A special chip for direct and real-time observation of resistive changes, including set and reset processes based on Au/ZnO/Au system inside a transmission electron microscope (TEM), was designed. A clear conducting bridge associated with the migration of Au nanoparticles (NPs) inside a defective ZnO film from anode to cathode could be clearly observed by taking a series of TEM images, enabling a dynamic observation of switching behaviors. A discontinuous region (broken region) nearby the cathode after reset process was observed, which limits the flow of current, thus a high resistance state, while it will be reconnected to switch the device from high to low resistance states through the migration of Au NPs after set process. Interestingly, the formed morphology of the conducting bridge, which is different from the typical formation of a conducting bridge, was observed. The difference can be attributed to the different diffusivities of cations transported inside the dielectric layer, thereby significantly influencing the morphology of the conducting path. The current TEM technique is quite unique and informative, which can be used to elucidate the dynamic processes in other devices in the future.

A novel carbon-enclosed chemical vapor deposition (CE-CVD) to grow high quality monolayer graphene on Cu substrate at a low temperature of 500 °C was demonstrated. The quality of the grown graphene was investigated by Raman spectra, and the detailed growth mechanism of high quality graphene by the CE-CVD process was investigated in detail. In addition to growth of high quality monolayer graphene, a transparent hybrid few-layer graphene/CuNi mesh electrode directly synthesized by the CE-CVD process on a conventional glass substrate at the temperature of 500 °C was demonstrated, showing excellent electrical properties (∼5 Ω/□ @ 93.5% transparency) and ready to be used for optical applications without further transfer process. The few-layer graphene/CuNi mesh electrode shows no electrical degradation even after 2 h annealing in pure oxygen at an elevated temperature of ∼300 °C. Furthermore, the few-layer graphene/CuNi mesh electrode delivers an excellent corrosion resistance in highly corrosive solutions such as electroplating process and achieves a good nucleation rate for the deposited film. Findings suggest that the low temperature few-layer graphene/CuNi mesh electrode synthesized by the CE-CVD process is an excellent candidate to replace indium tin oxide (ITO) as transparent conductive material (TCM) in the next generation.

Chemical vapour deposition of graphene was the preferred way to synthesize graphene for multiple applications. However, several problems related to transfer processes, such as wrinkles, cleanness and scratches, have limited its application at the industrial scale. Intense research was triggered into developing alternative synthesis methods to directly deposit graphene on insulators at low cost with high uniformity and large area. In this work, we demonstrate a new concept to directly achieve growth of graphene on non-metal substrates. By exposing an amorphous carbon (a-C) film in Cu gaseous molecules after annealing at 850 °C, the carbon (a-C) film surprisingly undergoes a noticeable transformation to crystalline graphene. Furthermore, the thickness of graphene could be controlled, depending on the thickness of the pre-deposited a-C film. The transformation mechanism was investigated and explained in detail. This approach enables development of a one-step process to fabricate electrical devices made of all carbon material, highlighting the uniqueness of the novel approach for developing graphene electronic devices. Interestingly, the carbon electrodes made directly on the graphene layer by our approach offer a good ohmic contact compared with the Schottky barriers usually observed on graphene devices using metals as electrodes.

The use of costly and rare metals such as indium and gallium in Cu(In,Ga)Se2 (CIGS) based solar cells has motivated research into the use of Cu2ZnSnS4 (CZTS) as a suitable replacement due to its non-toxicity, abundance of compositional elements and excellent optical properties (1.5 eV direct band gap and absorption coefficient of ~104 cm−1). In this study, we demonstrate a one-step pulsed hybrid electrodeposition method (PHED), which combines electrophoretic and electroplating deposition to deposit uniform CZTS thin-films. Through careful analysis and optimization, we are able to demonstrate CZTS solar cells with the VOC, JSC, FF and η of 350 mV, 3.90 mA/cm2, 0.43 and 0.59%, respectively.

Background Recent studies have reported promising outcomes of non-operative treatment for uncomplicated appendicitis; however, the preoperative prediction of complicated appendicitis is challenging. We developed models by incorporating fat stranding (FS), which is commonly observed in perforated appendicitis. Material and methods We reviewed the data of 402 consecutive patients with confirmed acute appendicitis from our prospective registry. Multivariate logistic regression was performed to select clinical and radiographic factors predicting complicated acute appendicitis in our model 1 (involving backward elimination) and model 2 (involving stepwise selection). We compared c statistics among scoring systems developed by Bröker et al. (in J Surg Res 176(1):79–83. https://doi.org/10.1016/j.jss.2011.09.049, 2012), Imaoka et al. (in World J Emerg Surg 11(1):1–5, 2016), Khan et al. (in Cureus. https://doi.org/1010.7759/cureus.4765, 2019), Kim et al. (in Ann Coloproctol 31(5):192, 2015), Kang et al. (in Medicine 98(23): e15768, 2019), Atema et al. (in Br J Surg 102(8):979–990. https://doi.org/10.1002/bjs.9835, 2015), Avanesov et al. (in Eur Radiol 28(9):3601–3610, 2018), and Kim et al. (in Abdom Radiol 46:1–12, 2020). Finally, we examined our models by performing the integrated discrimination improvement (IDI) test. Results Among enrolled patients, 64 (15.9%) had complicated acute appendicitis. We developed new 10-point scoring models by including the following variables: C-reactive protein, neutrophil to lymphocyte ratio, and computed tomography features of FS, ascites, and appendicolith. A cutoff score of ≥ 6 exhibited a high sensitivity of 82.8% and a specificity of 82.8% for model 1 and 81.3% and 82.3% for model 2, respectively, with c statistics of 0.878 (model 1) and 0.879 (model 2). Compared with the model developed by Bröker et al. which included C-reactive protein and the abdominal pain duration (c statistic: 0.778), the models developed by Atema et al. (c statistic: 0.826, IDI: 5.92%, P = 0.0248), H.Y Kim et al. (c statistics: 0.838, IDI: 13.82%, P = 0.0248), and our two models (IDI: 18.29%, P < 0.0001) demonstrated a significantly higher diagnostic accuracy. Conclusion Our models and the scoring systems developed by Atema et al. and Kim et al. were validated to have a high diagnostic accuracy; moreover, our models included the lowest number of variables.