• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.170-170
• /
• 2003

We have implanted on sapphire substrate with various ions and investigated the properties of GaN epilayers grown on implanted sapphire substrate by metal organic chemical vapor deposition (MOCVD). Sapphire is typical substrate for GaN epilayers. However, there are many problems such as lattice mismatch and thermal coefficient difference between sapphire substrate and GaN. The ion implanted substrate's surface had decreased internal tree energies during the growth of the GaN epilayer, md the misfit strain was relieved through the formation of an AlN phase on the ions implanted sapphire(0001) substrates. [1] The crystal and optical properties of GaN epilayer grown in ions implanted sapphire(0001) substrate were improved.

• Applied Science and Convergence Technology
• /
• v.24 no.6
• /
• pp.242-244
• /
• 2015

ZnO:Ga thin films were deposited by RF magnetron sputtering technique from ZnO (3 wt.% $Ga_2O_3$) target onto glass substrates under various RF power. The influence of RF power on the structural, electrical, and optical properties of ZnO:Ga thin films was investigated by X-ray diffraction, atomic force microscopy, Hall method and optical transmission spectroscopy. As the RF power increases from 50 to 110W, the crystallinity is deteriorated, the root main square surface roughness is decreased and the sheet resistance is increased. The increase of sheet resistance is caused by decreasing carrier concentration due to interstitial Ga ion. All films are transparent up to 80% in the visible wavelength range and the adsorption edge is a red-shift with increasing RF power.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.23 no.6
• /
• pp.789-794
• /
• 1986

The current-voltage characteristics of ion-implanted GaAs MESFET's have been simulated by using the velocity saturation model. Using this model, a MESFET with threshold voltage of -0.5V and transconductance of 460 mS/mm is designed. To implement high transconductance MESFET's, low energy ion-implantation (20 keV) and RTP(Rapid Thermal Process) activation ($575^{\circ}C$, 5sec) processes are required.

• Korean Journal of Materials Research
• /
• v.13 no.9
• /
• pp.598-605
• /
• 2003

The optimized conditions for the cross-sectional TEM sample preparation using tripod polisher and ion-beam miller was confirmed by AFM and TEM. For the TEM observation of interfaces including InGaN layers like InGaN/GaN MQW structures, the sample preparation by the only tripod polishing was useful due to the reduction of artifacts. On the other hand, in case of the thick nitride films like ELO, PE, and superlattice, both tripod polishing and controlled ion-beam milling were required to improve the reproducibility. As a result, the ion-beam milling with the $60^{\circ}$modulation showed the minimum height difference between film and sapphire interface and the ion-beam milling of the $80^{\circ}$modulation showed the broad observable width.

• Applied Microscopy
• /
• v.36 no.spc1
• /
• pp.25-33
• /
• 2006

Nanofabrication with finely focused ion and electron beams is reviewed, and position and size controlled fabrication of nano-metals and -semiconductors is demonstrated. A focused ion beam (FIB) interface attached to a column of 200keV transmission electron microscope (TEM) was developed. Parallel lines and dots arrays were patterned on GaAs, Si and $SiO_2$ substrates with a 25keV $Ga^+-FIB$ of 200nm beam diameter at room temperature. FIB nanofabrication to semiconductor specimens caused amorphization and Ga injection. For the electron beam induced chemical vapor deposition (EBI-CVD), we have discovered that nano-metal dots are formed depending upon the beam diameter and the exposure time when decomposable gases such as $W(CO)_6$ were introduced at the beam irradiated areas. The diameter of the dots was reduced to less than 2.0nm with the UHV-FE-TEM, while those were limited to about 15nm in diameter with the FE-SEM. Self-standing 3D nanostructures were also successfully fabricated.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.05a
• /
• pp.159-160
• /
• 2010

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1262-1264
• /
• 1993

An amorphous $Se_{75}Ge_{25}$ thin film as inorganic resist for the focused ion beam lithography(FIBL) is investigated. This film offers an attractive potential alternative to polymer resists because of a number of advantages, such as the possibility of preparing physically uniform films of thickness as small as 200A and obtaining both positive and negative resist action in the same material, compatibility with dry processing, the sensitivity on optical, e-beam and ion beam exposure, the high-temperature stability, etc. In previous paper, the defocused ion beam-induced characteristics in a-$Se_{75}Ge_{25}$ film has been propose. Practically it is neccesary to know the relation with resist and source ions. For the purpose, the ion stopping power, the ion projected range and ion transmission coefficiency are studied. In this paper, the theoretically calculated values of parameters are presented and compared with theory.

