bluuebunny/crossref_metadata_2025 huggingface dataset:
Porosification of Silicon from the Viewpoint of Nonlinear Dynamics
Authors: Fukami Kazuhiro
Published: February 2020

Anodic dissolution of silicon in HF solutions leads to formation of porous silicon. Formation of a wide variety of porous structures has been reported. In the course of the studies, electrochemical oscillations have been found in silicon anodization. Because a symmetry breaking is necessary for the formation of porous silicon, such oscillatory phenomena have attracted keen attention for the understanding of porous silicon formation.

Formation of macroporous silicon, whose pore diameter is several micrometers, has been explained based on the current burst model proposed by Föll and his colleagues. In the current burst model, macropore formation has been explained based on desynchronization of local oscillators on a silicon surface.Recent studies on nonlinear dynamics in electrochemistry have shown that spatiotemporal pattern formation is closely related to a negative differential resistance (NDR) observed in the current density vs. potential curve. However, NDRs have not been considered in porous silicon formation so far. We have focused our attention on the emergence of NDR in anodization of silicon, and have discussed the spatial pattern formation on silicon.

Recently, we have found that a clear S-shaped NDR is observed after the correction of iR-drop in the electrolyte solution, when using an HF solution containing alcohol such as 2-propanol. In the S-shaped NDR region, an array of microgrooves is spontaneously formed on the silicon surface. Since an S-shaped NDR is induced by a positive feedback which is independent on electrode potential, while electrode potential plays a role of an negative feedback. In the present case, we think that the microgroove array is induced by Turing instability. According to earlier studies, the size of Turing patterns observed in electrochemical systems is on the scale of millimeters. Astonishingly, the size of the present Turing pattern is on the scale of micrometers. In the present paper, the reason why the characteristic size is so small will be discussed in detail. In addition to the Turing pattern formation, formation of other spatiotemporal patterns in silicon electrochemistry, which is difficult to be explained in the classical framework of spatiotemporal pattern formation in electrochemistry, will be discussed.
Electrochemical Regulation of the Cyanobacterial Circadian Oscillation
Authors: Nakanishi Shuji , Hashimoto Kazuhito
Published: February 2020

There has been a growing awareness of a close relationship between circadian oscillation and intracellular redox state in diverse species ranging from cyanobacteria to mammals [1]. The elucidation of this relationship is of physiological importance since malfunction and disruption of the circadian clock can threaten the wellbeing of living organisms. Here we report that the circadian oscillation of the cyanobacterium Synechococcus elongatus PCC7942, the simplest organism found to exhibit circadian oscillation,can be entrained by periodical modulation of the intracellular redox state via electrochemically controlled-extracellular electron transfer (EC-EET), a process in which intracellular electrons are exchanged with extracellular electrodes [2].

In-vivo monitoring of chlorophyll fluorescence revealed that the redox state of plastoquionone pool could be controlled by EC-EET with simply changing the electrode potential in the presence of biocompatible electron mediators. As a result, the endogenous circadian clock of S. elongatuscells was successfully entrained through periodically modulated EC-EET by emulating the natural light-and-dark cycle, even under constant illumination conditions. This represents the first example of regulating the biological oscillation via intracellular redox state by electrochemical technique.

[1] S. Edgar et al.,
PNAS10.1073. (2012).

[2] Y. Lu et al.,
Angew. Chem. Int. Ed., 53, 2208-2211 (2014).
Induced Coherence Resonance in an Electrochemical System
Authors: Rico-Martínez Ramiro , Calderón-Ramírez Mario , Ramírez-Álvarez Elizeth , Parmananda Punit
Published: February 2020

Applying noise to an excitable electrochemical systems near homoclinic orbits may lead to the emergence of coherent dynamics. A noise driver-control was developed for this purpose, using a neural network reference model assisted by a Kalman filter. The model is constructed to predict the occurrence of spiking behavior and its long-term prediction describes the statistics of the spike train. The strategy involving the use of the Kalman filter allows for the on-line correction of model inaccuracies. This adaptive protocol is coupled with a stochastic search algorithm, allowing the pinpointing of the optimal noise amplitude that induces maximum coherence resonance in the system. The protocol was tested in an experimental Fe-potassium sulfate system, exhibiting a robust response even in the presence of electrochemical drift.
Kinetic Resistance: Concept for Elecrochemical and Catalytic Kinetics
Authors: Yablonsky Gregory S
Published: February 2020

It is shown that the steady-state or pseudo-state of rate of complex chemical reaction with a single route can be presented in a form

Rate = (Driving force)/ "Kinetic Resistance" (1)

The driving force is related to the 'mass law expression' for the overall reaction.

The Kinetic Resistance (KR) has a Langmuirian form. It is linear regarding the concentration terms. Coefficients of these terms are Arrhenius parameters or sums of the Arrhenius parameters.

Obviosly, this dependence is similar to the Ohms Law, i.e. rate, driving force and 'kinetic resistance', can be identified with current, voltage and resistance, respectively.

This equation is rigorously proven using graph theory for many classes of linear complex mechanisms which steps are linear regarding intermediates.

As for the non-linear mechanisms, it is rigorously proven for the single route mechanims under typical simplifying assumptions: (a) presence of the rate-determining step;

(b) vicinity of the equlibrium.

