CAREER: Controlling surface and interface relaxation mechanisms through the chemical environment: A route to 2D conductors between dissimilar materials

职业：通过化学环境控制表面和界面弛豫机制：不同材料之间形成二维导体的途径

• 批准号: 1151568
• 负责人: Douglas Irving
• 金额: $ 45万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151568&HistoricalAwards=false
• 关键词: CAREER; Controlling; surface; interface; relaxation

TECHNICAL SUMMARY: This CAREER award, funded by the Condensed Matter and Materials Theory Program in the Division of Materials Research, supports an integrated theoretical research, education, and outreach effort seeking to develop a fundamental understanding of how and to what degree atomistic and electronic compensation mechanisms compete to overcome diverging electrostatic energies in polar-oriented oxide thin films and whether this competition can be tuned to enable their low defect growth. It is proposed that overcoming the barrier to low defect growth can be accomplished through the active control of the chemical environment during epitaxy. First principles based methods will be used to evaluate surface free energies, and to what degree they reorder, as a function of chemical species, partial pressure, and temperature of the growth environment. This provides critical information that can be used by experiment to determine growth conditions that yield low defect thin films. Identification of growth conditions that produce these low defect thin films is a first step towards the ultimate goal of this proposal, which is to discover new material combinations that support a two dimensional electron gas between materials of different structure or symmetry. To this end, first principles methods will also be used to predict functionality of the heterogeneous interface. The goals of the theoretical research in this proposal, which center on controlling the relative free energy of different surface terminations, feed very well into the integrated educational outreach component. Two modules will be developed that use intuitive hands on active demonstrations to excite students and illustrate the subtle physical arguments of the effects of re-ordering surface free energies. One module is experimental and the other is computational in nature. For the experimental module, students will burn Mg ribbons, harvest the MgO smoke crystals, submerge them in water, and image them with a tabletop SEM. For the computational module students will interact in real time with an atomic simulation via 3-D visualization and a force feedback haptic device. NON-TECHNICAL SUMMARY:This CAREER award, funded by the Condensed Matter and Materials Theory Program in the Division of Materials Research, supports an integrated theoretical research, education, and outreach effort with the ultimate goal of accelerating the creation of next generation interfacial electronics by use of predictive theoretical methods. Interfacial electronics are unique in that their functionality is compressed down to layers of atoms. Their creation, however, has been limited to materials that have similar atomic structure, which, in part, has limited widespread use and integration. New functionality could be expected as this type of active interface is created between interfaces of dissimilar materials. For the most part, this has not been achievable due to the inability to fabricate atomically perfect materials or materials with low defect concentrations. It is proposed that these barriers can be overcome by changing the gas phase chemistry used to deposit one material on another and that predictive simulations can be used to determine what conditions should be explored experimentally. This approach allows for the ability to focus on materials and conditions that would be expected to be fruitful, saving both time and money and, thus, accelerating the development of these new materials. Ultimately, enabling low defect interfaces between structurally dissimilar materials not only expands the catalogue of materials that can be used to create novel devices but also endows new functionality that will impact the creation of ultra-fast transistors, very high-density memory, and magnetic sensors. An educational outreach program is strongly coupled to and feeds into the proposed research. This program will have significant impact on education through the development of the visual and active demonstration modules that will be targeted to students in local high school, in local colleges, and to the general public. These modules will not only excite participants about careers in STEM related fields but will also pass along technological vocabulary, define the role of engineers in solving real world problems, and help define Materials Science and Engineering to the participants. Two experienced educators will aid in assessing the outcomes and ensure meaningful impact of the modules to a wide range of participants.

技术概要：该职业奖由材料研究部的凝聚态物质和材料理论项目资助，支持综合理论研究，教育，和推广努力，寻求发展如何以及在何种程度上原子和电子补偿机制竞争，以克服两极分化的静电能的基本理解，取向的氧化物薄膜，以及是否可以调整这种竞争以使其能够低缺陷生长。 有人提出，克服低缺陷生长的障碍，可以通过在外延过程中的化学环境的主动控制来完成。基于第一原理的方法将用于评估表面自由能，以及它们重新排序的程度，作为生长环境的化学物质、分压和温度的函数。这提供了关键的信息，可用于实验，以确定生产低缺陷薄膜的生长条件。确定产生这些低缺陷薄膜的生长条件是实现该提议的最终目标的第一步，该提议的最终目标是发现支持不同结构或对称性的材料之间的二维电子气的新材料组合。为此，第一原理方法也将被用来预测功能的异构接口。本提案中的理论研究目标集中在控制不同表面终端的相对自由能上，非常好地融入了综合教育推广部分。 将开发两个模块，使用直观的手在积极的示范，激发学生，并说明重新排序表面自由能的影响微妙的物理参数。一个模块是实验性的，另一个是计算性的。 对于实验模块，学生将燃烧镁带，收获MgO烟雾晶体，将它们浸泡在水中，并用桌面SEM对其进行成像。对于计算模块，学生将通过3-D可视化和力反馈触觉设备与原子模拟进行真实的交互。非技术总结：该职业奖由材料研究部的凝聚态物质和材料理论计划资助，支持综合理论研究，教育和推广工作，最终目标是通过使用预测理论方法加速下一代界面电子器件的创建。界面电子的独特之处在于它们的功能被压缩到原子层。然而，它们的创造仅限于具有类似原子结构的材料，这在一定程度上限制了广泛的使用和集成。由于这种类型的主动界面是在不同材料的界面之间创建的，因此可以预期新的功能。在大多数情况下，由于无法制造原子级完美的材料或具有低缺陷浓度的材料，这是无法实现的。有人提出，这些障碍可以克服通过改变气相化学用于存款一种材料上的另一个和预测模拟可以用来确定什么条件下应该探索实验。这种方法可以专注于预期富有成效的材料和条件，节省时间和金钱，从而加速这些新材料的开发。最终，在结构不同的材料之间实现低缺陷界面不仅扩大了可用于制造新型器件的材料目录，而且还赋予了新的功能，这将影响超快晶体管、超高密度存储器和磁传感器的制造。一个教育推广计划与拟议的研究密切相关。该方案将通过开发针对当地高中学生、当地大学学生和公众的视觉和主动示范模块，对教育产生重大影响。这些模块不仅将激发参与者对STEM相关领域的职业生涯，而且还将通过沿着技术词汇，定义工程师在解决真实的世界问题中的作用，并帮助参与者定义材料科学与工程。两名经验丰富的教育工作者将帮助评估结果，并确保模块对广泛的参与者产生有意义的影响。