Growth and Characterization of Transition Metal Phosphochalcogenide Compounds, Alloys, and Superlattices

本文提出的研究目标是应用分子束外延的一种变体，即范德华外延，以过渡金属磷酸硫族化合物（MPX3）为基础合成新的化合物和超晶格。追求这一领域的主要动机是与高温铜超导体在质量上的相似性。因此，将寻求替代的高Tc材料。目前已知的过渡金属MPX3化合物都是相关的反铁磁绝缘体，具有类似于MX2化合物的准二维层状结构。气相外延所允许的合成灵活性将允许系统地改变有效的单电子带宽度和有效的现场相关能，以诱导绝缘体-金属转变，从而生产具有新颖和潜在有用的输运、光学和磁性质的材料。具体来说，i)已知MPX3化合物的数量将增加到包括4d和5d金属，ii)随机合金M'yM1-yPX3将被生长以诱导n型或p型掺杂，iii)将MPX3化合物与各种具有不同介电性能的层状材料结合在一起的超晶格将被产生。这些新材料和结构将以各种技术为特征。＊＊＊

9308854 Kevan The goal of the proposed research is to apply a variant of molecular beam epitaxy called van der Waals epitaxy to synthesize novel compounds and superlattices based upon transition metal phosphochalcogenide (MPX3) compounds. The primary motivation to pursue this area is a qualitative similarity to the high temperature cuprate superconductors. Alternative high Tc materials will thus be sought. The currently known transition metal MPX3 compounds are all correlated antiferromagnetic insulaators and have a quasi-two-dimensional layered structure similar to MX2 compounds. The synthetic flexibility allowed by vapor phase epitaxy will allow systematic variation of effective one-electron band widths and effective on-site correlation energies to induce an insulator-metal transition, thereby producing materials with novel and potentially useful transport, optical, and magnetic properties. Specifically, i) the number of known MPX3 compounds will be increased to include 4d and 5d metals, ii) random alloys M'yM1-yPX3 will be grown to induce n- or p-type doping, and iii) superlattices combining MPX3 compounds with a variety of layered maaaaterials having divergent dielectric properties will be produced. These new materials and structures will be characterized by a variety of techniques. ***