bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Silicon Nanowires: Donors, Surfaces and Interface Defects
Authors: Fanciulli Marco , Paleari Stefano , Belli Matteo , Lamperti Alessio 
Published: February 2020

Group IV semiconductor nanowires have been investigated experimentally and theoretically for several years. Their intriguing and yet not fully understood properties and the potential for applications in nanoelectronics, spintronics, energy harvesting, production and storage, sensors, and neuroelectronics motivate this research effort. Due to the high surface area SiNWs and GeNWs represent also a perfect material science lab to investigate with high accuracy specific issues related to defects and interfaces. The investigation of defects at the interface between silicon and silicon oxide becomes very important when the SiNW diameter reduces below 10-20 nm and the surface-to-volume ratio increases [1, 2]. In the present work we focus on the investigation of the doping of silicon nanowires addressing the role of hydrogen, as well as other passivating species, and Pb defects at the Si/SiO2 interface [3-5] in the donor deactivation mechanisms and the role of the confinement and dielectric mismatch in determining the donor electronic wave function. To address these intriguing issues we have used different complementary experimental techniques such as electron paramagnetic resonance (EPR), both continuous wave and pulsed, FT-IR, and MD-PICTS. Silicon nanowires have been produced by metal-assisted chemical etching (MACE) [6, 7] using either Ag nanoparticles or a thin Au layer as catalyst and further processing has been used to reduce the size of the nanowires. The reported results are relevant for the wide range of applications exploiting the peculiar silicon nanowires electronic properties and surface reactivity. GeNWs and core-shell heterostructures (Si/Ge) produced by vapor-liquid-solid growth have been also investigated and results on the dominant defects in these nanostructures will be discussed.
References:
[1] V. Schmidt, S. Senz, and U. Gösele, Appl. Phys. A. 86, 187 (2007)
[2] M. T. Björk, H. Schmid, J. Knoch, H. Riel and W. Riess, Nature Nanotech. 4, 103 (2009)
[3] M. Fanciulli, A. Vellei, C. Canevali et al., Nanosci. Nanotechnol. Lett. 3, 568 (2011)
[4] M. Fanciulli, A. Molle, S. Baldovino, A. Vellei , Microelectronic Engineering 88, 1482 (2011)
[5] M. Fanciulli, M. Belli, S. Paleari, A. Lamperti, M. Sironi, and A. Pizio, ECS J. Solid State Sci. Technol. 5(4), 3138 (2016)
[6] Z. Huang, N. Geyer, P. Werner et al., Adv. Mater. 23, 285 (2011)
[7] C. Canevali, M. Alia, M. Fanciulli, M. Longo, R. Ruffo, C.M. Mari, Surface & Coatings Technology 280, 37 (2015)
(Invited) Electrochemical Gating-Induced Hydrogenation in VO2 Nanowires at Room Temperature
Authors: Kanki Teruo , Sasaki Tusbasa , Tanaka Hidekazu 
Published: February 2020

The transport characteristics of transition metal oxides are sensitive to redox reactions because the valence numbers of the transition metal ions are easily changed by the reactions, which affect the carrier density and/or stabilization of the crystal structure. Conventionally, controlling the amount of hydrogen/oxygen ions in an oxide has been conducted by annealing the samples under redox gas atmospheres, in an aqueous solution and with a hydrogen spillover method. Every method requires high temperatures of at least 150 °C. Recently, on the other hand, an electric field has been shown to be a means of both hydrogenation and oxidization in oxides at room temperature. Thus electrochemical gating including water electrolysis has a full potential to allow hydrogen storage and tuning of doping level of electron carriers at room temperature.
In this research [1], reversible and drastic modulation of the transport properties in vanadium dioxide (VO2) nanowires by electric field-induced hydrogenation at room temperature was demonstrated using the nanogaps, separated by humid air in field-effect transistors with planer-type gates (PG-FET). These PG-FETs allowed us to investigate behavior of revealed hydrogen intercalation and diffusion aspects with time and spatial evolutions. These results show that air nanogaps can operate as an electrochemical reaction field, even in a gaseous atmosphere, and offer new directions to explore emerging functions for electronic and energy devices in oxides and will lead to the realization of new gas-sensing, storage applications and also ion pumps in a wide range of solid-state materials.
[1] T. Kanki et al, Sci. Rep. 5, 17080 (2015).
Particle Removal in Wet Wafer Cleaning Processes
Authors: Zhu Ji , Xia Man , Mui David , Kawaguchi Mark 
Published: February 2020

