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We investigate the Ni–Si film silicidation process on 4H-SiC and Si substrates and compare the thermal stability of the films grown on each substrate. The Ni–Si films were subjected to rapid thermal annealing (RTA) in the temperature range 575 °C–975 °C for 90 s, and their thermal stability was characterized by in-situ temperature-dependent sheet resistance measurements at temperatures of 25 °C–550 °C. The sheet resistance of a 40 nm thick Ni film was observed to increase sharply above 330 °C in the Ni/Si (100) interface, but slightly decrease at approximately 480 °C in the Ni/4H-SiC interface. The thermal stability of the films was found to be significantly dependent on the RTA temperature. Thermally stable Ni–Si silicide films with excellent Ohmic properties (no hysteresis behavior) can be obtained on 4H-SiC substrates at RTA temperatures of 925 °C–975 °C and can used for application in MOSFET devices.

Herein, the fabrication of a novel highly sensitive and fast hydrogen (H2) gas sensor, based on the Ta2O5 Schottky diode, is described. First, Ta2O5 thin films are deposited on silicon carbide (SiC) and silicon (Si) substrates via a radio frequency (RF) sputtering method. Then, Pd and Ni are respectively deposited on the front and back of the device. The deposited Pd serves as a H2 catalyst, while the Ni functions as an Ohmic contact. The devices are then tested under various concentrations of H2 gas at operating temperatures of 300, 500, and 700 °C. The results indicate that the Pd/Ta2O5 Schottky diode on the SiC substrate exhibits larger concentration and temperature sensitivities than those of the device based on the Si substrate. In addition, the optimum operating temperature of the Pd/Ta2O5 Schottky diode for use in H2 sensing is shown to be about 300 °C. At this optimum temperature, the dynamic responses of the sensors towards various concentrations of H2 gas are then examined under a constant bias current of 1 mA. The results indicate a fast rise time of 7.1 s, and a decay of 18 s, for the sensor based on the SiC substrate.

The surface passivation of a CMOS image sensor (CIS) is highly beneficial for the overall improvement of a device performance. We employed the thermal atomic layer deposition (T-ALD) and plasma enhanced (PE-ALD) techniques for the deposition of 20 nm HfO2 as well as stacked with 3 and 5 nm Al2O3 thin films. The HfO2/Si and Al2O3/HfO2/Si metal-oxide-semiconductor structures were used to analyze the fixed charge density (Qf) and interface trap density (Dit). The as-synthesized samples show high Dit and Qf values (10 12 cm -2 eV -1 ) and a minority carrier lifetime of 15-300 µs. The finite-difference time-domain simulation of high-k dielectrics confirmed that the Al2O3 (top)/HfO2 stacked structures expected higher quantum efficiency for CIS application. The effect of vacuum annealing (VA) and forming gas annealing (FGA) treatments succeeded with the decomposition of the Dit and increase in carrier lifetime. The H2 ambient FGA samples showed a remarkable decrease in the Dit values. To improve the overall performance of the device after passivation, we employed an Al2O3/HfO2 bilayer structure, which showed a low Dit of 10 11 cm -2 eV -1 and a minority carrier lifetime of ~3,700 µs after 400 °C and 30 min FGA. We believe that this surface passivation strategy will pave way for future CIS technology regarding the development of lower defective surface and superior performance.

Reduced graphene oxide (RGO)-coated microballs of poly (methyl methacrylate) (PMMA) used for fabricating three-dimensional sensor (3D sensor), which are expected to exhibit high sensitivity compared with conventional two-dimensional (2D) sensors, were prepared using a reaction-based assembly process. The sheet resistance and transmittance of the RGO-coated balls decreased with increasing number of coatings, implying that the RGO was well adhered to the ball by the assembly method. Two types of vacuum pressure sensors using multiple balls and a single ball were fabricated using lift-off and air-blowing methods, respectively. At pressures <1 torr, the sensors showed an increased resistance value due to the bending of graphene sheets by the Van der Waals attractive force. Further, the pressure versus resistance values at the logarithmic scale showed a linear relation, with a pressure reading error <6%. Compared with the 2D sensor fabricated using RGO, the multiball sensor exhibited almost 4–5 times higher RRC value. The single-ball sensor showed reasonable reproducibility at various temperatures. Given the size and pressure reading range of the sensor, the sensitivity of the single-ball sensor at 100 °C was approximately 6,000 times greater than that of the sensor with the highest sensitivity reported in the literature. The increase in surface area and the geometric effect of the sensing part of the single-ball sensor appeared to be responsible for its abnormally high sensitivity.