Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session C03: CMP + Materials 2: Imaging Techniques |
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Chair: Karine Chesnel, Brigham Young University Room: JFB 103 |
Friday, October 12, 2018 10:45AM - 11:09AM |
C03.00001: Imaging electronic states in van der Waals heterostructures Invited Speaker: Brian LeRoy The ability to create arbitrary stacking configurations of layered two-dimensional materials has opened the way to the creation of designer band structures. Twisted bilayer graphene and graphene on hexagonal boron nitride (hBN) are two of the simplest examples of such a van der Waals heterostructure where the electronic properties of the composite material can be fundamentally different from either individual material. These van der Waals heterostructures can be formed using a wide variety of layered materials including transition metal dichalcogenides, graphene and topological insulators. This talk will mostly focus on creating topologically protected states in graphene devices by breaking inversion symmetry. The lattice mismatch and twist angle between layers in the heterostructure produces a moiré pattern which affects its electronic properties. For graphene on hBN, the moiré pattern creates a new set of superlattice Dirac points. In small twist angle bilayer graphene, the combination of a long-wavelength moiré pattern and an electric field leads to the formation of an array of topologically protected states on the domain walls of the moiré pattern. In this talk, I will discuss our fabrication of these heterostructures and measurements using scanning probe microscopy. |
Friday, October 12, 2018 11:09AM - 11:21AM |
C03.00002: Dangling bond states at the diamond surface characterized by Dynamic Tunneling force microscopy Gongqi Yu, Clayton C Williams Recently the creation of atomic scale quantum states composed of dangling bonds (DBs) at the surface of hydrogenated Si (100) has been explored [1]. At room temperature, electrons in these DB states are trapped for sub-nanosecond times. At the bare reconstructed diamond surface C(100)-(2x1), some DB states have much larger trapping energies (~ 1 eV) [2]. Electrons can be trapped in these atomic sized states for long times (hours) at room temperature, providing a basis for creating atomic scale charge and spin quantum devices [3]. Dynamic Tunneling Force Microscopy (DTFM) is an effective method to characterize the spatial distribution and energy of such electron trap states [4,5]. DTFM measurements of DB states at the diamond surface will be presented and the properties of the DB states will be discussed. [1] J.L. Pitters, L.Livadaru, M.B. Haider & R.A. Wolkow, J. Chem. Phys. 134, 064712 (2011). [2] Z. Zhang, M. Wensell & J. Bernholc, Phys. Rev. B, 51, 5291 (1995). [3] L. Livadaru, J. Pitters, M. Taucer & R.A. Wolkow, Phys. Rev. B, 84, 205416 (2011). [4] R. Wang, S.W. King & C.C. Williams, Appl. Phys. Lett. 105, 052903 (2014). [5] R. Wang & C.C. Williams, Rev. Sci. Instr. 86, 093708 (2015).
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Friday, October 12, 2018 11:21AM - 11:33AM |
C03.00003: Magnetic Imaging of Multilayered [Co/Pt] Thin Films Aaron Gentillon I will present a study of the behavior of the magnetic domains of multilayered Cobalt/Platinum thin films. The goal of this project is to experimentally find a magnetic field value at which the number of domains per unit area is maximized. To complete this study, I used a Vibrating Sample Magnetometer to apply a magnetic field to the thin films, and then I used an Atomic/Magnetic Force Microscope to image the magnetic domains of a small area on the sample, usually about 10 x 10 micrometers. The images were then statistically analyzed, and the number of domains was counted and plotted as a function of magnetic field value. I've studied an ascending series of field values on samples with Cobalt layers that are 60 and 12 Angstroms thick. In both cases, a peak field value was observed. |
Friday, October 12, 2018 11:33AM - 11:45AM |
C03.00004: Imanging Magnetic Domian Morphologies of Cobalt/Platinum Multilayer Thin-films Carson Richards I am doing research under Dr. Chesnel at Brigham Young University. The research studies the magnetic domain morphologies of CoPt thin-films ranging from 55-335 nanometers in total thickness. In these CoPt multilayer thin-films, the thickness of the individual Co layers varies in the samples from 0.4 to 6 nanometers and the thickness of the individual Pt layer is 0.7 nanometers, these two layers repeat 50 times. I will present results for samples with a Co thickness of 2.5 and 3.1 nanometers. We used a Vibrating Sample Magnetometer (VSM) to apply a strong magnetic field looping sequence to the samples before returning to net-zero magnetization. We then used an Atomic Force Microscope (AFM) to map the magnetic domain morphologies. We repeated this process, of alternatively using the VSM and AFM to complete various types of sequences. The densities of the magnetic domains of the individually and previously applied loops in each state were analyzed. I am looking for the relationship between the magnitude of the previously applied magnetic field and the density of the magnetic domains in three different types of series. I will present a comparison between the ascending series, the descending series, and the pumping series. |
Friday, October 12, 2018 11:45AM - 11:57AM |
C03.00005: Volumetric nanoscale strain visualization using Bragg x-ray coherent diffraction imaging Elijah Schold, Edwin Fohtung Nanoscopic strain engineering is an innovative pathway which holds great potential in functional device application [memory, photactive materials, sensors, diodes, etc.]. Therefore: volumetric imaging of strain at the nanoscale is important for understanding and designing these devices. In my presentation I will overview Bragg X-ray Coherent Diffractive Imaging (BCDI) of topological defects in ferroelectrics and ferroelectric devices in operando. Through this, the audience will be introduced to how BCDI can act as a liaison between theory, design, and application of the next generation of electronic devices. |
Friday, October 12, 2018 11:57AM - 12:09PM |
C03.00006: Determine of Attachment Strength of Carbon Nanotube-Carbon Composite Neural Probe Array Bryce Eric Hedelius Current neural probes have mechanical properties that are very different from neural tissue. After insertion, the probes continue to cause damage due to micromotion. As an alternative, carbon nanotube-carbon composite structures have tunable mechanical properties and therefore would cause less damage. Carbon nanotubes were grown into dense forests on a substrate patterned with an array of catalytic iron spots, then infiltrated with carbon to create high-aspect ratio posts. To measure the attachment strength, the posts are pushed with a platinum wire, increasing the applied force until the post detached. The failure modes of flexure, tensile, and compression (buckling) are measured. The measured attachment strengths range from 131 to 667 MPa. |
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