bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of Defect Evolution and Distribution in Thermally Cycled Cu-TSVs
Authors: Marro James Brandon , Okoro Chukwudi A , Obeng Yaw S. , Richardson Kathleen A , Chamma Karima
Published: February 2020

Through-silicon vias (TSV) are copper (Cu) interconnects used in three dimensional integrated circuits (3D-IC) and other packaging to allow inter-chip communication. A thermo-mechanical reliability concern for Cu-TSVs, are the formation of voids, which are indicative of the stresses undergone by the structures. Voids can degrade signal propagation by acting as scattering centers and if large enough, can prevent the passage of current [1]. Simulations of fabrication conditions such as back-end-of-the-line (BEOL) addition, have been conducted by isothermal heating or minimal cycling [2-4]; however, few studies have focused on in-use conditions where chips undergo many cycles at lower temperatures, simulating environmental changes and joule heating from use. This study replicates these in-use conditions to evaluate defect evolution and distribution in thermally cycled Cu-TSVs. Silicon (Si) chips containing blind Cu-TSVs were cycled 2000 times from room temperature to maximum cycling temperatures of 100 °C, 150 °C, or 200 °C. Residual voiding from fabrication was considered by examining two sample types (shown in Fig. 1), specimens that contained Cu-TSVs with seams and large bottom voids and those that exhibited only microvoids. The S11 parameter was measured at 500 cycle increments and determined signal loss trended with maximum cycling temperature and initial void area, but not with number of cycles. To further investigate void development, the TSVs were cross-sectioned for internal evaluation using a combination of grinding, polishing, and ion beam milling. Voids were then studied using focus ion beam (FIB) and scanning electron microscope (SEM) images to record void dimensions and locations within the Cu of the TSVs. Void area was observed to increase with increasing maximum cycling temperature from 100 °C to 200 °C, however, this increase is a result of void nucleation as opposed to pre-existing void growth. While rapid cycling (~5 min/cycle) under in-use conditions for these Cu-TSVs did not allow diffusion and growth of voids, maximum cycling temperatures provided sufficient driving force for stresses to form new voids in the Cu.

Fig. 1: SEM micrographs of the TSV cross-sections for the two as-received sample types: (a) containing seams and large bottom voids and (b) solely containing microvoids.

References:

1. J. Kim, J. Cho, J. S. Pak, J. Kim, J. Yook, and J. C. Kim, Electrical Performance of Electronic Packaging and Systems (EPEPS), 2011 IEEE 20th Conference on 243-246 (2011).

2. H. Shin, B. Kim, J. Kim, S. Hwang, A. Budiman, H. Son, K. Byun, N. Tamura, M. Kunz, D. Kim and Y. Joo, Journal of Electronic Materials, 41 [4] 712-719 (2012).

3. L. W. Kong, J. R. Lloyd, K. B. Yeap, E. Zschech, A. Rudack, M. Liehr and A. Diebold, Journal of Applied Physics, 110 [5] 053502 (2011).

4. L. Kong, A. C. Rudack, P. Krueger, E. Zschech, S. Arkalgud and A. C. Diebold, Microelectronic Engineering, 92 [0] 24-28 (2012).
An Efficient Phase Field Model for Electrostatics in Complex Dielectric Heterostructures
Authors: Cheng Tianle , Wen Youhai
Published: February 2020

At the microstructural level, dielectric inhomogeneity is ubiquitous in common ceramic, polymer and composite materials. If the characteristic length scale of the dielectric heterostructure is critical to the problem of interest the position dependent dielectric constant needs to be explicitly considered. Such examples include dielectric performance of a composite, ionic transport in metal oxides containing precipitates, micropores and/or cracks (e.g., during high temperature metal oxidation), and dielectrophoresis of small particles. A bound-charge phase field model is developed to address the dielectric heterogeneity problem. The model solves electrostatic problems by using a fast-converging iteration algorithm and Fast Fourier Transform. Excellent efficiency of the model is observed that demonstrates its potential for many practical applications.
Current Status of Slurries and Cleans for CMP of III-V Device Fabrications – a Critical Review
Authors: Banerjee Gautam
Published: February 2020

With the growth of cloud computing market, the need for logic and memory chips for data centers have been steadily growing which require low power and high performance. Another area of growing semiconductor application is mobile products which require increasingly higher performance without sacrificing power. The above two requirements can only be achieved by scaling supply voltage(Vdd).

III-V materials enable Vdd scaling to address power without sacrificing performance due to the very high electron injection velocity at virtual source compared to Si. For example,
Vinj

(InGaAs) > 2
Vinj

(Si) at less than half VDD.

The development at Intel on InGaAs and at IMEC on Ge based FinFET structures have made it possible to conceive the integration scheme such as depicted in http://www.compoundsemiconductor.net/csc/features-details/19732136/Uniting-III-Vs-and-germanium-for-CMO.html .

In order to enable such CMOS fabrication, development of CMP slurry, post CMP clean and modification of the presently available process tools need to be done. While new slurries and cleans will be needed to planarize III-V film layer(s) without compromising the film composition (and functionality), modification of the process tool will be needed to address potential release of toxic waste water into the the waste stream after planarization.

At this time, published results show some academic works in addressing various issues related to CMP of III-V materials but there are not many reports in the public domain from the industry to address the need which is essential to successfully integrate CMP as an enabling step in the manufacturing of III-V CMOS devices.

