Browsing by Author "Haider, Ali"

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Open Access
Area-selective atomic layer deposition of noble metals: polymerized fluorocarbon layers as effective growth inhibitors
(AVS Science and Technology Society, 2021-01-29) Deminskyi, Petro; Haider, Ali; Eren, Hamit; Khan, Talha Masood; Bıyıklı, Necmi
The increasingly complex nanoscale three-dimensional and multilayered structures utilized in nanoelectronic, catalytic, and energy conversion/storage devices necessitate novel substrate-selective material deposition approaches featuring bottom-up and self-aligned precision processing. Here, we demonstrate the area-selective atomic layer deposition (AS-ALD) of two noble metals, Pt and Pd, by using a plasma-polymerized fluorocarbon layer as growth inhibition surfaces. The contact angle, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy measurements were performed to investigate the blocking ability of polymerized fluorocarbon (CFx) layers against ALD-grown metal films. Both Pt and Pd showed significant nucleation delays on fluorocarbon surfaces. Self-aligned film deposition is confirmed using this strategy by growing Pt and Pd on the microscale lithographically patterned CFx/Si samples. CFx blocking layer degradation during ozone exposure was analyzed using XPS measurements, which confirmed the oxygen physisorption as the main responsible surface reaction with further hydroxyl group formation on the CFx surface. Our work reveals that the CFx layer is compatible with an ozone coreactant until the blocking polymer cannot withstand oxygen physisorption. Our results could potentially be used to investigate and develop radical-assisted AS-ALD processes for a wider selection of materials.
Open Access
Atomic layer deposition of III-nitrides and metal oxides : their application in area selective ALD
(2017-07) Haider, Ali
III-nitride compound semiconductor materials (GaN, AlN, and InN) and their alloys have generated significant interest in both basic research and commercial applications mainly in the field of photonics, energy storage, nano-sensors, and nano-(opto)electronics. Wurtzite type III-nitrides exhibit direct band gaps, which extend from the ultra-violet (UV) to the mid-IR spectrum with values of 6.2, 3.4 and 0.64 eV for AlN, GaN, and InN, respectively. This feature allows the band gap of III-nitride alloys to be conveniently tuned by precisely controlling the composition for a particular application. Metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are the most common successful techniques for achieving high-quality epitaxial III-nitride layers with low impurity concentrations and decent electrical properties. However, both of these methods employ high growth temperatures, which is neither compatible with the existing CMOS technology nor suitable for temperature-sensitive device layers (e.g. In-rich InxGa1-xN) and substrates (e.g. glass, flexible polymers, etc.). These limitations are the main driving source for a continuous exploration of alternative low temperature processes for the growth of III-nitride layers and their alloys. High aspect ratio III-nitride nanostructures in the form of nanowires and nanorods have been synthesized using different techniques including vapor-liquid-solid crystal growth, electrospinning, template based synthesis, and etching. Critical breakthroughs in fabrication of III-nitrides nanostructures have been achieved by above mentioned techniques but suffer from limited control over properties of nanostructures (shape, orientation, and size) and in some cases high growth-temperature requirement. A recent flurry of interest in developing high quality I-D III-nitride nanostructures derives from the desire to obtain flexible optoelectronic devices having wider applications. Template-assisted growth technique is one of the most promising approach to fabricate III-nitride nanostructures with precise control over shape, size, position, and distribution. In the first part of thesis, we have deposited InN and III-nitride alloys using hollow-cathode plasma assisted atomic layer deposition (HCPA-ALD) at low growth temperatures. The aim was to deposit III-nitride materials at lowest growth temperatures with decent crystalline quality and minimum impurity content. Depositions were carried out using group III organometallic precursors along with N2/H2 or N2 plasma as metal and nitrogen source, respectively. Process parameters including precursor pulse time, plasma flow duration, purge time, and deposition temperature are investigated and correlations were developed between process parameters and material properties. Refractive index of the InN film deposited at 200 C was found to be 2.66 at 650 nm. 48 nm-thick InN films exhibited relatively smooth surfaces with RMS surface roughness values of 0.98 nm, while the film density was extracted as 6.30 g/cm3. The effect of In content on structural, optical, and morphological properties of InxGa1-xN thin films was investigated. Grazing incidence X-ray diffraction (GIXRD) and transmission electron microscope (TEM) showed that InN and InxGa1-xN thin films were polycrystalline