bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Deformation of Metal Films Under Controlled Pressure for Generating Ultra-flat Metal Surfaces
Authors: Vj Logeeswaran , Chan Mei-Lin , Islam M.Saif , Horsley David A. , Wu Wei , Wang Shih Yuan , Williams R. Stanley 
Published: April 2011

ABSTRACTWe present a technique to generate ultra-smooth surfaces and direct pattern imprinting on thin metal films by flattening the bumps and spikes of a freshly vacuum deposited metal film. The technique was implemented by using a small footprint mechanical imprint press that has the capability to vary the applied pressure from 100MPa to 600MPa. The mechanical press was incorporated with a tactile force sensor that enabled direct monitoring of the applied pressure. We demonstrated the feasibility of the technique on an e-beam evaporated silver (Ag) metal film with thickness ranging from 150Å (optically thin) to 1000Å (optically thick). The film was deposited on double-polished (100)-oriented silicon surface and double-polished borosilicate glass, resulting in a varying degree of film smoothness. The surface morphology of the pressed thin film was then studied using atomic force microscopy and SEM. Our demonstration with the e-beam evaporated silver thin film exhibits the potential for applications in decreasing the scattering-induced losses in optical metamaterials, plasmonic nanodevices and electrical shorts in molecular-scale electronic devices.
Chemical Routes to Ultra Thin Films for Copper Barriers and Liners
Authors: Ekerdt John , Shin Jinhong , Winkenwerder Wyatt , Kim Hyun-Woo , Thom Kelly , Hwang Gyeong S , Agapiou Kyriacos , Jones Richard A 
Published: April 2011

ABSTRACTTriruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.
Phase-Change Nanowires for Non Volatile Memory
Authors: Cui Yi , Meister Stefan , Peng Hailin 
Published: April 2011

AbstractWe report the synthesis of GeTe, Sb2Te3 and Ge2Sb2Te5 nanowires via a gold-catalyzed vapor-liquid-solid mechanism. The nanowires are studied via electron microscopy and energy-dispersive X-ray spectrometry and are found to be single crystalline. For electrical measurements contact to individual nanowires is made via electron-beam lithography. The nanowires can be switched from their initially low resistance state to a higher resistance state by applying a 200ns voltage pulse. Switching back to the low resistance state is possible via annealing. Electric force microscopy studies show the switching takes place at the metal-nanowire contact.
Effects of Different Fluorine Dopants on the Properties of the Tin Oxide Window Layer and CdTe/CdS Solar Cell
Authors: Li Xiaonan , Bai Mailasu , Pankow Joel , Asher Sally E. , Moutinho Helio Moutinho R. , Gessert Tim 
Published: April 2011

AbstractConductive tin-oxide (SnO2) film is doped by group V or VII elements. Of all possible dopants, fluorine provides n-type SnO2 with the best electronic and optical properties. However, the commonly used fluorine dopant, bromotrifluoromethane (CBrF3), is a greenhouse gas. Thus, an alternative fluorine source is needed. In this work, we compared CIF3 as a fluorine dopant to CBrF3. With CBrF3 dopant, optimized carrier concentration and electron mobility values can reach to mid 1020 cm-3 and over 40 cm2/V-s, respectively. After carrier concentration saturates, the electronic mobility continues to improve with an increase of CBrF3 dopant concentration. As a comparison, to achieve similar carrier concentration, far less CIF3 dopant is required. However, the electron mobility is lower (<30 cm2/V-s) and does not improve with an increase of dopant concentration. The low electron mobility increases the optical absorption, especially of long wavelengthes. Considering CdTe/CdS solar cell efficiency, the device with a CIF3-doped SnO2 window layer provides the lower photocurrent.
Transparent Back Contacts in CdTe/CdS: Evaluation for Tandem Cells
Authors: Vasko Anthony , Vasko Anthony , Compaan Alvin D , Marsillac Sylvain 
Published: April 2011

AbstractCdS/CdTe solar cells with 2.3 μm CdTe were prepared with four different types of p+/n+ transparent back contacts (TBCs) - ZnTe:Cu/ZnO:Al, ZnTe:N/ZnO:Al, ZnTe:Cu/ITO, and ZnTe:N/ITO. ZnTe:N/ITO was found to give the best results. This back contact was then used to make cells of lesser (1.8 μm and 0.7 μm) CdTe thickness, in those cases giving good performance up to 9.1% efficiency. Bifacial J-V was performed on all cells with the optimum ZnTe:N/ITO back contact.
Understanding Metastable Defect Creation in CIGS by Detailed Device Modeling and Measurements on Bifacial Solar Cells
Authors: Lee Jin Woo , Needleman David Berney , Shafarman William N. , Cohen J. David 
Published: April 2011

