bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Electrical Properties in Si Ion Implanted GaN Layer as A Function of Dose and Energy
Authors: Satoh Masataka , Saitoh T , Nomoto K , Nakamura T 
Published: April 2011

ABSTRACTThe sheet resistance and sheet carrier concentration for Si ion implanted GaN have been investigated as a function of Si ion dosages and ion's energy using van der Pauw method and Hall effect measurement. Si ion implanted GaN is annealed at 1200 °C for 10 sec in N2 gas flow with 50 nm-thick SiNx cap layer to avoid dissociation of GaN. For Si ion energy of 30 keV, the sheet resistance is decreased from 103 to 56 ohm/sq. for the dose ranging from 1 × 1014 to 2 × 1015/cm2. For the Si dose larger than 2 × 1015/cm2, the sheet carrier concentration is saturated around 1 ×s 1015/cm2. Si ion implanted GaN with energy of 50, 80, and 120 keV at a dose of 2 × 1015/cm2 also reveal the sheet carrier concentration of about 1 × 1015/cm2 with the decrease of electron mobility. It is suggested that the implanted Si donors are strongly compensated by the residual implantation-induced defects.
Electron-Beam-Induced Dissociation of Boron-Deuterium Pairs in Diamond
Authors: Barjon Julien , Chevallier Jacques , Jomard François , Baron Céline , Deneuville Alain 
Published: April 2011

ABSTRACTThe diffusion of deuterium in boron-doped homoepitaxial diamond films leads to the passivation of boron acceptors via the formation of B-D pairs. In this letter, the stability of these complexes is investigated under the stress of a low-energy (10keV) electron-beam irradiation at low temperature (∼100K). The dissociation of the complexes is evidenced by cathodoluminescence spectroscopy and is shown to result in the reactivation of most acceptors. The dissociation yield per incident electron is found to be strongly dependent on the e-beam current, which suggests a dissociation involving a vibrational excitation of the complexes by hot electrons.
The Mechanism for Ultrananocrystalline Diamond Growth: Experimental and Theoretical Studies
Authors: May Paul William , Mankelevich Yuri A. 
Published: April 2011

ABSTRACTAr/CH4/H2 gas mixtures have been used to deposit microcrystalline diamond, nanocrystalline diamond and ultrananocrystalline diamond films using hot filament chemical vapor deposition. A 3-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor. Using the experimental and calculated data, we show that the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH3 radicals and other C1 radical species reacting with dangling bonds on the surface. Proposed formulae for growth rate and average crystal size are tested on both our own and published experimental data for Ar/CH4/H2 and conventional 1%CH4/H2 mixtures, respectively.
DNA Bonding to CVD Diamond Probed by Scanning Electron-, Fluorescence-, and Atomic force- Microscopy
Authors: Nebel Christoph E. , Uetsuka Hiroshi , Rezek Buhuslav , Shin Dongchan , Tokuda Norio , Nakamura Takako 
Published: April 2011

ABSTRACTDouble stranded desoxyribonucleic acid (ds-DNA) layers, bonded to hydrogen terminated polycrystalline diamond, are characterized by scanning electron (SEM), fluorescence (FM), and atomic force microscopy (AFM). DNA grafting has been achieved using photochemical bonding of ω-unsaturated 10-amino-dec-1-ene molecules. SEM detects local variations of electron affinities on polycrystalline diamond, revealing distinct grain structures. FM applied on fluorescence labeled ds-DNA show laterally varying intensities of typically 20 %, which resembles also grain structure as detected by SEM. Contact and tapping mode AFM characterization reveal a tilted DNA bonding to diamond, dense layer formation which gives rise to smoothening of surface properties. The lateral density variation of DNA is attributed to local variations of the photo-electron emission efficiency which affects the photochemical attachment chemistry of amine linker molecules to diamond.
Synthetic diamond devices for radiotherapy applications: Passive and active dosimetry
Authors: Descamps Caroline , Tromson Dominique , Mer Christine , Nesladek Milos , Bergonzo Philippe 
Published: April 2011

