Browsing by Author "Huang, Tsung-Lin"

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Feasibility of Ge double quantum dots with high symmetry and tunability in size and inter-dot spacing
(2019-01-01)
Peng, Kang-Ping
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Huang, Tsung-Lin
;
George, Thomas
;
Lin, Horng-Chih
;
Li, Pei-Wen
We report the tunability of the sizes and inter-dot spacings of Ge coupled quantum dots (QDs) using nano-spacer technology in combination with selective oxidation of Si0.85Ge0.15. Spherical-shaped Ge QDs were formed at each sidewall corner of the nano-patterned Si3N4 ridges by thermal oxidation of poly-SiGe spacer layers encapsulating the Si3N4 nano-ridges. The diameters of the Ge spherical QDs are essentially determined by geometrical height, width, and length of the nano-spacer islands of poly-SiGe, which are tunable by adjusting the process times of their deposition and etch back. The inter-dot spacing between the Ge DQDs are controllable by adjusting the widths of the lithographically-patterned Si3N4 ridges and the thermal oxidation times. Our self-organization and self-alignment approach achieved high symmetry within the Ge DQDs in terms of the individual QD sizes as well as the coupling barriers between the QDs and external electrodes in close proximity.
The Germanium "Halo": Visualizing Ge interstitial dynamics in nanocrystallite formation
(2018-10-01)
George, Thomas
;
Huang, Tsung-Lin
;
Hsueh, Chui-Yu
;
Peng, Kang-Ping
;
Lin, Horng-Chih
We report the ability to image distributions of Ge interstitials within amorphous SiO2 matrices using conventional transmission electron microscopy and energy dispersive X-ray spectroscopy mapping. While previous, established methods have only been able to indirectly infer the presence of interstitials within materials, our direct "visualization" approach allows the ability to study and better understand the dynamics of several interesting phenomena occurring within the Ge-Si-O system during processing at temperatures greater than 700 degrees C which has not been described in any previously published work. Experimental observations by TEM of the Ge interstitial dynamics has allowed us to clarify the various operating mechanisms for Ge nanocrystallite growth within these SiO2 matrices. These phenomena include Ostwald ripening, migration of Ge nanocrystallites through amorphous SiO2 and Si3N4 matrices, Ge incorporation in Si-rich materials such as Si3N4 and Si, and finally, morphological changes in the Ge nanocrystallites themselves. (c) 2018 The Japan Society of Applied Physics.
Tunable diameter and spacing of double Ge quantum dots using highly-controllable spacers and selective oxidation of SiGe
(2019-08-05)
Huang, Tsung-Lin
;
Peng, Kang-Ping
;
Chen, Ching-Lun
;
Lin, Horng-Chih
;
George, Tom
We report the novel tunability of the diameters and spacings of paired Ge double quantum dots (DQDs) using nano-spacer technology in combination with selective oxidation of Si0.85Ge0.15 at high temperature. Pairs of spherical-shaped Ge QDs were formed by the selective oxidation of poly-SiGe spacer islands at each sidewall corner of the nano-patterned Si3N4/poly-Si ridges. The diameters of the Ge spherical QDs are essentially determined by geometrical conditions (height, width, and length) of the nano-patterned spacer islands of poly-SiGe, which are tunable by adjusting the process times of deposition and etch back for poly-SiGe spacer layers in combination with the exposure dose of electron-beam lithography. Most importantly, the separations between the Ge DQDs are controllable by adjusting the widths of the poly-Si/Si3N4 ridges and the thermal oxidation times. Our self-organization and self-alignment approach achieved high symmetry within the Ge DQDs in terms of the individual QD diameters as well as the coupling barriers between the QDs and external electrodes in close proximity.