with hexagonal wurtzite structure. Spectral absorption measurements exhibited an optical band edge of InN around 1.9 eV. X-ray photoelectron spectroscopy (XPS) confirmed the deposition of InN and alloy thin films and revealed the presence of low impurity contents. Higher In concentrations resulted in an increase of refractive indices of InxGa1-xN ternary alloys from 2.28 to 2.42 at a wavelength of 650 nm. Optical band edge of InxGa1-xN films red-shifted with increasing In content, confirming the tunability of the band edge with alloy composition. Photoluminescence measurements of InxGa1-xN exhibited broad spectral features with an In concentration dependent wavelength shift. We have also studied the compositional dependence of structural, optical, and morphological properties of BxGa1-xN and BxIn1-xN ternary thin film alloys grown using sequential pulsed CVD. GIXRD measurements showed that boron incorporation in wurtzite lattice of GaN and InN diminishes the crystallinity of BxGa1-xN and BxIn1-xN sample. Refractive index decreased from 2.24 to 1.65 as the B concentration of BxGa1-xN increased from 35 to 88 %. Similarly, refractive index of BxIn1-xN changed from 1.98 to 1.74 for increase in B concentration value from 32 to 87 %, respectively. Optical transmission band edge values of the BxGa1-xN and BxIn1-xN films shifted to lower wavelengths with increasing boron content, indicating the tunability of energy band gap with alloy composition. Atomic force microscopy measurements revealed an increase in surface roughness with boron concentration of BxGa1-xN, while an opposite trend was observed for BxIn1-xN thin films. Moreover, we demonstrate vertical GaN, AlN, and InN hollow nano-cylindrical arrays (HNCs) integrated to Si(100) substrates using anodized aluminum oxide (AAO) membrane templated PA-ALD. Our fabrication and Si-integration strategy consists of the following process steps: (i) reactive ion etching (RIE) of Si using AAO membrane as hard mask material to achieve nanoporous Si substrate, (ii) conformal growth of III-nitride films on nanoporous Si via low-temperature PA-ALD, (iii) removal of PA-ALD coated III-nitride material from top surface of Si via plasma etching, and (iv) isotropic dry etching of surrounding Si to attain long-range ordered vertical III-nitride HNCs. The material properties of nanostructured III-nitride materials have been compared with the thin-film counterparts which were also grown using low-temperature PA-ALD. SEM images revealed that long-range ordered arrays of III nitride HNCs were successfully integrated in Si(100) substrates. TEM, GIXRD, and selected area electron diffraction (SAED) cumulatively confirmed that III-nitride HNCs possess hexagonal wurtzite crystalline structure. XPS survey and high-resolution scans detected presence of different elements and peaks at specific binding energies which confirmed the formation of III-nitride HNCs. The second part of the thesis deals with self-aligned thin film patterning of metal oxides using area selective atomic layer deposition (AS-ALD). Nanoscale process integration demands novel nano-patterning techniques in compliance with the requirements of next generation devices. Conventionally, top-down subtractive (etch) or additive (deposition/lift-off) processes in conjunction with various lithography techniques is employed to achieve film patterning, which become increasingly challenging due to the ever-shrinking misalignment requirements. To reduce the complexity burden of lithographic alignment in critical fabrication steps, self-aligned processes such as selective deposition and selective etching might provide attractive solutions. We demonstrate a methodology to achieve AS-ALD by using inductively couple plasma (ICP) grown fluorocarbon polymer film as growth inhibition layer. The fluorocarbon layer was grown using C4F8 feed gas in a conventional ICP-etch reactor. Our approach has been tested for metal-oxides including ZnO, Al2O3, TiO2, and HfO2. Additionally, we investigate the poly(methyl methacrylate) (PMMA) and polyvinylpyrrolidone (PVP) as growth inhibition layers for AS-ALD of TiO2. Contact angle, XPS, spectroscopic ellipsometer, energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) measurements were performed to investigate the blocking ability of polymer layers against ALD-grown films. Characterizations carried out revealed that effective blocking on fluorocarbon layer is achieved for ZnO film upto 136 growth cycles. On the other hand, a rather slow nucleation has been observed for HfO2 growth on fluorocarbon coated surfaces, while TiO2 and Al2O3 growth showed almost no delay with a growth rate equal to the ones on conventional substrate surfaces. For TiO2, PMMA revealed successful growth inhibition upto the maximum inspected growth cycles while PVP was able to block TiO2 growth upto 300 growth cycles. By exploiting this inhibition feature, thin film patterning has been demonstrated by growing ZnO films on photo lithographically patterned fluorocarbon/Si samples. We also demonstrate nanoscale patterned deposition of TiO2 using a PMMA masking layer that has been patterned using e-beam lithography.
