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Combining different material processing techniques is one of the keys to obtain materials that depict synergistic properties. In this review, we have reviewed a combination of two highly potential techniques, namely, electrospinning and atomic layer deposition (ALD), in the view of various applications. Over the past 10 years, our research groups are involved in the exploration of employing this combination for a range of applications. We also include some basic information on both the processes and diversity of nanostructures as a result of their combination. Nonwoven nanofiber membranes are excellent candidates for a wide range of applications. Also, they can act as templates to produce various other kinds of nanostructures when combined with ALD in small/large scale production. These nanostructures could be used as such or further subjected to other processing techniques yielding hierarchical structures. In this review, we exclusively survey and highlight the unique capabilities of combined electrospinning and ALD for applications in catalysis, photocatalysis, solar cells, batteries and gas sensors.

In this paper, we present the progress in the growth of nanoscale semiconductors grown via atomic layer deposition (ALD). After the adoption by semiconductor chip industry, ALD became a widespread tool to grow functional films and conformal ultra-thin coatings for various applications. Based on self-limiting and ligand-exchange-based surface reactions, ALD enabled the low-temperature growth of nanoscale dielectric, metal, and semiconductor materials. Being able to deposit wafer-scale uniform semiconductor films at relatively low-temperatures, with sub-monolayer thickness control and ultimate conformality, makes ALD attractive for semiconductor device applications. Towards this end, precursors and low-temperature growth recipes are developed to deposit crystalline thin films for compound and elemental semiconductors. Conventional thermal ALD as well as plasma-assisted and radical-enhanced techniques have been exploited to achieve device-compatible film quality. Metal-oxides, III-nitrides, sulfides, and selenides are among the most popular semiconductor material families studied via ALD technology. Besides thin films, ALD can grow nanostructured semiconductors as well using either template-assisted growth methods or bottom-up controlled nucleation mechanisms. Among the demonstrated semiconductor nanostructures are nanoparticles, nano/quantum-dots, nanowires, nanotubes, nanofibers, nanopillars, hollow and core-shell versions of the afore-mentioned nanostructures, and 2D materials including transition metal dichalcogenides and graphene. ALD-grown nanoscale semiconductor materials find applications in a vast amount of applications including functional coatings, catalysis and photocatalysis, renewable energy conversion and storage, chemical sensing, opto-electronics, and flexible electronics. In this review, we give an overview of the current state-of-the-art in ALD-based nanoscale semiconductor research including the already demonstrated and future applications.

Here peptide amphiphile (PA) nanofiber network is exploited as a three-dimensional soft template to construct anatase TiO2 and wurtzite ZnO nanonetworks. Atomic layer deposition (ALD) technique is used to coat the organic nanonetwork template with TiO2 and ZnO. ALD method enables uniform and conformal coatings with precisely controlled TiO2 and ZnO thickness. The resulting semiconducting metal oxide nanonetworks are utilized as anodic materials in dye-sensitized solar cells. Effect of metal oxide layer thickness on device performance is studied. The devices based on thin TiO2 coatings (< 10 nm) demonstrate considerable dependence on material thickness, whereas thicker (> 17 nm) ZnO-based devices do not show an explicit correlation. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

AlN and GaN thin films were deposited by plasma-enhanced atomic layer deposition using trimethylmetal precursors. The films were found to have high oxygen incorporation, which was attributed to oxygen contamination related to the plasma system. The choice of nitrogen containing plasma gas (N2, N2/H2 or NH3) determined the severity of oxygen incorporation into deposited films. Lowest oxygen concentrations were attained for AlN and GaN thin films using NH3 and N2 plasma, respectively. Initial experiments have shown that GaN thin films with low impurity concentrations can be deposited when plasma-related oxygen contamination is avoided by the use of an alternative plasma source. © The Electrochemical Society.

Crystalline aluminum nitride (AlN) films have been prepared by plasma-enhanced atomic layer deposition (PEALD) within the temperature range from 100 to 500 degrees C. A self-limiting, constant growth rate per cycle temperature window ( 100200 degrees C) was established which is the major characteristic of an ALD process. At higher temperatures (>225 degrees C), deposition rate increased with temperature. Chemical composition, crystallinity, surface morphology, mass density, and spectral refractive index were studied for AlN films. X-ray photoelectron spectroscopy (XPS) analyses indicated that besides main Al-N bond, the films contained Al-O-N, Al-O complexes, and Al-Al metallic aluminum bonds as well. Crystalline hexagonal AlN films were obtained at remarkably low growth temperatures. The mass density increased from 2.65 to 2.96 g/cm(3) and refractive index of the films increased from 1.88 to 2.08 at 533 nm for film growth temperatures of 100 and 500 degrees C, respectively. (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Date of Conference: 18-21 June 2012 Conference name: Microtech Conference & Expo 2012 We demonstrate that room-temperature liquid metal alloy droplets of Eutectic Gallium Indium (EGaIn) and Gallium Indium Tin alloy (Galinstan) can be actuated using electro-wetting-on-dielectric (EWOD) effect. With the application of 80-100V across the actuation electrode and ground electrode, the metallic liquid droplets were observed to be actuated. We have studied the actuation characteristics using different electrode architectures in open-air configuration as well as in encapsulated microfluidic channel test-beds. The resulting microfluidic DC actuation might potentially be used for RF switching applications.

Design, fabrication, and characterization of high-performance AI xGa1-xN-based photodetectors for solar-blind applications are reported. AlxGa1-xN heterostructures were designed for Schottky. p-i-n, and metal-semicondnctor-metal (MSM) photodiodes. The solar-blind photodiode samples were fabricated using a microwave compatible fabrication process. The resulting devices exhibited extremely low dark currents. Below 3 fA, leakage currents at 6-V reverse bias were measured on p-i-n samples. The excellent current-voltage (I-V) characteristics led to a detectivity performance of 4.9×1014 cmHz1/2W -1. The MSM devices exhibited photoconductive gain, while Schottky and p-i-n samples displayed 0.09 and 0.11 A/W peak responsivity values at 267 and 261 nm, respectively. A visible rejection of 2×104 was achieved with Schottky samples. High-speed measurements at 267 nm resulted in fast pulse responses with greater than gigahertz bandwidths. The fastest devices were MSM photodiodes with a maximum 3-dB bandwidth of 5.4 GHz.