Defects in semiconductor manufacturing that originate from add-on particles can contribute to device yield loss. One possible avenue in removing these particles is a wet wafer cleaning process. Single wafer wet cleaning systems are the current industry standard for defect removal due to their superior ability to control particle re-deposition, especially near wafer edge, as compared to batch cleaning systems. However, our experiments have shown that large micron-sized particles re-deposit during a typical single wafer cleaning process in a model system. These particles were moved and re-deposited primarily during the initial wetting stage. A mechanistic model has been developed to estimate the forces acting on the particles at the three-phase contact line during the wetting stage. The model results show that the forces acting on a particle in the wetting stage are orders of magnitude higher than those in the steady state condition (Fig. 1). Thus, particles are more likely to be moved during the initial wetting step. However, if these moved particles were not transported out of the flow boundary, they could re-deposit and stress produced in steady state flow condition is insufficient to remove them.
To further remove smaller particles from wafer surface, a novel particle removal technology based on a polymer solution is reported in this paper. Physical cleaning methods, such as cryogenic aerosol spray, two-phase fluid aerosol spray and megasonic cleaning, have been used in both front-end- and back-end-of-line cleaning processes for a long time. However, all these methods have the risk of damaging fine features on the wafer in today’s advanced process nodes. Thus, there is a need for a damage-free high efficiency particle removal technology. Polymer solutions have long been used in paper making and water treatment industries to aggregate particles either to deposit them on papers or for their removal from water. The same particle aggregation property of polymer solution has been successfully applied to particle removal. High particle removal and no pattern damage have been demonstrated. The particle removal effect is also highly synergistic with SC1 chemistry. By combining these two approaches, particles 25 nm and above can be removed with >90% efficiency.
Fig. 1 Schematic of forces acting on defects during wetting stage. FM is motion induced interfacial force, Fdis the hydrodynamic drag force.

Figure 1
Preventing TSV Protrusion Via Controlling Impurity Content in Copper Electrodeposits
Authors: Lee Ui-Hyoung , Park Chae-Min , Lee Hyo-Jong , Lee Kihyeob , Kim Kangsoo 
Published: February 2020

3D IC integration is the latest technological breakthrough for maximizing its performance while reducing wiring lengths, interconnection latency, and power consumption. Through-silicon via (TSV) is an essential feature of the 3D IC integration. Filling high aspect ratio TSVs by the conductive materials can be a challenging task. Copper electrodepostion is often adopted due to its optimal electrical preoperties, simplicity, and cost-effectiveness. However, the coefficient of thermal expansion (CTE) of copper is much higher (16.7 ppm/℃) than that of silicon (2.3 ppm/℃). Therefore, the CTE mismatch between copper and silicon substrate can induce thermal stresses, which may lead to TSV protrusion and interfacial delamination. In previous studies, this is mostly managed via suitable heat treatment. This study however proposes a novel method for controlling TSV protrusion. Copper with JGB (Janus Green B, C30H31ClN6) concentration increases (and at the level of 0.2mM of JGB), while the sheet resistance decrease by 7% for the initial resistance. Here, the crystal growth is not observed that is due to impurity pinning or solute dragging effect at grain boundaries. This leads to the conclusion that controlling impurity contents may relieve stress of TSV overhang area. To prevent TSV protrusion, we also perform the same concentration split tests on TSV pattern wafers.
Figure 1. EBSD IPF maps of Cu electrodeposit after annealing at 80 ℃ for 90 min with various JGB concentrations of (a) 0, (b) 0.01, (c) 0.03, (d) 0.1, (e) 0.2 and (f) 1 mM in the Cu plating bath.

Figure 1
(Invited) Nanostructured Photocatalysts Prepared By Atomic Layer Deposition
Authors: Szilagyi Imre Miklos 
Published: February 2020