Open Access
Atomic layer deposition of ruthenium nanoparticles on electrospun carbon nanofibers: a highly efficient nanocatalyst for the hydrolytic dehydrogenation of methylamine borane
(American Chemical Society, 2018) Khalily, Mohammad Aref; Yurderi, M.; Haider, Ali; Bulut, A.; Patil, Bhushan; Zahmakiran, M.; Uyar, Tamer
We report the fabrication of a novel and highly active nanocatalyst system comprising electrospun carbon nanofiber (CNF)-supported ruthenium nanoparticles (NPs) (Ru@CNF), which can reproducibly be prepared by the ozone-assisted atomic layer deposition (ALD) of Ru NPs on electrospun CNFs. Polyacrylonitrile (PAN) was electropsun into bead-free one-dimensional (1D) nanofibers by electrospinning. The electrospun PAN nanofibers were converted into well-defined 1D CNFs by a two-step carbonization process. We took advantage of an ozone-assisted ALD technique to uniformly decorate the CNF support by highly monodisperse Ru NPs of 3.4 ± 0.4 nm size. The Ru@CNF nanocatalyst system catalyzes the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage, with a record turnover frequency of 563 mol H2/mol Ru × min and an excellent conversion (>99%) under air at room temperature with the activation energy (Ea) of 30.1 kJ/mol. Moreover, Ru@CNF demonstrated remarkable reusability performance and conserved 72% of its inherent catalytic activity even at the fifth recycle.
Embargo
Continuous conducting architecture developed by supporting Prussian blue analogue on metal-organic framework derived carbon-doped manganese- oxide nanorods for high-performance sodium-ion batteries
(Elsevier BV, 2023-07-03) Ullah, Irfan; Saeed, Roheen; Inayat, Abid; Zubair, Muhammad; Wu, Xianyong; Duran, Hatice; Haider, Ali; Pope, Michael A.; Hussain, Irshad
Prussian blue analogues (PBA) are regarded as promising cathode materials for sodium-ion batteries (SIBs) owing to their open framework with large interstitial sites to accommodate Na+ ions. However, PBA suffer from low electronic conductivity and mechanical instability, which may be improved by their structural modification leading to enhanced kinetics. In this regard, we report an in-situ integration of ultra-small PBA cubes into three-dimensional metal organic framework (MOF) derived carbon-doped manganese oxide nanorods (C-Mn2O3), which form a continuous conductive architecture with intimate PBA/C-Mn2O3 contact. The C-Mn2O3 nanorods provide nucleation sites for the growth of PBA cubes and further act as the electronic pathway to improve electrode reaction kinetics. This hierarchical configuration effectively buffers the lattice expansion, which improve the structural stability of NiCoPBA. Consequently, the composite exhibits promising performance in aqueous Na+ batteries. Specifically, it delivers a high capacity of 97 mAh/g within a narrow potential window of and retained 82% capacity for 1000 cycles in aqueous electrolyte. It shows even higher capacity of 136 mAh/g and similar capacity retention (76% after 1000 cycles) in non-aqueous electrolytes. The promising performance of developed materials demonstrates the significant impact decreasing the size of PBA cubes has on the capacity by reducing the diffusion pathways and thus facilitating intercalation/deintercalation within the cubes. This study offers new insights of exploiting redox-active substrates to modify and stabilize PBA materials for energy storage applications.
Open Access
Effect of substrate temperature and Ga source precursor on growth and material properties of GaN grown by hollow cathode plasma assisted atomic layer deposition
(IEEE, 2016) Haider, Ali; Kizir, Seda; Deminskyi, P.; Tsymbalenko, Oleksandr; Leghari, Shahid Ali; Bıyıklı, Necmi; Alevli, M.; Gungor, N.
GaN thin films grown by hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD) at two different substrate temperatures (250 and 450 °C) are compared. Effect of two different Ga source materials named as trimethylgallium (TMG) and triethylgallium (TEG) on GaN growth and film quality is also investigated and reviewed. Films were characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometery, and grazing incidence X-ray diffraction. GaN film deposited by TMG revealed better structural, chemical, and optical properties in comparison with GaN film grown with TEG precursor. When compared on basis of different substrate temperature, GaN films grown at higher substrate temperature revealed better structural and optical properties.