We report solar-blind AlxGal1-xN-based heterojunction p-i-n photodiodes with low dark current and high detectivity. After the p+ GaN cap layer was recess etched, measured dark current was below 3 fA for reverse bias values up to 6 V. The device responsivity increased with reverse bias and reached 0.11 A/W at 261 nm under 10-V reverse bias. The detectors exhibited a cutoff around 283 nm, and a visible rejection of four orders of magnitude at zero bias. Low dark current values led to a high differential resistance of 9.52 × 1015 Ω. The thermally limited detectivity of the devices was calculated as 4.9 × 1014 cm · Hz1/2W-1. © 2004 IEEE.

Cataloged from PDF version of article. High-performance detection of ultraviolet (UV) radiation is of great importance for a wide range of applications including flame sensing, environmental (ozone layer) monitoring, detection of biological/chemical agents, missile early warning systems, and secure intersatellite communication systems. These applications require high-performance UV photodetectors with low dark current, high responsivity, high detectivity, and fast time response. The widebandgap AlxGa1−xN ternary alloy is well-suited as a photodetector material for operation in the wavelength range of 200 nm to 365 nm. Its outstanding material properties (direct bandgap, tunable cut-off, allows heterostructures, intrinsically solar-blind) make AlxGa1−xN suitable for a variety of harsh environments. If properly constructed, AlxGa1−xN-based photodetectors could offer significant advantages over the older photomultiplier tube (PMT) technology in terms of size, cost, robustness, complexity, dark current, bandwidth, and solar-blind operation. The motivation behind this work is the need for high-performance, solid-state UV photodetectors that can be cost-effectively manufactured into high-density arrays. We have designed, fabricated, and characterized several visible/solar-blind AlxGa1−xN photodiode samples. With solar-blind AlxGa1−xN photodiode samples, we achieved excellent device performance in almost all aspects. Very low dark currents were measured with heterostructure AlxGa1−xN Schottky and p-i-n samples. The extremely low leakage characteristics resulted in record detectivity and noise performance. Detectivity performance comparable to PMT detectivity was achieved. True solar-blind operation (sub-280 nm cut-off) with high visible rejection was demonstrated. In addition, we improved the bandwidth performance of AlxGa1−xN-based solar-blind photodetectors by over an order of magnitude. Solar-blind Schottky, p-i-n, and metal-semiconductor-metal photodiode samples exhibited very fast pulse response with multi-GHz bandwidths. Bıyıklı, Necmi Ph.D.

Ankara : Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 1998. Thesis (Master's) -- Bilkent University, 1998. Includes bibliographical references leaves 62-68. Bıyıklı, Necmi M.S.

In this work, we demonstrate vertical GaN, AlN, and InN hollow nano-cylindrical arrays (HNCs) grown on Si substrates using anodized aluminum oxide (AAO) membrane templated low-temperature plasma-assisted atomic layer deposition (PA-ALD). III-Nitride HNCs have been characterized for their structural, chemical, surface, and optical properties. The material properties of nanostructured III-nitride materials have been compared with the thin-film counterparts which were also grown using PA-ALD. Our results revealed that long-range ordered arrays of III nitride HNCs were successfully integrated on Si substrates and possess hexagonal polycrystalline wurtzite crystalline structure. Such long-range ordered wafer-scale III-nitride nanostructures might be potentially used in piezotronic sensing, energy harvesting, resistive memory, flexible and wearable electronics, III-nitride photovoltaics, and (photo)catalysis.

Coupling the functional nanoheterostructures over the flexible polymeric nanofibrous membranes through electrospinning followed by the atomic layer deposition (ALD), here we presented a high surface area platform as flexible and reusable heterogeneous nanocatalysts. Here, we show the ALD of titanium dioxide (TiO2) protective nanolayer onto the electrospun polyacrylonitrile (PAN) nanofibrous web and then platinum nanoparticles (Pt-NP) decoration was performed by ALD onto TiO2 coated PAN nanofibers. The free-standing and flexible Pt-NP/TiO2-PAN nanofibrous web showed the enhancive reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 45 seconds though the hydrogenation process with the degradation rate of 0.1102 s−1. The TiO2 protective layer on the PAN polymeric nanofibers was presented as an effective route to enhance the attachment of Pt-NP and to improve the structure stability of polymeric nanofibrous substrate. Commendable enhancement in the catalytic activity with the catalytic dosage and the durability after the reusing cycles were investigated over the reduction of 4-NP. Even after multiple usage, the Pt-NP/TiO2-PAN nanofibrous webs were stable with the flexible nature with the presence of Pt and TiO2 on its surface.

Here, we report nano-patterning of TiO2via area selective atomic layer deposition (AS-ALD) using an e-beam patterned growth inhibition polymer. Poly(methylmethacrylate) (PMMA), polyvinylpyrrolidone (PVP), and octafluorocyclobutane (C4F8) were the polymeric materials studied where PMMA and PVP were deposited using spin coating and C4F8 was grown using inductively coupled plasma (ICP) polymerization. TiO2 was grown at 150 °C using tetrakis(dimethylamido) titanium (TDMAT) and H2O as titanium and oxygen precursors, respectively. Contact angle, scanning electron microscopy (SEM), spectroscopic ellipsometry, and X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate the blocking/inhibition effectiveness of polymer layers for AS-ALD of TiO2. TiO2 was grown with different numbers of growth cycles (maximum = 1200 cycles) on PMMA, PVP, and C4F8 coated substrates, where PMMA revealed complete growth inhibition up to the maximum number of growth cycles. On the other hand, PVP was able to block TiO2 growth up to 300 growth cycles only, whereas C4F8 showed no TiO2-growth blocking capability. Finally, mm-, μm-, and nm-scale patterned selective deposition of TiO2 was demonstrated exploiting a PMMA masking layer that has been patterned using e-beam lithography. SEM, energy-dispersive X-ray spectroscopy (EDX) line scan, EDX elemental mapping, and XPS line scan measurements cumulatively confirmed the self-aligned deposition of TiO2 features. The results presented for the first time demonstrate the feasibility of achieving self-aligned TiO2 deposition via TDMAT/H2O precursor combination and e-beam patterned PMMA blocking layers with a complete inhibition for >50 nm-thick films.