Semiconductor oxides are widely used photocatalysts to decompose organic contaminations with solar energy. The activity of these photocatalysts can be further improved by doping them with heteroatoms, by making composites of them with other semiconductor oxide materials, noble metal nanoparticles, organic dyes and other organic absorbers, or by increasing their specific surface using highly structured substrates. Since by ALD uniform thin films with thickness control of sub-nanometer precision can be deposited on nanopatterned surfaces, it is a unique tool for preparing, doping and programming nanoscaled photocatalytic material.
In the lecture several examples will be shown about how various nanostructured photocatalysts can be obtained by ALD, based on our own experience. By combining electrospinning and ALD, WO3/TiO2, ZnO/TiO2 and TiO2/ZnO core/shell Vis or UV active nanofiber photocatalysts were prepared. By using sol-gel and ALD, SiO2/TiO2 core/shell photocatalytic nanoparticles were obtained. Photocatalysts based on biological substrates can be also manufactured by ALD, e.g. TiO2 coated lotus leaves with both superhydrophobic and photocatalytic activities. C60/TiO2 (Fig. 1), graphene oxide (GO)/TiO2, CNT/TiO2, carbon aerogel/TiO2 and PMMA/TiO2 composites are examples for ALD prepared carbon and polymer nanostructure based photocatalysts.
On the previously mentioned substrates, TiO2 thin films were deposited by ALD using TiCl4 or Ti(OPr)4 and H2O as precursors at various temperatures (80, 160, 250, 300 °C), and therefore nanocomposites containing both crystalline and amorphous TiO2 layers were prepared. While TiO2 is considered to have photocatalytic activity only in the crystalline state; unexpectedly, we observed that when TiO2 was deposited in amorphous form on biological or organic substrates, i.e. lotus leaf, C60-OH, GO or PMMA, the amorphous TiO2 layer clearly exhibited photocatalytic property.

Figure 1
A Precise and Scalable Post-Modification of Mesoporous Metal-Organic Framework NU-1000 Via Atomic Layer Deposition
Authors: Kim In Soo , Farha Omar K. , Hupp Joseph T. , Gagliardi Laura , Chapman Karena W , Cramer Chris , Martinson Alex B. F. 
Published: February 2020

The connectivity of NU-1000 gives rise to Zr nodes with hydroxyl-containing functional groups pointing into the large 1D mesoporous hexagonal channels of the framework. These free and exposed –OH groups are ideal grafting sites, and they can be easily tailored to serve a specific function. We demonstrate that by performing atomic layer deposition in MOFs (AIM), several oxides can be formed with atomic precision at the exposed –OH sites of NU-1000. Importantly, this process occurs without changing the overall structure of the framework. This talk will discuss recent progress in scaling AIM to 0.2 gram quantities of the ultrahigh surface area (2300 m2/g) framework as well as progress in pinpointing the location and mechanism of surface chemical reactions of catalytically relevant metals. Computational, synchrotron, and in-situ analytical methods including DFT, differential electron diffraction, and in situ FTIR are brought to bear on several new metal systems, many of which show remarkably self-limiting behavior.
The Figure shows a representation of the DFT-derived model of a Zr6 node, highlighting the newly installed metal location.

Figure 1
Effect of Thickness on Flexible, Electrical and Optical Properties of Ti- ZnO Films on Flexible Glass By Atomic Layer Deposition
Authors: Lee Woo-Jae , Kwon Jung-Dae , Kwon Se-Hun 
Published: February 2020

TCO (Transparent Conducting Oxide) on flat glass is used in thin-film photovoltaic cell, flat-panel display. Nowadays, Corning® Willow Glass®, known as flexible substrate, has attracted much attention due to its many advantages such as reliable roll-to-roll glass processing, high-quality flexible electronic devices, high temperature process. Also, it can be an alternative to flexible polymer substrates which have their poor stability and degradation of electrical and optical qualities. For application on willow glass, the flexibility, electrical, optical properties can be greatly influenced by the TCO thin film thickness due to the inherent characterization of thin film in nanoscale. It can be expected that while thick TCO layer causes poor transparency, its sheet resistance become low. Also, rarely reports were focusing on the influence of flexible properties by varying TCO thickness on flexible glass. Therefore, it is very important to optimize TCO thickness on flexible Willow glass.
In this study, Ti-ZnO thin films, with different thickness varied from 0 nm to 50 nm, were deposited on the flexible willow glass by atomic layer deposition (ALD). The flexible, electrical and optical properties were investigated, respectively. Also, these properties of Ti-doped ZnO thin films were compared with un-doped ZnO thin film. Based on the results, when Ti-ZnO thin films thickness increased, resistivity decreased and then saturated; transmittance decreased. The Figure of Merit (FoM) and flexibility was the highest when Ti-ZnO thickness was 40nm. The flexible, electrical and optical properties of Ti-ZnO thin films were better than ZnO thin film at the same thickness.
Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Thin Film at 100oc Using Novel Silicon Precursors
Authors: Jang Se-Jin , Park Joong-Jin , Kim Sung-Gi , Lee Sang-Do , Yang Byeong-il , Park Jung-Ju , Park Gun-Ju , Seok Jang-Hyeon , Lee Sang-Ick , Kim Myoung-Woon , Park Jae-Min , Hwang June , Lee Won-Jun 
Published: February 2020