ABSTRACTFor all its remarkable properties, diamond is well known as an interesting material for radiation detection and more particularly for medical uses. Natural diamond use for detection application is limited because of its high cost and the severe gem selection needed to fabricate reproducible and reliable devices. The recent progress of the chemical vapour deposition (CVD) technique offers new possibilities in the fabrication of ionisation chambers as well as thermoluminescent dosimeters for the particular field of radiotherapy. This paper presents the use of CVD diamond for both applications.For the use of diamond for TL applications, the purpose of this study was to control the trapping levels in the material with deliberate incorporation of impurities in CVD diamond film during the growth.For ionisation chamber fabrication, the aim was to purposely incorporate defects (with nitrogen incorporation) in the material in order to better understand the modification of the charge transport during irradiation. The first results obtained when the device is used to monitor the beam fluency of a medical accelerator facility are presented here.For both applications, several preliminary dosimetric parameters were probed and namely the reproducibility of the response, the linearity of the signal with the dose, and for TL dosimeters, both the optical and thermal fadings were carefully studied. Results are extremely encouraging and lead to interesting prospects for the use of diamond for dosimetry.
Low Temperature Aqueous Polymeric Precursor Processing of ZnO:Er Using a Glycerol Chelating Agent
Authors: Choppali Uma , Gorman Brian P 
Published: April 2011

ABSTRACTErbium doped ZnO (ZnO:Er) is considered to be a suitable candidate for fabrication of the current injection optical devices. Although ZnO: Er thin films have been synthesized previously by pulsed laser deposition, we present low – temperature processed ZnO:Er thin films from polymeric precursors. In this work, we study the effect of variation of Er doping concentration on the structural and electrical properties of the synthesized films. ZnO nanoparticles of varied Er doping concentration, derived from the prepared polymeric solution, has been spin – coated onto surface modified substrates, and annealed at different temperatures. The effect of Er doping concentration on film grain size and strain was analyzed using X-ray diffraction. XRD data reveals that doping of Er ions reduces compressive strain considerably in the films. It is speculated that the presence of larger Er cations in ZnO cause tensile stress, which neutralizes the inherent compressive stress, observed in undoped ZnO, significantly decreasing and hence, making the films stress free. Crystallite size of ZnO:Er thin films, annealed at 600°C, was calculated to be approximately 12 nm using Scherrer's equation. The surface morphology of the thin films was characterized by both SEM and AFM. Electrical resistivity of the films, annealed at 450oC, was calculated to be 290 Ω-m for 5 at wt% and 125 Ω-m for 10 at wt% ZnO:Er films.
A Comparison of the Mechanical Properties and the Impact of Contact Induced Damage in a- and c- Axis ZnO Single Crystals
Authors: Coleman Victoria A. , Bradby J E , Jagadish C , Phillips M R 
Published: April 2011

ABSTRACTNanoindentation studies were conducted on a-axis oriented ZnO single crystals. The mechanical properties and deformation mechanisms were monitored and compared to previously determined data from c-axis material. Hardness and modulus values reveal that a-axis ZnO is significantly softer than c-axis material (measured hardness of 2 ± 0.2 GPa) and behaves much more plastically. Additionally, the influence of contact induced damage upon the defect structure of a-axis material was also examined using cathodoluminescence spectroscopy and monochromatic imaging to monitor the luminescence from indent sites. Deformation directly under the indent site enhanced the occurrence of red defect luminescence, and was attributed to a native defect in ZnO that has a higher formation energy than the defects responsible for the green and yellow visible defect bands, which were present in the ZnO during growth and were found to cluster to the indent site during annealing.
Acceptors in ZnO Studied by Photoluminescence
Authors: Reshchikov Michael A , Garbus James , Lopez Gabriel , Ruchala Monica , Nemeth Bill , Nause Jeff 
Published: April 2011

ABSTRACTWe studied photoluminescence from melt-grown ZnO crystals annealed in air ambient at different temperatures. Along with intense and sharp excitonic lines, we observed several broad bands presumably related to deep acceptors. Two luminescence bands peaking at 1.95 and 2.15 eV at 10 K were studied in detail at different temperatures. The 1.95 eV band has been attributed to transitions from shallow donors to yet unidentified deep acceptor. Very slow non-exponential decay of this band at low temperatures supports such an assumption.
Interface and Luminescence Properties of Pulsed Laser Deposited MgxZn1-xO/ZnO Quantum Wells with Strong Confinement
Authors: Heitsch Susanne , Zimmermann Gregor , Müller Alexander , Lenzner Jörg , Hochmuth Holger , Benndorf Gabriele , Lorenz Michael , Grundmann Marius 
Published: April 2011

