• 한국재료학회지
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• 제4권5호
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• pp.516-523
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• 1994

이논문에서는 metal organic chemical vapor deposition(MOCVD)에 의해서 성장된 InGaAsP/InP이종접합구조의 격자부정합이 Photoluminescence(PL)효율에 미치는 영향을 연구하였다. 격자부정합은 (400)과 {511} x-ray reflection을 통해 측정하였고, 부정합 전위의 유무는 x-ray to-pography와 PL imaging을 통해 확인했다. PL강도 측정결과, 상대적으로 높은 PL강도는 탄성적으로 스트레인을 받은 시료에, 낮은 PL강도는 전위로 인해 비탄성적으로 변형된 시료에서 얻어졌다. 성장온도에서 격자정합된 시료의 PL효율이 실온에서 가장 높은 것을 알 수 있었다. PL강도와 X-ray반치폭과 관계에서, 시료의 광전자 특성이 구조적 특성과 밀접하게 연관됨을 알 수 있었다.

• 한국결정성장학회지
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• 제5권4호
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• pp.408-413
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• 1995

초크랄스키 실리콘 기판의 뒷면에 형성된 기계적 손상이 레이저 여기/극초단파 반사 광전도 감쇠법에 의한 소수반송자 재결합 수명 측정에 미치는 영향을 고찰하였다. 기계적손상의 정도는 X-선 이중결정 회절법과 X-선 단면 측정법 및 습식산화/선택적 식각 방법으로 평가하였다. 그 결과, 웨이퍼 뒷면에 가해지는 기계적 손상의 세기가 강할수록 소수반송자 재결합 수명은 짧아지고, 소수반송자 재결합 수명 측정에 영향을 미치는 반치전폭의 임계값은 약13초임을 알 수 있다.

• 한국세라믹학회지
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• 제33권1호
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• pp.56-64
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• 1996

A large amount of papers about the cubic-to-tetragonal phase transition the ferroelectric domain structures of the BaTiO3 were already reported but there exist still some needs to observe the domain behaviors directly. In this study the domain structures of the tinned plates prepared from ta single crystal grown by the TSSG technique were observed using a polarizing microscope TE and X-ray topography. The spatial relation be-tween the orientation states of domains was investigated and the effects of external stresses and electric fields on the behaviors of ferroelectric and ferroelastic domains were studied. All the 90$^{\circ}$walls cut off in the crystal are the wedge shaped lamellar domains and all the straight boundaries in the observed domain patte군 can be interpreted as the head-to-tail 90$^{\circ}$walls. The irregular overlapped boundaries commonly observed by using a polarizing microscope and X-ray topography are complex combinations of well-known 90$^{\circ}$walls and are domain walls were predominant and were stabilized after surface polishing. In the paraelectric phase region the domain walls vanished but the residual surface strain patterns could be seen at the same positions of the stabilized 90$^{\circ}$a-a walls in the tetragonal phase region, These stabilized walls resulted from the surface strain had a memory effect in domain formation during the repeated phase transitions and could notr be affected by an external electtric field.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.3-3
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• 2002

Many studies on crystal growth mechanisms of the hen egg-white lysozyme protein crystals have mainly performed by optical microscopy and atomic force microscopy (AFM). As results, two types of growth mechanisms, which are a two-dimensional nucleation mechanism and a spiral growth mechanism, were identified. However, there was no direct evidence of grown-in screw dislocations at the spiral sites. We first observed the screw dislocations in tetragonal lysozyme crystals using synchrotron X-ray topography. In addition, to confirm the characteristics of dislocations, we have observed some elastic constants in lysozyme crystals in terms of the sound velocity measurement by pulse echo methods. Tetragonal hen egg-white lysozyme crystals were grown by the concentration gradient method. The crystals were grown in test tubes, with an inner diameter of 8 ㎜ and 80 ㎜ in length, held vertically. The test tubes were kept at 23C for 2 weeks. The maximum size of crystals were 3×3×4 ㎟. The high quality crystals were examined by Laue topography with a water filter using synchrotron radiation. Figure is a X-ray topograph. Several straight screw dislocations were observed. We also determined Burgers vector to be a [110] direction. The measurement of sound velocity was performed by the digital signal processing method. the crystals were placed in stainless steel vessel, which was filled with lysozyme solution used for crystal growth. We observed the longitudinal sound velocity along the [110] direction in the tetragonal is obtained to be 1817 ㎧. Therefore, Young modulus and shear modulus were evaluated to be 2.70 Gpa and 1.02 Gpa, respectively, if we assumed Poisson ratio is 0.33. These results will be discussed at the meeting.

