bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased Corrosion Resistance of Zinc Magnesium Aluminum Galvanised Coating through Germanium Additions
Authors: Mehraban Shahin
Published: February 2020

Improvements in the corrosion resistance of hot dipped galvanised steel coatings have been brought about over the last 20 years through binary alloy additions such as Al and more recently ternary Mg additions [1], [2], to further improve corrosion resistance quaternary additions were made to a commercially produced Zn-Mg-Al (ZMA) alloy.

Corrosion performance of the ZMA alloy coating was shown to improve through the addition of a quaternary element, Germanium. This was added in the molten state and the alloy mixture was rapidly cooled to mimic the cooling rate of a galvanised steel production line.

The increased corrosion resistance can be attributed to microstructural changes in the alloy composition due to Ge addition while in the molten state. The proportion of the most active MgZn2 phase which has been shown to initiate the corrosion reaction in a ZMA alloy [3] was reduced thorough the formation of Mg2Ge crystals. The formation of crystal structures within the alloy also increased the heterogeneous nucleation of the primary zinc phase.

The phases present of the experimental alloy were identified using EDX analysis and from this a relationship was determined between the observed microstructural phases and the corrosion rates for varying Ge addition.

The Scanning Vibrating Electrode Technique (SVET) was used to measure the rate of corrosion, anode life and zinc loss of the alloy samples. The results showed a zinc loss of around 50% when compared to standard ZMA alloy without Ge addition.

 

[1]        D. A. Worsley, H. N. McMurray, J. H. Sullivan, and I. P. Williams, “Quantitative Assessment of Localized Corrosion Occurring on Galvanized Steel Samples Using the Scanning Vibrating Electrode Technique,” Corrosion, vol. 60, no. 5, pp. 437–447, May 2004.

[2]        A. R. Marder, “The metallurgy of zinc-coated steel,” Prog. Mater. Sci., vol. 45, no. 3, pp. 191–271, Jun. 2000.

[3]      J. Sullivan, S. Mehraban, and J. Elvins, “In situ monitoring of the microstructural corrosion mechanisms of zinc–magnesium–aluminium alloys using time lapse microscopy,” Corrosion Science, vol. 53, no. 6, pp. 2208- 2215, Jun. 2011.
Hybrid Silver Mesh Electrode for ITO-Free Flexible Polymer Solar Cells
Authors: Kim Wanjung , Park Jong Hyeok
Published: February 2020

Herein, we demonstrate a tailored poly(3,4-ethylenedioxythiophene) PEDOT polymer-coated silver (Ag) mesh electrode on a flexible polyethylene terephthalate (PET) substrate. By introducing this highly conductive polymer, the existing problems of Ag mesh-type transparent conductive electrodes, such as high pitch, roughness, current inhomogeneity and adhesion problems between Ag mesh grid and PEDOT polymer or PET substrate, were successfully solved, resulting in excellent electron spreading from the discrete Ag mesh onto the entire surface without sacrificing sheet conductivity and optical transparency. Based on this hybrid anode, we demonstrate highly efficient flexible polymer solar cells (PSCs) with a high fill factor of 67.11 %, resulting in a power conversion efficiency (PCE) of 6.9 % based on a PTB7:PC71BM bulk heterojunction device. Furthermore, the PSC device with the Ag mesh electrode also exhibits good mechanical bending stability, as indicated by a 70% retention of the initial PCE after 500 bending cycles compared with the PSC device with a PET/indium tin oxide (ITO) electrode, which retained 0% of the initial PCE after 300 bending cycles.
Opto-Electronic Properties of Hybrid Perovskites
Authors: Mohite Aditya , Nie Wanyi , Tsai Hsinhan , Blancon Jean-Christophe , Tretiak Sergei , Gupta Gautam
Published: February 2020

The photovoltaic efficiency utilizing hybrid perovskites as an absorber layer have reached 22% and offers extraordinary potential for clean sustainable energy technologies and also for low-cost optoelectronic devices. In spite of the unprecedented progress, there still exists tremendous variability in the structural and physical properties of these hybrid perovskite based thin-films across the globe. Crystallinity, defect density and impurities are in general determining factors for these physical properties, which are also highly dependent on the materials formation processes. In addition to this, the stability and reliability of perovskite based devices remains open questions and perhaps will determine the fate of this remarkable technology in the longer run.

In this talk, I will describe our recently discovered hot-casting approach for thin-film crystal growth as a general strategy for growing highly crystalline, bulk homogenous pin-hole free thin-films of both 3D and layered 2D organometallic perovskites that yield reproducible and stable high efficiency devices and allow access to the intrinsic photo-physical properties. These results are briefly described below.

