• Journal of the Korean Vacuum Society
• /
• v.17 no.6
• /
• pp.528-537
• /
• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.

• Journal of the Korean Vacuum Society
• /
• v.20 no.1
• /
• pp.42-49
• /
• 2011

We deposited $SiN_x$ thin films by using PECVD technique at $200^{\circ}C$ with various flow ratios of the $SiH_4/N_2$ gases. The photoluminescence measurements revealed that the maximum emission wavelength shifted to long wavelength as the ratio increased, however, positions of the several peak wavelengths, such as 1.9, 2.2, 2.4, and 3.1 eV, were independent on the ratio. Changes of the photoluminescence spectra were measured in the $N_{2}-$, $H_{2}-$, and $O_2$-annealed films. The luminescence intensities increased after the annealing process. In particular, the maximum emission wavelength shifted to short wavelength after $H_{2}-$ or $O_2$-annealing. But there were still several peaks on the spectra of all annealed films, several peak positions remained to be unchanged after the annealing. As for the light emission mechanism, we have considered the defect states of the Si- and N- dangling bonds in the $SiN_x$ energy gap, so that the energy transitions from/to the conduction/valence bands and the defect states in the gap were attributed to the light emission in the $SiN_x$ films. The experimental results point to the possibility of a Si-based light emission materials for flexible Si-based electro-optic devices.

• Proceedings of the KIEE Conference
• /
• 2001.11a
• /
• pp.112-114
• /
• 2001

In this letter, we report on the investigation of Si/Ti, Pt/Si/Ti, Co/Si/Ti Ohmic contacts to p-type 4H-SiC. The contacts were formed by a 2-step vacuum annealing at $550^{\circ}C$ for 5 min, $850^{\circ}C$ for 2 min respectively. The contact resistances were measured using the transmission line model method, which resulted in specific $10^{-4}{\Omega}cm^2$, and the physical properties of the contactcontact resistivities in the $9.2{\times}10^{-4}$, $7.1{\times}10^{-4}$ and $4.5{\times}s$ were examined using microscopy, AES(auger electron spectroscopy). AES analysis has shown that, at this anneal temperature, there was a intermixing of the Ti and Si, migration of into SiC. Overlayer of Pt, Co had the effect of decreasing the specific contact resistivity and improving the surface morphology of the annealed contact.

• Proceedings of the IEEK Conference
• /
• 2004.06b
• /
• pp.391-394
• /
• 2004

In this study, highly thermal stable Ni Germanosilicide has been utilized using NiPt alloy and novel NiPt/Co/TiN tri-layer. And, the Ni Germanosilicide Properties were characterized according to different Ge ratio (x) in $Si_{l-x}Ge_x$ for the next generation CMOS application. The sheet resistance of Ni Germanosilicide utilizing pure-Ni increased dramatically after the post-silicidation annealing at $600^{\circ}C$ for 30 min. Moreover, more degradation was found as the Ge fraction increases. However, using the proposed NiPt/Co/TiN tri-layer, low temperature silicidation and wide range of RTP process window were achieved as well as the improvement of the thermal stability according to different Ge fractions by the subsequent Co and TiN capping layer above NiPt on the $Si_{l-x}Ge_x$. Therefore, highly thermal immune Ni Germanosilicide up to $600^{\circ}C$ for 30 min is utilized using the NiPt/Co/TiN tri-layer promising for future SiGe based ULSI technology.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.109.2-109.2
• /
• 2015

Graphene, as a single layer of $sp^2$-bonded carbon atoms packed into a 2D honeycomb crystal lattice, has attracted much attention due to its outstanding properties such as high carrier mobility, chemical stability, and optical transparency. In order to synthesize high quality graphene, transition metals, such as nickel and copper, have been widely employed as catalysts, which need transfer to desired substrates for various applications. However, the transfer steps inevitably induce defects, impurities, wrinkles, and cracks of graphene. Here, we report a facile transfer-free graphene synthesis method through nickel and carbon co-deposited layer, which does not require separately deposited catalytic nickel and carbon source layers. The 100 nm NiC layer was deposited on the top of $SiO_2/Si$ substrates by nickel and carbon co-deposition. When the sample was annealed at $1000^{\circ}C$, the carbon atoms diffused through the NiC layer and deposited on both sides of the layer to form graphene upon cooling. The remained NiC layer was removed by using nickel etchant, and graphene was then directly obtained on $SiO_2/Si$ without any transfer process. Raman spectroscopy was carried out to confirm the quality of resulted graphene layer. Raman spectra revealed that the resulted graphene was at high quality with low degree of $sp^3$-type structural defects. Furthermore, the Raman analysis results also demonstrated that gas flow ratio (Ar : $CH_4$) during the NiC deposition and annealing temperature significantly influence not only the number of graphene layers but also structural defects. This facile non-transfer process would consequently facilitate the future graphene research and industrial applications.

