafers, respectively. It reveals that the thermal expansion of the GaN epilayer is slightly larger than that of the Si substrate and the nitride growth tends to decrease the thermal expansion of the Si (111) wafer at lower temperatures. Onset of drop in the lattice expansions has been observed when the temperature is increased to a transition point, Ttr, and the Ttr of the MLT-AlN buffered GaN on the 1500 µm thick Si is ~500 °C, which is apparently lower than that of the SG-AlxGa1−xN/AlN buffered GaN on the 700 µm thick Si. These observations have been interpreted and attributed to convolutions among the residual lattice strains, their relaxations, and the thermal expansion coefficient mismatch induced wafer curvatures (opposite to that during MOCVD growth) at elevated temperatures.
- Published
- 2021
19. Comparison of the AlxGa1–xN/GaN Heterostructures Grown on Silicon-on-Insulator and Bulk-Silicon Substrates
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Wai Hoe Tham, Thirumaleshwara N. Bhat, Lakshmi Kanta Bera, Vivian Kaixin Lin, Diing Shenp Ang, Surani Bin Dolmanan, and Sukant K. Tripathy
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010302 applied physics ,Materials science ,Silicon ,business.industry ,Wide-bandgap semiconductor ,chemistry.chemical_element ,Silicon on insulator ,Gallium nitride ,Heterojunction ,02 engineering and technology ,High-electron-mobility transistor ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Overlayer ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Optoelectronics ,Wafer ,Electrical and Electronic Engineering ,0210 nano-technology ,business - Abstract
Compared with bulk-Si wafer, Al x Ga1– x N/gallium nitride (GaN) heterostructures grown on a 150-mm silicon-on-insulator (SOI) substrate with a 35-nm-thick Si overlayer are shown to have $\sim 50$ % less wafer bowing. As a result, the 2-D electron gas mobility and the sheet-resistivity uniformity on SOI are improved due to a lower defect density. In terms of device performance, high-electron-mobility transistors (HEMTs) fabricated on the Al x Ga1– x N/GaN-on-SOI exhibit $\sim 20.5$ % higher saturation drain current as compared with the bulk-Si counterparts. However, due to the poorer conductivity of the buried oxide layer, the Al x Ga1– x N/GaN-on-SOI HEMT suffers greater self-heating, with $\sim 50$ K higher channel temperature. With mitigation of self-heating, the Al x Ga1– x N/GaN-on-SOI, in view of its more superior structural and thermal stability, should offer an attractive alternative for integration of the GaN technology with the Si CMOS platform.
- Published
- 2016
20. Real time detection of Hg2+ ions using MoS2 functionalized AlGaN/GaN high electron mobility transistor for water quality monitoring
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Mahesh Kumar, Adarsh Nigam, Neeraj Goel, Thirumaleshwara N. Bhat, Surani Bin Dolmanan, Sukant K. Tripathy, Md. Tawabur Rahman, and Qiquan Qiao
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Diffraction ,Materials science ,Scanning electron microscope ,02 engineering and technology ,High-electron-mobility transistor ,010402 general chemistry ,01 natural sciences ,Ion ,chemistry.chemical_compound ,symbols.namesake ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Molybdenum disulfide ,Detection limit ,business.industry ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Linear range ,symbols ,Optoelectronics ,0210 nano-technology ,business ,Raman spectroscopy - Abstract
A sensor for highly sensitive, selective, and rapid determination of the trace amount of toxic Hg2+ ions is developed for the first-time using molybdenum disulfide (MoS2) functionalized AlGaN/GaN high electron mobility transistor (HEMT). The vertically aligned, flower-like MoS2 structures are synthesized through a simple hydrothermal route and applied on the gate region of AlGaN/GaN HEMT. The scanning electron microscopy, Raman spectroscopy, and X-ray diffraction are performed for structural characterization of MoS2. Further, the sensing of Hg2+ ions is performed by electrical characterizations of MoS2 functionalized AlGaN/GaN HEMT. The sensor showed an excellent sensitivity of 0.64 μA/ppb and detection limit of 0.01152 ppb with the rapid response time of 1.8 s. The sensor exhibits the linear range of detection from 0.1 ppb to 100 ppb and highly selective behavior towards Hg2+ ions. The results demonstrated that the MoS2 possess excellent Hg2+ ions capture property, that could be attributed to the complexation of Hg2+ ions with sulfur and the electrostatic interaction between MoS2 and Hg2+ ions alters the drain to source current (IDS) of the HEMT at a constant drain to source voltage (VDS). Therefore, the MoS2 based AlGaN/ GaN HEMT devices have a huge potential for next-generation ion sensing applications.
- Published
- 2020
21. Meandering Gate Edges for Breakdown Voltage Enhancement in AlGaN/GaN High Electron Mobility Transistors
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Digbijoy N. Nath, Surani Bin Dolmanan, Sandeep Kumar, Sukant K. Tripathy, and Rangarajan Muralidharan
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010302 applied physics ,Materials science ,business.industry ,Algan gan ,02 engineering and technology ,Surfaces and Interfaces ,High-electron-mobility transistor ,Edge (geometry) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,On resistance ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Electric field ,0103 physical sciences ,Materials Chemistry ,Optoelectronics ,Figure of merit ,Breakdown voltage ,Electrical and Electronic Engineering ,0210 nano-technology ,business - Abstract
In this letter, we report on a unique device design strategy for increasing the breakdown voltage and hence Baliga Figure of Merit (BFOM) of III-nitride HEMTs by engineering the gate edge towards the drain. The breakdown of such devices with meandering gate-drain access region (M-HEMT) are found to be 62% more compared to that of conventional HEMT while the ON resistance suffers by 76%, leading to an overall improvement in the BFOM for by 28%. 3D-TCAD simulations show that the decrease in the peak electric field at the gate edge was responsible for increased breakdown voltage.
