bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct-Write Deposition and Laser Processing of Dry Fine powders
Authors: Kumar Pranav , Das Suman 
Published: June 2019

ABSTRACTWe present a concept for multi-material solid freeform fabrication of 2D and layered 3D heterogeneous components. This technique involves direct-write deposition of multiple, patterned powder materials followed by laser processing. The direct-write deposition system features miniature hopper-nozzles for depositing dry powdered materials by gravity or by high frequency vibration-assisted flow onto a movable substrate. A dual wavelength laser processing workstation was used to consolidate the deposited pattern to desired densities. The feasibility of this concept was proved by direct-writing and laser processing various powder material patterns.
Controlled Electrospray for Tissue Engineering Applications
Authors: Paine M.D. , Stark J.P.W 
Published: June 2019

AbstractThe development and status of a novel electrospray system, capable of a variety of applications, including the fabrication of tissue engineered structures is described. The system requirements dictate the following key components: a micro-fabricated silicon electrospray emitter, a mass spectrometer capable of selecting molecules having a charge to mass ratio up to 32, 000 with a resolution of 10, 000, and an integrated ion optics system permitting depositing the selected molecules ‘softly’ onto a target with a spatial resolution of 0.1μm. One critical feature of the system is the overall efficiency of transferring biomolecules from a buffer solution, typically comprising water, acetonitrile and ammonium acetate, into an ion flux. Commercial ES/MS systems are generally designed with simplicity of operation as a design driver, together with the low probability of transmitting spray droplets directly into the quadrupole mass selection system. This has focused attention onto the detailed design and characterization of the electrospray emitter and the environment into which the spray is launched. This has highlighted the need to evaluate in detail, an electrospray operating into a low pressure environment and to improve our understanding of the interaction between voltage and flow rate in the transition from nano-electrospray mode, wherein no positive pressure is applied to the fluid and normal electrospray mode, close to minimum flow rate. Early results of this investigation are presented. There is evidence that at reduced ambient pressure there is a small reduction in spray current, however this is offset by improved transmission of the beam into the first quadrupole stage.
Production of complex nano-structures by electro-hydro-dynamics
Authors: Loscertales Ignacio G. , Barrero A. , Márquez Manuel 
Published: June 2019

ABSTRACTThe use of electro-hydro-dynamic (EHD) forces to generate highly charged coaxial jets of immiscible fluids, with diameters in the micro and nano regime, has unravel itself as a very interesting choice for producing complex nanostructures from a vast variety of precursors, provided they can solidify, polymerize or gel, in times comparable or shorter than the living time of the coaxial nanojet. For time ratios larger than one, the result of the process are micro or nanocapsules, while for time ratios smaller than one coaxial nanofibers are produced. We show examples of both situations, with organic and inorganic precursors. On the other hand, realization of the process in a liquid bath opens the door to production of controlled micro and nanosized complex emulsions.
Grown-in and Radiation-induced Defects in 4H-SiC
Authors: Eberlein T. A. G. , Jones R. , Briddon P. R. , Öberg S. 
Published: June 2019

AbstractSiC is a material that seems ideal for high-power, high frequency and high temperature electronic devices. It does not suffer from large reverse recovery inefficiencies typical for silicon when switching. In contrast to silicon, SiC is however difficult to dope by diffusion, and instead ion-implantation is used to achieve selective area doping. The drawback of this technique is that irradiating the crystal with dopant atoms creates a great deal of lattice damage including vacancies, interstitials, antisites and impurity-radiation defect complexes. Although many of the point defects can be eliminated through thermal annealing, some however, e.g. the photoluminescence (PL) DI and DLTS Z1/Z2 centers in ·4H-SiC, are stable to high temperatures. In this polytype, DI and the related alphabet lines are the most prominent PL signals. The latter can be seen directly after low energy irradiation while DI usually dominates the PL spectrum of implanted and irradiated SiC after annealing. Not only implantation but also rapid growth of SiC by CVD methods leads to a deterioration in quality with an increase in electrically active grown in defects. Among these, the Z1/Z2 defects are dominant in n-type 4H-SiC, as well as material that has been exposed to radiation. We use first principles density functional calculations to investigate defect models for the above mentioned defects in 4H-SiC and relate their electrical and optical activity to experiments.
Void Formation in Hydrogen Implanted and Subsequently Plasma Hydrogenated and Annealed Czochralski Silicon
Authors: Job R. , Düngen W. , Ma Y. , Huang Y. L. , Horstmann J. T. 
Published: June 2019

