Design and Fabrication of a Vacuum Chamber for a Commercial Atomic Force Microscope

Park, Sang-Joon,Jeong, Yeon-Uk,Park, Soyeun,Lee, Yong Joong The Korean Vacuum Society 2014 Applied Science and Convergence Technology Vol.23 No.2

A vacuum chamber for a commercial atomic force microscope (AFM) is designed and fabricated. Only minimal modifications were made to an existing microscope in an effort to work in a vacuum environment, while most of the available AFM functionalities were kept intact. The optical alignment needed for proper AFM operations including a SLD (superluminescent diode) and a photodiode can be made externally without breaking the vacuum. A vacuum level of $5{\times}10^{-3}$ torr was achieved with a mechanical pump. An enhancement of the quality factor was observed along with a shift in the resonance frequency of a non-contact-mode cantilever in a vacuum. Topographical data of a calibration sample were also obtained in air and in a low vacuum using the non-contact mode and the results were compared.

Extending the Pressure Limit for Turbomolecular Pump up to 133 Pa by using Conductance-Reducer and Measuring the Pressure Differences in Vacuum Chamber

홍승수,와킬 칸,강상우,윤주영,신용현,Hong, S.S.,Khan, Wakil,Kang, S.W.,Yun, J.Y.,Shin, Y.H. The Korean Vacuum Society 2010 Applied Science and Convergence Technology Vol.19 No.1

진공게이지의 비교교정 방법으로 교정이 가능하고-비교교정은, 2차표준기라고 부르는 교정되어진 게이지와 교정할 다른 게이지의 지시값을 읽어 비교는 방법- 다른 진공관련 실험을 할 수 있는 기체 유량 시스템을 개발하였다. 교정시스템에의 진공용기는 터보분자펌프(TMP)에 의해서 배기하고, 후면에 스크롤펌프를 배치하여 배기시스템을 꾸몄다. 터보분자펌프의 최대허용가능 압력은 펌프의 주입구에서 0.1 Pa까지이며, 이보다 압력이 높아지면 배기속도가 감소하며 압력대 이하의 환경을 조절하기가 매우 어렵게 된다. 현재 133 Pa까지의 높은 압력을 발생시킬 수 있는 새롭게 개발된 기체유량조절시스템은 바이패스 라인에 맞도록 설계된 컨덕턴스-리듀서를 설치하여 터보분자펌프를 안전하게 운용할 수 있도록 하였다. 추가로 진공용기안에 전체압력 범위(0.1 Pa ~ 133 Pa)의 압력을 생성하며 기체 주입과 압력구배를 연구하였다. 압력의 최대 편차는 용기의 위쪽 방향에 위치한 가스 주입구에서 가까운 위치 C에서 1.6%로 나타났다. A dynamic flow system has been developed which can be used for vacuum gauge calibration by comparison method - a calibration method in which the reading of the gauge under calibration is compared to another calibrated vacuum gauge called the "secondary standard" - and other vacuum-related experiments. The chamber of the calibration system is pumped by a turbomolecular pump (TMP), backed by a scroll pump. As maximum acceptable pressure at the inlet of a TMP is 0.1 Pa, above which the TMP decelerates, the pumping speed decreases and it becomes more difficult to adjust pressure under such circumstances. In the present work, high pressures of up to 133 Pa have been generated in the chamber of the newly developed dynamic flow control system by installing a well-designed conductance-reducer in the by-pass line and, at the same time, operating the TMP in safe mode. In addition, the gas flow and pressure distribution within the chamber have been investigated for the entire pressure range (0.1 Pa ~ 133 Pa) while generating pressure dynamically. Maximum deviations in pressure (1.6 %) were observed at point C on the chamber, which is close to the gas inlet port on the top of the chamber.

Dependence of electron and photon emission during abrasion by surface condition of magnesium oxide crystal

Hwang, Do-Jin,Kim, Jong-Min,Park, Eun-Hee,Kim, Myoung-Won The Korean Vacuum Society 2001 Journal of Korean Vacuum Science & Technology Vol.5 No.1

We measured the simultaneous, time-resolved spectra of photon emission, electron emission, and frictional force during the abrasion single crystal MgO with a diamond stylus in vacuum. phE and EE signal can be detected with millisecond resolution during the wear of a single crystal MgO substrate with a diamond stylus. The emissions and wear behavior are strong function of surface condition, load and stylus velocity. Measurement on annealed vs as-received material show that the luminescence is primarily due to deformation, and the electron emission is primarily due to fracture. These emissions provide insight into the processes responsible for catastrophic failure of ceramics in wear applications.

