Hyukhyun Ryu

UV and Visible Electroluminescence From a

A Sn-doped Ga₂O₃ thin film was deposited on a n⁺-Si substrate by metal-organic chemical vapor deposition. The Ga₂O₃ film was found to be amorphous-like and exhibited n-type conduction with Sn doping. Room-temperature electroluminescence was clearly observed from the Sn:Ga₂O₃/n⁺ -Si diode, including an ultraviolet (UV) emission at ~ 370 nm, a yellow emission at ~ 580 nm, and a red emission at ~ 680 nm. The UV emission is assigned to the transition from Sn_Ga donor to the <i>V</i>_Ga acceptor, whereas the visible emissions were assigned to be related to the dangling bond defects.

\hbox{Sn:Ga}_{2}\hbox{O}_{3}/\hbox{n}^{+}\hbox{-Si}

In this study, the structural properties of ZnO nanostructures grown by plasma-enhanced vapor phase transport (PEVPT) were investigated. Plasma-treated oxygen gas was used as the oxygen source for the ZnO growth. The structural properties of ZnO nanostructures grown for different durations were measured by scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The authors comprehensively analyzed the growth of the ZnO nanostructures with different growth durations both with and without the use of plasma-treated oxygen gas. It was found that PEVPT has a significant influence on the growth of the ZnO nanorods. PEVPT with plasma-treated oxygen gas facilitated the generation of nucleation sites, and the resulting ZnO nanorod structures were more vertical than those prepared by conventional VPT without plasma-treated oxygen gas. As a result, the ZnO nanostructures grown using PEVPT showed improved structural properties compared to those prepared by the conventional VPT method.

Heterojunction by Metal–Organic Chemical Vapor Deposition

The thermal stability of nickel silicide (NiSi) on a silicon-on-insulator (SOI) substrate after postsilicidation annealing (550–700 °C) is discussed in this paper. Nickel silicide technology, used for nanoscale complementary metal oxide semiconductor (CMOS) field-effect transistor (FET) devices, has a fundamental problem of thermal stability. Three different Pd concentrations in Ni–Pd alloy, 1, 5, and 10 at. %, were used to study the thermal stability of nickel silicide formed by a silicidation process. The Ni–Pd (10%) sample showed good thermal stability upon annealing at temperatures up to 700 °C for 30 min. Only a low-resistivity mononickel silicide (NiSi) phase peak was observed by X-ray diffraction (XRD) measurement, which was confirmed by Auger electron spectroscopy (AES) analysis. Uniformly formed nickel silicide with a good interface profile was obtained using the Ni–Pd (10%) sample according to field-emission scanning electron microscopy (FE-SEM) measurement. However, the Ni–Pd (5%) sample produced high-resistivity nickel disilicide (NiSi2) after annealing at 650 °C for 30 min. Four different layer structures, Ni, Ni/TiN, Ni/Co/TiN, and Ni–Pd (10%)/Co/TiN, were also used for further study. Among these structures, the Ni–Pd (10%)/Co/TiN layer structure had good thermal stability upon annealing at temperatures up to 700 °C, while the other structures deteriorated due to agglomeration above 550 °C.

ZnO nanorod growth by plasma-enhanced vapor phase transport with different growth durations

The effects of a strained silicon layer on the thermal stability of nickel (germano)silicide for nanoscale complementary metal oxide semiconductor field-effect transistor (CMOSFET) devices are discussed in this study. Three different thicknesses, 5, 13, and 40 nm, of silicon layers on silicon germanium (SiGe) were prepared for this experiment. The effects of the silicidation rapid thermal annealing (RTA) temperature and postsilicidation annealing temperature for the different silicon layer thicknesses were studied. For comparison, a bulk silicon substrate and a SiGe substrate were also used. Silicides with the thin strained silicon layers (5 and 13 nm) on SiGe showed good thermal stability in this study. However, the other silicides using bulk silicon, 40-nm-thick silicon on SiGe, and the SiGe substrate underwent degradation due to silicide agglomeration during annealing. A SiO2 layer was found on the silicide using the SiGe substrate. In this study, several analysis methods such as four-point probe measurement, field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Auger electron spectroscopy (AES) were used for detailed study.

Study of Nickel Silicide Thermal Stability Using Silicon-on-Insulator Substrate for Nanoscale Complementary Metal Oxide Semiconductor Field-Effect Transisor Device

In this study, the effects of precursor concentration on the zinc oxide (ZnO) nanorods grown on flexible polyethylen terephthalate (PET) substrate with and without buffer layer were discussed. The concentration was varied from 0.05 to 0.5M. When we inserted buffer layer before hydrothermally growth of ZnO, better aligned ZnO nanorods were grown. At relatively middle concentration (from 0.2 to 0.3M), well-aligned ZnO nanorods were grown on PET substrate with and without buffer layer. The crystal structural properties and surface morphologies were examined by x-ray diffraction (XRD), and field emission scanning electron microscope (FE-SEM), respectively.