Plasma-assisted atomic layer deposition (PA-ALD) is a promising method for low-temperature growth of III-nitride materials. However, selective film deposition using PA-ALD is challenging mainly due to the plasma-incompatibility of conventional deactivation/blocking layers including self-assembled monolayers and polymers. The main motivation behind this work is to explore alternative plasma-resistant blocking layer materials. Toward this goal, single/multilayered graphene (SLG/MLG) sheets were investigated as potential growth-blocking layers for III-nitride grown via PA-ALD. Prior to PA-ALD growth experiments, partially graphene-covered Si(100) samples were exposed to N2/H2 and N2-only plasma cycles to evaluate the plasma resistance of SLG and MLG. While SLG degraded fairly quickly showing signs of completely etched areas and rough surface morphology, MLG surface displayed certain degree of plasma-resistance. Based on this result, III-nitride PA-ALD experiments were carried out on MLG-patterned Si(100) samples. Crystalline III-nitride film deposition was observed on both Si(100) and graphene surfaces, confirming the rather ineffective nucleation blocking property of graphene surface against PA-ALD process. However, as graphene layers feature relatively weak van der Waals bonds at the substrate/graphene interface as well as between the multilayer graphene interfaces, conventional lift-off process was sufficient to remove the deposited excessive nitride films. InN and AlN-coated samples were ultrasonicated, and blocked/unblocked surfaces were characterized using scanning electron microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometer. While ∼50 nm thick films were measured in the open Si(100) areas, graphene-coated sample portions exhibited limited material growth in the range of 5-15 nm. Although not completely, the MLG surface has considerably blocked the PA-ALD growth process resulting in a usable thickness difference, enabling growth selectivity with postgrowth etch process. An Ar-based physical dry etching recipe was utilized to completely etch the unwanted nitride films from graphene coated area, while about 30 and 40 nm thick InN and AlN films remained on the nonblocked parts of the samples, respectively. As a result, selective deposition of PA-ALD grown AlN and InN has been achieved via graphene-assisted lift-off technique along with subsequent dry-etch process, achieving a maximum growth selectivity of ∼40 nm. With further process recipe optimization and integrating with a suitable patterning technique, the demonstrated graphene-assisted lift-off technique might offer an alternative feasible pathway toward area-selective deposition of III-nitrides and other plasma-necessitating materials. The authors acknowledge the National Nanotechnology Research Center (UNAM), Bilkent University for providing the materials growth and characterization facilities. P.D. acknowledges TUBITAK for financial support under the BIDEB-2216 fellowship program for international researchers. A.H. acknowledges Higher Education Commission of Pakistan (HEC) for the Human Resource Development (HRD) fellowship for MS leading to Ph.D. N.B. acknowledges support from the European Commission-Research Executive Agency (REA)-Marie Curie International Reintegration Grant (NEMSmart, Grant No. PIRG05-GA-2009-249196). N.B. also acknowledges the financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) through Grant Nos. 112M004, 112M482, and 214M015.

In this paper, AlN thin films with two different thicknesses, i.e., 7 and 47 nm, were deposited at 200 °C on p-type Si substrates by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia. To investigate the electrical characteristics of these AlN films, MIS capacitor structures were fabricated and characterized using current-voltage and high-frequency (1 MHz) capacitance-voltage measurements. The results showed that the current transport mechanism under accumulation mode is strongly dependent on the applied electric field and thickness of the AlN film. Possible conduction mechanisms were analyzed, and the basic electrical parameters were extracted and compared for AlN thin films with different thicknesses. Compared with 7-nm-thick film, a 47-nm-thick AlN film showed a lower effective charge density and threshold voltage along with a higher dielectric constant.

Photocatalytic activity (PCA) on semiconductors is known to be majorly influenced by specific surface area and intrinsic lattice defects of the catalyst. In this report, we tested the efficiencies of 1D ZnO catalysts of varying fiber diameter (80 nm and 650 nm of inner diameter) in two formats, viz. core–shell and hollow nanofibers, where the former is calcined to yield the latter. These nanofibrous catalysts were produced by combining electrospinning and atomic layer deposition processes which were then subjected to thorough characterization including photoluminescence (PL) unveiling the details of intrinsic defects/densities. During the thermal treatment, intrinsic defects are reorganized and as a result a new PL band is observed apart from some significant changes in the intensities of other emissions. The densities of various intrinsic defects from PL are compared for all samples and juxtaposed with the PCA. Careful scrutiny of the various results suggested an anti-correlation between surface area and PCA; i.e., higher surface area does not necessarily imply better PCA. Beyond a limit, the most deterministic factor would be the density of surface defects rather than the specific surface area. The results of this study enable the researchers to fabricate 1D semiconductor photocatalysts while striking the balance between surface area and density of defects.

In this report, we study the evolution of valence band (VB) structure during a controlled amorphous to tetragonal transformation of ZrO2 core shell nanostructures fabricated from electrospun nanofiber template (at 130, 200, and 250 degrees C). Shell-ZrO2 was formed with atomic layer deposition. X-ray diffraction and transmission electron microscopy are employed to unveil the transformation of amorphous to crystalline structure of ZrO2. O is core-level spectra indicated chemisorbed oxygen (O-Ch) of almost invariant fraction for the three samples. Zr 3s level suggested that the sample deposited at 130 degrees C has depicted a peak at relatively higher binding energy. Analyses on Zr 3d spectra indicated the presence of metallic-Zr (Zr+zeta, 0

SrTiO3 (STO) thin films have been prepared by reactive RF magnetron sputtering on Si (100) and UV fused silica substrates at room temperature. The effect of oxygen flow on film characteristics was investigated at a total gas flow of 30 sccm, for various O-2/O-2 + Ar flow rate ratios. As-deposited films were annealed at 700 degrees C in oxygen atmosphere for 1 h. Post-deposition annealing improved both film crystallinity and spectral transmittance. Film microstructure, along with optical and electrical properties, was evaluated for both as-deposited and annealed films. Abroad photoluminescence emission was observed within the spectral range of 2.75-3.50 eV for all STO thin films irrespective of their deposition parameters. Upon annealing, the optical band gap of the film deposited with 0% O-2 concentration slightly blue-shifted, while the other samples grown at higher oxygen partial pressure did not show any shift. Refractive indices (n) (at 550 nm) were in the range of 2.05 to 2.09, and 2.10 to 2.12 for as-deposited and annealed films, respectively. Dielectric constant values (at 100 kHz) within the range of 30-66 were obtained for film thicknesses less than 300 nm, which decreased to similar to 30-38 after postdeposition annealing. (C) 2015 Published by Elsevier B.V.

Hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD) is a promising technique for obtaining III-nitride thin films with low impurity concentrations at low temperatures. Here we report our previous and current efforts on the development of HCPA-ALD processes for III-nitrides together with the properties of resulting thin films and nanostructures. The content further includes nylon 6,6-GaN core-shell nanofibers, proof-of-concept thin film transistors and UV photodetectors fabricated using HCPA-ALD-grown GaN layers, as well as InN thin films deposited by HCPA-ALD using cyclopentadienyl indium and trimethylindium precursors. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Here we demonstrate the combination of electrospinning and hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD) processes by fabricating flexible polymer-GaN organic-inorganic core-shell nanofibers at a processing temperature much lower than that needed for the preparation of conventional GaN ceramic nanofibers. Polymer-GaN organic-inorganic core-shell nanofibers fabricated by the HCPA-ALD of GaN on electrospun polymeric (nylon 6,6) nanofibers at 200 °C were characterized in detail using electron microscopy, energy dispersive X-ray analysis, selected area electron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence measurements, and dynamic mechanical analysis. Although transmission electron microscopy studies indicated that the process parameters should be further optimized for obtaining ultimate uniformity and conformality on these high surface area 3D substrates, the HCPA-ALD process resulted in a ∼28 nm thick polycrystalline wurtzite GaN layer on polymeric nanofibers of an average fiber diameter of ∼70 nm. Having a flexible polymeric core and low processing temperature, these core-shell semiconducting nanofibers might have the potential to substitute brittle ceramic GaN nanofibers, which have already been shown to be high performance materials for various electronic and optoelectronic applications.

Yarı iletken III-nitrit bileşikleri (GaN, AlN, and InN) ve onların alaşımları, hem temel araştırma alanlarında hem de ticari uygulamalarda, özellikle fotonik, enerji depolaması, nano-sensörler ve nano-(opto) elektronikler alanlarında önemli ilgi uyandırmıştır. Würtzit tipi III-nitritları, sırasıyla AlN, GaN ve InN için 6,2, 3,4 ve 0,64 eV değerleri ile morötesi (UV) ile orta-IR spektruma uzanan doğrudan bant aralıklarına sahiptir. Bu özellik, belirli uygulamalar için III-nitrit alaşımlarının band aralığını tam bileşim kontrolü ile kolaylıkla ayarlamaya izin veriyor. Metalorganik kimyasal buhar birikimi (MOCVD) ve Moleküler kiriş epitaksisi (MBE), düşük safsızlık konsantrasyonlu ve iyi elektriksel özelliğe sahip yüksek kaliteli epitaksiyel III-nitrit tabakalarını elde etmenin en yaygın ve başarılı yöntemleridir. Fakat bununla birlikte, bu yöntemlerin her ikisi de, mevcut CMOS teknolojisi ile uyumlu olmayan ya da sıcaklığa duyarlı aygıt katmanlarına (örneğin In-zengin InxGa1-xN) ve alt tabakalara (örneğin cam, esnek polimerler, vb.) uygun olmayan yüksek büyüme sıcaklıkları kullanmaktadı. Bu kısıtlamalar, III-nitrit ve alaşımlarının tabakalarını büyütmenin alternatif düşük sıcaklıktaki proseslerin araştırmalarının ana itici kaynağıdır. Nanotel ve nanoçubuk şeklindeki yüksek en-boy oranlı III-nitrit nanoyapıları buhar-sıvı-katı kristal büyütmesi, elektrospinning, şablon esaslı sentez ve aşındırma yöntemlerini kapsayan yöntemlerle sentezlenmiştir. III-nitrit nanoyapıların üretiminde kritik gelişmeler yukarıda adı geçen yöntemlerle elde edilmiştir ancak nanoyapılardaki (şekil, yönelim ve boyut) özelliklerde kısıtlı kontrol ve bazı yüksek sıcaklık gereksinimlerinden muzdarip. Yüksek kalitede I-D III-nitrit nanoyapıların geliştirilmesine yönelik yeni bir ilgi, daha geniş uygulamalara sahip esnek optoelektronik aygıtlar elde etme isteğinden kaynaklanmaktadır. Şablon destekli büyütme tekniği, III- nitrit nanoyapılarının şekli, boyutu, konumu ve dağılımı üzerinde hassas kontrolü olan en umut verici üretim yöntemlerinden bir tanesidir.Tezin ilk bölümünde, düşük büyüme sıcaklıklarında içi boş katot plazma yardımlı atomik katman çökeltme (HCPA-ALD) kullanarak InN ve III-nitrür alaşımları tevdi ettik. Amaç, III-nitrür materyallerin, uygun kristal kalitesi ve minimum safsızlık içeriği ile en düşük büyüme sıcaklıklarında depolanmasıydı. Depozisyonlar N2/H2 ve N2 plazması ile birlikte grup III organometalik öncülleri kullanılarak gerçekleştirildi. Prekürsör darbe süresi, plazma akış süresi, boşaltma süresi ve çökelme sıcaklığı gibi proses parametreleri araştırılmış ve proses parametreleri ile malzeme özellikleri arasında korelasyonlar geliştirilmiştir. 200 °C'de biriken InN filminin refraktif indeksi 650 nm'de 2.66 bulundu. 48 nm kalınlığında InN filmleri 0.98 nm RMS yüzey pürüzlülüğü değerlerine sahip nispeten pürüzsüz yüzeyler sergilerken film yoğunluğu 6.30 g / cm3 olarak çıkarıldı. In içeriğinin yapısal, optik ve InxGa1-xN ince filmlerin morfolojik özelliklerine etkisi araştırıldı. Grazing insidansı X-ışını kırınımı (GIXRD) ve transmisyon elektron mikroskobu (TEM). InN ve InxGa1-xN ince filmlerin altıgen würzit yapıya sahip polikristalin olduğunu gösterdi. Spektral absorpsiyon ölçümleri, 1.9 eV civarında InN'nin bir optik bant kenarını sergiledi. X-ışını fotoelektron spektroskopisi (XPS) InN ve alaşım ince filmlerin birikimini doğruladı ve düşük safsızlık içeriğinin varlığını ortaya koydu. Dahası, anodize edilmiş aliminyum oksit (AAO) membran kalıplı PA-ALD kullanarak Si(100) alttaş üzerine dikey GaN, AlN ve InN oyuk nano-silindir dizisinin etegrasyonu gösterildi. Bizim fabrikasonumuz ve Si-etegrasyonu takip eden işlemleri içerir: (i) Nano-pürüzlü Si alttaşa sahip olmak için, AAO membranı sert maske malzemesi olarak kullanarak Si rekatif iyon oyma (RIE), (ii) düşük sıcaklıklı PA-ALD ile nano-pürüzlü Si üzerinde III-Nitrat filmlerin konformal olarak büyütülmesi, (iii) PA-ALD kaplamalı III-nitrat malzemelerin Silikon yüzeyinden plazma oyma kullanarak kaldırılması, ve (iv) uzun mesafeli dizili dikey III-nitrat HNC'lere sahip olmak için Silikonun çevresinin izotropik kuru oyulması. Nano-işlenmiş III-Nitrat malzemelerin malzeme özellikleri, benzer şekilde düşük sıcaklıklı PA-ALD'de büyütülmüş ince film emsalleri ile karşılaştırıldı. SEM resimleri, uzun sıralı dizilmiş III-Nitrat HNC dizisi başarılı bir şekilde Si(100) alttaşa entegre edildiğini ortaya koymuştur. TEM, GIXRD ve seçili alan electron difraksiyon (SAED) sonuçları III-Nitrat HNC'lerin hegzagonal wurtzite kristal yapıya sahip olduğunu kümülatif olarak gösterdi. XPS analizi ve yüksek çözünürlüklü taramalar III-Nitrat HNC'lerin farmasyonunun doğrulayan spesifik bağlanma enerjilerinde farklı elementler tespit etti. Tezin ikinci bölümü,alan seçmeli atomik katman birikimini kullanarak metal oksitlerin ince filmde kendi dizilişine değinmektedir(AS-ALD).Nanoölçüm süreç entegrasyonu yeni nesil cihazların gereksinimlerine uygun olarak nanodiziliş tekniklerini talep eder.Genellikle, çeşitli litografi teknikleri ile birlikte yukarıdan aşağıya eksiltici(etch) ya da katkı maddesi(biriktirme/kaldırma) prosesleri filmin desenleme işlemini elde etmek için kullanılır,bu, sürekli küçülen yanlış hizalama gereksinimleri nedeniyle gittikçe zorlaşır.Kritik üretim aşamalarında litografik hizalamanın karmaşıklık yükünü azaltmak için, seçici biriktirme ve seçici aşındırma gibi kendi kendine hizalı işlemler cazip çözümler sağlayabilir.Artımlı inhibisyon tabakası olarak indükte çift plazma (ICP) yetiştirilmiş florokarbon polimer filmi kullanarak AS-ALD'yi gerçekleştirmek için bir metodoloji gösteriyoruz.Florokarbon tabakası, alışılmış bir ICP-etch reaktöründe C4F8 besleme gazı kullanılarak büyütüldü. Yaklaşımımız ZnO, Al2O3, TiO2 ve HfO2 gibi metal oksitler için test edilmiştir. Ayrıca, TiO2'nin AS-ALD için büyüme önleyici tabakalar olarak poli (metil metakrilat) (PMMA) ve polivinilpirolidonu (PVP) araştırdık.ALD ile üretilen filmlere karşı polimer katmanlarının bloke edici özelliklerini araştırmak için temas açısı, XPS, spektroskopik elipsometre, enerji dağılımlı X-ışını spektroskopisi (EDX) ve taramalı elektron mikroskobu (SEM) ölçümleri yapıldı. Yapılan karakterizasyonlar, ZnO filmi 136 büyüme çevrimine kadar florokarbon tabakasında etkili bir blokajın gerçekleştirildiğini ortaya koydu.Diğer yandan,TiO2 ve Al2O3 büyümesi, geleneksel substrat yüzeylerindeki büyüme hızına eşit bir büyüme oranı ile neredeyse hiç gecikme göstermezken,florokarbon kaplı yüzeylerde HfO2 büyümesinde oldukça yavaş bir çekirdeklenme gözlemlendi. TiO2 için, PMMA maksimum incelenen büyüme döngüsüne kadar başarılı büyüme inhibisyonu ortaya koyarken, PVP ,TiO2 büyümesini 300 büyüme döngüsüne kadar bloke edebildi. Bu inhibisyon özelliğinden yararlanılarak ince film şekillenmesi, foto litografik olarak desenli florokarbon/Si numuneleri üzerinde ZnO filmlerinin büyütülmesi ile gösterildi.e-ışınlı litografi kullanılarak desenlendirilmiş bir PMMA maskeleme katmanı kullanarak TiO2'nin nano ölçekli desenli birikimini ayrıca kanıtlamış olduk. 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. 199