In the general case, the rate of complex reaction can not be expressed explicitly as a function of concentration and temperature. It was proven that for the single-route complex reaction with the non-linear mechanism, the kinetic expression is a polynomial F( R, c, T), i.e. a Kinetic Polynomial (KP) , which is implicit regarding the reaction rate. However the thermodynamic branch of kinetic polynomial can be always presented in the form (1) using concepts of the 'driving force' and 'Kinetic resistance'. These resultants have been obtained using the algebraic theory of resultants (1) The concept of kinetic resistance was succefully applied for description of water-gas shift reaction over platinumcontaining catalyst (2)

1. Lazman, M.Z. and Yablonsky, G.S. (2008), in Mathematics in Chemical Engineering and Kinetics, Advances in Chemical Engineering, V.34, Elsevier, Amsterdam, pp.47-102

2. Marin, G, and Yablonsky, G.S., Kinetics of Chemical Reactiions: Decoding Complexity, Wiley-VCH, 2011, 428 pp.
Processing of 2D Layered Materials for Supercapacitors Applications
Authors: Nicolosi Valeria , Mendoza Beatriz , Cohelo Joao , O'Brien Sean , Pettersson Henrik , McGuire Eva , Nerl Hannah , Doherthy Evie , Long Edmund , Barco Jesus , Coleman Jonathan
Published: February 2020

Graphene has generated huge interest in recent years due to its unique physics properties [1, 2]. We have shown that high-quality monolayer graphene can be produced at significant yields by non-chemical, solution-phase exfoliation of graphite in certain organic solvents. Until a few years ago the standard procedure used to make graphene was micromechanical cleavage [1], which is a very low yield production method. In order to fully exploit graphene’s outstanding properties, a mass production method was necessary and the development of a method to exfoliate cheap, commercial graphite in organic solvents down to large area single graphene flakes with high yield was one major achievement [3]. Recently this work had been extended to a wide range of two-dimensional inorganic nanomaterials [4, 5]. These are potentially important because they occur in hundreds of different types with a wide range of electronic properties, varying from metallic to semiconducting.

In this work we present a cost-effective spray deposition technology for the fabrication of both semi-industrial scale and laboratory size film supercapacitor electrodes. Based on graphene and other two-dimensional nanomaterials. Cylic voltammetry, and charge discharge studies revealed a combination of a double layer capacitance and pseudocapacitance charge storage mechanisms that, unlike the many graphene-oxide derived electrodes reported to date, was maintained at unusually high scan rates of 20,000 mV/s. The performance of these graphene electrodes contrasts with that of functionalised single walled carbon nanotubes (SWNTs) electrodes similarly fabricated, which show a sharp decrease in capacitance above a voltage scan rate of 200 mV/s and a nearly complete resistive behaviour at 4,000 mV/s. Electrochemical impedance spectroscopy analysis showed a capacitor response of 17.3 ms and cyclability for 5,000 cycles with 100 % capacitance retention at 10,000 mV/s [6]. We have also exploited the concept of hybridization to combine the properties of two 2D materials in a "hybrid" synthesized by a single step liquid-phase exfoliation method. First synthesized metal oxide-graphene hybrids showed an improved charge storage capacity. This work constitutes the proof-of-concept work for future investigation on rational design of functional 2D hybrid nanomaterials.

A. K. Geim, Science
324, 1530 (Jun, 2009).

S. Stankovich et al., Nature
442, 282 (Jul, 2006).

Y. Hernandez et al., Nature Nanotechnology, 3, 9, 563 (2008).

J. N. Coleman et al., Science, 331, 6017, 568-571 (2011).

5. V. Nicolosi et al., Science, 340, 6139, 1420 (2013)

B. Sanchez et al, Carbon, 52, 337-346 (2013).
Invited: In Situ Characterization of Plasma Assisted Hydrogenation/Fluorination of Graphene and CFx Battery Applications
Authors: Jayasinghe Ruwantha , Sumanasekera Gamini U , Thapa Arjun K , Pradhan Bhabendra
Published: February 2020

Monolayer graphene synthesized by chemical vapor deposition was subjected to controlled and sequential hydrogenation using RF plasma while monitoring its electrical properties in-situ. Low temperature transport properties, viz., electrical resistance (R), thermopower (S), Hall mobility (m), and magneto-resistance (MR) were measured for each sample and correlated with ex-situ Raman scattering and X-ray photoemission (XPS) characteristics. For weak-hydrogenation, the transport is seen to be governed by electron diffusion and low temperature transport properties show metallic behavior (conductance G remains non-zero as 0). For strong-hydrogenation, the transport is found to be describable by variable range hopping (VRH) and the low T conductance shows insulating behavior (0 as 0). Weak localization (WL) behavior is seen with a negative MR for weakly-hydrogenated graphene and this WL effects are seen to diminish as the hydrogenation progresses. A clear transition to strong localization (SL) is evident with the emergence of pronounced negative MR for strongly-hydrogenated graphene.