Photovoltaic devices fabricated using 3D hybrid perovskites show hysteresis-free response, with high degree of reproducibility, with an average efficiency of planar devices approaching ~20%. Photo-physical, electrical characterization and theoretical modeling attribute the improved performance to reduced bulk defects and improved charge-carrier mobility in large-grain devices. Furthermore, our most recent efforts on understanding and controlling photo-degradation in these systems demonstrate that the large grain-size perovskite thin-films are not limited by detrimental effects such as ion migration or defect assisted trapping generally reported in perovskite thin-film devices allowing us to probe intrinsic photo-physical processes that lead to the degradation of PCE in perovskite solar cells and control the light-induced degradation in these materials.
Vapor-Assisted Efficient Perovskite Solar Cells Fully Fabricated in Open Air
Authors: Yin Jun , Li Jing , Zheng Nanfeng
Published: February 2020

Organometal trihalide perovskite based solar cells (PSCs) have been developed intensively in recent years due to the attractive applications in the next generation solar cells with low cost and high power conversion efficiency (PCE).1, 2 Currently, the solution based spin-coating technique is the mostly used preparing method for perovskite films.3, 4 However, limited film scale, low material usage and strict film growth condition always present in the spin-coating based fabrication processes. Like other thin-film solar cells, vapor-depositing method also can be used in the PSCs' fabrication to improve the film quality and interface uniformity, where the growth process can be much precisely controlled under vapor mode transportation. 5

In this work, vapor assisted deposition of organometal trihalide perovskite films in open air has been developed to fabricate efficient and stable perovskite solar cells. It has been found that the film quality, as well as the device’s performances, are strongly dependent on the reaction time and growth temperature, while not sensitive to the environment humidity. With the optimized vapor-assisted growth parameters, an average PCE of 16.40% and the maximum of 18.14% have been achieved on the planar type of PSCs. Detailed investigations demonstrated that the improved film quality and interface uniformity within cells by this unique vapor-assisted method are responsible for the enhanced photovoltaic performances and good stability either in air or under light irradiation.

References

1. M. A. Green, A. Ho-Baillie and H. J. Snaith, Nature Photon., 2014, 8, 506-514.

2. M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami and H. J. Snaith, Science, 2012, 338, 643-647.

3. H. S. Jung and N. G. Park, Small, 2015, 11, 10-25.

4. J.-H. Im, H.-S. Kim and N.-G. Park, APL Materials, 2014, 2, 081510.

5. M. Liu, M. B. Johnston and H. J. Snaith, Nature, 2013, 501, 395-398.
(Invited) X-Ray Crystallographical Studies on the Intermediates in the Solution Fabrication Process for Highly Efficient Perovskite Solar Cells
Authors: Wakamiya Atsushi
Published: February 2020

Perovskite solar cells represent cost-effective next generation printable photovoltaics. In a relatively short period, power conversion efficiencies (PCEs) in such cells have been substantially increased, mainly due to improvements of the fabrication protocols for the perovskite layer as well as the development of new materials for buffer layers. In this presentation, the recent progress and perspective on this promising new type of photovoltaics are introduced, including our approaches toward development of high PCE cells in terms of materials science.

Regarding the molecular design for organic semiconductors that are used as p-type buffer layer in perovskite solar cells, we have recently reported that the use of partially oxygen-bridged triarylamines as quasiplanar scaffolds for charge-transporting materials facilitates delocalized pi-conjugation and on-top pi-stacking in the solid state, which ensures high carrier mobilities in the pi-stacking direction. In this study, we designed and synthesized the two-dimensionally expanded system (HND-Azulene) with a sheet-shaped structure, in which four oxygen-bridged triarylamines that contain alkoxy groups to enhance the solubility were attached to an azulene core skeleton. Using HND-Azuleneas a HTM in perovskite solar cells led to high PCEs (16.5%), even compared to Spiro-OMeTAD. By comparison with reference compounds, we were able to determine the key factors that improve the efficiency of HTMs in perovskite solar cells, which ultimately led to an increase in cell performance.

Moreover, we focused on the fabrication of perovskite layer by one-step solution method with solvent engineering, and studied on the mechanism in terms of the elucidation of the key intermediates formed during the process and the roll of solvents. Based on these results, we could develop and optimize the fabrication protocol to obtain dense and planar perovskite layer with 500 nm thickness. Using this protocol, we achieved to prepare the perovskite solar cells with high PCEs over 20%. The details of our recent progress will also be discussed in this presentation.
Investigation of Dynamics of Perovskites using Chemically, Spatially and Temporally Resolved 2D Mapping
Authors: Namkoong Gon , Jeong Hyeon Jun , Mamun M A , Byun Hyeryung , Demuth Derek , Jeong Mun Seok , Baumgart Helmut
Published: February 2020

Currently, there is an ongoing strong discussion regarding the nature of organometallic CH3NH3PbI3-xClx perovskites for solar cells. In this work, perovskites have been investigated using chemically, spatially, and temporally resolved measurements. To investigate the carrier dynamics of perovskites, perovskite (CH3NH3PbI3-xClx) films were prepared using hot casting technique in which perovskite (CH3NH3PbI3-xClx) solution was prepared by dissolving equimolar ratios of lead iodide (PbI2, Sigma-Aldrich, 99%) and methylamine hydrochloride (MACl, Sigma-Aldrich) in N, N-dimethylformamide (DMF, Sigma-Aldrich, anhydrous, 99.8%) in 11% concentration. A lower hot-casting temperature (100 °C) resulted in smaller grain size, with typical grain sizes of 1~2µm. Hot-casting temperatures higher than 100 °C produced perovskite samples with larger grains of ~ more than tens of micrometers, which was confirmed by high-resolution scanning electron microscopy (SEM). The PL intensity and peak-position mapping image of submicron-scale were performed using confocal micro-spectroscopy. In-plane spatial resolution of ~380nm was indicated by an objective lens with numerical aperture of 0.7 and a solid-state laser with 405nm wavelength for the excitation. The signal collected by the objective lens was detected by a thermoelectrically cooled CCD detector. For the analysis of time resolved PL (TRPL), multifunctional confocal microscopy including a time-correlated single photon counting (TCSPC) system was employed. In addition, 2-D energy-dispersive X-ray (EDS) measurement was performed to elucidate the distribution of chemistries for the surface of perovskites, which were correlated to spatially and temporally resolved PL. Particularly, the carrier dynamics between grain interiors and grain boundaries were systematically investigated.
Fabrication of Non-Vacuum Sns Thin Film for Solar Cell Application
Authors: Eo Young Joo
Published: February 2020