- Published
- 2020
22. Deep Submicron Normally Off AlGaN/GaN MOSFET on Silicon with V TH > 5V and On‐Current > 0.5 A mm −1
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Digbijoy N. Nath, Rangarajan Muralidharan, Sandeep Kumar, Surani Bin Dolmanan, Sukant K. Tripathy, and Sandeep Vura
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Materials science ,Silicon ,business.industry ,chemistry.chemical_element ,Algan gan ,Normally off ,Surfaces and Interfaces ,High-electron-mobility transistor ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,MOSFET ,Materials Chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,Current (fluid) ,business - Published
- 2020
23. UV Detector based on InAlN/GaN-on-Si HEMT Stack with Photo-to-Dark Current Ratio > 107
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Digbijoy N. Nath, Sukant K. Tripathy, Surani Bin Dolmanan, Sandeep Kumar, Rangarajan Muralidharan, and Anamika Singh Pratiyush
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010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,Silicon ,business.industry ,Wide-bandgap semiconductor ,Photodetector ,chemistry.chemical_element ,02 engineering and technology ,Carrier lifetime ,High-electron-mobility transistor ,Physics - Applied Physics ,021001 nanoscience & nanotechnology ,01 natural sciences ,chemistry ,Stack (abstract data type) ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Ohmic contact ,Dark current - Abstract
We demonstrate an InAlN/GaN-on-Si HEMT based UV detector with photo to dark current ratio > 107. Ti/Al/Ni/Au metal stack was evaporated and rapid thermal annealed for Ohmic contacts to the 2D electron gas (2DEG) at the InAlN/GaN interface while the channel + barrier was recess etched to a depth of 20 nm to pinch-off the 2DEG between Source-Drain pads. Spectral responsivity (SR) of 34 A/W at 367 nm was measured at 5 V in conjunction with very high photo to dark current ratio of > 10^7. The photo to dark current ratio at a fixed bias was found to be decreasing with increase in recess length of the PD. The fabricated devices were found to exhibit a UV-to-visible rejection ratio of >103 with a low dark current < 32 pA at 5 V. Transient measurements showed rise and fall times in the range of 3-4 ms. The gain mechanism was investigated and carrier lifetimes were estimated which matched well with those reported elsewhere., Comment: 12 pages
- Published
- 2017
24. Silicon Nitride Thickness Dependent Electrical Properties of InAlN/GaN Heterostructures
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Surani Bin Dolmanan, Milan Kumar Bera, Eng Fong Chor, Yi Jie Ngoo, Sarab Preet Singh, Lwin Min Kyaw, Yi Liu, and Sukant K. Tripathy
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Thickness dependent ,chemistry.chemical_compound ,Materials science ,Silicon nitride ,chemistry ,business.industry ,Optoelectronics ,Heterojunction ,business - Abstract
Introduction Lattice-matched InAlN/GaN/Si based high electron mobility transistors (HEMTs) have recently attracted much attention as a candidate for next generation high-power, high-temperature and high-frequency devices, due to their higher charge density than the conventional AlGaN/GaN heterostructure [1]. However, HEMT performance, reliability, integrity and robustness are determined by the contact materials employed and passivation. Various dielectrics, such as SiO2, Si3N4, AlN, MgO, Al2O3, HfO2, Sc2O3, etc have been investigated for passivation. Among them, Si3N4 is the most widely used. Extensive improvement in electrical properties of the AlGaN/GaN/Si heterostructure achieved by the SiN x passivation process has been reported [2]. Such improvements by SiN x passivation were believed to be due to the reduction of the surface states, change in the AlGaN potential barrier height or increase of the 2DEG density at the channel due to tensile stress [3-5]. In spite of various reports on SiN x pasivation of InAlN/GaN heterostructures, SiN x thickness dependent studies have not been extensively explored to date. In the present study, we report SiN x thickness dependent electrical properties and its effect on the device performance of InAlN/GaN heterostructures. Experiment Nearly lattice-matched InAlN/GaN/Si epi-wafer, with a sheet resistance of 348.9 Ω/sq, was used in the present study. Prior to ohmic contact formation, InAlN/GaN/Si substrate surface was ultrasonically cleaned with acetone, IPA and DI water. Hf (15)/Al (200)/Ta (20) nm ohmic contacts were deposited by sputtering followed by rapid thermal annealing in vacuum at 600 oC for 1 min. No surface treatment was performed prior to passivation. Passivation SiN x layer of varying thickness ranging from 25 to 200 nm was deposited at 300°C by PECVD using silane