Sn, In/Si(Ⅲ)표면에서의 구조변화 및 이탈에너지에 대한 연구

곽호원(Ho-Weon Kwak),곽지훈(Ji-Hoon Kwak) 한국산업융합학회 2002 한국산업융합학회 논문집 Vol.5 No.3

The change of surface structures for the deposition of Sn, In on clean Si(111) surface is investigated as a function of surface coverage by RHEED system. For tin submonolayer films 7×7, √3×√3 structures are observed depending on the coverage and substrate temperature. For indium submonolayer films 7×7, √3×√3, √31×√31, 1×1 structures are observed. We find that at substrate temperature of 500℃, √3×√3 structure is formed at tin coverages of 0.2~0.4 ML and at indium coverages of 0.1~0.3 ML, respectively. From the desorption process, the desorption energies of Sn, In in √3×√3 structure is observed to he 3.25 eV, 2.66eV, respectively.<br/> <br/>

RHEED회절점의 강도변화에 따른 In / Si(111)에 대한 연구

곽호원(Ho-Weon Kwak),이의완(Eui-wan Lee),박동수(Tong-Soo Park),이운환(Woon-Hwan Lee) 한국진공학회(ASCT) 1997 Applied Science and Convergence Technology Vol.6 No.2

Si(111) 7×7표면에 In을 증착시킬 때 기판용도와 증착량에 따른 표면구조의 변화를 RHEED(Reflection High Energy Electron Diffraction) 상 (pattern)과 RHEED상의 회절반점(spot)강도 변화를 관찰하여 조사하였다. Si(111) 기판온도를 400℃로 유지하면서 In을 증착시킬 때 증착량이 약 0.1, 0.3, 0.5 ML에서 각각 √3×√3, √31×√31, 4×1구조가 관찰되기 시작하였다. 기판온도 300°에서는 증착량이 약 0.2ML에서부터 4×1구조가 나타나고 0.8ML이상에서부터는 4×1+√3×√3 혼합구조가 관찰되기 시작하였다. Si(111)-√3×√3구조의 기판온도를 실온으로 유지하면서 In를 증착시킬 때 증착량이 0.25, 0.7ML에서 각각 2×2, √7×√3구조가 나타나기 시작하였다. RHEED 반점의 강도변화를 이용하여 Si(111)-√7×√3구조에서의 In원자의 이탈 과정을 조사한 결과 이탈 에너지는 2.84 eV로 조사되었다. The change of surface structures for the deposition of indium on clean Si(111) surface is investigated as a function of substrate temperature and surface coverage by RHEED. We find that at substrate temperature of 400℃, √3×√3, √31×√31 and 4×1 structures are formed at indium coverages of 0.2, 0.3 and 0.5 ML, respectively. We also find that for the substrate temperature of 300℃, 4×1 structure starts to be formed by 0.2 ML of indium, and the mixed structure of 4×1 and √3×√3is observed for more than 1.0ML. On the other hand, if the indium is deposited on the Si(111)-√3×√3 structure at room temperature, 2×2 and √7×√3 structures are found to form at 0.2 and 0.4 ML, respectively. From the desorption process, the desorption energy of indium in Si √7×√3 structure is observed to be 2.84 eV.

Si(111)표면 위에서 Si의 동종층상성장에 관한 연구

곽호원(Ho-Weon Kwak),문병연(Byung-yeon moon) 한국산업융합학회 2004 한국산업융합학회 논문집 Vol.7 No.4

The growth mode of the Si layers which were grown on Si(111) by using Ag as surfactant were investigated by intensity oscillations of the RHEED specular spot at the different temperatures. we found that the introduction of Ag as the surfactant alters the growth mode from a three-dimensional clustering mechanism to a two-dimensional layer-by-layer growth. In the growth of Si layers on Si(111) with a surfactant Ag, At 450℃, RHEED intensity oscillation was very stable and periodic from early stage of deposition to 32 ML. RHEED patterns during homoepitaxial growth at 450℃ was changed from 7×7 structure into √3×√3 structures. Since the √3×√3 structure include no stacking fault, the stacking fault layer seems to be reconstructed into normal stacking one at transition from the 7×7 structure to a √3×√3 one. We also found that the number of the intensity oscillation of the specular spot for Si growth with a surfactant Ag was more than for Si growth without a surfactant. This result may be explained that the activation energy decrease for the surface diffusion of Si atoms due to segregation of the surfactant toward the growing surface.<br/>

RHEED 반점의 강도변화를 이용한 Si(111) - Sn 표면조사

곽호원(Ho Weon Kwak),이의완(Eui-Wan Lee) 한국진공학회(ASCT) 1994 Applied Science and Convergence Technology Vol.3 No.2