AbstractWe present a compensated donor-acceptor conversion model to explain the metastable light-induced changes in the performance of CIGS solar cells. In this model, compensating donors plays the role of recombination channel. Modeling using SCAPS-1D yielded reasonable fits to the I-V curves in different metastable states, matching the experimentally observed decreases in short circuit current and fill factor as well as the lack of change in open circuit voltage. Comparison of the experimental results from bifacial solar cells and SCAPS simulations strongly supports the compensated donor-acceptor conversion model both qualitatively and quantitatively.
On Industrial Production of Thin Film CdTe PV Modules
Authors: Bonnet Dieter 
Published: April 2011

AbstractDue to its basic physical and chemical properties CdTe has become a favored base material for thin film solar cells using robust, high-throughput manu-facturing procedures. The technology shows significant potential for attaining cost levels of <1 $/Wp. Close-Spaced Sublimation (CSS) is the fastest and simplest deposition process for both semiconductors used, CdTe and CdS, permitting in-line production at high linear speed of about 1 m/min.. The individual manufacturing steps for integrated modules are explained in view of their incorporation in the production line. ANTEC Solar GmbH has entered production of CdTe thin film modules on a scale of 100,000 m2 per annum using CSS as the deposition procedure for the semiconductor films and high-rate in-line sputtering for transparent and opaque contacts. Standard module size is 60 × 120 cm2. The production line is operative since 2002, without major problems. This article recounts the efforts to master lab processes for application in production.
CuGaSe2-Based Solar Cells with High Open Circuit Voltage
Authors: Caballero Raquel , Siebentritt Susanne , Kaufmann Christian A. , Kelch Carola , Schweigert Daniel , Unold Thomas , Rusu Marin , Schock Hans-Werner , Lux-Steiner Martha Ch 
Published: April 2011

AbstractThe objective of this work is to increase the open circuit voltage of CuGaSe2(CGS)-based solar cells without decreasing their efficiency. For that, the interface between the p-type CGS absorber and the n-type CdS/ZnO window layer is compared using three different recipes for the growth of the buffer layer. Results show the importance of the adaptation of the CdS buffer layer to the CuGaSe2 absorber film. A maximum open circuit voltage of 922 mV is achieved for the devices when using 60ºC as the chemical bath temperature and a low thiourea concentration. Drive-level capacitance profiling, external quantum efficiency and temperature dependent current-voltage measurements reveal a better quality of the CdS/CuGaSe2 interface for this buffer layer deposition conditions. Factors such as the larger depletion region width and the lower doping level, reducing the tunnelling component, are pointed out as responsible of the higher Voc.
Nanoscale Forces at the Heart of Staphylococcus Infections
Authors: Yongsunthon Ruchirej , Vellano Francis Paul , Lower Brian H. , Fowler Vance G. , Alexander Emily , Lower Steven K. 
Published: April 2011

AbstractStaphylococcus aureusis one of the most frequently isolated bacteria from infected medical implants.S. aureushas the capacity to adhere to the surface of an implant where it forms a biofilm. We used atomic force microscopy to probe binding forces between a fibronectin-coated tip and isolates ofS. aureus, which were obtained from either patients with infected prostheses or healthy humans. A unique force-signature was observed for binding events between the tip and the cells. There is a strong distinction (p=0.01) in the binding force-signature observed forS. aureusisolated from the infected vs. healthy populations. This observation suggests a fundamental correlation between nanometer scale binding forces and the clinical outcome of patients with implanted medical devices.
Capillary Forces Studied with Atomic Force Microscopy
Authors: Maghsoudy-Louyeh Sahar , Tittmann Bernhard R. 
Published: April 2011