Tin mono-sulfide (SnS) thin film has been investigated as a photovoltaic absorber material due to not only a high optical absorption coefficient but also non-toxicity and earth abundance. However, the highest photovoltaic conversion efficiency is as low as 4.4%. One of the reasons for the low efficiency is considered to be the poor quality of the SnS layer, such as the formation of secondary phases and a high grain boundary density. Thus, many research groups have dedicated their own effort to obtaining a high quality of SnS thin film.

Nano-particle based approach can be one of the suitable fabrication methods of SnS thin films because the thin film can be prepared by a simple coating process using the nano-particle based ink, and the subsequent thermal annealing. The thermal annealing can transform the nano-particle precursors into the thin film and promote the grain growth. Moreover, it can affect the micro-crystalline structure of the thin film. Thus, we can control the physical properties of the SnS thin films by the modification of the thermal annealing condition.

In this study, we focused on the effect of the thermal annealing condition on the properties of the SnS thin films. We have found that the crystallinity and band gap (Eg) of thin film are highly dependent on the thermal annealing temperature. The partial pressure of hydrogen sulfide (H2S) gas during the thermal annealing affects the valence of Sn atom and the composition of the thin film. Finally, we demonstrate a SnS thin film solar cell and characterize its photovoltaic performance.
Transparent Conducting Oxide Layer By Thermal Evaporation for Cu(In,Ga)Se2 Solar Cell with Chemical Bath Deposited-ZnS Buffer Layer
Authors: Lee Woo-Jung , Cho Dae-Hyung , Wi Jae-Hyung , Han Won Seok , Chung Yong-Duck , Kim Yi Do , Choi Myung-Woon , Choi Jin Chul
Published: February 2020

Chemical-bath-deposited (CBD) ZnS buffer layer is being steadily studied in Cu(In,Ga)Se2 (CIGS) thin-film solar cell because of their beneficial properties, for examples, good transparency with large direct bandgap, less toxicity and cost effectiveness. CBD-ZnS buffer layer, however, is easily affected during subsequent sputtering process for window layer and the conversion efficiency decreases with sputtering power. The decrease of efficiency in CBD-ZnS/CIGS thin-film solar cells is known to be related to plasma damage originated from high energy negative oxygen ions or neutral particles at the interface. In typical CIGS solar cell, ITO/i-ZnO bilayer deposited by sputtering process has been used as a conventional window layer and then interface properties between window layer and buffer is considered as an important key to determine the cell efficiency.

In this paper, to know actual effects of interface property between window layer and buffer on cell performance, we applied the two types of window layer and fabricated CIGS solar cell with CBD-ZnS buffer; (i) typical structure of ITO/i-ZnO/CBD-ZnS/CIGS, and (ii) thermally grown-IZO/i-ZnO/CBD-ZnS/CIGS. To completely exclude plasma damage from sputtering, two types of CIGS solar cell were also fabricated without i-ZnO layer. As a result, the cell performance interestingly shows the opposite tendency depending on presence or absence of i-ZnO layer; cell efficiency with IZO layer is higher than that with ITO layer in the presence of i-ZnO layer, while the former is lower than the latter in the absence of i-ZnO layer. To understand these phenomena, interfacial properties between window and buffer layer are characterized by various analysis tools.
Eco-Friendly Orgnaic-Inorganic Hybrid Perovskite Solar Cells
Authors: Im Sang Hyuk , Heo Jin Hyuck
Published: February 2020

Organic-inorganic hybrid perovskite materials have prominent properties such as high absorptivity by direct bandgap, long charge carriers' diffusion lenght by ionic crystal characteristics, high open circuit voltage by large dielectric constant, and solution processibility so that their power conversion efficiency of solar cells reached over 22% at 1 Sun condition. However, to find applications in daily commodities the toxic Pb should be replaced to non-toxic metals. Here, we tried to replace the Pb to the non-toxic metals and checked their photovoltaic properties and stabilities.
(Invited) Parallelized Nano-Pillar Perovskites for Semitransparent Solar Cells Using Anodized Aluminum Oxide Scaffold
Authors: Kwon Hyeok-Chan , Lee Hongseuk , Lee Eunsong , Ma Sunihl Ma , Moon Jooho
Published: February 2020

