Lateral force microscopy in low normal force limit

Lee, H.,Lee, N.,Seo, Y. Elsevier 2010 Current Applied Physics Vol.10 No.1

We have studied frictional force between SiN tip and Si surface by using lateral force microscopy. The cantilever we have used has very low stiffness of 0.006N/m, and the normal force acting on the surface was much lower than the attractive force such as van der Waals force. In this low normal force limit, it was found that the frictional force did not depend on the normal force. We suggest a calibration method to estimate the attractive force from the lateral force data in this limit. The estimated attractive force between Si sample and SiN tip with radius of 10nm was 0.4nN in flat region and 0.65nN at the corner of a rectangular hole.

Lateral force microscopy in low normal force limit

이현수,이내성,서용호 한국물리학회 2010 Current Applied Physics Vol.10 No.1

We have studied frictional force between SiN tip and Si surface by using lateral force microscopy. The cantilever we have used has very low stiffness of 0.006 N/m, and the normal force acting on the surface was much lower than the attractive force such as van der Waals force. In this low normal force limit, it was found that the frictional force did not depend on the normal force. We suggest a calibration method to estimate the attractive force from the lateral force data in this limit. The estimated attractive force between Si sample and SiN tip with radius of 10 nm was 0.4 nN in flat region and 0.65 nN at the corner of a rectangular hole.

Comparative Study of Trans-linear and Trans-impedance Readout Circuits for Optical Beam De ection Sensors in Atomic Force Microscopy

Bernard Ouma Alunda,루크오두어르오티에노,Melody CHEPKOECH,변지수,이영중 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.2

The optical beam de ection sensor remains the most popular force detection method used in atomic force microscopy. With the recent development of short cantilevers, a means for measuring small de ections at high frequencies has become a challenge. Minimizing the noise level of the readout electronics without signicantly limiting the detection bandwidth still remains a challenge. In this work, a recently proposed trans-linear readout circuit-based technique, in which necessary analog arithmetics are done in the current domain instead of the voltage domain, is compared to a more traditional trans-impedance readout circuit-based topology. Our developed trans-impedance readout circuit recorded a noise oor of 9:48 1013 V2 Hz1 compared to 1:41 1011 V2 Hz1 for the trans-linear readout circuit. Also, the measured 3 dB bandwidth of 11 MHz for the transimpedance readout circuit was slightly higher than the 10 MHz for the trans-linear readout circuit. Trans-impedance readout circuits, with proper circuit design considerations and careful selection of electronic parts, still remain competitive for use in high-speed operations in atomic force microscopy.

Visualization of Bonghan Microcells by Electron and Atomic Force Microscopy

백구연,오가이,Sae Chae Jeoung,소광섭 사단법인약침학회 2009 Journal of Acupuncture & Meridian Studies Vol.2 No.2

Abstract Objectives: The origin of adult stem cells remains an open question. If they derive from embryos, it is difficult to determine the mechanism which interrupts their differentiation during tissue formation. In the 1960s, the Bonghan microcell was suggested as one possible, yet to be described, route of stem cell production, such that they have the potential to proliferate to produce normal cells. Materials and Methods: In this study, Bonghan microcells were isolated from Bonghan tissues on rat organ surfaces, and their detailed morphology examined by electron and atomic force microscopy. Results: The ultrastructure observed distinguished them from apoptotic bodies and other microorganisms, and their unique, possible proliferation feature, as protruding threads, was imaged by atomic force microscopy. Conclusions: The unique threadlike structure of the Bonghan microcell is consistent with Prof. Kim's observation in the first step of making a cell. Understanding of the functions of this threadlike structure may give a clue to understand the origin or the differentiation cue of adult stem cells.

원자현미경을 이용한 마이토마이신 노출 시간에 따른 공막 표면 콜라젠의 변화 관찰

이희재,최삼진,정유진,정경복,진경현,박헌국,이승준,Hui-Jae Lee,MD,Samjin Choi,PhD,Youjin Cheong,MD,PhD Candidate,Gyeong Bok Jung,PhD,Kyung-Hyun Jin,MD,Hun-Kuk Park,MD,PhD,Seung Jun Lee,MD 대한안과학회 2011 대한안과학회지 Vol.52 No.6

Purpose: To investigate the effects of mitomycin C on the scleral collagen surfaces using atomic force microscopy (AFM). Methods: Two non-contact mode AFM machines were used to observe changes in the morphological characteristics of human scleral surfaces before and after one, three, and five minutes of 0.02% mitomycin C application. Based on AFM topography and deflection images of the collagen fibril, the morphological characteristics of scleral fibrils including the fibril diameter and D-period were measured using the line profile. Results: The sclera collagen fibril treated with 0.02% mitomycin C for one minute did not show any significant increases in mean fibril diameter (155.04 ± 17.46 nm) or mean D-periodicity (70.02 ± 3.33 nm), compared to those of the control group. However, the scleral collagen fibrils treated with 0.02% mitomycin C for three and five minutes showed significant increases in mean fibril diameter (182.33 ± 16.33 nm, 199.20 ± 12.40 nm, respectively) and mean D-periodicity (70.27 ± 13.66 nm, 72.75 ± 19.32 nm, respectively), compared to those of the control group. Conclusions: The present study examined the structural changes in the scleral collagen fibrils before and after mitomycin C application according to atomic force microscopy. The results indirectly suggest that three or more minutes of 0.02% mitomycin C application affects the morphology of scleral collagen. J Korean Ophthalmol Soc 2011;52(6):671-678