• Journal of the Mineralogical Society of Korea
• /
• v.28 no.4
• /
• pp.293-297
• /
• 2015

Focused ion beam (FIB) technique is widely used in the precise preparation of thin slices for the transmission electron microscopic (TEM) observation of target area of the minerals and geological materials. However, structural damages and artifacts by the Ga ion beam as well as electron beam damage are major difficulties in the TEM analyses. TEM analyses of the mineral samples showed the amorphization of quartz and feldspar, curtain effect, and Ga contamination, particularly near the grain edges and relatively thin regions. Although the ion beam damage could be much reduced by the improved procedures including the adjustment of the acceleration voltage and current, the ion beam damage and contamination are likely inevitable, thus requiring careful interpretation of the micro-structural and micro-chemical features observed by TEM analyses.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.815-819
• /
• 2013

Micropatterns of streptavidin and human epidermal carcinoma A431 cells were successfully imaged, as received and without any labeling, using cluster $Au_3{^+}$ ion beam-based time-of-flight secondary ion mass spectrometry (TOF-SIMS) together with a principal component analysis (PCA). Three different analysis ion beams ($Ga^+$, $Au^+$ and $Au_3{^+}$) were compared to obtain label-free TOF-SIMS chemical images of micropatterns of streptavidin, which were subsequently used for generating cell patterns. The image of the total positive ions obtained by the $Au_3{^+}$ primary ion beam corresponded to the actual image of micropatterns of streptavidin, whereas the total positive-ion images by $Ga^+$ or $Au^+$ primary ion beams did not. A PCA of the TOF-SIMS spectra was initially performed to identify characteristic secondary ions of streptavidin. Chemical images of each characteristic ion were reconstructed from the raw data and used in the second PCA run, which resulted in a contrasted - and corrected - image of the micropatterns of streptavidin by the $Ga^+$ and $Au^+$ ion beams. The findings herein suggest that using cluster-ion analysis beams and multivariate data analysis for TOF-SIMS chemical imaging would be an effectual method for producing label-free chemical images of micropatterns of biomolecules, including proteins and cells.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.169.2-169.2
• /
• 2013

본 연구에서는 gas를 이용한 PECVD 공법중 이온화 에너지가 높고 대면적 코팅이 용이한 Hybrid 코팅 장비에서 Linear Ion-Gun 이용하여 탄화수소 계열의 gas인 $C_2H_2$ 와 Si을 함유한 TMS (tetramethylsilane, $Si(CH_3)_4)$ gas를 이용하여 저마찰, 고경도 특성을 갖는 Si-DLC 코팅에 대한 연구를 수행하였다. Si-DLC 코팅에 앞서 전처리 공정으로 Linear Ion-Gun에 Ar gas를 주입하고 고전압의 DC 전원을 인가하여 제품 표면의 건식세정 및 표면 활성화를 진행 후, $C_2H_2$ 와 TMS gas를 Linear Ion-Gun에 주입하여 Si-DLC 코팅 공정을 진행하였다. Si-DLC 코팅시 $C_2H_2$ gas 주입량을 고정하고 TMS 가스 유량을 5~20sccm으로 조절하여 Si 함유량에 따른 Si-DLC 코팅막의 특성을 분석하였다. 이렇게 코팅된 Si-DLC의 박막 특성 분석으로 마찰계수 측정을 위해 ball-on-disk 타입의 tribometer를 사용하였으며, 박막 경도 측정은 Nano-indenter를 이용하여 분석을 진행하였다. 그 결과 Si을 포함하지 않는 DLC의 경우 마찰계수가 ~0.2를 가지는 반면, Si-DLC의 경우 Si 함유량이 약 1.5at%일 때, 마찰계수 ~0.04 저마찰의 우수한 특성을 지니며, 박막의 경도는 22[Gpa]로 고경도의 Si-DLC 코팅을 확인할 수 있었다.