• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.3
• /
• pp.165-170
• /
• 2018

In this study, double-layered TCO (transparent conductive oxide) films were produced by depositing two distinct TCO materials: $SnO_2$ works as an n-type layer and ITO (indium-doped tin oxide) serves as a transparent conductor. Both transparent conductive oxide-films were sequentially deposited by sputtering. The electrical and optical properties of single-layered TCO films ($SnO_2$) and double-layered TCO ($ITO/SnO_2$) films were investigated. A TCO-embedding photodetector was realized through the formation of an $ITO/SnO_2/p-Si/Al$ layered structure. The remarkably high rectifying ratio of 400.64 was achieved with the double-layered TCO device, compared to 1.72 with the single-layered TCO device. This result was attributed to the enhanced electrical properties of the double-layered TCO device. With respect to the photoresponses, the photocurrent of the double-layered TCO photodetector was significantly improved: 1,500% of that of the single-layered TCO device. This study suggests that, due to the electrical and optical benefits, double-layered TCO films are effective for enhancing the photoresponses of TCO photodetectors. This provides a useful approach for the design of photoelectric devices, including solar cells and photosensors.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.278-278
• /
• 2016

Solution-processed metal-oxide semiconductors have been considered as the next generation semiconducting materials for transparent and flexible electronics due to their high electrical performance. Moreover, since the oxide semiconductors show high sensitivity to light illumination and possess persistent photoconductivity (PPC), these properties can be utilized in realizing optical memory devices, which can transport information much faster than the electrons. In previous works, metal-oxide semiconductors are utilized as a memory device by using the light (i.e. illumination does the "writing", no-gate bias recovery the "reading" operations) [1]. The key issues for realizing the optical memory devices is to have high photoconductivity and a long life time of free electrons in the oxide semiconductors. However, mono-layered indium-zinc-oxide (IZO) and mono-layered indium-gallium-zinc-oxide (IGZO) have limited photoconductivity and relaxation time of 570 nA, 122 sec, 190 nA and 53 sec, respectively. Here, we boosted up the photoconductivity and relaxation time using a double-layered IZO/IGZO active layer structure. Solution-processed IZO (top) and IGZO (bottom) layers are prepared on a Si/SiO2 wafer and we utilized the conventional thermal annealing method. To investigate the photoconductivity and relaxation time, we exposed 9 mW/cm2 intensity light for 30 sec and the decaying behaviors were evaluated. It was found that the double-layered IZO/IGZO showed high photoconductivity and relaxation time of 28 uA and 1048 sec.

• Journal of Information Display
• /
• v.13 no.2
• /
• pp.61-66
• /
• 2012

The double-layered Ti/Si barrier metal is demonstrated for the source/drain Cu interconnections in oxide semiconductor thin-film transistors (TFTs). The transmission electromicroscopy and ion mass spectroscopy analyses revealed that the double-layered barrier structure suppresses the interfacial reaction and the interdiffusion at the interface after thermal annealing at $350^{\circ}C$. The underlying Si layer was found to be very useful for the etch stopper during wet etching for the Cu/Ti layers. The oxide TFTs with a double-layered Ti/Si barrier metal possess excellent TFT characteristics. It is concluded that the present barrier structure facilitates the back-channel-etch-type TFT process in the mass production line, where the four- or five-mask process is used.

• Proceedings of the IEEK Conference
• /
• 2002.06b
• /
• pp.225-228
• /
• 2002

The adhesion effect between the oxide layer and the metal layer has been studied by RTP anneal. Two types of oxides, BPSG and P-TEOS, were used as a bottom layer under multi-layered metal film. We observe the interface between oxide and metal layer using SEM (scanning electron microscopy), TEM (transmission electron microscopy), AES (auger electron spectroscopy). Adhesion failure was occurred by interfacial reaction between the BPSG oxide and the multi-layered metal film at 650"C RTP anneal. The phosphorus rich layer was observed at interface between BPSG oxide and metal layer by AES and TEM measurements. On the other hand adhesion was a)ways good in the sample used P-TEOS oxide as a bottom layer. We have known that adhesion between BPSG and multi-layered metal film was improved when the sample was annealed below $650^{\circ}C$.TEX>.

• Journal of Power System Engineering
• /
• v.11 no.2
• /
• pp.44-50
• /
• 2007

The oxidation behavior of commercial pure titanium is investigated in the temperature range of $727^{\circ}C{\sim}950^{\circ}C$ in mixed gases. The weight change is measured by TGA during oxidation in mixed gases. The oxidation behavior indicated by weight gain or the growth of oxide layer is based on the linear rate law at high temperatures. The structure of the oxide scale formed during oxidation is analysed by optical microscopy, electron probe microanalyzer, scanning electron microscope and x-ray diffraction. Oxide scales have a $TiO_2$ structure, and are constituted with multi-layered or two layered porous external one and a dense internal one. Ti-O solid solution region is formed at the interface of metal and scale layer. The formation of oxide scale is influenced by the oxidation temperature, time, crystal structure and the condition of atmosphere.