• The Journal of Advanced Prosthodontics
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• 제13권4호
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• pp.258-267
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• 2021

PURPOSE. The purpose of this study was to compare the surface roughness, phase transformation, and surface topography of dental zirconia with three different yttrium oxide compositions under same grinding and polishing conditions. MATERIALS AND METHODS. Three zirconia disks (IPS e.max ZirCAD LT, MT, MT multi, Ivoclar Vivadent AG, Schaan, Liechtenstein) were selected for experimental materials. Sixty-nine bar-shaped specimens were fabricated as 12.0 × 6.0 × 4.0 mm using a milling machine and glazing was conducted on 12.0 × 6.0 mm surface by same operator. With a custom polishing device, 12.0 × 6.0 mm surfaces were polished under same condition. Surface roughness (Ra[㎛]) was measured before grinding (C), after grinding (G), and at every 3 steps of polishing (P1, P2, P3). X-ray diffraction and FE-SEM observation was conducted before grinding, after grinding, and after fine polishing (P3). Statistical analysis of surface roughness was performed using Kruskal-Wallis test and Mann-Whitney-U test was used as a post hoc test (α = .05). RESULTS. There were no significant differences of surface roughness between LT, MT, and MM groups. In LT, MT, and MM groups, P3 groups showed significantly lower surface roughness than C groups. X-ray diffraction showed grinding and polishing didn't lead to phase transformation on zirconia surface. In FE-SEM images, growths in grain size of zirconia were observed as yttrium oxide composition increases. CONCLUSION. Polished zirconia surface showed clinically acceptable surface roughness, but difference in yttrium oxide composition had no significant influence on the surface roughness. Therefore, in clinical situation, zirconia polishing burs could be used regardless of yttrium oxide composition.

• 한국표면공학회지
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• 제39권5호
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• pp.229-234
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• 2006

Diamonds have been widely employed as polishing media for precise machining and noble substrates for microelectronics. The recent development of the split sphere press has led to the enhancement of low quality natural diamonds. Synthesized and treated diamonds are sometimes traded deceptively as high quality natural diamonds because it is hard to distinguish among these diamonds with conventional gemological characterization method. Therefore, we need to develop a new identification method that is non-destructive, fast, and inexpensive. We proposed using new methods of UV fluorescence and X-ray Lang topography for checking the local HPHT stress field to distinguish these diamonds from natural ones. We observe unique differences in the local stress field images in treated diamonds using UV fluorescence and Lang topography characterization. Our result implies that our proposed methods may be appropriate for identification of the treated diamonds.

• 대한추나의학회지
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• 제3권1호
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• pp.153-166
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• 2002

후방 종인대 골화중의 치료에 수술적 처치 이전 단계의 환자에 대한 보존적 치료는 대증적 치료가 주가 되어 왔다. 본 증례에서는 추나요법을 주로 시행한 후방 종인대 골화증 환자(32세, 여자)에서 시각적 상사 척도의 각 치료기간별 감소 및 ROM의 증가와 더불어 X-ray상의 변화까지도 감소되는 현저한 치료효과를 나타내게 되었다. 향후 본 질환에 대한 보다 심도 있는 연구가 진행된다면 후방 종인대 골화증의 보존적 치료에 추나요법이 뚜렷한 역할을 공헌하리라 기대되며 이에 대한 관심과 연구가 진행되어야 한다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.19.2-19.2
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• 2011

The $(Sr_{0.75},\;La_{0.25})TiO_3$ (SLTO) ultra-thin films with various thicknesses have been grown on Ti-O terminated $SrTiO_3$(100) substrate using Laser-Molecular Beam Epitaxy (Laser MBE). By monitoring the in-situ specular spot intensity oscillation of reflection high energy electron diffraction (RHEED), we controlled the layer-by-layer film growth. The film structure and topography were verified by atomic force microscopy (AFM) and high resolution thin film x-ray diffraction by the synchrotron x-ray radiation. We have also investigated the electronic band structure using x-ray absorption spectroscopy (XAS). The ultra thin SLTO film exhibits thickness driven metal-insulator transition around 8 unit cell thickness when the film thickness progressively reduced to 2 unit cell. The SLTO thin films with an insulating character showed band splitting in Ti $L_3-L_2$ edge XAS spectrum which is attributed to Ti 3d band splitting. This narrow d band splitting could drive the metal-insulator transition along with Anderson Localization. In optical conductivity, we have found the spectral weight transfer from coherent part to incoherent part when the film thickness was reduced. This result indicates the possibility of enhanced electron correlation in ultra thin films.

• 한국광물학회:학술대회논문집
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• 한국광물학회.한국암석학회 2005년도 공동학술발표회 논문집
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• pp.50-57
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• 2005

Although the bulk composition of materials is one of the major considerations in extractive metallurgy and environmental science, surface composition and topography (edges and dislocations are preferred sites for physicochemical reactions) control surface reactivity, and consequently play a major role in determining metallurgical phenomena and pollution by heavy metals and organics. An understanding of interaction mechanisms of different chemical species with the mineral surface in an aqueous media is very important in natural environment and metallurgical processing. X-ray photoelectron spectroscopy (XPS) has been used as an ex-situ analytical technique, but the material to be analyzed can be any size from $100{\mu}m$ up to about 1 cm. It can also measure mixed solids powders, but it is impossible to ascertain the original source of resulting x-ray signals where they were emitted from, since it radiates and scans the macro sample surface area.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.155-159
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• 1997

We investigated the effect of mechanical backside damage in Czochralski silicon wafer. The intensity of mechanical damage were evaluated by minority carrier recombination lifetime by a laser excitation/microwave reflection photoconductance decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photoacoustic displacement values are also increased proportionally.