Semitransparent solar cells have attracted significant attention for practical applications, such as windows in buildings and automobiles. Here, we report semitransparent, highly efficient, one-dimensionally nano-structured perovskite solar cells employing anodized aluminium oxide (AAO) as a scaffold layer. The parallel nano-pillars in the perovskite layer enable construction of haze-free semitransparent devices without any hysteresis behaviour. By controlling the pore size in the AAO, the volume occupied by the perovskite layer can be precisely varied, and the colour neutrality of the resulting devices can be achieved. With the incorporation of a transparent cathodic electrode (indium tin oxide, ITO) with a buffer layer (MoOx), a highly efficient semitransparent nano-pillared perovskite solar cell is achievable with a power-conversion efficiency of 9.6% (7.5%) and a whole device average visible light transmittance of 29.7% (38.2%). To determine the role of the scaffold layer in improving the photo-electrical properties of the cell, impedance spectroscopy analyses were performed, revealing that the AAO-structured perovskite layer suppresses internal ion diffusion and enables critical improvements in long-term stability under continuous illumination.
(Invited) Intramolecular Exchanging Crystallization for Formamidinium Lead Iodide Perovskite Solar Cells
Authors: Noh Jun Hong
Published: February 2020

Inorganic-organic hybrid solar cells using perovskite metal-halides such as methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3) have great potential for future photovoltaic systems in terms of high efficiency and low-cost. MAPbI3 had opened the field of perovskite solar cells, but FAPbI3 is recently attracting considerable attention for high efficiency exceeding 20 % and superior durability of the perovskite solar cell. However, FAPbI3 had been limited to utilize as a photovoltaic material due to its polymorph of non-perovskite phase and difficulty to make high quality film in solution process. Recently we reported that perovskite phase of FAPbI3 can be stabilized by compositional engineering of FAPbI3 with incorporation of MAPbBr3. In addition, we showed that intramolecular exchanging process successfully offers a way to make high quality FAPbI3 based perovskite film using dimethyl sulfoxide (DMSO) as a mediator to control crystallization of perovskite. The exchange of FAI with DMSO in pre-deposited PbI2(DMSO) film leads to crystallize into perovskite film with small volume expansion, preferred crystallographic orientation, and large grains, yielding to high power conversion efficiency exceeding 20 %. In this talk, FAPbI3 based perovskite solar cells will be discussed in terms of the compositional engineering and intramolecular exchanging process.
Two-Dimensional Layered Perovskite Solar Cells with 12.5 % Efficiency and 2000 Hours Stability in Light and Humidity
Authors: Gupta Gautam , Tsai Hsinhan , Nie Wanyi , Blancon Jean-Christophe , Stoumpos Constantinos , Kanatzidis Mercouri , Mohite Aditya , Ajayan Pulickel M
Published: February 2020

Three-dimensional organic-inorganic perovskites have emerged as one of the most promising thin-film solar cell materials due to their remarkable photophysical properties that have led to power conversion efficiencies exceeding 22%, with the prospect of further improvements towards Shockley-Queisser limit for a single‐junction solar cell (~33.5%). Alongside efficiency, a critical factor for photovoltaics and other optoelectronic applications is environmental and photostability under operating conditions. In contrast to their 3D counterparts, Ruddlesden-Popper phases, layered two-dimensional (2D) perovskite films, have shown promising stability, but poor efficiency at only 4.73%. This is attributed to the inhibition of out-of-plane charge transport by organic cations, which act like insulating spacing layers between the conducting inorganic components. Here we overcome this fundamental issue in layered perovskites by producing near single-crystalline quality thin-films with a strongly preferential out-of-plane alignment of the inorganic perovskite component to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.5 % with no hysteresis, and devices that exhibit greatly improved stability in comparison to their 3D counterparts when subjected to aggressive stress tests of light, humidity and heat. Unencapsulated 2D perovskite devices retain over 70% of their efficiency for over 2000 hours under constant 1 Sun illumination, and exhibit greater tolerance to 65% relative humidity than 3D equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant 1 Sun illumination or humidity.
High Efficiency and Durable Flexible Photovoltaics: Dye-Sensitized and Perovskite Solar Cells
Authors: Ko Min Jae
Published: February 2020

There have been significant progresses in the dye-sensitized (DSSCs) and perovskite solar cells (PSCs). Further cost reduction in high-speed manufacturing can be accomplished by continuous roll-to-roll printing processes using a flexible plastic substrate. Lightweight and flexible plastic solar cells can be installed even on non-flat surface, which makes them a possible ubiquitous power source for mobile electronics. To fully utilize these kinds of advantages in DSSCs and PSCs, mechanical durability as well high efficiency should be guaranteed. In this talk, we will introduce several strategies to address these issues.
(Invited) Scaled Magnetic Tunnel Junctions for High-Density Nonvolatile Memories
Authors: Sugii Toshihiro , Yoshida Chikako , Noshiro Hideyuki , Yamazaki Youichi , Iba Yoshihisa
Published: February 2020

We report scaled magnetic tunnel junction (MTJ) for high-density nonvolatile cache memory. Under the same clock frequency, CPU performance can be improved by increasing its embedded cache memory capacity because the probability of cache misses decreases as cache memory capacity increases. Our motivation is to realize small magnetic tunnel junctions which enable high density embedded STT-MRAM cache. We have already proposed a unique fabrication technique which we call it as “shrink process” for reducing the size of a MTJ and realized MTJs with 20 nm in diameter [2014 Symposium on VLSI Technol. pp.212-213].

In this paper, in order to realize scaled MTJs with an MgO barrier, two major issues have to be solved. One is to realize a very thin barrier to keep moderate MTJ resistance from the point of a 1-transistor and 1-MTJ memory cell configuration. Another is to fabricate small MTJs without increasing their size variation.

 In this paper, in order to realize the thin MgO barrier, its leakage mechanism was studied precisely, and proposed its model and possible solutions which will leads to much reduced leakage current and enough write endurance.

