Phase Change Memory Materials via Non-Aqueous Electrodeposition into Nano-structured Templates

该项目涉及开发非水电化学方法和合适的定制试剂，以促进二元(例如In2(Se,Te)3, Sb2（Se,Te)3, Ge(Se,Te)）和三元硫系材料（例如Ge2Sb2Te5，掺杂Sb2Te3）的空间选择性电沉积，用于固态相变存储器（PCM）。关键目标是证明目标材料在纳米级（低至2纳米）受限细胞结构内的成功沉积，并确定降尺度孔径对沉积过程的影响。成功电沉积这些类型的明确定义的化合物半导体合金成分将提供一种重要的新使能技术，也可能对需要在纳米尺度上沉积半导体合金的其他应用产生重大影响。使用非水溶剂（如甲基萘甲酸酯、碳酸丙烯酯或氯氟化碳）将比水处理带来几个优势：(i)使用范围更广的试剂，可以根据应用进行定制；（ii）获得更活泼的合金成分；（iii）更宽的沉积电位范围，而这些溶剂更容易获得，更便宜，更容易净化和更少的粘性（对穿透狭窄很重要）。高宽高比的孔隙)比离子液体要多。这些硫系合金是相变存储器（PCM）材料的主要兴趣-一种新兴的非易失性存储器技术，有望与专业和日常消费电子产品中的闪存竞争（甚至取代）。与目前的生产方法（主要是PVD）相比，通过电沉积生产这些合金可以带来几个优势，因为它允许空间选择性沉积（因为材料只沉积在电极表面），从底部填充模板的孔隙，因此可以完全填充非常狭窄的纳米孔-导致每个单个电池的尺寸显着减小，因此可能会有更高的电池密度。反过来，这将导致晶体和非晶体相之间更快的转换，从而导致更小的设备和更高的能源效率。要实现这些目标，需要多学科方法，涉及几个关键贡献：(i)开发（和改进）新的定制分子化合物（电化学试剂），将p-区块的元素（镓、铟、锗、锑）与含有硫原的基团（即元素硒和碲）结合；（ii）使用这些作为试剂，通过电化学沉积将二元和三元合金材料生长到纳米结构的二氧化硅或氧化铝模板中，模板由非常狭窄的平行孔组成，直径在1000纳米到2纳米之间；（iii）表征沉积材料，以确定存在的元素比例（组成）、晶体结构和相变特性；（iv）将“最佳”组合物沉积到芯片阵列上定义良好的孔隙中，从而允许在实际设备中切换阵列存储单元，从而展示了这种新方法的真正潜力。为了实现这些目标，研究团队汇集了一套互补的、国际上独一无二的技能和专业知识，而我们的项目合作伙伴Ilika Technologies Ltd的投入将为该项目增加相当大的价值。

This project is concerned with developing non-aqueous electrochemical methods and suitably tailored reagents to facilitate spatially selective electrodeposition of binary (e.g. In2(Se,Te)3, Sb2(Se,Te)3, Ge(Se,Te)) and the ternary chalcogenide materials (e.g. Ge2Sb2Te5, doped Sb2Te3) for applications in solid-state phase change memory (PCM). The key objectives are to demonstrate successful deposition of the target materials inside nano-scale (down to 2 nm) confined cell structures and to establish the effect of down-scaling pore size on the deposition process. Successful electrodeposition of well-defined compound semiconductor alloy compositions of these types will provide a significant new enabling technology which could also have a major impact on the other applications requiring semiconductor alloy deposition on a nano-scale. Using non-aqueous solvents (such as MeCN, propylene carbonate or chlorofluorocarbons) will bring several advantages over aqueous processes:(i) the use of a much wider range of reagents which can be tailored to the application;(ii) access to more reactive alloy compositions;(iii) a wider range of deposition potentials,while these solvents are more readily available, less expensive, much more easy to purify and less viscous (important for penetrating narrow. high aspect-ratio pores) than for example ionic liquids.These chalcogenide alloys are of major interest for phase change memory (PCM) materials - an emerging technology for non-volatile memory which is expected to compete with (and even replace) FLASH memory in specialist and everyday consumer electronics. Production of these alloys by electrodeposition could bring several advantages over current methods of production (mainly PVD), since it allows spatially selective deposition (since the materials are only deposited on the electrode surface), filling the pores of the templates from the bottom, hence enabling complete filling even of very narrow nanopores - leading to a very significant reduction of the dimensions of each individual cell, and hence potentially much higher cell density. In turn this will lead to faster switching between the crystalline and non-crystalline phases, leading to smaller devices and greater energy efficiency. To achieve these targets requires a multidisciplinary approach involving several key contributions: (i) to develop (and refine) new tailored molecular compounds (electrochemical reagents) with elements from the p-block (gallium, indium, germanium, antimony) in combination with groups containing the chalcogens i.e. the elements selenium and tellurium; (ii) to use these as reagents for the growth of the binary & ternary alloy materials by electrochemical deposition into nano-structured silica or alumina templates comprised of very narrow parallel pores with well-defined diameters between 1000 nm and 2 nm; (iii) characterisation of the deposited materials to determine the element ratios present (composition), their crystal structures, and phase change properties;(iv) deposition of the 'best' compositions into well-defined pores on a chip array to allow switching of the arrays memory cells in an actual device, hence demonstrating the true potential of this new approach.The team of investigators brings together a complementary and internationally unique set of skills and expertise to achieve these targets, while the input from our Project Partners, Ilika Technologies Ltd will add considerable value to the project.