bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Substrate Type on CoSi2 Formation in Rapid Thermal Annealing
Authors: Kim Eun Jung , Lee Jin Yul , Kim Sang Deok , Song Han Sang , Yeom Seung Jin , Ishigaki Toshikazu , Kang Kitaek , Yoo Woo Sik 
Published: February 2020

Low resistivity junctions and contacts are essential for fabricating high performance devices with advanced device nodes. Significant effort has been expended towards the development of low resistivity junctions. However, low resistivity contact formation has not received significant attention. The silicide of choice has been changed from high temperature silicide to low temperature silicide (i.e., WSi → TiSi2 → CoSi2 → NiSi) depending on the allowed maximum process temperature and required minimum line width for the device node. Once the candidate silicide material is chosen for the device node, relatively small improvements in resistivity and small changes in the silicide formation process have been made in recent years, despite silicidation process optimization. This includes fine tuning of silicide formation conditions for types of Si (i.e., doped poly Si, NMOS and PMOS), modifications of process steps and integration schemes.
In this study, we have investigated the effect of substrate type on CoSi2 formation in rapid thermal annealing (RTA). The RTA temperature and time sensitivity of the resulting resistivity of the Co2Si contacts with P-doped poly-Si, NMOS source/drain (S/D) and PMOS S/D were investigated for process window determination using a single wafer furnace (hot wall)-based RTA system.
The type of Si had a significant effect on the resulting CoSi2 formation temperature and contact resistance was observed. With the increase of RTA time, the CoSi2 formation temperature was reduced and the difference of CoSi2 formation temperature for different Si substrates became larger. Depending on CoSi2 integration schemes (i.e., one step (for all CoSi2 in poly-Si gate and S/D) or two step (one for CoSi2 for poly-Si gate and the other for CoSi2 for S/D)), the CoSi2 formation RTA conditions must be modified. Detailed effects of substrate type on CoSi2 formation and process windows will be reported.

Figure 1
Hot-Wire Chemical Vapour Deposition for Silicon Nitride Waveguides
Authors: Domínguez Bucio Thalía , Tarazona Antulio , Khokhar Ali Z. , Mashanovich Goran Z. , Gardes Frederic Y. 
Published: February 2020

SiN layers are typically deposited by low-pressure chemical vapour deposition (LPCVD) and plasma-enhanced chemical vapour deposition (PECVD). The issue with these deposition techniques is that they require high temperature processing (>400ºC) in order to produce waveguides with low propagation losses. As a result, they are incompatible with multilayer platforms in which the integration of active devices is intended, because the fabrication of these devices requires processes that are sensitive to high temperatures such as metallisation and doping. To address this situation, we are proposing hot wire chemical vapour deposition (HWCVD) as a means to deposit SiN layers at temperatures below 400ºC. This technique has already been used in solar cell applications [1,2] to produce amorphous SiN layers with low hydrogen content and high mass density [3]. In this study, several deposition recipes were defined with a design of experiments methodology (DoE) in which different combinations of deposition parameters were investigated to understand how they affect the material structure of the SiN layers in order to optimise the quality and the losses of the deposited materials. The physical, chemical and optical properties of the obtained SiN layers were characterised using ellipsometry, scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and atomic force microscopy (AFM). Also, waveguide structures were fabricated on the deposited materials to measure their propagation losses at 1310 and 1550nm using the cutback method. SiN layers with good uniformity, roughness as low as 0.61nm, H concentration as low as 10.4x1021 atoms/ cm3 and losses of 7.1dB/cm at 1310nm and 12.3dB/cm at 1550nm were obtained.
[1] H. D. Goldbach, C. H. M. van der Werf, J. Löffler, A. Scarfo, A. M. C. Kylner, B. Stannowski, W. M. Arnoldbik, A. W. Weeber, H. Rieffe, W. J. Soppe, J. K. Rath, and R. E. I. Schropp,“Hot-wire chemical vapor deposition of silicon nitride for multicrystalline silicon solar cells,” in Conference Record of the Thirsy-first IEEE Photovoltaic Specialists Conference, pp. 1249–1252, IEEE, January 2005.
[2] J. K. Holt, D. G. Goodwin, A. M. Gabor, F. Jiang, M. Stavola, and H. A. Atwater, “Hot-wire chemical vapor deposition of high hydrogen content silicon nitride for solar cell passivation and anti-reflection coating applications,” Thin Solid Films 430, pp. 37–40, April 2003.
[3] V. Verlaan, R. Bakker, C. H. M. van der Werf, Z. S. Houweling, Y. Mai, J. K. Rath, and R. E. I. Schropp, “High-density silicon nitride deposited at low substrate temperature with high deposition rate using hot wire chemical vapour deposition,” Surface and Coating Technologies 201, pp. 9285–9288, September 2007.
(Invited) Basic Properties of h-BN Epilayers
Authors: Jiang Hongxing , Lin Jingyu 
Published: February 2020