 The shrink process for small MTJs was also investigated from the point of scalability without increasing MTJ size variation. After the MTJ etching, various plasma treatments were done. During this treatment, the sidewall surface of the MTJ was modified, which resulted in the small electrical MTJ size of around 20 nm. Proposed techniques are scalable and promising for sub-20 nm MTJ generations.

 This work was funded by ImPACT Program of Council for Science, Technology and Innovation.
Resistive Switching Effect in BiFeO3 Nano-Islands
Authors: Choi Taekjib
Published: February 2020

With a revolution in mobile devices and the increasing demand for higher data storage density, non-volatile memory technologies have rapidly developed. Among various non-volatile memories, resistive random access memory (ReRAM) based on metal oxide has been emerging as a promising alternative to flash memory due to its high speed, long retention, good endurance, low operating voltage, and high scalability. However, gaining a high memory performance and overcoming the scaling limitations would still impose a significant challenge and require nanoscale device structure, reliable resistive switching (RS) materials, and cost-effective device architectures. To realize high density resistive random access memory (ReRAM) compatible with cross-point stack structure, highly nonlinear bistable current-voltage (I-V) characteristics is necessary. Here, we report highly nonlinear bistable I-V characteristics in a BiFeO3 (BFO) nano-island arrays. We explored the local charge conduction and ferroelectric polarization in highly-oriented ferroelectric BFO nano-islands by using conductive atomic force microscopy and piezoresponse force microscopy. A mosaic nano-crystalline BFO nano-island grown on a Nb-doped SrTiO3 substrate, which has pinned downward polarization, exhibits both bipolar resistive switching with resistance ratio of 4,420 and nonlinear behavior with nonlinearity factor α of 1,100 in low resistance state. Such high resistance ratio and nonlinearity factor suggest that our BFO nano-islands can be extended to an N × N array of N = 3,740 corresponding to ~107 bits. Therefore, our BFO nano-island showing both high resistance ratio and nonlinearity factor offers a simple and promising building block of high density ReRAM.
TiO2 Based Conductive-Bridge-Random-Access-Memory
Authors: Kim Dong-Won , Song Myung-JIn , Kwon Ki-Hyun , Kim Hye-Jee , Jin Soo-Min , Kim Do-joon , Park Jea-Gun
Published: February 2020

NAND flash is currently facing physical limitations for 10nm technology because as NAND flash cells have been getting smaller, cell to cell interference significantly increase. To overcome these challenge, new memories have been developed. Conductive Bridge Random Access Memory (CBRAM) is a one of the most promising new memories due to its simple structure, low power consumption, high scaling potential, large on/off margin and high speed. It has been reported that resistivity switching of CBRAM is induced by filament formation and rupture due to metal cation movement in the solid electrolyte. In the previous our research work, we studied CuO based CBRAM using CuTe top electrode. But CuO is not a fab-friendly material. In this work, instead of CuO based material, TiO2 are used for solid electrolyte because TiO2 is fab-friendly material and it has a good compatibility with a conventional CMOS process. TiO2 exist in three phases in atmospheric pressure, i.e. anatase, rutile and brookite, which phase of TiO2 presents different physical properties. In this work, we compared switching characteristics of amorphous with anatase phases TiO2 CBRAM. XRD confirmed amorphous-anatase phase transition at annealing temperature of 400 oC, as shown in Fig.1. Based on the crystallinity of TiO2 thin film, two different samples were prepared, amorphous (W/O annealing) and anatase phase TiO2 CBRAM (400 oC annealing). The CBRAM was fabricated on plug type TiN bottom electrode patterned wafer. The size of the bottom electrode was 34nm to 1921nm. TiO2 layer was deposited by RF magnetron sputter. And CuTe electrode was deposited by DC magnetron sputter. The structure of the device was shown in Fig.2 (a). On/Off ratio of TiO2 based CBRAM with amorphous phase was greater than that with anatase phase TiO2 CBRAM because HRS (High Resistive State) of the amorphous phase TiO2 CBRAM was lower than that of anatase phase TiO2 CBRAM. The amorphous and anatase phase TiO2 based CBRAMs demonstrated the endurance cycles of 105 and 2X106 respectively. We will report the memory characteristic of two phases TiO2based CBRAMs and explained why they showed the different memory characteristic.

* This work was financially supported by the Industrial Strategic Technology Development Program (10039191, The Next Generation MLC PRAM, 3D ReRAM, Device, Materials and Micro Fabrication Technology Development) funded by the Ministry of Trade, Industry and Energy (MOTIE), Republic of Korea and the Brain Korea 21 Plus, Republic of Korea.

Figure 1
Resistance Switching Structures Based on Hydrogen Silsesquioxane (HSQ) Thin Films
Authors: Ng Wing Hung , Mehonic Adnan , Montesi Luca , Buckwell Mark , Kenyon Anthony Joseph
Published: February 2020

In recent years, resistance switching (ReRAM) devices have attracted a lot of attention due to their properties in low programmable energy and fast switching speed which could lead to potential applications in non-volatile memory. Hydrogen silsesquioxane (HSQ) is commonly used in electronic industry as a flowable dielectric material, and here we present our recent study of using HSQ thin film as an active switching material.

