Synthesis and polarity driven alignment of ZnO crystallites

该项目的重点是制造具有固有取向极性的氧化锌晶体，以及这种材料基于其结晶度和取向的特殊电气和机械性能。其目的是实现各向异性的微观结构，使极化在压应力下的变化，从而调制跨结的电荷载流子传输。为此目的，纳米和微米尺寸的氧化锌微晶将以受控的方式合成并以定向的方式沉积。几种技术将被应用于获得从薄到厚的薄膜在基板上的对象，从而可以使用额外的处理或烧结步骤。如果适当调整合成条件，则可以获得具有介观和微米尺寸的ZnO晶粒的多晶结构。首先，必须合成合适尺寸的ZnO单晶，从而需要具有窄尺寸分布的均匀颗粒。ZnO微晶的受控排列是一个合成挑战，将使用三种不同的方法进行研究：（a）通过电场（B）通过毛细管力（对流组装）或（c）通过有机模板（自组装单层或逐层堆叠的聚电解质）。压电材料的电泳沉积（a）被建立用于沉积压电材料，产生尺寸在微米至毫米范围内的独立陶瓷体。因此，本文将首次研究这种方法用于沉积具有交替取向极性的层。通过对流组装（B）的ZnO片晶的排列和堆叠提供了用于单层和多层的受控形成的途径。有机模板（c）可以与专门合成的颗粒的沉积以及与来自化学浴的原位形成的陶瓷ZnO层组合。找到最佳的合成沉积技术，允许ZnO晶体的可控合成和组装，以产生具有定向极性的所需沉积，是该项目的两项中心任务和具有挑战性的目标，该项目是压电电阻效应和电导率机械调制领域联合研究工作的一部分。因此，与Klein、Albe、Rödel/Kleebe和Gjonaj/Xu等合作伙伴项目的互动至关重要。我们的工作基本上有助于科学问题：化学成分，粒子取向及其在界面上的电子结构如何影响电导率和应变的依赖性？我们的材料选择将理想地补充由Rödel/Kleebe项目处理的宏观ZnO双晶的研究。同样，该提案也将受益，但也将为PAK 928/1的其他组提供材料专业知识。

The project focuses on the fabrication of zinc oxide crystals with an inherent oriented polarity as well as the particular electrical and mechanical properties of this material based on its crystallinity and orientation. The aim is to achieve an anisotropic microstructure which enables the alteration of the polarisation under compressive stress and thus the modulation of charge carrier transport across junctions. For this purpose nano- and micrometre sized crystallites of zinc oxide will be synthesized in a a controlled fashion and deposited in an oriented manner. Several techniques will be applied to obtain objects ranging from thin to thick films on substrates whereby additional processing or sintering steps can be used. If the synthetic conditions are suitably adapted, a polycrystalline structure with meso- and microsized ZnO grains will become accessible. First, ZnO single crystals of suitable size must be synthesized, whereby uniform particles with a narrow size distribution are required. The controlled alignment of the ZnO crystallites is a synthetic challenge and will be studied using three different approaches: (a) induced by electrical fields (b) by capillary forces (convective assembly) or (c) by organic templates (self-assembled monolayers or layer-by-layer stacks of polyelectrolytes). The electrophoretic deposition (a) of piezoelectric materials is established for the deposition of piezoelectric materials yielding free standing ceramic bodies with dimensions in the regime of micro to millimetres. This method will consequently be studied for the deposition of layers with alternating oriented polarity herein for the first time. The alignment and stacking of ZnO platelets by means of convective assembly (b) provides a route for a controlled formation of mono and multilayers. Organic templates (c) could be combined with the deposition of dedicatedly synthesized particles as well as with in-situ formed ceramic ZnO layers from chemical baths. Finding the optimum synthetic deposition techniques which allow a controlled synthesis of ZnO crystals and the assembly of those to yield their desired deposition with oriented polarity are the two central tasks and challenging goals of the project which is part of the joined research effort in the field of piezoresisitive effects and mechanical modulation of electrical conductivity. Therefore the interaction with the partner projects; Klein, Albe, Rödel/Kleebe and Gjonaj/Xu is essential. Our work contributes essentially towards scientific questions as: How do chemical composition, particle orientation and its electronic structure at interfaces affect the dependence of electrical conductivity and strain? Our materials choice will ideally supplement the studies of macroscaled ZnO bicrystals treated by the Rödel/Kleebe project. Likewise this proposal will benefit but will also provide materials expertise for use in the other groups of PAK 928/1.