Effects of Strained Silicon Layer on Nickel (Germano)silicide for Nanoscale Complementary Metal Oxide Semiconductor Field-Effect Transistor Device

Vertically aligned TiO2 nanorods were grown on a fluorine-doped tin oxide (FTO) substrate covered with a TiO2 buffer layer by using the hydrothermal method with various titanium precursor concentrations. In this study, the effects of the precursor concentration on the morphological, structural, optical and photoelectrochemical properties of TiO2 nanorods were investigated. We observed that photoelectrochemical properties were mainly dependent on the nanorod length, surface area, transmittance and (002) XRD peak intensity, which indicates the oriented growth of the TiO2 nanorods perpendicular to the substrate. As a result, the sample grown from a 0.09 M precursor solution, which grew vertically and had the highest surface area, showed the highest photocurrent density, 0.733 mA/cm2 (at 1.0 V vs. SCE). Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to characterize the morphology of the nanorods, X-ray diffraction (XRD) was used to detect the structural properties of the nanorods, UV-visual spectroscopy was used to measure the optical properties, and analysis with a three-electrode potentiostat was used to measure the photoelectrochemical properties.

Effects of precursor concentration on ZnO nanorods grown on flexible PET substrate by hydrothermal synthesis

In this study, the effects of an annealed buffer layer with different thickness on heterojunction diodes based on the ZnO/ZnO/p-Si(111) systems were reported. The effects of an annealed buffer layer with different thickness on the structural, optical, and electrical properties of zinc oxide (ZnO) films on p-Si(111) were also studied. Before zinc oxide (ZnO) deposition, different thicknesses of ZnO buffer layer, 10 nm, 30 nm, 50 nm and 70 nm, were grown on p-Si(111) substrates using a radio-frequency sputtering system; samples were subsequently annealed at for 10 minutes in in a horizontal thermal furnace. Zinc oxide (ZnO) films with a width of 280nm were also deposited using a radio-frequency sputtering system on the annealed ZnO/p-Si (111) substrates at room temperature; samples were subsequently annealed at for 30 minutes in . In this experiment, the structural and optical properties of ZnO thin films were studied by XRD (X-ray diffraction), and room temperature PL (photoluminescence) measurements, respectively. Current-voltage (I-V) characteristics were measured with a semiconductor parameter analyzer. The thermal tensile stress was found to decrease with increasing buffer layer thickness. Among the ZnO/ZnO/p-Si(111) diodes fabricated in this study, the sample that was formed with the condition of a 50 nm thick ZnO buffer layer showed a strong c-axis preferred orientation and I-V characteristics suitable for a heterojunction diode.

Study of the morphological, optical, structural and photoelectrochemical properties of TiO2 nanorods grown with various precursor concentrations

In this study, the effects of ZnO buffer layer thickness and annealing temperature on the heterojunction diode, ZnO/b-ZnO/p-Si(111), were reported. The effects of those on the structural and electrical properties of zinc oxide (ZnO) films on ZnO buffered p-Si (111) substrate were also studied. Structural properties of ZnO thin films were studied by X-ray diffraction and I-V characteristics were measured by a semiconductor parameter analyzer. ZnO thin films with 70 nm thick buffer layer and annealing temperature of showed the best c-axis preferred orientation. The best electrical property was found at the condition of buffer layer annealing temperature of and 50nm thick ZnO buffer layer (resistivity: , carrier concentration: ). The I-V characteristics for ZnO/b-ZnO/p-Si(111) heterojunction diode were improved with increasing buffer layer thickness at buffer layer annealing temperature of .

Dependence of the Heterojunction Diode Characteristics of ZnO/ZnO/p-Si(111) on the Buffer Layer Thickness

ZnO thin films were deposited on polyethersurfone (PES) substrates by atomic layer deposition (ALD). We investigated the effects of O2 plasma pretreatment from 0W to 100W before the ZnO growth. When the plasma power was increased, the PET substrate surface roughness was also increased. However, the surface roughness of ZnO on the roughest PET substrate with maximum plasma power pretreatment showed the smoothest value. The XRD (002) peak intensity of ZnO was increased with increasing plasma power. The morphologies of ZnO thin films were measured by atomic force microscope (AFM) and scanning electron microscope (SEM). And the crystal structural properties were analyzed by x-ray diffraction (XRD) method.

Dependence of the Diode Characteristics of ZnO/b-ZnO/p-Si(111) on the Buffer Layer Thickness and Annealing Temperature

We systematically investigated the effects of InAs coverage variation, two-step annealing and an asymmetric InGaAs quantum well (QW) on the structural and optical characteristics of InAs quantum dots (QDs) by using atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL) measurement. The transition of size distribution of InAs QDs from bimodal to multi-modal was noticeably observed with increasing InAs coverage. By means of two-step annealing, it is found that significant narrowing of the luminescence linewidth (from 132 to 31 meV) from the InAs QDs occurs together with about 150 meV blueshift, compared to as-grown InAs QDs. Finally, the InAs QDs emitting at longer wavelength of with narrow linewidth were grown by an asymmetric InGaAs QW. The excited-state transition for the InAs QDs with an asymmetric InGaAs QW was not noticeably observed due to the large energy-level spacing between the ground states and the first excited states. The InAs QDs with an asymmetric InGaAs QW will be promising for the device applications such as optical-fiber communication.