We carried out x-ray photoelectron spectroscopy (XPS) on HSQ thin films; results showed that they are SiO2 like after spin-coating and soft baking. Electrical characterisation results showed our metal-insulator-metal devices required typically -1.2V to switch from a high resistance state (HRS) to low resistance state (LRS). The voltage required to reset the device from LRS to HRS was typically +1.5V. The device was capable of bipolar switching and multiple setting and resetting cycles could be achieved with voltage pulses. Retention studies showed the device had retention properties of up to 105 seconds.

We have also fabricated HSQ nanopillar array and addressed individual nanopillars with a conductive atomic force microscope (CAFM). Results showed we could change the conductivity of individual pillars by applying bias on the sample via the CAFM tip. These encouraging results show HSQ is potentially a very promising material for non-volatile ReRAM applications.
The Application of Advanced Pulsed Plasma in Fin Etch Loading Improvement
Authors: Zhang Haiyang , Xiao Fangyuan , Han Qiuhua
Published: February 2020

With the background of general integrated circuit (IC) feature size shrinking designers to get high performance transistors, Self-Alignment-Double-Patterning (SADP) FinFETetch was widely used in 14/16 nm technologies node and beyond. Rigorous process loading control (CD, profile, depth) in reactive ion etch (RIE) becomes more critical and challenging to ensure precise patterning and to avoid performance degradation among different features.[1]However, it’s quite hard to tackle such notorious loading for its inherent high Te induced ionization in traditional continuous wave (CW) plasmas.Thus, significant improvements in controlling plasma properties in a dry etching reactor are essential to satisfy such stringent requirement.

Pulsed plasmas have demonstrated several advantages compared to CW plasmas. By varying the pulse frequency and the duty cycle, pulsed plasma provide additional “control knobs” in controlling critical plasma parameters, such as ion and electron densities, electron temperature, flux and energy of the ions and radicals incident on surface. These critical factors affecting overall on-wafer performance during plasma etching processes at both within wafer and within die levels, etching and deposition, vertical and lateral etch rate, profile control, feature sidewall passivation and plasma damage.[2]In view of characters of pulsed plasma noted above, it appears to be a promising approach to improve RIE-lag loading in SADP fin etch.

In this paper, we systematically investigated the influence of both bias pulsed plasma and synchronous pulsed plasma to fin CD, profile (sidewall angle) and depth loading performance among dense and semi-isolated lines. It was found that proper duty cycle and frequency of pulsed power could drastically impact the loading performance. Based on the above learning, we finally delivered the overall solution by introducing synchronous pulsed plasma etch in mandrel and shallow trench isolation (STI) to address the rigorous loading control between dense and isolated patterns.

[1] Y. Wang, et al, CSTIC, “Process Loading Reduction on SADP FinFET Etch”, 2015

[2] S. Banna, et al, JVST A, “Pulsed High-density Plasmas for Advanced Dry Etching Process”, 2012
In-Situ Rare Earth Doping of Silicon-Based Nanostructures By Plasma Enhanced Chemical Vapour Deposition
Authors: Mascher Peter , Wojcik Jacek , Khatami Zahra , Miller Jeremy William , Brown Austin
Published: February 2020

In order for Si-based materials to be used in solid-state lighting (SSL) schemes it is necessary to have precise control of the optical emission from these materials. This can be accomplished through the use of rare earth dopants such as Ce, Tb, and Eu to obtain blue, green, and red emissions, respectively. After a brief review of the latest developments in the field, this talk will focus on several in-situ doping approaches to achieving very high, optically active concentrations of the rare earths. The methodologies include electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD), inductively coupled plasma (ICP) CVD as low thermal budget processes for film deposition, reactive sputtering, as well as the use of a recently installed Circular High Vacuum Magnetron Sputtering source attached to the ECR-PECVD tool. We will describe the salient features of the deposition systems and correlate important process parameters with the observed luminescence. Finally, we will discuss some of the challenges in developing electrically driven lighting cells suitable for SSL and in particular, for the development of widely tuneable Si-based light sources.

This work has been supported by the Natural Sciences and Engineering Research Council (NSERC) under its Discovery Grants Program.
(Invited) Role of Charges in Non-Classical Crystallization of Thin Films and Nanostructures in the Plasma CVD Process
Authors: Hwang Nong-Moon
Published: February 2020

Extensive studies have been made on non-classical crystallization, which refers to the crystal growth by the building unit of nanoparticles. In parallel with the non-classical crystallization in the crystal growth in solution, the non-classical crystallization in the gas phase synthesis of thin films and nanostructures by chemical vapor deposition (CVD) and some physical vapor deposition (PVD) has been studied extensively. Here, the charged nanoparticles (CNPs) are spontaneously generated in the gas phase and become the building block of thin films and nanostructures. Charged nanoparticle-based crystallization appears to be very general, including the growth of diamond, Si, ZrO2, GaN, ZnO films as well as nanowires. The generation of CNPs in the gas phase was experimentally confirmed in many systems and their mass distribution was shown to play a decisive role in the microstructure evolution of films, nanowires, and nanotubes. The fact that CNPs can be a building block of crystals without leaving any void behind and of nanowires with smooth surface indicates that CNPs are quasi-solid, having a liquid-like property in diffusion. This means that the charge enhances the atomic diffusion, which is a newly discovered physical phenomenon. This means again that charge weakens the bond strength. Small nanoparticles can be liquid-like even if singly charged but large nanoparticles should be multiply charged to be liquid-like. Based on this understanding, the microcrystalline silicon without an amorphous incubation layer could be deposited on a glass substrate at 320oC and on a polymer substrate at 200oC. Using the liquid-like property of CNPs, the epitaxial growth of silicon was successfully achieved at 550oC by the plasma CVD process. Weakening of bond strength by charges would enhance chemical reactions at low temperature, which can explain the low temperature decomposition in the plasma CVD process. Charge-enhanced diffusion would favor the crystallization and produce charged crystalline nanoparticles at low temperature in the plasma, which explain the low temperature deposition of crystalline films by the plasma CVD process. References

N.M. Hwang and D.K. Lee, J. Phys. D: Appl. Phys.
43, 483001 (2010) (Topical Review).

