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Solar array simulators (SAS) equipment is used to mimic the characteristics curve for photovoltaic (PV) generators. However, an in-depth stability analysis of the SAS with respect to its reference signal is yet to be investigated. This is due to implicit and nonlinear mapping equations used to describe the $I\text{--}V$ curve, which complicates the loop analysis. Our study proposes a super-elliptical method to approximate the $I\text{--}V$ characteristic curve and provide an explicit PV equation that is straightforward to manipulate. Furthermore, this approximate model is then used for the dynamic performance assessment for the typical control architecture. Based on the comparative study using the approximate mode either in the theoretical analysis and the experimental verification, the resistance-sensing control scheme tends to reduce the effect of loop interactions in the SAS, thereby showing more consistent dynamic performance than the other control structure. [ABSTRACT FROM AUTHOR]

In the back-end-of-line double-gate (DG) amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs), the linearity of top-gate voltage (${V}_{TG}$)-swept threshold voltage (${V}_{T,TG}$) with back-gate voltage (${V}_{BG}$) is essential. In this work, the influence of positive bias stress (PBS) condition on both $\beta = \partial {V}_{T,TG}/\partial {V}_{BG}$ and $\Delta \beta = \partial \Delta {V}_{T,TG}/\partial {V}_{BG}$ is investigated in DG a-IGZO TFTs, using the subgap density-of-states (DOS) extracted before and after PBS. While $\Delta \beta $ remains almost constant in the PBS condition of ${V}_{TG}/{V}_{BG}=30$ /-30 V, the ${V}_{TG}={V}_{BG}=30$ V condition shows the complicated nonlinear relationship between $\Delta {V}_{T,TG}$ and ${V}_{BG}$. It is found that $\lambda = \delta \Delta \beta /\delta {V}_{BG}$ , as the parametric indicator describing the PBS-induced degradation of linearity for the ${V}_{BG}$ -controlled ${V}_{T,TG}$ , is $\times 7$ larger (less linear) at ${V}_{TG}={V}_{BG}=30$ V than at ${V}_{TG}/{V}_{BG}=30$ /−30 V. The origin of this non-linearity is comprehensively explained based on the model of the excessive oxygen-related defect creation resulting from broken peroxy linkage. Our result suggests that the ${V}_{TG}/{V}_{BG}=30$ /−30 V is a more advantageous condition in the viewpoint of the $\Delta {V}_{T,TG}$ linear with ${V}_{BG}$ , in comparison with ${V}_{TG}={V}_{BG}=30$ V. [ABSTRACT FROM AUTHOR]

Threshold voltage shift ($\Delta {V}_{\text{T}}$) under various current stress (CS) conditions need to be quantitatively studied in self-aligned top-gate amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Here, we propose a stretched-exponential function (SEF)-based $\Delta {V}_{\text{T}}$ model that can be applied to various combinations of ${V}_{\text{GS}}$ and ${V}_{\text{DS}}$. The proposed model indicates the characteristic electron trapping time constant $\tau _{1}$ is inversely proportional to (${V}_{\text{GS}} - {V}_{\text{T}}$). In contrast, the time constant $\tau _{2}$ is directly proportional to the square root of (${V}_{\text{DS}}+{V}_{\text{bi}}$), presumably due to the local donor creation by a lateral electric field. The proposed model was verified experimentally in various ${V}_{\text{GS}}$ and ${V}_{\text{DS}}$ configurations. Further, it is confirmed that the lateral electric field dominantly influences donor creation near the drain. [ABSTRACT FROM AUTHOR]

Viscoelasticity of human tissue often carries important physiological information linking to many fatal diseases, such as heart failure, renal impairment, and liver failure. Fluid retention due to these diseases cause swelling of body parts (edema) and changes the viscoelastic characteristic of the tissue. We hypothesize that the viscoelastic behavior change of the tissue can be estimated by creating and quantifying the pit on the swelled body parts. Here, we present a smartphone tactile imaging probe with an indenter (STIP-I) system that measures the pitting parameters and characterizes the viscoelastic behavior. This system consists of tactile imaging sensing that utilizes a light diffusion in a polydimethylsiloxane (PDMS)-based optical waveguide and a Viscoelastic Pitting Recovery (VPR) computation model. The prototype STIP-I system is tested using edematous tissue phantoms, which show a moderate measurement error of 29.5% for the pitting parameters and excellent performance of 7.60% error in elastic modulus estimation. The STIP-I system is expected to bring a new approach to understanding viscoelasticity changes due to various diseases. [ABSTRACT FROM AUTHOR]

In this study, the oxygen flow rate (OFR) dependence of negative bias illumination stress (NBIS) and positive bias stress (PBS) in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices was investigated. Unlike in previous studies, our study simultaneously considered and analyzed the bias stress-induced degradation mechanisms by charge trapping and defect creation. NBIS and PBS instability were measured according to the OFR splits of bottom-gate (BG) IGZO TFTs and the behavior of full subgap range density of states (DOS) was experimentally tracked with especial emphasis on deep-level oxygen vacancy (${V}_{\text {O}}$) peak. It was found that the observed DOS variation was consistent with the ${V}_{\text {O}}$ ionization model during NBIS. In addition, the threshold voltage shift by charge trapping (${\Delta } {V}_{\text {T,CT}}$) and the threshold voltage shift by defect creation, i.e., change of DOS, (${\Delta } {V}_{\text {T,DOS}}$) were separated and extracted through the subthreshold slope decomposition method. After NBIS, the threshold voltage shift (${\Delta } {V}_{\text {T}}$) was composed of a component by charge trapping and a component with the ionization of ${V}_{\text {O}}$. After PBS, ${\Delta } {V}_{\text {T}}$ was dominated by a component arising due to charge trapping. Fitting through the stretched exponential function (SEF) was performed for each separately extracted ${\Delta } {V}_{\text {T}}$ , and the activation energy for each ${\Delta } {V}_{\text {T}}$ was extracted using the inverse Laplace transform method through the extracted ${\Delta } {V}_{\text {T0}}$ , $\tau $ , and $\beta $. Activation energy by charge trapping and DOS was extracted from NBIS and PBS, respectively. As a result of simultaneously considering the two degradation mechanisms, the extracted activation energy was located between the previous values. Experimentally extracted sets of DOS-specific parameters before and after bias stress were applied to technology computer-aided design (TCAD) simulations. Accurate reproduction of TFT current–voltage (${I}$ – ${V}$) curves before and after bias stress and recovery suggests that the methodology and parameter set used in this study are reasonable and potentially useful for a more robust and systematic analysis of the bias stress-induced instability in a-IGZO BG TFTs. [ABSTRACT FROM AUTHOR]

This study proposes a model of mobility and negative bias stress stability degradation mechanism of zinc oxynitride (ZnON) thin-film transistors (TFTs) with various anion compositions. The subgap density of states (DOS) for ZnON TFTs were extracted using monochromatic photonic capacitance–voltage measurement. The extracted subgap DOS indicated an additional nitrogen-related subgap peak was observed in ZnON TFTs with an excessive nitrogen condition, which might originate from a nitrogen divacancy formation. Furthermore, the shifted threshold voltage components after the bias stress test were quantitatively divided as subgap DOS and interface trapping. [ABSTRACT FROM AUTHOR]