Multi-walled carbon nanotubes synthesized using fluidized bed chemical vapor deposition technique were fluorinated sequentially to prepare a series of CFx battery electrodes. Primary battery performance was tested using CFx as a cathode against Li. Fully fluorinated MWNTs showed capacity exceeding 815 mAh/g while partially fluorinated samples showed systematically lowered capacity with decreasing x (in CFx). However, fully fluorinated MWCNTs showed distinctly low rechargeable capacity compared to the subfluorinated samples when used as an anode against Li. Mildly fluorinated MWNTs show high capacity and better stability during charge/discharge cycles. High concentrations of fluorine seem to affect capacity retention due to the increased defect densities and reduced electronic conduction. These defects of nanotubes will provide additional pathways for lithium ions to diffuse within the core of the fluorinated structure and to access the electrochemically active C-F sites. XRD, XPS, and Raman spectroscopy were utilized to characterize the samples. Finally the electrochemical performance of fluorinated MWNTs was compared with that of Natural Chinese Graphite (NCG).
Invited: Plasmaelectrochemistry in Ionic Liquids: Challenges to Make Silicon Nanoparticles
Authors: Endres Frank
Published: February 2020

Based on the publications of J. Gubkin et al in the early 20th century we developped together with Juergen Janek the concept of plasmaelectrochemistry in ionic liquids (ILs). ILs have quite low vapour pressures that make them even ultrahigh vacuum compatible. Thus, a low temperature low pressure plasma can be ignited over an ionic liquid and the electrons of the plasma can be used as a reducing agent. By this way we could make several metals as nanoparticles and - interestingly - the particle sizes are in the regime between 10 and 50 nm, dependent on the IL and the experimental conditions. The making of Ge or Si (or SiGe) nanoparticles is complicated by the high vapour pressure of the respective precursors which at the reduced pressure of the plasma experiment are simply pumped off. With a specially designed cell this problem could be solved. It will be shown that Si nanoparticles can be made by plasmaelectrochemistry and that these particles are highly reactive, even against the employed ionic liquid, which makes the analysis a bit challenging (invited).
Designing Knitted Architectures for Applications in Electrochemical Capacitors
Authors: Jost Kristy , Dion Genevieve , Gogotsi Yury
Published: February 2020

In recent years, numerous reports on yarn and fiber capacitors have appeared in the literature. These capacitors have demonstrated excellent electrochemical performance under mechanical stress, making them viable for applications in wearable and flexible electronics [1-3]. However, few of these yarns have been constructed into full size textiles, or tested in lengths longer than a few centimeters.

The goal of this study is to explain how the electrochemical performance is effected when capacitive and conductive yarns are fabricated into different knitted structures. We also identify how researchers can design the capacitance and resistance of a textile capacitor to achieve desired device properties. The capacitance and equivalent series resistance for each geometry is determined from galvanostatic cycling, cyclic voltammetry and impedance spectroscopy. Classic sandwiched, interdigitated (Fig. 1) and modified electrode configurations in fabrics will be discussed. All devices are fabricated on a Shima Seiki industrial knitting machine making these geometries viable solutions for any researcher to scale up their capacitive yarns.

References:

1. K. Jost, G. Dion, Y. Gogotsi, “Textile Energy Storage in Perspective,” Review Article in Issue on Flexible Energy Storage and Conversion, Journal of Materials Chemistry A, Feb. 2014, DOI: 10.1039/C4TA00203B

2. K. Jost, D. Stenger, C.R. Perez, J.K. McDonough, K. Lian, Y. Gogotsi, G. Dion, “Knitted and screen printed carbon fiber textile-supercapacitors for applications in wearable electronics,” Energy and Environmental Science, 6 (2013) 2698-2705

3. K. Jost, C.R. Perez, J.K. McDonough, V. Presser, M. Heon, G. Dion, Y. Gogotsi, “Carbon Coated Textiles for Flexible Energy Storage in Smart Garments.” Energy and Environmental Science. 4 (2011) 5060-5067

Fig. 1. Front and back photographs of stainless steel yarn knitted into a symmetric interdigitated supercapacitor, where each electrode is physically separated by a non-conductive yarn knitted between the fingers.
Highly-Doped, Highly-Strained Germanium and Schottky Electroluminescent Diodes
Authors: El Kurdi Moustafa , Prost Mathias , Ghrib Abdelhamid , Checoury Xavier , Sauvage Sébastien , Zerounian Nicolas , Aniel Frederic , Beaudoin Gregoire , Sagnes Isabelle , Le Thanh Vinh , Luong T.P.K. , Chaigneau Marc , Ossikovski Razvigor , Baudot Charles , Boeuf Frederic , Boucaud Philippe
Published: February 2020

Achieving a monolithic germanium laser source represents a major challenge for silicon photonics. Two key parameters have an impact on the laser performances including threshold, output power, reliability... The first key parameter is the germanium doping. Modeling indicates that an active electron carrier concentration of 3 - 4 x 1019 cm-3 is requested to obtain a robust gain. We will show that such doping level can be achieved for germanium grown on silicon using a co-doping method followed by thermal anneal. The thermal annealing is necessary to minimize the non-radiative recombination processes. The second key parameter is the tensile strain present in germanium. The achievement of high or even record tensile strain values in small volumes is not sufficient for lasing. The homogeneity of the strain field within the germanium volume needs to be taken into account. We will show how it is possible to maximize the tensile strain homogeneity either for straight waveguides or germanium microdisks strained by a silicon nitride stressor. The trade-off between homogeneity and maximum strain value allows one to achieve a more robust modal gain. We will finally discuss the transfer of these concepts for electrical injection.
A Study on the Sensitivity between Oxygen Radical and Negative Color PR in Exposure Process of CMOS Image Sensor
Authors: Hwang Sang Duk , Kim J N , Kim Y J , Choi J K
Published: February 2020

Color filter process for CMOS image sensor process is divided into micro-lens and color layers steps.

And the structure of Color layers is made by building up photo resist(PR).