Analytical Study of Noise Spectral Density in -controlled Atomic Force Microscopy

이만희,안상민,제원호 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.3

Q-controlled atomic force microscopy utilizes an oscillating probe with an adjustable qualityfactor, which is done by adding a variable damping interaction to the probe. While the Q-controlcan enhance the probe sensitivity by increasing the Q-factor, the applied interaction increases thenoise of the probe motion as well. Thus, the signal-to-noise ratio (SNR) associated with the probesensitivity varies accordingly. Here, we analytically derive the noise spectral density of the tipmotion, and theoretically investigate the SNR in Q-controlled atomic force microscopy. We showthat both the overall tip-motion signal and the noise monotonically increase with the effective Qfactorunder control, whereas the SNR exhibits a global minimum near the original Q value andasymptotically scales as the square root of the effective Q-factor. Therefore, in general, the Qcontroltechnique can be used to alter the quality factor, the magnitudes of signal and noise, andthe probe sensitivity in amplitude-modulation atomic force microscopy.

Multiple Pivot loading 방법을 이용한 액체 환경에서의 수평방향 힘 교정

김류운(Lyu-Woon Kim),정구현(Koo-Hyun Chung) 한국트라이볼로지학회 2013 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.29 No.2

Quantifying the nanoscale force between the atomic force microscopy (AFM) probe of a force-sensing cantilever and the sample is one of the challenges faced by AFM researchers. The normal force calibration is straightforward; however, the lateral force is complicated due to the twisting motion of the cantilever. Force measurement in a liquid environment is often needed for biological applications; however, calibrating the force of the AFM probes for those applications is more difficult owing to the limitations of conventional calibration methods. In this work, an accurate nondestructive lateral force calibration method using multiple pivot loading was proposed for liquid environment. The torque sensitivity at the location of the integrated probe was extrapolated based on accurately measured torque sensitivities across the cantilever width along a few cantilever lengths. The uncertainty of the torque sensitivity at the location of the integrated tip was about 13%, which is significantly smaller than those for other calibration methods in a liquid environment.

Visualization of Bonghan Microcells by Electron and Atomic Force Microscopy

Baik, K.Y.,Ogay, V.,Jeoung, S.C.,Soh, K.S. Elsevier 2009 Journal of Acupuncture & Meridian Studies Vol.2 No.2

Objectives: The origin of adult stem cells remains an open question. If they derive from embryos, it is difficult to determine the mechanism which interrupts their differentiation during tissue formation. In the 1960s, the Bonghan microcell was suggested as one possible, yet to be described, route of stem cell production, such that they have the potential to proliferate to produce normal cells. Materials and Methods: In this study, Bonghan microcells were isolated from Bonghan tissues on rat organ surfaces, and their detailed morphology examined by electron and atomic force microscopy. Results: The ultrastructure observed distinguished them from apoptotic bodies and other microorganisms, and their unique, possible proliferation feature, as protruding threads, was imaged by atomic force microscopy. Conclusions: The unique threadlike structure of the Bonghan microcell is consistent with Prof. Kim's observation in the first step of making a cell. Understanding of the functions of this threadlike structure may give a clue to understand the origin or the differentiation cue of adult stem cells.

Atomic Force Microscopy와 신경망을 이용한 플라즈마 진단

박민근(Mingun Park),김병환(Byungwhan Kim) 대한전기학회 2006 정보 및 제어 심포지엄 논문집 Vol.2006 No.1

A new diagnosis model was constructed by combining atomic force microscopy (AFM), wavelet, and neural network, Plasma faults were characterized by filtering AFM-rneasured etch surface roughness with wavelet. The presented technique was evaluated with the data collected during the etching of silicon oxynitride thin film. A total of 17 etch experiments were conducted. Applying wavelet to AFM, surface roughness was detailed into vertical, horizontal, and diagonal components. For each component, neural network recognition models were constructed and evaluated. Comparisons revealed that the vertical component-based model yielded about 30% improvement in the recognition accuracy over others. The presented technique was evaluated with the data collected during the etching of silicon oxynitride thin film. A total of 17 etch experiments were conducted.

Ex-situ atomic force microscopy on the growth mode of SrRuO3 epitaxial thin film

김보라,이상아,설대희,최우석,김윤석 한국물리학회 2017 Current Applied Physics Vol.17 No.12

The functional properties of devices based on perovskite oxides depend strongly on the growth modes that dramatically affect surface morphology and microstructure of the hetero-structured thin films. To achieve atomically flat surface morphology, which is usually a necessity for the high quality devices, understanding of the growth mechanism of heteroepitaxial thin film is indispensable. In this study, we explore heteroepitaxial growth kinetics of the SrRuO3 using intermittent growth scheme of pulsed laser epitaxy and ex-situ atomic force microscopy. Two significant variations in surface roughness during deposition of the first unit cell layer were observed from atomic force microscopy indicating the possible formation of the half unit cell of the SrRuO3 before the complete formation of the first unit cell. In addition, layer-by-layer growth mode dominated during the first two unit cell layer deposition of the SrRuO3 thin film. Our observation provides underlying growth mechanism of the heteroepitaxial SrRuO3 thin film on the SrTiO3 substrate during the initial growth of the thin film.