Open Access
Growth and characterization of boron nitride thin films and nanostructures using atomic layer deposition = Bor nitrür ince filmlerin ve nanoyapıların atomik katman biriktirme yöntemi ile büyütülmesi ve karakterizasyonu
(2014) Haider, Ali
Being a member of III-nitride family, boron nitride (BN) and its nanostructures have recently attracted a lot of attention, mainly due to their distinctive and superior material properties, including wide band gap, high-temperature stability, high oxidation and corrosion resistance, as well as high thermal conductivity. This versatile material has found applications in UV emission, lubrication, composite reinforcement, gas adsorption, cosmetics, and thermal management. For modern electronic applications, it is imperative to obtain high quality BN films on large area substrates with a controlled thickness in order to fulfill the entire spectrum of hBN applications. Also, a facile method such as atomic layer deposition (ALD) using non halide precursors is necessary to obtain BN films at low temperatures compliant with the standards in terms of having nontoxic byproducts. ALD is a special case of chemical vapor deposition (CVD), in which two or more precursors are sequentially exposed to substrate surface separated by purging periods. In comparison with other thin film growth methods, hall mark of ALD is self limiting growth mechanism which enables deposition of highly uniform and conformal thin films with sub-angstrom thickness control. The precise and conformal layer by layer growth of ALD can be exploited to achieve growth of BN hollow nanofibers (HNFs) on high aspect ratio electrospun polymer nanofibrous templates. BN HNFs fabricated by combination of ALD and electrospinning can be utilized to address and solve important constraints associated with previous methods of fabrication such as severe preparation conditions, limited control over morphology, and low purity of the resulting BN HNFs. In this thesis, we report on the controlled deposition of BN films and its nanostructures with the use of a hollow-cathode plasma source integrated (HCPA-ALD) reactor and present detailed materials characterization results of deposited thin films and fabricated nanostructures. Depositions are carried out at low substrate temperatures (less than 450 °C) using sequential injection of nonhalide triethylboron (TEB) and N2/H2 plasma as boron and nitrogen precursors, respectively. The deposition process parameters such as pulse length of TEB and substrate temperature, as well as the influence of post-deposition annealing are studied. Moreover, another nonhalide alternative precursor named tris(dimethyl)amidoboron (TDMAB) was studied for deposition of BN films. Initial experiments were performed using TDMAB and N2/H2 plasma as boron and nitrogen precursor. In addition to BN thin film growth studies, we report on electrospun polymeric nanofibrous template-based fabrication and characterization of AlN/BN bishell HNFs. Synthesized AlN/BN bishell HNFs were found to be polycrystalline with a hexagonal structure along with lowimpurity content.
Open Access
Hollow-cathode plasma-assisted atomic layer deposition: A novel route for low-temperature synthesis of crystalline III-nitride thin films and nanostructures
(IEEE, 2015) Bıyıklı, Necmi; Ozgit-Akgun, Çağla; Goldenberg, Eda; Haider, Ali; Kızır, Seda; Uyar, Tamer; Bolat, Sami; Tekcan, Burak; Okyay, Ali Kemal
Hollow cathode plasma-assisted atomic layer deposition is a promising technique for obtaining III-nitride thin films with low impurity concentrations at low temperatures. Here we report our efforts on the development of HCPA-ALD processes for III-nitrides together with the properties of resulting thin films and nanostructures. The content will further include nylon 6,6/GaN core/shell and BN/AlN bishell hollow nanofibers, proof-of-concept thin film transistors and UV photodetectors fabricated using HCPA-ALD-grown GaN layers, as well as early results for InN thin films deposited by HCPA-ALD technique. © 2015 IEEE.
Open Access
Investigation of native oxide removing from HCPA ALD grown GaN thin films surface utilizing HF solutions
(IEEE, 2016) Deminskyi, Petro; Haider, Ali; Bıyıklı, Necmi; Ovsianitsky, A.; Tsymbalenko, A.; Kotov, D.; Matkivskyi, V.; Liakhova, N.; Osinsky, V.
The paper consider oxygen contamination of HCPA ALD grown GaN films under an air conditioning and during different time duration. High resolution XPS analysis of HCPA ALD grown GaN films after diluted 1:10 HF(41 %) : H2O and undiluted HF (41 %) influence on oxygen impurities was investigated. Lesser oxygen impurities have been observed. Better resistivity to oxygen atoms of GaN thin films after diluted HF solution treatment was achieved compared to undiluted HF treatment and without treatment.
Open Access
Zno nanostructures via hydrothermal synthesis on atomic layer deposited seed-layers
(IEEE, 2015) Orlov, A.; Ulianova, V.; Bogdan, O.; Pashkevich, G.; Bıyıklı, Necmi; Goldenberg, Eda; Haider, Ali
The original results of two different types of ZnO nanostructures grown via hydrothermal synthesis on ZnO seed-layers coated by atomic layer deposition process on Si substrates were presented. Scanning electron microscopy and X-ray diffractometry were used for the analysis of resulting nanostructured ZnO samples. The influence of annealing on crystal properties of the ZnO nanostructures was shown. It was ascertained that solution composition had a significant influence on the morphology of nanostructures and post-growth annealing modified the crystal properties of nanostructures. © 2015 IEEE.