AbstractBy μ-Raman spectroscopy the formation of hydrogen related defects (vacancy-hydrogencomplexes, hydrogen saturated silicon dangling bonds, H2 molecules in multi-vacancies andvoids/platelets) has been investigated in H-implanted and subsequently H-plasma exposed andannealed Czochralski (Cz) silicon wafers. Annealing was done either in air or in an ambientcontaining hydrogen (forming gas). The investigations were applied under conditions, which arerelevant for ion-cut processes and layer exfoliation in Cz Si for SOI-wafer fabrication at reducedimplantation doses (as compared to standard procedures like the smart-cut® process).
Modelling the MOS Device Conductance Using an Extended Tunnelling Model and Subsequent Determination of Interface Traps.
Authors: Konofaos N. 
Published: June 2019

AbstractThe contribution of the AC conductance on admittance spectroscopy measurements on Metal-Insulator-Semiconductor (MIS) devices allows the calculation of the interface traps density and the relevant time constant. Two equivalent model approaches can be applied in order to explain the experimental results. One model is the statistical model based on the Shockley- Read-Hall (S-R-H) recombination statistics and the other one is a model based on the quantum tunneling effect. Recent evidence suggest that the tunneling model can be equivalent to the statistical one if a continuum of states is also considered in the modeling, creating an extended tunneling model. In the present paper, a further investigation on the extended model is attempted. Admittance spectroscopy data were collected for various Insulator/Si combinations, such as SrTiO3 and BaTiO3 deposited on Si. Both the S-R-H based and the extended tunneling models were used to analyze the data. The results showed that the extended tunneling can model the conductance of the device successfully and can calculate the interface states density and the traps time constant.
Electrical Transient Based Defect Spectroscopy in Polymeric and Organic Semiconductors
Authors: Mohapatra Y.N. , Varshney V. , Rao V. , Singh Samarendra P. , Samal G.S. 
Published: June 2019

AbstractThe relation between electrically active defects in organic and polymeric semiconductor materials and degradation of devices such as loss of luminance is currently not understood. In this paper, we study defect related charge processes using electrical transients in polymeric and organic diodes. We monitor slow charging and discharging currents as a function of time for both virgin and electrically aged devices. The current transients are analyzed spectroscopically in time domain using a technique called Time Analyzed Transient Spectroscopy, which is similar to DLTS in its implementation. We observe highly stretched exponentials over 3—4 orders of magnitude in time up to thousands of seconds indicating existence of large distribution in time constants in aged PLED devices. We demonstrate ability to distinguish between different mechanisms of charge storage related to defect related processes in typical OLED and PLED.
Towards the Routine Fabrication of P in Si Nanostructures: Understanding P Precursor Molecules on Si(001)
Authors: Schofield Steven R. , Curson Neil J. , Warschkow Oliver , Marks Nigel A. , Wilson Hugh F. , Simmons Michelle Y. , Smith Phillip V. , Radny Marian W. , McKenzie David R. 
Published: June 2019

AbstractThe ability to controllably position individual phosphorus dopant atoms in silicon sur-faces is a critical first step in creating nanoscale electronic devices in silicon, for example a phosphorus in silicon quantum computer. While individual P atom placement in Si(001) has been achieved, the ability to routinely position P atoms in Si for large-scale device fabrication requires a more detailed understanding of the physical and chemical processes leading to P atom incorporation. Here we present an atomic-resolution scanning tunneling microscopy study of the interaction of the P precursor molecule phosphine (PH3) with the Si(001) surface. In particular, we present the direct observation of PH3 dissociation and diffusion on Si(001) at room temperature and show that this dissociation is occasionally complete, leaving a P monomer bound to the surface. Such surface bound P monomers are important because they are the most likely entry point for P atoms to incorporate into the substrate surface at elevated temperature.
Influence of Oxygen Vacancies and Strain on Electronic Reliability of SiO2-x Films
Authors: Suzuki Ken , Ito Yuta , Miura Hideo , Shoji Tetsuo 
Published: June 2019