and ammonia as precursor gases. SiN x layer on the ohmic electrodes was removed by etching in buffered hydrofluoric acid. To characterize our samples, room-temperature Hall measurements using van der Pauw geometry and ultraviolet (UV) Photoluminescence (PL) spectra excited using 266 nm laser source were performed. Results and Discussion Figure 1 shows the room-temperature Hall measurements of InAlN/GaN/Si as a function of the passivation SiN x layer thickness. Increase in sheet carrier concentration (ns), whereas decrease in mobility (μ) is observed with increasing SiN x passivation layer thickness. A thickness of ~100 nm can be viewed as optimum as it yields a minimum sheet resistance (Rs), as shown in Fig. 1. The corresponding increase in ns is substantial of almost ~30%, with respect to sample without SiN x passivation. Although the reason for the significant increase in ns is not apparent, yet our preliminary studies by means of UV PL reveal a shift in the PL peak position of the GaN channel layer (Fig. 2), which is most likely due to band bending under stress. However, possibility of reduction of surface states of the passivated InAlN and/or an increase in positive charge at the SiN x /InAlN interface cannot be ruled out. Additionally, the decrease in μ is possibly due to increased electron-electron scattering and/or interface roughness scattering with such a high carrier concentration in 2DEG channel. Interestingly, the trend of increase in 2DEG density is similar to that observed for AlGaN/GaN heterostructure under different SiN x passivation layer thickness [6]. This observation indicates that the intrinsic property of SiN x film may be playing a critical role in the enhancement of 2DEG density rather than the interface property. Further studies to establish the mechanisms responsible for the enhancement in 2DEG density as well as to evaluate the influence of passivation layer thickness on the device performance are in progress. Conclusion In conclusion, surface passivation of InAlN/GaN heterostructures with PECVD SiN x of varying thickness has been investigated. A thickness of ~ 100 nm is found to be optimum and has yielded a minimum sheet resistance. The corresponding 2DEG density change is substantially higher (by ~30 %) than sample without SiN x passivation, and this enhancement is attributed possibly to band bending under stress. References [1] A. Dadgar, F. Schulze, J. Bläsing, A. Diez, A. Krost, M. Neuburger, E. Kohn, I. Daumiller and M. Kunze, Appl. Phys. Lett. 85, 5400 (2004). [2] J. Bernát, P. Javorka, A. Fox, M. Marso, H. Lüth and P.Kordoš, Solid-State Electronics 47, 2097 (2003). [3] A. V. Vertiachikh, L. F. Eastman, W. J. Schaff and T. Prunty, Electron. Lett. 38, 388 (2002). [4] C. M. Jeon and J. Lee, Appl. Phys. Lett. 86, 172101 (2005). [5] N. Onojima, M. Higashiwaki, J. Suda, T. Kimoto, T. Mimura and T. Matsui, J. Appl. Phys. 101, 043703 (2007). [6] I. R. Gatabi, D. W. Johnson, J. H. Woo, J. W. Anderson, M. R. Coan, E. L. Piner and H. R. Harris, IEEE Transactions on Electron Devices, 60, 3, (2013).
- Published
- 2014
25. Solar water oxidation in sputter-deposited nanocrystalline WO3 photoanodes via tuning of Ar:O2 flow rate combinations
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Wei Wang, Siao Li Liew, Surani Bin Dolmanan, Glen Tai Wei Goh, and Dongzhi Chi
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Photocurrent ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,Electrolyte ,Condensed Matter Physics ,Oxygen ,Nanocrystalline material ,Volumetric flow rate ,chemistry ,Sputtering ,General Materials Science ,Thin film ,Monoclinic crystal system - Abstract
Thin film WO 3 photoanodes were prepared by reactive sputtering in Ar and O 2 gas mixtures of various flow rate combinations. Furnace annealed films were nanocrystalline monoclinic WO 3 with (002), (020) and (200) plane orientations. Water oxidation in 0.33 M H 2 SO 4 electrolyte under simulated solar illumination showed that photoanodes deposited in highest Ar and O 2 flow rate combinations exhibited highest photocurrent of 4.1 mA cm −2 (at 1.3 V vs Ag/AgCl) compared to 3–3.8 mA cm −2 for photoanodes deposited in lower flow rate combinations. The higher photocurrents were ascribed to lower bulk resistivity and charge transfer resistance at the WO 3 /electrolyte interface. These photoanodes consisted of randomly oriented (002), (020) and (200) planes in contrast to the preferentially orientated (002) and (200) planes of photoanodes which were highly resistive with poorer photocurrent responses. These results were interpreted in terms of the effects of Ar:O 2 flow rate combinations on the distribution of oxygen vacancies and formation of crystallographic shear planes in the sputtered films.
