Analysis of ZnS and MgF2 layered nanostructures grown by glancing angle deposition for optical design.

This study investigated the multilayer growth and properties of ZnS and MgF2 using glancing angle deposition. We used deposition angles of 85°-89° for ZnS and 70°-88° for MgF2 to obtain the structural properties. The film properties primarily followed Tait's rule with a deposition angle of less than 87° in the vapor flux. However, film growth with a vapor flux angle of 88°-89° followed the tangent rule. Mathematical and cross-sectional scanning electron microscopy examinations found a transition point for the growth mechanisms at 87°, which comes from an extreme angle property for glancing angle deposition. We also performed mathematical derivations for the well-known empirical formula of the tangent rule and its generalized version. To stabilize the interface structure and surface roughness of multilayer structures, film growth at slightly tilted angles is recommended. Based on these results, an optical structure was designed, fabricated, and analyzed for a 550 nm wavelength pass filter on a glass substrate.

Performance of thyristor memory device formed by a wet etching process.

Thyristor random access memory without a capacitor has been highlighted for its significant potential to replace current dynamic random access memory. We fabricated a two-terminal (2-T) thyristor by wet chemical etching techniques on n+-p-n-p+ silicon epitaxial layers, which have the proper thicknesses and carrier concentrations, as provided by technology computer-aided design simulation. The etched features such as etch rate, surface roughness, and morphologies, in a potassium hydroxide (KOH) and an isotropic etchant, were compared. The type of silicon etchant strongly affected the etched shapes of the side wall and therefore critically influenced the device performance with varying turn-on voltages. The turn-on voltage of thyristor fabricated with a KOH solution showed a consistent tendency of operation voltage in the range of 2.2-2.5 V regardless of the cell size, while the thyristor formulated with isotropic etchant had an operation voltage which increased from about 2.3-4.4 V as the device dimension decreased from 200 µm to 10 µm. The optimized 2-T thyristor showed a memory window of about 2 V, a nearly zero-subthreshold swing, and a current on-off ratio of about 104-105.

Assessment of American Bullfrog (Lithobates catesbeianus) spreading in the Republic of Korea using rule learning of elementary cellular automata.

The spread of American Bullfrog has a significant impact on the surrounding ecosystem. It is important to study the mechanisms of their spreading so that proper mitigation can be applied when needed. This study analyzes data from national surveys on bullfrog distribution. We divided the data into 25 regional clusters. To assess the spread within each cluster, we constructed temporal sequences of spatial distribution using the agglomerative clustering method. We employed Elementary Cellular Automata (ECA) to identify rules governing the changes in spatial patterns. Each cell in the ECA grid represents either the presence or absence of bullfrogs based on observations. For each cluster, we counted the number of presence location in the sequence to quantify spreading intensity. We used a Convolutional Neural Network (CNN) to learn the ECA rules and predict future spreading intensity by estimating the expected number of presence locations over 400 simulated generations. We incorporated environmental factors by obtaining habitat suitability maps using Maxent. We multiplied spreading intensity by habitat suitability to create an overall assessment of bullfrog invasion risk. We estimated the relative spreading assessment and classified it into four categories: rapidly spreading, slowly spreading, stable populations, and declining populations.

Structural properties of indium tin oxide thin films by glancing angle deposition method.

We have studied the structural and optical properties of indium tin oxide (ITO) films deposited on sapphire substrates by electron beam evaporator with glancing angle deposition method. The ITO films were grown with different deposition angles of 0 degrees, 30 degrees, 45 degrees, 60 degrees at fixed deposition rate of 3 angstroms/s and with deposition rates of 2 angstroms/s, 3 angstroms/s, and 4angstroms/s at deposition angle of 45 degrees, respectively. From analysis of ellipsometry measurements, it appears that the void fraction of the films increased and their refractive indices decreased from 2.18 to 1.38 at the wavelength of 500 as increasing the deposition angle. The refractive index in the wavelength ranges of 550 nm-800 nm also depends on the deposition rates. Transmittance of ITO film with 235-nm-thickness grown at 60 degrees was covered about 20-80%, and then it was increased in visible wavelength range with increase of deposition angle.

Work Function Modification of Tungsten-Doped Indium Oxides Deposited by the Co-Sputtering Method.

We have studied the work function modification of tungsten-doped indium oxides (IWOs) through the co-sputtering of indium oxide (In2O3) and indium tungsten oxide (In2O3 80 wt% + WO3 20 wt%) via a radio frequency (RF) magnetron sputtering system. By controlling the elemental deposition of IWOs, the resultant work functions varied from 4.37 eV to 4.1 eV. The IWO thin films showed excellent properties for application as transparent conducting oxide materials in the region of 0 to 2.43 at.% of tungsten versus the total metal content. The carrier concentration of n-type IWO thin films varied from 8.39 x 10(19) cm(-3) to 8.58 x 10(21) cm(-3), while the resistivity varied from 3.15 x 10(-4) Ωcm to 2.26 x 10(-3) Ωcm. The largest measured optical band gap was 3.82 eV determined at 2.43 at.% of tungsten atoms relative to the total amount of metal atoms, while the smallest optical band gap was 3.6 eV at 4.78 at.% of tungsten. IWO films containing more than 2.43 at.% of tungsten atoms relative to the total number of metal atoms revealed an average transmittance of over 80% within the visible light region.