Applications of dewetting in micro and nanotechnology

Abstract

Dewetting is a spontaneous phenomenon where a thin film on a surface ruptures into an ensemble of separated objects, like droplets, stripes, and pillars. Spatial correlations with characteristic distance and object size emerge spontaneously across the whole dewetted area, leading to regular motifs with long-range order. Characteristic length scales depend on film thickness, which is a convenient and robust technological parameter. Dewetting is therefore an attractive paradigm for organizing a material into structures of well-defined micro- or nanometre-size, precisely positioned on a surface, thus avoiding lithographical processes. This tutorial review introduces the reader to the physical-chemical basis of dewetting, shows how the dewetting process can be applied to different functional materials with relevance in technological applications, and highlights the possible strategies to control the length scales of the dewetting process.

Non-blinking dendritic crystals from C-dot solution

“…Numerous methods of crystal growth such as high temperature growth and low temperature growth [15,16] have been reported for different types of semi-conductor crystals. In the present work, C-dots were synthesized using a microwave assisted method using Sorbitol as a precursor followed by their crystallization.…”

Colloidal Magnetic Heterostructured Nanocrystals with Asymmetric Topologies: Seeded-Growth Synthetic Routes and Formation Mechanisms

“…The shell rapidly dewetted out and evolved into a separate cubic spinel Fe 3 O 4 @γ-Fe 2 O 3 core@shell domain attached aside, leaving a thin iron oxide shell on the diametrically opposite side of FePt (Nolle et al, 2009). Overall, this process permitted alleviating the intervening interfacial strain due to large difference (~8%) in lattice parameters between FePt and iron oxide (Erdemir et al, 2009;Nolle et al, 2009;Gentili et al, 2012;Thompson, 2012), albeit at the cost of nucleation of dislocations within the heterodimer lattice (Figuerola et al, 2008). Since each reaction step was selectively activated under distinct thermal conditions, regulation of both the temperature and the heating time guaranteed that the two material sections of the MHNCs formed at different stages of the synthesis course (Erdemir et al, 2009).…”

“…Such evolution was explained by considering that the large junction tension in the initially attained core@shell nanostructures could be greatly relieved during the annealing at high temperature, as supply of extra thermal energy promoted coalescence and dewetting of the crystallizing shell into a separate domain aside, which resulted in an obvious reduction of the interfacial area shared between the two materials. This interfacial energy gain could thus be large enough to compensate for the proportionally smaller increase in the overall surface energy that eventually accompanied formation of the non-core@shell heterostructure (Gentili et al, 2012;Thompson, 2012). In the case of the γ-Fe 2 O 3 -MeX system, the observed topological evolution was rationalized on the basis of the CSLT theory (Randle, 1997;Kwon and Shim, 2005;Kwon et al, 2006;McDaniel and Shim, 2009).…”

“…Subsequently, as the deposited layer exceeds a threshold thickness and/or reaches a critical composition (for example, in those cases in which it chemically reacts with the substrate underneath, forming an alloy or solid solution), and/or an excess of thermal energy is provided (e.g., when reaction temperature is increased), subsequent growth continuation will proceed in the form of segregated domains protruding out of the initially deposited layer (ΔG S < 0) in response to an intensification of interfacial strain fields. Exceedingly high strain fields, combined with a strong cohesive energy of the secondary material, may also led to a complete dewetting of the initially deposited thin layer and its reshaping into discrete domains (Gentili et al, 2012;Thompson, 2012).…”

Dewetting Dynamics of Ultra-Thin Liquid Films with Boundary Layer

“…緒 言 液体は、 濡れ難い条件下で Young の式に則り、 三相境界線において任意の接触角を有する部分 的濡れの状態を形成する [1]。重力環境下では、毛 管長 [2]で決定される臨界厚さよりも液膜が厚い 場合、濡れ拡がり、逆の場合、撥水することが知 られている [3]。 液体が自発的に後退する特徴を有 する撥水は、超疎水表面上の高速撥水、液膜の安 定性、 ナノ液滴の跳躍などの理学的興味 [4][5][6]に加 え、セルフクリーニング、微細構造・粒子の形成 などの工学的応用が期待されている [7][8][9]。 液膜の撥水過程に関する初めての定量的な実 験 [10]では、撥水速度は液体の粘性に大きく依存 することが観測されている [11]。一方で、低粘性 流体 [12]やポリマー [13]は基板上をスリップする ことで、撥水領域の時間依存性がRedon et al [10] の実験結果とは異なる挙動が報告されている。こ れらの撥水過程は、Navier-Stokes方程式を潤滑近 似 [2]して得られる液膜内部の速度分布を議論す ることで体系的に理解でき、特に高速な撥水が起 こる低粘性流体の条件では、慣性領域（I） 、粘慣 性領域（VI） 、粘性領域（V）に大別される [14]。 慣性領域では、シャボン液膜の破裂と同様の議 論 [15,16]ができるため、液膜の撥水速度は次式で 表現される。 Ó Ô Õ ; ; Ö ×Ö ; aeØ ÓÓ ÙÚ §Û §ÛÜ_YÛÝÞßb5àYÛáâãCaÛÂPM äå ae Õ < ae = å åçèéêëì« íîï ð ñÕ ae ae ò ae Ô å < ae ae ó Õ î < ôõ ö ÷ ð ø õ ùõ ú õ ø ö ûü ý ö ôü < þ ff õ 0 ff 1 2 12ä42f óôõ05ïÝ]*+$ù RST%&26\b*+7Öî ×H2887897Öî*+9:7 8C&,;<=>2 8 9 a c? 0*+9:78C&@642789 7Ö0 9\78ABó x789CD} ÞE5FGH/Na93aba`p¡' "$1 9789ìí7/CD0EÞ*0N`9 78C& 9ab0`3I02J S¤0c f 134K0Ra93789L¹# ìaeMNO;P5±b88 9 a cd 5H bS¤0QRóô078\bp¡¬ae1W b010Sb…”