Then, Color is distinguished by color pattern of image sensor after light induced transmits through the pattern built.

So negative PR is generally used for the structural characteristic.

Negative PR needs high-dose which results in deactivation effect by oxygen radical.

In this paper, the experiment was performed to reduce oxygen radical by adding tool in lithography machine.

As a result, PR sensitivity was developed by reducing Oxygen radical and the process in order to pattern by reduced dose was acquired.
(Invited) Spin Transport in Germanium
Authors: Kawakami Roland Kenji
Published: February 2020

Spin transport in semiconductors forms the basis of potential new technologies in information processing and storage. I will highlight the work leading to the first demonstration of spin transport and precession in germanium. This includes the development of single-crystalline MgO tunnel barriers and ferromagnetic Fe electrodes and their incorporation into lateral spin valves. Measurements in the non local spin transport geometry including Hanle spin precession provides the unambiguous proof for spin injection and transport in germanium. In addition, I will discuss our development of a two-dimensional form of germanium, known as germanane, consisting of hydrogen-terminated honeycomb sheets, similar to graphene. This new 2D material is a direct gap semiconductor with band gap of ~1.5 eV and has favorable properties for spintronic devices.
Shape and Orientation Controlled Vapor-Liquid-Solid growth of Si and Ge Nanowires for Monolithic Device Integration
Authors: Lugstein Alois , Molnar Wolfgang , Zeiner Clemens , Bertagnolli Emmerich
Published: February 2020

Controlling morphology, electronic properties and growth direction of nanowires is an important aspect regarding their integration into devices on technologically relevant scales.

The purpose of the presentation is to illuminate several aspects regarding the vapour-liquid-solid synthesis of group IV nanowires (Si, Ge), their electrical properties, and the fabrication of devices made thereof. Following an introductory survey of nanowire growth methods, experimental results concerning the epitaxial growth of group IV nanowires are presented. The diameter dependence of the growth velocity and crystallographic growth direction of nanowires, a parameter that is of great importance especially in view of the technical applicability of epitaxially grown nanowires will be discussed. After these partially theoretical considerations with regard to the nanowire morphology, the electrical and optical properties of nanowires will be shown.

Finally we will demonstrate shape transfer from a catalytic particle to the nanowire which has to be seen as a proof-of-concept. Given the immense variety of potential binary alloy seeds, we suppose that this approach should not be limited solely to the materials discussed here – other precursors or catalysts should extend this method to other materials.

Having electronic applications of nanowires in mind, theintegration of nanowires in field-effect transistors is naturally the first step. The feasibility of the fabrication process and the basic functionality of nanowire based devices such as gate all around FETs or “straintronic” devices will be demonstrated.
Templated Shadowing-Growth for Photonics and Plasmonics
Authors: Suzuki Motofumi
Published: February 2020

It is well known that electric and magnetic polarizations depend on shape of bodies. Photonic metamaterials which reflect useful properties of shape are obtained by shaping and arraying nanoelements (<< λ) with a narrow spacing (<< λ), where λ is a wavelength of light. On the other hand, photonic monocrystals, polycrystals and amorphous with shape related useful properties are available by arraying the shaped nanoelements in a scale comparable to λ. Hybridization of photonics and plasmonics is also possible if the metallic nanoelements are integrated.

In order to control the shapes of such nanoelements, shadowing growth based on dynamic oblique deposition is quite useful. The shadowing growth enables growth of complex 3D structures without any pre- and post-processes such as lithography and etching and is robust in choosing materials. In addition it is easy to modulate the composition in a direction perpendicular to substrate surface because the dynamic oblique deposition technique is a version of PVD. By using a template, which is either self-assembled or lithographically patterned, we can tune the shapes and growth position of nanoelements. Therefore, the shadowing growth on a template with tailored nanomorphology is a powerful tool to shape and array those nanoelements.

In this presentation, we will show you the peculiar nanomorphology prepared on various templates and some examples of applications to photonics and plasmonics including photonic crystals, polarizers and sensors.
Defect Analysis of Monolithic GaInP/GaInAs/Ge Triple-Junction Solar Cells by Luminescence Technology
Authors: Lin Shih-Hung , Cheng Tzu-Huan
Published: February 2020

The luminescence of solar cell gives unique signatures of the bandgap and cell composition. Electroluminescence (EL) and photoluminescence (PL) of the monolithic GaInP/GaInAs/Ge triple-junction solar cells are investigated to probe each subcell quality. The band-to-band emissions from the GaInP, GaInAs, and Ge junctions are observed at the wavelengths of 0.7, 0.9, and 1.8 μm, respectively. The emission from tunneling junction and defects are also characterized. By adjusting the excitation wavelength, PL spectra can probe individual subcell. EL spectra can measure the spectral uniformity and defect level of individual subcell with selected filter. PL and EL mapping with selected filter corresponding to relative emission wavelength range can help to determine the uniformity, defect, and hot spots of individual layer. The PL and EL emission are related to absorption edge and the temperature coefficient can be used to design the current match condition at operation temperature. PL complementary to EQE measurement can give a quick look of the current matching for cell design. The in-line PL application can also be a real-time diagnostic tool for quality control and yield enhancement.
Templated Growth of Multilayer Graphene from Cellulose for the Fabrication of Photovoltaic Devices
Authors: Dasari Mallika , Hautzinger Mathew , Kohli Punit , Fan-Hagenstein Haiyan
Published: February 2020

