• Journal of the Korean Society for Heat Treatment
• /
• v.26 no.2
• /
• pp.55-58
• /
• 2013

ITO thin films deposited on glass substrate with RF magnetron sputtering were vacuum annealed at 100, 200 and $300^{\circ}C$ for 30 minutes and then effect of annealing temperature on the structural, electrical and optical properties of ITO films were investigated. The structural properties are strongly related to annealing temperature. The annealed films above $100^{\circ}C$ are grown as a hexagonal wurtzite phase and the largest grain size is observed in the films annealed at $300^{\circ}C$. The electrical resistivity also decreases as low as $4.65{\times}10^{-4}{\Omega}cm$ with a increase in annealing temperature and ITO film annealed at $300^{\circ}C$ shows the lowest sheet resistance of $43.6{\Omega}/{\Box}$. The optical transmittance in a visible wavelength region also depends on the annealing temperature. The films annealed at $300^{\circ}C$ show higher transmittance of 80.6% than those of the films prepared in this study.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.293.1-293.1
• /
• 2016

Various materials including conductive, dielectric, and semi-conductive materials, constitute suitable candidates for printed electronics. Metal nanoparticles (e.g. Ag, Cu, Ni, Au) are typically used in conductive ink. However, easily oxidized metals, such as Cu, must be processed at low temperatures and as such, photonic sintering has gained significant attention as a new low-temperature processing method. This method is based on the principle of selective heating of a strongly absorbent film, without light-source-induced damage to the transparent substrate. However, Cu nanoparticles used in inks are susceptible to the growth of a native copper-oxide layer on their surface. Copper-oxide-nanoparticle ink subjected to a reduction mechanism has therefore been introduced in an attempt to achieve long-term stability and reliability. In this work, a flash-light sintering process was used for the reduction of an inkjet-printed Cu(II)O thin film to a Cu film. Using a photographic lighting instrument, the intensity of the light (or intense pulse light) was controlled by the charged power (Ws). The resulting changes in the structure, as well as the optical and electrical properties of the light-irradiated Cu(II)O films, were investigated. A Cu thin film was obtained from Cu(II)O via photo-thermal reduction at 2500 Ws. More importantly, at one shot of 3000 Ws, a low sheet resistance value ($0.2527{\Omega}/sq.$) and a high resistivity (${\sim}5.05-6.32{\times}10^{-8}{\Omega}m$), which was ~3.0-3.8 times that of bulk Cu was achieved for the ~200-250-nm-thick film.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.196.1-196.1
• /
• 2016

TCO(Transparent Conducting Oxide) on flat glass is used in thin-film photovoltaic cell, flat-panel display. Nowadays, Corning(R) Willow Glass(R), known as flexible substrate, has attracted much attention due to its many advantages such as reliable roll-to-roll glass processing, high-quality flexible electronic devices, high temperature process. Also, it can be an alternative to flexible polymer substrates which have their poor stability and degradation of electrical and optical qualities. For application on willow glass, the flexibility, electrical, optical properties can be greatly influenced by the TCO thin film thickness due to the inherent characterization of thin film in nanoscale. It can be expected that while thick TCO layer causes poor transparency, its sheet resistance become low. Also, rarely reports were focusing on the influence of flexible properties by varying TCO thickness on flexible glass. Therefore, it is very important to optimize TCO thickness on flexible Willow glass. In this study, Ti-ZnO thin films, with different thickness varied from 0 nm to 50 nm, were deposited on the flexible willow glass by atomic layer deposition (ALD). The flexible, electrical and optical properties were investigated, respectively. Also, these properties of Ti-doped ZnO thin films were compared with un-doped ZnO thin film. Based on the results, when Ti-ZnO thin films thickness increased, resistivity decreased and then saturated; transmittance decreased. The Figure of Merit (FoM) and flexibility was the highest when Ti-ZnO thickness was 40nm. The flexible, electrical and optical properties of Ti-ZnO thin films were better than ZnO thin film at the same thickness.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.235.2-235.2
• /
• 2015

The front transparent conductive oxide (TCO) films must exhibit good transparency, low resistivity and excellent light scattering properties for high efficiency amorphous silicon (a-Si) thin film solar cells. The light trapping phenomenon is limited due to non-uniform and low aspect ratio of the textured glass [1]. We present the low cost electrochemically deposited uniform zinc oxide (ZnO) nanorods with various aspect ratios for a-Si thin film solar cells. Since the major drawback of the electrochemically deposited ZnO nanorods was the high sheet resistance and low transmittance that was overcome by depositing the RF magnetron sputtered AZO films as a seed layer with various thicknesses [2]. The length and diameters of the ZnO nanorods was controlled by varying the deposition conditions. The length of ZnO nanorods were varied from 400 nm to $2{\mu}m$ while diameter was kept higher than 200 nm to obtain different aspect ratios. The uniform ZnO nanorods showed higher haze ratio as compared to the commercially available FTO films. We also observed that the scattering in the longer wavelength region was favored for the high aspect ratio of ZnO nanorods and much higher aspect ratios degraded the light scattering phenomenon. Therefore, we proposed our low cost and uniform ZnO nanorods for the high efficiency of thin film solar cells.