Fabrication Process of Single CuO Nanowire Devices

Vu, Xuan Hien,Jo, Kwang-Min,Kim, Se-Yun,Lee, Joon-Hyung,Kim, Jeong-Joo,Heo, Young-Woo The Korean Vacuum Society 2014 Applied Science and Convergence Technology Vol.23 No.3

One-dimensional nanostructures such as nanowires have been extensively investigated as a promising type of material for applications of nanoscale technology. The fabrication of single-nanowire devices are consequently important and interesting. This study introduced a feasible method for growing CuO nanowires on Cu foils. The nanowires had diameters of 10~150 nm and lengths of more than $7{\mu}m$ and were grown by means of thermal oxidation in a vacuum. They were entirely and uniformly grown over the Cu foil surfaces and could be extracted and dispersed in an ethanol solution for further purposes. In addition, a simple fabrication method for realizing device functionality from a single CuO nanowire was reported. Fabricated devices were carefully checked by field-emission scanning electron microscopy (SEM). The probability of the realization of a single-CuO-nanowire device relative to that of all other types was estimated to be around 25%. Finally, the I-V characteristics of the devices were analyzed.

Electronic, Optical and Electrical Properties of Nickel Oxide Thin Films Grown by RF Magnetron Sputtering

Park, Chanae,Kim, Juhwan,Lee, Kangil,Oh, Suhk Kun,Kang, Hee Jae,Park, Nam Seok The Korean Vacuum Society 2015 Applied Science and Convergence Technology Vol.24 No.3

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.

High-Resolution X-Ray Photoelectron Spectroscopy Study of a Sb₂Te₃ Thin Film with the Polycrystalline Phase

이영미,김기홍,신현준,정민철,취야빙,Lee, Y.M.,Kim, K.,Shin, H.J.,Jung, M.C.,Qi, Y. The Korean Vacuum Society 2012 Applied Science and Convergence Technology Vol.21 No.6

스퍼터를 이용하여 실리콘 기판위에 제작된 안티몬-테레니움 다결정 박막을 방사광을 이용한 고해상도 엑스선 광전자 분광법 실험을 수행하여 화학적 상태를 분석하였다. 엑스선 회절 실험을 통해 제작된 안티몬-테레니움 박막은 롬보헤드럴 구조를 가지는 다결정임을 확인하였다. 엑스선 광전자분광법을 수행하기 위하여 표면의 산화막 제거를 위해 저에너지 네온 이온 스퍼터링을 빔에너지 1 kV로 1 시간동안 수행하였고, 이를 통해 표면 산화막이 완벽히 제거됨을 확인하였다. 또한, 스퍼처링에 의하여 표면 비정질화된 상태를 결정화 상태로 만들기 위해 상변화온도인 $100^{\circ}C$에서 5 분간 초고진공상태에서 열처리를 수행하였다. 이후 획득되어진 테레니움 4d와 안티몬 4d 속전자레벨 분석에서 각각의 묶음에너지가 40.4 그리고 33.0 전자볼트임을 확인할 수 있었으며, 각각은 단일한 화학적 상태를 나타내고 얻어진 피크의 밀도분석을 통해 화학적조성비가 2 : 3임을 확인하였다. We investigated chemical states of a $Sb_2Te_3$ thin film with the polycrystalline phase by using high-resolution x-ray photoelectron spectroscopy with synchrotron radiation. The $Sb_2Te_3$ thin film was formed by sputtering. The rhombohedral phase was confirmed by x-ray diffraction. To remove the surface oxide, we performed $Ne^+$ ion sputtering for 1 hour with the beam energy of 1 kV and post-annealing at $100^{\circ}C$ for 5 min in ultra-high vacuum. We obtained the Te and Sb 4d core-levels spectra with the peaks at the binding energies of 40.4 and 33.0 eV, respectively. The full-width of half maximum of both the Te and Sb $4d_{5/2}$ core-levels is 0.9 eV. The Te and Sb core-levels only show a single chemical state, and we also confirmed the stoichiometry of approximately 2 : 3.