Si(111)-7×7 표면에 Sn을 증착시킬 때 기판온도와 증착량에 따른 표면구조의 변화를 RHEED(Reflection High Energy Electron Diffraction)상(pattern)과 RHEED상의 회절반점(spot) 강도변화를 관찰하여 조사하였다. Si(111) 기판온도를 400℃로 유지하면서 Sn을 증착시킬 때 √3×√3 구조가 관찰되었으며 기판온도 200℃ 이하에서는 증착량에 따라 √3×√3×, 2√3×2√3 구조들이 관찰되었다. RHEED 반점의 강도변화를 이용하여 Si(111)-Sn √3×√3 구조에서의 Sn원자의 이탈 과정을 조사한 결과 이탈에너지는 3.3±0.1 eV로 조사되었다. On the Si(111)-7×7 surface, we investigated the surface structures according to the temperatures of the substrate and the thickness of Sn which is deposited on the Si(111) surface by using RHEED. When Sn was deposited on the Si(111)-7×7 surface at 400℃, √3×√3 structure was formed. On the Si(111)-7×7 surface at 200℃, according to the thickness of Sn which is deposited, √3×√3, 2√3×2√3 structures were formed respectively. By using the RHEED intensity oscillation of Si(111)-Sn √3×√3 spots, we investigated the desorption process of Sn on the √3×√3 structure and obtained the desorption energy. The desorption energy is 3.3±0.1 eV.

계면금속(Sn)이 흡착된 Ge(111)표면에서의 Ge의 층상성장에 대한 연구

곽호원(Ho-Weon Kwak) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.2

RHEED(Reflection High Energy Electron Diffraction)상(pattern)의 거울반사점(specular spot) 강도의 주기적인 진동을 이용하여, 계면금속(surfactant)Sn을 흡착하지 않은 경우와 흡착한 경우 Ge(111) 표면 위에서 Ge의 층상성장을 조사하였다. 계면금속을 흡착하지 않았을 경우, 기판온도 200℃에서 반점의 강도가 24ML 정도 안정되게 진동하는 것으로 보아, Ge 층상성장의 최적온도로 생각되었다. 계면금속(Sn) 0.5 ML를 Ge(11l) 표면위에 흡착시킨 후, Ge 성장에서는 기판온도 200℃에서 성장초기에 불규칙한 진동이 나타났으며, 반점강도의 주기적인 운동이 흡착하지 않은 경우 보다 더 큰 진폭으로 38ML 이상까지 관찰되었으며 Ge이 성장하는 동안 d2×2 구조의 변화가 없었다. 이는 계면금속이 교환작용으로 성장표면 쪽으로 편석(segregation)하면서 흡착원자의 표변확산 거리를 저해시켜 3차원적 핵성장에 의한 층상성장을 저해하고 대신 2차원적 성장을 도우는 것으로 생각된다. The epitaxial growth of Ge on the clean and surfactant (Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24 ML at the substrate temperature of 200℃. Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge (111) seems to be 200℃. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations are observed in the early stage of the growth. The RHEED intensity oscillation was very stable and periodic up to 38 ML, and the d2×2 structure was not charged with continued adsorption of Ge at the substrate temperature of 200℃. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface.

알칼리금속/Si(111)표면에서의 구조변화 및 탈착에너지 조사

곽호원(Ho-Weon Kwak),정승민(Sung-Min Jung) 한국산업융합학회 2003 한국산업융합학회 논문집 Vol.6 No.3

The effects of adsorption and desorption of alkali-metals on Si(111) surface were investigated by using AES and RHEED-system. The adsorption system is a fundamental interest because of its unique electronic properties such as measurement of work function change, adatom-core level shift. It was found that the growth node of K on Si(111) surface was layer by layer growth and the saturation coverage was 2.0ML at room temperature. Superstructure changes on Si(111) surface according to the alkali-metal thickness and substrate temperatures were accurately defined. By applying the isothermal desorption method, the desorption energies of Li/Si(111) and K/Si(111) surfaces was measured. On Li/Si(111) and K/Si(111) surfaces, the desorption energies were 3.07 eV, 2.19 eV respectively.

정상군과 폭주부족군에서 조절반응 변화량의 비교

곽호원(Ho Weon Kwak),이세희(Se Hee Lee),곽형빈(Hyung Bin Kwak) 한국안광학회 2014 한국안광학회지 Vol.19 No.1

Purpose:This study investigated accommodative changes by measuring accommodative response, appearing on the normal and convergence insufficiency Group, by using both eyes open-view auto-refractometer (Nvision- K5001, shin-nippon, Japan). Methods: It carried out objective and subjective refractions, targeting 74 college students (54 males and 20 females) aged between 19 and 29 (21.59±2.53), spherical equivalent OD -2.28±2.03 D, OS -2.18±2.01 D, by measuring accommodative responses at full correction and under correction with plus lens +0.25, +0.50, +0.75 arbitrarily added. Results: In the group of normal and convergence insufficiency, the shorter fixation distances were, the greater accommodative lags showed. The group of convergence insufficiency showed the lesser changes of accommodative response than those of normal. But we found that the convergence insufficiency group had a little larger accommodative amplitude in the total fixation distances. The full correction of convergence insufficiency group and the under correction (+0.50 D) of normal were alike in the accommodative responses. We have also investigated that the correlation between accommodative responses and fixation distances was decreased steeply at the excessive low vision correction. Conclusions: Under correction (+0.50 D) in a near distance is expected to avoid unnecessary accommodative responses, make eyes relaxed and comfortable.