AbstractThe deposition of films and coatings is sometimes influenced by the presence of small amounts of moisture, which can affect the nucleation and growth processes. It is important to understand the behavior of coating materials–especially in semiconductors–in terms of hydrophilicity/hydrophobicity along with adhesion forces. Our technical approach centers on the use of the atomic force microscope (AFM) which was found to be a reliable tool for studying the surface characteristics of materials. In addition to obtaining topographic information, the AFM can also probe attractive or repulsive forces between the tip and the sample surfaces. In this research, a systematic study of the influence of humidity on the adhesion forces between different AFM tips (silicon and silicon nitride) and both hydrophilic and hydrophobic materials (quartz, calcite, mica, graphite) has been conducted using atomic force microscopy. Several force-distance curves measured by the M5 AFM have been gathered at a series of different humidity levels and different locations on the samples. In this paper, measurements of the adhesion force for hydrophobic and hydrophilic materials versus humidity are presented. The results show that the adhesion force on graphite which has hydrophobic character is independent of humidity variation. Results also show that the adhesion force for fused quartz, mica, and calcite which are hydrophilic materials, change dramatically with increasing humidity due to capillary forces. This is in good agreement with theoretical calculations.
Growth and Raman Spectroscopy of Single Crystal ZnGeN2 Rods Grown from a Molten Zn/Ge Alloy
Authors: Peshek Timothy J. , Wang Shanling , Angus John C. , Kash Kathleen 
Published: April 2011

AbstractWe present evidence for the growth of ZnGeN2 from a molten Zn/Ge alloy via the vapor-liquid-solid mechanism. Hexagonally faceted, 3-4 microns wide by 20-40 microns long, single crystal rods of ZnGeN2 capped by a polycrystalline dome of ZnGeN2 were formed. A micro-Raman spectrum shows several individually resolved peaks and no spectral features above 825 cm−1, in contrast to a previously published spectrum for polycrystalline ZnGeN2, but in excellent agreement with recent theoretical predictions.
Obsidian Subsources Utilized at Sites in Southern Sardinia (Italy)
Authors: Tykot Robert H , Glascock Michael D. , Speakman Robert J. , Atzeni Enrico 
Published: April 2011

AbstractWhile geochemical analysis of obsidian artifacts is now widely applied around the world, both new instrumental methods and new research questions continue to be applied in archaeology. In the Mediterranean, many analytical methods have been employed and proven successful in distinguishing all of the island sources. In this study, results are presented from the virtually non-destructive, LA-ICP-MS multi-element analysis of 95 carefully selected obsidian artifacts from four neolithic period sites in southwestern Sardinia. The patterns of exploitation of specific Monte Arci obsidian subsources revealed in this study support a down-the-line model of obsidian trade during the neolithic period, but with chronological changes that are best explained by increased socioeconomic complexity.
Anomalous Branch-structured Carbon Nanotubes on Silicon Substrates
Authors: Abdi Yaser , Mohajerzadeh Shams , Baghbani Kokab , Paydavosi Sara , Soleimani Ebrahim Asl 
Published: April 2011

ABSTRACTWe have grown vertically-aligned carbon nanotubes on (100) silicon substrates by means of a plasma enhanced chemical vapor deposition method. The growth of CNTs is achieved by a mixture of hydrogen and acetylene gases in a CVD reactor and a 2-5nm thick nickel is used as the seed for the growth. Following the growth of nanotubes on the silicon substrates, they are covered by a titanium-oxide layer and then the substrate is placed back into the original chamber to expose to a hydrogen plasma. Depending on the hydrogenation step, the nickel seed layer, which is placed on the tip side of the original nanotube, is expanded. The subsequent process in the same reactor leads to the growth of carbon nanotubes in a branched manner. Scanning electron microscopy has been used to investigate the results of such tree-like nanostructures.
Resonant and Broadband Microwave Permittivity Measurements of Single-walled Carbon Nanotubes
Authors: Darne Chinmay D. , Xie Lei-Ming , Padmaraj Divya , Cherukuri Paul , Zagozdzon-Wosik Wanda , Wosik Jarek 
Published: April 2011

ABSTRACTWe report on microwave measurements of complex permittivity of single-walled carbon nanotubes (SWNTs). The SWNT samples are a mixture of semiconducting and metallic nanotubes suspended using Pluronic (F108) as a stabilizing surfactant agent. Other samples that were characterized include pluronic powder and an oriented carpet of multi-walled nanotubes (MWNT). For broadband measurements, the shielded open-circuited transmission line technique was used. Single frequency (resonant) measurements for liquid-based SWNT samples were carried out by employing two different modes in specially designed microwave dielectric resonators (DR), either with a cylindrical hole in the center of a dielectric disk or with a horizontal gap (split resonator). The first resonator can operate in either TE011 or TM011 modes (3.4 GHz and 6 GHz) and was designed for liquid or powder characterization. For pluronic suspended SWNT, real (epsilon) and imaginary parts of permittivity were found at 3.4 GHz as 3.5 and 0.72, respectively.
Direct Growth of III-V Devices on Silicon
Authors: Herrick Katherine , Kazior Thomas , Liu Amy , Loubychev Dmitri I. , Fastenau Joel M. , Urteaga Miguel , Fitzgerald Eugene A. , Bulsara Mayank T. , Clark David , Brar Berinder , Ha Wonill , Bergman Joshua , Daval Nicolas , LaRoche Jeffrey 
Published: April 2011