A. Badzian and N.M. Hwang, Diamond: Low-Pressure Synthesis, Ref. Module of Mater. Sci. & Mater. Eng. (2016).
(Invited) Plasma Treatment on 2D Mxene Ti3C2 Nanosheets for Water Desalination
Authors: Yang Hui Ying
Published: February 2020

Carbon materials, such as activated carbon, carbon nanotubes, graphenes and carbon composites, have been extensively explored for capacitive desalination. Though considerable efforts have been devoted to enhance the removal capacity, the achievement was still limited to less than 15 mg g-1. Plasma treated 2D Mxene Ti3C2 was firstly explored for capacitive desalination hybrid with activated carbon in a CDI unit cell. An optimized performance was obtained with a large removal capacity of 22.8 mg g-1 and a high charge efficiency of 58% at the external power of 1.2 V. The asymmetric CDI unit cell composed of 2D Mxene Ti3C2 is promising for capacitive desalination due to the merit of high surface area and conductivity of the nanosheets.
Atmospheric Plasma Jet Oxidation of Solution Based Precursors for Enabling Material Discovery
Authors: Ajayi Babajide , Jaramillo-Cabanzo Daniel Felipe , Kumari Sudesh , Spurgeon Joshua M , Jasinski Jacek B , Sunkara Mahendra Kumar
Published: February 2020

Paramount to the global action plan on climate change is the renewable energy technology that drives carbon neutrality goal, and vital in this pursuit is the addressing of material challenges currently facing this technology. To properly address this issue, a synthesis technique capable of accelerating the discovery of materials for various energy conversion and storage applications needs to be developed. Here we present a technique that allows rapid and controlled synthesis of mixed metal oxide particles using plasma oxidation of liquid droplets containing mixed metal precursors1. The conventional wet chemical methods for synthesis of multimetal oxide solid solutions often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control. The concept is demonstrated by synthesizing binary and ternary transition metal oxide solid solutions with control over entire composition range using metal precursor solution droplets oxidized using atmospheric oxygen plasma. The results show the selective formation of metastable spinel and the rocksalt solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMnzFe2−zO4 (0 ≤ z ≤ 1), exhibits considerable electrocatalytic activity toward oxygen evolution reaction, achieving an overpotential of 0.39 V at a benchmarking current density of 10 mA/cm2 for a low manganese content of z = 0.20.

References

1. Ajayi, B. P., S. Kumari, et al. (2016). "A rapid and scalable method for making mixed metal oxide alloys for enabling accelerated materials discovery." Journal of Materials Research, 1-12 doi: http://dx.doi.org/10.1557/jmr.2016.92
Electromagnetic Interference Shielding Effectiveness of Silver Thin Films Fabricated By Dry Plasma Reduction
Authors: Oh Hyo-Jun , Dao Van-Duong , Choi Ho-Suk
Published: February 2020

Owing to the wide use of commercial, military, and scientific electronic devices and communication instruments, electromagnetic interference (EMI) shielding of radio frequency radiation is becoming a serious global problem. In general, light weight, high conductivity and excellent adhesion are required for EMI shielding materials. Metals and their composites are the most popular materials for EMI shielding effectiveness. Currently, they are usually deposited by sputtering and electrodeposition. However, there are some inconvenience for their wide application such as expensive vacuum equipment, or high voltage and small cell used for deposition method. Recently, we developed a new process for efficiently synthesizing supported metal, core-shell, bimetallic nanoparticles by using dry plasma reduction (DPR) near room temperature under atmospheric pressure. The aim of this technique was to overcome the previous mentioned process restrictions. We present, for the first time, here the use of DPR to fabricate silver thin film on PET substrate under atmospheric pressure, without using any toxic chemicals, near room temperature for EMI shielding applications. The morphology and silver film thickness are characterized through HRSEM. The formation of silver nanoparticles are examined using TEM, XRD and XPS measurements. Silver film conductivities are measured by four point probe. The results show that silver thin films are successfully fabricated by DPR. EMI shielding effectiveness is measured in the frequency range from 0.045 to 1 GHz. As the results, the silver thin films have significant shielding effectiveness of more than 55 dB at 0.1 GHz with near 600 nm thickness and sheet resistance of 0.087 Ω/□. Furthermore, the increase in silver film thickness resulted in decreasing sheet resistance and increasing EMI shielding effectiveness.
Thin and Flexible Nickel Based Current Collectors Developed By Electroless Deposition for Energy Storage Devices
Authors: Wu Haoran , Susanto Amelia , Lian Keryn
Published: February 2020

The rapid development in portable and wearable consumer electronics for recreation, fitness and medicines requires thin, light weight and flexible solid state energy storage devices to improve the user experience and safety. Among the key components for solid state energy storages, relatively little effort has been made to the development of flexible current collectors. A polyethylene terephthalate (PET) film here was metallized by a simple and inexpensive electroless nickel deposition to form thin and flexible current collector for solid state energy storage devices. The PET was etched in butylamine, followed by surface activation of reduced nickel particles by sodium borohydride. The electroless nickel was then conducted in a commercial available plating bath. The chemical composition of the developed nickel on PET (Ni-PET) current collector was characterized by EDX and XPS, which showed a high P nickel deposition. SEM images suggested an island growth during the film formation.

