A proposal to enhance project New Phase Change Materials for Photonics by installing chalcogen plasma gas sources for epitaxial thin film growth
Abstract
We propose to install plasma gas sources for epitaxial growth of sulfide and selenide thin films by molecular beam epitaxy (MBE). Cracking of hydride precursors H2S and H2Se is essential for growing high-quality chalcogenide films by gas-source MBE, at low and moderate substrate temperature, and plasma sources are the preferred means of gas cracking due to their efficient gas utilization and tunable conditions. These sources will be installed on an existing MBE chamber that was designed for the deposition of chalcogenide thin films and phase-change electronic materials.The proposed upgrades would directly benefit the work carried out under the project entitled New phase change materials for photonics: from in-silico design to novel device concepts, which is funded by the Office of Naval Research (ONR) under the Multidisciplinary University ResearchInitiative (MURI) program, award number N00014-17-1-2661. This is a collaboration focusing on chalcogenide phase-change materials (PCMs) for photonics. PCMs are increasingly important to critical communication and computation technologies. A major impediment to the widespread utilization of PCMs is the large power required for switching, which is due to the need ofconverting electrical or optical energy to heat. The fundamental reason for this limitation is that established phase-change materials are switched using time-temperature processing. Electronic and optical energy could be used more effectively if external stimuli were directly coupled to the relevant microscopic degrees of freedom in the materials.Our efforts focus on materials that are proximal to thermodynamic phase transitions, and for which an optical field can couple directly to the relevant structural distortion. Our preliminary work emphasizes opportunities in layered materials, including alloys of sulfide transition metal dichalcogenides, and tin selenide. Our theory results suggest that these materials may featureuseful phase-change functionality with ultra-fast, low-energy, non-thermal optical switching. Our experimental results to-date support our theory predictions, but also emphasize the need for cracker sources to produce high-quality films at wafer-scale and with low processing temperature. This will be possible with the proposed plasma cracker sources.The proposed upgrade will have impact well beyond the ongoing work on phase-change materials for photonics. Sulfide MBE is very rare, but not due to lack of interest; there are many families of sulfide semiconductors that are of tremendous for applications including photodetectors, photonics, microelectronics, and energy conversion. Sulfide MBE lags due largely to the difficulty of making sulfides in ultra-high vacuum, and the challenges to vacuum technology presented by solid-source sulfur crackers. The proposed capabilities, especially the capacity to make sulfide-selenide alloys by co-deposition from H2S and H2Se plasma sources, would represent a noteworthy advance, and could spur widespread interest and a revival of activity in chalcogenide gas-source MBE.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 31, 2020
- Source ID
- N000142012807
Entities
People
- Rafael Jaramillo
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy