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Efficient doping for modulating electrical properties of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is essential for meeting the versatile requirements for future electronic and optoelectronic devices. Because doping of semiconductors, including TMDCs, typically involves generation of charged dopants that hinder charge transport, tackling Coulomb scattering induced by the externally introduced dopants remains a key challenge in achieving ultrahigh mobility 2D semiconductor systems. In this study, we demonstrated remote charge transfer doping by simply inserting a hexagonal boron nitride layer between MoS 2 and solution-deposited n-type dopants, benzyl viologen. A quantitative analysis of temperature-dependent charge transport in remotely doped devices supports an effective suppression of the dopant-induced scattering relative to the conventional direct doping method. Our mechanistic investigation of the remote doping method promotes the charge transfer strategy as a promising method for material-level tailoring of electrical and optoelectronic devices based on TMDCs.

Efficient doping for modulating electrical properties of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is essential for meeting the versatile requirements for future electronic and optoelectronic devices. Because doping of semiconductors, including TMDCs, typically involves generation of charged dopants that hinder charge transport, tackling Coulomb scattering induced by the externally introduced dopants remains a key challenge in achieving ultrahigh mobility 2D semiconductor systems. In this study, we demonstrated remote charge transfer doping by simply inserting a hexagonal boron nitride layer between MoS

Low-temperature solderless Cu–Cu bonding is an important technology for advanced packaging, such as fine-pitch 3-D packaging and heterogeneous integration. In this study, we prepared an oxidation-free Cu surface using an optimized N2 plasma process in a two-step Ar/N2 plasma treatment based on the design of the experiment method, to improve direct Cu–Cu bonding quality at 260 °C. The N2 plasma treatment process was optimized using the Minitab optimizer with chemical state results obtained by X-ray photoelectron spectroscopy (XPS) analysis. The Cu surface treated under the two-step Ar/N2 plasma with optimized N2 plasma conditions not only formed Cu nitride well, but the surface remained without further oxidation for at least one week at room temperature. The Cu–Cu bonding was performed at the low bonding temperature of 260 °C and low bonding pressure of 0.9 MPa for 1 hour, and the bonded interface was evaluated using scanning acoustic tomography (SAT) and field emission scanning electron microscope (FE-SEM) images. We measured shear strength to estimate the bonding interface quality of the oxidation-free Cu–Cu bonding specimen. A maximum shear strength of 62.6 MPa was obtained. Our bonding results demonstrated remarkably improved Cu–Cu bonding quality compared with other previous Cu–Cu joint studies that used Sn, Cu/Ag nanoparticles, or Cu composites.

Biocidal disinfectants (BDs) that kill microorganisms or pathogens are widely used in hospitals and other healthcare fields. Recently, the use of BDs has rapidly increased as personal hygiene has become more apparent owing to the pandemic, namely the coronavirus outbreak. Despite frequent exposure to BDs, toxicity data of their potential neurotoxicity (NT) are lacking. In this study, a human-derived SH-SY5Y/astrocyte was used as a co-culture model to evaluate the chemical effects of BDs. Automated high-content screening was used to evaluate the potential NT of BDs through neurite growth analysis. A set of 12 BD substances classified from previous reports were tested. Our study confirms the potential NT of benzalkonium chloride (BKC) and provides the first evidence of the potential NT of poly(hexamethylenebicyanoguanide-hexamethylenediamine) hydrochloride (PHMB). BKC and PHMB showed significant NT at concentrations without cytotoxicity. This test system for analyzing the potential NT of BDs may be useful in early screening studies for NT prior to starting in vivo studies.

3D packaging is able to keep the scaling in semiconductor market. Increased and shorter interconnects achieved by vertical stacking have benefits such as improved performance, reduced signal delay, and small form factor. In order to obtain high-quality 3D packaging applications, the integration of heterogeneous devices through bonding technologies is very important. Low temperature and pressure are essential during the bonding process because most of logic/memory devices has many metal and low-k dielectric layers, which are vulnerable to thermal budget and mechanical stress. Therefore, a small amount of solder with a low melting point is presently used on the top of the copper pillar for mass production. But, solder creates an intermetallic compound with copper at the bonding interface and cannot be applied to fine pitch patterns due to their reflow characteristics. Thus, Cu is emerged as a promising interconnect, but Cu-Cu bonding has few challenges because copper is easily oxidized and has a high melting point. In this paper, copper nitride, which prevents oxidation of the copper surface and promotes low temperature bonding, was studied by two step Ar/N 2 plasma treatment. The optimum thickness of copper nitride passivation was derived using the design of experiment. It was also found that the copper nitride layer was almost decomposed at a temperature of 200°C.

Biocidal products are broadly used in homes and industries. However, the safety of biocidal active substances (BASs) is not yet fully understood. In particular, the neurotoxic action of BASs needs to be studied as diverse epidemiological studies have reported associations between exposure to BASs and neural diseases. In this study, we developed in silico models to predict the blood-brain barrier (BBB) permeation of organic and inorganic BASs. Due to a lack of BBB data for BASs, the chemical space of BASs and BBB dataset were compared in order to select BBB data that were structurally similar to BASs. In silico models to predict log-scaled BBB penetration were developed using support vector regression for organic BASs and multiple linear regression for inorganic BASs. The model for organic BASs was developed with 231 compounds (training set: 153 and test set: 78) and achieved good prediction accuracy on an external test set (R2 = 0.64), and the model outperformed the model for pharmaceuticals. The model for inorganic BASs was developed with 11 compounds (R2 = 0.51). Applicability domain (AD) analysis of the models clarified molecular structures reliably predicted by the models. Therefore, the models developed in this study can be used for predicting BBB permeable BASs in human. These models were developed according to the Quantitative Structure-Activity Relationship validation principles proposed by the Organization for Economic Cooperation and Development.

Crystalline ZnO:Ga thin films with highly preferential c-axis oriented crystals were prepared on Si(001) substrates at different temperatures using the reactive magnetron sputtering technique. Effects of temperature-induced stress in ZnO:Ga films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), electrical transport, and spectroscopic ellipsometry measurements. XRD results showed that the films were highly c-axis (out-of-plane) oriented and crystallinity improved with growth temperature. The residual compressive stress in films grown at low temperature relaxes with substrate temperature and becomes tensile stress with further increases in growth temperature. Resistivity of the films decreases with increasing stress, while the carrier concentration and mobility increase as the stress increases. The mechanism of the stress-dependent bandgap of ZnO:Ga films grown at different temperatures is suggested in the present work.

As copper technology moves from pilot to volume manufacturing, semiconductor fabrication is focused on methods to improve device yield. In especially semiconductor manufacturing, electrochemically deposited copper is the material of choice for advanced interconnect applications. Electrochemical deposition (ECD) employs copper plating electrolytes with organic additives to achieve bottom-up filling of small vias and trench with high aspect-ratios. However, for features with small aspect-ratios, the ECD process yields conformal layers because the additives and the bottom-up fill mechanism are not operative in such large features. So, ECD process does not achieve within-die and within-wafer planarity of the deposited copper layer. For planarization of large features and obtaining globally and locally flat films, an electro-chemical mechanical deposition (ECMD) method has been employed. ECMD process is a novel technique that has ability to deposit planar conductive films on non-planar substrate surfaces. Technique involves simultaneous ECD roles and mechanical sweeping of the substrate surface. Copper layer deposited by the ECMD process grows preferentially in cavities on the wafer surface yielding flat profiles and much reduced overburden thickness. Preferential deposition into the cavities on the substrates surface may be achieved through two different mechanisms. The first mechanism is more mechanical in nature and it involves material removal from the top surface. The second mechanism is more chemical in nature and it involves enhancing deposition into the cavities where mechanical sweeping does not reach, and reducing deposition onto surfaces that are swept. Planar layers obtained by the ECMD technique are suitable for low stress material removal processes. Planar layers also yield improved parametric results in device structures after the material removal step. In this study, we demonstrate mechanical role of pad gives effects in ECMD process. So we evaluate gap-filling and planarization between ECMD and ECD.

Summary form only given as follows. A balanced and efficient allocation of R&D resources is a crucial element of corporate strategies aimed at enhancing firms' competitiveness. This paper evaluates R&D strategy of Korea Gas Corporation (KOGAS), a monopolistic state-owned gas company, with respect to efficiency of its project selection and technology stock accumulation. We measure technology stocks and their associated spillovers in order to assess the extent of allocative efficiency of R&D expenditure across a set of peer groups of research and development projects. We also combine the technology relation analysis with the measurement of the technology stock, although the two have been heretofore considered to be separate analytical tools. Technology stocks of 45 peer projects were evaluated, allowing us to derive a technology map of R&D fields of KOGAS. Our empirical findings imply that, in allocating its R&D resources, KOGAS was putting too much emphasis on operation and maintenance of its facilities. We therefore suggest that KOGAS may wish to reallocate its R&D resources to other research areas such as the development of new energy sources, participation in the overseas gas markets and design of the strategies conducive to its becoming what its vision is: being a world-class energy company.