• Korean Journal of Materials Research
• /
• v.14 no.9
• /
• pp.676-681
• /
• 2004

In-situ observation in SBM on the microfracture behavior of coating layer was performed for GA steel sheets that have various Fe contents and thickness of coating layer. In case of cross sectional side of coating layer that was in a tensile stress state during bending, fine perpendicular crack pre-induced during galvannealing grew and propagated rapidly toward the coating surface with the increase of strain. And then it grew and propagated along the ${\Gamma}/Fe$ matrix interface, and combined with the nearest another perpendicular crack. Consequently, flaking occurred. The more Fe content and thickness of coating layer increased, the more average crack interval and flaking resistivity increased. Exfoliation was little observed at coating surface in a tensile stress state.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.438-439
• /
• 2013

Microelectronic devices의 접촉저항의 향상을 위해 Metal silicides의 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 지난 수십년에 걸쳐, Ti silicide, Co silicide, Ni silicide 등에 대한 개발이 이루어져 왔으나, 계속적인 저저항 접촉 소재에 대한 요구에 의해 최근에는 Rare earth silicide에 관한 연구가 시작되고 있다. Rare-earth silicide는 저온에서 silicides를 형성하고, n-type Si과 낮은 schottky barrier contact (~0.3 eV)를 이룬다. 또한, 비교적 낮은 resistivity와 hexagonal AlB2 crystal structure에 의해 Si과 좋은 lattice match를 가져 Si wafer에서 high quality silicide thin film을 성장시킬 수 있다. Rare earth silicides 중에서 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 낮은 schottky barrier 응용에서 쓰이고 있다. 이로 인해, n-channel schottky barrier MOSFETs의 source/drain으로써 주목받고 있다. 특히 ytterbium과 molybdenum co-deposition을 하여 증착할 경우 thin film 형성에 있어 안정적인 morphology를 나타낸다. 또한, ytterbium silicide와 마찬가지로 낮은 면저항과 electric work function을 갖는다. 그러나 ytterbium silicide에 molybdenum을 화합물로써 높은 농도로 포함할 경우 높은 schottky barrier를 형성하고 epitaxial growth를 방해하여 silicide film의 quality 저하를 야기할 수 있다. 본 연구에서는 ytterbium과 molybdenum의 co-deposition에 따른 silicide 형성과 전기적 특성 변화에 대한 자세한 분석을 TEM, 4-probe point 등의 다양한 분석 도구를 이용하여 진행하였다. Ytterbium과 molybdenum을 co-deposition하기 위하여 기판으로 $1{\sim}0{\Omega}{\cdot}cm$의 비저항을 갖는 low doped n-type Si (100) bulk wafer를 사용하였다. Native oxide layer를 제거하기 위해 1%의 hydrofluoric (HF) acid solution에 wafer를 세정하였다. 그리고 고진공에서 RF sputtering 법을 이용하여 Ytterbium과 molybdenum을 동시에 증착하였다. RE metal의 경우 oxygen과 높은 반응성을 가지므로 oxidation을 막기 위해 그 위에 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, 진공 분위기에서 rapid thermal anneal(RTA)을 이용하여 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium silicides를 형성하였다. 전기적 특성 평가를 위한 sheet resistance 측정은 4-point probe를 사용하였고, Mo doped ytterbium silicide와 Si interface의 atomic scale의 미세 구조를 통한 Mo doped ytterbium silicide의 형성 mechanism 분석을 위하여 trasmission electron microscopy (JEM-2100F)를 이용하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.7
• /
• pp.563-568
• /
• 2012

