講演会

「Tonchev先生 講演会」
日 時

2016年8月3日(水)14:00より(1時間半程度)

会 場

大阪電気通信大学 寝屋川キャンパス エレ研新棟(W号館)2階会議室
寝屋川市初町18-8 電話 072-824-1131
(京阪電鉄 寝屋川市駅より 徒歩10分)
アクセス
キャンパスマップ

参 加 費

無料(事前にお申し込みください)

主 催

大阪電気通信大学学術研究教育国際交流助成基金

協 賛

大阪電気通信大学エレクトロニクス基礎研究所

大阪電気通信大学学術研究教育国際交流助成基金及びエレクトロニクス基礎研究所では、The 18th International Conference of Crystal Growth and Epitaxy (ICCGE-18, Nagoya, August 7-12, 2016) に参加されるために来日した Tonchev先生をお招きして結晶表面に発生するstep bunching 現象に関する講演会を開催します。卒研生・院生を含め て、多くの皆様の来聴を歓迎します。

Diffusion-limited (DL) vs. kinetics-limited (KL) crystal growth: Numerical and analytical models
Vesselin Dimitrov Tonchev 准教授(Rostislaw Kaischew Institute of Physical Chemistry, Sofia, Bulgaria)

In the introductory part of the talk, the transition from DL- to KL-regime is illustrated using a 2D model based on Cellular Automata (CA). In it, similarly to the model of diffusion-limited aggregation (DLA), the growth starts from a seed but, differently from the DLA, proceeds by applying the automaton rule to all lattice sites in parallel with all particles spread on the lattice from the beginning and their number not sustained further (“batch crystallization mode”). The time is measured in parallel growth updates and between two consecutive ones, nDS diffusional updates are performed that include only the single particles but not those belonging already to the crystal aggregate. When nDS = 1 the growth is DL with fractal dimension of the aggregates ~1.68, but with increasing nDS smoothly the fractal dimension of the aggregates also increases [1] to reach ~2 for nDS of ~200.

In the main part are presented models of unstable vicinal crystal growth. In particular, they resolve the long-standing controversy between numerical results on the minimal step-step distance lmin in bunches and predictions of continuum theory - while the size-scaling exponent of lmin is found the same in diffusion-limited (DL) and kinetics-limited (KL) regime, and the time-scaling exponent of the bunch size N is predicted also to be the same (=1/2), the scaling exponents of the bunch width W and lmin are predicted to distinguish in between. With extensive calculations on the model of Sato and Uwaha (SU) we solve the puzzle. Results from other models are discussed as well: vicinal Cellular Automata (vicCA) [2], strain-induced step bunching [3], etc. Especially, for the vicCA it is the time-scaling exponent of the macrostep size Nm that makes the difference.

In the concluding part is introduced a simplest analytical model of crystal growth – that of N equally-sized crystals growing in batch crystallization mode independently of the others and in DL-regime at the same growth rate thus remaining with the same linear size. The considerations employ conservation law and kinetic equation and result in obtaining the universal curve of the model in the rescaled coordinates (Time, Supersaturation, Size) [4]. Further, the possible transitions between kinetic regimes, quantified by the power g with which the supersaturation enters into the expression for the normal growth rate of the crystal are considered [5].

[1] D Goranova, R Rashkov, G Avdeev, V Tonchev, J. Mat. Sci 51, (2016) 8663.
[2] F Krzyżewski, M Załuska-Kotur, A Krasteva, H Popova, V Tonchev, arXiv:1601.07371.
[3] A Krasteva, H Popova, N Akutsu, V Tonchev, AIP Conference Proceedings 1722, (2016) 220015.
[4] C.Nanev, V.Tonchev, F.Hodzhaoglu, J. Cryst. Growth 375, (2013) 10.
[5] V. Tonchev, G. As. Georgiev, P. Vekilov, C. Nanev, prepared for publication.

【問い合わせ】

大阪電気通信大学工学部 阿久津典子
tel: 072-824-1131(内線2267)
e-mail akutsu@osakac.ac.jp

【参加申し込み】

大阪電気通信大学エレクトロニクス基礎研究所 古賀 弘
tel: 072-824-1131(内線2588) fax: 072-820-9010
e-mail feri@isc.osakac.ac.jp