In this paper, the status of development of CMP processes, slurries and post CMP cleans will be reviewed and the critical needs to enable for the future III-V device integration will be analyzed.
(Invited) Study of Carrier Localization, Carrier Transportation and Carrier Recombination Processes in Blue-Emitting InGaN/GaN MQWs
Authors: Li Cheng , Stokes E. B. , Armour Eric A
Published: February 2020

InGaN/GaN MQWs grown on c-plane sapphire substrate show high internal quantum efficiency, regardless of their high threading dislocation density (108 cm-2~ 1010 cm-2) that is introduced by lattice mismatch. This high-IQE phenomenon is attributed to bandgap energy fluctuation and carrier localization in the QW layer [1].

In the present work, temperature-dependent PL, confocal microscopy, and nanometer-scale time-resolved photoluminescence (TRPL) spectroscopy were employed to analyze the carrier localization, carrier transportation and carrier recombination processes in blue-emitting InGaN/GaN MQWs.

The temperature-dependent PL spectra were taken from 10 K to 300 K. The decreased spectrum-integrated PL intensity with increasing temperature was observed, which was fitted with second-order Arrhenius equation, as shown in Fig. 1. The fitting indicated two non-radiative channels: the one with high activation energy (dominated at high temperature) corresponded to thermal activation of carriers out of the strongly localized states, while the one with low activation energy (dominated at low temperature) corresponded to thermal activation of carriers out of the weakly localized states. The S-shaped shift of PL peak energy and the inverse S-shaped shift of PL FWHM were also observed, as shown in Fig. 2 and Fig. 3, which were explained with carrier localization and carrier dynamics.

The confocal microscope image collecting near bandedge emission showed inhomogeneous PL intensity distribution, as shown in Fig. 4. Previous analysis [2] has shown that the bright region had smaller bandgap energy than dark region did. Nanometer-scale TRPL spectra were taken at different places in the confocal microscope image. As shown in Fig. 5, TRPL spectra taken at the center of bright region and the center of dark region show single exponential decay, which are characterized by a single lifetime and corresponds to carrier localization in strongly localized state and weakly localized state, respectively. Comparing with bright region, dark region has shorter lifetime, indicating a higher probability of nonradiative recombination and carrier transportation from dark region to bright region. TRPL spectrum taken at the boundary of bright region, however, shows double exponential decay, as shown in Fig. 5, which is characterized by two lifetimes. The short lifetime corresponds to carrier transportation from weakly localized state to strongly localized states, while the long lifetime corresponds to carrier recombination at local strongly localized state.

References:

1. R. A. Oliver, et al., Journal of Physics D-Applied Physics, 43, 35 (2010)

2. C. Li, et al., ECS Journal of Solid State Science and Technology, 2, 11 (2013)
Photo-Electroless-Etching of Wide Band Gap Material for Flexible Solid-State Devices
Authors: Slimane Ahmed B , Ng Tien K , Ooi Boon S
Published: February 2020

We report on photo electroless chemical (PEC) etching of III-Nitride material for thin layer lift-off for flexible solid-state light emitting devices. We investigate three different structures: 30 µm unintentionally doped GaN on sapphire, 30 µm n-type GaN on sapphire, and 200 nm InGaN on 4 µm unintentionally doped GaN on sapphire with different indium composition. Initially the three structures were etched as-grown for the same duration and the same conditions in a HF/CH3OH/H2O2 solution under UV illumination. Scanning electron microscopy (SEM) measurements performed on the etched samples reveals porous structure and high density nanowire on the surface, as well as the formation of V-shaped pits. The etch rate in each structure were compared. Optical study were performed using photoluminescence (PL) and Raman spectroscopies to analyze PL peak shift and phonon frequency shift compared to the as-grown, which we attributed to the compressive strain relaxation and localized impurity formed in the crystalline structure after PEC etching. We also fabricated microcolumns of diameters ranging from 5 to 100-µm via inductively coupled plasma (ICP) etching process in the InGaN on GaN samples. Dry etching of micropillars exposes unintentionally doped GaN to the wet etching. We study the selectivity of GaN over InGaN in the PEC etching process. SEM images reveal lateral etching and porous GaN layer formation under the InGaN after wet etching. We compare etching process in the InGaN structure with and without microcolumns. PEC etching is sensitive to band bending in the surface of the semiconductor and electrolyte, when InGaN surface is in contact with HF solution, oxidation and reduction reaction happens at slow rate and leads to the porous structure in the surface. However, when the GaN under the InGaN is exposed, the etching in this layer is preferred due to the low resistivity and the confinement of the photogenerated minority in the upward band bending depleted region near the contact surface between GaN and electrolyte.

Undercut InGaN microdisks were lifted off for optical study via flexible polydimethylsiloxane (PDMS) material. Microdisks were then transferred on to a Si wafer for PL measurements. We also performed Raman study on the microdisks and observed a shift in the phonon frequency attributed to the relaxation of the compressive strain with respect to the as-grown. InGaN microdisks with higher indium composition were transferred on a blue LED for optical pumping. Optical measurements on transferred microdisks revealed typical prominent visible peaks. These observations confirm the promising application of this technique to selectively etch III-V semiconductor. The lift-off process is a compelling technique for next generation transferred substrate devices and III-Nitride micro phosphor fabrication.
(Invited) Carbon Nanotube Based Photonics
Authors: Noury Adrien , Le Roux Xavier , Gaufrès Etienne , Vivien Laurent , Izard Nicolas
Published: February 2020

The use of optics in microelectronic circuits to overcome the limitation of metallic interconnects is more and more considered as a viable solution. Numerous photonic building blocks, compatible with CMOS technology, have been developed. However, integration of all these building blocks on the same chip is a bottleneck, due to the various materials used (Ge, Si, III-V). This drawback could be significantly overcome by considering carbon nanotubes, which have the ability to emit, modulate and detect light in the wavelength range of silicon transparency. That makes them a promising candidate and in consequence an alternative material for active device in silicon photonics technology.

