In this report, two types of substrates were prepared for deposition of few-layer tin disulfide (SnS2) via atomic layer deposition (ALD). The first substrate was prepared using a conventional ...cleaning method, while the second substrate was rinsed with buffered oxide etcher (BOE) solution after conventional cleaning. Changes in the substrate were confirmed by X-ray photoelectron spectroscopy, contact angle measurements, and electron spin resonance. Characteristics of the SnS2 thin films were determined by X-ray diffraction, Raman analysis, Fourier transform-infrared spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. To investigate growth rate, thickness was measured as a function of ALD cycle number by atomic force microscopy, and 2D layered structure was confirmed by transmission electron microscopy. Findings confirmed that surface treatment using BOE solution was related to an increased growth rate during the initial ALD process. Finally, back-gate field effect transistors based on ALD-grown SnS2 film prepared on substrate that received diluted-BOE surface treatment showed marginal improvement in current on/off ratio from 2.9 × 105 to 6.5 × 105 and mobility from 0.22 cm2/Vs to 0.31 cm2/Vs compared to ALD-grown SnS2 film prepared on bare substrate.
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•SnS2 thin films were grown by atomic layer deposition.•Bare and surface treated substrates were used to deposit SnS2.•Buffered oxide etchant solution was used to surface treatment.•Hydrophilicity of two different substrates was investigated.•Growth rate and transport properties of SnS2 thin films were investigated.
We used atomic layer deposition (ALD) to evaluate the effect of single Al2O3 cycle insertion at various locations on SnO2 and Al-doped SnO2 thin film transistors (TFTs). The ALD process was used to ...deposit the SnO2 thin film in 67 cycles (5 nm thickness). The position of the Al doped layer of Al-doped SnO2 was controlled by inserting a single Al2O3 cycle into the 56th, 34th and 12th cycles out of 67 cycles. The inserted Al doping layer was analyzed by secondary ion mass spectrometry (SIMS). Crystallinity and thickness of SnO2 and Al-doped SnO2 were measured using transmission electron microscope (TEM). Al-doped SnO2 thin films were prepared at different single Al2O3 cyclic positions for use as channel layers. XPS analysis showed that the oxygen vacancies within the film ranged from 32.8% to 41.6%. Also, the carrier concentration varied from 1.44 x 1016 to 2.80 x 1020 cm−3 depending on the Al doping position based on Hall measurements. In addition, the field effect mobility and on/off current ratios ranged from 1.4 to 8.1 cm2/Vsec and from 5.29 x 102 to 1.56 x 107, respectively. Lastly, the threshold voltage varied from −6.56 to 11.60 V. Overall, SnO2 and Al doped SnO2 channel layers deposited using atomic layer deposition were adjusted to exhibit switching characteristics by inserting a single Al2O3 cycle based on position.
Silicon nitride (SiNx) thin films using 1,3-di-isopropylamino-2,4-dimethylcyclosilazane (CSN-2) and N2 plasma were investigated. The growth rate of SiNx thin films was saturated in the range of ...200–500 °C, yielding approximately 0.38 Å/cycle, and featuring a wide process window. The physical and chemical properties of the SiNx films were investigated as a function of deposition temperature. As temperature was increased, transmission electron microscopy (TEM) analysis confirmed that a conformal thin film was obtained. Also, we developed a three-step process in which the H2 plasma step was introduced before the N2 plasma step. In order to investigate the effect of H2 plasma, we evaluated the growth rate, step coverage, and wet etch rate according to H2 plasma exposure time (10–30 s). As a result, the side step coverage increased from 82% to 105% and the bottom step coverages increased from 90% to 110% in the narrow pattern. By increasing the H2 plasma to 30 s, the wet etch rate was 32 Å/min, which is much lower than the case of only N2 plasma (43 Å/min).
VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via ...thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALDdeposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio. KCI Citation Count: 0
Photocrosslinked DNA Nanospheres for Drug Delivery Roh, Young Hoon; Lee, Jong Bum; Tan, Shawn J. ...
Macromolecular rapid communications,
July 1, 2010, Letnik:
31, Številka:
13
Journal Article, Conference Proceeding
Recenzirano
DNA has been employed as both a genetic and a generic material. X‐shaped DNA (X‐DNA) in particular has four branched arms, providing multivalent functionalities that can allow for simultaneous ...multiple crosslinking. Here we report the synthesis of four acrylate‐functionalized X‐DNA monomers that can be further photocrosslinked to form monodisperse and tunable DNA nanospheres. In particular, the size and surface charge of these nanospheres were precisely controlled in a linear fashion, simply by tuning the monomer concentration in the reaction. The morphology and surface properties of the nanospheres were characterized using FT‐IR, HPLC, TEM, AFM, zeta potential, and DLS analysis. In vitro studies in mammalian cells revealed that these DNA nanospheres demonstrated significant efficacy in the delivery of doxorubicin. These results highlight the potential of using DNA as material building blocks to design novel nanocarriers with properties tailored for the delivery of drugs in general and DNA/RNA in particular.
Novel monodisperse and tunable DNA nanospheres have been generated via rapid photocrosslinking of photoreactive branched DNA monomers. This paper describes the synthesis and characterization of photocrosslinked DNA nanospheres that may have potential applications as drug delivery carriers.
We investigated the effect of ZnO seed layer thickness on the density of ZnO nanorod arrays. ZnO has been deposited usingtwo distinct processes consisting of the seed layer deposition using ALD and ...subsequent hydrothermal ZnO growth. Due tothe coexistence of the growth and dissociation during ZnO hydrothermal growth process on the seed layer, the thickness ofseed layer plays a critical role in determining the nanorod growth and morphology. The optimized thickness resulted in theregular ZnO nanorod growth. Moreover, the introduction of ALD to form the seed layer facilitates the growth of the nanorodson ultrathin seed layer and enables the densification of nanorods with a narrow change in the seed layer thickness. This studydemonstrates that ALD technique can produce densely packed, virtually defect-free, and highly uniform seed layers and twodistinctive processes may form ZnO as the final product via the initial nucleation step consisting of the reaction between Zn2+ions from respective zinc precursors and OH− ions from H2O. KCI Citation Count: 0
In this study, the reclaimed polypropylene (RPP) and waste ground rubber tire (WGRT) were used to simulate the thermoplastic vulcanizate (TPV) for cost reduction and resources recycling. Also, we ...examined the effects of dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexane (DTBPH) as peroxide type cross-linking agents to enhance the properties of TPV`s. The components of RPP and WGRT were fixed at 30 and 70 wt%, and DCP and DTBPH were added in the concentrations from 0.5 to 1.5 phr, respectively. RPP/WGRT composites with different contents of DCP and DTBPH were prepared by a modular intermeshing co-rotating twin screw extruder. The Young`s modulus of composites were decreased with increasing peroxides contents. On the other hand, tensile strength, elongation at break, and impact strength of the composites were increased with peroxide contents. We also confirmed that interfacial adhesion between RPP and WGRT was considerably improved by adding the peroxides. Taken together, DTBPH added RPP/WGRT composites exhibited better mechanical properties rather than those of DCP added composites.
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