• Korean Journal of Materials Research
• /
• v.22 no.5
• /
• pp.237-242
• /
• 2012

We report on the NO gas sensing properties of Al-doped zinc oxide-carbon nanotube (ZnO-CNT) wire-like layered composites fabricated by coaxially coating Al-doped ZnO thin films on randomly oriented single-walled carbon nanotubes. We were able to wrap thin ZnO layers around the CNTs using the pulsed laser deposition method, forming wire-like nanostructures of ZnO-CNT. Microstructural observations revealed an ultrathin wire-like structure with a diameter of several tens of nm. Gas sensors based on ZnO-CNT wire-like layered composites were found to exhibit a novel sensing capability that originated from the genuine characteristics of the composites. Specifically, it was observed by measured gas sensing characteristics that the gas sensors based on ZnO-CNT layered composites showed a very high sensitivity of above 1,500% for NO gas in dry air at an optimal operating temperature of $200^{\circ}C$; the sensors also showed a low NO gas detection limit at a sub-ppm level in dry air. The enhanced gas sensing properties of the ZnO-CNT wire-like layered composites are ascribed to a catalytic effect of Al elements on the surface reaction and an increase in the effective surface reaction area of the active ZnO layer due to the coating of CNT templates with a higher surface-to-volume ratio structure. These results suggest that ZnO-CNT composites made of ultrathin Al-doped ZnO layers uniformly coated around carbon nanotubes can be promising materials for use in practical high-performance NO gas sensors.

• Journal of the Korean Ceramic Society
• /
• v.51 no.4
• /
• pp.295-299
• /
• 2014

Electrical conductivities of complex perovskites, layered perovskite and Sr doped layered perovskite oxides were measured and analyzed for cathode materials of Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The electrical conductivities of $Sm_{1-x}Sr_xCoO_{3-\delta}$ (x = 0.3 and 0.7) exhibit a metal-insulator transition (MIT) behavior as a function of temperature. However, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ (SSC55) shows metallic conductivity characteristics and the maximum electrical conductivity value compared to the values of $Pr_{0.5}Sr_{0.5}CoO_{3-\delta}$ (PSC55) and $Nd_{0.5}Sr_{0.5}CoO_{3-\delta}$ (NSC55). The electrical conductivity of $SmBaCo_2O_{5+\delta}$ (SBCO) exhibits a MIT at about $250^{\circ}C$. The maximum conductivity is 570 S/cm at $200^{\circ}C$ and its value is higher than 170 S/cm over the whole temperature range tested. $SmBa_{0.5}Sr_{0.5}Co_2O_{5+\delta}$ (SBSCO), 0.5 mol% Sr and Ba substituted at the layered perovskite shows a typically metallic conductivity that is very similar to the behavior of the SSC55 cathode, and the maximum and minimum electrical conductivity in the SBSCO are 1280 S/cm at $50^{\circ}C$ and 280 S/cm at $900^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.302.1-302.1
• /
• 2016

Solution-processed amorphous metal-oxide thin-film transistors (TFTs) are considered as promising candidates for the upcoming transparent and flexible electronics due to their transparent property, good performance uniformity and possibility to fabricate at a low-temperature. In addition, solution processing metal oxide TFTs may allow non-vacuum fabrication of flexible electronic which can be more utilizable for easy and low-cost fabrication. Recently, for high-mobility oxide TFTs, multi-layered oxide channel devices have been introduced such as superlattice channel structure and heterojunction structure. However, only a few studies have been mentioned on the bias illumination stress in the multi- layered oxide TFTs. Therefore, in this research, we investigated the effects of bias illumination stress in solution-processed bilayer oxide TFTs which are fabricated by the deep ultraviolet photochemical activation process. For studying the electrical and stability characteristics, we implemented positive bias stress (PBS) and negative bias illumination stress (NBIS). Also, we studied the electrical properties such as field-effect mobility, threshold voltage ($V_T$) and subthreshold slop (SS) to understand effects of the bilayer channel structure.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.47.2-47.2
• /
• 2011

High-efficient transparent conductive oxide (TCO) film-embedding Si heterojunction solar cells were fabricated. An improved crystalline indium-tin-oxide (ITO) film was grown on an Al-doped ZnO (AZO) template upon hetero-epitaxial growth. This double TCO-layered Si solar cell provided significantly enhanced efficiency of 9.23 % as compared to the single TCO/Si devices. The effective arrangement of TCO films (ITO/AZO) provides a good interface, resulting in the enhanced photovoltaic performances. It discusses TCO film arrangement scheme for efficient TCO-layered heterojunction solar cells.

• Proceedings of the KIEE Conference
• /
• 1988.07a
• /
• pp.328-331
• /
• 1988

Sealed Interface Local Oxidation (SILO) technology has been investigated using a nitride/oxide/nitride three-layered sandwich structure. P-type silicon substrate was either nitrided by rapid thermal processing, or silicon nitride was deposited by LPCVD method. A three-layered sandwich structure was patterned either by reactive ion etch (RIE) mode or by plasma mode. Sacrificial oxidation conditions were also varied. Physical characterization such as cross-section analysis of field oxide, and electrical characterization such as gate oxide integrity, junction leakage and transistor behavior were carried out. It was found that bird's beak was nearly zero or below 0.1um, and the junction leakages in plasma mode were low compared to devices of the same geometry patterned in RIE mode, and gate oxide integrity and transistor behavior were comparable. Conclusively, SILO process is compatible with conventional local oxidation process.