Graphene is one of the fast emerging materials in the field of material chemistry. Graphene possesses exceptionally great flexibility, extremely high electrical and thermal conductivity which makes it stand out for numerous applications in materials chemistry. The growing demand to produce high quality graphene inexpensively in larger scale remains a challenge for researchers. Our work emphasizes a straightforward and simple method of high-quality graphene synthesis on substrates with area of many cm2. The multilayer graphene was grown utilizing renewable material (cellulose) as a source of carbon. In our first venture cellulose paper was used as a carbon source soaked in iron catalyst. We achieved high-quality multilayered graphene sheets of ~6.8 cm2 area. In the present talk, I will demonstrate graphene based photovoltaic device (figure 1) with photo-to-electron conversion efficiency ranging from 0.5-2 %. SEM images of nanotubes gave average diameter of the nanotubes to be 200 nm and average nanotubes thickness of 3-10 nm. Graphene films and nanotubes (figure 1 a and b) were characterized using infrared (IR), Raman, X-ray diffraction (XRD), energy-dispersive X-ray (EDS)) spectroscopy; scanning electron (SEM), and transmission electron (TEM) microscopy. The devices are characterized using AFM, Solar-simulator (AM 1.5), and I-V curves.
Effect of Organic Solar Cells by Inserting Pentacene Layer
Authors: Huang Pao-Hsun , Chen Kan-Lin , Shih Neng-Lang , Meen Teen-Hang , Huang Chien-Jung
Published: February 2020

This work have demonstrated the effect of small molecule organic solar cells based on a planer heterojunction of phthalocyanine (CuPc) and fullerene (C60) by inserting pentacene layer between MoO3 and CuPc. The performance of device with structure indium tin oxide (ITO)/MoO3 (5 nm)/pentacene (0~10 nm)/CuPc (20 nm)/C60 (30 nm)/ 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline BCP (10 nm)/aluminum (Al, 100 nm) was enhanced by inserting optimized thickness pentacene layer. The power conversion efficiency (PCE) of device compared to reference information was improved from 0.564% to 0.782%. This achievement of efficiency is not only attributed to the properties of pentacene, which is more suitable in hole transporting ability of high carrier mobility (~1.5 cm2/Vs) and field-effect mobility (~3.0 cm2/Vs), but also the thin MoO3 layer blocks the transfer of electrons into anode and therefore reduces electron leakage current, which leads to the increase of open circuit voltage (VOC), short circuit current (JSC), and PCE. As a result, the pentacene interlayer is also served as a hole transport layer to improve transport of charge carriers and reduce dissociation of excitons.
Water Soluble CdTe Quantum Dots for Mercury Detection
Authors: Elnagar Mohmed , Sakr Abdel-Hamid , Soliman Moataz , Ebrahim Shaker , Abdel-Fattah Tarek M
Published: February 2020

Nanomaterials are becoming one of the most important classes of material research [1]. For example, quantum dots (QDs), especially water soluble QDs, have been used in many areas of research [2-3]. QDs are nanosize crystals of inorganic semiconductors with diameter in the range of 1-10 nm [4]. At such small sizes (close to or smaller than the dimensions of the exciton Bohr radius within the corresponding bulk material), these nanostructured materials behave differently from bulk solids, because of quantum-confinement effects [4]. As a result of quantum-confinement, they have unique optical and electronic properties such as broad excitation spectra and narrow, symmetric and tunable emission spectra [4]. Therefore, QDs have been used as novel luminescent sensors for chemical and biological species [5-8].

This study fabricated cadmium telluride (CdTe) QDs from aqueous solution containing CdCl2 and Te precursor in presence of thioglycolic acid. The resulted QDs were characterized by using Uv-Vis. spectroscopy, photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). The results demonstrated that low concentration, in nano-molar range, of Hg(II) ions could effectively quench the CdTe QDs fluorescence because Hg(II) ions form a stable complex with QDs coating (thioglycolic acid) which allow for an effective electron transfer from the QDs to the Hg(II). A linear response to Hg(II) ions in the concentration range from 0.625 to 8.0 n M was observed and the detection limit of this sensor was 0.625 nM and sensitivity was equal to 53.4 /nM.

References

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Goldman ER, Balighian ED, Mattoussi H, Kuno MK, Mauro JM, Tran PT, Anderson GP (2002) Avidin: a natural bridge for quantum dot-antibody conjugates. J Am Chem Soc 124:6378–6382

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Chan WCW, Maxwel DJ, Gao X, Bailey RE, Han M, Nie S (2002) Luminescent quantum dots for multiplexed biological detection and imaging. Curr Opin Biotechnol 13:40–46

Zhang L, Ci Xu, Li B (2009) Simple and sensitive detection method for chromium(VI) in water using glutathione—capped CdTe quantum dots as fluorescent probes. Microchim Acta 166: 61–68

Landes C, Burda C, Braun M, El-Sayed MA (2001) Photoluminescence of CdSe nanoparticles in the presence of a hole acceptor: n-Butylamine. J Phys Chem B 105:2981–2986

Dong F, Hu K, Han H, Liang J (2009) A novel method for methimazole determination using CdSe quantum dots as fluorescence probes. Microchim Acta 165:195–201
Effect of the Diameter on the Band Gap of ZnO Nanorods
Authors: Kasim Muhd Firdaus , Kamarulzaman Norlida , Rusdi Roshidah
Published: February 2020

