Hybrid nanomechanical systems including atom-scale defects based on silicon carbide (NEMSiC)

提出的项目探索基于碳化硅（SiC）的混合纳米机械系统。特别是，我们将重点关注原子尺度缺陷与纳米力学自由度的耦合。这些缺陷与金刚石中众所周知的nv中心相似。然而，由于大量的碳化硅多型，可能的缺陷种类要多得多。我们的建议特别针对自旋3/2缺陷。与金刚石中众所周知的自旋1缺陷不同，自旋3/2缺陷可以在光学上检测，而无需额外应用微波场。在项目过程中，我们研究了由两种不同的SiC多型加工的纳米机械谐振器：一方面，我们将研究在不同掺杂的SiC衬底上生长的六边形4H-SiC。4H-SiC的优异之处在于其极高的晶体质量，这使得缺陷中心的自旋相干性很大。然而，涉及到谐振器的制造，并且期望在1,000-10,000范围内的中等机械质量因素。另一方面，我们将使用立方的3C-SiC。这种材料在强拉伸应力下生长在（111）硅片上。这削弱了自旋相干性，但由于大的拉伸应力，使机械质量系数达到10万。我们将描述由这两种互补多型制造的纳米机械谐振器的振动特性。特别强调的是主要的耗散机制（以及普遍的拉应力，对于3C-SiC的情况）。通过可控的聚焦离子束辐照产生缺陷中心，并探索其自旋相干性。该项目的目标是实现一种混合纳米机械系统，其中自旋状态可以被机械地操纵或读出。这将通过光学检测自旋-机械共振实验建立。总之，我们建议建立碳化硅作为混合自旋-纳米机械系统的替代材料，它比流行的单晶金刚石更容易加工。此外，我们将阐明这种新材料的潜在优势。对4H-SiC和3C-SiC的比较将进一步表明，长自旋相干性和高机械质量因子之间的权衡如何有利于混合纳米机械系统。

The proposed project explores hybrid nanomechanical systems based on silicon carbide (SiC). In particular, we will focus on the coupling of atomic-scale defects to the nanomechanical degree of freedom. These defects bear resemblance to the well-known NV-centers in diamond. However, the variety of possible defects is much higher as a result of the large number of polytypes of SiC. Our proposal specifically targets spin 3/2 defect. Unlike the well-known spin 1 defects in diamond, the spin 3/2 defects can be optically detected without additional application of microwave fields. In the course of the project, we investigate nanomechanical resonators processed from two different SiC polytypes: On the one hand side, we will investigate hexagonal 4H-SiC grown on differently doped SiC substrates. 4H-SiC excels in its extremely high crystal quality, which results in a large spin coherence of the defect centers. However, the fabrication of resonators is involved, and moderate mechanical quality factors in the range of 1,000-10,000 are to be expected. On the other hand side, we will employ cubic 3C-SiC. This material is grown on (111) silicon wafers under strong tensile stress. This impairs the spin coherence, but enables large mechanical quality factors of several 100,000 as a result of the large tensile stress.We will characterize the vibrational properties of nanomechanical resonators fabricated from both, complementary polytypes. Particular emphasis will be on the dominating dissipation mechanisms (as well as the prevailing tensile stress, for the case of 3C-SiC). Even more, the defect centers will be generated by focused ion beam irradiation in controllable manner and their spin coherence will be explored. The goal of the project is the realization of a hybrid nanomechanical system, in which the spin state can be manipulated or read out mechanically. This will be established experimentally via optically detected spin-mechanical resonance. AIl in all, we propose to establish silicon carbide as an alternative material for hybrid spin-nanomechanical systems, which is easier to process than the prevalent single-crystal diamond. In addition, we will shed light on the potential advantages which arise from this new choice of material. The comparison between 4H-SiC and 3C-SiC will further show how the tradeoff between long spin coherence and high mechanical quality factor can be advantageously leveraged for hybrid nanomechanical systems.