Few years ago, we have developed an efficient method to extract semiconducting nanotube (s-SWNT), using a polyfluorene agent in toluene followed by ultracentrifugation steps [1]. We demonstrated that this method allows obtaining metallic-free s-SWNT samples, as confirmed by photoluminescence, absorption and Raman spectroscopy, and the realisation of high Ion/Ioff FET devices.

This achievements leads to the first experimental demonstration of a strong optical gain of 160 cm-1 at a wavelength of 1.3 µm in (8,7) s-SWNT at room temperature [2]. A special emphasis will be put on the s-SWNT extraction, as optical gain could not be achieved in a raw or lowly extracted sample.

Carbon nanotube properties were then relied on the existing silicon photonic platform, and we envision the use of carbon nanotubes as active optoelectronic devices in silicon. A complete study of the coupling between carbon nanotubes and silicon waveguides was performed [3]. In particular, temperature independent emission up to 100°C from carbon nanotubes in silicon was demonstrated, which opens bright perspectives for future high performance integrated circuits

(Figure : Integration scheme of carbon nanotube with silicon waveguide, showing carbon nanotube emission throught the waveguide)

[1] N. Izard, S. Kazaoui, K. Hata, T. Okazaki, T. Saito, S. Iijima and N. Minami, Appl. Phys. Lett., 92, 243112 (2008)

[2] E. Gaufrès, N. Izard, X. Le Roux, D. Marris-Morini, S. Kazaoui, E. Cassan and L. Vivien, Appl. Phys. Lett., 96, 231105 (2010)

[3] E. Gaufrès, N. Izard, A. Noury, X. Le Roux, G. Rasigade, A. Beck and L. Vivien, ACS Nano, 6, 3813 (2012)
Correlation of Surface Composition to Optical Properties of CdSe Nanocrystals
Authors: Shakeri Behtash , Meulenberg Robert W
Published: February 2020

Understanding the role that surface chemistry plays in modifying the optical properties of quantum dots (QDs) has been an active field of research for some time now. Recently, one of the goals of many research groups involve possessing systematic control of the ligand exchange process which can provide the ability to tailor the surface with a specific amount of surface ligand, thereby having unparalleled control over the optical properties. In this presentation, we will discuss our efforts towards investigating controlled efforts of ligand exchange in CdSe QDs. Most notably, we focus on the trioctylphosphine oxide (TOPO) coated CdSe system with efforts towards exchanging phosphine oxide derivatives onto the QD surface. Using a combination of nuclear magnetic resonance and infrared spectroscopy and thermogravimetric analysis, we probe the extent of ligand exchange of a function of incoming ligand concentration and QD particle size. We also discuss the effects of multiple washing of the QDs during the cleaning process – QD materials that still possess quantum confinement like features, yet is not dispersible in typical organic solvent. Titrations of ligands from the excessively cleaned materials lead to dispersed QDs. During the course of these measurements, we will discuss the impact these surface chemistry treatments have on the photoluminescence of these materials.
Consolidated Vacuum Sublimation Module: a Purification Apparatus and Process for Solid-Phase Materials
Authors: May Michael , Paul Elizabeth , Katovic Vladimir
Published: February 2020

A consolidated Vacuum Sublimation Module [cVSM] provides engineering improvements over conventional sublimation apparatus. As implied, the cVSM is structurally modular and it comprises: valve stem unit, valve/Collector/jacket unit, lower glass body, FKM seals, threaded PTFE bushing, and an internal glass cartridge [see US patent 7794694]. In association with the cVSM, a batch sublimation process was developed to purify solid-phase materials such as ferrocene, perylene, oxalic acid, and pentachlorobenzene.

To effect sublimation, the lower glass body is controllably heated to establish a vertical temperature gradient. The temperature gradient along the [evacuated] lower body surface was measured versus input electric power. At steady state, an input of ~37 watts generated +530K at z=0 and +314K near z=95 mm. When operated with natural cooling, the starting material recovery was typically ≥95 mass%. Design features of said Module include: concentric multi-tubular geometry, elongated tapered Collector, positively compressed seals, natural Collector cooling, minimal power consumption, transparency, and glovebox compatibility. The [static vacuum] leakage of an empty cVSM measured <20 ppmv of air per hour. Lastly, the prototype Module has been moderately scaled-up and demonstrated.
Al-Zn Alloy Formation from Non-Aqueous Solution By Electrochemical Technique
Authors: Sano Katsuhito , Tasugi Naoya , Watanabe Nobuaki , Koiwa Ichiro
Published: February 2020

Introduction

At present, the hot dipping of Zn-Al, uses to suppress the corrosion of the steel. In addition, Al-Zn alloy become a high strength material such as duralumin by making the alloying with Mg and Cu.