Recently, the demand for moisture barrier has been increasing as the encapsulation layers of organic electronic devices, such as organic light-emitting diode (OLED) display, organic solar cells, and organic thin-film transistors. Dielectric thin films prepared by plasma-enhanced chemical vapor deposition (PECVD), hot-wire CVD, and atomic layer deposition (ALD) at low temperatures lower than 150°C have been investigated as the moisture barrier. Among them, the multilayered thin structure composed of aluminum oxide or silicon nitride prepared by ALD showed the best results [1,2]. In the present work, we prepared silicon nitride thin films by plasma-enhanced ALD (PEALD) at 100°C using novel silicon precursors, 1,3-di-iso-propylamino-4,4-dimethylcyclodisilazane (CSN-2) and bis-(di-methylamino-dimethylsilyl)- trimethylsilyl amine (DTDN-2H2), and investigated the properties of the deposited films, such as growth rate per cycle, composition, density, wet etch rate, and water vapor permeability. The effects of deposition temperature and plasma condition on the barrier properties were also discussed.
[1] F. Nehm, ACS Appl. Mater. Interfaces, 7 (2015) 22121.
[2] A.-M. Andringa, et al., ACS Appl. Mater. Interfaces, 7 (2015) 22525.
Fig.1. The FTIR spectrum of silicon nitride thin films prepared by PEALD at 100°C using CSN-2 as the silicon precursor.

Figure 1
Determination of Atomic-Layer-Deposited Multilayer Antireflection Coating Parameters Using a Novel X-Ray Reflectivity Approach
Authors: Li Chao , Shahriarian Firouz , Goorsky Mark S. 
Published: February 2020

The thicknesses and densities of coatings prepared by atomic layer deposition (ALD) and by other deposition techniques are important to understand their optical, electrical and mechanical properties. Specular X-ray reflectivity (XRR) is a powerful tool that is capable of nondestructively extracting layer thicknesses with angstrom resolution, and what is distinct, determining the layer densities through modeling structures with simulation programs. Unfortunately, problem with modeling usually arises when other layers form at the surface or interfaces, and it is also common to other nondestructive techniques such as ellipsometry. A recent development1 has shown that with differentiating the specular XRR intensity with respect to vertical reciprocal space coordinate, a Fourier transform (FT) approach can provide straightforward information about the layer thicknesses in multilayer systems, which will make it easier to build the XRR simulation model. Therefore, a novel combination of FT and specular XRR simulation would be quite efficient in layer thickness extraction compared with other conventional techniques (e.g. transmission electron microscope (TEM) and ellipsometry). In this study, the novel XRR approach, together with other techniques including optical microscope (OR), spectroscopic ellipsometry (SE), TEM, energy dispersive X-ray spectroscopy and glancing incidence X-ray diffraction, was utilized to characterize the effect of annealing on optical properties of Al2O3/TiO2/Al2O3 multilayer antireflection stack. The films were deposited on (0 0 1) Si wafers using ALD which is a good candidate for multilayer antireflection coatings, due to the self-limiting nature of chemical reactions resulting in the precise control of film thickness and large-area uniformity. The thickness values of the as-deposited layers determined by XRR agree quite well with those obtained from OR, SE and TEM, with the difference below uncertainty levels. This, together with the good correlation between layer densities extracted from XRR and refractive indices measured by OR and SE, demonstrates the validity of the XRR approach. On the other hand, it is revealed that air annealing at 400 °Ϲ for 10 min induces the densification of the TiO2 layer as well as the initiation of crystallization. Meanwhile, both Al2O3 layers keep amorphous after annealing, with the thickness of top Al2O3 layer decreased that is likely due to interdiffusion of Al and Ti atoms between the top two layers, while the thickness of bottom Al2O3 layer increased accompanied with a decrease in density, which is probably attributed to the diffusion of Si atoms from the substrate into layers.
Reference

1B. Poust, R. Sandhu, and M. Goorsky, Phys. Status Solidi A. 206, 1780 (2009).
Atomic Layer Deposition of Zn(O, S) Buffer Layer on CIGS Solar Cell
Authors: Yu Yu-Hsuan , Kei Chi-Chung , Li Wen-Chieh , Wu Cheng-Han , Liang Shih-Chang , Ni Cuo-Yo , Shiao Ming-Hua 
Published: February 2020