- Published
- 2014
26. Origin and Quenching of Novel ultraviolet and blue emission in NdGaO3: Concept of Super-Hydrogenic Dopants
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Weiming Lü, Zhen Huang, Mallikarjuna Rao Motapothula, Thirumaleshwara Bhatt, Saurav Prakash, Sukant K. Tripathy, Xiaohu Huang, Ariando Ariando, Mark Asta, Thirumalai Venkatesan, Nikolai Yakovlev, Chunxiao Cong, Surani Bin Dolmanan, Zhiqi Liu, Surajit Saha, Soo Jin Chua, Ting Yu, Abhijeet Patra, Siddhartha Ghosh, Chuan Beng Tay, Jianqiang Chen, and Yao Cai
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Quenching ,Multidisciplinary ,Photoluminescence ,Materials science ,Dopant ,Doping ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Article ,Ion ,Other Physical Sciences ,X-ray photoelectron spectroscopy ,0103 physical sciences ,Biochemistry and Cell Biology ,010306 general physics ,0210 nano-technology ,Bohr radius ,Perovskite (structure) - Abstract
In this study we report the existence of novel ultraviolet (UV) and blue emission in rare-earth based perovskite NdGaO3 (NGO) and the systematic quench of the NGO photoluminescence (PL) by Ce doping. Study of room temperature PL was performed in both single-crystal and polycrystalline NGO (substrates and pellets) respectively. Several NGO pellets were prepared with varying Ce concentration and their room temperature PL was studied using 325 nm laser. It was found that the PL intensity shows a systematic quench with increasing Ce concentration. XPS measurements indicated that nearly 50% of Ce atoms are in the 4+ state. The PL quench was attributed to the novel concept of super hydrogenic dopant (SHD)”, where each Ce4+ ion contributes an electron which forms a super hydrogenic atom with an enhanced Bohr radius, due to the large dielectric constant of the host. Based on the critical Ce concentration for complete quenching this SHD radius was estimated to be within a range of 0.85 nm and 1.15 nm whereas the predicted theoretical value of SHD radius for NdGaO3 is ~1.01 nm.
- Published
- 2016
27. Influence of RuOx Gate Thermal Annealing on Electrical Characteristics of AlxGa1-xN/GaN HEMTs on 200-mm Silicon
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Eng Fong Chor, Thirumaleshwara N. Bhat, Yi Liu, Surani Bin Dolmanan, Milan Kumar Bera, Hui Ru Tan, Sukant K. Tripathy, Y. Dikme, and Lwin Min Kyaw
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Materials science ,Silicon ,chemistry ,business.industry ,Optoelectronics ,chemistry.chemical_element ,Electrical and Electronic Engineering ,business ,Electronic, Optical and Magnetic Materials - Published
- 2013
28. Efficiency Optimization on Dye-Sensitized Solar Cells With Low-Frequency Noise Analysis
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Szu Cheng Lai, Lin Ke, Surani Bin Dolmanan, Xiao Wei Sun, and Ming Fei Yang
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Materials science ,business.industry ,Photoconductivity ,Infrasound ,Zinc compounds ,Noise (electronics) ,Electronic, Optical and Magnetic Materials ,law.invention ,Dye-sensitized solar cell ,law ,Sufficient time ,Solar cell ,Optoelectronics ,Nanorod ,Electrical and Electronic Engineering ,business - Abstract
The effects of time durations for ZnO nanorod growth and dye loading on a ZnO-based dye-sensitized solar cell's efficiency and 1/f low-frequency noise (LFN) spectral were analyzed. Sufficient time durations for ZnO growth and dye loading were required for achieving optimum photoconversion efficiency. Extending these two time parameters beyond the optimal, however, reduced the efficiency due to nanorod defects and dye agglomerations. The mechanisms inducing the change in the efficiency was reflected in the LFN spectral and explained on the basis of Kleinpenning's noise equation and excessive noises in the presence of structural defects.
- Published
- 2010
29. Degradation mechanism of ZnO-based dye-sensitized solar cells
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Lu Shen, Surani Bin Dolmanan, Hong Liu, Zheng Zhang, Doreen Mei Ying Lai, Lin Ke, and Pramoda Kumari Pallathadk
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Photocurrent ,Absorption spectroscopy ,Renewable Energy, Sustainability and the Environment ,Chemistry ,technology, industry, and agriculture ,Analytical chemistry ,Infrared spectroscopy ,Electrolyte ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Dye-sensitized solar cell ,Chemical engineering ,X-ray photoelectron spectroscopy ,law ,Solar cell ,Nanorod - Abstract
Zinc oxide (ZnO)-based dye-sensitized solar cell was fabricated and tested under constant solar simulator illumination until the photocurrent decreased. Electrolyte and dye were studied by Fourier transform infrared and UV–vis absorption spectroscopy. Scanning electron microscopy, photoluminescence and X-ray photoelectron spectroscopy were used to study the degradation of ZnO. Secondary Ion Mass spectroscopy was used to analyze the structural change of the device during the degradation process. The degradation process of dye-sensitized solar cell is started when N3 dye slowly gets desorbed from the ZnO surface and gets incorporated into the electrolyte. Electron injection decreases with time as more dye gets desorbed. The degradation process is further accelerated when ions of Zn, O and In are diffused into the electrolyte as this process create defect vacancies on the ZnO nanorod surface. The stability of the semiconductor surface and interface between the semiconductor and dye are crucial to improve device lifetime.
- Published
- 2010
30. Improved Photoelectrochemical Cell With Carbon Nanotubes
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Surani Bin Dolmanan, Wei Wei Loh, Zhi Hui Jiao, Szu Cheng Lai, Xiao Wei Sun, and Lin Ke
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Materials science ,Nanoparticle ,chemistry.chemical_element ,Nanotechnology ,Carbon nanotube ,Photoelectrochemical cell ,Electronic, Optical and Magnetic Materials ,Titanium oxide ,Indium tin oxide ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Titanium dioxide ,Electrode ,Electrical and Electronic Engineering ,Titanium - Abstract
Single-walled carbon nanotubes (SWCNTs) were incorporated into a dye-sensitized titanium dioxide (TiO2)-based photoelectrode and characterized in a conventional three-arm system for water photolysis. Improvements in short-circuit current, efficiency, and lifetime were observed in the presence of an increase in SWCNT concentration at the TiO2-ITO (back-electrode) interface. The mechanism behind these improvements was explained on the basis of the SWCNTs acting as a conductive scaffolding network responsible for anchoring the TiO2 and transporting the photoelectrons to the back electrode.