III-nitride wide bandgap semiconductors have been at the center stage of the semiconductor R & D effort over the last two decades. Photonic/electronic devices based on III-nitrides, including UV/blue/green/white light emitting diodes (LEDs), violet/blue laser diodes (LDs), UV detectors, and high power/temperature transistors, have been successfully realized and commercialized.
Among the members of the III-nitrides, BN is the least studied and understood. BN exists in three crystalline forms (hexagonal, cubic and wurtzite). The sp2-bonded hexagonal form (h-BN) is the most stable phase when synthesized at any temperature under ambient pressure. Its extraordinary physical properties, such as ultra-high chemical stability, thermal conductivity, electrical resistivity, and band gap (Eg ~ 6.5 eV) make h-BN the material of choice for many emerging applications. Due to its close lattice match to graphite, h-BN is being recognized as the most suitable substrate/dielectric/separation layer for 2D electronics and optoelectronics. As such, much efforts in the synthesis of h-BN have been largely focused on mono- or a few layers of h-BN in the past.
In this presentation, I will summarize recent progress in the growth of wafer-scale h-BN epilayers with a few um in thickness by metal-organic chemical vapor deposition (MOCVD). The basic properties of h-BN epilayers will be discussed in comparison with other nitride semiconductors, in particular AlN. H-BN shows the unique qausi-2D nature with exceptionally high density of states (DOS) and large exciton binding energy (around 740 meV), which results in high optical absorption and emission intensity. P-type conduction in h-BN and diode behaviors in the p-n junction structures consisting of p-type h-BN and n-type Al-rich AlGaN heterostructures have been demonstrated, which could potentially address the intrinsic problem of low p-type conductivity in Al-rich AlGaN for DUV photonic devices. The potential applications of h-BN for deep UV emitters and detectors, 2D templates/dielectric/separation layers, and solid-state neutron detectors will also be discussed.
(Invited) The Use of Sub-Bandgap Optical Pumping to Identify Defects in AlGaN/GaN High Electron Mobility Transistors
Authors: Ren Fan 
Published: February 2020

AlGaN/GaN high electron mobility transistors (HEMTs) showed its promising features in high power and high frequency applications such as inverter units in hybrid electric vehicles, advanced radar systems, and satellite-based communication networks with its high density of sheet carrier concentration, high electron mobility, and radiation hardness. However, intrinsic defects and impurities in the channel and gate-to-drain regions degrades HEMT performance through phenomena such as drain current collapse, high gate leakage, and lower rf power efficiency. Moreover, subsequent electrical stressing of the HEMTs during operation leads to creation of more traps and further device degradation through various mechanisms, including gate contact sinking, shallow trap formations, and the inverse piezoelectric effect. It is clearly desirable to have non-destructive methods available that can identify the activation energies and spatial location of trap states in GaN-based heterostructure devices.
In this work, a sub-bandgap optical pumping technique using 671, 532 and 447 nm lasers was used to determine the trap locations in AlGaN/GaN HEMTs. Using different photon fluxes, the traps with different activation energies can be identified. This indicates that the defects originated at different physical locations in the HEMT heterostructures. The locations of the traps were confirmed by companion gate pulse measurements under optical pumping.
(Invited) Improved GaN Based Hydrogen Sensors
Authors: Baik Kwang Hyeon , Kim Jimin , Jang Soohwan 
Published: February 2020