Guler, Mustafa/0000-0003-1168-202X; Acar, Handan/0000-0001-8708-9279 WOS: 000397499300008 Point-of-care biosensor applications require low-cost and low-power solutions. They offer being easily accessible at home site. They are usable without any complex sample handling or any kind of special expertise. Impedance spectroscopy has been utilized for point-of-care biosensor applications; however, electrical double layer formed due to ions in the solution of interest has been a challenge, due to shielding of the electric field used for sensing the target molecules. Here in this study, we demonstrate a nanogap based biosensor structure with a relatively low frequency (1-100 kHz) measurement technique, which not only eliminates the undesired shielding effect of electrical double layer but also helps in minimizing the measurement volume and enabling low concentration (A mu molar level) detection of target molecules (streptavidin). Repeatability and sensitivity tests proved stable and reliable operation of the sensors. These biosensors might offer attributes such as low-cost label-free detection, fast measurement and monolithic chip integrability. European Union Framework Program 7 Marie Curie IRG [239444, 249196]; COST NanoTPEuropean Cooperation in Science and Technology (COST); TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [109E044, 112M004, 112E052, 112M944, 113M815]; TUBITAK-BIDEBTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) This work was supported in part by European Union Framework Program 7 Marie Curie IRG Grant 239444 and 249196, COST NanoTP, TUBITAK Grants 109E044, 112M004, 112E052, 112M944 and 113M815. The authors acknowledge support from TUBITAK-BIDEB. The authors thank Firat Yilmaz for his contributions and Dr. Mohammad Ghaffari for SEM images.

Plasmonic enhancement for electron–hole separation efficiency and visible light photocatalysis was achieved by Pd nanocube decoration on a ZnO nanolayer coated onto electrospun polymeric (polyacrylonitrile (PAN)) nanofibers. Since exciton formation and sustainable electron–hole separation have a vital importance for realizing better solar energy in photovoltaic and photocatalytic devices, we achieved visible light photocatalysis by Pd nanocube decoration onto well designed core–shell nanofibers of ZnO@PAN-NF. By controlling the cubic Pd nanoparticle size and the thickness of the crystalline ZnO nanolayer deposited onto electrospun PAN nanofibers via atomic layer deposition (ALD), defect mediated visible light photocatalysis efficiency can be increased. By utilizing nanofabrication techniques such as thermal decomposition, electrospinning and ALD, this fabricated template became an efficient, defect mediated, Pd nanocube plasmon enhanced photocatalytic system. Due to the enhanced contact features of the Pd nanocubes, an increase was observed for the visible light photocatalytic activity of the flexible and nanofibrous mat of Pd@ZnO@PAN-NF.