An aluminum, that is less noble than hydrogen is, not able to be electrodeposited from aqueous solution.1)Therefore, the electrodepositions using ionic liquids or non-aqueous have been studied. However solution such as toluene, which has a risk of causing a spontaneous combustion because of it’s high flammable. An ionic liquids are salts whose melting point less than 100 ℃. Since the solution has very high electrical conductivity, high stability and, low volatility, it is suitable for plating solvent.

In this study, we report on the results of the plating of the Al-Zn alloy films from the plating bath with AlCl3, ZnCl2 and dimethyl sulfone (DMSO2).

Experiment

The plating solution was composed of AlCl3, ZnCl2 and DMSO2. The total metal chloride ratio, (AlCl3 + ZnCl2) / (DMSO2 + AlCl3 + ZnCl2), is constant at 33.3 mol%. The ratio of ZnCl2 to AlCl3 is controlled from 0.005 to 1.0 mol%. A current density is 600A/m2. The acid activating (RT, 1min) after alkaline degreasing (60 ℃, 5min) is performed as pretreatment process. The plating was performed at 150 ℃ for 30 minutes. As analysis method of sample, we used X-ray diffraction (XRD), energy dispersive x-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS).

Results and Discussion

Effect of bath composition

As a result of changing the bath composition, metallic gloss plating film was deposited up to 0.05 molar percent metal salt concentration of Zn. The gray film was obtained in 1.0 molar percent.

Results of by EDS

The composition of the deposited Al-Zn alloy plating films was estimated by using EDS. The content of Zn is increased with increasing the concentration of the metal salt Zn.

Result by X-ray diffraction (XRD)

Figure 1 shows an XRD pattern of the sample. The peak of the Al can observed without the sample of 0.1 molar percent of Zn salt.

Figure 2 shows an enlarged view of Al (200) peak area. With increasing of the Zn metal salt concentration, the diffraction peak is shifted to a lower angle side, and the half width is increased. An atomic radius of Zn and Al are 125 and 135 pm, respectively. The diffraction peak will be shifted to high angle in accordance with Vegard’s low, when Zn is replaced by Al site. The increase of half width shows deterioration of crystallinity.

Acknowledgements

This work was partially aided by MEXT-supported Program for the Strategic Research Foundation at Private Universities.

References

T. Hirato, J. Fransaer, and J. P. Celis,

J. Electrochem.Soc., 148, C280 (2001).
Synthesis of Ellipsoid TiO2 Nanoparticles and Their Application to Photoelectrodes of Dye-Sensitized Solar Cells
Authors: Shimoyama Yuki , Furue Miwako , Kikuchi Takahiro , Tomita Koji , Kunugi Yoshihito
Published: February 2020

Dye-sensitized solar cells (DSSCs) have attracted extensive attention due to their potential low cost and high energy conversion efficiency, rendering them one of the most promising systems for solar-to-energy conversion. At the heart of these solar cells is a mesoporous TiO2 electrode, which not only provides a high surface area for accommodating the light-absorbing sensitizer but also serves as the stable conductor for photogenerated electrons. Although the solar-to-energy conversion efficiencies were found to be increased resulting from the increased light scattering, such kinds of photoanodes still suffered from low electron transport capability because of their particle stacking nature that forms large quantities of grain boundaries. In this work, we try to synthesis ellipsoid TiO2nanoparticles which can provide a fast way for electron transport and offer reduced trapping of photoinjected electrons during the path to back contact.

Ellipsoid TiO2 nanoparticles were synthesized by hydrothermal method. The morphology of the TiO2 nanoparticle was characterized with a scanning electron microscope. TiO2 paste was prepared as follows, ellipsoid TiO2 nanoparticles (1.850g), acetylacetone (0.20ml), Triton-X (30%, 1.0 ml) and polyethyleneglycol (0.185g) were mixed into acidic water (pH=0.7). The resulting TiO2 paste was printed by doctor blade method on fluorine-doped SnO2-coated (FTO) glass electrodes and sintered at 450 °C for 30 min. DSSCs were prepared by a conventional procedure.

According to SEM images of the ellipsoid TiO2 nanoparticles, particle length and width were 240 and 40 nm, respectively. The ellipsoid TiO2 powders were characterized by XRD, and determined their crystal structure is anatase. We have successfully fabricated ellipsoid TiO2 based DSSCs, and their conversion efficiency was 6.8% under AM 1.5 simulated full sunlight (100 mW cm−
2) illumination.
Pdm/Rgo with Enhanced Catalytic Activity for Electrooxidation of Formic Acid
Authors: Hu Chenyao
Published: February 2020

With the ever-increasing environmental problems and the up-coming depletion of fossil fuels, the direct formic acid fuel cells (DFAFCs) have aroused wide research interests in recent years[1-2]. There are several advantages of formic acid such as higher theoretical open circuit potential, lower crossover through the membrane, nontoxicity and uninflammability at room temperature, thus the DFAFCs are thought to be the one of the most promising power sources for portable electronic devices [3]. However, for commercial application, one of the essential issues is the design of effective and low cost anode catalysts for DFAFCs. Pd-based catalyst seems to be the best candidate for its lower cost and excellent catalytic activity toward formic acid electro-oxidation compared to Pt-based catalysts [4-5]. However, the stability of Pd is not satisfactory and its activity needs further improvement for commercialization.