Recently, there are many interests in hydrogen as alternative energy source and carrier. Hydrogen is emission-free fuel when reacted with oxygen to produce the heat of combustion of 141.9 kJ/g while 47.0 and 45.0 kJ/g are for gasoline and diesel. Electrochemical cells and combustion in internal engines are used to transport hydrogen-generated energy to power vehicles and electric devices. Great efforts have been devoted on the researches to produce hydrogen in efficient and economical ways such as photoelectrochemical water splitting, photocatalytic water splitting, radiolysis, and photobioligical water splitting.
Hydrogen is consumed in the petrochemical plant for hydrodealkylation, hydrodesulfurization, and hydrocracking, as a coolant in power stations due to its highest specific thermal conductivity of all gases, as an energy carrier in fuel-cell vehicles, in the propulsion of spacecraft, and in the semiconductor industry. Hydrogen gas is colorless, odorless, extremely reactive with oxygen, and has low ignition energy. When it leaks from pressurized container, its temperature rises up due to its negative Joule-Thomson coefficient, which can induce spontaneous flammable ignition. Therefore, hydrogen gas detection is very important issue in various hydrogen related industrial processes and equipments. Not only for early flammability alarm, a hydrogen sensor is also essential to monitor feed stream in the fuel-cell vehicle for efficient energy conversion.
GaN based material system is very suitable to construct hydrogen sensor. Wide bandgap of GaN enable devices to operate at high temperature and harsh radiative environment, and mechanical and chemical robustness of GaN ensures reliability and durability of the device. Many types of GaN based hydrogen sensing devices including Schottky diode, metal oxide semiconductor (MOS) diode, GaN nanowire and AlGaN/GaN high electron mobility transistors (HEMTs) which employ platinum or palladium film as a catalytic active layer have been developed for fast and sensitive detection of hydrogen .

In this study, effect of crystal polarity and plane on hydrogen sensing characteristics of GaN based diodes was investigated. Also, AlGaN/GaN HEMT hydrogen sensors with dramatically increased active sites on platinum nanostructure and GaN diode sensors with etched large surface area will be introduced as an approach to improve the sensitivity of hydrogen sensors.
Anchoring Molecules on the Surface of ZnO and Effects on Intergranular Transport Properties
Authors: Gamon Jacinthe , Barboux Philippe , Giaume Domitille , Le Mercier Thierry , Le Bahers Tangui 
Published: February 2020

Improving electrical conductivity in thin film semiconductor devices such as solar cells, thermoelectric modules, or transparent conducting devices, remains a key point for better performances. As polycrystalline films have the favor of the industry for their lower fabrication cost, the limitation of the current is most of the time attributed to charge scattering at the grain boundaries due to high energy barriers at the interface between grains.(1)
This work focuses on the understanding of intergranular electrical conductivity in the view of improving thin film semiconductor performances deposited via a soft chemistry deposition routes. In this goal, ZnO:Al was chosen as a model doped semiconductor for our investigations as it is a reference material in many semiconductor applications (sensors, solar cells, transparent conducting oxides)(2). Many studies have already demonstrated the role of adsorbed species onto ZnO thin films and nanostructures surfaces to improve sensor selectivity or charge transfer in dye sensitized solar cells for instance (3).
With this in mind, we have performed liquid phase adsorption studies of organic molecules onto ZnO particles through solution conductimetry and IR. A theoretical modeling of the energy level of anchoring molecules was performed in order to fit the LUMO level to the conduction band. Conjugated and thiophene based molecules with different substituents and lengths were selected. Conductivity on pressed powders was studied as a function of the applied pressure to show the effect of the grain boundaries and of the powder compaction. A conclusion was drown on the participation of these molecules and their LUMO levels in the electrical conductivity of ZnO:Al.
This study allows quantitative determination adsorbates on ZnO surface and puts into perspective the investigation of better matches between LUMO and conduction band.