Çinko oksit (ZnO) 3.4 eV gibi geniş bir bant aralığına sahip olması ile beraber, 1930'lu yıllardan beri elektronik uygulamalar için kullanılmaktadır. Son otuz yıl boyunca ince film teknolojileri, ince film tranzistörler (TFTs), şeffaf iletken elektrotlar (TCEs) ve ince film fotovoltaik güneş hücreleri gibi uygulmalarda daha çok potansiyel vadetmesi sebebiyle, katkılanmış çinko oksit ile daha fazla ilgilenmektedir. Özellikle indiyum ve galyum katkılı çinko oksit (IZO), (GZO), (IGZO) ince filmler dikkate değer elektriksel ve optik özelliklerinden dolayı araştırmacıların daha çok ilgisini çekmekte ve yeni nesil esnek optoelektonik uygulamalar için iyi bir aday olarak göze çarpmaktadır.Bu tez çalışması, ince filmlerde, kaplama parametrelerinin, optik özellikler ve kristallik üzerindeki etkisini incelemektedir. Ayrıca, ince filmlerin, kimyasal bileşimleri, elektriksel ve şekilsel özellikleri oda sıcaklığında ve 200°C alltaş sıcaklığı altında büyütülen filmlerde karşılaştırmalı olarak çalışıldı. Öncelikle, basınç, plasma gücü ve Argon (Ar) gaz akışı gibi kaplama parametreleri farklı değerlerde değiştirilerek, katkılandırılmış ZnO filmler seri olarak RF- püskürtmeli kaplama tenkiği ile kaplandı. Sonrasında seçilmiş bir kaplama reçetesi alttaş sıcaklığı değiştirilerek test edildi. İyi yapışmış, eş dağılımlı, pürüzsüz ve yüksek oranda saydam filmler gözlendi. Literatür IZO ince filmlerin oda sıcaklığında kaplandığında amorf bir yapıya sahip olduğunu sölese de, bu çalışmada oda sıcaklığında kaplanan IZO ince filmlerin kristal bir yapıya sahip olduğunu gösterdi. Sonuçlar, kaplama esnasında alttaşın düşük miktarlarda ısıtılmasının hem IZO hem de GZO ince filmlerde IGZO ince filmlere oranla daha etkili olduğunu gösterdi. Her bir karakterizasyon aşamasının ayrı ayrı bahsedilecek olmasıyla beraber, düşük sıcaklığın, diğer karakterizasyonlara kıyasla; kristallik ve optik özelliklerde daha çok etkili olduğu gözlendi. Kalın filmler (~1 µm), film sertliği (H) ve elastikiyet katsayısını (E) içeren mekanik özelliklerin incelenmesi için büyütüldü. Zinc Oxide (ZnO) has been studied since 1930's as a candidate for the electronic applications, as it possesses a wide bandgap of 3.4 eV. While in the last 3 decades the technology of thin films were more interested in Doped zinc oxide (ZnO) for their promising potential for many applications including thin film transistors (TFTs), transparent conductive electrodes (TCEs), and thin-film photovoltaic solar cells. Mainly Indium doped and Gallium doped-zinc-oxide (IZO), (GZO) and (IGZO) thin films have drawn researchers' attention due to their remarkable electrical, optical properties, making them good candidate for the next generation flexible optoelectronic applications.This thesis work studies the effect of deposition parameters on the crystallinity and optical properties of the thin films. In addition, the chemical composition, electrical and morphological properties of the thin films were studied in a comparative form between room temperature (RT)-grown thin films and those gown with substrate heating at 200 °C. First, a series of doped ZnO thin films were deposited by radio frequency RF-sputtering at (RT), as a function of pressure, plasma power, and argon (Ar) flow. Then a chosen deposition recipe was tested with substrate heating. Well-adhered, uniform, smooth and highly transparent films were observed. Although Literature has shown that IZO thin films exhibit amorphous nature at RT-deposition, in this work it was observed that IZO thin films exhibits crystalline nature at RT. Results indicated that low substrate heating has affected both of IZO and GZO more than it has to IGZO Thin films. The low heat effect was more effective on the crystallinity and optical characteristics of these thin films more than its effect on their other characteristics, as it will be demonstrated as we go over each characteristic. Thicker films of (~1m) were grown in order to evaluate the mechanical properties, including film hardness (H) and Young's Modulus (E). 82

An atomic layer deposition (ALD) of monodispersed palladium (Pd) nanograins (approximate to 2 nm) onto electrospun polymeric nanofibers (NF) is presented. By ALD, monodispersed Pd nanograins with (111) exposed facets are decorated on the surface of the free-standing flexible nanofibrous webs (NW). The Pd nanograin-decorated free-standing NW exhibit catalytic reduction of 4-nitrophenol to 4-aminophenol. Even under low loading capacity (approximate to 20 mu g mg(-1)), Pd nanograins manifest effective catalytic performance which can be referred to direct exposure of Pd single crystalline highly interactive (111) plains with high surface area on the NW. The Pd nanograins and the interactive sites along with the high surface area NW yield effective catalytic reduction of 4-nitrophenol to 4-aminophenol with the catalytic reduction rate of 0.0531 min(-1). Pd nanograins display thermally tunable effective catalytic reduction properties with activation energy (E-a) of 1.705 J mol(-1) on varying the reaction temperature from 12 to 42 degrees C. Moreover, Pd nanograin-decorated NW are exhibited the effective reusable behavior with stable structural integrity even after repeated catalytic reactions. The approach of this study opens up synthesis and surface decoration of metal nanostructures onto NF through ALD with controlled size and facet orientation for designing reusable and free-standing flexible catalytic nanofibrous materials.