Risk and Risk Perception of Nanotechnology

이상욱,Yi, Sang-Wook The Korean Vacuum Society 2010 Applied Science and Convergence Technology Vol.19 No.6

나노기술은 현재 대부분의 연구 및 산업 선진국에서 미래의 가장 영향력 있는 기술로 간주되고 있다. 이런 이유로 여러 나라의 정부는 미래의 기술경쟁에서 앞서 나가기 위해 나노기술 연구에 상당한 인적, 물적, 자원을 투여하고 있다. 그러므로 나노기술 연구는 다른 곳에 쓰일 수도 있었을 공적자원의 사용과 관련된 책무성을 요구받는 분야가 된다. 저자는 나노기술 연구의 책무성을 적절하게 지켜내기 위해서는 위험만이 아니라 시민의 위험인지도 반드시 고려해야 한다고 주장한다. 흔히 위험인지는 객관적 확률로 주어지는 위험에 비해 사람에 따라 달라지고, 시간에 따라 변화하고 극단적으로 양분되는 경향을 보인다는 근거에서 기술연구 정책에서 정당한 고려사항이 될 수 없다고 여겨진다. 하지만 저자는 위험인지가 대중이 특정 방향으로 행동하게 만들 수 있다는 의미에서 유효하고, 많은 사람이 공유한다는 의미에서 상호주관적이며, 민주주의 사회에서 필수적으로 반영되어야 한다는 점에서 고려대상으로서의 정당성을 획득한다고 주장한다. Nanotechnology is now widely believed to be one of the most influential techno-sciences of the future. Or at least it is believed that way in most of industrial countries including South Korea. Naturally, the governments of these industrial countries are currently investing a sizable portion of their human and material resources in order to go ahead in this prominent area of research. Consequently, nanotechnology in these countries has become one of the social sectors where reasonable accountability is normally called for. I claim that reasonable accountability of nanotechnology should take into account the risk-perception of citizens as regards nanotechnology as well as its risk itself. Risk-perception could be variable, changeable, and prone to be polarized; still we should pay more attention to public risk-perception because it is clearly effective in mobilizing public movements, objective in the intersubjective way, and legitimate in a democratic society.

Vacuum Characteristic of a Chamber Made of Mild Steel

Park, Chongdo,Ha, Taekyun,Cho, Boklae The Korean Vacuum Society 2015 Applied Science and Convergence Technology Vol.24 No.4

The base pressure and outgassing rate of a mild steel chamber were measured and compared to those of a stainless steel chamber. A combined sputter-ion and non-evaporable getter pump with a nominal pumping speed of 490 l/s generated the base pressure of $2.7{\times}10^{-11}$ mbar in the mild steel chamber and $1.2{\times}10^{-10}$ mbar in the stainless steel chamber. The rate-of-rise measurements show that the mild steel has an extremely low outgassing rate of $2.6{\times}10^{-13}$ mbar $ls^{-1}cm^{-2}$, which is about one-order of magnitude smaller than the outgassing rate of the stainless steels. Vacuum annealing of the mild steel at $850^{\circ}C$ reduced the outgassing rate further to $8.8{\times}10^{-14}$ mbar $ls^{-1}cm^{-2}$, which was comparable to the outgassing rate of a heat treated stainless steel for extreme-high vacuum use.

Vacuum Test of Cavity with Liquid Nitrogen

Choi, Suk,Park, Gunn-Tae,Kim, Heetae The Korean Vacuum Society 2015 Applied Science and Convergence Technology Vol.24 No.5

Schematic of RAON vacuum system is introduced. Vacuum test for superconducting cavity with liquid nitrogen is performed. Schematic plan for RAON vacuum system is introduced and vacuum control system for superconducting cavity test is constructed. Vacuum pressure of cavity is shown as a function of pumping time. The temperature of cavity is shown as a function of cooling time. Outgassing species from cavity is also detected. Detailed experimental procedure is presented to test the cavity vacuum with liquid nitrogen.

Calculation of Pressure Profiles in a Molecular Flow Regime using LTSpice IV

Choi, Won-Shik,Kang, Kun-Uk,Kim, Se-Hyun,Park, Chongdo The Korean Vacuum Society 2016 Applied Science and Convergence Technology Vol.25 No.4

This article describes an electrical network analysis (ENA) method to calculate the pressure distribution of a vacuum system in a molecular flow regime. The vacuum system was modeled using electrical components. For an accurate analysis, a complexly combined pipe model, excluding entrance conductance, was employed and the pressure distribution was simulated using ENA. A vacuum system comprising three vacuum pumps was used for simplicity. In addition, the ENA results were compared with results from finite element analysis (FEA) and experimental measurements. The pressure distribution profiles estimated from ENA, performed using the LTSpice IV software, were in agreement with FEA and experimental results.