Literature:

1. Greuter F, Blatter G. Electrical properties of grain boundaries in polycrystalline compound semiconductors. Semicond Sci Technol. 1990;5(2):111.
2. Klaus Ellmer, Andreas Klein, Bernd Rech. Transparent Conductive Zinc Oxide. Springer Series in Material Science. 2008.
3. Galoppini E. Linkers for anchoring sensitizers to semiconductor nanoparticles. Coord Chem Rev. 2004 juillet;248(13–14):1283–97.
TiO2 Nanoparticles Synthesis from a Ti Alloy Foil By Electrochemical Method in Aqueous Electrolyte
Authors: Ortega-Díaz David , Fernandez Dennys , Pelaez-Abellan Ernesto 
Published: February 2020

In recent years, catalysis and photocatalysis processes using TiO2 nanoparticles (TNPs) have received great attention due to their effectiveness in degrading and mineralizing organic and inorganic compounds. Nanocrystalline TiO2 powder with different crystallinity and phase structures were synthesized using a Ti alloy as anode and stainless steel as cathode by the galvanostatic anodization method in alcoholic solution of chloride. Sodium dodecyl sulphate (SDS) surfactant was used as additive for to control the particle size. The X-ray diffraction (XRD), RAMAN spectroscopy and transmission electron microscopy (TEM) results, showed that a 50:50 anatase and brookite mixture phase was obtained with crystal sizes 7.2 nm and 7.5 nm respectively without any annealing. The size of the particles and the material purity are measured using scanning electron microscopy (SEM), dynamic light scattering (DLS) and energy dispersive X-ray analysis (EDX) indicated that a particle size smaller than 40 nm and a free impurity materials. The Brunauer–Emmett–Teller (BET) results show a specific surface area bigger than 200 m2/g. The band gap energy of the resulting TNPs were determined by diffuse reflectance measurements according to the Kubelka Munk theory, revealing a value of 3.24 eV. Therefore, the results indicate the success of this method to create TiO2 nanoparticles in aqueous medium with a good properties to be use like photocatalyst in a very economical and environmentally benign way.
(Invited) Electrostatic and Electrochemical Nature of Liquid-Gated Electric-Double-Layer Transistors Based on Oxide Semiconductors
Authors: Yuan Hongtao 
Published: February 2020

The electric-double-layer (EDL) formed at liquid/solid interfaces provides a broad and interdisciplinary attraction in terms of electrochemistry, photochemistry, catalysts, energy storage, and electronics because of the large interfacial capacitance coupling and their ability for high-density charge accumulation. Much effort has recently been devoted to the fundamental understanding and practical applications of such highly-charged EDL interfaces. For example, electric field control of carrier density with EDL in a transistor configuration has been used as a powerful tool to tune the electronic states of condensed matter. However, the intrinsic nature of the EDL charging, whether it is electrostatics or electrochemistry, and how to distinguish them are far from clear. Here, by combining electrical transport measurements with electrochemical impedance spectroscopy (EIS), we studied the charging mechanisms of highly-charged EDL interfaces between an ionic-liquid and oxide semiconductor, ZnO. The direct measure for mobile carriers from the Hall effect agreed well with that from the capacitance-voltage integration at 1 Hz, implying that the pseudo-capacitance does not contribute to carrier transport at EDL interfaces. The temperature-frequency mapping of EIS was further demonstrated as a “phase diagram” to distinguish the electrostatic or electrochemical nature of such highly-charged EDL interfaces with densities of up to 8×1014 cm-2, providing a guideline for electric-field induced electronic phenomena and a simple method for distinguishing electrostatic and electrochemical charging in EDLTs not only based on a specific oxide semiconductor, ZnO, but also commonly applicable to all types of EDL interfaces with extremely high-density carrier accumulation.
1. H. T. Yuan, H. Shimotani, J. T. Ye, S. J. Yoon, H. Aliah, A. Tsukazaki, M. Kawasaki, and Y. Iwasa, Electrostatic and Electrochemical Nature of Liquid-Gated Electric-Double-Layer Transistors on Oxide Semiconductors,
J

.