ABSTRACTOur direct growth approach of integrating compound semiconductors (CS) and silicon CMOS is based on a unique silicon template wafer with an embedded CS template layer of Germanium (Ge). It enables selective placement of CS devices in arbitrary locations on a Silicon CMOS wafer for simple, high yield, monolithic integration and optimal circuit performance. HBTs demonstrate a peak current gain cutoff frequency ft of 170GHz at a nominal collector current density of 2mA/μm2. To the best of our knowledge this represents the first demonstration of an InP-based HBT fabricated on a silicon wafer.
Growth optimization for high quality GaN films grown by metal-organic chemical vapor deposition
Authors: Jang Jung Hun , Herrero A M , Son Seungyoung , Gila B , Abernathy C , Craciun V 
Published: April 2011

ABSTRACTGaN layers were grown on c-plane sapphire substrates by using a conventional two step growth method via metal organic chemical vapor deposition (MOCVD). The effect of different growth conditions used in the deposition of the low temperature nucleation layer and high temperature islands on the crystalline quality of the GaN layers was investigated by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). The polar (tilt) and azimuthal (twist) spread were estimated from the full width at half maximum (FWHM) values of the omega rocking curves (¥ø-RCs) recorded from the planes parallel and perpendicular to the sample surface. It was found from the XRD and TEM study that the edge and mixed type threading dislocations are dominant defects so that the relevant figure of merit (FOM) for the crystalline quality should be considered only by the FWHM value of ¥ø-RC of the surface perpendicular plane. The result showed that the mixed- and edge-types dislocations were strongly associated with the growth conditions used in the deposition of the nucleation layer and high temperature islands.
Power Performance of AlGaN/GaN HEMT's Grown on 6″ Si Substrates
Authors: Derluyn Joff , Das Jo , Cheng Kai , Lorenz Anne , Visalli Domenica , Degroote Stefan , Germain Marianne , Borghs Staf 
Published: April 2011

ABSTRACTAlGaN/GaN HEMT's were grown on 6″ Si <111> substrates and passivated using IMEC's in-situ SiN technique. The epitaxial growth was optimized to minimize RF losses due to the substrate-nitride interface while at the same time maintaining high buffer resistivity and low trap density.To assess RF losses of the epitaxial layer structure, coplanar waveguides were defined on places of the wafer where the top in-situ SiN and AlGaN has been etched away. The attenuation of the RF signals on the coplanar waveguides remained below 0.3dB/mm for frequencies up to 6GHz.The processing of HEMT's included mesa etching, the formation of TiAlMoAu ohmic contacts, 500nm long gates with source-connected field plates and an airbridge process. The gate fingers are 250µm wide, yielding a total gate periphery of 1.5mm for 6-finger devices and 5mm for the 20-finger version.The devices' RF power performance was characterised on-wafer. To avoid damage to the RF-probes, active load-pull measurements were performed in pulsed mode with a 100µs period under 10% and 30% duty cycle respectively. As there was no difference between the performance using different duty cycles, we conclude that the channel temperature reaches steady-state in less than 10µs.The 6-finger devices were operated in deep class AB operation mode but showed clear self-biasing effects. The bias voltage was changed from 30V to 60V in 10V increments. Under 60V bias, the devices provide an output power density of 7.9W/mm at 2GHZ with a PAE of 46% and 6.3W/mm at 4GHz with a PAE of 41%. The output power scales linearly with the bias voltage ranging from 30V to 60V, showing that there is no drain lag in the devices. We attribute this to the efficient surface passivation with the in-situ Si3N4 as well as to high crystal quality and hence the low trap density of the buffer layers. At 2GHz, the linear and saturated power gain are 22dB and 16.4dB respectively. An interesting observation is that the maximum gate current, even at power density levels of 7.9W/mm, remains below 50µA/mm which should prove beneficial for reliability.The larger 20-finger devices of 5mm total gate periphery reach a maximum absolute output power of 20W at a bias of 40V which represents the limit of our on-wafer measurement system.These results prove that the use of large area Si substrates is the only viable route forward for AlGaN/GaN HEMT's.
MOVPE of m-plane InGaN/GaN Buffer and LED Structures on γ-LiAlO2
Authors: Behmenburg H. , Mauder C. , Khoshroo L. Rahimzadeh , Wen T.C. , Dikme Y. , Rzheutskii M.V. , Lutsenko E.V. , Yablonskii G.P. , Chou M.M.C. , Woitok J. , Heuken M. , Kalisch H , Jansen R.H. 
Published: April 2011