- Published
- 2010
31. Design and synthesis of polymer-functionalized NIR fluorescent dyes--magnetic nanoparticles for bioimaging
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Surani Bin Dolmanan, Yong Zhang, Anushya Hariharan, Dominik Jańczewski, Vincent H.B. Ho, Sukant K. Tripathy, Thankiah Sudhaharan, Vimalan Vijayaragavan, Subramanian Tamil Selvan, Kishore Bhakoo, Sohail Ahmed, Swee Kuan Yen, Jeeva Lavanya Lakshmi, and Parasuraman Padmanabhan
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Indocyanine Green ,Materials science ,Polymers ,General Physics and Astronomy ,Contrast Media ,Nanotechnology ,Ethylenediamine ,Biocompatible Materials ,Photochemistry ,symbols.namesake ,chemistry.chemical_compound ,Magnetics ,Mice ,Stokes shift ,Animals ,Humans ,General Materials Science ,Cyanine ,Coloring Agents ,Fluorescent Dyes ,chemistry.chemical_classification ,Spectroscopy, Near-Infrared ,technology, industry, and agriculture ,General Engineering ,Polymer ,equipment and supplies ,Fluorescence ,chemistry ,Microscopy, Fluorescence ,Quantum dot ,Spectrophotometry ,symbols ,Surface modification ,Magnetic nanoparticles ,Nanoparticles ,Spectrophotometry, Ultraviolet ,HeLa Cells - Abstract
The fluorescent probes having complete spectral separation between absorption and emission spectra (large Stokes shift) are highly useful for solar concentrators and bioimaging. In bioimaging application, NIR fluorescent dyes have a greater advantage in tissue penetration depth compared to visible-emitting organic dyes or inorganic quantum dots. Here we report the design, synthesis, and characterization of an amphiphilic polymer, poly(isobutylene-alt-maleic anhyride)-functionalized near-infrared (NIR) IR-820 dye and its conjugates with iron oxide (Fe3O4) magnetic nanoparticles (MNPs) for optical and magnetic resonance (MR) imaging. Our results demonstrate that the Stokes shift of unmodified dye can be tuned (from ~106 to 208 nm) by the functionalization of the dye with polymer and MNPs. The fabrication of bimodal probes involves (i) the synthesis of NIR fluorescent dye (IR-820 cyanine) functionalized with ethylenediamine linker in high yield,90%, (ii) polymer conjugation to the functionalized NIR fluorescent dye, and (iii) grafting the polymer-conjugated dyes on iron oxide MNPs. The resulting uniform, small-sized (ca. 6 nm) NIR fluorescent dye-magnetic hybrid nanoparticles (NPs) exhibit a wider emissive range (800-1000 nm) and minimal cytotoxicity. Our preliminary studies demonstrate the potential utility of these NPs in bioimaging by means of direct labeling of cancerous HeLa cells via NIR fluorescence microscopy and good negative contrast enhancement in T2-weighted MR imaging of a murine model.
- Published
- 2013
32. Gold-free contacts on AlxGa1-xN/GaN high electron mobility transistor structure grown on a 200-mm diameter Si(111) substrate
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Siew Lang Teo, Lakshmi Kanta Bera, Surani Bin Dolmanan, Diing Shenp Ang, Thirumaleshwara N. Bhat, R. S. Kajen, Wai Hoe Tham, Hui Ru Tan, Sukant K. Tripathy, and School of Electrical and Electronic Engineering
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Fabrication ,Materials science ,Annealing (metallurgy) ,02 engineering and technology ,High-electron-mobility transistor ,01 natural sciences ,law.invention ,Electrical resistivity and conductivity ,law ,0103 physical sciences ,Aluminium ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Ohmic contact ,010302 applied physics ,Electrical Resistivity ,business.industry ,Process Chemistry and Technology ,Contact resistance ,Transistor ,Wide-bandgap semiconductor ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Engineering::Electrical and electronic engineering [DRNTU] ,Optoelectronics ,0210 nano-technology ,business - Abstract
The authors report on the fabrication and characterization of low-temperature processed gold-free Ohmic contacts for AlxGa1−xN/GaN high electron mobility transistors (HEMTs). The HEMT structure grown on a 200-mm diameter Si(111) substrate is used in this study. Using the Ti/Al/NiV metal stack scheme, the source/drain Ohmic contact optimization is accomplished through the variation of Ti/Al thickness ratio and thermal annealing conditions. For an optimized Ti/Al stack thickness (20/200 nm) annealed at 500 °C for 30 s with smooth contact surface morphology, a specific contact resistivity of ∼6.3 × 10−6 Ω cm2 is achieved. Furthermore, with gold-free Ni/Al gates, the fabricated HEMTs exhibit ION/IOFF ratio of ∼109 and a subthreshold swing of ∼71 mV/dec. The demonstrated gold-free contact schemes thus provide a solution toward the implementation of GaN-based HEMT process on a Si foundry platform. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version
- Published
- 2016
33. Synthesis and characterization of fluorescent dyes-magnetic nanoparticles for bioimaging applications
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Dominik Jańczewski, Swee Kuan Yen, Subramanian Tamil Selvan, Surani Bin Dolmanan, and Tripathy Sudhiranjan
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chemistry.chemical_classification ,Aqueous solution ,Nanoparticle ,Nanotechnology ,Polymer ,Conjugated system ,equipment and supplies ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Magnetic nanoparticles ,Viability assay ,Cyanine ,human activities - Abstract
Magnetic-fluorescent nanoparticles have been emerging as potential bimodal probes in the area of bioimaging. However, near-infrared (NIR) fluorescent dye as a fluorescent material for bimodal probe remains unexplored. The tailor-design of NIR cyanine dye is challenging. Herein, we report the synthesis and characterization of novel functional IR 820 dye. This modified IR 820 has been successfully conjugated with long and short back-bone chain polymers. All these compounds preserve good water solubility and photochemical properties. The magnetic-fluorescent bimodal probe has been demonstrated, wherein the magnetic nanoparticles have been coated with dye-polymer. The cytotoxicity studies on HeLa cells show that MNP@dye-polymer with short back-bone chain has better cell viability.
