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RF 마그네트론 스퍼터링 공정 조건에 따른AlN 박막의 배향성, 표면 거칠기 및 압전 특성에 관한 연구
방정호,윤영섭,강성준,장동훈,김동국 대한전자공학회 2006 電子工學會論文誌-SD (Semiconductor and devices) Vol.43 No.4
AlN thin films have been fabricated by using RF magnetron sputtering method and their crystal orientations, microstructures and piezoelectric properties have been investigated with variation of the Ar/N2 gas ratio and the substrate temperature. Particularly, when the Ar/N2 gas ratio and the substrate temperature are 10/10 (sccm) and 400℃, respectively, the AlN thin film exhibits the highest (002) orientation. The result of the surface roughness measurement by using AFM shows that the surface roughness becomes better as the partial pressure of N2 increases at the substrate temperature of 400℃ and it becomes the smallest value of 2.1 nm when Ar/N2 is 0/20 (sccm). The AFM measurement also shows that when Ar/N2 is 10/10 (sccm) shows that surface roughness becomes better as the substrate temperature increases from room temperature up to 300℃ and then it becomes worse as the substrate temperature goes up from 300℃. At the substrate temperature of 300℃ and Ar/N2=10/10 (sccm), the surface roughness is 3.036 nm. The piezoelectric constant (d33) of AlN thin film is measured by Pneumatic probe method. The measurement shows that the AlN thin film with the highest (002) orientation, fabricated at Ar/N2=10/10 (sccm) and the substrate temperature of 400℃, has the best piezoelectric constant (d33) of 6.01 pC/N. RF 마그네트론 스퍼터링 방법을 이용하여 Ar/N2 가스비와 기판 온도 변화에 따른 AlN 박막의 배향성과 표면 거칠기 그리고 압전 특성의 변화를 조사하였다. 특히, Ar/N2=10/10 (sccm), 기판 온도 400℃ 일 때 가장 우수한 (002) 배향성을 얻을 수 있었다. AFM 을 이용하여 표면 거칠기를 분석한 결과, 기판 온도 400℃ 인 경우 Ar/N2 가스비의 변화에 대해서는 N2 의 분압비가 증가할수록 표면 거칠기 특성이 좋아지는 것으로 나타났으며 Ar/N2=0/20 (sccm) 일 때 2.1 nm 로 가장 작은 값을 나타내었다. Ar/N2=10/10 (sccm) 인 조건에서 기판 온도 변화에 대한 표면 거칠기 특성은 기판 온도가 상온에서 300℃ 로 증가함에 따라 향상되는 경향을 보였으며, 300℃ 에서 3.036 nm 로 최소값을 나타낸 후, 기판 온도가 300℃ 이상으로 상승하면 표면 거칠기는 다시 열악해지는 것을 확인할 수 있었다. Pneumatic probe 방법을 이용하여 압전 특성을 측정한 결과, Ar/N2=10/10 (sccm), 기판 온도 400℃ 일 때 piezoelectric constant (d33)=6.01 pC/N 이라는 가장 우수한 값을 나타내었으며, 이는 AlN 박막이 가장 좋은 (002) 배향성을 갖는 조건과 일치하는 것이다.
A Quantum Heuristic Algorithm for the Traveling Salesman Problem
방정호,류정희,이창협,유석원,James Lim,이진형 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.12
We propose a quantum heuristic algorithm to solve the traveling salesman problem by generalizing the Grover search. Sufficient conditions are derived to greatly enhance the probability of finding the tours with the cheapest costs reaching almost to unity. These conditions are characterized by the statistical properties of tour costs and are shown to be automatically satisfied in the large-number limit of cities. In particular for a continuous distribution of the tours along the cost, we show that the quantum heuristic algorithm exhibits a quadratic speedup compared to its classical heuristic algorithm.
방정호,J.H. Bang 한국전자통신연구원 2023 전자통신동향분석 Vol.38 No.5
Quantum machine learning (QML) is an area of quantum computing that leverages its principles to develop machine learning algorithms and techniques. QML is aimed at combining traditional machine learning with the capabilities of quantum computing to devise approaches for problem solving and (big) data processing. Nevertheless, QML is in its early stage of the research and development. Thus, more theoretical studies are needed to understand whether a significant quantum speedup can be achieved compared with classical machine learning. If this is the case, the underlying physical principles may be explained. First, fundamental concepts and elements of QML should be established. We describe the inception and development of QML, highlighting essential quantum computing algorithms that are integral to QML. The advent of the noisy intermediate-scale quantum era and Google's demonstration of quantum supremacy are then addressed. Finally, we briefly discuss research prospects for QML.
방정호,유석원 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.12
We propose a genetic-algorithm-based method to find the unitary transformations for any desiredquantum computation. We formulate a simple genetic algorithm by introducing the “geneticparameter vector” of the unitary transformations to be found. In the genetic algorithm process,all components of the genetic parameter vectors are supposed to evolve to the solution parametersof the unitary transformations. We apply our method to find the optimal unitary transformationsand to generalize the corresponding quantum algorithms for a realistic problem, the one-bit oracledecision problem, or the often-called Deutsch problem. By numerical simulations, we can faithfullyfind the appropriate unitary transformations to solve the problem by using our method. We analyzethe quantum algorithms identified by the found unitary transformations and generalize the variantmodels of the original Deutsch’s algorithm.
과학기술분야의 외래어규범화에서 제기되는 몇가지 문제에 대하여
방정호(方正浩) 길림성민족사무위원회 2020 중국조선어문 Vol.225 No.-
과학기술의 발전과 함께 생겨나는 수많은 과학기술용어들 특히 다른 나라에서 생겨난 과학기술분야의 외래어들을 해당 민족어에 받아들여 쓰는데서는 여러가지의 문제들이 제기된다. 본 론문은 과학기술분야의 외래어를 받아들이는데서 제기되는 일반적, 원칙적문제와 함께 표기상의 문제를 서술함으로써 외래어규범화에 대한 리해를 가지도록 하는데 목적을 두었다.