AbstractWe performed a quantum chemical molecular dynamics analysis for SiO2-x structure under strain to make clear the effect of the strain and intrinsic defects on both electronic and structural characteristics of SiO2-x. The SiO2-x showed a large change of the structure during the simulation. This is mainly because that the Si-O bonds near an oxygen vacancy were broken and a free silicon monoxide molecule was generated in the SiO2-x structure. The magnitude of the band gap of the SiO2-x decreased drastically due to the formation of the free monoxide. In addition, the band gap decreased further under large tensile strain of about 10%. We can conclude therefore, that both the existence of oxygen vacancies and tensile strain in SiO2-x films deteriorate the electronic reliability of the oxide film seriously.
μ-Raman Spectra Analysis of the Evolution of Hydrogen Related Defects and Void Formation in the Silicon Ion-Cut Process
Authors: Düngen W. , Job R. , Ma Y. , Huang Y. L. , Fahrner W. R. , Keller L. O. , Horstmann J. T. 
Published: June 2019

AbstractHydrogen implanted, boron doped (100) Czochralski silicon wafers, which were annealed after implantation up to 600 °C, are investigated by μ-Raman spectroscopy (μRS). We have studied the thermal evolution of hydrogen related defects, including vacancy-hydrogen (VnHm) complexes, H-saturated dangling bonds and trapped H2 molecules. Applying temperatures above ∼ 400 °C, the hydrogen related defects and the formation of voids/platelets are distinctly modified. The measured intensity of the local vibration mode (LVM) of H2 molecules trapped in multi-vacancy complexes at a frequency of ∼ 3820 cm-1 decreases while the LVM of H2 in platelets or larger voids (∼ 4150 cm-1) is increasing. This indicates that multi-vacancy complexes coalesce and form larger voids/platelets. Most of the VnHm complexes (∼ 2000 – 2200 cm-1) are dissolved during annealing at 600 °C, where a thin silicon layer exfoliates due to the ion-cut mechanism. However, the Raman modes of the characteristic V2H6 complex, of Si-Hx bonds stemming from H-terminated surfaces and of H2 located in voids/platelets still can be observed after a short time annealing (≤2 min) at 600 °C.
Hydrogen Ion Implantation Caused Defect Structures in Heavily Doped Silicon Substrates
Authors: Li Minhua , Wang Q. 
Published: June 2019

AbstractThe defects caused by hydrogen ion (H+) implantation were studied for heavily arsenic (As), boron (B), and phosphorous (P) doped (100) silicon substrates. At the implantation energy of 170keV, H+ beam generates defect zones in both arsenic and boron doped silicon wafers. The width of implant damage zone in the heavily As-doped silicon increased from 138nm to 415nm when H+ ion implant dose increased from1×1016 ion//cm2 to 5×1016 ion/cm2, respectively. This dependence is however, opposite in the heavily B-doped substrate. The defect zone decreased with increasing H+ ion dose. The second ion mass spectrometry (SIMS) data show that in both heavily As- and P-doped silicon substrates, hydrogen distribution was governed by both H+-dopant pairing reaction and the amount of the crystal damage, whereas it is exclusively determined by pairing reaction in heavily B-doped silicon substrates. The atomic force microscope (AFM) measurement indicated that the rms roughness of the as-exfoliated surface was 18.86nm, 13.06nm, and 6.79nm for P-, As- and B-doped silicon substrates, respectively. An rms roughness improvement of 20nm-170nm was observed when wafers were annealed at 270°C.
Effect of Substrate Orientation on the Growth Rate and Surface Morphology on GaSb Grown by Metal-Organic Vapor Phase Epitaxy
Authors: Yu Jian , Bhat Ishwara B. 
Published: June 2019