ABSTRACTMgxZn1-xO/ZnO/MgxZn1-xO quantum wells (QWs) (0.12 ≤ x ≤ 0.15) have been grown on a-plane sapphire substrates by pulsed laser deposition. The nominal ZnO well layer thickness lies between 1.2 nm and 6 nm. Atomic force microscopy (AFM) investigations at ZnO/MgxZn1−xO heterostructures show the film-like structure of the ZnO layers. Their root mean square surface roughness of ∼ 0.5 nm gives information about the interface roughness in the QWs. AFM results from the MgxZn1−xO barrier layers show the same surface structure and roughness. We confirmed the lateral homogeneity of the Mg distribution in the MgxZn1−xO barrier layers by scanning cathodoluminescence measurements. The QWs show a bright and laterally homogeneous luminescence, suggesting good crystalline quality of the ZnO wells. The measured QW photoluminescence energies agree well with calculated values and display the presence of the quantum-confined Stark effect. As a result of quantum confinement a high-energy shift of the ZnO excitonic photoluminescence of 222 meV is observed in the thinnest QW.
Raman Scattering Characterization of Implanted ZnO
Authors: Alarcon-Llado Esther , Cusco Ramon , Artus Luis , Gonzalez-Diaz German , Martil Ignacio , Jimenez Juan , Wang Buguo , Callahan Michael 
Published: April 2011

ABSTRACTIn this work we investigate the lattice damage induced in ZnO implanted with potential group V acceptors by means of Raman scattering. ZnO samples were implanted with N and P to high doses and Raman spectra were obtained prior and after rapid thermal annealing (RTA). Characteristic disorder-activated modes are observed in the spectra that can be used to assess the degree of lattice damage. ZnO samples were also implanted with native Zn+ and O+ ions under similar conditions to study specific effects of implantation with N+ and P+. As revealed by the intensity of disorder-activated bands, the implantation induced lattice damage is considerably higher for Zn+ than for the lighter O+ ion. In samples implanted with N+ additional Raman peaks emerge that are not observed either in the samples implanted with the native Zn+ and O+ ions or in the samples implanted with P+, thus pointing to a local vibrational mode of N or a N complex as the origin of these modes. Disorder-activated features are fully removed by RTA, indicating a high degree of lattice recovery by RTA even for the heavily damaged ZnO samples implanted with Zn+.
Fabrication OF ZnO and ZnMgO Thin Films and UV Photodetectors by Mist Chemical Vapor Deposition Method
Authors: Kawaharamura Toshiyuki , Kawaharamura Toshiyuki , Nishinaka Hiroyuki , Fujita Shizuo 
Published: April 2011

ABSTRACTDeposition of Zn1-xMgxO thin films on glass substrates has been investigated by the simple and cost-effective mist CVD technique. A water solution of zinc acetate and magnesium acetate was used as the source of Zn and Mg. The solution was ultrasonically atomized, and the aerosols hence formed were supplied by the N2 carrier gas to the substrates. The band gap energy of ZnMgO was successfully controlled from 3.25 eV (ZnO) to 3.75 eV with the concentration ratio [Mg]/([Zn]+[Mg]) in the solution. The transparency in the visible region was higher than 90% and the surface RMS roughness was 7.5 nm (an example for ZnO) despite the polycrystalline structure; they are satisfactory for the optical applications. A UV photodetctor with interdigital electrode structure on the ZnMgO surface was fabricated, where the photoresponsivity of 2.6 A/W at 350 nm and the lowest detectable power of about 1 μW were obtained. Although these values are satisfactory for the simple UV detection but the existence of deep defects is deteriorating the dynamic response of the detector device.
Optical and Electrical Properties of Gallium-Doped Mg15Zn85O Thin Films
Authors: Wei Wei , Bhosle Vikram , Jin Chunming , Narayan Roger J 
Published: April 2011

ABSTRACTGa-doped Mg0.15Zn0.85O thin films have been grown on fused silica substrates at 350°C with four different gallium concentration values using pulsed laser deposition. X-ray diffraction results indicate that these films were textured with c-plane parallel to the substrate surface. The bandgap of the films were determined based on the absorption measurements. The bandgaps of the Ga-doped thin films shifted to higher energy with respect to that of the unalloyed Mg0.15Zn0.85O thin film due to the band filling effect of electron distribution in the conduction band. Resistivity of the films was measured with four-point probe at temperatures from 295 K to 15 K. The activation energy of the gallium dopants was extracted by fitting the temperature dependent curve of resistivity.
Modification of Blinking Statistics in Solid State Quantum Dot/Conjugated Organic Polymer Composite Nanostructures
Authors: Hammer Nathan I , Early Kevin T , Odoi Michael Y , Tangirala Ravisubhash , Sill Kevin , Emrick Todd , Barnes Michael D 
Published: April 2011