The electrochemical characterizations showed that the Ni-PET can be used both as current collectors for electrochemical capacitors (EC) and as electrodes for batteries (Fig. 1a) in the respective potential regions. The electrochemical performance of the Ni-PET current collector was similar to that of Ni foil but with less hydrogen evolution at low potential, and the flexibility was also better than that of a metallic Ni foil. The resistance of the Ni-PET current collector almost remained the same under compression but increased under tension. Nonetheless, the shape and conductivity can be recovered when the applied force was released. The carbon nanotube was coated on the Ni-PET to form an electrochemical capacitor electrode and showed high chemical stability in both liquid and solid electrolytes (Fig. 1b), suggesting a promising application in solid energy storage devices.

Figure 1
Electroless Deposition of Co-Mo-P (or B) Alloys for Ulsi Applications
Authors: Sverdlov Yelena , Shacham-Diamand Yosi , Shklovsky Jenny
Published: February 2020

The purpose of this work was on the one hand to produce Co-Mo-P (or B) deposits and on the other to use our Co-P electrolyte as universal and to obtain Co-W-P or Co-Mo-P thin films from common solution. The Co-W-P electrolyte with sodium tungstate Na2WO4 or tungsten phosphoric acid H3[P(W3O10)4] as a source of W-ions was well studied. In this paper we present the process of Co-Mo-P (or B) electroless deposition from either sulfate and chloride bath at basic conditions using sodium hypophosphite or sodium borohydride as a reducing agent. The material and chemical properties of the obtained films were characterized. The paper focuses on the deposition process and study of electroless deposited films for using in microelectronic technology.

The Co-Mo-P and Co-Mo-B thin films were obtained from sulfate and chloride bath correspondingly. The refractory metal has been introduced to the solutions by adding molybdate ions.

The Co-Mo-P and Co-Mo-B were obtained by chemical method. The structure of electroless deposited Co-Mo-P (B) films was amorphous as determined by XRD analyze. By this is meant that barrier properties of electroless deposited Co-Mo-P(B) thin films are bound to be reasonably good. The resistivity of the deposited on Co-seed Co-Mo-P thin films with thickness of 60nm after annealing was 80 μΩ.cm. The resistivity of the Co-Mo-B layers with thickness of about 50-60 nm was 100 μΩ.cm and 38-40 μΩ.cm for Co and Cu seed, respectively. Co-Mo-P deposition process is less expensive as compared to Co-W-P deposition by reason of very low Mo-concentration in bath (0.1 g/l).

References

E.J. O'Sullivan, A.G. Schrott, M. Paunovic, C.J. Sambucetti, J.R. Marino, P.J. Bailey, S. Kaja, and K.W. Semkow, IBM J. Res. Develop., 42, p. 607 (1998).

F.Pearlstein, R.F.Weigman, Plating, 54, 714 (1967).

Physico-chemical origins of the chemical reduction of cobalt, K.M. Gorbunova ed., Science Publishing, Moscow (1974) (in Russian).

Y. Shacham-Diamand, Y. Sverdlov and N. Petrov, J. Electrochem. Soc., 148, C162 (2001).

5. Y.Shacham-Diamand, A.Zylberman, N.Petrov, Y.Sverdlov, Microel. Eng., 64, p.315-320 (2002)

Figure 1
Eletroless Plating of Copper on Graphite Powders for Homogeneous Copper-Carbon Composite
Authors: Lee Hyukjae , Chung Tai-Joo , Pyo Hyun-Uk
Published: February 2020

DC motor brush facilitates current connection between moving parts and stationary wires in motor. Copper wire brushes are traditionally used in the past, but carbon brushes are more widely used in recent days. Although carbon brush offers high resistance and better commutation between commuter segments, it wears more rapidly than copper brushes due to its softness. New copper and carbon composite brushes have been developed to overcome this drawback of copper wire, however, the density difference between the carbon and copper results in inhomogeneity during mixing which causes poor sinterability and less than expected performance of the final product.

A simple way to bypass this problem is the coating of copper on carbon powder which easily reduces inhomogeneity caused by the density difference. In this work, copper is electrolessly plated on graphite powders and the effect of plating variables on the sintering behavior of the coated graphite powders. Prior to the electroless plating of copper, standard activation and sensitization procedures are applied to graphite powders using SnCl2-PdCl2 solution and PdCl2, respectively. For electroless plating of copper, formaldehyde is used as reducing agent of copper sulfate. Various ratios of amount of copper sulfate and graphite powder, pH, and plating times are tested to find the optimum condition for sintering of the coated powder. The results show that the copper coated graphite successively produces homogeneous sintered compacts, which shows improved sinterability as well.