자료유형  

 학위논문

Control Number  

0017164858

International Standard Book Number  

9798346389934

Dewey Decimal Classification Number  

621.381

Main Entry-Personal Name  

Paul, Tiffany.

Publication, Distribution, etc. (Imprint  

[S.l.] : Stanford University., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

114 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-05, Section: B.

General Note  

Advisor: Kapitulnik, Aharon.

Dissertation Note  

Thesis (Ph.D.)--Stanford University, 2024.

Summary, Etc.  

요약Standard differential torque magnetometry is a technique for measuring magnetic anisotropy by placing a sample on the end of a diving-board-like cantilever and tracking the cantilever's resonant frequency in magnetic field. We use radiation pressure to drive the cantilever across its resonant frequency, and we use optical interferometry to measure the cantilever's response to the drive. When the cantilever is placed in an external magnetic field, a magnetic dipole on the end of the cantilever interacts with the field, resulting in a differential torque on the cantilever. This can be measured as a change in the resonant frequency of the device. Of course, excellent signal to noise and high Q cantilevers are necessary for detecting small frequency shifts. But for measurements of quantum materials, particularly in reduced dimensions, there is also the need to electrically manipulate the sample on the cantilever. By fabricating cantilevers from scratch, we are able to pattern integrated circuits directly on the cantilever and tailor the dimensions of each device to maximize sensitivity for a given sample. We introduce two realizations of specialized cantilevers with electrically controlled samples: cantilevers with thin-film samples deposited in a Corbino disk geometry and miniaturized cantilevers patterned with gates for exfoliated samples.When I joined the Kapitulnik lab in 2017. I began working on a project in collaboration with the Amir Yacoby lab designed measure the Hall conductivity of poor conductors using cantilever torque magnetometry. To do this, we learned to integrate the multi-layer patterns needed to form a Corbino geometry with the cantilever fabrication process while maintaining a very high Q (25000). We used sputtered indium tin oxide (ITO) with resistivity 3.5 x 10 -3cm as the sample and measured the Hall conductivity of two devices to be (2.0±0.1) x10-7Ω -1 and (1.8±0.3)x10-7 Ω -1 respectively [67]. Converting to resistivities, this becomes pxy ~ Ω .10 or 5 x 10-7Ω cm in 3D. These results are the first measurements of Hall conductivity using torque magnetometry, and the small ratio of Pxy/Pxx and the ability to measure day ~ 10-8Ω-1demonstrate the effectiveness of our technique. We also used this technique to show unambiguous evidence of in-plane ferromagnetism and its effect on the transport properties of low carrier density ITO annealed through its MIT by simultaneously measuring the bulk magnetic and transport properties of a material [66].After completing these preliminary measurements, I began work on second generation gated flake devices in order to reduce the background magnetic field dependence, further improve our measurement sensitivity, and allow tuning of the carrier density of a gated sample by adding a separate ground lead in addition to the back gate and top gates. I characterized the second generation device's inherent response to magnetic field and gate voltage, showing the field dependence to be an order of magnitude smaller that that of the first generation devices due to improvements in the device fabrication.

Subject Added Entry-Topical Term  

Silicon wafers.

Subject Added Entry-Topical Term  

Photographs.

Subject Added Entry-Topical Term  

Electrons.

Subject Added Entry-Topical Term  

Graphene.

Subject Added Entry-Topical Term  

Magnetic fields.

Subject Added Entry-Topical Term  

Asymmetry.

Subject Added Entry-Topical Term  

Annealing.

Subject Added Entry-Topical Term  

Atomic physics.

Subject Added Entry-Topical Term  

Electromagnetics.

Added Entry-Corporate Name  

Stanford University.

Host Item Entry  

Dissertations Abstracts International. 86-05B.

Electronic Location and Access  

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Control Number  

joongbu:656196