Epitaksiyel Olarak Gerilmiş İzotropik İnce Filmlerde Elastik Etkileşim Nedenli Morfolojik Değişimin Doğrusal Kararlılık ve Sayısal Analizi

Year 2022, Volume: 3 Issue: 1, 21 - 33, 30.06.2022

Aytaç Çelik

https://doi.org/10.53501/rteufemud.1088954

Abstract

Bu sistematik sayısal analiz çalışmasında ince film yüzeyinin kararlılığı, elastik dipol etkileri de göz önünde bulunduran matematiksel model ile farklı çeki kuvvetleri altında kararlılığı incelenmiştir. Bu modelde yüzey difüzyonuna gerilmenin etkisi birinci ve ikinci dereceden iki terim ile ifade edilmektedir. İnce film yüzeyinin sinüs dalgası şekillinde olduğu varsayılmış ve bu dalga yapısının yüzeydeki gerilme nedenli difüzyon ile sönümlenme veya büyüme dinamikleri incelenerek kararlılığı test edilmiştir. Elastik dipol etkileşimlerin basma ve çekme gerilmeleri altında farklı yüzey dinamiklerine sebep olduğu, bu farkın kritik basma gerilmesi (σ>100 MPa) üzerindeki basma gerilmesi durumunda çatlak benzeri yapıların oluşmasına neden olduğu gösterilmiştir. Çekme gerilmesine maruz kalan yüzeydeki dalgalı yapının sönümlendiği gözlemlenmiştir. Çatlak yapıların oluşumu sonrası yüzey kinetiği doğrusal kararlılık analizlerinden uzaklaşmaktadır. Uygulanan gerilmeye göre 3 farklı davranış saptanmıştır. Bunlar; sönümlenmenin gerçekleştiği (Ξ >0) çekme kuvveti uygulanan bölge, düşük basma kuvveti (-1,12>Ξ > 0) uygulanan yüzeyin karalı olduğu bölge ve çatlak benzeri oluşumların gözlemlendiği yüksek basma gerilmesinin (Ξ<-1,12) uygulandığı bölgedir. Yapılan simülasyonlarda, çatlak oluşumu sürecinde, çatlak bölgeden difüzyon ile kaçan maddenin tepelerde birikerek yeni tepeler oluşturduğu gözlemlenmiştir. 

Keywords

İnce film, Difüzyon, Elastik etkileşimler, Uyumsuzluk gerilmesi

Supporting Institution

TUBITAK

Project Number

107M011

Thanks

Bu çalışma TUBİTAK tarafından 107M011 nolu proje dahilinde desteklenmiştir.

Linear Instability and Numerical Analysis of Surface Morphology Changes of Epitaxially Strained Thin Films Due to Elastic Interactions

Abstract

In this systematic simulation study, thin-film surface stability has been investigated with consideration of elastic dipole interactions under compression and tension. In this model, the effect of stress on surface diffusion is introduced by first and second-order parameters. Preexistent sinusoidal wave formed surface of the thin films is assumed and decay or growth of this form due to the diffusion is investigated with the combined effect of capillary, stress, and elastic dipole interactions. It has been shown that elastic dipole interactions cause the different surface dynamics under the compression and the tension, and this difference caused crack like formations on the surface over critical compression stress (σ>100 MPa). On the other hand, wave-formed thin film surface decays with tensile stress. Three different regions were observed according to the applied stress; the area where decaying has occurred (Ξ >0) under tensile load, the region the surface is stable where the low compression force (-1,12>Ξ > 0) is applied, and the high compressive stress (Ξ<-1,12), where crack-like formations are observed. After the crack formation, surface kinetics deviates from the linear instability analysis. During the crack formation, mass flow due to the diffusion results in creating new crests at the surface or filling in the trough. 

Keywords

Thin films, Difüzyon, Elastic interactions, Misfit stress

Project Number

107M011

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