- Published
- 2012
34. Morphological dependance of charge transport in nanostructured ZnO-based dye sensitized solar cells
- Author
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Vijila Chellappan, Jia Xing Lee, A. Sreekumaran Nair, Surani Bin Dolmanan, Karen Ke Lin, Seeram Ramakrishna, Mein Jin Tan, Liu Bin, Naveen Kumar Elumalai, Saudi International Electronics, Communications and Photonics Conference (SIECPC) Riyadh, Saudi Arabia 24-26 April 2011, Elumalai, Naveen Kumar, Tan, MJ, Lee, JX, Dolmanan, S, Link, Karl K, Bin, L, Nair, AS, Chellappan, V, and Ramakrishna, S
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Photocurrent ,Materials science ,business.industry ,Photoconductivity ,Photovoltaic system ,Energy conversion efficiency ,Wide-bandgap semiconductor ,Light scattering ,Dye-sensitized solar cell ,dye sensitized solar cells ,Optoelectronics ,Nanorod ,electron transport ,diffusion coefficient ,business - Abstract
Zinc oxide (ZnO) photoanodes of two different morphologies - nanorods and nanosheets are used to fabricate dye sensitised solar cells in order to study the influence of morphology on device performance. Characteristics such as dye loading capacity and light scattering ability of the photoanodes depend on the morphology to a large extent. This leads to change in the electron transport properties, which in turn affects power conversion efficiency. Here we report the difference in the charge transport properties of these morphologies evaluated using the time resolved photocurrent measurements. The photocurrent transients for ZnO nano-rod film exhibited dual peak behaviour, whereas transients for ZnO nano-sheet film exhibited only one peak as the time delayed second peak corresponding to slow electron diffusion was totally suppressed. The transient photocurrent decay also indicates that the charge transport rate is much faster in the ZnO nano-sheets, which allows the efficient charge collection over much larger thickness compared to other ZnO nano-rod film. The power conversion efficiency (PCE) of the devices was found to be 1.6% and 1.5 % for the ZnO-nano-rod and nano-sheet based dye sensitized solar cells respectively. A comparative study is performed and the photovoltaic parameters obtained in each case are correlated with the photocurrent transients enabling better understanding of the impact of morphology. Refereed/Peer-reviewed
- Published
- 2011
35. Light emission from tensile-strained n-type epitaxial Ge thin films on Si by ultrahigh vacuum chemical vapor deposition
- Author
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Mingbin Yu, Andy En-Jin Lim, Surani Bin Dolmanan, L. Ding, Guo-Qiang Lo, and Sukant K. Tripathy
- Subjects
Materials science ,Photoluminescence ,Vacuum deposition ,Dopant ,business.industry ,Annealing (metallurgy) ,Optoelectronics ,Light emission ,Chemical vapor deposition ,Thin film ,Dopant Activation ,business - Abstract
Recently, Ge has been intensively studied as a light emission material that emits at ∼1.5 μm, as it has been theoretically proven to be a promising candidate to realize Si-based light source for on-chip and chip-to-chip communications. In this paper, photoluminescence (PL) is reported from heavily phosphorus (P)-implanted epitaxial Ge thin films on Si. Sheet resistance has been measured to characterize the dopant concentration in Ge. X-ray diffraction (XRD) and micro-Raman spectroscopy have been employed to investigate the Ge crystalline quality and film strain, which are both important factors of light emission efficiency of Ge epilayer on Si. Thermal annealing effect on dopant activation, tensile-strain, and PL has been investigated. It is found that the annealing temperature of 700 °C gives the most effective dopant activation, in-plane tensile strain of 0.4%, and high crystalline quality, leading to strongest PL emission.