Am

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Chem. Soc.
132, 18402 (2010).
2. H. T. Yuan, H. Shimotani, A. Tsukazaki, A. Ohtomo, M. Kawasaki, and Y. Iwasa, Hydrogenation- Induced Surface Polarity Recognition and Proton Memory Behavior at Protic-Ionic-Liquid/Oxide Electric-Double-Layer Interfaces,
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Am

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Chem. Soc.
132, 6672 (2010).
(Invited) A Frequency Domain Optofluidics Dissolved Oxygen Sensor with Enhanced Sensitivity for Water Monitoring
Authors: Mahoney Eric , Du Fei , Hsu HuanHsuan , Selvaganapathy Ravi , Fang Qiyin 
Published: February 2020

Dissolved oxygen (DO) is an important indicator for water quality and is also used in point of care applications. Fluorescence signal from Ruthenium (Ru(dpp)3
2+ ) based fluorophores can be quenched by oxygen such that the reduction of fluorescence signal is proportionally to oxygen concentration. This mechanism allows an optical method to measure DO in liquid. Although optical DO measurements offer high sensitivity and stability, they are also expensive, bulky, and difficult to use due to its complex design and requirement for specialized optical instruments such as light sources and spectrometers. Recently, the advances in microfabricated optical component including waveguides, lenses and mirrors, light sources, and photo detectors enable the integration of optical sensing and microfluidics sampling platform. We report the development of a total internal reflection assisted (TIRA) optical DO sensor for sensitivity enhancement. The excitation light is conducted down the water channel direction in the microfluidic device, while being confined within glass slide by total internal reflection. In addition to steady state intensity measurements, oxygen quenching is measured in the frequency domain using modulated light sources and synchronized detection systems. Experimental results show that optical sensitivity can be increased up to an order of magnitude in TIRA sensors. These results suggest the potential of TIRA scheme as a sensing and characterizing platform for optofluidic sensors.
Single- and Few-Layers MoSe2 Nanoflowers: Synthesis, Characterization, and Their Piezoresponse
Authors: Wu Mei Hsuan , Wu Jyh Ming 
Published: February 2020

We demonstrate a hydrothermal process at temperature of 180oC to synthesize a single to few layers MoSe2 nanoflowers which exhibit a high surface-to-volume ratio and is stable under room temperature in ambient air. The crystal structure of the MoSe2 nanoflowers has been confirmed by X-ray diffraction pattern, Raman, and High-resolution transmission electron microscopy (HRTEM). On the basis of the scanning electron microscope (SEM) image, the size of the MoSe2 nanoflowers is in the range of the 300-500nm. HRTEM image reveals that the MoSe2 nanoflowers possess a great number of the single- and few-layers, which further confirms that our nanoflowers display the plentiful amount of active surface sites. In addition, the lattice fringes between each single layer is about 0.66 nm, which is slightly larger than the reported value of 0.62 nm for the MoSe2. The piezoresponse force microscopy image further shows that the MoSe2 nanoflowers exhibits significantly piezoelectric potential which is generated from the active surface sites of the petals in the MoSe2 nanoflowers.
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3. Alyörük, M.M., et al., Promising Piezoelectric Performance of Single Layer Transition-Metal Dichalcogenides and Dioxides. The Journal of Physical Chemistry C, 2015. 119(40): p. 23231-23237.
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(Invited) Layered Semiconductor Materials and Device Applications
Authors: Jena Debdeep 
Published: February 2020

Several innovative device technologies have been proposed with 2D layered semiconductor materials, of which I will disucss a small sampling that we are investigating in our group. I will present preliminary work investigating semiconducting, and superconducting properties of layered materials and their heterostructures. Several topologically non-trivial electronic states can potentially be realized in such materials, which will be discussed in the framework of device applications. Finally, I will present experimental progress in our group on the epitaxial growth, and device applications of 2D layered materials and their heterostructures.