Quantum Interfaces of Dissimilar Materials

非技术描述：该项目专注于研究当两种具有不同性质的材料（如半导体和铁电材料）耦合在一起时产生的新量子材料特性。人们可能期望发现所得的材料性质是每种材料性质的总和。然而，当每种材料的层只有几个原子厚时，这种情况就会改变，从而形成量子界面材料。例如，原子之间的短程键合主导着半导体材料的特性，而在铁电体中，原子之间的键合主要是远程的。将两种材料结合在一个界面上，形成了一种混合键，形成了令人兴奋的新量子材料功能。铁电氧化物中的极化允许调谐和控制半导体电子和光学特性，以实现更小、更快的电子器件。同样，利用半导体中的移动电荷来影响铁电体的极化，为更小更快的存储设备创造了机会。基本上，界面是一种“新量子材料”，它为研究量子效应创造了新的有趣的可能性，比如分数量子霍尔效应，以及电子的操纵，电流的控制，电子自旋，以及材料与光的相互作用。这些是电子和光子学领域新发现和令人兴奋的新产品的新科学和技术机会的基本成分。本研究为研究生和本科生提供了机会，他们将自己的兴奋带到区域中学教室和公共场所，即阿肯色州购物中心，以激发对科学教育的探究。认识到妇女和少数民族在科学领域的需要，在每年的全国黑人和西班牙裔国家会议和材料研究学会（MRS）会议上招收学生。技术描述：该项目在单层尺度上研究半导体-过渡金属氧化物量子界面的性质。由于结构性质和晶格参数的差异，外延生长的难度很大。然而，这一挑战已被证明是非常理想的，可以通过分子束外延在层接层的生长中取得进展，具有原子尺度扫描隧道显微镜和光谱学以及压电力显微镜的原位表征能力，并且是本提案所采用的方法。例如，研究小组正在BaTiO3（110）上生长GaAs（001）、InGaAs（001）和GaAsP（001）的单层，在SrTiO3（110）上生长BiFeO3(110)，以产生过渡金属-半导体量子界面。为了进行分析，该团队正在使用扫描隧道和压电力显微镜进行形态学和光谱分析，通过提供交互式反馈来提供实时数据，以了解从单层到10-20纳米厚度的界面。对于不同材料之间的界面，该团队正在评估局部态密度、极化筛选、表面重建、电场和磁场耦合、sp电子和d电子之间的键合、分数量子霍尔效应、电荷的局域化以及晶格匹配、失配和应变对界面电子和光子特性的影响。作为一个高风险的令人兴奋的机会，该团队正在使用高质量的半导体/过渡金属氧化物和过渡金属氧化物/半导体界面，堆叠界面，形成具有新特性的量子界面的超晶格。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: This project is focused on investigating new quantum material properties that are provoked when two materials with dissimilar properties, such as, semiconductor and ferroelectric materials, are coupled together. One may expect to find the resulting material properties to be the sum of the properties of each material. However, this situation changes when the layers of each material are only a few atoms thick, creating a quantum interface material. For example, whereas short-range bonding between atoms dominates the material properties of semiconductors, in ferroelectrics the bonding between atoms is predominantly long-range. Combining the two materials at one interface creates a hybrid bonding that forms exciting new quantum material functionalities. The polarization in the ferroelectric oxide allows tuning and controlling the semiconductor electronic and optical properties for smaller and faster electronics. Likewise, mobile charges in the semiconductor is exploited to affect the polarization in the ferroelectric, creating the opportunity for smaller and faster memory storage devices. Basically, the interface is a "new quantum material" that creates new intriguing possibilities to investigate quantum effects, such as the fractional quantum Hall effect, as well as the manipulation of electrons, control of electrical current flow, electron spin, and the material interaction with light. These are the fundamental ingredients for novel scientific and technological opportunities for new discoveries and exciting new products in electronics and photonics. This research provides opportunities to graduate and undergraduate students who bring their excitement to regional middle school classrooms and public places, i.e. Arkansas Shopping Mall, to stimulate inquiry into science education. Recognizing the need for women and minorities in science, recruitment for students is at the annual National Black and Hispanic National meeting and Materials Research Society (MRS) meetings.Technical description: The project is investigating the properties of semiconductor-transition metal oxide quantum interfaces at the monolayer scale. The challenge arises mostly because of the difficulty of epitaxial growth with the disparity of structural properties and lattice parameters. This challenge, however, has proven to be very much ideal for the progress made in layer-by-layer growth by molecular beam epitaxy, with in-situ characterization capability for atomic-scale scanning tunneling microscopy and spectroscopy, and piezoelectric force microscopy, and is the approach taken in this proposal. For example, the research team is growing monolayers of: GaAs (001), InGaAs (001) and GaAsP (001) on BaTiO3 (110) and BiFeO3 (110) grown on SrTiO3 (110), to produce transition metal-semiconductor quantum interfaces. For analysis, the team is using scanning tunneling and piezoelectric force microscopy for morphology and spectroscopy to provide real-time data, by providing interactive feedback, needed to understand the interface from single monolayers to 10-20 nm thicknesses. For the interface between dissimilar materials, the team is evaluating the effects of the local density of states, polarization screening, surface reconstruction, electric and magnetic field coupling, bonding between sp-electrons and d-electrons, fractional quantum Hall effect, localization of charge, and lattice match, mismatch and strain on the interface electronic and photonic properties. As a more high-risk exciting opportunity the team is using high quality semiconductor/transition metal oxide and transition metal oxide/semiconductor interfaces, to stack interfaces, to form a superlattice of quantum interfaces with novel properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.