WOS: 000412681900013 An effective method for the fabrication of well designed nanocomposite for the catalytic reduction of 2,4,6-trinitrotoluene (TNT) was developed. Here, cubic palladium (Pd) nanoparticles were utilized for enhancing the interface properties, attachment quality, catalytic yield and stability after the catalysis reactions. Ligand controlled facet growth by the Br- anions during thermal decomposition of the palladium-precursor resulted with cubic shaped average similar to 13nm palladium nanocubes (Pd NC). The anisotropic Pd NC were utilized to decorate the surface of the zinc oxide (ZnO) nanolayers deposited by atomic layer deposition (ALD) technique on the electrospun polyacrylonitrile (PAN) nanofibers. Due to the polymeric nature of the electrospun PAN nanofibers, Pd NC decorated nanoweb is highly flexible and has a high surface area. For the sustainable Pd NC decoration on the ZnO surfaces coated on PAN nanofibers, anchor points were formed by the functional thiol groups which can facilitate the Pd NC attachment and stability on the ZnO surface. The -OH and alkyl thiol groups obtained via sol-gel reactions positioned on the ZnO layer providing a better interface between ZnO and Pd NC which cannot be obtained by pristine PAN nanofibers. Additionally, due to the increased surface interaction, geometrical positioning on fibers for a better intermediate complex formation and stability via soft-soft interaction, Pd NC decorated flexible polymeric electrospun nanoweb provided enhanced catalytic reduction of TNT in aqueous medium. Turkish Academy of Sciences-Outstanding Young Scientists Award Program (TUBA-GEBIP); TUBITAK BIDEB Fellowships for 2232-Post Doctoral programme [115C095] Prof. Arslan acknowledges TUBITAK BIDEB Fellowships for 2232-Post Doctoral programme (project no. 115C095) for financial support. T. U acknowledges partial support of The Turkish Academy of Sciences-Outstanding Young Scientists Award Program (TUBA-GEBIP). The authors acknowledge Dr. F. Topuz for the synthesis of Pd NC and thank to M. Guler for TEM investigations.

Hexagonal boron nitride (hBN) thin films were deposited on silicon and quartz substrates using sequential exposures of triethylboron and N 2 /H 2 plasma in a hollow-cathode plasma- assisted atomic layer deposition reactor at low temperatures ( ≤ 450 ° C). A non-saturating film deposition rate was observed for substrate temperatures above 250 ° C. BN films were charac- terized for their chemical composition, crystallinity, surface morphology, and optical properties. X-ray photoelectron spec- troscopy (XPS) depicted the peaks of boron, nitrogen, carbon, and oxygen at the film surface. B 1s and N 1s high-resolution XPS spectra confirmed the presence of BN with peaks located at 190.8 and 398.3 eV, respectively. As deposited films were polycrystalline, single-phase hBN irrespective of the deposition temperature. Absorption spectra exhibited an optical band edge at ~ 5.25 eV and an optical transmittance greater than 90% in the visible region of the spectrum. Refractive index of the hBN film deposited at 450 ° C was 1.60 at 550 nm, which increased to 1.64 after postdeposition annealing at 800 ° C for 30 min. These results represent the first demonstration of hBN deposi- tion using low-temperature hollow-cathode plasma-assisted sequential deposition technique. © 2014 The American Ceramic Society.

Cataloged from PDF version of article. We report on the synthesis and photocatalytic activity (PCA) of electrospun poly(acrylonitrile) (PAN) nanofibrous mat decorated with nanoneedles of zinc oxide (ZnO). Apart from a detailed morphological and structural characterization, the PCA has been carefully monitored and the results are discussed elaborately when juxtaposed with the photoluminescence. The present hierarchal homoassembled nanostructures are a combination of two types of ZnO with diverse optical qualities, i.e. (a) controlled deposition of ZnO coating on nanofibers with dominant oxygen vacancies and significant grain boundaries by atomic layer deposition (ALD), and (b) growth of single crystalline ZnO nanoneedles with high optical quality on the ALD seeds via hydrothermal process. The needle structure (similar to 25 nm in diameter with an aspect ratio of similar to 24) also supports the vectorial transport of photo-charge carriers, which is crucial for high catalytic activity. Furthermore, it is shown that enhanced PCA is because of the catalytic activity at surface defects (on ALD seed), valence band, and conduction band (of ZnO nanoneedles). PCA and durability of the PAN/ZnO nanofibrous mat have also been tested with aqueous solution of methylene blue and the results showed almost no decay in the catalytic activity of this material when reused. (C) 2014 Elsevier B.V. All rights reserved.

Cataloged from PDF version of article. Rutile TiO2 nanorods on fluorine-doped thin oxide glass substrates via the hydrothermal technique were synthesized and decorated with a sputtered CdTe layer to fabricate a core-shell type n-TiO2/p-CdTe solar cell. Absorbance spectrum verified the absorption contribution of both TiO2 and CdTe to the absorption process. The solar cell parameters, such as open circuit voltage, short circuit current density, fill factor and power conversion efficiency were found to be 0.34 V , 1.27 mA cm(-2), 28% and 0.12%, respectively. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hafnia (HfO2) hollow nanofibers (HNs) were synthesized by atomic layer deposition (ALD) using electrospun nylon 6,6 nanofibers as templates. HfO2 layers were deposited on polymeric nanofibers at 200 degrees C by alternating reactant exposures of tetrakis(dimethylamido) hafnium and water. Polymeric nanofiber templates were subsequently removed by an ex situ calcination process at 500 degrees C under air ambient. Morphological and structural characterizations of the HN samples were conducted by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Freestanding network of HfO2 HNs was found to be polycrystalline with a monoclinic crystal structure. Elemental composition and chemical bonding states of the resulting HfO2 HNs were studied by using X-ray photoelectron spectroscopy. The presence of HfO2 was evidenced by high resolution scans of Hf 4f and O 1s with binding energies of 16.3-17.9 and 529.6 eV, respectively. Combination of electrospinning and ALD processes provided an opportunity to precisely control both diameter and wall thickness of the synthesized HfO2 HNs. (C) 2013 Elsevier B. V. All rights reserved.

Date of Conference: 26 June-1 July 2016 The design, fabrication and characterization of a 2×8 patch antenna array operating in the IEEE 802.11ad frequency band (57-66 GHz) is presented. The design is based on two-layer structures, where the radiating patches placed on top substrate are fed by conductor backed coplanar waveguide (CPW)-fed loop slots, which are placed on the bottom substrate. The top layer is formed by using a low-cost pyrex (ϵr = 4.9, tani = 0.01) substrate of 500μm thickness. The pyrex is then etched away to a thickness of 100μm, where 400μm of air volume is formed underneath. This approach does not only benefit from the low-cost feature of pyrex but also exploits the low-loss nature of air. The thin layer of pyrex is solely used for mechanical support for the radiating patches while the air provides good RF-environment for the array. The bottom substrate housing the CPW feed network is an RF-compatible and microfabrication friendly quartz (ϵr = 3.9, tanδ = 0.0002) of 525μm thickness. The simulations indicate a good maximum realized gain of 19.3 dBi of which variation over ∼ 17% bandwidth is relatively constant changing from 17-19.3 dBi. © 2016 IEEE.

Date of Conference: 19-21 April 2016 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.

Date of Conference: 19-21 April 2016 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.