AbstractMOVPE of GaSb grown on (100), (111)A and (111)B GaSb substrates were investigated to study the effect of substrate orientation on the growth rate and surface morphology. Besides growth temperature and V/III ratio, the GaSb growth rate strongly depends on the crystallographic orientation. As the V/III ratio rises, the growth rate on the (111)B oriented substrate decreases, whereas that on the (111)A oriented substrate increases. The surface morphology on different substrates was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). On (111)A substrates, triangular hillocks are the dominant defects, while on (111)B planes, three distinct types of hexagonal hillocks are observed, namely, non-flat top hexagonal structure with spiral growth features (Type I), flat top structure with lateral growth features (Type II), and non-flat top hexagonal structure with multiple islands (Type III). For all types, the basal edges of each hillock are preferentially aligned along <110> directions. A closer look reveals that the top surface of Type II feature consists of many levels of small hexagonal shaped terraces, with each step height in the monolayer range, indicating a step flow growth involved.
Thermal Transformation of Hydrogen Bonds in a-SiC:H Films: Structural and Optical Properties
Authors: Vasin Andrey V. , Kolesnik Sergey P. , Konchits Andrey A. , Lysenko Vladimir S. , Nazarov Alexey N. , Rusavsky Andrey V. , Ashok S. 
Published: June 2019

AbstractHydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited using magnetron sputtering technique. Investigation of the effect of the vacuum annealing temperature on photoluminescence properties and paramagnetic defects, and its correlation with structural transformation of a-SiC:H have been performed. Significantly enhanced light emission efficiency after low-temperature vacuum treatment (450 °C) is found due to enhanced passivation of paramagnetic defects associated with carbon-rich chemically disordered structure. Subsequent high-temperature vacuum annealing results in a decrease of luminescent intensity that is associated with increase of carbon related paramagnetic defect states, shown to be the primary nonradiative recombination centres. For the first time silicon-related dangling bonds in a-SiC:H have been detected reliably by electron paramagnetic resonance measurements in annealed samples.
Probing Process-Induced Defects in Si Using Infrared Photoelastic Stress Measurement Technique
Authors: Liu X.H. , Wong S.P. , Peng H.J. , Ke N. , Zhao Shounan 
Published: June 2019

AbstractThe stress depth distribution in the silicon substrate under thin thermal oxide layers has been measured using the photoelastic technique. With the high sensitivity and improved spatial resolution of a newly developed low level birefringence detection system, it is confirmed that the stress distribution deviates significantly from the linear distribution predicted by classical bi-metallic strip theory. The deviation can be attributed to arising from Si self-interstitial injection during the thermal oxidation process. Long term changes in the stress distribution with time have also been observed and the changes can be understood in terms of point defect movements under the stress field in the substrate. Our preliminary results have demonstrated how we can probe microscopic point defect processes in thin film SiO2/Si substrate systems using a macroscopic photoelastic stress measurement technique.
Defect Reduction in Si-based Metal-Semiconductor-Metal Photodetectors with Cryogenic Processed Schottky Contacts
Authors: Li M. , Anderson W. A. 
Published: June 2019

AbstractMetal-Semiconductor-Metal photodetectors (MSM-PD's) and simple Schottky diodes were fabricated using a low temperature (LT) technique to greatly reduce the device dark current. LT processing for metal deposition increased Schottky barrier height by improving the interface between metal and semiconductor to reduce the leakage current of the device. The structure consists of a 20 Å oxide over the active area to passivate surface states, a thicker oxide under contact pads to reduce dark current and the interdigitated Schottky contacts. A comparison was made for Schottky metal deposited with the substrate at 25 °C or -50 °C (LT). The devices fabricated using the LT process had better I-V characteristics compared to detectors fabricated using the standard room temperature (RT) metal deposition technique. The dark current for the LT film was found to be one to three orders lower in magnitude compared to the film deposited at RT. In one case, for example, the dark current was significantly reduced from 1.69 nA to 4.58 pA at 1.0 V. The active area for the device was determined to be 36 × 50 μm2 with 4 μm electrode width and 4 μm electrode spacing. Additionally, LT-MSM-PD's exhibited an excellent linear relationship between the photo-current and the incident light power. The Schottky barrier height for LT processing was found to be 0.79 eV; however, this value was 0.1 eV more than that of the same contact obtained by RT processing.
Nanoindentation as a Tool for Formation of Thin Film-Based Barrier Structures
Authors: Khlyap H. , Sydorchuk P. 
Published: June 2019