ZnO nanomaterials have different properties from the bulk. One interesting property is band gap. It is found that the band gap is dependent on the dimensions of the nanostructures. Many methods have been used by researchers [1-7] to produce ZnO nanostructures but amongst the soft chemistry methods, chelating agents are normally used [1,6,7]. In this work zinc oxide nanostructures have been synthesized using the sol-gel synthesis method. The effect of a synthesis with and without the use of gelling agent is investigated. One sample is done using a sol-gel synthesis route using tartaric acid and the other sample is synthesized without using a gelling agent at all. Results showed that the samples are pure, however the sample prepared without using the gelling agent are made up of rods with long aspect ratios while the one obtained using the gelling agent are made up of rods with lower aspect ratios. It is found that the band gap of the high aspect ratio ZnO is smaller than the one with low aspect ratio. This is attributable to the lattice expansion of the lower aspect ratio ZnO nanorods as obtained from quantitative X-Ray diffraction. Therefore, a characteristic of ZnO nanomaterials is dependent on their dimensions.
Interaction of Silicene and Germanene with Non-Metallic Substrates
Authors: Houssa Michel , Scalise Emilio , van den Broek Bas , Lu Augustin , Pourtois Geoffrey , Afanas'ev Valeri V. , Stesmans Andre
Published: February 2020

Silicene, the silicon counterpart of graphene, has recently attracted a lot of attention as an alternative 2D materials to graphene for nanoelectronic devices. So far, the likely existence of silicene on Ag(111) surfaces has recently been reported, by combining experimental and first-principles simulations (1,2). The growth of silicene has also been reported on other metallic substrates, like (0001) ZrB2 (3) and (111)Ir (4).

However, the characterization of the electronic and electrical properties of silicene on metallic substrates is very challenging, since these properties can be largely dominated by the substrates. In addition, potential applications of silicene in nanoelectronic devices will also require its growth on non-metallic substrates.

We report here on the theoretical study of the interaction of silicene and germanene (2D Ge counterpart of graphene) with non-metallic substrates, using first-principles simulations. We first studied the weak (van der Waals) interaction between silicene or germanene with metal chalcogenide substrates (5,6). The buckling of the silicene/germanene layer is found to be correlated to the in-plane lattice mismatch between the free-standing silicene or germanene layer and the metal dichalcogenide layer. Highly buckled silicene (e.g. on MoS2) is predicted to be metallic, while low buckled silicene (on e.g. GaSe) is predicted to have Dirac cones at the K-points.

We next investigated the interaction between silicene or germanene with (0001) ZnS or (0001) ZnSe surfaces (7,8). In this case, part of the Si (Ge) atoms form covalent bonds with the substrate, leading to the opening of a gap in their energy band structure. Very interestingly, the value of this energy gap can be controlled by an out-of-plane electric field, leading to field-driven semiconductor to metal transitions at these interfaces – which could be very promising for the potential use of silicene and germanene in field effect transistors.

Part of this work has been financially supported by the European Project “2D Nanolattices” within the Future and Emerging Technologies (FET) program of the European Commission, under FET-grant number 270749, as well as the KU Leuven Research Funds, project GOA/13/011.

References

1. P. Vogt et al., Phys. Rev. Lett. 108, 155501 (2012).

2. D. Chiappe et al., Adv. Mat. 24, 5088 (2012).

3. A. Fleurence et al., Phys. Rev. Lett. 108, 245501 (2012).

4. L. Meng et al., Nano Lett. 13, 685 (2013).

5. D. Chiappe et al., Adv. Mat., in press (2014).

6. E. Scalise et al., 2D Materials, in press (2014).

7. M. Houssa et al., Phys. Chem. Chem. Phys. 15, 3702 (2013).

8. M. Houssa et al., Appl. Surf. Sci. 291, 98 (2014).
Investigation of Frenkel-Pair Formation in HfO2 and Its Influence on OxRAM Memory Reliability
Authors: Vianello Elisa , Blaise Philippe , Traoré Boubacar , Xue Kanhao , Fonseca Leonardo , Molas Gabriel , de Salvo Barbara , Perniola Luca , Nishi Yoshio
Published: February 2020

Oxide based RRAM memories are considered as potential candidates to replace floating gate memory devices [1-2] due to their proven low power operation , high switching speed [3] and compatibility with conventional CMOS back-end-of-line process. The working principle relies on the reversible change of the oxide layer’s resistance between two levels namely HRS (High Resistance State) and LRS (Low Resistance State). This resistance change has been widely attributed to the creation/reconstruction and rupture of a localized or multiple conductive filaments (CF) in the oxide layer. Various companies [4] and research laboratories [5] have adopted the HfOx solution as the active oxide layer that casts the memory effect. However, the process of the CF creation responsible for resistive switching and the oxide layer degradation are yet to be fully explored.

In this paper we use first principles calculations to investigate Frenkel-Pair formation (FP) in HfO2 that play an important role in the CF creation. Depending on the electrode nature, its work function and reactivity with oxygen, we bring more insight into the FP formation leading to CF creation and device reliability. We show that oxygen active electrodes with low work function, like Ti, improve device reliability. Finally, endurance tests on a memory cell with Ti as top electrode were performed to assess cycling stability. Endurance up to 108 cycles, with optimized set conditions has been demonstrated.