ABSTRACTFluorescence intermittency, or “blinking” in quantum dot systems has been the subject of great interest since the first observation of this phenomenon nearly 10 years ago. The stability of quantum dot fluorescence emission is especially important in the context of photovoltaic, optoelectronic, and biological applications, where device performance, or the ability to track labeled particles, is affected adversely by fluorescence intermittency. Single-molecule spectroscopy combined with atomic force microscopy measurements reveal that CdSe quantum dots functionalized with oligo(phenylene vinylene), OPV, ligands exhibit modified optical properties such as suppression of blinking when compared to conventional TOPO covered or ZnS-capped CdSe quantum dots. The blinking suppression is shown to be highly sensitive to the degree of ligand coverage on the quantum dot surface and this effect is interpreted as resulting from charge transport from photoexcited OPV into vacant trap sites on the quantum dot surface. This direct surface derivatization of quantum dots with organic ligands also enables a “tunable” quantum dot surface that allows dispersion of quantum dots in a variety of polymer supported thin films without phase segregation. This facilitates straightforward inclusion of these new hybrid materials into solid state formats and suggests exciting new applications of composite quantum dot/organic systems in optoelectronic systems.
Enhanced Luminescence Efficiency from Hydrogel Microbead Encapsulated Quantum Dots
Authors: Neogi Arup , Ghosh Santaneel , Li Jianyou , Cai Tong , Hu Zhibing 
Published: April 2011

ABSTRACTIn this paper, a novel quantum dot (QD) based nanomaterial system is presented for efficient FRET analysis. The quantum dots have been embedded in hydrogel microspheres based on poly(N-isopropylacrylamide) (PNIPAM) a thermoresponsive polymer that undergoes a volume phase transition across the low critical solution (LCST). The optical properties of the quantum dots entrapped within the gel microspheres has been modified due to change in refractive index, volume density of the surrounding hydrogel medium. The QDs encapsulated in the PNIPAM microspheres showed 100–200 % enhancement in the PL efficiency as the microgels shrank at the temperature above the LCST temperature of the gel.
Elastic Energy Relaxation in Buried Quantum Dots
Authors: Chaldyshev Vladimir V , Kolesnikova Anna L. , Romanov Alexei E. 
Published: April 2011

ABSTRACTWe theoretically analyze three models, which correspond to three different ways of the elastic energy relaxation in buried quantum dots. The first model considers formation of a pair of prismatic dislocation loops. One of them lies on dot/matrix interface, whereas the other is a satellite and locates in the adjacent matrix. The second model also includes the satellite loop and differs from the first one by non-local reduction of the dot plastic distortion. The origin of the satellite loop is the materials conservation requirement. The third model considers the case when this requirement is violated and only the misfit dislocation loop is formed. We determine the critical radii of the dots and loops, as well as the dependence of the satellite loop size on the dot size. The model calculation are compared to the relevant experimental data.
Controlling Lateral Ordering of InGaAs Quantum Dots with Arsenic Background
Authors: Marega Euclydes , Waar Ziad Abu , Hussein Mohammad , Salamo Gregory 
Published: April 2011

ABSTRACTWe present in this work a method to control lateral ordering of In0.4Ga0.6As quantum dots (QDs) using the surface anisotropic and the growth environment. We have shown experimentally that using As2 molecules instead of As4 as a background flux is promising to control the diffusion of adatoms in away to make it possible to control the ordering of In0.4Ga0.6As QDs together with the GaAs surface properties specially for GaAs (100) surfaces. For GaAs (n11)B surfaces the As4 provides a better two dimension ordering than the As2 environment. Our results are consistent with reported experimental and theoretical studies on surface structure and diffusion mechanism over GaAs surface.
Nano-Graphitization in Amorphous Carbon Films via Electron Beam Irradiation and the Iron Implantation
Authors: Aizawa Tatsuhiko , Iwamura Eiji 
Published: April 2011

