Kyungyul Ryu

Improvement in the performance of an InGaZnO thin-film transistor by controlling interface trap densities between the insulator and active layer

An amorphous InGaZnO film fabricated by radio frequency magnetron sputtering in only an Ar-reactive gas shows high conductivity, and a thin-film transistors (TFTs)-based IGZO active layer expresses a poor on/off current ratio with a high off current and high subthreshold swing (SS). This paper presents the post-annealing effects on IGZO thin films to compensate the oxygen deficiencies in films as well as on TFT devices to reduce the densities of the interface trap between the active layer and insulator. The ratio of oxygen vacancies over total of oxygen (O2/Otot) in IGZO estimated by the XPS measurement shows that they significantly diminish from 24.75 to 17.68% when increasing the temperature treatment to 350 °C, which is related to the enhancement in resistivity of IGZO. The TFT characteristics of IGZO treated in air at 350 °C show a high ION/IOFF ratio of ~1.1 × 107, a high field-effect mobility of 7.48 cm2 V−1 s−1, and a low SS of 0.41 V dec−1. The objective of this paper is to achieve a successful reduction in the interface trap density, ΔDit, which has been reduced about 3.1 × 1012 cm−2 eV−1 and 2.0 × 1012 cm−2 eV−1 for the 350 and 200 °C treatment samples compared with the as-deposited one. The resistivity of the IGZO films can be adjusted to the appropriate value that can be used for TFT applications by controlling the treatment temperature.

A novel method for crystalline silicon solar cells with low contact resistance and antireflection coating by an oxidized Mg layer

One of the key issues in the solar industry is lowering dopant concentration of emitter for high-efficiency crystalline solar cells. However, it is well known that a low surface concentration of dopants results in poor contact formation between the front Ag electrode and the n-layer of Si. In this paper, an evaporated Mg layer is used to reduce series resistance of c-Si solar cells. A layer of Mg metal is deposited on a lightly doped n-type Si emitter by evaporation. Ag electrode is screen printed to collect the generated electrons. Small work function difference between Mg and n-type silicon reduces the contact resistance. During a co-firing process, Mg is oxidized, and the oxidized layer serves as an antireflection layer. The measurement of an Ag/Mg/n-Si solar cell shows that Voc, Jsc, FF, and efficiency are 602 mV, 36.9 mA/cm2, 80.1%, and 17.75%, respectively. It can be applied to the manufacturing of low-cost, simple, and high-efficiency solar cells.

Desflurane reduces intraoperative remifentanil requirements more than sevoflurane: comparison using surgical pleth index-guided analgesia

Background: Sevoflurane and desflurane are widely used in balanced anaesthesia in combination with opioid analgesics. The opioid remifentanil is frequently chosen because of its extremely rapid pharmacokinetics. However, intraoperative high‐dose remifentanil is associated with increased postoperative pain and rescue analgesic use owing to acute tolerance and opioid‐induced hyperalgesia. This study aimed to compare intraoperative remifentanil requirements during equi‐minimum alveolar concentration (MAC) sevoflurane and desflurane anaesthesia via surgical pleth index‐guided remifentanil administration. Methods: Eighty‐two subjects undergoing laparoscopic cholecystectomy were randomly allocated to two groups receiving either sevoflurane (n=40) or desflurane (n=42). Anaesthesia was maintained with the assigned inhaled anaesthetics and remifentanil. End‐tidal anaesthetic concentration was maintained at age‐corrected 1.0 MAC, and remifentanil infusion was continuously adjusted to achieve a surgical pleth index of 20–50. Mean remifentanil infusion rate, which was the primary outcome of the study, was calculated as the total infused remifentanil dose per kg body weight per minute of total operative time. Results: Mean remifentanil infusion rate [mean (standard deviation)] was significantly higher in the sevoflurane group than in the desflurane group [0.192 (0.064) vs. 0.099 (0.033) &mgr;g kg−1 min−1; difference, 0.093 (95% confidence interval, 0.071–0.115); P<0.001]. Conclusions: During equi‐MAC anaesthesia of 1.0 MAC, sevoflurane and desflurane did not show similar intraoperative remifentanil consumption under surgical pleth index‐guided opioid administration. Further studies using other monitors with different measuring mechanisms are warranted to determine the cause of this difference. Clinical trial registration: NCT02830243 (ClinicalTrials.gov).

Analysis of Resistance and Surface Recombination Velocities by Contact Coverage for Optimizing Electrical Loss in c-Si Local Back Contact.

Recently, the importance of solar cell research has emerged due to emerging social issues such as environmental pollution problems and rising oil prices. Accordingly, each company is studying to make solar cell of high efficiency. In order to fabricate high-efficiency solar cells, the two major techniques have to be applied on the rear. One is complete passivation of the surface using a thermal oxide and the other one is the part that comes in contact with the electrode doped partially LBSF (Local BSF) formation. In this paper, LBC technology which is usually applied for high efficiency crystalline silicon solar cell, applied to mass productive solar cell to achieve high open circuit voltage and short circuit current with low surface recombination from rear side. Thermal SiO2/SiN(x) double layer which has superior thermal stability is formed on rear surface as passivation layer, then 1% of the whole rear surface area is locally contacted with aluminum. Finally, the cell has been fired at high temperature and the cell process has complete. The fabricated LBC cells conversion efficiency was 18.0% with 625 mV of open-circuit voltage (V(oc)), 37.58 mA/cm2 of current density (J(sc)), 76.3% of fillfactor (FF) at 5% contact coverage, respectively.