• 한국진공학회지
• /
• 제7권4호
• /
• pp.300-305
• /
• 1998

rf magnetron sputtering 증착법으로 Al2O3(0001)기판위에 적층생장시킨 Pt박막의 결정성 및 이의 구조적 특성을 backscattering spectrometry(BS)/channeling, transmission electron microscopy(TEM)등을 이용해 분석하였다. $MeV^4$He ion channeling 결과, 증착시 기판의 온도가 $600^{\circ}C$, 증착된 Pt층의 두께가 3500$\AA$이었을 때 최소산란수율(channeling minimum yield)이 4%인 결정성이 우수한 Pt박막이 생장되었음을 확인하였으며, 동일한 증 착조건하에서 증착된 Pt층은 $Al_2O_3$(0001)기판위에 6중 대칭구조를 지닌(111)면방향으로 적층 생장되었으며, (111)면방향을 중심으로 대칭적인 원자배열 구조를 갖고 있는 쌍정구조를 형 성하고 있었다. 단면 TEM 분석결과에서도 격자부정합에 의한 strain을 감소시키기 위하여 형성된 쌍정을 관찰할 수 있었으며 strain이 집중되는 쌍정경계면에서 표면거칠기의 증가 또는 관찰되었다.

• Applied Science and Convergence Technology
• /
• 제24권6호
• /
• pp.228-231
• /
• 2015

We investigated the adsorption structures and the initial growth mode of ultra-thin Al films on a W(110) surface at a high temperature. When Al atoms were adsorbed on the W(110) at the substrate temperature of 1100 K and with coverage of 0.5ML, Al atoms formed a p($2{\times}1$) double-domain structure. When the coverage was 1.0 ML, the double domain of a hexagonal structure (fcc(111) face) rotated ${\pm}5^{\circ}$ from the [100] direction of the W(110) surface and another distorted hexagonal structure were found. Low-energy electron diffraction results along with ion scattering spectroscopy results showed that the Al atoms followed the Volmer-Weber growth mode at a high temperature.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
• /
• pp.156-156
• /
• 2000

Recently, the surface electronic states have attracted much attention since their standing wave patterns created around steps, defects, and adsorbates on noble metal surfaces such as Au(111), Ag(110), and Cu(111) were observed by scanning tunneling microscopy (STM). As a typical example, a striking circular pattern of "Quantum corral" observed by Crommie, Lutz, and Eigler, covers a number of text books of quantum mechanics, demonstrating a wavy nature of electrons. After the discoveries, similar standing waves patterns have been observed on other metal and demiconductor surfaces and even on a side polane of nano-tubes. With an expectation that the surface states could be utilized as one of ideal cases for studying two dimensionakl (sD) electronic system, various properties, such as mean free path / life time of the electronic states, have been characterized based on an analysis of standing wave patterns, . for the 2D electron system, electron density is one of the most importnat parameters which determines the properties on it. One advantage of conventional 2D electron system, such as the ones realized at AlGaAs/GaAs and SiO2/Si interfaces, is their controllability of the electrondensity. It can be changed and controlled by a factor of orders through an application of voltage on the gate electrode. On the other hand, changing the leectron density of the surface-state 2D electron system is not simple. On ewqy to change the electron density of the surface-state 2D electron system is not simple. One way to change the electron density is to deposit other elements on the system. it has been known that Pd(111) surface has unoccupied surface states whose energy level is just above Fermi level. Recently, we found that by depositing Pd on Cu(111) surface, occupied surface states of Cu(111) is lifted up, crossing at Fermi level around 2ML, and approaches to the intrinsic Pd surface states with a increase in thickness. Electron density occupied in the states is thus gradually reduced by Pd deposition. Park et al. also observed a change in Fermi wave number of the surface states of Cu(111) by deposition of Xe layer on it, which suggests another possible way of changing electron density. In this talk, after a brief review of recent progress in a study of standing weaves by STM, I will discuss about how the electron density can be changed and controlled and feasibility of using the surface states for a study of 2D electron system. One of the most important advantage of the surface-state 2D electron system is that one can directly and easily access to the system with a high spatial resolution by STM/AFM.y STM/AFM.

• Bulletin of the Korean Chemical Society
• /
• 제19권7호
• /
• pp.733-737
• /
• 1998

Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have compared adsorption properties of adsorbates on the Pt(Ill) surface with the Pt(lll)/γ-Al203 surface in the ethylene hydrogenation reaction. In two-layer thick model systems, the calculated activation energy of the hydrogenation by the surface platinum hydride is equal to the energy by the hydride over supported platinum/γ-alumina. The transition structure on platinum is very close to the structure on the supported platinum/γ-alumina surface. Hydrogenation by the surface hydride on platinum can take place easily because the activation energy is about 0.5 eV less than hydrogenation by ethylidene. On supported platinum/,y-alumina the activation energy of the hydride mechanism is about 0.61 eV less than that of ethylidene mechanism. In one-layer thick model systems, the activation energy of hydrogenation by ethylidene is about 0.13 eV less than the activation energy of hydride reaction. The calculated activation energy by the hydride over the supported platinum y-alumina is 0. 24 eV higher than the platinum surface. We have found from this result that the catalytic properties of one-layer thick model systems have been influenced by the support but the two-layer thick model systems have not been influenced by the support.