ABSTRACTNano-graphitization from amorphous carbon state is assisted by the electron beam irradiation. An inter-columnar region in the amorphous carbon films with low atomic and electron densities is controlled to have a graphitic structure with relatively low dose electron beam irradiation. This amorphous carbon ? beam interaction generates a new type of carbon hybrids where amorphous carbon phase columns are sustained by the graphitic inter-columnar network. This hybrid film has an exotic mechanical and tribologic response: extraordinary reversible deformability up to 8 – 10 % normal strain, high wearing resistance and low friction at high normal pressure. A combination of iron implantation with this electron irradiation provides us the other nano-graphitization process. An amorphous carbon film including the implanted iron atoms is chemically modified to have a columnar graphitic structure by the electron beam irradiation. In this post-implantation electron beam irradiation, the basic graphitic units with 1-2 nm in size are controlled to align vertically along the film thickness. This type of nano-graphitization has a strong dependency on the iron doses before electron beam irradiation. The above two types of nano-graphitization provides us a new tool to explore the functionalized structural thin films in application.
Room-Temperature Nanoimprint Lithography
Authors: Matsui Ken-Ichiro , Matsui Shinji 
Published: April 2011

ABSTRACTRoom-temperature nanoimprint lithography (RT-NIL) using spin-coated hydrogen silsesquioxane (HSQ) resin as the replication material was developed. HSQ pattern with 50 nm linewidth was successfully obtained by the RT-NIL. Postbaking temperature dependence of a HSQ imprinted depth on a mold linewidth was investigated. HSQ imprinted depth had a dependence on the mold linewidth. This revealed that the RT-NIL is suitable for the linewidths of below 1 mm. Furthermore, we have also developed a new imprinting technique that uses liquid-phase hydrogen silsesquioxane (HSQ) as an alternative to the spin-coated HSQ resin. The liquid-phase HSQ imprint technique enabled fabrication of various HSQ patterns with a wide range of linewidths from 25 nm to 300 mm. Arbitrary patterns, including both submicron and greater than 100 micron patterns, were simultaneously replicated with a one-step imprint process, something very difficult to accomplish with spin-coated HSQ. Moreover, after imprinting, the residual HSQ layer in the compressed area was less than 10 nm thick.
Nanostructural Evolution in Non-epitaxial Growth of Thin Films
Authors: Hu Minghui , Noda Suguru , Komiyama Hiroshi 
Published: April 2011

ABSTRACTThe initial growth of non-epitaxial thin films was studied and discussed using the concept that thermodynamics controls the unit-structure within the surface diffusion length of deposits, whereas kinetics controls the ensemble-structure on a large scale. Three basic topics, growth mode (island shape), crystalline (island inner) structure, time-dependent properties of island ensemble (island size, distance, and density), are summarized based on the investigation of thin film growth of metals on TiO2, Cu on SiO2 and Ti/SiO2. This study provides fundamental understanding of structural control during thin film growth, and further can be applied to various advanced devices for electronics, photonics, catalysis, and energy applications.
Process Integration of Composite High-k Tunneling Dielectric for Nanocrystal Based Carbon Nanotube Memory
Authors: Ganguly Udayan , Hou Tuo-Hung , Kan Edwin Chihchuan 
Published: April 2011

ABSTRACTRecently, metal nanocrystal based carbon nanotube memory has been demonstrated with sub-5V low bias programming, single electron sensitivity but poor room temperature retention. The process integration of an ultra-thin tunnel dielectric is essential for lateral, vertical scaling and reliable room temperature operation. Low defect density and conformal deposition on the nanotube are required to enhance the performance as a tunnel barrier. Additionally, Au contamination in the CNT decreases the on/off current ratio in the CNTFETs by substantially increasing the off current. Consequently, the dielectric should function as a good diffusion barrier for Au in the nanocrystals. We have explored composite tunneling dielectric film with SiO2 seed layer for conformal high-k deposition to demonstrate minimal Au contamination and improved retention. Room temperature retention of better than three days has been observed.
A Nanodamascene Process to be used as a Building Block for Nanodevices
Authors: Dubuc Christian , Beauvais Jacques , Drouin Dominique 
Published: April 2011

ABSTRACTWe report a single-electron transistor concept and its related process enabling the fabrication of ultrasmall junction capacitance. The method utilizes a nanodamascene approach where trenches in silicon oxide are covered with a filling material and planarized with chemical mechanical polishing. Single-electron transistors fabricated with this approach were characterized up to 433 K and demonstrated that the nanodamascene process has high resolution, is relatively simple and is highly scalable.