In this work, PdM (M = Ni, Co, Ce, Cr, Ir) catalysts dispersed on reduced graphite oxide (RGO) were prepared by a simple hydrogen reduction procedure. The electrochemical measurements reveal that the PdIr catalysts have the best catalytic activity and stability for formic acid electrooxidation.

Reference

[1] Yoon, B. et al., J. Am. Chem. Soc., 127(49), 17174 (2005)

[2] Maiyalagan, T. et al., J. Power Sources, 211, 147 (2012)

[3] Huang, H.et al., J. Mater. Chem., 22(42), 22533 (2012)

[4] Morgan, R. D. et al., J. Phys. Chem. C, 115(39), 19413 (2011)

[5] Zhao, H. et al., Chem. Comm. 47, 2014 (2011)
Regeneration of Enzymatic Layer on Layer-By-Layer Assembled Biosensor Interfaces
Authors: Zhang Yuanyuan , Arugula Mary , Simonian Aleksandr
Published: February 2020

Previously, we reported an approach employing layer-by-layer (LbL) assembly of bio-functionalized multi-walled carbon nanotubes (MWCNT) on glassy carbon electrode for electrochemical detection of pesticides. In this study, to have a better understanding of self-assembled layers, surface morphology and element composition were characterized with Atomic Force Microscopy (AFM) and Scanning Electron Microscopy coupled with Energy-dispersive X-ray Spectroscopy (SEM/EDS). To further manipulate the versatile layer-by-layer assembly process, the possibility to regenerate the enzymatic layer in the layer-by-layer assembled bio-functionalized MWCNT Interfaces was investigated. Different approaches including direct chemical treatment, such as acid/alkali with different pH value, as well as inserting intermediate layer, such as conductive polymer PEDOT/NaPSS were explored. Such a strategy to achieve controllable assembly/disassembly of the layers is of great significance to enhance the biosensing system for long-term utility and/or multi-enzyme detection.
Development in Phosphor Glass Ceramics Composites
Authors: Chung Yuan-Run , Wu Fan-Bean , Chang Chih-Kun , Liao Jin-Hong
Published: February 2020

Glass ceramics containing phosphor, GCP, has become an advanced material in high power LED lighting application recently due to its superior optical and thermal performance and elongated lifetime. Glass systems which have lower characteristic temperatures , glass transition temperature(Tg) and glass softening point(Td)…, as well as excellent mechanical strength and chemical stability, are proposed in microelectronics technology, infrared laser technology and sealing of materials. Borosilicate glass systems exhibit lower characteristic temperatures and quality optical properties. By controlling functional elements, further enhancement in thermal, mechanical, and optical properties can deduced. In this study, the YAG phosphor powders embed into designed glasses under controlled atmosphere to from glass ceramics phosphor composites. The thermal, optical properties and structure of borosilicate glass host are discussed. Heat treatment which affects the YAG phosphor incorporation into the glass is also considered. The glass transition temperatures(Tg) and softening points(Td) are 447~483oC, and 476~524oC respectively. A high refractive index of 1.85~1.94 can be reached. The results show that the developed borosilicate glass hosts are suitable for GCP matrix to contain phosphor powders. The YAG phosphor powders are well contained and dispersed in the glasses.

Key words: LED, Glass ceramics phosphor composites(GCPC), Low characteristic temperature, Heat treatment
ZnO Gate Based Mosfets for Sensor Applications
Authors: Saikumar Ashwin Kumar , Skaria Giji , Sundaram Kalpathy B
Published: February 2020

In recent years, studies on zinc oxide (ZnO) films have drawn considerable interest because of their good electrical and optical properties, in combination with their wide bandgap, abundance in nature, and absence of toxicity. Owing to its varied physical properties such as electro-optical, acousto-optical, piezoelectrical and luminescence characteristics make ZnO as one of the most obvious choices for sensor applications [1].

Monitoring and control of the environment is very crucial part everywhere ranging from small scale laboratories to the most advanced industrial facilities. The interface that operates between the system and its surroundings and enables us to act accordingly is called as a sensor. Sensors are one of the most indispensable parts of today’s technology.

For the investigation of this, we fabricate a MOSFET with ZnO as its gate metal. We use a four level mask to fabricate the MOSFET, the first level for making the diffusion wells for source and drain. The second level to form the via holes for Aluminum deposition followed by the third level to shape the source and drain contact structures. Finally the fourth level mask to deposit ZnO gate metal. The ZnO gate metal was deposited by sputtering process. The electrical characteristic analysis was performed on the fabricated MOSFETs. We investigate the usage of these MOSFETs for various sensor applications which include but not restricted to gas and UV sensor applications.