ABSTRACTWe report on deposition and properties of m-plane GaN/InGaN/AlInN structures on LiAlO2 substrates grown by metal organic vapor phase epitaxy (MOVPE). At first, two different buffer structures, one of them including an m-plane AlInN interlayer, were investigated concerning their suitability for the subsequent coalesced single-phase m-plane GaN growth. A series of quantum well structures with different well thickness based on one of these buffers showed absence of polarization-induced electric fields verified by room temperature photoluminescence (RT PL) measurements at different excitation intensities. Furthermore, polarization-resolved PL measurements revealed a high degree of polarization (DoP) of the emitted light with an intensity ratio of 8:1 between light polarized perpendicular and parallel to the c-axis.
AlGaN/GaN multiple quantum wells grown by using atomic layer deposition technique
Authors: Lo Ming-Hua , Li Zhen-Yu , Chen Shih-Wei , Hong Jhih-Cang , Lu Ting-Chang , Kuo Hao-Chung , Wang Shing-Chung 
Published: April 2011

ABSTRACTIn this work, we report on the growth of ultraviolet (UV) AlGaN/GaN multiple quantum wells (MQWs) structure using atomic layer deposition (ALD) technique. The AlGaN/GaN MQW sample grown on the sapphire substrate consisted of three GaN QWs and four AlGaN barriers comprised AlN/GaN superlattices (SLs). The root-mean-square value of the surface morphology was only 0.35 nm observed from the atomic force microscope image and no crack was found on the surface. Both of the high resolution X-ray diffraction curves and transmission electron microscope images showed sharp interfaces between SLs layers and QWs with good periodicity. These results demonstrate that the ALD could be a very useful technique for controlling the crystalline quality and thickness of the III-nitride epilayer.
P Implantation Effect on Specific Contact Resistance in 3C-SiC Grown on Si
Authors: Bazin Anne-Elisabeth , Michaud Jean-François , Portail Marc , Chassagne Thierry , Zielinski Marcin , Lecoq Jean-Marc , Collard Emmanuel , Alquier Daniel 
Published: April 2011

ABSTRACTIn this work, non-intentionally doped 3C-SiC epilayers were implanted using phosphorus at different energies and subsequently annealed at temperatures between 1100°C and 1350°C in order to form n+implanted layers. Different techniques such as Fourier Transformed InfraRed spectroscopy (FTIR) and Secondary Ion Mass Spectroscopy (SIMS) were used to characterize implanted 3C-SiC epilayers after the different annealing steps. Successively, metal layers were sputtered in order to form the contacts. The specific contact resistance (ñC) was determined by using circular Transfer Length Method (c-TLM) patterns. Specific contact resistance values were investigated as a function of doping and contact annealing conditions and compared to those obtained for highly doped 3C-SiC epilayers. As expected, ñC value is highly sensitive to post-implantation annealing and metal contact annealing. This work demonstrates that low resistance values can be achieved using phosphorus implantation and, hence, enabling device processing.
Using Thermal Oxidation and Rapid Thermal Annealing on Polycrystalline-SiGe for Ge Nanocrystals
Authors: Kao Chyuan-Haur , Lai C. S. , Tsai M. C. , Lee C. H. , Huang C. S. , Chen C. R. 
Published: April 2011

AbstractIn this paper, simple techniques were proposed to fabricate germanium nanocrystal capacitors by one-step thermal oxidation and/or rapid thermal annealing on polycrystalline-SiGe (poly-SiGe) deposited with a LPCVD (low pressure chemical vapor deposition) system. This thermal oxidation method can directly result in the top-control oxide layer via the oxidation of amorphous-Si film and the formation of Ge nanocrystals from the poly-SiGe film. Otherwise, the rapid thermal annealing method can be also used to form Ge nanocrystals as comparison.