[1] H. Akinaga and H. Shima, Proc. IEEE, vol. 98, p. 2237, 2010.[2] V. Sriraman et al., IPCSIT, vol. 32, p.101, 2012 [3] B. Govoreanu et al., IEDM Tech. Dig., pp. 729-732, 2011 [4] Ch. Walczyk et al., J. Vac. Sci. Technol. B 29, 01AD02 (2011) [5] Y.S.Chen et al., IEDM Tech. Dig,pp. 31.3.1 - 31.3.4,2011.
Resistive Switching Characteristics and Controllable Quantized Conductance in Single-Crystal Anatase TiO2 on Si (001)
Authors: Yu Edward T. , Hu Chengqing , McDaniel Martin D. , Posadas Agham B. , Demkov Alexander A. , Ekerdt John G.
Published: February 2020

Resistive switching in TiO2 has been studied extensively for resistive random access memory and other applications in nanoelectronics; nearly all of these studies have employed polycrystalline or amorphous TiO2. We have used atomic layer deposition to grow single-crystal anatase TiO2 thin films on Si (001) substrates, with single-crystal SrTiO3 grown by molecular beam epitaxy serving as a buffer layer between the TiO2 and the Si substrate. Resistive switching devices are then fabricated with the bottom electrode consisting of the SrTiO3/Si substrate, and the top electrode formed by deposition of 5-8nm Ti followed by 160nm Au [Figure 1(a)-(b)]. Highly stable bipolar resistive switching and very linear current-voltage characteristics in the on (low-resistance) state are consistently observed [Figure 1(c)-(d)]. For a subset of devices studied, the single-crystal TiO2 was annealed after 3nm deposition, resulting in formation of oxygen vacancies in that layer. In all the devices, deposition of Ti for the top electrode also creates oxygen vacancies near the top of the TiO2 layer. The oxygen vacancies, created either by annealing or by Ti deposition, play a key role in the bipolar resistive switching processes observed. Detailed analysis of electrical behavior in these devices reveals that switching between the high-resistance and low-resistance states occurs via an electrochemical metallization-like mechanism in which oxygen vacancies form a highly conductive filament during the device SET process, which then dissolves during the RESET process. Extremely high resistance ratios between the off (high-resistance) and on (low-resistance) states – as high as 107 – are regularly observed, which we attribute to the highly insulating nature of the single-crystal TiO2 layer. In addition, we observe that the on-state conductance can be controlled quite precisely and reproducibly via the compliance current imposed during the measurement, and assumes values that are integer multiples of G
0 = 2e
2/h, the fundamental quantum of conductance for a single-mode ballistic conductor. At compliance currents of 10-200µA, on-state conductance can be controlled to within a single quantum of conductance by imposing a given compliance current during the device SET process (Figure 2). These results demonstrate substantial advantages of single-crystal TiO2 as a material for resistive switching devices, and suggest a variety of avenues for integration into high-density memory arrays and elucidation of issues relevant to scaling potential.
The Study of Charge Trapping in Mahas Memory Structure with Various HfO2 Trap Layer Thicknesses
Authors: Na Heedo , Oh Jinho , Lee Kyumin , Sohn Hyunchul
Published: February 2020

Recently, charge trap type memory devices are developed to replace the conventional floating-gate flash memories for high quality memory operation in dense memory cell array. However, memory reliability characteristic degradations have arisen from the tunnel oxide thickness scale down in the ‘ONO’ (SiO2/Si3N4/SiO2) type charge trap memory. To overcome this limitation, high-k dielectrics have been attempted by replacing the charge trap layer (CTL) SiNx / blocking layer (BL) SiO2. Especially, HfO2 and Al2O3 have been mainly developing for CTL and BL, respectively. But, it is still required to investigate the high-k dielectrics scale down for improvement of memory performance. In this study, optimized thickness of the HfO2 CTL was investigated in Junctionless devices with poly silicon channel. Increase Step Pulse Program (ISPP) characteristic in HfO2 CTL device show less sensitive to thickness scale down than SiNx CTL device. But, under the 6nm of HfO2 thickness, ISPP slope degradation was observed by high applied voltage pulse. It is expected that amount of tunneling electron through the Al2O3 BL is increased by decrement of dielectric thickness. By program/erase results, 4.6nm SiNx CTL device show poor erase characteristic comparison with HfO2 CTL device. Consequently, very slow program and erase operation during endurance test was observed in SiNx CTL device. For these results, we are expected that optimized HfO2 CTL can be replaced conventional SiNx CTL for next generation NAND flash memory.
Integration of Photodefinable Polybenzoxazole as Intermetal Dielectric for GaAs HBT Technology
Authors: Yota Jiro , Do Benny
Published: February 2020

Polybenzoxazole (PBO) is a polymer dielectric that has excellent mechanical, physical, and electrical characteristics and that is used for various semiconductor thin film applications. The PBO has low dielectric constant, and has good thermal stability and thermo-oxidative resistance. Furthermore, the PBO material can be applied by spin-coating and can be cured at temperature of <300oC, which is significantly lower than many other spin-on dielectric materials. These characteristics make PBO suitable for use in many semiconductor technologies and applications that require the processing temperatures not to exceed 300oC, such as GaAs hetero-junction bipolar transistor (HBT) technology. The PBO material is easily processed, and can be made photodefinable by adding photoactive compounds, and therefore be patterned on semiconductor wafers. By using a photodefinable PBO dielectric material, there will not be any need to perform patterning by dry-etch process steps that are typically performed in GaAs technologies.

