Nonequilibrium plasma aerotaxy of size controlled GaN nanocrystals

2020-02-01
Üner, Necip Berker
Thimsen, Elijah
High quality gallium nitride (GaN) nanocrystals (NCs) are promising materials in a wide range of applications including optoelectronics, photonics and biomedical devices. Unlike II-VI semiconductors, the synthesis of free-standing GaN NCs is not well-established, and there is a need for a synthesis platform that can provide GaN NCs with tunable size and photonic properties. In this work, we present a flexible gas-phase synthesis method that can deliver crystalline, free-standing, pure GaN NCs with controlled size and narrow size distributions. The method, termed nonequilibrium plasma aerotaxy (NPA), employs an aerosol of Ga and gaseous N-2 as the precursors. The term aerotaxy means growth on an unsupported surface, in this case promoted by a nonequilibrium plasma. The key to narrow size distributions is that the NPA mechanism is based upon surface growth, as opposed to coagulation mechanisms that result in broad size distributions. The NPA process converts the Ga aerosol into GaN NCs within 10-100 ms of residence time. The mechanism involves non-thermal vaporization of the source Ga aerosol, which is followed by nucleation and reaction with the excited N-2 species in the plasma. Particles can be made to be either hollow or solid. Solid NCs were found to be photoluminescent. Large NCs emitted photons at a peak wavelength near the bulk band-gap transition. Tuning the size to be smaller than 7 nm average diameter led to a blue-shifted photoluminescence. Inline processing of these bare GaN NCs into porous films by supersonic impact deposition is demonstrated. Moving beyond the specific example of GaN, the NPA mechanism is general and can be extended to many other binary, ternary or doped semiconductors.
JOURNAL OF PHYSICS D-APPLIED PHYSICS

Suggestions

Phase mixing in GaSb nanocrystals synthesized by nonequilibrium plasma aerotaxy
Üner, Necip Berker; Thimsen, Elijah (2020-05-01)
III-V semiconductor nanocrystals are an important class of optoelectronic materials. However, the gas-phase synthesis of these materials, especially of the stibnides, has been left relatively unexplored. In this study, we demonstrate the synthesis of free-standing GaSb nanocrystals for the first time, using a novel gas-phase process. We show that when elemental aerosols are used as precursors for Ga and Sb, the elements mix at the nanometer length scale as the aerosols pass through a nonequilibrium plasma r...
Ductile–brittle failure of amorphous glassy polymers: A phase-field approach
Dal, Hüsnü; Gültekin, Osman; BAŞDEMİR, SELÇUK; Açan, Alp Kağan (2022-11-01)
© 2022 Elsevier B.V.Optimal use and design of amorphous glassy polymers in goods have become a significant task in the key industrial sectors ranging from micro-electronics to aerospace and medical industry. Depending on the microstructure, temperature level and the external loading rate to which these polymers are subjected, the fracture response may change from ductile to brittle or vice versa. While the ductile response is manifested by diffuse shear zones exhibiting volume-preserving inelastic deformati...
Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends
Caydamli, Yavuz; Yıldırım, Erol; Shen, Jialong; Fang, Xiaomeng; Pasquinelli, Melissa A.; Spontak, Richard J.; Tonelli, Alan E. (2017-12-14)
Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants ...
Thermal effects of gate connected field-plates and surface passivation on AlGaN/GaN HEMTs
Kara, Doğacan; Okutucu Özyurt, Hanife Tuba; Dönmezer, Nazlı; Department of Mechanical Engineering (2018)
AlGaN/GaN high electron mobility transistors (HEMTs) are widely preferred in automotive, space, and military applications due to their superior electrical and thermal properties. However, when operated in full capacity, their electrical reliability drops significantly due to electron collapse, device degradation, concentrated heating, and mechanical stresses. To increase the reliability and maximum performance of GaN HEMTs, field-plate and surface passivation technologies are used frequently. Although signi...
Colloidal CdSe Quantum Wells with Graded Shell Composition for Low-Threshold Amplified Spontaneous Emission and Highly Efficient Electroluminescence
Keleştemur, Yusuf; Anni, Marco; Yakunin, Sergii; De Giorgi, Maria Luisa; Kovalenko, Maksym V. (2019-12-01)
Semiconductor nanoplatelets (NPLs) have emerged as a very promising class of colloidal nanocrystals for light-emitting devices owing to their quantum-well-like electronic and optical characteristics. However, their lower photoluminescence quantum yield (PLQY) and limited stability have hampered the realization of their outstanding luminescent properties in device applications. Here, to address these deficiencies, we present a two-step synthetic approach that enables the synthesis of core/shell NPLs with pre...
Citation Formats
N. B. Üner and E. Thimsen, “Nonequilibrium plasma aerotaxy of size controlled GaN nanocrystals,” JOURNAL OF PHYSICS D-APPLIED PHYSICS, vol. 53, no. 9, pp. 0–0, 2020, Accessed: 00, 2022. [Online]. Available: https://hdl.handle.net/11511/97119.