- Published
- 2010
36. Channel temperature measurements of InxAl1−xN/GaN high electron mobility transistors on Si(111) using optical spectroscopy
- Author
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Surani Bin Dolmanan, Thirumaleshwara N. Bhat, Yi Liu, Sukant K. Tripathy, Eng Fong Chor, Hui Ru Tan, Lakshmi Kanta Bera, and Lwin Min Kyaw
- Subjects
Photoluminescence ,Materials science ,business.industry ,Process Chemistry and Technology ,Schottky barrier ,Wide-bandgap semiconductor ,Substrate (electronics) ,High-electron-mobility transistor ,Epitaxy ,Temperature measurement ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Materials Chemistry ,symbols ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Raman spectroscopy ,Instrumentation - Abstract
The temperature profiles of InxAl1−xN/GaN high electron mobility transistors (HEMTs) were investigated using nondestructive optical spectroscopic techniques. In this study, HEMT structures were epitaxially grown on a Si(111) substrate with a diameter of 200 mm. In particular, the channel temperature underneath the gate was able to be accurately probed by using a RuOx-based semitransparent Schottky contact in the ultraviolet photoluminescence (PL) and visible Raman excitation modes. A maximum channel temperature as high as ∼475 K was probed near the gate edge using the PL technique at a power dissipation of ∼11.6 W/mm, thus leading to a minimum thermal conductance of about 64.7 Wm−1K−1 in such a HEMT structure. Furthermore, the temperature profiles at the GaN buffer and AlN/Si(111) interface were determined using micro-Raman measurements.
- Published
- 2015
37. Record-low contact resistance for InAlN/AlN/GaN high electron mobility transistors on Si with non-gold metal
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Chandra Mohan Manoj Kumar, S. C. Foo, Sukant K. Tripathy, K. Ranjan, Geok Ing Ng, Thirumaleshwara N. Bhat, Kian Siong Ang, S. Vicknesh, Subramaniam Arulkumaran, and Surani Bin Dolmanan
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Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Transconductance ,Transistor ,Contact resistance ,General Engineering ,General Physics and Astronomy ,Cutoff frequency ,law.invention ,Root mean square ,law ,Etching ,Surface roughness ,Optoelectronics ,business ,Ohmic contact - Abstract
We have demonstrated 0.17-µm gate-length In0.17Al0.83N/GaN high-electron-mobility transistors (HEMTs) on Si(111) substrates using a non-gold metal stack (Ta/Si/Ti/Al/Ni/Ta) with a record-low ohmic contact resistance (Rc) of 0.36 Ω mm. This contact resistance is comparable to the conventional gold-based (Ti/Al/Ni/Au) ohmic contact resistance (Rc = 0.33 Ω mm). A non-gold ohmic contact exhibited a smooth surface morphology with a root mean square surface roughness of ~2.1 nm (scan area of 5 × 5 µm2). The HEMTs exhibited a maximum drain current density of 1110 mA/mm, a maximum extrinsic transconductance of 353 mS/mm, a unity current gain cutoff frequency of 48 GHz, and a maximum oscillation frequency of 66 GHz. These devices exhibited a very small (
- Published
- 2015
38. Structural and optical properties of AlxGa1−xN/GaN high electron mobility transistor structures grown on 200 mm diameter Si(111) substrates
- Author
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Hui R. Tan, Thirumaleshwara N. Bhat, Sukant K. Tripathy, Yilmaz Dikme, Surani Bin Dolmanan, and Lakshmi Kanta Bera
- Subjects
Epiwafer ,Materials science ,business.industry ,Process Chemistry and Technology ,Wide-bandgap semiconductor ,Heterojunction ,High-electron-mobility transistor ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Barrier layer ,Materials Chemistry ,Optoelectronics ,Wafer ,Electrical measurements ,Metalorganic vapour phase epitaxy ,Electrical and Electronic Engineering ,business ,Instrumentation - Abstract
The authors report on the study of homogeneity in structural and optical properties of AlxGa1−xN/GaN high electron mobility transistor (HEMT) structures grown on 200 mm diameter Si(111) substrates. The consequence of a variation of buffer layer thicknesses as well as the interface quality has been studied by in-situ growth monitoring. A reasonably good uniformity of crystalline quality in the heterostructures grown with a lower wafer bowing has been observed from the full width at half maxima of symmetric as well as asymmetric high resolution x-ray diffraction scans across the wafer. Furthermore, the thickness and Al content of the AlxGa1−xN barrier layer across the wafer is found to be uniform when the wafer bowing is lower. Optical and electrical measurements across the epiwafer address the strain homogeneity, luminescence, and two-dimensional electron gas properties. Based on these studies of growth optimization, HEMT epiwafers with a total nitride stack thickness of 4.4 μm with a wafer bowing
- Published
- 2014
39. Thin-film InGaN∕GaN Vertical Light Emitting Diodes Using GaN on Silicon-On-Insulator Substrates
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Sukant K. Tripathy, Siew Lang Teo, Alois Krost, Surani Bin Dolmanan, Hui Kim Hui, Armin Dadgar, and Vivian Kaixin Lin
- Subjects
Materials science ,business.industry ,General Chemical Engineering ,Silicon on insulator ,law.invention ,law ,Electrochemistry ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Thin film ,business ,Light-emitting diode - Published
- 2011
40. Minority Carrier Lifetime Measurement Based on Low Frequency Fluctuation
- Author
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Ke, Lin, primary, Huang, Sha, additional, Chua, Soo Jin, additional, Lai, Szu Cheng, additional, and Surani, Bin Dolmanan, additional
- Published
- 2009
- Full Text
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41. Temperature rise in InGaN/GaN vertical light emitting diode on copper transferred from silicon probed by Raman scattering
- Author
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Siew Lang Teo, Sukant K. Tripathy, Surani Bin-Dolmanan, Esther Alarcon-Llado, Alois Krost, Armin Dadgar, and Vivian Kaixin Lin
- Subjects
Materials science ,Silicon ,business.industry ,General Physics and Astronomy ,chemistry.chemical_element ,Electroluminescence ,law.invention ,symbols.namesake ,chemistry ,law ,symbols ,Optoelectronics ,Light emission ,Dry etching ,Thin film ,business ,Raman spectroscopy ,Raman scattering ,Light-emitting diode - Abstract
The authors report on a Raman scattering study of self-heating in InGaN/GaN-based thin film vertical light emitting diode (VLED) on copper successfully transferred from silicon (111). The LED structures grown on bulk Si are transferred to a copper substrate host using electroplating and sacrificial removal of silicon by grinding, lapping and dry etching. The light emission characteristics of such VLEDs are studied by electroluminescence measurements. Due to self-heating at very high injection current, the temperature of the p-side down VLED without encapsulation and packaging increases rapidly and correlates well with the I-V characteristics. The Raman measurements allow probing of temperature profiles when these VLEDs are driven at current up to 1 A.
