N-Channel MOSFET Reliability Issue Induced by Visible/Near-Infrared Photons in Image Sensors.

Image sensors such as single-photon avalanched diode (SPAD) arrays typically adopt in-pixel quenching and readout circuits, and the under-illumination first-stage readout circuits often employs high-threshold input/output (I/O) or thick-oxide metal-oxide-semiconductor field-effect transistors (MOSFETs). We have observed reliability issues with high-threshold n-channel MOSFETs when they are exposed to strong visible light. The specific stress conditions have been applied to observe the drain current (Id) variations as a function of gate voltage. The experimental results indicate that photo-induced hot electrons generate interface trap states, leading to Id degradation including increased off-state current (Ioff) and decreased on-state current (Ion). The increased Ioff further activates parasitic bipolar junction transistors (BJT). This reliability issue can be avoided by forming an inversion layer in the channel under appropriate bias conditions or by reducing the incident photon energy.

Effects of Lower Limb Cycling Training on Different Components of Force and Fatigue in Individuals With Parkinson's Disease.

The strength of lower extremity is important for individuals to maintain balance and ambulation functions. The previous studies showed that individuals with Parkinson's disease suffered from fatigue and strength loss of central origin. The purpose of this study was to investigate the effect of lower extremities' cycling training on different components of force and fatigue in individuals with Parkinson's disease. Twenty-four individuals (13 males, 11 females, mean age: 60.58 ± 8.21 years) diagnosed with idiopathic Parkinson's disease were randomized into training and control groups. The maximum voluntary contraction (MVC) force, voluntary activation level (VA), and twitch force of knee extensors were measured using a custom-made system with surface electrical stimulation. The general, central, and peripheral fatigue indexes (GFI, CFI, and PFI) were calculated after a fatiguing cycling protocol. Subjects received 8 weeks of low resistance cycling training (training group) or self-stretching (control group) programs. Results showed that MVC, VA, and twitch force improved (p < 0.05) only in the training group. Compared to the baseline, central fatigue significantly improved in the training group, whereas peripheral fatigue showed no significant difference in two groups. The cycling training was beneficial for individuals with Parkinson's disease not only in muscle strengthening but also in central fatigue alleviation. Further in-depth investigation is required to confirm the effect of training and its mechanism on central fatigue.

Voltage modulation efficiency in scanning capacitance microscopy.

This paper reports a novel investigation of the voltage modulation efficiency (VME) in scanning capacitance microscopy (SCM). A signal intensity model was used to define the VME, which is dependent on the impedance components in an SCM setup. In SCM, the VME was found to play a key mediating role in the close relationship between the signal intensity and the modulation voltage, providing an indicator for the surface treatment and the back-contact process of an SCM specimen. We observed that, for silicon-based specimens, ultraviolet-assisted oxidation and microwave annealing improved the specimen surface and the back-contact, respectively, which increased the VME. It was also found that a high modulation voltage and a large back-contact area may induce a significant stray capacitance around the conductive tip and, hence, lower the VME. The VME degradation not only decreased the SCM signal intensity but also reduced the image contrast in the regions with high carrier concentrations. In addition, our experimental results further revealed that the signal intensity model also provided a promising opportunity to establish a precise and quantitative method for measuring the thickness of insulating layers.