Presentation Title

Fabrication and Characterization of High Entropy Chalcogenide: A Potential Spin Hall Material

Presenter Information

Brandi WootenFollow

Faculty Mentor

Dr. John Heron

Start Date

18-11-2017 11:15 AM

End Date

18-11-2017 11:30 AM

Location

9-247

Session

Engineering/CS 3

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

High Entropy Alloys (HEA) have gained significant attention over the last decade because they exhibit advantageous properties that their elements individually may not demonstrate. HEAs usually consist of five or more metals in equal proportions and are materials of high configurational entropy. For example, Germanium Tin Lead Sulfur Selenium Telluride (GeSnPbSSeTe) is a high entropy chalcogenide (HEC). This HEC contains heavy elements and is proposed to present a stronger spin orbit coupling, which would induce a strong spin Hall angle and will be a good candidate for a spin Hall material. To adequately test the HEC, HEC thin films with optimal roughness and structural properties are needed. A flat thin film is required for maximal contact, essential for most devices, while a crystalline structure is preferred to maximize the spin Hall effect as it is a cumulative effect dependent upon local structural orientation. Using pulsed laser deposition, we deposited several HEC films at various substrate temperatures and chamber pressures. We then characterized the roughness of the films using atomic force microscopy and the structure using x-ray diffraction. We observed that, as the growth temperature was increased, the roughness of the film increased in an exponential fashion. Concurrently, the film exhibited a crystalline structure only at higher temperatures and was more pronounced at lower pressures. These observations are essential for the next steps of fabricating devices using the HEC thin films to measure the material’s spin Hall angle.

Sinova, J.; Valenzuela, S.; Wunderlich, J.; Back, C.; Jungwirth, T. Spin Hall Effects. Reviews of Modern Physics 2015, 87.

Yeh, J.; Tsai, M. High-Entropy Alloys: A Critical Review. Materials Research Letters 2014, 2, 107–123.

Summary of research results to be presented

I fabricated high entropy chalcogenides (HEC) using pulsed laser deposition (PLD). PLD involves sending a high power laser pulse into a chamber and striking a target with a known composition. The material will vaporize and deposit onto the substrate. With every laser pulse, the material on the substrate 'grows', allowing for a way to construct flat thin films with desired qualities. While using this technique to fabricate thin films, one can change several parameters such as temperature, pressure, geometry of the system, and frequency and strength of the laser pulses. During my project, I varied temperature and pressure to optimize the thin film's roughness and crystalline structure. I characterized the thin films using atomic force microscopy and x-ray diffraction. Ultimately, I found the optimal growth conditions to fabricate thin films with our desired properties. These characteristics are essential to measure the material's spin Hall angle.

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Nov 18th, 11:15 AM Nov 18th, 11:30 AM

Fabrication and Characterization of High Entropy Chalcogenide: A Potential Spin Hall Material

9-247

High Entropy Alloys (HEA) have gained significant attention over the last decade because they exhibit advantageous properties that their elements individually may not demonstrate. HEAs usually consist of five or more metals in equal proportions and are materials of high configurational entropy. For example, Germanium Tin Lead Sulfur Selenium Telluride (GeSnPbSSeTe) is a high entropy chalcogenide (HEC). This HEC contains heavy elements and is proposed to present a stronger spin orbit coupling, which would induce a strong spin Hall angle and will be a good candidate for a spin Hall material. To adequately test the HEC, HEC thin films with optimal roughness and structural properties are needed. A flat thin film is required for maximal contact, essential for most devices, while a crystalline structure is preferred to maximize the spin Hall effect as it is a cumulative effect dependent upon local structural orientation. Using pulsed laser deposition, we deposited several HEC films at various substrate temperatures and chamber pressures. We then characterized the roughness of the films using atomic force microscopy and the structure using x-ray diffraction. We observed that, as the growth temperature was increased, the roughness of the film increased in an exponential fashion. Concurrently, the film exhibited a crystalline structure only at higher temperatures and was more pronounced at lower pressures. These observations are essential for the next steps of fabricating devices using the HEC thin films to measure the material’s spin Hall angle.

Sinova, J.; Valenzuela, S.; Wunderlich, J.; Back, C.; Jungwirth, T. Spin Hall Effects. Reviews of Modern Physics 2015, 87.

Yeh, J.; Tsai, M. High-Entropy Alloys: A Critical Review. Materials Research Letters 2014, 2, 107–123.