• Applied Science and Convergence Technology
• /
• v.24 no.3
• /
• pp.72-76
• /
• 2015

Nickel oxide (NiO) thin films were grown on soda-lime glass substrates by RF magnetron sputtering method at room temperature (RT), and they were post-annealed at the temperatures of $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ and $400^{\circ}C$ for 30 minutes in vacuum. The electronic structure, optical and electrical properties of NiO thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy spectroscopy (REELS), UV-spectrometer and Hall Effect measurements, respectively. XPS results showed that the NiO thin films grown at RT and post annealed at temperatures below $300^{\circ}C$ had the NiO phase, but, at $400^{\circ}C$, the nickel metal phase became dominant. The band gaps of NiO thin films post annealed at temperatures below $300^{\circ}C$ were about 3.7 eV, but that at $400^{\circ}C$ should not be measured clearly because of the dominance of Ni metal phase. The NiO thin films post-annealed at temperatures below $300^{\circ}C$ showed p-type conductivity with low electrical resistivity and high optical transmittance of 80% in the visible light region, but that post-annealed at $400^{\circ}C$ showed n-type semiconductor properties, and the average transmittance in the visible light region was less than 42%. Our results demonstrate that the post-annealing plays a crucial role in enhancing the electrical and optical properties of NiO thin films.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2003.06a
• /
• pp.220-221
• /
• 2003

Equiatomic FePt and CoPt alloy thin films have received considerable attention as possible magnetic and magneto-optic recording because of their high magnetic anisotropy energy and high coercivity. The high coercivity in these thin films is due to the presence of finely dispersed ordered FePt phase mixed with disordered FePt phase. However, a high temperature treatment, either substrate heating during deposition or post annealing, is needed to obtain the ordered L1$\_$0/ phase with high value of magneto crystalline anisotropy. Recent microstructural studies on these films suggest that the average grain size ranges from 10-50 nm and the grains are magnetically coupled between each other. On the other hand, the ultrahigh-density magnetic recording media with low media noise imposes the need of a material, which consists of magnetically isolated grains with size below 10 nm. The magnetic grain isolation can be controlled by the amount of additional non-magnetic element in the system which determines the interparticle separation and therefore the interparticle interactions. Recently, much research work has been done on various non-magnetic matrices. Preliminary studies showed that the samples prepared in B$_2$O$_3$ and Carbon matrices have shown strong perpendicular anisotropy and fine grain size down to 4nm, which suggest these nanocomposite films are very promising and may lead to the realization of a magnetic medium capable of recording densities beyond 1 Tb/in$^2$. So, in this work, the effect of Carbon doping on the magnetic properties of FePt nanoparticles were investigated.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.182-182
• /
• 1999

The chemisorption effect of CO on the Ni/Cu(001) surface was investigated using LEED(Low Energy Electron Diffraction) and EELS(Electron Energy Loss Spectrscopy0 under the UHV conditions. after mounting the Cu(001) single crystal in the UHV chamber (base pressure 1$\times$10-10Torr), a clean surface was obtained after a few cycles of repeated Ar+ ion sputtering and annealing at about 40$0^{\circ}C$. The epitaxial thin Ni films were formed on the Cu(001) by evaporation from 99.999% Ni block. The pseudomorphic growth and the orderness of the thin Ni films were monitored by c(2$^{\circ}C$2) LEED pattern. CO adlayers on Ni epitaxial thin films were prepared by dosing pure CO has through a leak valve. After CO adsorpton at room temperature, two pairs of peaks were observed by EELS, whose relative intensities are changed as the film thickness is varied and time is elapsed. These two pair of peaks are likely related to different bonding sites (-top and bridge sites) of C-Ni as well as C-O vibration. Experimental results and qualitative interpretation of the spectra wille be discussed. The possibility of using EELS in combination with probe species (CO) to investigate the nature of thin film growth is mentioned. We will report the experimental result of O2 dosage on Ni film and interaction of CO and O2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.3
• /
• pp.245-249
• /
• 2007

The liquid crystal display (LCD) applications treated on the organic overcoat thin film surfaces by ion beam irradiation was successfully studied. The good LC aligning capabilities treated on the organic overcoat thin film surfaces with ion beam exposure of $60^{\circ}$ for 2 min above ion beam energy of 1200 eV can be achieved. But, the alignment of defect of NLC on the organic overcoat surface at low energy of 600 eV was measured. The pretilt angle of NLC on the organic overcoat thin film surface with ion beam exposure of $60^{\circ}$ for 2 min at energy of 1800 eV was measured about 1 degree. Finally, the good thermal stability of LC alignment on the organic overcoat thin film surface with ion beam exposure of $60^{\circ}$ for 2 min until annealing temperature of $200^{\circ}C$ can be measured.

• Korean Journal of Materials Research
• /
• v.20 no.5
• /
• pp.235-240
• /
• 2010

We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of $500^{\circ}C$. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at $250^{\circ}C$ and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.