In this study, photodefinable PBO has been integrated as intermetal dielectric in GaAs HBT technology. Process module optimization and integration studies were performed and the PBO results and process flow were compared to those of dry-etch polyimide, which is typically used as intermetal dielectric in GaAs technology. The photodefinable PBO is shown to allow the intermetal dielectric process flow to be simplified and the number of processes and equipments to be reduced. Results show that PBO has more planarity than polyimide, when coated on GaAs HBT wafers, which typically have significant topography. The PBO photolithography coat, expose, and develop processes were optimized in order to obtain the desired dielectric thickness and the required via dimension and sidewall profile, in addition to removing the PBO from the die street. The PBO thermal curing process was performed at 300oC, while ashing was performed to remove any PBO residue in the vias and streets. Figure 1 shows the FIB/SEM images of GaAs wafer after deposition of Metal 1 and coated with photodefinable, after via expose and develop, after cure, and after ash. Figure 2 shows the GaAs HBT wafer with (a) dry-etch polyimide and (b) photodefinable PBO used as intermetal dielectric. These results show that the photodefinable PBO film is compatible with, is suitable for, and can be integrated as intermetal dielectric in GaAs HBT technology.
New Approaches to Realizing High Power Nitride Based Field Effect Transistors
Authors: Shur Michael , Simin Grigory , Gaska Remis
Published: February 2020

High breakdown voltage, excellent current carrying capabilities, high electron saturation velocity, high mobility, good thermal properties, chemical inertness, and radiation hardness of nitride semiconductors make them uniquely suited for high power applications. However, new approaches are needed to achieve their full potential. We report on several key innovations that include (1) the use of Perforated Channel (PC) design (to control and minimize the parasitic and on resistances and off and on transistor capacitances for faster switching and sharply reduced losses); (2) surface application of Low Conducting Layers (LCLs) (to control the properties and stability of ungated surfaces and dramatically increase the breakdown voltage); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors with unprecedented power handling capability); (5) improved control of self-heating and better heat dissipation using the PC channel design. We also review our recent results exploring the PC channel and LCL designs [1-3]. These experimental and simulation results demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.

[[1]] G. Simin, M. Islam, M. Gaevski, J. Deng, R. Gaska, and M. Shur, “Low RC-constant Perforated-Channel HFET”, IEEE Electron Device Letters, 35 (2014)

[2] M. Gaevski, Jianyu Deng, A. Dobrinsky, R. Gaska, M. Shur, and G. Simin, Static and transient characteristics of GaN power HFETs with low-conducting coating, physica status solidi, Article first published online: 24 MAR 2014 | DOI: 10.1002/pssc.201300541

[3] G Simin, M Shur, R Gaska, Semiconductor device with low-conducting buried and/or surface layers - US Patent Application 20,130,126,905 (2013)
III-V Nanowire MOSFETs in RF-Applications
Authors: Wernersson Lars-Erik
Published: February 2020

III-V MOSFETs are currently being considered for logic applications with the aim to increase the drive current at reduced power consumption. The benefits of the III-V material include a high injection velocity and the possibility to operate close to the ballistic limit, whereas the cylindrical geometry provides electrostatic control. The devices may also find RF-applications that will require studies of further metrics like the on-resistance, the output conductance, and the voltage gain. For device applications it is essential to consider the complete transistor architecture to optimize the layout and to minimize parasitic elements.

In this talk, we will discuss the possibilities and benefits of using III-V Nanowire MOSFETs in RF-applications. In particular we will demonstrate:

Integration III-V nanowires on 4” Si substrates

Interface characterization of the III-V/High-k surface

Design of transistor architectures at scaled gate lengths

RF-performance for 200 nm Lg devices

Strategies to integrate p-type devices

Operation of InAs MOSFET RF down-conversion mixers on Si substrates
Structural and Optical Properties of Phase Change Material in Sb2Te3 Thin Film
Authors: Choi Hyejin , Jung Seonghoon , Kim Taehyeon , Park Jaehun , Jeong KwangHo , Cho Mann-Ho
Published: February 2020

Chalcogenide based compound, especially Sb2Te3 and related compounds, exhibit pronounced structural and optical contrast with rapid phase transition from amorphous and crystalline phase. This makes them suitable candidates for rewritable optical storage media and phase change random access memory. Simultaneously, Sb2Te3 have reported that one of the best p-type thermoelectric materials characteristics at room temperature, and topological insulators property. As electron and phonon plays a crucial role in determining the performances of any real devices, a better understanding of the amorphous phase and crystal phase, and the transition mechanism between them, is imperative. Recent, Optical pump THz probe spectroscopy (OPTP) is a powerful tool to study the ultrafast carrier dynamics of structural phase transition occurring on ultrafast time scales, as has been applied to a variety of materials, such as semimetal and semiconductor, and Mott insulators examined by using a femtosecond pump-probe technique and found that the appearance of the coherent vibrational modes was significantly modified upon the phase change.

In this study, we investigate ultrafast carrier dynamics in {Sb(3)Te(9)}n thin film that the phase change from amorphous into crystalline states can be explained by THz-TDS and OPTP, which is the relationship between structural phase transition and optical properties transition in THz range. We observed that OPTP spectroscopy was closely dependent on phase of the Sb2Te3 film, indicating that decay time is a crucial carrier dynamics mechanism to the phase transformation process.