REFERENCES

[1] P.P.Sahay, Journal of Material Sciences 40 (2005) 4383-4385

[2] Yongki Min, “Properties and Sensor Performance of Zinc Oxide Thin Films”, Massachusetts Institute of Technology, September 2003

[3] Eujune Lee, Dong-Il Moon, Ji-Hwan Yang, Keong Su Lim, and Yang-Kyu Choi, “Transparent Zinc Oxide Gate Metal–Oxide–Semiconductor Field-Effect Transistor for High-Responsivity Photodetector” IEEE Electron Devices Letters, Vol 30, No.5, May 2009
Understanding Electrodeposition Instabilities
Authors: Wang Chun-Chieh , Ziegler Kirk J , Narayanan Ranga
Published: February 2020

Electrodeposition is a common process via which metal ions are reduced at a cathode as a thin film. However, under certain conditions the deposited film on the cathode exhibits a unique interfacial pattern that is dependent on the applied voltage, the concentration, and the distance between electrodes. Although these morphological instabilities have been observed in the past, it still remains difficult to predict the formation and dimensions of these interfacial patterns. In an electrolytic cell, the reduction runs faster than oxidation. This is apparent when there is a small crest, as a disturbance, on the surface of cathode or a small trough on the surface of anode. These disturbances alter the rate and uniformity of metal deposition and initiate the growth of an interfacial pattern. Here we develop a model that describes the electrodeposition instabilities that lead to interfacial patterns. Transport and kinetic reactions described by Butler-Volmer equations are used to calculate and predict the electric current and growth characteristics of the film. A Cu-Cu electrodeposition system is then investigated to observe the instabilities. The pattern on the cathode is observed with or without the presence of disturbances on the anode. The roughness, periodicity, and thickness of the pattern can also be correlated to specific operating conditions.
Zinc Nucleation and Growth in Secondary Alkaline Batteries
Authors: Desai Divyaraj , Banerjee Sanjoy
Published: February 2020

Zinc morphology strongly affects the performance of secondary alkaline batteries. The formation of mossy and dendritic structures is detrimental to anode performance and cycle life. The initial stages of zinc deposition on carbon structures are investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and electron-diffraction. Mossy zinc is formed by the aggregation of zinc clusters in a nucleation-controlled process. Dendritic zinc is formed by the unstable growth of zinc along preferred growth axes. An attempt is made to develop a free-energy based phase-field model of electrodeposition to simulate dendritic growth. Preliminary results using a solidification model are able to qualitatively simulate zinc deposition. Understanding the nucleation and growth processes is key to developing innovations to improve battery performance in alkaline zinc anodes.
Electrochemical Synthesis of Titanium Dioxide Nanostructures
Authors: Jayaraman Shrisudersan
Published: February 2020

Metal and metal oxide nanostructures immobilized on substrates are extensively studied material systems due to their immense practical and industrial applications such as catalysis and photocatalysis, photovoltaics, electrochromics, energy storage, sensors, functional coatings and biomedical applications [1-6]. Nanomaterials possess unique properties that are not observed in bulk material. In addition to very high surface area – to – volume ratios, they exhibit quantum chemical and quantum mechanical effects which open doors for novel applications that are otherwise impossible with bulk material [7]. A major problem with nanotechnology is the difficulty associated with manufacture of the nanomaterial economically, as a result of which only a few nanotechnology based applications have been commercially realized [8]. In this talk, a simple, low-cost electrochemical process for synthesis of a titanium oxide nanostructures will be reported. This process works at ambient conditions and uses low electrochemical potentials (≤ 5V) and low current densities (few 10’s of A•m-2), which results in use of less energy compared to conventional synthesis processes. As it is an electrochemical process, it also highly scalable with a good degree of reproducibility and controllability even on a manufacturing scale. The size and structure of the nanostructures can be tweaked using process parameters such as voltage, electrode polarity, electrolyte composition and temperature. This methodology opens up possibilities of synthesizing a wide spectrum of nanomaterials at ambient conditions and more importantly, at low cost to enable more nanomaterial-based applications.

References

1. Chen, X. and S.S. Mao, Titanium dioxide nanomaterials: Synthesis, properties, modifications, and applications. Chemical Reviews, 2007. 107(7): p. 2891-2959.

2. Guo, S.J. and E.K. Wang, Noble metal nanomaterials: Controllable synthesis and application in fuel cells and analytical sensors. Nano Today, 2011. 6(3): p. 240-264.

3. Seil, J.T. and T.J. Webster, Antimicrobial applications of nanotechnology: methods and literature. International Journal of Nanomedicine, 2012. 7: p. 2767-2781.

4. Tian, Y.F., S.R. Bakaul, and T. Wu, Oxide nanowires for spintronics: materials and devices. Nanoscale, 2012. 4(5): p. 1529-1540.

5. Zhao, X., et al., The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices. Nanoscale, 2011. 3(3): p. 839-855.

6. Duncan, T.V., Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors. Journal of Colloid and Interface Science, 2011. 363(1): p. 1-24.

7. Haruta, M., Size- and support-dependency in the catalysis of gold. Catalysis Today, 1997. 36(1): p. 153-166.

8. Kang, H.-Y., A Review of the Emerging Nanotechnology Industry: Materials, Fabrications, and Applications, 2010, Department of Toxic Substances Control Pollution Prevention and Green Technology.
The Influence of the Interaction Between Silicon and Hydroxyl Radicals before the Copper Electrodeposition. Activity Changes of the Silicon Surface
Authors: Muñoz Eduardo Carlo , Navarrete Emilio Alonso , Heyser Cristopher Alejandro , Henríquez Rodrigo Gonzalo , Schrebler Ricardo Silvio , Córdova Ricardo Alejandro
Published: February 2020

Several studies have emerged in an attempt to explain the aging process which occurs in the human body, where free radicals (FR) are species involved in these alterations. Considering this subject, there is a great interest in being able to detect, quantify and control the amount of FR that human body produces at certain periods, and especially the hydroxyl radical (OH) [i, ii].