• 한국재료학회지
• /
• 제21권5호
• /
• pp.243-249
• /
• 2011

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to $89^{\circ}C$/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

• 한국기계가공학회지
• /
• 제15권2호
• /
• pp.111-117
• /
• 2016

The cutting performance of a developed small-angle spindle tool was investigated with Al6061 using a TiAlN coated high-speed steel end mill. Up-cut and down-cut processes in a milling machine were carried out at the range of 1000-4000 rpm for spindle speed and 50-300 mm/min for feed rate. As a result, the highest cutting force in the Fx direction was obtained from the up-cut process when the spindle speed was 1000 rpm and the feed rate was 100 mm/min. In the Fy direction, the highest cutting force appeared in the up-cut process at a feed rate of 250 mm/min at the same spindle speed. Conversely, the lowest cutting force came out in the up-cut process at a spindle speed of 4000 rpm and a feed rate of 50 mm/min. As for surface finish, the finest surface roughness was obtained as Ra 0.7642 um at a spindle speed of 4000 rpm and a feed rate of 50 mm/min. Consequently, given the cutting performance of the developed small-angle spindle tool, we conclude that its use in industrial practice is feasible.

• 한국표면공학회지
• /
• 제45권3호
• /
• pp.111-116
• /
• 2012

Oblique angle deposition (OAD) is a physical vapor deposition method which utilizes non-normal angles between the substrate and the vaporizing source. It has been known that tilting the substrate changes the properties of the film deposited on it, which was thought to be a result of morphological change of the film. In this study, OAD has been applied to prepare single and multilayer Al films by magnetron sputtering. The magnetron sputtering source of 4 inch diameter was used to deposit the films. Al films have been deposited on Si wafers and cold-rolled steel sheets. The multilayer films were prepared by changing the tilting angle upside down at each layer interval, which means that when the first layer was deposited at an angle of $+45^{\circ}$, the second layer was deposited at an angle of $-45^{\circ}$, and vice versa. The microstructure, surface roughness and reflectance of the films were investigated using a scanning electron microscope, a surface profiler and a spectrophotometer, respectively. The corrosion resistance was measured and compared using the salt spray test. The single layer film prepared at an oblique angle of $60^{\circ}$ prepared at other angles. However, for the multilayer films, the film prepared at an oblique angle of $45^{\circ}$ showed the most compact and featureless structure. The multilayer films were found to exhibit higher corrosion resistance than the single layer films.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.457-457
• /
• 2012

We presented plasma processing using a DC Arc Plasmatron for diamond deposition on Al2O3 ceramic substrates. Plasma surface treatments were conducted to improve deposition condition before processing for diamond deposition. The Al2O3 ceramic substrates deposited, $5{\times}15mm^2$, were investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). Properties of diamond (111), (220) and (311) peaks were shown in XRD. We identified nanocrystalline diamond films on substrates. The results showed that deposition rate was approximately $2.2{\mu}m/h$ after plasma surface treatments. Comparing the above result with a common processing, deposition rate was improved. Also, the surface condition was improved more than a common processing for diamond deposition on Al2O3 ceramic substrates.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
• /
• pp.137-137
• /
• 2000

The surface collective modes of thin K films deposited on Al(111) have been investigated using frequency dependent photoyield measurements and momentum resolved inelastic electron scattering. Jellium based theoretical calculations have predicted a richer set of features in the thin films than for the surface of a semi-infinite solid because there are th interference between two interfaces (substrate-film and film-vacuum) and heavy damping on the substrate. The use of an optical probe and electron scattering has allowed us to draw a more complete picture of the dynamic screening in thin films. The number, dispersion, damping and optical activity of the collective modes of the thin films have been measured as a function of K film thickness. New overlayer-induced excitations are observed : At qII=0, they correspond to the antisymmetric slab mode and the multipole surface plasmon. At finite qII=0, these modes undergo a transition towards the K multipole and monopole surface plasmons. With increasing coverage, the overlayer excitations turn into the collective modes of semi-infinite K. For a consistent interpretation of photoyield and electron energy loss spectra it is crucial to account for the non-analytic dispersion of the overlayer modes at small parallel wave vectors and for the finite angular resolution of the detector. The observed dispersions confirm predictions based on the time-dependent density functional approach.

• 한국전기전자재료학회논문지
• /
• 제14권12호
• /
• pp.972-978
• /
• 2001

Some effects of Al/N ratio on microstructure of AlN films grown on Si(111) substrates by PAMBE were investigated. Al/N ratio was controlled by rf power of N$_2$ plasma source system. Al excess or N excess conditions were obtained below or above 350 W rf power, respectively. Surface roughness and morphology of AlN film grown at Al/N=1.0 showed the best result. Under Al excess condition, it was suggested that excess Al atoms which did not contribute to the growth of AlN film prevent the normal crystal growth and make abnormal growth of some columns. However, under N excess condition, it was explained that some of the excess active N source turned into gas state and then desorbed out from substrate.