AbstractA2B6 semiconductors and their solid solutions (ZnSe, ZnTe, CdTe, ZnCdHgTe) are matter of choice for near- and far-infrared optoelectronics. The importance of maximally reduced degree of defectness for these materials is not subjected to discussion. However, preparation of high quality barrier structures based on these compounds by means of MBE, laser technology or liquid phase technique is not always successful due to lattice parameters mismatch. At the same time, good selection of a proper buffer layer may also pose some unavoidable problems. From this point of view the nanoindentation as a tool of defect engineering can be effective for fabrication of surface barrier structures. The first experimental results and numerical simulation of experimental data obtained under investigation of nanoindentation effect on electric characteristics (in particular, current – voltage (I-V) and capacitance – voltage (C-V)) of ZnCdHgTe thin films and ZnCdHgTe/Cd(Zn)Te heterostructures at the room temperature are presented.
High-Rate Deposition Of Rare-Earth Doped Silicate Nanoparticles For Porous & Dense Optical Films
Authors: Horne Craig R. , Mascarel Pierre de , Blume Russell , Jur Jesse , Cohen-Jonathan Cecile , Chapin Michael , Posner Jonathan , Foo Wei Cho , Honeker Christian , Zhu Qing , Chiruvolu Shiv , Mosso Ronald , McGovern William 
Published: June 2019

AbstractA novel deposition process has been developed for manufacturing of high quality rare-earth doped glass films with complex composition. This process, Laser Reactive Deposition (LRDTM), comprises photothermal laser pyrolysis using an aerosol feedstock coupled with deposition of the resulting nanoparticle product onto Si substrates with our without an underlying glass film. This paper describes this novel process as well as the structure, properties and performance of the Erdoped, multicomponent silicate glass films produced to date with this process.
Visible and Infrared Emission from Er-doped III-N Light Emitting Diodes
Authors: Zavada John M. , Nyein Ei Ei , Hömmerich Uwe , Li J. , Lin J. Y. , Jiang H. X. , Chow P. , Dong Jian-Wei 
Published: June 2019

AbstractWe report on the visible and infrared emission characteristics of Er-doped III-N lightemitting diodes (LEDs). Quantum well-like device structures were grown through a combination of metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) on cplane sapphire substrates. The dual stage growth process was used to take advantage of the high quality of AlGaN layers produced by MOCVD and in situ doping of Er during MBE growth. The multilayer structures were processed into devices and LEDs with different sizes and geometric shapes were produced. Electroluminescence (EL) was observed under either forward or reverse bias conditions. Visible and infrared spectra displayed narrow emission lines representative of the Er3+ system. The temperature dependence of the spectra, which were measured from 100K to 300K, showed a stability in the visible emission intensity but a sharp decrease in the infrared intensity at room temperature. Based on light output vs current measurements, estimates of the excitation cross-section were obtained for visible EL emission.
Nonequilibrium Carrier Dynamics Studied in Er, O-Codoped GaAs by Pump-Probe Reflection Technique
Authors: Fujiwara Yasufumi , Nakamura Kazuhiko , Takemoto Shoichi , Terai Yoshikazu , Suzuki Masato , Koizumi Atsushi , Takeda Yoshikazu , Tonouchi Masayoshi 
Published: June 2019

AbstractCarrier dynamics in Er,O-codoped GaAs (GaAs:Er,O) have been systematically investigated by means of a pump and probe reflection technique with a mode-locked Ti:sapphire laser. In GaAs:Er,O, it has been found that the codoping produces a single atom configuration (Er-20 configuration) as an Er atom located at the Ga sublattice with two adjacent O atoms together with two As atoms, resulting in extremely strong Er luminescence. Time-resolved reflectivity of GaAs:Er,O exhibited an abrupt increase in amplitude, followed by a steep decrease to negative in less than 1 ps and then a gradual increase in approximately 100 ps. The steep decrease is due to bandgap renormalization. The gradual increase in reflectivity depended strongly on Er concentration, indicating that a trap induced by Er and O codoping plays an important role in dynamics of nonequilibrium carriers in GaAs:Er,O.