In this study we examined the changes in the surface activity of n-Si after its exposition to a solution containing hydroxyl radicals. Changes in the surface activity caused by the interaction between silicon and OH radicals were characterized by analyzing the nucleation and growth mechanism (NGM) of copper on silicon electrodes. For this aim, we studied the copper deposition on: i) n-Si without exposure to hydroxyl radicals and ii) n-Si exposes at different periods of time to hydroxyl radical. It was observed a change in the copper NGM on n-Si, from 3D progressive nucleation diffusion-controlled growth (PN3DDIFF), for the system without exposure to the OH radical, toward 3D instantaneous nucleation diffusion-controlled growth (IN3DDIFF), when the semiconductor substrate was exposed to the OH radicals. In both cases analysis by the Atomic Force Microscopy (AFM) technique was performed confirming these mechanisms.

[i] Tomasz Rapecki, Anna M. Nowicka, Mikolaj Donten, Fritz Scholz, Zbigniew Stojek, Electrochem. Commun. 12, (2010), 1531-1534.

[ii] Anna Maria Nowicka, Ulrich Hasse, Mikolaj Donten, Michael Hermes, Zbigniew Jan Stojek, Fritz Scholz, J Solid State Electrochem., 15, (2011), 2141–2147.
Anti-Biofouling Nanoporous Gold Electrodes for Biochemical Sensor Applications
Authors: Saraf Shashank , Neal Craig J. , Kumar Amit , Das Soumen , Park Sanghoon , Seal Sudipta , Cho Hyoung J.
Published: February 2020

Within the scope of traumatic brain injury research, the implications of radical oxygen species (ROS) have been a primary interest. The ability to monitor these species cannot only provide a window into the progression of resultant pathology but also assist in therapeutic intervention by detailing the associated ROS insult experienced by the afflicted patient. Formation of protein plaques and aggregates is also associated with traumatic brain injury. These can form a passivation layer on the sensor’s surface leading to bio-fouling, thus limiting or even nullifying the sensitivity. The nano-scale ‘roughness’ of our nanoporous gold (NPG) electrode augments the effective surface area for conduction and is found resistant to bio-fouling. Likely, the proteins are excluded from entering pores due to the constriction of pore sizes, which significantly reduces the sites for protein deposition. NPG and plain gold electrode (PG) were tested in bovine serum albumin and beta amyloid to assess relative biofouling resistivity. The cyclic voltammetry (CV) from BSA incubation shows promise for NPG while PG experiences rapid surface saturation and loss of sensitivity (fig.1). CV was also performed in phosphate buffered saline (PBS) with a well-known redox couple of potassium hexacyanoferrate (HCF). Comparison between the CV measures for each electrode shows the increased conductivity for NPG. The results implicate the dual benefits of using the NPG for electrodes for increased sensitivity and resistance to bio-fouling.
Sensor Technologies and Applications for Smart Roads and Smart Buildings
Authors: Grace Roger Henry
Published: February 2020

Smart System Integration (SSI) principles currently have widespread applications in the societal infrastructure sector addressing critical needs of safety, quality of environment and energy conservation applications. This is easy to understand since SSI approaches provide a small and cost-effective approach to monitoring and controlling the many environments surrounding us vis-à-vis the utilization of broad selection of sensors in their front end. In addition to these front end sensors, Smart Systems also include a diverse array of other functions including signal conditioning circuits (e.g. ASICs with embedded microcontrollers), energy sources, and communication back ends….either wired or wireless and all assembled and packaged. The sensors, when linked together to form a network are frequently referred to as Wireless Autonomous Sensor Networks (WASNs).

Major opportunities for these Smart System Integration solutions currently exist in structural bridge monitoring. In the US alone, the American Society of Civil Engineers (ASCE) has recently reported that there are over 583,000 bridges and of these over 25% are structurally deficient or functionally obsolete. ASCE also reports that of the 76,926 dams that exist in the US of which 1,819 have high hazard potential. Various organizations including the University of Michigan and the University of Illinois have been developing solutions to monitor these and other civil engineering structures including dams, buildings, levees and pipelines.

Additionally, infrastructure monitoring has expansive applications in building monitoring from a structural, energy management, security and quality of environment perspectives. The US census reported that there are over 160 million households in the US and it is reported that there are 1.7 billion households internationally. Most provide heating (and many also provide cooling) to their inhabitants. This is in addition to commercial buildings. WASNs are critical to the efficient monitoring and control of these systems especially in these times of minimizing the systems’ thermal footprint and minimizing energy consumption.

This presentation will address several of the systems currently in use and/or under development at commercial organizations and research facilities in the US to be able to monitor and control these infrastructure applications. Applications include bridge monitoring, smart roads (traffic control and parking) and smart buildings. We will present functional analysis of the systems, address specific elements of the systems (with a focus on sensors) and provide measured results to establish the feasibility and efficacy of such approaches.
Commercialization of Technology: Examples in Chemical Sensors
Authors: Stetter Joseph R , Carter Michael T , Stetter Edward F
Published: February 2020

It takes a special and concerted effort to get technology successfully into the marketplace. Commercialization of technology requires a multidisciplinary and interdisciplinary approach. Not only is the science and engineering important from basic understanding to manufacturing design, but also market and sales efforts have to be integrated with the team’s management, financing, and organizational skills. You can start this conversation anywhere you wish, but knowledge of the customer need you are solving is critical and this requires serious research to understand the details well enough to design a successful product. Figure 1 illustrates the central position of technology in solving the customer problems, but highlights the overall goal of knowing the customer need. How your product will fill this need is of primary importance in getting to realize the commercial potential of any technology. It is not so important for your technology to solve many needs or be placed in many markets: just one substantive solution to one important need is required for success. If you attempt to write a detailed engineering description of the hardware and software needed to solve your application, you quickly find out what information you still need. The way to resolve your questions is to talk to the marketing group and, often better, to talk to the customer and convince yourself and the rest of the team that the specific product you describe works. While Figure 1 illustrates a nanosensor example that can start a dialog with different markets like safety, process control, medical or environmental and can be useful for solving problems therein, it also show some of the complexities of commercialization. That is to say, there are myriad questions to answer to design a product that will be successful in even one of the above applications.

