Browsing by Author "Yang, Kuo-Ching"

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A Unique Approach to Generate Self-Aligned SiO2/Ge/SiO2/SiGe Gate-Stacking Heterostructures in a Single Fabrication Step
(2015-05-19)
Lai, Wei-Ting
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Yang, Kuo-Ching
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Hsu, Ting-Chia
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Liao, Po-Hsiang
;
George, Thomas
We report a first-of-its-kind, unique approach for generating a self-aligned, gate-stacking heterostructure of Ge quantum dot (QD)/SiO2/SiGe shell on Si in a single fabrication step. The 4-nm-thick SiO2 layer between the Ge QD and SiGe shell fabricated during the single-step process is the result of an exquisitely controlled dynamic balance between the fluxes of oxygen and silicon interstitials. The high-quality interface properties of our "designer" heterostructure are evidenced by the low interface trap density of as low as 2-4 x 10(11) cm(-2) eV(-1) and superior transfer characteristics measured for Ge-based metal-oxide-semiconductor field-effect transistors (MOSFETs). Thanks to the very thin interfacial SiO2 layer, carrier storage within the Ge QDs with good memory endurance was established under relatively low-voltage programming/erasing conditions. We hope that our unique self-aligned, gate-stacking heterostructure provides an effective approach for the production of next-generation, high-performance Ge gate/SiO2/SiGe channel MOSFETs.
Gate-stack engineering for self-aligned Ge-gate/SiO2/SiGe-channel Insta-MOS devices
(2015)
Lai, Wei-Ting
;
Yang, Kuo-Ching
;
Liao, Po-Hsiang
;
George, Thomas
;
Li, Pei-Wen
We reported a first-of-its-kind, self-aligned gate-stack heterostructure of Ge-nanoshpere-gate/SiO2/SiGechannel on Si in a single-step approach through selective oxidation of a SiGe nano-patterned pillar over a Si3N4 buffer layer on Si substrate. Good tunability on the Ge-nanoshpere size, SiO2 thickness, and SiGe-shell thickness provides a practically-achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices with size-tunable Ge gates, SiO2 gate oxide, and SiGe channels. Detailed interfacial morphologies and structural properties between the Ge nanosphere/SiO2 and SiO2/SiGe-channel were examined using transmission electron microscopy, energy dispersive x-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Both Al/SiO2/Genanospheres and NiGe/SiO2/SiGe MOS capacitors exhibit quite low interface trap densities of 3-5x10(11) cm(-2)eV(-1), which is beneficial for advanced Ge MOS applications.
Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors
(2016-02-11)
Lai, Wei-Ting
;
Yang, Kuo-Ching
;
Liao, Po-Hsiang
;
George, Tom
;
Li, Pei-Wen
We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe-nanopatterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5-90 nm), the SiO2 thickness (3-4 nm), and the SiGe-shell thickness (2-15 nm) have been demonstrated, enabling a practically achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive X-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5 x 10(11) cm(-2) eV(-1) and fixed charge densities of 1-5 x 10(11) cm(-2), suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1-xGex shell (x > 0.5) in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge) MOS nanoelectronic and nanophotonic applications.
Negative correlation of cortical thickness with the severity and duration of abdominal pain in Asian women with irritable bowel syndrome
(2017-08-31)
Chua, Chian Sem
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Bai, Chyi-Huey
;
Shiao, Chen-Yu
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Hsu, Chien-Yeh
;
Cheng, Chiao-Wen
Background & aims: Irritable bowel syndrome (IBS) manifests as chronic abdominal pain. One pathophysiological theory states that the brain-gut axis is responsible for pain control in the intestine. Although several studies have discussed the structural changes in the brain of IBS patients, most of these studies have been conducted in Western populations. Different cultures and sexes experience different pain sensations and have different pain responses. Accordingly, we aimed to identify the specific changes in the cortical thickness of Asian women with IBS and to compare these data to those of non-Asian women with IBS. Methods: Thirty Asian female IBS patients (IBS group) and 39 healthy individuals (control group) were included in this study. Brain structural magnetic resonance imaging was performed. We used FreeSurfer to analyze the differences in the cortical thickness and their correlations with patient characteristics. Results: The left cuneus, left rostral middle frontal cortex, left supramarginal cortex, right caudal anterior cingulate cortex, and bilateral insula exhibited cortical thinning in the IBS group compared with those in the controls. Furthermore, the brain cortical thickness correlated negatively the severity as well as duration of abdominal pain. Conclusions: Some of our findings differ from those of Western studies. In our study, all of the significant brain regions in the IBS group exhibited cortical thinning compared with those in the controls. The differences in cortical thickness between the IBS patients and controls may provide useful information to facilitate regulating abdominal pain in IBS patients. These findings offer insights into the association of different cultures and sexes with differences in cortical thinning in patients with IBS.