- Published
- 2010
42. Low frequency noise analysis on organic thin film transistors
- Author
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Surani Bin Dolmanan, Soo Jin Chua, Lay-Lay Chua, Perq-Jon Chia, Lin Ke, Peter K. H. Ho, Rui-Qi Png, Chellappan Vijila, and Lu Shen
- Subjects
Organic field-effect transistor ,Materials science ,business.industry ,Infrasound ,Transistor ,General Physics and Astronomy ,Noise (electronics) ,Threshold voltage ,law.invention ,Thin-film transistor ,law ,Optoelectronics ,Field-effect transistor ,Flicker noise ,business - Abstract
Bottom-contact organic field-effect transistors (OFETs) based on poly(3-hexylthiophene) with different channel lengths were fabricated under different substrate pretreatment process conditions. These OFET devices were characterized using low frequency noise (LFN) spectroscopy, and the device performance parameters were correlated with the level of LFN. It is observed that the devices with higher noise levels showed poorer device properties when compared with the devices operated at same Ids of the same channel length. It is also observed that the noise level increased with the increase in channel length for devices with the same pretreatment conditions, which is due to increased trapping and detrapping in the channel material interface domain. The OFET device operating around the threshold voltage Vth will have a 1/f noise slope that is flatter, having a gradient that is smaller in magnitude. The threshold voltage of a device can thus be observed to be at the gate voltage in which 1/f noise intensity is t...
- Published
- 2008
43. Impact of self-assembled monolayer on low frequency noise of organic thin film transistors
- Author
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Perq-Jon Chia, Soo Jin Chua, Surani Bin Dolmanan, Peter K. H. Ho, Lay-Lay Chua, Lu Shen, Chellappan Vijila, Lin Ke, and Rui-Qi Png
- Subjects
Conductive polymer ,Electron mobility ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Transistor ,Analytical chemistry ,Octadecyltrichlorosilane ,Noise (electronics) ,law.invention ,Organic semiconductor ,chemistry.chemical_compound ,chemistry ,Thin-film transistor ,law ,Optoelectronics ,Field-effect transistor ,business - Abstract
Bottom-contact organic field-effect transistors (FETs) based on regioregular poly(3-hexylthiophene) were fabricated with different surface treatments and were evaluated using a low frequency noise (LFN) spectroscopy. The oxygen-plasma (OP) treated device shows the highest mobility with the lowest current fluctuation. Octadecyltrichlorosilane and perfluorodecyldimetylchlorosilane treated device gives a higher noise compared with the OP treated device. Hexamethyldisilazane treated devices show the highest noise but the lowest mobility. The LFN results are correlated with organic FET device mobility and stability, proved by channel material crystallinity and degree of dislocations analysis. LFN measurement provides a nondisruptive and direct methodology to characterize device performance.
- Published
- 2008
44. Record-low contact resistance for InAlN/AlN/GaN high electron mobility transistors on Si with non-gold metal.
- Author
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Subramaniam Arulkumaran, Geok Ing Ng, Kumud Ranjan, Chandra Mohan Manoj Kumar, Siew Chuen Foo, Kian Siong Ang, Sahmuganathan Vicknesh, Surani Bin Dolmanan, Thirumaleshwara Bhat, and Sudhiranjan Tripathy
- Abstract
We have demonstrated 0.17-µm gate-length In
0.17 Al0.83 N/GaN high-electron-mobility transistors (HEMTs) on Si(111) substrates using a non-gold metal stack (Ta/Si/Ti/Al/Ni/Ta) with a record-low ohmic contact resistance (Rc ) of 0.36 Ω mm. This contact resistance is comparable to the conventional gold-based (Ti/Al/Ni/Au) ohmic contact resistance (Rc = 0.33 Ω mm). A non-gold ohmic contact exhibited a smooth surface morphology with a root mean square surface roughness of ∼2.1 nm (scan area of 5 × 5 µm2 ). The HEMTs exhibited a maximum drain current density of 1110 mA/mm, a maximum extrinsic transconductance of 353 mS/mm, a unity current gain cutoff frequency of 48 GHz, and a maximum oscillation frequency of 66 GHz. These devices exhibited a very small (<8%) drain current collapse for the quiescent biases (Vgs0 = −5 V, Vds0 = 10 V) with a pulse width/period of 200 ns/1 ms. These results demonstrate the feasibility of using a non-gold metal stack as a low Rc ohmic contact for the realization of high-frequency operating InAlN/AlN/GaN HEMTs on Si substrates without using recess etching and regrowth processes. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
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