There are of course many factors to consider besides technology and market when bridging the gap from a technical idea to successful monetization of the technology. Figure 2 illustrates seven different areas that may be important in a startup venture. In the USA, there are a myriad of ways that each of these elements play out in the commercialization scenario. For example, it is sometimes possible to get patent protection and then sell the invention and then not get involved in many of the other details of commercialization like finding distribution for your product or service idea. In the end, realizing the connection of your idea and technological developments can be very rewarding intellectually, personally, and financially.
Experimental and Theoretical Investigations on the Corrosion Inhibition of Lumazine over Mild Steel in 1M HCl
Authors: Meitei Oinam Romesh , Wilson Paul
Published: February 2020

The corrosion inhibition efficiencies and adsorption characteristics of Lumazine over mild steel in 1 M HCl were investigated using electrochemical and theoretical methods. The Gravimetric and electrochemical methods used in the present investigation includes weight loss, Tafel polarisation and Electrochemical Impedance Spectroscopy methods respectively. The adsorption studies carried out using this inhibitor adhere to Langmuir adsorption isotherm. In addition, the equilibrium constant and free energy of adsorption were calculated for the inhibitors on mild steel in 1 M HCl. Density Functional Theory using B3LYP functional was utilised to calculate the quantum chemical parameters of the inhibitors which were used to determine their contribution to inhibition of corrosion. HOMO LUMO, mulliken atomic charge, condensed fukui functions, local softness, relative nucleophilicity and relative electrophilicity were analysed to study the possible site of the inhibitor molecule at the metal surface. The quantitative structure-activity relationship (QSAR) has been established to correlate the experimental inhibition efficiencies and the quantum chemical parameters to model mathematical equations describing theoretical inhibition efficiencies.
The Role of Surface Adhering Organic Substances on Metal Dissolution and Repassivation during Cyclic Deformation of Ti-6Al-4V Alloy
Authors: Doi Kotaro , Miyabe Sayaka , Fujimoto Shinji
Published: February 2020

In the body environment, passive film is broken by cyclic stress induced by the motion of body, then newly created surface is exposed to the body fluid which includes Cl- ions and organic substances. Consequently, corrosion fatigue occurs. However, the role of the organic substances such as proteins and cells on the passivity breakdown and repassivation has been little clarified. In this work, therefore, we examined the passivity breakdown and repassivation behavior of Ti-6Al-4V alloy with cyclic deformation in simulated body fluid including proteins and cells. The samples of Ti-6Al-4V alloy for tensile test with a gauge size of 8×4×1 mm3 were mirror-finished and sterilized in an autoclave at 121 °C for 900 s. Then samples were immersed in a-MEM+10 % FBS which is commonly used for cell culturing. The immersion period was 1day or 1 week ((1) 1 day immersed, (2) 1 week immersed). In order to examine the role of cells adhering on the samples, osteoblast-like cells (MC3T3-E1) were cultured on some samples for 1 week ((3) 1week immersed with cells). Samples without immersion ((4) in the air) were examined for comparison. Then a cyclic stress which was modulated as sinusoidal wave was applied to the samples. The stress ratio was 0.1 and the maximum stress was 400~800 MPa, which did not exceed the elastic region of Ti-6Al-4V alloy. The stress frequency was 10 Hz. During the test, the samples were accommodated in the electrochemical cell filled with a-MEM + 10 % FBS kept at 37 °C under atmosphere controlled as 5 % CO2, 20 % O2 and 75 % N2 (1 day immersed, 1 week immersed and 1 week immersed with cells) or in the air kept at 28 °C (in the air) . The transients of strain, stress and corrosion potential were recorded with time. Figure shows the fatigue life cycles of samples under the four conditions. The fatigue life cycles of the samples deformed in the solution were shorter than the samples deformed in the air, because passivity breakdown and metal dissolution enhanced the growth of fatigue crack. Therefore, the fatigue lives of 1 week immersed and 1 week immersed with cells were shorter than that of 1 day immersed. This result indicates that the proteins and cells decrease the fatigue life of Ti-6Al-4V alloy. When the passive films are broken by cyclic deformation, the corrosion potential shifts less noble and when the area of newly created surface decreases by reapassivation, the corrosion potential shifts noble. The corrosion potential of 1 day immersed shifted less noble at only first cycle and then shifted monotonously noble direction. On the other hand, for 1 week immersed and 1 week immersed with cells, the corrosion potential continued to shift less noble until about 1000th cycle and then shifted noble. These results indicate that proteins and cells adhered on the sample surface hinder the repassivation. It is considered that the hindrance to repassivation by protein and cells led the less fatigue life of Ti-6Al-4V alloy.