Indium tin oxide (ITO) films were prepared using radio frequency (RF) magnetron sputtering method, magnets were equipped near the target in the sputter to bring the plasma near the target. The effect of magnetic field that brings the plasma near the substrate was compared with that of substrate heating. The effect of substrate heating on the grain size of the ITO thin film was larger than that of the magnetic field. However, the grain size of the ITO thin film was larger when the magnetic field was applied near the substrate during the sputtering process than when the substrate was not heated and the magnetic field was not applied. If stronger magnetic field is applied near the substrate during sputtering, it can be expected that the ITO thin film with good electrical conductivity and high transparency is obtained at low substrate temperature. When magnetic field of 90 Gauss was applied near the substrate during sputtering, the mobility of the ITO thin film increased from 15.2 $cm^2/V.s$ to 23.3 $cm^2/V.s$, whereas the sheet resistivity decreased from 7.68 ${\Omega}{\cdot}cm$ to 5.11 ${\Omega}{\cdot}cm$.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.22 no.4
• /
• pp.76-83
• /
• 1985

Mo2N/Mo double layer which is to be used for gate of the RMOS (refractory metal oxide semiconductor) and interconnection material has been formed by means of low temperature r.f. reactive sputtering in Ar and N2 mixture. The sheet .esistance of 1 000$\AA$Mo2 N/4000$\AA$Mofilm was about 1.20-1.28 ohms/square, which is about an order of magnitude lower than that of polysilicon film. The workfunction difference naE between MO2N/MO layer and (100) p-Si with 6-9 ohm'cm resistivity obtained from C-V plots was about -0.30ev, and the fixed charge density Qss/q in the oxide was about 2. Ix1011/cm2. To evaluate the signal transfer delay time per inverter stage, an integrated ring oscillator circuit consisting of 45-stage inverters was fabricated using the polysilicon gate NMOS process. The signal transfer delay time per inverter stage obtained in this experiment was about 0.8 nsec

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.458.2-458.2
• /
• 2014

We have demonstrated that simple brush-painted Ti-doped $In_2O_3$(TIO) films can be used as a cost effective transparent anodes for organic solar cells (OSCs). We examined the RTA effects on the electrical, optical, and structural properties of the brush painted TIO electrodes. By the direct brushing of TIO nanoparticle ink and rapid thermal annealing (RTA), we can simply obtain TIO electrodes with a low sheet resistance of 28.25 Ohm/square and a high optical transmittance of 85.48% under atmospheric ambient conditions. Furthermore, improvements in the connectivity of the TIO nano-particles in the top region during the RTA process play an important role in reducing the resistivity of the brush-painted TIO anode. In particular, the brush painted TIO films showed a much higher mobility ($33.4cm^2/V-s$) than that of previously reported solution-process transparent oxide films ($1{\sim}5cm^2/V-s$) due to the effects of the Ti dopant with higher Lewis acid strength (3.06) and the reduced contact resistance of TIO nanoparticles. The OSCs fabricated on the brush-painted TIO films exhibited cell-performance with an open circuit voltage (Voc) of 0.61 V, shot circuit current (Jsc) of $7.90mA/cm^2$, fill factor (FF) of 61%, and power conversion efficiency (PCE) of 2.94%. This indicates that brush-painted TIO film is a promising cost-effective transparent electrode for printing-based OSCs with its simple process and high performance.

• Current Photovoltaic Research
• /
• v.3 no.3
• /
• pp.101-105
• /
• 2015

ZnO is gathering great interest for large square optoelectrical devices of flat panel display (FHD) and solar cell as a transparent conductive oxide (TCO). Herewith, Mg and IIIA (Al, In) co-doped ZnO films were prepared on SLG substrate using RF magnetron sputtering system. The effect of variation of atomic weight % of Mg and ZnO have been investigated. The atomic weight % Al and In are of 3% and kept constant throughout. The numbers of samples were prepared according to their different contents, which are $M_{3%}AZO_{94%}$, $M_{4%}AZO_{93%}-(MAZO)$ and $M_{3%}IZO_{94%}$, $M_{4%}IZO_{93%}-(MIZO)$ respectively. A RF power of 225 W and working pressure of 6 m Torr was used for the deposition at $300^{\circ}C$. All of the two thin film show good uniformity in field emission scanning electron microscopy image. $M_{3%}AZO_{94%}$ thin film shows overall better performance among the all. The film shows the best lowest resistivity, carrier concentration, mobility and Sheet resistance and is found to be are of $8.16{\times}10^{-4}{\Omega}cm$, $4.372{\times}10^{20}/cm^3$, $17.5cm^2/vs$ and $8.9{\Omega}/sq$ respectively. Also $M_{3%}AZO_{94%}$ thin film shows the relatively high optical band gap energy of 3.7 eV with high transmittance more than 80% in visible region required for the better solar cell performance.