Perovskit tipi ferroelektirik oksit malzemeler arasından SrTiO3 (STO) ve BaSrTiO3 (BST) ince filmler potansiyel oksit tabanlı elektronik uygulamalar açısından ilgi uyandırıcı hale gelmiştir. Fakat STO ve BST ince filmlerin güvenirlilikleri ve verimlilikleri mikroyapılarına olduğu gibi optik ve elektriksel sabitlerine de ekseriyetle bağlıdır.STO ve BST ince filmler oda sıcaklığında Si (100), UV sınıfı kaynaşmalı silika, quartz alttaş üzerine ve TiO2 nanofiberler üzerine saçtırma metodunun radyo frekansı ile çalışan magnetronu ile farklı plazma gücü, farklı oksijen karıştırma oranı (OKO) ve farklı depolama basıncı kullanılarak depolanmıştır. Tavlama işleminden geçmeyen örnekler depolama koşullarından bağımsız olarak amorf yapı da nanokristal mikro yapı göstermıştir. Ayrıca tavlama çalışmasında beş farklı sıcaklığın etkisi etkisi amorf büyüyen stokiyometrik RF-saçtırma yöntemi ile büyütülmüş filmler üzerinde incelenmiştir. Bütün filmler görünür bölgede yüksek geçirgenliğe sahiptir ve STO and BST filmler belirgin soğurma bölgesi sergiledikleri görülmüştür: Direk ve indirek olan band aralığı hesaplamaları STO filmlerin band aralığının 2.32 ile 4.55 eV aralığında olduğunu göstermiştir. 3 mTorr basınçda depolanan STO filmlerin, BST ve tavlama çalışmasında kırılma indisinin ise OKO ve tavlama ile arttığı gözlemlenmiştir. Fakat 5 mTorr da depolanan filmler için bir bağlantı bulunamamıştır. BST filmlerin kırılma indilslerinin 550 nm deki değerlerinin 1.90 ile 2.07 arası nda depolama koşuluna bağlı olarak değiştiği gözlemlenmiştir. BST filmlerin band aralığının 3.60 ile 4.30 eV aralığında olduğu hesaplanmıştır. STO filmlerin dielektrik sabitleri Ag/STO/p-Si yapısından frekans ya da voltaj bağımlı kapasitans ölçümünden alınan kapasitans değerinden hesaplanmıştır. Dielektrik sabiti en yüksek 100 olarak bulunmuştur. Tüm STO örneklerin yük depolama kapasitelerinin 2.5 μC/cm2 dan fazla olduğu ve dielektirik kayıpların düşük olduğu not edilmiştir (100 kHz için 0.07 den düşük). 800°C de 1 saatlık tavlamanın etkisiyle polikristal BST filmler elde edilmiş ve kırılma indisinin ve dielektrik sabitini arttırdığı not edilmiştir. Fakat optik geçirgenliği azalmıştır. Frekansa bağlı dielektirik sabiti değeri 46 ile 72 arasındadır ve ~1μA değerinde düşük kaçak akım gözlemlenmiştir. Sonuçlar düşük sıcaklıkta depolanan STO ve BST filmlerin çeşitli aygıt uygulamarında potansiyeli olduğunu göstermektedir. Among the several perovskite ferroelectric oxides, SrTiO3 (STO) and BaSrTiO3 (BST) thin films have attracted significant attention due to their potential applications in oxide-based electronics. However, reliability and performance of STO and BST thin films depend usually on the precise knowledge of microstructure, as well as optical and electrical properties.STO and BST thin films were deposited at room-temperature on Si (100), UV-grade fused silica, quartz substrates and TiO2 nanofibers by radio frequency (RF) magnetron sputtering using different plasma power, oxygen mixing ratios (OMRs) and deposition pressure levels. As-deposited thin films showed amorphous-like nanocrystalline microstructure almost independent of the deposition conditions. Influence of post-deposition annealing at various temperatures of RF sputtered STO thin films were also investigated. All films were found to be highly transparent (>75%) in the visible region, and both STO and BST films exhibited well defined main absorption edges: the calculated indirect and direct band gaps for STO films were in the range of 2.32 to 4.55 eV. The refractive index of the STO films increased with OMR and post-deposition annealing for 3 mTorr deposition for STO, BST and STO annealing study. However, there is no correlation for 5 mTorr deposition. The refractive indices of BST films were in the range of 1.90-2.07 at 550 nm depending on their deposition conditions. The optical band gap of the BST films were calculated the ranging in 3.60 to 4.30 eV.Electrical dielectric constant values of the STO thin films were extracted from frequency or voltage dependent capacitance measurements using micro-fabricated Ag/STO/p-Si device structures. High dielectric constant values reaching up to 100 were obtained. All STO samples exhibited more than 2.5 μC/cm2 charge storage capacity and low dielectric loss (less than 0.07 at 100 kHz). Post-deposition annealing at 800°C for 1 h resulted in polycrystalline BST thin films with increased refractive indices and dielectric constants, along with reduced optical transmission values. Frequency dependent dielectric constants were found to be in the range of 46-72, and the observed leakage current was very small, less than 1 μA. Our experimental results show that these low temperature grown STO and BST films have the potential for various electrical applications. 135

Gallium nitride films were grown by hollow cathode plasma-assisted atomic layer deposition using triethylgallium and N-2/H-2 plasma. An optimized recipe for GaN film was developed, and the effect of substrate temperature was studied in both self-limiting growth window and thermal decomposition-limited growth region. With increased substrate temperature, film crystallinity improved, and the optical band edge decreased from 3.60 to 3.52 eV. The refractive index and reflectivity in Reststrahlen band increased with the substrate temperature. Compressive strain is observed for both samples, and the surface roughness is observed to increase with the substrate temperature. Despite these temperature dependent material properties, the chemical composition, E-1(TO), phonon position, and crystalline phases present in the GaN film were relatively independent from growth temperature. (C) 2015 American Vacuum Society.

Conference name: CLEO: Science and Innovations 2016 Date of Conference: 5–10 June 2016 The CO2 polishing of femtosecond laser micromachined channels is studied. The surface quality before and after polishing is observed with naked eye and optical microscope. The method improves imaging of microspheres.

In this work, the authors have performed sequential pulsed chemical vapor deposition of ternary BxGa1-xN and BxIn1-xN alloys at a growth temperature of 450 degrees C. Triethylboron, triethylgallium, trimethylindium, and N-2 or N-2/H-2 plasma have been utilized as boron, gallium, indium, and nitrogen precursors, respectively. The authors have studied the compositional dependence of structural, optical, and morphological properties of BxGa1-xN and BxIn1-xN ternary thin film alloys. Grazing incidence X-ray diffraction 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. (C) 2015 American Vacuum Society.