Deposition of Zn(O, S) thin film as the Cd-free buffer layer is an important topic in Copper Indium Gallium Diselenide (CIGS) solar cells since it offers the potential enhancements for low cost and good for our environment. For CIGS buffer layer deposition, chemical bath deposition is the most common method in use. However, the incompatibility with in-line vacuum-based production methods is an issue of concerned.
In this study, the buffer layer of Zn(O, S) thin films were fabricated by atomic layer deposition (ALD) method with alternately depositing of ZnS and ZnO thin films, using diethyl Zinc((C2H5)2Zn, DEZ), dimethyl sulfide((CH3)2S, DMS), and H2O as the precursors. As the alternative layers were deposited, atomic layer deposition technique exhibits good step-coverage, uniformity and accurate control of layer thickness. By changing the cycle ratios (m/n) of ZnS and ZnO, the oxygen (O)/sulfide(S) composition can be controlled in the Zn(O, S) buffer layer thin film as shown in Fig. 1. Various O/S composition ratios of Zn(O, S) thin films were deposited on the CIGS absorber. The optical properties, microstructure and chemical analyses of the deposited Zn(O, S) buffer layer thin films were carried out by ellipsometry, scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The CIGS device performances were measured by current-voltage (I-V) measurements.
Keywords: CIGS, Zn(O, S) buffer layer, atomic layer deposition (ALD)
References
[1] U. P. Singh, S. P. Patra. International Journal of Photoenergy, 2010, 311–330.
[2] N. Naghavi, S. Spiering, M. Powalla, B. Cavana, D. Lincot. Progress in Photovoltaics: Research and Applications, 2003, 11, 437-443
[3] U. Zimmermann, M. Ruth, M. Edoff. Proceedings of the 21st European Photovoltaic Solar Energy Conference, Dresden, 2006, 1831–1834.
[4] A. Hultqvist, C. Platzer-Björkman, J. Pettersson, T.Törndahl, M. Edoff. Thin Solid Films, 2009, 517, 2305–2308.
[5]J. Lindahl, J. T. Wätjen, A. Hultqvist, T. Ericson, M. Edoff and T. Törndahl. Progress in Photovoltaics: Research and Applications, 2013, 1588-1597.

Figure 1
Behavior of La0.6sr 0.4Co0.2Fe0.2O3-δ Cathode Powders Surface Modified by Atomic Layer Deposition for Solid Oxide Fuel Cells
Authors: Roeder Jeffrey F. , Zeberoff Anthony F , Van Buskirk Peter C , Torabi Alireza , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Huang Kevin 
Published: February 2020

Atomic layer deposition (ALD) has been used to modify the surfaces of La0.6Sr0.4Co0.2Fe0.2O3-
d (LSCF) cathode powders with gadolinium doped ceria (GDC) and cobalt doped zirconia (CDZ). Cyclopentadienyl based Gd and Ce sources were used for GDC, while amidinate and amide sources were used for Co and Zr, respectively. ALD was carried out between 240-260°C. Transmission electron microscopy indicated uniform coating on selected samples, depending on process recipe. Coated powders were pressed into pellets and sintered at 1000°C in air. Microstructural analysis by scanning electron microscopy (SEM) revealed good sintering behavior. Similar sintering was observed for both GDC and CDZ treated powders. Pycnometry showed porosities in the range of approximately 41% for uncoated LSCF and in the range of 37-39% for surface modified powders and mercury probe analysis showed similar pore size distributions. Symmetrical electrochemical cells were prepared from pastes of uncoated and surface modified powders using a scandium stabilized zirconia electrolyte. Electrical impedance spectroscopy showed marked improvements in polarization for the surface modified powders (Fig. 1). ZrO2 and GDC coatings decreased polarization by a factor of 2. CDZ coatings decreased polarization by a factor of up to 4. Equivalent circuit modeling suggested little effect on gas diffusion through the porous structure, consistent with similar porosity values. Intermediate and high frequency contributions were significantly affected, suggesting a strong positive impact of the surface modification on both non-charge-transfer properties and charge-transfer properties, respectively. A pre-fabricated symmetrical cell treated with GDC via ALD showed very similar behavior to a symmetrical cell fabricated from surface modified GDC. This suggests that ALD may be used in alternate ways to improve cathode performance: on a fully sintered cathode or on the powder prior to sintering.

Figure 1