RHEED를 이용한 Ge(111)표면의 층상성장에서 Sn의 영향

곽호원(Ho-Weon Kwak) 한국산업융합학회 2001 한국산업융합학회 논문집 Vol.4 No.4

The epitaxial growth of Ge on the clean and surfactant(Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24ML at the substrate temperature of 200℃ Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge(111) seems to be 200℃. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations arc observed in the early stage of the growth. The RHEED intensity oscillation was very stable and periodic up to 38ML, and the d2x2 structure was not charged with continued adsorption of Ge at the substrate temperature of 200℃. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface. From the desorption process, the desorption energy of Sn in Ge √5x√5 structure is observed to be 3.28eV.<br/>

Rheed 반점강도의 변화를 이용한 Si(111)-Ad 표면조사

곽호원,이의완,이상윤,Kwak, Ho-Weon,Lee, Eui-Wan,Lee, Sang-Yun 한국재료학회 1994 한국재료학회지 Vol.4 No.6

Si(111)표면위에 Au의 증착량과 기판온도에 따른 표면구조의 변화를 RHEED(Reflection High Energy Electron Diffraction)상(pattern)과 RHEED상의 회절반점(spot)강도변화를 이용하여 조사하였다. Si(111) $7\times7$구조를 Au 를 0.1ML-0.4ML증착후에 기판을 $350^{\circ}C$-$750^{\circ}C$로 수초간 가열하면 $7\times7$구조에서 $7\times7$ + $5\times2$의 혼합 구조로 변화하였으며 증착량 0.4ML-1.0ML에서는 RHEED상이 기판온도와 증착량에 따라 $5\times2,\alpha- \sqrt{3} \times \sqrt{3},\beta- \sqrt{3} \times \sqrt{3}$의 구조들이 관찰되었다. $6\times6$구조는 기판온도 $270^{\circ}C$-$370^{\circ}C$에서 증착량 0.8ML에서부터 형성되기 시작하여 1ML에서 완성되었다. AES(Auger Electron Spectroscopy)를 이용한 $\alpha- \sqrt{3} \times \sqrt{3},5 \times 2$구조에서의 Au원자의 이탈과정 조사에서 이탈 에너지는 각각 79kcal/mol, 82kcal/mol로 조사되었다. The Si(ll1) surface structures induced by deposition of Au atoms were investigated by RHEED system. When Au atoms were deposited on the Si(ll1) $7\times7$ surfade, the dependence of structures and phases on the substrate temperatures and coverages was drastic. For O.1ML to 0.4ML of coverage the $7\times7$ structure changes to $7\times7$ + $5\times2$ structure as temperature increases to $350^{\circ}C$-$750^{\circ}C$. Between 0.4M1 to 1.OML the phase changed to $5 \times 2,\alpha- \sqrt{3} \times \sqrt{3},\beta- \sqrt{3} \times \sqrt{3}$ structure according to the substrate temperature and coverages. When the coverages exceeds O.SML, the 6 x 6 structure appears at the substrate temperature range between $270^{\circ}C$-$370^{\circ}C$ and compeletely transforms to 6 x6 at 1,OML. The isothermal desorption of Au on Si(ll1) surface investigated by using AES in the $\alpha- \sqrt{3} \times \sqrt{3},5 \times 2$ structures shows that the desorption energys of $\alpha- \sqrt{3} \times \sqrt{3}$ and 5 x 2 were 79Kcal/mol and 82 Kcal/mol respectively.

Si(3)7×7 표면구조에서의 Ge성장에 관한 연구

리의완 ( Eui Wan Lee ),곽호원 ( Ho Weon Kwak ) 경북대학교 과학교육연구소 1993 科學敎育硏究誌 Vol.17 No.-

We have investigated the superlattice structures, the growth modes and the variations of inpiane lattice constants for Germanium on Si( 111) 7×7 surface using RHEED and AES. The changes of superlattice sturctures at the substrate temperature of room temperature, 350`C and 500`C etc. are observed. Firstly, of room temperature case, we observed that the structures are changed from 7×7 to the diffuse 1×1 at 0.7 ML and ne×t to the nonstructure above 2IML. Secondly, for the substrate temperature of 350”C, we observed that the structures are changed from 7×7 to the diffuse 1×1 at 0.7ML and to the formation of island above 4ML. ``Thirdly, for the substrate temperature of 500``C, we observed that the structures are changed from 7×7 to 7×7+5×5 at OJML, and ne×t to 5×5 at 2ML, and ne×t to 5×5+7×7 at 1OML, and ne×t to 7×7 at 45 ML, and finally to bulk Ge structure at the hundreds of monolayer. Also, from the measurement of intensity distribution of the reciprocal lattice rod(0, 0), inplane lattice constant for the 7×7 structure at 45ML is observed to be 3% large than that of Si(111) 7×7 structure. We also measure the variations of inplane lattice constants for the sample of 45 ML Ge on the surface of Si(111) 7×7 as a function of temperatures. From these measurements, we find that from 600`C the lattice constant decreases slowly and the intensity of Si(LVV)-92eV increases. Therefore, from these results, we conclude that alloy of Si and Ge is formed above this tempera-ture of 6000.